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Recovering couch patato
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Discussion Starter · #1 · (Edited)
I've been riding, reading and thinking on bikes for about 15 years now. Owned well more than a bike a year over that time, and loved most of them for one reason or another.

Hanging on these forums for a couple thousand posts have helped me built an insight in bikes that's more in-depth than at first I thought possible, yet I realize that other will always know more. Mostly because they care about bikes even more than I do. Some of them post on MTBR, some are keeping all they know to themselves. Others, like Sheldon Brown, worked all their lives just trying to share their knowledge with the generations yet to come.

I've been ranting quite a bit on various topics, most in some way connected to the prime topic of this forum : 29" wheels.

I thought I'd just try an list the things I feel strongly about, and which have not find their way into mainstream thinking yet, to blame mostly by the resistance to change within cycling that is greater than within any conservative party anywhere around the world.

Most topics are related to bikes as used for XC racing, as that's been my thing for many years.

  • Handlebars
  • Tire width
  • Bike weight in general
  • Wheel weight and its importance
  • Chainstay length
  • Gearing, range and steps or lack thereof
  • Crank length
  • Sensible geometry, choices made for the right reasons
  • Quick/snappy/agile/lively/responsive handling vs. lap times

If I omit a topic I've been ranting on here that you remember, feel free to remind me.

I'll try and get more into the above, below.
 

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Recovering couch patato
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Discussion Starter · #2 ·
Handlebars
Somewhere in the 70's or 80's someone hip intoduced a long straight handlebar and labeled it as made for what we now call mountainbiking.
Before, road bikes had been equipped with the curvy things they essentially still have, in parts due to regulations. 0 degree and 90 degree swept parts.
The straight bar got the 0 degree part only, or perhaps 3 or 5. For wrist relief, bar ends were introduced, which helps when alterated prequently.
Comfort and City bikes always had bars that swept back, usually between 20 and 80 degrees. Good for hours of riding enjoyment. But it cramped up the cockpit, so it was a no-no for MTB's.
It has to take til the 21st century for a Brit to invest a couple grand on a bending mold that gives a swept bar some forward sweet nea he stem, to fit well for riders still on a striahgt handlebar, without need for a longer stem. Haro named a bike after that handlebar, Mary. 19th century commons sense in riding comfort only introduced in the 21st century, that's bike engineering for you. That's how important the business thinks it is that your bike will be feeling good to you. Or, how little faith it has that proper designs are going to be honored with paying customers.
With a sweep roughtl betwen 0 and 90 degrees, the wrists are at ease, and there's much less need to relieve them with alternative hand positions. Control and power transfer can be just fine, when choosing the correct width. That first Mary was about the same effective width as a stereotype straight XC riser bar, with barends.

The ideal amount of back sweep is of course dependant on individual shoulder, elbow, wrist configuration. But also on seat-grip reach, effective handlebar width (distance between centre of palms), and relative bar height.
In most cases, a rider will appreciate that an 11d bar feels nicer than a 5d one. 17d feel nicer too, and around the 40d mark lies the optimum, for a large part of the cycling population.
The more swep on a bar, the more important tilt gets to find the ideal fit. Imagine the broomstick bars, you can tilt that and it doesn't matter at all. But take a bullhorn bar, and see if you can ride it on the horns at all when tilted just a few degrees off the ideal setting. Your body tells you how the tilt a bar, but t can take a few tries to interpret the signals right.

Some riders, especially over the past decade, have been cuting their broomstick down. From typically 56-58cm to as short as <50cm (been there, done that).
For weight (mere grams to be won on an average of 100,000g total of bike+ rider + gear), for speed (more aero?), but intuatively perhaps also because of ideal sweep vs. width. Hold an imaginy bar (grip a pen in each hand), and vary width, reach and height, while keeping wrist natural. You'll notice that a narrow bar "prefers" less back sweep. Even negative backsweep as you get narrower than your shoulder width!
So, were straight bars too wide, or swept inadequately? Try out-of-saddle climbing with a cut down straight bar first, and then with a wide swept bar, and let me know.
In case of the Jones H-bars, there's aero horns for the duller trails and road sections too. Perhaps not something that's never been done, but forgotten about altogether till he brought them for sure! Why does it take an acknowledged bike genious to construct a logical and effective handlebar? We have dozens of multi-million $ companies claiming to make the ultimate handlebars, ust for our kind of riding. Yet, our wrists hurt, and have been for 30 years of riding fat tires offroad.
Oddly, those first mountainbikes, arguably being raced down "Repack" Mountain or somewhere else on the globe ca. 1976, often had big swept bars, but I only have that from pictures as I wasn't there.

The past decade or so, bike manufacturers seem to add a degree of handlebar sweep every couple of years. Many bikes are now at 9d, which Fisher is (very much in character) ahead of most, with 12d. At this rate, when will the ~40d Mary bar become commonplace? Or will we never get there, and collectively switch to hurting our wrists on road drops again, by the time we'd be warming up for 18d?
The best though-through handlebars for XC in my opinion, are not on the market right now, Bikes On Snow's FloWing, the announced version with a little rise, or better : drop. The basic idea is shared with the Mary, but taken to dimensions that should work out better for more riders.

For commuting, by lack of a true MTB bar like that, I prefer trekking bars with sweep and a correcting long stem. I get the width to control the bike and jerk on it to get up to speed. I get length and reach near the stem, for comfort at speed, almost triathlon style.
A road bar, even not those with big flare, have nothing on that for hasted riding.
 

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Recovering couch patato
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Discussion Starter · #5 ·
Tire width
Popular misconceptions:
* Narrower tires roll faster, per definition.
* Losing weight on the tire will make you faster, because of the weight

Scientifi research conducted in Germany by technical market leader Schwalbe has proven that wider tires actually roll with less resistance. I'll advise their .com to read the ins and outs on that. This is for surfaces when do not drastically deform due to the tire passing over it.
In mud for instance, a narrow tire releases itself easier from the mud. Per meter terrain covered, less mud is trying to suck the tire back in. Supposing a firmer base at a few meters below the surface, a wider tire will sink about as deep, thus deform more mud. Deforming mud takes effort, and brings little back. Trampolines give back nearly all the efort put into deforming them. Only really wide tires manage to avoid sinking into the mud, to the point where the total amount of erenrgy required to ride a given speed is reduced as width is increased. This doesn't mak a super wide tire the final solution for mud riding though.

In sand, we'll gree a 23mm road tire is bad. 20mm if possible even worse. A 29x2.25" Bontrager XR though, floats over, in full control. Even more so for the 26x3.7 Surly Endomorpth which shares about the same outer tire diameter.
Recently, the only pro's ridin 29" in XC have been among the very few even considering sized-down 29" XC tires (to 1.75-1.8"). They race them for the weight savings. While a 29" rim makes any tire style better riding than an otherwise identical 26" one, it seems counter-logical to me to use a narow tire when in 26" you don't.
A 29x1.8 tire will surely handle an XC course really well, but keep the width around 2.0-2.4", and you've got all the same performance, then boosted some, at only the cost of 30-100g a tire. That's up to 0.1% of total weight. Something to be upset about for sure.
Been there to, done that too. I raced 1.7" Ritcheys and Specializeds on my FS in the late 90's. Flatted a lot, washed out a lot, but thoroughly enjoying the finer traits of havin light and narrow tires. During that period, ironically, there was not one wet race where I could use them close to their specific and limited potential.
I'm lusting for even wider tires than the 2.4 Schwalbes, even if they'll only fit my forks, not my frames. The improvement of the 2.35" Fast Fred over the 2.0 was just astronomical. A different tire altogether, and should not have shared the same name. Something like a 2.6" Fast Fred, but built to 2008 Schwalbe Evolution spec, that's be something. And well worth the 70og they'd weigh.

1 or 2 years from now, the pro's will have lightweight 2.0-2.4x29" tires availble to them, regardless of tire sponsor, and use of 1.8's will be restricted to wet races.

Me, I don't have a tire sponsor, so I ride the fattest and most high-tech tires that will fit, and my money can buy : Schwalbe's in 2.25" and 2.4".
 

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Just give me hardpack
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Questions

Maybe time to ask some of my questions to the points you always raise - I'm not sure I've seen these addressed adequately and wonder how you think about these:

1. Does tyre weight and hence overall weight not have an effect on climbing time? And as most time in a race is spent on uphills the trade off of narrow, but lighter tyres in rolling resistance is worth it on a hilly course. Hence the pro's obsession with weight?

2. Does air resistance not come into the equation on flat trails? In other words what is the trade off with bigger tyres in air resistance and does the rolling resistance benefits exceed the disadvantage of increased air resistance?

3. The handle bar story to me always also seemed to relate to air resitance. Flat narrow bars reduce effective frontal surface area of the rider. (low tuck, shoulders in). Sure, they are not as comfortable, but are they faster?

It is true that the bikes one buy often look like pro racing bikes (that's always the case in sport) and these might not suit, but that's what sells. There has been quite a shift of late though to 'comfier' bikes and racing bikes?
 

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Recovering couch patato
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Discussion Starter · #9 ·
Bike weight in general
People love to obess over some perameter in their bike, over which they have control, and can belief it greatly affects performance. What easier and better to obsess over than weight?
Most women do it, openly, about their own body weight. Men all the same, although maybe to a lesser agree. But we have bikes, and we wrench on them. We don't buy high heels, and we don't accessorize, (I don't, no really I don't), but we can upgrade our bikes feel in control, and on the way up.

In my racing carreer, I've resorted to 2x9 to save 30g of weight. I've limited my gear range by swapping to 12-27 road cassettes, and then customizing to 11-27 for anoher 3 grams. Alu lockrings, bolts, cassettes even.
(remind me to add a topic of gearing will ya?)
I've cut down handlebars, sat on planks, stripped foam off seat decks, shortened my seatpost (funny, if you've seen me on a bike), shaved down tire knobs, used condoms for innertubes, left off protecting valve caps, left off CO2 in important races with podium chances, rigid alu forks on gnarly to me courses, lower spoke counts, I've done it all.

Never has it made me a fast rider. When the light bikes worked, they felt light. However, the world did not flash by me at fast forward pace. People were overtaking me just like they idn't realize the perfection I was riding. On hills, no less! On box stock bikes!

How much weight can we really save off a bike?
Let's buy a racable bike for $1800 or so, a Fisher Paragon. 11.5kg, a rough guess?
I can throw, say, $1500 at it, and it will be ~9.5kg, and rigid, before I start stripping gears.
2kg...
me=90kg
bike=10kg
total : 100kg.
"2 per cent of performance gain, right? Tel me I'll complete a race 2% faster, daddy?"
I'm afraid not, son.
Some 50% of your effort goes into air drag, and you've not changed that.
Then, you spend a good time coasting your bike, a light bike could be slower there.
And in turns, weight doesn't help you much. At times stability from well-balanced weight is what gets you around the corner faster.
Perhaps you'll be faster by .5 per cent, on the right course.
"But that's only 45 second in typical races!"
Sorry to bring it to you son, but I think you should know the truth.

In my most recent racing "career", I've been placing well in races where I brough a heavy POS singlespeed bike, all the same as my sub-9kg 1x9spd miracle Cube prototype racer.
The only thing these bikes shared, was that I mounted them up with my best and preferred tires for the conditions at hand. Of yeah, and Dimension cork/foam closed end grips. I'm a sucker for those.

The performance potential to be found in obsessing over bike weight (I hope to zoom in on wheel weight obsession later) is minute compared to choosing your race day break fast and its timing right. Let alone specific training and rest to get around a lap faster, or the week, month, year, or life preceeding it.
If you're ranked 50th out of 150 in your local racing series, the number 45 will beat you on an identical bike fitted with 2kg worth of lead. Think of that when consider your next bike part upgrade, and try to "weigh" the importance of weight vs. esthetics, burliness, function and especially: price.
Yeah, I still obsess about light parts to some degree. Can't help it. A rehabbed junkie will always feel special about the idea of scoring just one more time.
I don't preach that heavier bikes are faster (although at selected times, they are), but realize that when you're pulling your wallet to buy a light bike part, it's really only because the industry wants you to feel it's okay to spend so much on a bike.
A <$500 SS 29"er can get around a race track surprisingly well. #40 may well beat you when aboard it. To go faster, pick your tires right, use the appropriate pressure, live healtily and buy your lady nice flowers. So she'll let your go out and ride more.

I've got a race this weekend, and I'm awefully out of shape. About 7kg of it, I think. I can fool myself into believing I need a weighless bike, or I can look toward the next race, and think how I get phisically ready for that, in case I'll have to resort to my heavy SS bike when my miracle race bike gets a mechanical...

Summarizing :
Bike is to be felt very easily. We zoom in on the 100% "feel" line, and 0.5% is more than obvious a difference. One way it can take away our belief to ever reach the finish, the other way it can make us feel like bike gods. Yeah, till the legs give in, and every bike will feel lead-filled.
You may enjoy a light bike for its relative feel, but don't call it "fast", just based on weight alone. Get your tire wrong for tomorrow's mud race, and you're in problems. Your bike may end up heavier than mine, as the tires threw less of the trail onto the bike and me. And that's just the smallest of things to fear.
 

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Recovering couch patato
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Discussion Starter · #11 · (Edited)
NoMud said:
Maybe time to ask some of my questions to the points you always raise - I'm not sure I've seen these addressed adequately and wonder how you think about these:

1. Does tyre weight and hence overall weight not have an effect on climbing time? And as most time in a race is spent on uphills the trade off of narrow, but lighter tyres in rolling resistance is worth it on a hilly course. Hence the pro's obsession with weight?

2. Does air resistance not come into the equation on flat trails? In other words what is the trade off with bigger tyres in air resistance and does the rolling resistance benefits exceed the disadvantage of increased air resistance?

3. The handle bar story to me always also seemed to relate to air resitance. Flat narrow bars reduce effective frontal surface area of the rider. (low tuck, shoulders in). Sure, they are not as comfortable, but are they faster?

It is true that the bikes one buy often look like pro racing bikes (that's always the case in sport) and these might not suit, but that's what sells. There has been quite a shift of late though to 'comfier' bikes and racing bikes?
1.
Sure it does. But for less than the pecentile it cuts off total weight, as air resistance is still there, though minute. So save 1kg off my setup, and I'll climb <1% faster, no matter how steep the trail. I can even think of situations where a heavier bike would aid (Steep) climbing.
A Mavic test day on an Alp shockingly seemed to tell researchers that heavier road wheels result in faster climbin times. Cause is expected to have to do with the dead point of the pedal stroke, and the momentum carried through it. Rotational weight might have a leveling effect on speed through a pedal cycle.
I'd love to ride a 10kg bike up an Alp, where all the weight is concentrated in the rims, to compare it to a heavy bike fitted with ultra light wheels, but the same tires.

2.
Sure it does. To which extent, is what the question is.
My daily commutes, year after year, have been completed on 21mm tubulars, 23mm road tires, 35mm road clicks, 2.0 and 2.35" MTB slicks, in both 26" and 29".
Level asphalt, no wind, 25kph is the point where I can positively tell the 29x2.35" and swept (deep position) trekking bar fitted bike is harder to push forward, compared to the 23mm typical road race bike setup. Cruising speed, say 33kph, I cannot really tell which bike is faster. Throw in any type of bend in the road, traffic to deal with, awkward diagonal road crossings, train tracks, and the fattie just makes up heaps of time.
One way to tell the effects of weigh and air drag between 2 tires, would be to roll down an average surface flat fire road, having adjusted the bike computer carefully for each tire, and stop pedaling at a typical riding speed, say 25kph. Which-ever setup rolls further is also likely to be fastest around a lap, for weight and air drag at least. Cornering is kept out of this equasion. Differences between any setup are minute this way, but repeated testing (and riders doin it) will eventually give interesting data. My shorter and heavier riding buddy out-rolls me all the time. We use this 2m50 tall dune. Roll down it from standstill, through some typical singletrack turns, and back to standstill down a fire road. Good way to tell which tire is fast, especially with corners thrown into the mix that way. By lack of a computer, we used the hill as the objective motor.

3.
Can tested the same way as in 2. I suppose. It does leave out fatique from the equasion, but when use coast along some turns, you may even incorperate cornering precision and efficiency.
Low average speed courses, for the part that is pedaled, will not give too much advantage to aero arm positions (back angle to be considered fixed). And the super-wide H-bars, rolling down a smooth hill, do offer that super aero tuck which seems to bring an edge. At least my brain tells me too. Easy enough to test too. Roll down a long straifght hill with different hand positions. Max speed, meters coasted, or rolled up back the next hill might tell you something.

For me, wide bars are about transferring power, doing it quickly, and using muscles for it I don't use for general propelling. Wide bars are great when oming out of a tight hairpin and facing a steep hill without any room to build up speed for it. Try it with your hands closer in or wider out. This is why singlespeeders like wide handlebars. On the flats, you'll see them spinning their legs, and their hands near the stem, elbows bent.

(4)
Yes, shop floor bike look like race bikes, and race bikes look like shop floor bikes. Somehow, that's how the cycling industry thinks it works. Problem, those less into image and more into pure pleasure (women are strong that way) are turned off bike awkwardly feeling bikes. Women will know they don't like a thing, but not set out to solve it and make it better. Men, just ride the darn uncomfortable thing, and will tell all of the internet how much they like it, and other should get one just like it.
To some degree, enforced comfort might well improve hour+ race performance of pro racers. More people would be into cycling if road bieks didn't rattle your teeth out as much, and handlebars would be like a personalized race car seat rather than a torturing device you need to grab on to, to not fall into an miles deep vulcano.
 

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Just give me hardpack
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Devil's advocate again:

I think everybody knows that 'fitness trumps weight' even for Sauser and Absolon, but are just in denial about it. And playing with bike bits is fun.

BUT (again, I'm talking racing here) - has anyone ever measured the psychological benefit and 'thinking' you have a fast, light bike? Or even 'knowing' you have the lightest bike out there? ;)
 

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Discussion Starter · #13 ·
Wheel weight and its importance
Once upon a time there was a rider who was contemplating the laws of physics, in relation to gyroscopic forced, and the energy storing capacity of a bicycle wheel.
His findings or beliefs we'll never know. But all his son remembered from it, was something having to do with accelleration, and that a heavier wheel makes it harder.
The son had friends, and they had friends.
Soon we all knew, the main thing holding use on the starting line is the weight in our wheels, especially that neaer to the outside. As that was it. Never did the cycling knowlege base send out a memo to describe in detail the forces at play, and the time penalty to be expected from a superfluous weight unit in the outside of the wheel.

That didn't matter much though, because our legs are meter-long sensors. They detect everything holding its revolutions back. We KNOW: wheel weight is an enimy, and it needs to be neutralized.

Some things to consider, and some parameters to work from:
Rims are 500g each
Tires are 650g each
Tubes are 200g each
Spokes are closer to the centre, but let's use 150g per wheel.
Around 1.5kg of rotating weight per wheel, on a typical shop floor 29"er. That translates into 1.35kg for an otherwise equal 26".

3kg per bike, or 3% of the total I'm dragging around a lap.
An engineer on MTBR once calculated for us that during hard acceleration, our wheels "weigh" up to twice as much. "Wow, so without whels we'd be twice as fast, right?". No, we'd accelerate up to 6% faster without wheels, or zero weight wheels.
"Ah, but wheels turn all the time, that's accelerating, right? Especially uphill?"
No, accelating is the time spent with the bike computer showing ever increasing speeds.

Yes, wheel weight affects 0-20mph time. But even the most anal weight weenie will have a hard time losing 20% off those shop floor wheels, or 1.2% of actual performance increase.

That's why I ten to get to the first corner first, be it on my super light race bike, or my overbuil singlespeed. The weight thing is not a real factor. The time I take to clip into my pedals is, and whether I got any sleep the night before. Most of all, it comes down to how strong you are, relative to total bike+rider weight.

And dont think that when you exit a corner at 15mph, before working your way back up to 20mph, that 6% will be present. At higher speeds, acceleration is less acute, and thus less of a multiplier on your wheel weight. At 20mph, roughly half your effort goes toward creating a mild breeze right along the trail you just passed. Only the other half left to accelerate that 100kg. This is why cars go from 0-60mph in like 8 seconds, but take another 20 or more to reach 120mph. You'll tell that on the highway, when you floor it, the push back into you seat isn't quite there like when you leave the traffic lights.

Anyway, while simple cycling minds love to obsess over wheel weiht, as it's an easy thing to understand the importance of, a nicely defined factor of performace, it's really not all it's cracked up to be.

Especially when standing on the pedals, macho style swerving the front wheel left and right while you propel the bike up to speed, you'll be able the FEEL the weight of your wheels. It's unmistakably there. That's because it's effectively like you're holding a self-propelled wheel in each hand which are spinning themself up to speed while into a violet twist, just when you're trying to concentrate on your ballet steps.

A wheel spinning at 20mph quite something to handle. But, when the wheel is hel firmly, you can get it there with the flick of just one arm. Stopping it is a matter of a quick grip.
No huge power sucker there, the a wheel storing up to it's own weight in energy.

All too often forgotten is that what goes in, will come out. You accelerate off the line. But as you approach the first corner, or roll up the first hill, the energy stored in the wheel (proportionate to speed, mind you) is giving you back exactly what you put into it. If accelerating a heavier wheel asks for a bit more wrist power when it's in the wheel stand, consider that weight difference a friendly tap on the bum as you attack that first steep hill. Give, and take.
If your riding style is to kill kinetic energy only by grabbing a handful of braks, energy stored in the wheels will not do you much good. The braks will win. But when you learn how to use the energy stored inside ouf you, your bikes, and the tiny bonus in those wheels, you´ll be lapping noticably easier.
When I´m on my heavy wheeled bike, I stop pedaling sooner before a turn, saving energy slightly longer, only to be forced to accelerate longer before reaching preferred velocity. Give, and take.

Then, there´s the cornering effect of wheel weight. We all know it´s harder to move a wheel that spins than a statis one. Hold a wheel by the QR´s. let someone spin it, and you´ll be able to tell.
So, it takes more steering input to change the wheels´ direction. Does that slow down the cornering, or kill momentum. My conclusion has been that at worst, I´m working my bi~triceps a bit more, but never enough to notice. It a heavier wheel I´ve turning. Test yourself: bike on rear wheel, steer that fork with the front wheel spinning. That´s how tired steering really is, and any difference tires you. A non/issue.
If anything, heavier wheels seemed to help me keep more momentum through turns. Be it from the shear energy transfer from the wheel to trail, or the gyroscopic stabilty helping me to take a more fluent, more efficient line.

Don´t mistake the above as me saying heavier wheels are faster all the time. No, I think the powers at work are misunderstood, and exaggerated. What the AAA brands of the bike industry will lead you to believe.

Funny, how we are brought up to understand combustion engines and computers, but magic of a wheel makes our heads spin more than the wheels themselves.
 

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Discussion Starter · #14 ·
NoMud said:
I think everybody knows that 'fitness trumps weight' even for Sauser and Absolon, but are just in denial about it. And playing with bike bits is fun.

BUT (again, I'm talking racing here) - has anyone ever measured the psychological benefit and 'thinking' you have a fast, light bike? Or even 'knowing' you have the lightest bike out there? ;)
It would be interesting to hypnotize a consistently performing pro racer before a race, telling him his bike feels really heavy today, and everything seems to take much more effort than usually. I bet it would en in a DNF, and a bike thrown in a ditch.

Mental belief is everything in bike racing, and we are letting it be that. Although perhaps some of us feel muzed by the underdog position. I had that in my first/ever race on a SS, among gearies of my own level I raced against almost weekly. For me it worked, I hardly underperformed despite the huge discomfort and shockingly new experience. Not sure it would work that way for your typical Olympian, finding himself on the starting line without any gear shifters, and big, heavy wheels to boot.
 

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Discussion Starter · #15 ·
Chainstay length
Shorter is typically consider better, for everyhing. Tight turning, climbing, and curing cancer.

Yet, 99% of all 26" hardtails come with 425/430mm chainstays. A range so tight, it´s almost hard for manufacturers to not be off a couple mm either way. Yeah, I know, welding rigs...

Anyway, 425mm isn´t all that short. With some effort, 26" bikes could get 410mm, should the designer really care. But they don´t care, they just fear to differ in any way, as they honestly don´t know what´s best, or what customers will accept when going over the geometry spec in the catalogue. All the way the customer to do is read "425mm, check!". Like there´s one perfect length for chainstays, male of female, 4´of 7´, climber of DH´er.

While the 29" wheel adds 31.5mm in radius, your typical hardtail will read 445mm, only 20mm more than 26". Why is that? 29" designers care, because they expect riders to still look for that 425mm figure. So, they go for what´s reasonably doable in terms of clearance, and spec that. Early Fishers were 439mm even, making some tires nearly rub the thick seat tube. Surly KM´s are 431mm I think, a bend in the seat tube was made to make way for the rear wheel. The 2.8kg frame cannot be falsely expected to feel cumbersomely stable...

My Redline Monocog got 438mm chainstays with teh rear wheel forward in the horizontal dropouts. One day I brought a piece of extra chain and powerlink on a ride, plus the required 15mm wrench. I swapped chainstay length to 464mm and back, to try and appreciate the difference. The long setup had some interesting traits. Less bumpy on the azz over bumps, and more fluent through fast corners. Quite possibly due to more even weigh distribution with my super/tall, thus aft seat position.
I however could not complete any sort of wheelie though, where with shorter chainstays I could. This of course also means that had it been a geared bike, I could have climbed much steeper hills without the need to get out of the seat to prevent tumbling back over.

Although we all share the same trails, we are all different riders.
Should the trail dictate chainstay length, if a factor at all, or rider height?
If proportionate to rider height, chainstays be longer by about an inch for every 2" frame size increment. In reality, there´s less than an inch between the longest and shortest on the market, regardless of size. That´s how much manufacturers focus on NOT being different. And we´re promoting that behaviour.

Truth be told, the otherwise extremely conservative Santos bikes in Europe, now offers marathon/specific 26" hardtails with longer chainstays.

Many riders forget to realize how really long the chainstays even on their 26" FS bikes are, and how they still laude their tight/turn handling.

Chainstay length: misunderstood and importance exaggerated. Especially for 29" bikes which have plenty of traction anyway, and can be rolled through corners faster.
 

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Nice ramblings, but it strikes me how much of this comes down to your own personal experience and feel. The Schwalbe conclusion about tire width and pressure is valid, though. Some magazines have come to the same conclusion, being wide tires with low presssure are faster, once the ground gets bumpier or softer.

On the wheel weight bit: "An engineer on MTBR once said", come on, you can do better than that!

Here are the tools: http://www.analyticcycling.com/WheelsCritCorner_Page.html

This model simulates an acceleration out of a corner. Equalize the aerodynamic properties of both setups, enter weight and rotational enertia of light 26" wheels and heavy 29" wheels and presto: The difference between 2 riders after a set distance out of a corner.

Why have I not yet done this myself?... Anyone capable of calculating enertia? :madman:
 

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Discussion Starter · #17 ·
JeroenK said:
Why have I not yet done this myself?... Anyone capable of calculating enertia? :madman:
Thanks for that link Jeroen, and you guessed right: I never could remember any formula´s, hence me sitting here largely uneducated in the usual meaning of the word.

I´ll touch some on rolling resistance as I under stand it.

Very black and white, there´s hard and soft surfaces, and hard and soft tires.
Rolling resistance is the sum of the deforming tire, and the deforming trail.
Soft tires deform more, so there´s more resistance coming from that.
A soft trail deforms more from a hard tire than from a soft one. Due to the minimal rebound of most soft surfaces, it´s profitable to reduce tire pressure.

On a rock hard, totally even surface, high pressures are worth it. Look at track bikes, rolling at 200psi or so?
Offroad, that rarely happens I think, some give from the tire will usually bring improved roll.
 

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Discussion Starter · #18 ·
Gearing, range and steps or lack thereof
In mainstream cycling, we have 9 and 10spd cassettes, Campagnolo introducing 11 now.
Cogs usually starting at 11 or 12, and running up to 21 or perhaps 28 for road bikes, and 32 to 34 for mountainbikes.
It´s true that road bikes on average are pedaled within a narrow speed band. Say, 10 to 30mph (factor 3).
Mountainbikes need to operate between 4mph and 25mph (factor 5). No wonder that they come almost without exception with triple chainrings (22/32/44 for factor 2) and 11/34 cassettes (factor 3). Roadbikes traditionally stick to 39/53 and 12/23. Prolonged hills on even the smoothest Alps are thereby still a matter of struggling oneself up. Many roadbikes now come with triple cranks,a s riders have overcome their shame for that.

Gaps
The flatter road cassete of course has on average smaller steps between the cogs, Especially the 10 and 11spd ones. One tooth up per cog. This allows for very presize shifting, which can be really nice when looking to find that magical pedaling rythm (cadance) down a long, straight climbs, or open flat headwind hunted countryroad. It can reduce fatigue when one has the gear selection to fine tune cadance.

Offroad, a road cassette does the same. I for years used 12/27 and 11/27 9spd cassettes for this very reason. However, with the more frequent speed changes of offroading, you´ll be shifting through more cogs than with the typical MTB cassette. With the years, I found myself shifting more while going slower. To the point I became a freakshow of machine gun shifting, it drove my fellow racers mad (loud gripschift click). My legs had lost their flexibility, and only operated well inside a narow cadance range. Meaning I had to shift 3 times to go from 15mph to, say, 21mph.
So, 11/34 is much better, fewer shifts, more pedaling. We use our leg´s born ability to change pace. After all, we get from standstill just fine, right?
But do we even need the 9 gears to bridge ±200% of gear gain? Some experiments, and my first singlespeed experiences, have lead me to believe that larger gaps are better for efficient off road racing. For my legs, the sweet spot is around ±25%, like 16/20/25 steps. On smaller cogs, smaller gaps, that works out just nicely.

With larger gaps on a cassette, fewer chairings are required, many a rider might ditch their front derailer. Cassettes could also be narrower, leaving more room for the spokes which in turn brings a lateraly stiffer rear wheel.

We´re not likely going to see any changes in cog sizes on MTB casettes. They´ll probably fine a way to jam in a 10th cog in that 11/32 though, and call it development. I won´t go into drivetrain efficiency, mud shedding and that sort of thing, others know that much better than I.

I once went to 29/40t chainrings on my 29"er as the gearing felt too tall coming off 26" wheels. NOt talking about the granny gear, no all gears felt too tall. So, it was betwen the ears really. For some reason the mind is able to tell how fast the chain is moving or something.
I was still using the 12/27t at the time. Many are trying he same now. IMO it´s nonsense unless you are running an 11/34 cassette or better with it. Forget the argument of the weight savings from going to smaller chainrings. Jeroen will probably have a link to a site which plots drivetrain efficiency against weight, explaining my point.

I´d like to see 6spd 11/34 or 7spd 11/38 cassettes for trails that have many speeds changes, but within a speed range. I bet you´ll like it too. It would be like almost/singlespeed. Or see it like geared riding with on a shift per train section. Singlespeeds can be way quick over trails that don´t have you pedal at a fixed speed for too long on end. Why would a multi/speed cassette not work out even better?
 

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Cloxxki: A wheel spinning at 20mph quite something to handle. But, when the wheel is held firmly, you can get it there with the flick of just one arm. Stopping it is a matter of a quick grip. No huge power sucker there, the a wheel storing up to it's own weight in energy.

Once and for all you have to drop this argument. Spinning a wheel from the rubber is the equivalent of having a 200-300T cog. Try spinning up (or stopping) a big heavy wheel from the hub area (with a 16T cog) and you will understand why the problem is not weight, but the distance of the weight from the center of rotation. So it makes sense that any racer will always look for light rubber/rim combo, to gain that advantage (regardless of wheel size).

Common Cloxxki, you are an intelligent person, yet you never seem to acknowledge this.
 

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Discussion Starter · #20 ·
Crank length
99% of adults in the Western world are, what? 1m50 through 1m95 tall?
Yet, the cycling industry determined decades ago, for all of mankind, for decades to come, the one and only correct cranklength bound to win all Olympics, and teach even kid to ride a bike. The first century bikes, with extensive crank length studies, all universally pointing to one magical size: 175mm
Most all studies have shown that cranks best be a given percentage of leg length, broken up in femur length, foot length, etc. In the end, it comes down to being over 20% of inseam. Only really short riders manage that. But, short riders do win big races.
When a tall rider switches to longer cranks (they exist, but scarcely), usually it takes times for the muscles to adjust. Up months of riding, the early parts of it in dispair. Shorter cranks are easier to get used to, or don´t require any adjustment time, making them seem "better". I, too, have lost performance when I went from 172.5mm road cranks to 185mm. It took a long time before I was able to use them to their full potential. It´s the knee bending angle that gets to you. On riding pics, you´ll see that shorter riders tend to have greater knee angle, because the industry tries to standardize crank length. We are lucky they don´t try that for XC frames.
 
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