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So let's add this up: bad riding technique, blames tire construction while using them on narrow rims, doesn't understand rolling resistance....I'd like to see some video of this expert riding down a trail; probably dead sailors jumps and stops every km to catch his breath.

Now post yours.

Also I'm a tire engineer (automotive) and posted references for my statements already. A big part of my job is keeping semi-finished materials in weight tolerance because it's important for RR, and OE customers have strict standards for weight but apparently you know more than everyone in the tire industry.
 

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change is good
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I try to ride light tires but being a Clyde, I have different needs. Yes, on a lighter tire with a relatively thin casing, you can suffer from too much rebound and loss of traction to prevent flats and tire squirm at the required higher pressures or you suffer from the aforementioned issues. Very aggressive riders that weigh less but are crushing double black have the same needs. Over biked is relative, but if I riding smoother trails, I would be on lighter tires. I could go 2.4 DHR2/2.3 Aggressor, but it’s loose here and the bigger tires feel good. The Purg has really surprised me - it’s more like a 2.5 and it’s not squirmy even on a 30mm rim. It’s also 990gm. I don’t want to flatten out my rear tire too much, but my big butt will, and I like a rounded profile on the rear. 2.6 XR5/2.4 SE4 are faster and lighter but don’t have the casing stiffness or traction. B+ 2.8 Rekons suck as well as any other light high volume tire for this Clyde. If I’m riding 700+gm tires, I’m in the Midwest on a short travel 29er or hardtail. But if I’m on a hardtail or rigid primarily, 3.0 rocks.

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passed out in your garden
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Geez some of you carry on like wankers just cause someone has a different idea/opinion
 

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Geez some of you carry on like wankers just cause someone has a different idea/opinion
Don't you mean 'wrong opinion'?



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No doubt there are a ton of accelerations in racing which is another reason why light tires are good for racers besides just being less weight to carry uphill. There's also a point where if you don't need it for durability why would you run something heavier?

All I'm trying to get at it people seriously blow up the whole rotating mass thing when it's really not something they should bother taking into consideration for tire choice. There's to many other factors that's are far more important than a few grams.



https://www.youtube.com/watch?v=0QDnUkUaQfk


Roadie content but it still mostly applies. Seems rotational weight isn't the big deal that most people (including me) always thought it was.
 

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https://www.youtube.com/watch?v=0QDnUkUaQfk


Roadie content but it still mostly applies. Seems rotational weight isn't the big deal that most people (including me) always thought it was.
Newton's third law in action - Conservation of Momentum. We don't do enough accelerating and decelerating in cycling for it to matter much.

Within reasonable weights that we'd see in bike components it will effect suspension a little bit but tires themselves are the most effecient suspension component on the bike! So you can gain a lot of performance going to a higher volume tire at the expense of slightly slower reacting suspension due to the added weight.

You will also be carrying more weight up hill but the construction and tread makes a dramatic difference compared to around 300 grams per tire for XC vs Enduro. It's the tread and stiff construction slowing the Enduro tire down much more so than weight.

Everything has a point of optimum effeciency of course. Fat tires work in rocky rough terrain allowing the tire to mold around the terrain which maintains your forward momentum! You simply can't match that with skinny tires in rough terrain.
 

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I really want to believe this but the testing methods and the self-interest in the heavier tires kinda "make me go hmmmm....".
Time yourself on a decent length section of trail, at least a mile but maybe shorter for the climb. One climb and one flatish. Get some stick on automotive wheel weights. Stick about 300 grams evenly balanced on the inside of each rim. Try to match the effort level and time yourself on the same runs to see the difference. This will take out all variables of using a different tire and simply test the effect of weight.
 

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Are you comparing the same bike with different tires? Is this XC terrain pretty smooth?
I'm just referring to your comment about acceleration. The particular loop I looked at data for is rocky but not technically difficult, flattish but a decent amount of turning. If the surface wasn't as rough it would be a fairly flowy trail but even then there was constant large fluctuations in speed. There are very few trails near me where I'm pedaling at a relatively constant speed for any stretch of time.

I've been playing around with my insert setup on my hardtail. I just swapped the rear from a light 90g insert to a 260g insert. Initially when pedaling around the driveway it wasn't that noticeable. It was on the trail though that I noticed my energy getting sapped and not having the pep when trying to get back up to speed. This trail (different from the other I mentioned) has tons of grade and direction changes. This trail while not that difficult tends to drain newer riders because there is so much acceleration required and being able to maintain as much speed as possible as the trail turns back uphill is huge.
 

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I'm just referring to your comment about acceleration. The particular loop I looked at data for is rocky but not technically difficult, flattish but a decent amount of turning. If the surface wasn't as rough it would be a fairly flowy trail but even then there was constant large fluctuations in speed. There are very few trails near me where I'm pedaling at a relatively constant speed for any stretch of time.

I've been playing around with my insert setup on my hardtail. I just swapped the rear from a light 90g insert to a 260g insert. Initially when pedaling around the driveway it wasn't that noticeable. It was on the trail though that I noticed my energy getting sapped and not having the pep when trying to get back up to speed. This trail (different from the other I mentioned) has tons of grade and direction changes. This trail while not that difficult tends to drain newer riders because there is so much acceleration required and being able to maintain as much speed as possible as the trail turns back uphill is huge.
The insert is a massive change to the structure of the tire. The tire also has less room for deflection to absorb any rocks or roots which may cause losses of energy pushing you upward rather than forming better with the terrain and keeping you rolling forward. You're assuming the weight is the sole reason it might be draining your energy without taking into account the other variables.

Trails with lots of accelerations will always be more draining. If you add some stick on weights like I mentioned above and did back to back tests with a power meter and heart rate monitor I'd be very curious to see the results.
 

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Bipolar roller
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tires themselves are the most effecient suspension component on the bike... Fat tires work in rocky rough terrain allowing the tire to mold around the terrain which maintains your forward momentum! You simply can't match that with skinny tires in rough terrain.
Going back to the OPs original questions, this is why the extra weight of fat tires is worth it. It is simply faster on certain terrain which is most often the funnest parts of the ride ;)

Newton's third law in action - Conservation of Momentum. We don't do enough accelerating and decelerating in cycling for it to matter much.
This, and as you pointed out, with fatter tires we are able to carry more speed in rocky/rough terrain that slows us down and keep more speed out of tight corners that also slow us down as well. This is why fat bikes were 9 seconds faster than the full-sus trailbikes on the rough/rocky flat to downhill singletrack portion in the video from GMBN.
9 seconds is a lot considering all the other variables in that video.
 

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Elitest thrill junkie
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Looking at Strava data I'd say the opposite is true. On tight XC terrain there are wild fluctuations in speed.
Yeah, I'd say his statement is wildly inaccurate.
 

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The insert is a massive change to the structure of the tire. The tire also has less room for deflection to absorb any rocks or roots which may cause losses of energy pushing you upward rather than forming better with the terrain and keeping you rolling forward. You're assuming the weight is the sole reason it might be draining your energy without taking into account the other variables.

Trails with lots of accelerations will always be more draining. If you add some stick on weights like I mentioned above and did back to back tests with a power meter and heart rate monitor I'd be very curious to see the results.
Translation:

I, "Fajita Dave", believe that a tire insert makes massive changes. I also believe it reduces the tire's susp travel and ability to deform around rocks and roots, resulting in suspension losses. You're not accounting these suspension losses with your focus on elastic hysteresis.

Stop-and-go style riding will always be less efficient, especially with additional mass. If you want to prove that you're so smart, please entertain me by taking on the burden of proving this, and go do this experiment with consumer-grade measurement tools.

====

Sounds like a parroting of Jan Heine's findings. I don't argue it. A tire that doesn't deform around a bump, and rides up it, is essentially riding up a tiny hill. It all adds up. Riding through sand feels as hard as it does cause there's a hill directly in front of the tire that you're virtually climbing. A fat tire reduces the size of that "hill" since it doesn't sink as much.

On the other hand, jeremy3220 is putting this into more hardcore MTB context. A FS mtb's suspension works properly at a higher speed to do the same for bigger bumps, preventing suspension losses. Tires that fold too easily hold the rider back from properly utilizing the more advanced susp that was specifically tasked for the job.

Regarding how weight fits into the context, you can argue that the weight merely acts like a flywheel and isn't inefficient. I'd argue that all that weight requires a lot more physical effort from the body to carry it up the hill, gaining a lot more potential energy per unit of elevation. A lot of energy is wasted going into the brake pads when you descend that elevation though. The extra aero drag you face on the descent also wastes it.
 

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Massive change to the tire's construction might be an overstatement but depending on the insert used it could have a greater effect on sidewall deflection than a different tire construction itself. To many variables with the insert used in combination with a specific tire at a specific pressure for a specific terrain being ridden.

I'm not putting a $500 power meter on my Enduro bike so the only consumer grade measurement tool would be a heart rate monitor and a stop watch. I still challenge anyone to the above and add some stick on weights to their wheels to test it themselves. It will only cost a few dollars and everyone knows about how quick they should be on a section of trail they know well. None of you are going to believe me if I post my results anyway.

I've already done it quite a few years ago before I tracked rides with GPS. The results were practically identical between my normal riding setup and 400g of weights on each wheel on a 3.6 mile loop with 350ft of climbing. I specifically did this little test 10 years ago when I first got into mountain biking to see if I should go with a heavier more grippy tire. My fitness sucked and I didn't want anything making it harder. From the beginning I was skeptical that 400g between a 600g XC tire and a 1000g DH tire would make any real difference. My
expirement isolated all other variables as the rotating weight was the only change and there was no statistically significant difference between my times on the 3.6 mile loop. However, since I proved the weight didn't matter and bought some DH tires the tire construction and tread sure as hell rolled a lot slower. Which I did consider but with my inexperience in mtb components I was pretty surprised they were that much slower. I might do it again just to confirm what I've already known for the past decade.

As I also said above everything has an optimum usage. If your riding smooth trails or pavement using fatter tires than your terrain calls for will be slower. Fatter tires means there's more material to deflect so they will roll slower.

Shocks and forks are horribly inefficient compared to a tire. There's way to much friction, binding, spring pressure and mass to get moving. For absorbing the "texture" of a trail the suspension is just starting to react as the event is just about over in comparison to a tire that reacts instantly. Suspension is great but it has it's limitations just like tires do. When tires start getting to large they cave in way to easy on hard impacts or heavy loads. If you pump more psi in they get to bouncy. Goes back to that optimum usage window so buy the tire that fits your usage.

Carrying more weight up hill will obviously be slower but it doesn't matter that it's rotating unless you keep hitting the brakes. Tight curvy trails that require braking into corners will also be harder with heavier tires because braking just sucked energy out of the system. Which you now need to get back up to speed at corner exit. I also have no doubt even if you don't brake for corners there's some energy lost with knobs digging into the dirt for cornering. Energy that you'll again need to put back into the system.
 
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