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Yes, more of a statement than a belief. Ride a cheap bike with the same technique as you ride a modern stiff bike, and you'll see what I mean. Care to challenge it with some science? Newton's First Law is a solid place to start, but I'm open to hearing some quantum theories which seem to contest such laws...
A false statement. You’re on your own with that one...never heard it before...and dont think I will again.
 

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Cleavage Of The Tetons
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^^I got thrown from a pedal strike from a Stumpjumper 650 demo when they came out a few years ago. I was pedaling through a large dip in the trail and when the suspension compressed...my pedal hit the ground and I got tossed. With bikes nowadays...I'd rather have that slight bit of a margin than not.

I'm 5'8" with a 30 inseam and run 170 on all my bikes.
I'm 5'8" with a 32" inseam, 175" seems to be the sweet spot for me. That being said, I get way more pedal strikes on my new Rocky Altitude than the old version...
 

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Yes, more of a statement than a belief. Ride a cheap bike with the same technique as you ride a modern stiff bike, and you'll see what I mean. Care to challenge it with some science? Newton's First Law is a solid place to start, but I'm open to hearing some quantum theories which seem to contest such laws...
The "cheap bike" and "flexy parts" theory is backed by science?
 

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Ride a bike with a 32 29er 120mm fork into 5-6" tall curb at 10 mph. Swap in a 36 set to the same travel a2c and do the same. Would you have any confidence that the bike with the 32 fork would even continue rolling when you hit it? You'd likely brace for possible OTB, wouldn't you, right? I guarantee the 36 will roll up it without even much of a stutter or loss of speed, with absolutely no need to brace.

Now if you add in some cheap weight weenie handlebars, stem, weight weenie wheel, and deflate the tire by about 25%... do you think that all that additional flex when you hit the curb will not increase OTB risk, compared to having a stiff carbon bar, enduro-worthy wheel, firmer tire?

Note, I said same geo, so weight distro's the same. Your technique can be more relaxed on a stiffer bike, right? I experienced this on classic 71/73 geo first, with a modern 71/73 HT just plowing straight lines through rougher stuff that I used to feel compelled to go around, since flexy parts bothered me. I could simply ask why you want stiffer parts in the first place, like a 34 or Pike over a 32. It's obvious, it's for confidence. A 32 isn't gonna break if you plow through a rock garden at high speed, but you'd feel like you might break yourself if you try to go through as fast as you did if you had a stiffer fork. Are you denying this?
 

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Now if you add in some cheap weight weenie handlebars, stem, weight weenie wheel, and deflate the tire by about 25%... do you think that all that additional flex when you hit the curb will not increase OTB risk, compared to having a stiff carbon bar, enduro-worthy wheel, firmer tire?
It would probably decrease the OTB risk for the same reason enduro and DH bikes have a raked out fork with longer travel; so the spring path or 'flex' is inline with the impact force and able to absorb more of the impact. It's the same reason you bend your arms and legs riding over roots & rocks, to try and keep the bike moving forward.
 

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It's the same reason you bend your arms and legs riding over roots & rocks, to try and keep the bike moving forward.
According to our buddy that's just what they did "back in the day". Now you ride with more confidence.

Spend more money and buy heavy/stiff parts and you won't go OTB!
 

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It would probably decrease the OTB risk for the same reason enduro and DH bikes have a raked out fork with longer travel; so the spring path or 'flex' is inline with the impact force and able to absorb more of the impact. It's the same reason you bend your arms and legs riding over roots & rocks, to try and keep the bike moving forward.
Anyone else support this? Or is he on his own?

Brings up another question, is flex in crank arms beneficial? Detrimental? Has neither effect? Beliefs? Statements?

According to our buddy that's just what they did "back in the day". Now you ride with more confidence.


Spend more money and buy heavy/stiff parts and you won't go OTB!

You mean me and how I said riders back then countered flex by "getting low and behind the bars"?

What's this confident riding you speak of? Do you mean getting low and behind the bars is confident riding? Or perhaps riding without need for such technique?
 

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Discussion Starter #108
Anyone else support this?

Brings up another question, is flex in crank arms beneficial? Detrimental? Has neither effect? Beliefs? Statements?
You can feel crank arm flex!?

You are See-Fuu after all o_0

Sent from my kltedv using Tapatalk
 

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You can feel crank arm flex!?

You are See-Fuu after all o_0

Sent from my kltedv using Tapatalk
Yes, I actually can. Can you not? I can feel a difference between Shimano XT crank and a SRAM carbon crank, for instance, in terms of solid power transfer. The ring may likely play a significant factor in making the Shimano feel more solid, both using brand matched rings.

I recall a RF Ride crank with RF NW ring feeling less solid, despite having far more mass. Don't think the solid feeling is due to it being metal and having sharper feedback. Praxis shares a similar stiff feeling.

Since people were talking about power and torque earlier, flex could be considered as wasteful. Flex stores energy that's returned in an undesirable manner.
 

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Go get a road bike. Put on 170 cranks. Go climb, ride the flats, etc. Then with the same bike and gear ratio, put on 175 cranks and repeat. Report back.
I'm 5'9" and recently switched from 172.5 to 170mm crank on my road bike. Raised my seat height to fit leg extention and my average speeds went up by 1mph for the same given effort. My right knee no longer hurts on hard tempo rides and my power stroke starts sooner from the top without my knees being so high.

TdF riders also proved shorter cranks are faster because you can stay in a more aerodynamic position. Which has no real relevance for mtbing.

Both my mtb and road bike are 170 now and I wouldn't touch another bike with anything longer.

Crank length is all about fit first. If it stops pedal strikes for you then great but thats more of a technique issue. My first ride on the 170 cranks I had the worst OTB pedal strike I've ever had in 8 years.
 

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Out spokin'
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Anyone else support this? Or is he on his own?
I don't believe he's on his own, although I admit I haven't been paying close attention to this rather silly thread to know if I'm replying to the tangential spur that I think I am.

I'm here to agree with the statement that OTB is caused by weight bias, not flexy parts.

That's not to imply that I support the use of flexy parts. I've never used a crank in which I could detect flex, nor would I ever. I've detected frame flex through the BB shell/cranks plenty of times, though.
=sParty
 

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Well, here's the quip I responded to:

One advantage of short stem/wide bars is that you can keep your body center of mass nearly the same as with long stem/short bars by keeping the effective reach the same but when you are applying force to the bars it's easier to lift the front end (you're more in a deadlift form with the short stem) and you're less likely to go OTB since the bars you're putting your weight on are further behind the front wheel.
No change in geo (e.g. reach) nor center of mass. Relocating grips further behind the front wheel somehow makes Jeremy think that it makes the bike less likely to tip...

I really see no significant difference. It moves the hands back, but does it really shift your weight back? Seems like it just makes you more upright, at least if you're a type that prefers to have your shoulders no further ahead of the elbows. This in turn makes your lower back in charge of keeping the core's weight off the bars, as opposed to the extension of the arms when in a more stretched out position.

I don't see how a force from the bar affects tipping vs slipping when it's only different above the headset cups. It's like a force pulling the steerer forward, isn't it?

To look at this in context, look at tallbikes. Which ones have OTB risks? I'd argue the ones that look unstable due to flex. Ever see one with a heavily cantilevered fork?

How about being a bit more open minded? Just because it's a popular trend... what's there to lose from listening, rather than rejecting outright with prejudice/bias, going lalala false statement, never heard that before, [sarcastic statement: spend spend spend]. I can find numerous cases when it seemed to have gone too far. Shoulders forward of the elbows looks cramped and dangerous to me.
 

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Then you don't understand the physics at all.
B2D2liM.png

The stem and handlebar's primarily purpose is to turn the steerer. Bringing the hands closer to the body seemingly only makes this kid more likely to bash his face on the steering wheel. Do you rank perceived "OTB risk" second, and fit third?

Also, flex is not the same as suspension travel and arm and leg bending. The suspension stabilizes the frame and your arms+legs stabilize your core--the frame and your core don't need to rise and fall with every bump or hole. Flex doesn't do this function, nor does it offer a level of absorption. Something needs to damp the flex, else it oscillates, and typically that's your body. The suspension stores and absorbs forces coming from a single vector. Any forces perpendicular to that vector will go through the chassis, such as aft and upward forces. The HA is part responsible for tuning this vector to deal with more of one or the other.

On a road bike, which hand position is the least OTB prone? The flats, the hoods, the drops?

X1719li.jpg

Here's an exaggerated example showing how the concept of bringing hands behind the front wheel without changing anything else is flawed. I'm sure this guy will be less OTB prone if it had his bars far more forward, forcing him into a less upright position.

I feel that the ideal bar/grip position, should he look to take on some rough terrain, will allow him to comfortably get low enough, that he can transfer his inertia to the bars through his shoulders. No hanging off the back; no pulling on the bars to stay on the bike. Ideally, he shouldn't need to grip the bars much at all, and not need much energy to maintain the low ready position.

This is an example of someone with good fit and posture: Rider: Brian Lopes

And attached is a example of a good posture, but with a cramped cockpit. Rider: Greg Minnaar
 

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It's pretty well documented that shorter cranks don't reduce power outputs. Most riders would benefit from shorter arms. In a perfect world, it would be nice to see crank arm choices at 2.5 increments. Just because the bike industry makes a few sizes doesn't mean they are correct for you.
 

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Not sure if this is addressed above, but thought I would ask.

Does actual length of a crank arm change from size to size or is it strictly the pedal attachment hole that is being drilled higher or lower?

I ask because I had a CS rep tell me (not at this manufacturer) the only difference on the RaceFace Aeffect R crankset was the hold placement. The overall length of a 170mm was the same as a 175mm, it was simply the 5mm difference holes.

I don't have two of the same models to confirm this so just wanted to check.
 

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Not sure if this is addressed above, but thought I would ask.

Does actual length of a crank arm change from size to size or is it strictly the pedal attachment hole that is being drilled higher or lower?

I ask because I had a CS rep tell me (not at this manufacturer) the only difference on the RaceFace Aeffect R crankset was the hold placement. The overall length of a 170mm was the same as a 175mm, it was simply the 5mm difference holes.

I don't have two of the same models to confirm this so just wanted to check.
Depends on the model. I know Sram NX cranks use the same body for 170 and 175mm. I believe Sram's carbon cranks use different length bodies for 170 and 175
 

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Not sure if this is addressed above, but thought I would ask.

Does actual length of a crank arm change from size to size or is it strictly the pedal attachment hole that is being drilled higher or lower?

I ask because I had a CS rep tell me (not at this manufacturer) the only difference on the RaceFace Aeffect R crankset was the hold placement. The overall length of a 170mm was the same as a 175mm, it was simply the 5mm difference holes.

I don't have two of the same models to confirm this so just wanted to check.
Hi I'm not sure what the rep was talking about but yes the length definitely changes.
 

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Disgruntled Peccary
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I have a set of 170mm Affect R cranks. I don't see how they can be correct.
 
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