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Pedal Strike

Old 02-15-24, 05:44 AM
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Pedal Strike

I am new to full suspension. I rode rigid for a very long time and hard tails for quite a few years. My Habit 4 seems pretty prone to pedal strike. I am getting better at avoiding pedal strike and have played with suspension adjustments as well. Even with the suspension set to less sag than I prefer, I'd still like a bit more room to avoid pedal strike. It doesn't look like there is an option to adjust that (no flip chip or anything like that that I can see).

So without spending big bucks on longer travel suspension what options if any do I have? Or is it just a matter of being vigilant of where the pedals are rotated when rolling over roots and rocks?
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Old 02-15-24, 07:20 AM
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I am bad for pedal strikes too. First with my Norco and now with my Scott. In my experience it is just simply my poor positioning of the pedals over rough stuff and not controlling my boke as good as I could. I just need more practice But I have damaged a few pedals in my day lol.
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Old 02-15-24, 09:41 AM
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Some of the hard riding locals are going to shorter cranks, experimenting with ones as short as 150 mm. This is pretty extreme IMO, but works for them. A 150 adds an inch of travel over (presumably) your 175's.

Last edited by 2old; 02-18-24 at 11:24 PM.
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Old 02-15-24, 02:31 PM
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A few options:

1.) One is to anticipate a possible pedal strike obstacle and adjust your pedaling stroke to avoid it.
2.) Buy a FS bike with the highest BB you can find.
3.) Buy some shorter crankers.

My latest bike purchase I went with option 2 (345mm BB Height) because my previous bike had a lower BB and pedal strikes would occur often. On my newest bike it's now rare that I have a pedal strike anymore. I can't count exactly 2 in the last 3 years.

Make sure your rebound settings are correct. Slow rebound means your bike stays lower to the ground longer. Faster rebound get's you back up higher. Just don't overdo it, otherwise it will feel like the bike is trying to buck you off. If you can't make the problem go away your best solution will be shorter cranks.
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Old 02-15-24, 02:33 PM
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Lower BBs do take some getting used to, but most people do. My current FS bike is the lowest I've owned and at first I was getting a few strikes, but after a while I adapted and it does not really happen any more than it used to.

What length cranks are you using? There has been a trend to go shorter in recent years.
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Old 02-15-24, 06:15 PM
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Originally Posted by Kapusta
Lower BBs do take some getting used to, but most people do. My current FS bike is the lowest I've owned and at first I was getting a few strikes, but after a while I adapted and it does not really happen any more than it used to.
Yes, I am having fewer strikes as I have more time with the bike.

What length cranks are you using? There has been a trend to go shorter in recent years.
I don't see it in the spec. I'll have to measure. If I had to guess I'd say 170, but I may be wrong.

Edit:
I checked and the current cranks are 165mm.

Last edited by staehpj1; 02-15-24 at 06:27 PM.
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Old 02-16-24, 06:11 AM
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Originally Posted by Kapusta
What length cranks are you using? There has been a trend to go shorter in recent years.
I'll probably live with the 165s for now, but how short are folks going these days. Also how much shorter do you need to go to make much difference in having pedal strikes?

FWIW, I am decent at reading the surface and keeping the pedal rotation such that I don't get strikes over a lot of the terrain I ride, but we have a ton of roots here with short climbs that are all requiring pedaling the whole way up. I am getting pretty good at managing on the routes that I ride all the time so maybe I am learning.

Perhaps it is kind of like toe overlap on the road bike. A problem until you learn to subconsciously avoid it and then you don't see how it was ever a problem.
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Old 02-16-24, 08:50 AM
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Pretty simple 25 (25.4 actually) mm = 1 inch.
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Old 02-18-24, 10:43 AM
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Originally Posted by staehpj1
I'll probably live with the 165s for now, but how short are folks going these days. Also how much shorter do you need to go to make much difference in having pedal strikes?

FWIW, I am decent at reading the surface and keeping the pedal rotation such that I don't get strikes over a lot of the terrain I ride, but we have a ton of roots here with short climbs that are all requiring pedaling the whole way up. I am getting pretty good at managing on the routes that I ride all the time so maybe I am learning.

Perhaps it is kind of like toe overlap on the road bike. A problem until you learn to subconsciously avoid it and then you don't see how it was ever a problem.
165 is solidly on the short end of what is offered by most manufacturers. I would not go shorter just for pedal strikes.

As far as how much makes a difference…. In my experience, when going lower (either from longer cranks, lower bb, or thicker pedals) even 5mm makes a difference… at first. But then I adapt. Its less about how much actual clearance you have as much as how well you have a sense wherw that clearance ends.

Its a little bit like bar width. I’ve gone from 580mm back in the 90s to 780mm now in ~25mm increments, and each time the same thing happens: I graze a tree or two, then adapt. I don’t hit things with my 780mm bars any more than I did with my 580mm bars.

Of course there is probably a much harder limit to how low you can go with pedal clearance.
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Old 02-18-24, 11:21 AM
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Originally Posted by Kapusta
165 is solidly on the short end of what is offered by most manufacturers. I would not go shorter just for pedal strikes.

As far as how much makes a difference…. In my experience, when going lower (either from longer cranks, lower bb, or thicker pedals) even 5mm makes a difference… at first. But then I adapt. Its less about how much actual clearance you have as much as how well you have a sense wherw that clearance ends.

Its a little bit like bar width. I’ve gone from 580mm back in the 90s to 780mm now in ~25mm increments, and each time the same thing happens: I graze a tree or two, then adapt. I don’t hit things with my 780mm bars any more than I did with my 580mm bars.

Of course there is probably a much harder limit to how low you can go with pedal clearance.
That all makes a lot of sense. FWIW, I have been running with a bit less sag and a bit higher tire pressure than I prefer just to get a little more clearance and am not getting any pedal strikes lately on the trails I have been riding. I figure that maybe if I ease back to a more desirable sag and tire pressure in small increments it will help me learn to sense thje clearance better and allow me to run more ideal settings.
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Old 02-18-24, 12:32 PM
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Originally Posted by 2old
Pretty simple 25 (25.4 actually) mm = 1 inch.
I've checked your calculations, and they're correct.

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Old 02-18-24, 12:39 PM
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Originally Posted by staehpj1
That all makes a lot of sense. FWIW, I have been running with a bit less sag and a bit higher tire pressure than I prefer just to get a little more clearance and am not getting any pedal strikes lately on the trails I have been riding. I figure that maybe if I ease back to a more desirable sag and tire pressure in small increments it will help me learn to sense thje clearance better and allow me to run more ideal settings.
Yeah, I would definitely not be sacrificing optimum tire pressure or sag on the grounds of pedal clearance.
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Old 02-18-24, 03:42 PM
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Originally Posted by Kapusta
Yeah, I would definitely not be sacrificing optimum tire pressure or sag on the grounds of pedal clearance.
I agree that it isn't a solution. I tried it as an experiment to see how much difference it made with no intention of keeping the changes long term. Also, I didn't go far out of the range of normal. That said, even a little change seemed to make a lot more difference than I'd have expected.
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Old 02-18-24, 10:59 PM
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Originally Posted by 2old
Some of the hard riding locals are going to shorter cranks, experimenting with ones as short as 150 mm. This is pretty extreme IMO, but works for them. A 150 adds an inch of travel over (presumably) your 175's. In socal (for me) traction isn't a major issue and at times I've used narrower tires (mostly for weight reduction). They offer some degree of help too.
150mm are they sit and spinners? From I read for road bikes there is no lose in power if you are sitting and spinning.

The longer arms have advantage for instant power ( say like getting over a boulder on 15% grade hill etc.. ) and standing and sprinting.

I have been wanting to try 150mm on my road and maybe gravel bike. maybe I should try it on the mtb. hmm...
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Old 02-18-24, 11:24 PM
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Originally Posted by sean.hwy
150mm are they sit and spinners? From I read for road bikes there is no lose in power if you are sitting and spinning.

The longer arms have advantage for instant power ( say like getting over a boulder on 15% grade hill etc.. ) and standing and sprinting.

I have been wanting to try 150mm on my road and maybe gravel bike. maybe I should try it on the mtb. hmm...
You understand the concept well. The longer fulcrum (crank) increases power, but for my friends ground clearance is paramount since they're ferocious riding downhill and cornering. They seem to have settled on 155 and since they're in the 5'8" height range, they probably would "normally" ride 165 or 170. I have another friend with an e-MTB who had the same problem and changed to 150 or 155 with equally good results.

Last edited by 2old; 02-18-24 at 11:27 PM.
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Old 02-19-24, 07:38 AM
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Originally Posted by 2old
You understand the concept well. The longer fulcrum (crank) increases power, but for my friends ground clearance is paramount since they're ferocious riding downhill and cornering. They seem to have settled on 155 and since they're in the 5'8" height range, they probably would "normally" ride 165 or 170. I have another friend with an e-MTB who had the same problem and changed to 150 or 155 with equally good results.
A fulcrum is a pivot point. It can't be longer or shorter. The crank arm is the lever. (That much I'm pretty sure of.)

That said, the relationship of the crank arm length to power transmission is murkier than it appears to be. There are, in fact, four levers in play: the crank arm, the chainring, the sprocket, and the rear wheel.

Altering the length of any or all of those levers changes the level of pedal effort required to travel a given distance.

I always found this concept hard to get my head around, until I thought about my experiences using different gear ratios while climbing trails off-road. When I was climbing a steep trail under muddy conditions, choosing the right gear and maintaining the right pedal effort were crucial. You can just as easily lose traction (i.e., apply too much force) with shorter cranks and a slightly lower gear ratio as with longer cranks and a slightly higher ratio.

And, about "explosive sprinting power": one very successful sprinter I know who won national titles on the track over a couple of decades once mentioned to me that his secret for success in criteriums was that he always used a 50-tooth chainring. He and the other racers would usually be in the same sprocket on the back wheel, but he'd have just a bit more mechanical advantage.

Of course, some other rider might have slightly longer cranks, but that would just mean that the difference in mechanical advantage between the two was altered. Depending on the math, the longer cranks might give that other rider the edge, or they might not.

That was back when everyone else was using a 52, 53, or even 54 ring. He didn't alter the length of the crank lever arm---he altered the length of the chainring lever arm. Same effect.

In other words, it's all about the distance the bike travels versus the distance the pedal travels. The crank is just one more lever in the system.

Of course, riders with longer femurs might find longer cranks advantageous, although some recent research isn't even clear on that point.

About the math:

Sheldon Brown recognized many years ago that gearing calculations that don't incorporate crank arm length values are incomplete. He explains why and how to remedy the problem in his Web page titled "Gain Ratios-- A New Way to Designate Bicycle Gears."

From that page:

"What about crank length?

"All of these systems share a common inadequacy: none of them takes crank length into account! The fact is that a mountain bike with a 46/16 has the same gear as a road bike with a 53/19 only if they have the same length cranks. If the mountain bike has 175's and the road bike 170's, the gear on the mountain bike is really about 3% lower!"

Last edited by Trakhak; 02-19-24 at 07:46 AM.
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Old 02-19-24, 11:48 AM
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Sorry about that; I forgot it was distance from the fulcrum (guess Physics was a long time ago). When I rode dirt bikes "too much power" was a consideration, but hasn't been riding MTB's because it's always dry in socal and the traction doesn't vary much. For my friends, the only variable that was altered was crank length, so a simplified system. I always ride 175's so easy peasy. There are more important considerations than crank length.

Last edited by 2old; 02-19-24 at 11:57 AM.
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Old 02-21-24, 06:02 AM
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Originally Posted by Trakhak
A fulcrum is a pivot point. It can't be longer or shorter. The crank arm is the lever. (That much I'm pretty sure of.)

That said, the relationship of the crank arm length to power transmission is murkier than it appears to be. There are, in fact, four levers in play: the crank arm, the chainring, the sprocket, and the rear wheel.

Altering the length of any or all of those levers changes the level of pedal effort required to travel a given distance.

I always found this concept hard to get my head around, until I thought about my experiences using different gear ratios while climbing trails off-road. When I was climbing a steep trail under muddy conditions, choosing the right gear and maintaining the right pedal effort were crucial. You can just as easily lose traction (i.e., apply too much force) with shorter cranks and a slightly lower gear ratio as with longer cranks and a slightly higher ratio.

And, about "explosive sprinting power": one very successful sprinter I know who won national titles on the track over a couple of decades once mentioned to me that his secret for success in criteriums was that he always used a 50-tooth chainring. He and the other racers would usually be in the same sprocket on the back wheel, but he'd have just a bit more mechanical advantage.

Of course, some other rider might have slightly longer cranks, but that would just mean that the difference in mechanical advantage between the two was altered. Depending on the math, the longer cranks might give that other rider the edge, or they might not.

That was back when everyone else was using a 52, 53, or even 54 ring. He didn't alter the length of the crank lever arm---he altered the length of the chainring lever arm. Same effect.

In other words, it's all about the distance the bike travels versus the distance the pedal travels. The crank is just one more lever in the system.

Of course, riders with longer femurs might find longer cranks advantageous, although some recent research isn't even clear on that point.

About the math:

Sheldon Brown recognized many years ago that gearing calculations that don't incorporate crank arm length values are incomplete. He explains why and how to remedy the problem in his Web page titled "Gain Ratios-- A New Way to Designate Bicycle Gears."

From that page:

"What about crank length?

"All of these systems share a common inadequacy: none of them takes crank length into account! The fact is that a mountain bike with a 46/16 has the same gear as a road bike with a 53/19 only if they have the same length cranks. If the mountain bike has 175's and the road bike 170's, the gear on the mountain bike is really about 3% lower!"
Good post. The “more leverage” argument does not really hold up when talking about a system where you can choose whatever leverage you want with the right gear selection.

What it really comes down to is how big of a circle do you want to spin, and how fast (rpm)?
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