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Do all mtb's generally have the same pedal-to-pedal width?

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Do all mtb's generally have the same pedal-to-pedal width?

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Old 04-03-10, 09:45 AM
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Do all mtb's generally have the same pedal-to-pedal width?

Hi

Even after getting a pro fit kit on my roadie, I'm still having ITB pain in my left knee. I'm in a super comfortable position and i'm very efficient, but that knee problem just won't go away. Funny thing about it is that I don't get that problem on my mtb at all. I thought it may be due to float, but i've tried the roadie with lots of float, pain is still there.

So I started looking at the geometry to see where the significant differences are, starting at the torso and going down to the foot.

I found that in measuring the crank arm widths between my roadie (Trek 5.2) and my mtb (Trek 4300) that the distance from inside pedal to inside pedal (can't remember the term for this) was 2.25" wider on the mtb.

In my mind 2.25" difference is a lot! So my question is do all mtb's generally have the same pedal-to-pedal width?

Last edited by xfimpg; 04-03-10 at 09:50 AM.
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Old 04-03-10, 05:08 PM
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No. The q-factor on the crank (how far the crank sticks out) has a lot to do with it.
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Old 04-03-10, 05:35 PM
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Originally Posted by mzeffex View Post
No. The q-factor on the crank (how far the crank sticks out) has a lot to do with it.
Thanks

I'm looking at getting a Gary Fisher Roscoe

http://www.fisherbikes.com/bike/archivemodel/465

and in the goemetry section it doesnt identify q-factor.

How do I find out the q-factor of a given bike, other than being in the shop and measuring it?
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Old 04-03-10, 05:43 PM
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I'll elaborate some more on what mzeffex said. Q-factors vary because of:
  • Variations from manufacturer to manufacturer of cranksets themselves;
  • Bottom bracket shell widths (which can be 68 or 73 mm on 'regular' mountain bikes to 83 on many DH bikes)
  • Bottom bracket widths - - whether or not they have external or internal bearing cups
  • Bottom bracket spindle widths - - which can vary to accommodate chain guides, three-or two-ring setups, etc.

There are just so many variables any more, there is no one MTB 'standard.' Two of the major reasons MTB Q-factor is so much greater than your road bike is because extra room is needed for triple-ring cranksets and to clear the chainstays - - which are spaced a lot farther apart to clear fat tires.

Hope that helps.
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Old 04-03-10, 06:07 PM
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Originally Posted by dminor View Post
I'll elaborate some more on what mzeffex said. Q-factors vary because of:
  • Variations from manufacturer to manufacturer of cranksets themselves;
  • Bottom bracket shell widths (which can be 68 or 73 mm on 'regular' mountain bikes to 83 on many DH bikes)
  • Bottom bracket widths - - whether or not they have external or internal bearing cups
  • Bottom bracket spindle widths - - which can vary to accommodate chain guides, three-or two-ring setups, etc.

There are just so many variables any more, there is no one MTB 'standard.' Two of the major reasons MTB Q-factor is so much greater than your road bike is because extra room is needed for triple-ring cranksets and to clear the chainstays - - which are spaced a lot farther apart to clear fat tires.

Hope that helps.
Yes it does! Thanks to both of you!
Looks like i'll need to measure myself at the LBS... should be an interesting site! lol
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Old 04-04-10, 11:57 AM
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Here's a chart of various crank q-factors http://forums.mtbr.com/showpost.php?...87&postcount=2. Most guys are looking to narrow their q-factor to mimic their road bikes, your needs are a bit different it seems (I'm also fairly comfortable on wider q-factor setups).
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Old 04-04-10, 02:21 PM
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Originally Posted by bikinfool View Post
Here's a chart of various crank q-factors http://forums.mtbr.com/showpost.php?...87&postcount=2. Most guys are looking to narrow their q-factor to mimic their road bikes, your needs are a bit different it seems (I'm also fairly comfortable on wider q-factor setups).
Now that is just awesome!
Thanks!
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Old 04-04-10, 10:20 PM
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With ITB, a wider set of cranks would help... there is a less medial angle of your leg(are you a big guy?). Also I think getting a pair of shoes with a lot of arch support would help if you have high or weak arches.

Have you been to a physiotherapist? The symptoms may seem like ITB but the cause can be a bunch of things, especially if it is your left-leg only.
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Old 04-05-10, 06:22 AM
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Originally Posted by electrik View Post
With ITB, a wider set of cranks would help... there is a less medial angle of your leg(are you a big guy?). Also I think getting a pair of shoes with a lot of arch support would help if you have high or weak arches.

Have you been to a physiotherapist? The symptoms may seem like ITB but the cause can be a bunch of things, especially if it is your left-leg only.
Just a tad over average size, 6.1 and 200lbs. My left leg is .5 inches shorter than the right, the tibia happens to be the shorter of the two compared to the right left. I did get a Fit Kit done, which includes verifying your foot type and I didn't need any arch support (thank god), the fitter happens to also be an orthopedist.

I agree with you for a wider q-factor. With my old Trek 4300, I rarely had itb pain and when i did it was only slight at most. My feet do also tend to swing out when i walk. I'm really hoping that the q-factor is the solution. Besides, i prefer mountain biking over road cycling anyways!
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Old 04-05-10, 09:32 AM
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I read on a custom frame builder's site somewhere some info. about fitting people with two different length legs and how it differs depending on whether it's the upper leg or the lower leg. I'm afraid I don't remember the builder or the site, but I do remember him saying that for a shorter lower leg, as long as the hip to knee distance matches, all that's needed is a spacer like a block on the pedal or a thicker soled shoe to make up the difference on the shorter side. You might ask your fitter/orthepist about it.
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Old 04-05-10, 10:58 AM
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Originally Posted by xfimpg View Post
Just a tad over average size, 6.1 and 200lbs. My left leg is .5 inches shorter than the right, the tibia happens to be the shorter of the two compared to the right left. I did get a Fit Kit done, which includes verifying your foot type and I didn't need any arch support (thank god), the fitter happens to also be an orthopedist.

I agree with you for a wider q-factor. With my old Trek 4300, I rarely had itb pain and when i did it was only slight at most. My feet do also tend to swing out when i walk. I'm really hoping that the q-factor is the solution. Besides, i prefer mountain biking over road cycling anyways!
Did you get a custom shoe for the left foot to even things out? Was the length discrepancy caused by an old injury?

I'm not sure what is involved in the fit kit but, the reason i ask about the left foot pronating is because your symptoms seem to get better with the wider q-factor... which means to me(not a GP) that the leg length discrepancy wasn't the primary cause of the ITB. Another thing to look at would be if your left-knee is caving in, is your left foot remaining straight or does the heel twist at the bottom of a powerful stroke? Is your heel moving lower than level? It could be the muscle in your butt which helps to stabilize the left leg(gluteus medius) is not firing properly to keep your left leg straight.

Anyways, you didn't ask about all that and i am rambling.
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Old 04-05-10, 11:17 AM
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Originally Posted by electrik View Post
Did you get a custom shoe for the left foot to even things out? Was the length discrepancy caused by an old injury?

I'm not sure what is involved in the fit kit but, the reason i ask about the left foot pronating is because your symptoms seem to get better with the wider q-factor... which means to me(not a GP) that the leg length discrepancy wasn't the primary cause of the ITB. Another thing to look at would be if your left-knee is caving in, is your left foot remaining straight or does the heel twist at the bottom of a powerful stroke? Is your heel moving lower than level? It could be the muscle in your butt which helps to stabilize the left leg(gluteus medius) is not firing properly to keep your left leg straight.

Anyways, you didn't ask about all that and i am rambling.
No worries! It's actually more fun discussing with someone else than banging my head against the wall.

Leg length is a defect from the manufacturing plant (my parents). lol

The bike fitter was an orthopedist, he checked out my foot and confirmed that I have a neutral foot and did not need orthotics. I hope he's right.
I have noticed when walking that my left foot does tend to come out more than my right.

Another thing to look at would be if your left-knee is caving in
- after the Fit Kit session, my left leg was pretty much straight, but not as straight as my right. I did notice that my inner leg touching the top tube was more obvious than the right leg.

is your left foot remaining straight or does the heel twist at the bottom of a powerful stroke? Is your heel moving lower than level? It could be the muscle in your butt which helps to stabilize the left leg(gluteus medius) is not firing properly to keep your left leg straight.
- I do remember the fitter pointing out that both my heels were pointing outwards when i would stop pedaling, and he corrected this.

I did try pedal extenders, before the fit kit session; my left leg seems fine, but now it was my right that was hurting. Maybe just the pedal extender on the left side, I've thought about it but it seemed "strange".

Crazy stuff, isn't it?
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Old 04-05-10, 11:54 AM
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Originally Posted by xfimpg View Post
No worries! It's actually more fun discussing with someone else than banging my head against the wall.

Leg length is a defect from the manufacturing plant (my parents). lol

The bike fitter was an orthopedist, he checked out my foot and confirmed that I have a neutral foot and did not need orthotics. I hope he's right.
I have noticed when walking that my left foot does tend to come out more than my right.

Another thing to look at would be if your left-knee is caving in
- after the Fit Kit session, my left leg was pretty much straight, but not as straight as my right. I did notice that my inner leg touching the top tube was more obvious than the right leg.

is your left foot remaining straight or does the heel twist at the bottom of a powerful stroke? Is your heel moving lower than level? It could be the muscle in your butt which helps to stabilize the left leg(gluteus medius) is not firing properly to keep your left leg straight.
- I do remember the fitter pointing out that both my heels were pointing outwards when i would stop pedaling, and he corrected this.

I did try pedal extenders, before the fit kit session; my left leg seems fine, but now it was my right that was hurting. Maybe just the pedal extender on the left side, I've thought about it but it seemed "strange".

Crazy stuff, isn't it?
Yes, when everything works nicely it's great... but the body is quite complicated and trying to track down the source of a malfunction is not easy. What you are describing with your feet splaying outwards is sounding like duck feet/foot eversion. Sometimes if it is just one foot it may mean a hip injury or something from the parents... if you lay on your back and put both feet together then relax, if the left one falls further that is suspicious. From what i have read the source of duck feet is usually something further up the leg in either a muscle which adducts or abducts the leg. It is a problem which can be masked by simply making everything look normal down by your foot but the imbalance is from somewhere else.

For most people problems of misuse never really appear since they just don't do enough physical activity... but once you start to get serious all sorts of bad habits and old injuries just decide to crash your party.
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Old 04-05-10, 12:08 PM
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Originally Posted by electrik View Post
Yes, when everything works nicely it's great... but the body is quite complicated and trying to track down the source of a malfunction is not easy. What you are describing with your feet splaying outwards is sounding like duck feet/foot eversion. Sometimes if it is just one foot it may mean a hip injury or something from the parents... if you lay on your back and put both feet together then relax, if the left one falls further that is suspicious. From what i have read the source of duck feet is usually something further up the leg in either a muscle which adducts or abducts the leg. It is a problem which can be masked by simply making everything look normal down by your foot but the imbalance is from somewhere else.

For most people problems of misuse never really appear since they just don't do enough physical activity... but once you start to get serious all sorts of bad habits and old injuries just decide to crash your party.
Also, I have Time Atac's on my mtb and Look Keo on my roadie. Lots of float with the Time, no float with the Keo's (mind you i have tried up to 9 degrees of float to no avail). I think the Time float would help in my case.

I tried the test you suggested and strangely enough it's the right foot that leans further away, about a 1/4". Okay, this is creepy now.
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Old 04-05-10, 12:49 PM
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Originally Posted by xfimpg View Post
Also, I have Time Atac's on my mtb and Look Keo on my roadie. Lots of float with the Time, no float with the Keo's (mind you i have tried up to 9 degrees of float to no avail). I think the Time float would help in my case.

I tried the test you suggested and strangely enough it's the right foot that leans further away, about a 1/4". Okay, this is creepy now.
Hahaha... i'm not sure 1/4" is drastic but, you did say that your right leg hurt when you tried the extenders. Perhaps there is some sort of compensation going on between your left/right leg, tbh spending a visit or two with a recommended sports therapist might be time well spent. Maybe doing some isometric exercise like pistol squats would give you more insight to an imbalance.

About pedals with a lot of float, i'm not sure it's good... it may encourage excessive rotation of the foot because the rotation about cleat is easier when compared to friction of a sole when walking. Do you wear out the left/right cleat quickly? Checking the wear patterns on the cleat can be informative. If you wearing the outside left of the heel on your shoe, that may mean your foot is already crooked when it hits the ground instead of rotating outwards when you push down. If the foot is rotating while pedaling hard it may mean a weak ad/abductor muscle but if the running shoe is worn out it may mean your gait is off and a muscle is simply misfiring causing the misalignment. There are other issues related to your anatomical structure which may be causing it also. The pelvis/hip may simply be misaligned, maybe there is sclerosis of the spine which could mean misalignment of the pelvis... it is a long list.

These are all just guesses, since i have no official training, some investigation on your behalf would be better. Don't let me alarm you!
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Old 04-05-10, 01:17 PM
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Originally Posted by electrik View Post
Hahaha... i'm not sure 1/4" is drastic but, you did say that your right leg hurt when you tried the extenders. Perhaps there is some sort of compensation going on between your left/right leg, tbh spending a visit or two with a recommended sports therapist might be time well spent. Maybe doing some isometric exercise like pistol squats would give you more insight to an imbalance.

About pedals with a lot of float, i'm not sure it's good... it may encourage excessive rotation of the foot because the rotation about cleat is easier when compared to friction of a sole when walking. Do you wear out the left/right cleat quickly? Checking the wear patterns on the cleat can be informative. If you wearing the outside left of the heel on your shoe, that may mean your foot is already crooked when it hits the ground instead of rotating outwards when you push down. If the foot is rotating while pedaling hard it may mean a weak ad/abductor muscle but if the running shoe is worn out it may mean your gait is off and a muscle is simply misfiring causing the misalignment. There are other issues related to your anatomical structure which may be causing it also. The pelvis/hip may simply be misaligned, maybe there is sclerosis of the spine which could mean misalignment of the pelvis... it is a long list.

These are all just guesses, since i have no official training, some investigation on your behalf would be better. Don't let me alarm you!
LOL I'm already alarmed!

You're right, 1/4" between the two feet is not something to be alarmed about. lol

Thanks for exchanging, you brought up some interesting points.

Cheers
Mike
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