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Tandem Cycling A bicycle built for two. Want to find out more about this wonderful world of tandems? Check out this forum to talk with other tandem enthusiasts. Captains and stokers welcome!

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Old 03-28-12, 10:54 PM   #1
rdtompki
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Looking for Pedal Suggestion for Stoker

My wife is having some right leg pain, probably contributed to by the excursions made by her right knee. That having been said were making some adjustments and the PD-M540 Shimano SPDs seem to have much more offset than her relatively small feet require. I've measured 53mm from the outer surface of the pedal spindle to the center line of the cleat. So I'm looking for pedals will a reduced offset.

While this is not a tandem-specific question, it may be a more common issue for the tandem stoker position since the stoker is usual less than average male height and the Q-factor may not be all that favorable. I doubt moving the pedal centerline "in" will cause any other issues with the heel striking either the chainstays or the cranks.

I'm looking around on the web, but pedal drawings seem a bit hard to find. Definitely would like to stick with MTB-style pedals, but they don't have to be SPDs. Any and all suggestions gratefully accepted.

Last edited by rdtompki; 03-28-12 at 10:55 PM. Reason: typo
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Old 03-29-12, 07:20 AM   #2
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Are you saying you want the pedals further inboard? My only suggestion then might be Speedplay pedals with replacement spindles (which come in various sizes).
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Old 03-29-12, 07:43 AM   #3
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This is precisely why we had our Roholoff tandem built: to lower the stoker's Q-factor as much as possible. With 135mm rear spacing, a double crankset and no front derailleur, she loves it.

BTW: Speedplay offers longer spindles for their pedals, but not shorter ones.
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Old 03-29-12, 08:07 AM   #4
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How much do the stoker cranks clear the chain stays? If there is much clearance of the chain stays you might find a crank with less Q factor. The problem with tandems is the 145 mm or 160 mm rear drop out spacing moves the chain stays out farther and the crank has to clear the chain stays. Another factor to consider is the crank arm length. If you wife is riding 170 mm cranks she might be better off with 165 or 160 mm crank arms. I see that you ride a daVinci and I think that they make several lengths of crank arms.

Sheldon
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Old 03-29-12, 08:34 AM   #5
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How much do the stoker cranks clear the chain stays? If there is much clearance of the chain stays you might find a crank with less Q factor. The problem with tandems is the 145 mm or 160 mm rear drop out spacing moves the chain stays out farther and the crank has to clear the chain stays. Another factor to consider is the crank arm length. If you wife is riding 170 mm cranks she might be better off with 165 or 160 mm crank arms. I see that you ride a daVinci and I think that they make several lengths of crank arms.

Sheldon
The engineer in me came out and I over-described the situation. Yep, I want to move the pedals inboard. The cranks just clear the chainstays so a different brand of crank wouldn't help. I don't know if that 53mm figure is common, but I'm going to look around; I'm reluctant to move the shoe inboard by moving the cleat since that changes the center of pressure. Regarding the crank length, I had already considered that for a number of reasons. Current cranks are 170mm and I'm thinking of 160mm so I can make a noticeable change in the range of motion.
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Old 03-29-12, 09:10 AM   #6
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Maybe this is a stupid question, but are you sure the pain is due to the large Q factor and not to the centering float mechanism in the SPD pedals? You might want to consider changing to free float pedals (Speedplay Frogs if you prefer mtb shoes) before tinkering with the crankset. This might allow your stoker to adjust her feet position to naturally compensate for the crankarm position. While I can't guarantee that this would work, it seems as an easy first move in trying to correct the situation. Our experience: my wife developed a knee pain after two seasons on SPDs, she changed to Speedplays and all became good. I continue riding SPDs without any issues.
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Old 03-29-12, 09:23 AM   #7
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I agree that additional float might help. If the foot is moved out more than it should be the ankle will rotate the heel in in an attempt lesson stress on with the knee and hip. This result in a toes out - heels in pedaling style. That being said it may not fix your problem. Sometimes it comes down to trial and error.

I use these pedals which have a lot of free float and I think have fairly short axles. They work like a steel version of Speedplays. I will try to measure them and post the results. The company responds to emails so if you search for the company you can email them for the official specs.

http://www.universalcycles.com/shopp...ils.php?id=685
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Old 03-29-12, 10:24 AM   #8
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Seems to me I read somewhere that road pedals, in general, have less "q" factor. Suggest you take your 540's to a good lbs and compare them with Shimano A600 or A520. These are classed as road pedals, but they allow use of your current recessed cleats and walking shoes. These pedals are essentially the same except the A600 has an anodized finish and weighs a few grams less.
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Old 03-29-12, 11:15 AM   #9
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Most people do best with the limited float, such as provided by SPDs, because limited float prevents the knee or ankle getting at too odd an angle while pedaling. However, some people do better with unlimited float. Other people do better with zero float because that holds their ankle and knee in alignment. It can be a little difficult to diagnose exactly what the problem is. With limited or no float, it is important to get the cleat position correct. There's a short article about float adjustment here:
http://www.beginnertriathlete.com/cm...articleid=1954

It's also my guess that it's float or cleat position that's the culprit rather than q factor.
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Old 03-29-12, 11:22 AM   #10
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Great suggestions above. I'm going to look at the Speedplay frogs or similar. My wife doesn't want to try and correct her right leg excursions; might be the result of some ancient injury as she was a high-level athlete for years. The shorter cranks might be more of interest in terms of bringing our natural cadences more in line.
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Old 03-29-12, 11:27 AM   #11
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Another thing to try in your search for pain free cycling is arch support. For years of cycling my right knee did not track straight when I pedaled. This of course put pressure on my knee. Finally I tried an arch support in my right shoe and it has fixed the issue. Apparently my arch would fall during the power phase pulling my knee inward toward the top tube. E-Soles makes some good arch supports if you want to give it a try.

What I leaned is that if there is pain keep trying things and don't give up. It may seem expensive but pain free riding is more valuable than anything made out of carbon or Ti.
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Old 03-29-12, 12:56 PM   #12
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Have you thought about cleat wedges? If the sole of her forefoot is naturally angled inward or outward, that's going to put stress on the knee. You used to have to do custom orthotics to fix this, but now there are wedges you can put under your cleats that will angle the foot relative to the pedal surface. Changing the angle can move tthe knee inward or outward. For years, people made jokes about my knees-out pedaling style, and it's only recently that I put two and two together and realized that it was because of my feet, my feet naturally tilt outward. I'm opposite most people, though -- most people's feet tilt inward. Anyway, you can get the wedges here: http://www.bikefit.com/
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Old 03-29-12, 01:00 PM   #13
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Originally Posted by waynesulak View Post
Another thing to try in your search for pain free cycling is arch support. For years of cycling my right knee did not track straight when I pedaled. This of course put pressure on my knee. Finally I tried an arch support in my right shoe and it has fixed the issue. Apparently my arch would fall during the power phase pulling my knee inward toward the top tube. E-Soles makes some good arch supports if you want to give it a try.
This is interesting, I was really dumb not to think of this. My wife had problems with a falling arch in her foot! The Speedplay Frogs corrected the knee pain when cycling, but if it ever returns I know now where to look! Thanks for pointing this out.
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Old 03-29-12, 02:41 PM   #14
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Originally Posted by WheelsNT View Post
Have you thought about cleat wedges? If the sole of her forefoot is naturally angled inward or outward, that's going to put stress on the knee. You used to have to do custom orthotics to fix this, but now there are wedges you can put under your cleats that will angle the foot relative to the pedal surface. Changing the angle can move tthe knee inward or outward. For years, people made jokes about my knees-out pedaling style, and it's only recently that I put two and two together and realized that it was because of my feet, my feet naturally tilt outward. I'm opposite most people, though -- most people's feet tilt inward. Anyway, you can get the wedges here: http://www.bikefit.com/
Wedges are also a good thing to try. Methodical trial and error can be a good thing. I suggest that you keep track of what was used and the results so that you can refer back and draw conclusions.
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Old 03-30-12, 11:33 AM   #15
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My wife has also been having knee issues. We've gone to 130's for her crank length and this has helped. Her inseam is 30.5 inches. Speedplay frogs have also helped. She's recovering from knee surgery and we still haven't gotten her totally well though.

For information on short cranks try this: http://www.powercranks.com/cld.html

Here is a link to an interesting site for wedges/bikefitting: http://www.stevehoggbikefitting.com/articles/footloose/

I don't know if I read it on the above link or not, but I seem to remember reading that if the knee dives inward a varus wedge is needed for correction. If the knee moves laterally then the Q needs to be increased/and or cranks shortened. Here's a link about Q: http://www.slowtwitch.com/Tech/Stance_Width_2562.html

Good luck, I hope your wife's knee issues resolve.

Jack
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Old 03-30-12, 06:06 PM   #16
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Stoker Kay has some foot issues.
She tried clipless pedals and there just was not enough float for her feet and she then developed knee issues.
She went back to mt. bike toeclips which give her loads of float.
Problem solved for her.
Pedal on!
Rudy and Kay/zonatandem
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