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Discussion Starter · #1 ·
Hello wise and all knowing gurus of MTB science!! I didn't see a "Medical/First Aid" subforum, so GD it is. :thumbsup:

I have recently moved from my 1993 Trek 930 size 19.5 to a 2005 Jamis Dakar Sport size 17. The overall feel is better as I sit inside rather than on top of the bike, but I have begun to experience some pain in the top region just above my knee. :mad:



On the bigger Trek, I never had any troubles even after 2+ hours on the bike. With the smaller Jamis, I feel it after 10 minutes of riding and the soreness can still be felt 4 days after my last trip out. I've played with the seat position on the seatpost...pulling it back, bringing it close. It didn't matter. Then I tried adjusting the seat height position and still the pain persists. The length from the bottom bracket to the top of the saddle (along the seatpost) is currently 27 inches...what wrench science recommended for me. Unfortunately, I cannot remember that distance on my previous Trek. Going higher may help the knee, but even at that height I already feel "up in the air" and slightly out of control on a downhill.

Is there anything else that can be done? Is this the type of issue that can be remedied by going to a smaller crank size? They're currently and older square taper 175mm and I'm 5'7" 160 for reference.

Thanks!!

Jod ;)
 

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NormalNorm
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Did your new bike come with new pedals....or are using your old ones? maybe the float on the new pedals is different???
 

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Discussion Starter · #3 ·
Same pedals. Shimano...hmmm...cheap clipless from 2000. I didn't change the tension on them at all. Tho I found the left harder to get out than the right, so I checked em the other day and found the left pedal a few clicks higher than the right. Changed em both to 5 clicks from loosest.
 

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Something is wrong with your setup. Either your seat is too low or your clip in point is too far forward, which is causing too much pressure and strain on your knee. Based on your post, I'd guess the problem is that your seat is too low.

Note that your optimal seat height for pedaling is not going to be same as the optimal seat height for you to feel comfortable on downhills. You've basically got two options: (1) find a comfortable compromise between the two heights; or (2) invest in a gravity dropper seat post, which will allow you to change your seat height on the fly out on the trail (or you can stop and do it manually as the situation calls for it). If you have weak knees or a history of knee problems, the first option might not be possible. It might also help to move your clip-in point so that it is as far back as possible on your shoe (i.e., your foot is as far forward on the pedal as possible).

Note that the pain in your knee will carry over between rides. It won't immediately cease as soon as you make an adjustment. You might want to take a little time off, let the pain subside, and then play around with different heights, finding the lowest seat height that doesn't cause your knee to hurt.

EDIT: You may be able to improve your DH comfort level with your seat being higher up by also raising your hand position (e.g., with a higher rise bar, or taller stem).
 

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Yeah it sounds like you've got the saddle at the wrong height. You don't want to be fully extended at the bottom of your stroke, you want to have just a little bend. One way I've seen to properly adjust your seating position is to put your heel on the pedal and set your seat at a height where at the bottom of the stroke you are fully extended. The idea being that the ball of your foot when you're actually pedaling will give you just the right amount of bend at the knee.

I usually adjust my seat until I have just a little flex and then mess with it until I find the most comfortable position.
 

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Discussion Starter · #7 ·
ShaneMac - The saddle is about 2-3 inches higher now.

TLud - I'm not sold on the gravity dropper because I never felt like my old Trek's saddle needed to be raised/lowered for specific sections of the trail. It's really odd because I've never had knee problems either. In fact, the bike switching is the first time I've had and issue with pain in the knee. My cleats are all the way back and away towards the outside of the shoe. Perhaps I could move them all the way towards the inside of the shoe? My stem is a short 70mm with a Race Face Evolve DH riser bar. I'll be hitting the trail tomorrow, we'll see about the seat going even higher.

Sonicsuby - That sounds reasonable/easy enough...and that's where I'm at. I've got full extension with the heel at the bottom crank position. It feels like my knees go up to high/have too big a circle relative to my older bike.

So it seems my options are:

1. Play with the cleats and move them from outside of shoe to inside
2. Raise the seat even more/play with seat/seatpost position (forward or backward)
3. Get 170mm cranks
 

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Sounds like thi bike need to be "fit" to you. How tall are you? Going from a 19.5 to a 17 is a big differance. Your lbs should have fit the bike for you before you rode off. Sounds like a seat adjustment problem, you may also need a differant stem length.

Sean
 

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Discussion Starter · #9 ·
Well, I had upgraded my Trek many times and recently bought a new shock for it. Then I saw a deal on Jensen for the Dakar Sport frame...

I'm new to the AZ area and got the build done by a LBS. I just didn't feel the "love" from them, hehe. I'll have to poke someone in that forum for recs.
 

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Not to be a downer about your new ride, but it sounds like the geometry of the new frame is wrong for you. Were you measured for this frame or have you ever been fit for a bike before?

Playing baseball through high school, I was a catcher so I've had a lot of knee problems. So I'm pretty sensitive to bike fit. If the frame geometry is wrong for me, my knees will tell me. For me, this most commonly occurs with a frame that is too small. For example, I recently demoed a Titus Moto-Lite. The shop owner told me it was a large, and I took it out without paying much attention. I set the seat where it felt reasonably comfortable, but an hour later, I was back complaining about my knees. Sure enough, he looked at it and it was a medium. Not necessarily saying this is the case for you, but it's something to look at.
 

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Discussion Starter · #11 ·
Didn't get fit for it. Just bought a good deal on the net. Or so I thought, hehe. I'm only 5'7" tho, how could a 17" possibly be too small? I'll be playing around some more with the seat and clips over the weekend in Flag.

Thanks for all the suggestions guys. I think I'll have to get myself down to a good quality reputable shop to see if the bike's gonna work for me. As for this one, I definitely feel as tho my knees are in my chest too much...
 

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Best thing I can think of is adjust the seatpost, like stated before, adjust the pedals. If that doesn't work take the bike to the LBS and have them fit you.
 

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When I change bikes

I make some comparisons between the two bikes. I line them up next to each other at teh crank and just look at them. The differences between them are revealing. If my old cockpit positoin was working for me I try to duplicate this on the new bike and let the other differences fall where they may.
I drop a plumb line from the nose of the saddle and see where it rests vis-a-vis the bb. I set the nose of the saddle in the identical place on the new bike. I also take a measurement from the crankbolt to the top of the saddle above the seatpost and use this mesurement to set the seat height on the new bike. As long as you use the same seat adn crank length you will be in the same postion for power to the pedals.
I also take a measurement from teh nose of the saddle to teh middle of the bars and use this to set the distance to the bars on the new bike. I use a level to determine how high or low the bars were viv-a-vis the now-set saddle and duplicate this.
This method makes for a great starting point. I have used this on all of my bikes and my sons' as he has grown from one bike to another. It makes the whole process a bit less wild.
 

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My neighbor gave me an old issue of Cycling magazine last night to help me fit myself to my new road bike. When I get home this afternoon I'll try to remember to post up the info in there. It seems pretty helpful.
 

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Jodiuh said:
Didn't get fit for it. Just bought a good deal on the net. Or so I thought, hehe. I'm only 5'7" tho, how could a 17" possibly be too small? I'll be playing around some more with the seat and clips over the weekend in Flag.

Thanks for all the suggestions guys. I think I'll have to get myself down to a good quality reputable shop to see if the bike's gonna work for me. As for this one, I definitely feel as tho my knees are in my chest too much...
The saddle height, as everyone mentioned will make a difference.

The other major item is saddle fore / aft adjustment.

Regarding saddle height. The saddle to pedal distance should be set so that at full extension, your leg has just a slight bend at the knee. If your hips rock when you pedal, it's too high. You mentioned that raising the saddle makes you feel like you're too far up in the air... or something like that. Since it's a smaller frame than your previous bike, you will be more upright... and the same saddle height as before will put your center of gravity higher than before. You'll just have to get used to that. The correct saddle height has nothing to do with frame size.

The other item that can give you knee pain is if the saddle is too far forward. If the front of your kneecap (on your forward foot, with the pedals at 3/9 0'clock) is in front of the pedal spindle, then it can be very rough on your knees. In that case, move the saddle towards the rear of the bike.
 

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I don't suggest playing around with this until you have established you base cleat, seat height and seat fore/aft position. Use the Lemond method but make sure you start with your cleats.

https://www.bikenow.com.au/u-fit/saddle_height.htm

Since you already seem to have some irritation/inflamation, you may not notice an immediate difference so if you want to play with minor changes wait until the pain is gone. And even then make changes in small 2-3 millimeter increments. I'm guessing you can continue to right and still get better once you have set up the correct cleat, seat height and fore/aft position but I would recommend riding in lower gears and slowly increasing as your knee feels better.

hope that helps.

Jodiuh said:
Hello wise and all knowing gurus of MTB science!! I didn't see a "Medical/First Aid" subforum, so GD it is. :thumbsup:

I have recently moved from my 1993 Trek 930 size 19.5 to a 2005 Jamis Dakar Sport size 17. The overall feel is better as I sit inside rather than on top of the bike, but I have begun to experience some pain in the top region just above my knee. :mad:



On the bigger Trek, I never had any troubles even after 2+ hours on the bike. With the smaller Jamis, I feel it after 10 minutes of riding and the soreness can still be felt 4 days after my last trip out. I've played with the seat position on the seatpost...pulling it back, bringing it close. It didn't matter. Then I tried adjusting the seat height position and still the pain persists. The length from the bottom bracket to the top of the saddle (along the seatpost) is currently 27 inches...what wrench science recommended for me. Unfortunately, I cannot remember that distance on my previous Trek. Going higher may help the knee, but even at that height I already feel "up in the air" and slightly out of control on a downhill.

Is there anything else that can be done? Is this the type of issue that can be remedied by going to a smaller crank size? They're currently and older square taper 175mm and I'm 5'7" 160 for reference.

Thanks!!

Jod ;)
 

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So Jodiuh, have you managed to find a solution to your knee problem? Have you dropped a plumb down from your knee to make sure it either intersects the pedal shaft or falls behind it as BlueShorts said? Saddle height is a known cause of knee pain, but for/ aft I think causes more severe problems than slight height differences.
 

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Discussion Starter · #18 · (Edited)
Mastamind - That's exactly what I did. After raising another inch on the trail, most of the pain went away. It still felt uncomfy tho.
Berkeley Mike - I did take some measurements of my Trek 930, but not the saddle height. :( The plumb line shall be used in future endeavors.
sonicsuby - Did you ever find that article?
Blue Shorts - I didn't play with the fore / aft adjustment, but the bike shop did. :D It was too far back.
oscarc - Interesting read, I've printed it out for reference.
LyNx - Yes I have!! Here's what happened.

On Friday morning I brought my bike back to the Cactus in PHX for the " new cable" readjustment. I got there early and Fish readjusted the cables. Then Sean came in and spent about an hour fitting me on my bike. I told him about the issues and he used the plumb line to put my knee over the crank. He moved the saddle forward about an inch and a half. Then we had a laugh at my seat that was way out in outer space. We moved that down 2+ inches. I took it out for a ride in the parking lot and it definitely felt much better. I still had the weird strain in my knees, tho it was subdued. He recommended moving the cleats aft position to the middle from my current position, outside of foot. So I did that on Sunday morning and went for a ride up in Flagstaff, AZ for the first time. The pain was completely gone. I attribute most of it due to the cleat position which had my feet to close to each other. Now that I've moved it out, my feet are more of a straight line and this doesn't produce the crazy load I had before.

The next step Sean told me was to go to 170mm cranks, which have been ordered. I'm a spinner so I'll be looking forward to the decreased circle provided by some FSA V-Drive Megaexo's. I'm always clipping things along the way with the 175's, so maybe this have a second benefit of clearing rocks too.

All told, bike fit was something I should have done a long time ago. Thanks for all your support guys/gals and here's a couple shots of Shultz Pass on Mt. Eldon in Flagstaff. The first has my correct bike height/fore/aft/size action going on.


 

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Jodiuh, glad you got it sorted out and can now enjoy your new bike. Sounds a bit like me I tend to keep my cleats more towards the inside of my shoes since I pronate outwards and have slight knock knees. If you're a spinner the 170's should help and feel better to you.
 

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Jodiuh - I did find that article however it was mostly related to road bikes, so a lot of the fits for reach and such dealt with having your hands in the drops or on the hoods and such.

Main points from that article:

For seat position - set your low pedal to follow the same angle as your seat tube (basically your seat tube and crank should line up closely), then adjust your seat until the heel of your shoe is barely keeping contact with the pedal.

For cleat position: Place your forward pedal at 3 'o clock position, then drop a plumb bob off the front of your knee. It should come down directly at the ball of your foot. If not, adjust your cleat so it does.

The above stuff I think is pretty universal, though I'm not positive. For sure, what is universal are the comments made regarding the shop where you purchased the bike. If you got the bike at a shop, call and ask about a fit for your bike (it should be included with purchase in most cases) and have them set you up. They should be willing to swap out individual parts on your new bike at no charge (for equal parts) to get you the right fit.

I did that - I picked up a new road bike a week ago for commuting, went out for a ride and had some pain. I called the shop and asked for a fit, they had me down there that afternoon. With my bike up on a trainer, they had me ride like normal and started making changes. I had my seat close - but still off, so they adjusted it up a little, adjusted the angle of the seat and adjusted the cleat position on my shoe. They noticed my reach was a bit too extended so they're going to get me a 100mm stem (I have a 110mm stem right now) and swap it out for me at no charge next week when it comes in :cool:

The following day I did a 25 mile ride with no discomfort. I could have used a bit shorter reach though, so I think the new stem will help nicely.
 
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