Bike Fit and Knee Pain

mf-racing

Hi guys,

Wonder if you can help. I having some knee problems since I got my new Trek EX Fuel 9, I’m getting a pain in the back on my knee on my left leg only. It more pronounced when I’m pulling up when pedalling (using SPD’s)

It feels like my legs are too far forward, a bit like I’m riding a cruiser bike! From looking round it seems the best fit is to have your knee joint in line with the crank axle, for me to get this I have to have my saddle rails pretty much all the way forward and it looks well wrong!

I’m having trouble finding a good seat height as well due to the rear suspension sagging (set up at 25% static sag), also when I have my seat high (which feels right) I’m so far back (because of the angle of the seat tube) that it feels like a cruiser even more, and it makes my feat pedal at a upward angel (i.e. not flat on the pedal).

What can I do? The bike frame size is perfect, just feels like the seat tube angle is too steep and it need a inch chopping from the top tube!

What’s the best way at setting the saddle height on a full suspension bike?

How can I move my knee more towards inline with the crank axle?

Cheers
Matt

paulf2007

setting the saddle height is the same as on a hardtail as the front triangle includes seat tube and bottom bracket. Sit on the saddle ( obviously) and put your heel on the pedal when your leg is almost straight that's the height you want. If your knee hurts when pulling up on the pedal...............don't do it.

mf-racing

Cheers, i never thought of that! The saddle height to BB ratio is always the same what ever the rear suspension is doing. So if the rear shock sags that does not alter leg length?

I'm dumb sometimes! :oops:

mf-racing

I take the that rear sag will affect saddle angle though? Should I angle the seat forward a bit?

So, whats the best way of delaing with this knee pain? It happens all of the time, just worst when pulling up.

Cheers

outasight

<it seems the best fit is to have your knee joint in line with the crank axle

Are you aligning your knee with the crank bolt - that is, the centre of the chain rings? If so, you would be sitting way too far back, which might explain the problems.

With the right pedal at 3 o'clock (horizontal, facing forward, parallel with the top tube) your knee should be over the pedal axle. So if you dropped a plumb line from your knee it would touch the centre of the pedal, where the ball of your foot sits. (See the saddle Fore/Aft info on: http://www.edinburghbicycle.com/comms/s ... .htm#frame

I would guess the knee pain is as a result of sitting too far back. Ditto the upward angle of your foot on the pedals.

mf-racing

Thanks very much guys!

I've now put my saddle to line up with my knee and pedal and it's much, much better! I've also put the seat higher and now feels perfect in the seating department! Fully tested round Dalby red this weekend.

I do feel like there is a bit too much weight on my hands though?! Maybe thinking of lowering the stem a bit down the steerer tube? What do you think?

Cheers

artillerydave

another angle may be an in line rather than layback seatpost, this helps to shift you weight forward and effectively shortens the top tube reach. worth a try.

outasight

I do feel like there is a bit too much weight on my hands though?! Maybe thinking of lowering the stem a bit down the steerer tube? What do you think?

I would stick with it for a few more rides and see whether you get used to the new riding position. Moving your seat forwards and up will have thrown more weight onto your hands/the bars and that is likely to feel a bit weird to begin with, especially as you were sitting so far back before.

Lowering the stem/dropping the bars is more likely to pitch you even further forward and put even more weight on the bars, especially when you're headed downhill. If anything, you might want to raise the stem/bars for a more upright riding position that pushes your centre of gravity backwards on the bike, reducing the weight on the front.

Do you move about much on the bike? On the downs, when you're most likely to notice the weight on your hands, make sure you are shifting back on the saddle to keep your weight centred on the bike.

320DMsport

I had knee trouble when setting my EX9, infact it's taken me months to get comfy on long rides.

In the end i ditched the stock saddle for a SDG and set the rails so my knee is inline with the crank pedal as said, it was suggested to use a spirit level to set the seat angle level, but i run mine slightly down to the front as it hurts my knackers when climbing.

My biggest thing that was my problem was cleat set up, this is what was giving me my knee prob, plus seat abit low but all sorted now.

To stop sag when doing XC i run mine in Pro pedal position with it set on 2, that way i'm not bouncing around and only open it for DH sections, there is still enough suspension when on Pro pedal.

I run the front at 110 for XC and open and put it to 130 for DH, i only use the 90mm drop on climbs and road climbs i lock it out.

Everyone to there own but i've been messing around with my EX9 for months and that's what i seem to get the best from it.

Good luck with your set up etc.