SahuaritaDon

My current bike is a 61 cm Fuji Roubaix. It fits me well except for one parameter, ie my knees are about 4 cm in front of the pedal center in the 3/9 o’clock pedaling position. This is with the seat adjusted all the way to the rear. I don’t have a feel for how important this parameter is but I want to buy a new carbon frame bike and want to make sure it fits perfectly.

In looking at new bike geometries, it appears no one parameter affects where your knee is going to be but it seems to me that the critical distance is the TOP TUBE LENGTH minus the REACH. In my bike it is 183.4 mm. If that is correct, I need my new bike to have that measurement to be ~223 mm. I assumed this would be done by reducing the seat tube angle. (My current bike has a 72.5 degree seat tube angle). I have looked at a lot of new bike geometries and have not found anything near that.

My local bike shop was not a lot of help. They said I could:
1. Buy a new angled seat tube to get the seat farther to the rear but they did not recommend this. Did not say why.
2. Buy a custom frame.
3. Maybe move to a larger size such as 63 or 65 cm.

I can not afford a custom frame and when I look at larger sizes, I get a little more distance such as maybe 6 mm more but that’s a long ways from the 40 mm I need. Does anyone see something I have missed or have any ideas? Thanx in advance.

Dave Cutter

Don't Let the Perfect Be the Enemy of the good (or the done).

One might never complete a task if one has decided not to stop until it is perfect: completing the project well is made impossible by striving to complete it perfectly.

Ride the bikes at the bicycle shops. Go by how they feel... not by how they measure.

Jean_TX

I don't have any specific recommendations for you, except that maybe you should check out the two articles below that discuss the Knee-Over-Pedal "standard" :

The Myth of K.O.P.S.

https://www.stevehoggbikefitting.com...or-road-bikes/

Wildwood 

Getting your knee directly over pedal has never been a gold standard.
It IS a good starting point.
It is likely a goal of most custom builders to get a good overall fit and knee close to being directly over pedal. But riding style has a lot to do with it. Moving forward on the saddle during aggressive riding will certainly move the knee forward and that shouldn't be an issue.
would also agree with @Dave Cutter that riding and feeling the right frame size is better than debating measurements.

If your LBS is unhelpful or cannot fit you, please don't buy from them. A good bike shop will make your enjoyment easier. A poor one = wastes you time & $$$.

Leisesturm

There is truth in all of the posts preceding mine but I am putting it out there that... it is possible, in this instance, that the o.p. has mismeasured the critical dimension. It sounds very wrong to me that a 72.5 seat tube angle could be so off as to result in a 4 cm (~2"?) ahead of KOPS. Re-reading I notice that nowhere in the o.p. is the o.p.'s height or inseam provided. I think its relevant. Seat may be too low for one thing. FWIW.

H

SahuaritaDon

Thanks to all who responded with the great replies. But you, Leisesturm hit the nail on the head. My height is 6' and my cycling inseam is 91.5 cm. My seat height is set low as it was set just for the thigh to calf angle at full extension. It never occurred to me that raising the seat would draw the knees back (DUH!) Of course raising the seat will straight my leg too much at full extension but that is probably because my bike is too big at 61 cm. (I bought it from an individual and have never been thru a proper fitting). The proper size for me according to the height charts is 58 cm. I think buying a 58 and getting a proper fitting will solve the problem. Thanks again.

Carbonfiberboy 

Set your saddle height by the heel-on-pedal method. Put the bike near a wall or something so that you can mount the bike and hold yourself upright with one hand. Get into your usual riding position with the other hand. Unclip one foot and put that heel on the pedal. Pedal backwards slowly. At bottom dead center, your knee should completely lock out with no pedal pressure and without your hips rocking at all. Some people prefer a small gap between heel and pedal, say 4mm. Set your saddle height to make that true. Then test the other leg. Some people have legs of different lengths. I go by the shorter leg. Once you get the dialed, take the bike out on a no-traffic road and repeat the test with each foot while pedaling slowly with heel on pedal.

Once you have that set, put your hands on the hoods and with your back straight, bend your elbows until your forearms are horizontal. Your elbows should be a little in front of your knees at 3 o'clock, no overlap, and the gap less than 2". If that's not true, adjust your stem length to get it closer. You may not need a new bike at all.

Wildwood 

you have long legs for a 6' person, a 61cm frame should fit; but i understand the trend toward smaller frames.

CliffordK

What is your crank length? Lots of debate about crank lengths, but if you have long legs... you could probably use at least a 175, or maybe a 180. That will also move the pedals forward just slightly

There are lots of adjustments possible. For example not all seatposts have the same setback.

SahuaritaDon

This morning I did the saddle height setting procedure you sent me and it raised my saddle about 4 cm which is a lot. I then took a ride and it felt different, as it should, but I had more power and went faster. Thanks a bunch.

SahuaritaDon

Crank length is 175. I eyeballed the KOTP and it looked right on after I raised the seat.

Kevindale

It sounds like you're on the right track, but if you decide to go ahead and get a new bike, get a fitting done before you buy your new bike. You'll either find that you really can adjust your current bike just so, and no need for spending further $$, or you know what size and geometry you should be looking for.

fietsbob

you get a new frame with a shallower seat tube angle*, or a seat post with much more set back .

*it may not be something off the shelf.. a "Brand"

(Velo News writer) Lennard Zinn in Colorado specializes in tall peoples custom bikes..





...

pakossa

Once you have that set, put your hands on the hoods and with your back straight, bend your elbows until your forearms are horizontal. Your elbows should be a little in front of your knees at 3 o'clock, no overlap, and the gap less than 2". If that's not true, adjust your stem length to get it closer. You may not need a new bike at all.[/QUOTE]


Is this another one of those "starting point" rules, or is it more definitive? I checked my fit, and found somewhat of an overlap (assuming I'm doing it correctly, and that you're referring to the vertical plane -- see photo). I arrived at this reach by going as long as I can with the reach while still being able to pedal at "full power." (If I increase the reach just a cm, or 2, my power drops at least 20%. I assume this is due to my ridiculously short torso-to-leg ratio.) Or, could that mean my saddle position isn't quite right?SANY0762.jpg

Carbonfiberboy 

Note that your upper arms do not make a 90° angle with your torso. They should. I would increase reach until they did. I don't believe you about the 20% power drop with increased reach. I doubt it would make the slightest difference. The only difference really is in long distance comfort. Without that 90° angle, you're always using muscles in your arms and torso which don't need to be used. Over many hours that begins to tell on you.

Re saddle position: Only you can tell if you feel balanced on the bike. I don't think it's possible to see that from a photo.

In general, you want it to look like this in terms of pedaling, fit, and balance:

sumgy

Whose bike is that?
Looks seriously too small.

Bike fit for dummies:

Get pedal in correct position: BEHIND ball of foot. Often this is cleats slammed all the way back.
Get saddle height in correct position: while pedalling in a slightly bigger gear than needed pedal up a hill. The pedal stroke needs to feel circular rather than up and down and there should be no "snapping"/sudden acceleration of the knee. Keep lowering it until it feels awkward then raise again until it starts snapping.
Get saddle setback right: you should not feel like you are using your quads or hamstrings more than the other.
If you feel your hamstrings then move the saddle forward. If you feel your quads then move the saddle back.

When reaching for the bars you should not feel pressure through your back or neck.

Ali89

If you're into a 1980s retro thing.

from 2:53 for a close up.

pakossa

Note that your upper arms do not make a 90° angle with your torso. (SNIP)

Yes, but isn't that 90-degree rule when your arms are in the normal riding position (slightly bent), rather than with the forearms horizontal like that?

Carbonfiberboy 

IME and oddly enough, it works for all seated positions if fit, posture, and reach are correct. Check it in a mirror and/or watch the model in the video I posted. You may see slight variations, but close enough.

berner

This observation I think is correct. I once did an accurate scale drawing of a bike with a stick figure of my own proportions. Oddly, I found that the appearance on the bike, generally looked the same wherever the stick figure gripped the bars.