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Ok, seat height question...(7 posts)

Ok, seat height question...MVN
Oct 26, 2002 8:23 PM
I've been playing around with my seat height recently. I have the measurements from the LBS and they are geared more toward a touring position which is what I've gotten used to while training the past year. I want to try a position more conducive to racing. My saddle height can stand to come up a bit. What I've read says that seat height is your inseam X 0.883 and should be measured from the center of the bottom bracket. The LBS owner told me that seat height should be set from the middle of the pedal spindle in the 7 o'clock position (almost at the bottom of the stroke, leg not straight but has that 115-120 degree angle in it). My inseam is 81.0 cm, and my seat height according to LBS should be 87.3 cm (measured from center of pedal spindle), but according to web wisdom should be 71.5 cm (measured from center of BB). What it boils down to is that I'm confused. Which is correct? All answers appreciated.
re: Ok, seat height question...Juanmoretime
Oct 27, 2002 2:32 AM
Where ever your at you want your knee over the pedal axle. Colorado Cyclist has some good information on setting your position on the bike on their webisite. A method that works for me is, wearing your cyclist shorts and shoes. Sitting on the saddle flat, put one of the crank arms at the bottom of the stroke. adust the height of the seat untul you can put just your heal on your pedal while sitting pefectly flat on the saddle, do not rock to one side or the other. Now put the bike in a trainer or have a friend hold it. Clip in to your pedals and turn your cranks so they are level. Take a string with a nut or washer on it and find the little bony protrusion right below the outside of your patella. Hold the plumbline from there and adust the saddle back and forth until the plumbline lines up with the axle of your pedal. For me, this always has me very close. You may have to adjust your seat up or down a few millimeters afterward.
IMHO, KOPS, or even some variation of KOPS, is notbill
Oct 28, 2002 8:05 AM
nearly as important as saddle height. I'm sort of challenging you here, Juanmoretime, because vigorous debate is required on this all-important subject, and I want to hear from people who think that KOPS is critical.
Myself, small differences in saddle height seem very important to where and how I feel powerful through my pedal stroke, even my balance on the bike. KOPS seems a convenient myth (an intentionally inflammatory remark). I think that KOPS may have something to do with fore-aft balancing and bike fit, but I think that tolerances are broad and KOPS is way overblown.
To respond to the original poster -- I agree with everyone else that those numerical formulas are starting points with variations required for individual equipment, anatomy, and simple preference. The heel on the pedal think seems to work pretty well for me, but, in the end, it's all trial and error. Warm up and try it out; small differences can feel surprisingly different (unlike, for exampe, KOPS, IMHO).
IMHO, KOPS, or even some variation of KOPS, is notJuanmoretime
Oct 28, 2002 11:18 AM
Hi Bill, I think the importance of the KOPS has to do with a balanced position for overall efficiency. The rearset position from knee over creates a more powerful lever utilizing the quad, the ideal position for climbing, it's also more stress on the patella. The KOPS is balance of muscle recruitment, where a forward position creates a high saddle more hamstring recruitment which is the position generally preferred by multisport guys. The theory is that the legs are fresher off the bike going into the run having keep the running mucsles working. I by no means claim to be an expert. I started cycling back in the early 70's and have helped set up mostly multisport guys. I myself came from a running background into multisport and know have done from a timetrailing position on the bike to a standard road bike. Any exercise physiologist's care to weigh in?

Opinionated by not infallible.

Juan
no right or wrong...C-40
Oct 27, 2002 4:17 AM
The .883 times inseam fourmula was developed long before the days of clipless pedals. With the significant difference in the height of the various pedal, shoe and cleat combinations, this formula only provides a ballpark dimension.

Lowering the saddle will promote a higher cadence, but can produce an extreme angle at the top of the power stroke that is inefficient. Raising the saddle too much will slow cadence and produce an inefficient leg angle at the bottom of the power stroke and/or force the foot to angle down.

With my foot clipped into the pedal, I always be sure that I can drop my heel slightly below horizontal when my leg is locked out at the the bottom of the stroke. This method takes into account the thickness of your shoe, cleat and pedal. This method only provides a ballpark value as well. Fine tuning and experimentation is always required after an initial setting.

Remember that the saddle also moves forward when the saddle is lowered and backward when it is raised, by 1/3 the amount the saddle is raised or lowered. If you make a significant height adjustment, the saddle fore/aft position must be readjusted, or you will be changing your KOP position as well as saddle height. The result could be confusing.

As for KOP position, I've never had any luck with the knee set directly over the pedal, as often suggested. 1-3cm back works best for me. Further back positions enchance torque and forward positions enchance cadence. Experimentation is the key to finding the balance that produces optimum power and endurance.

To make accurate changes to saddle height, use a 6" machinist's scale to measure from the top of the seat tube clamp to some easily discernible place on the seat post. There is usually a sharp line between the tubular portion of the seatpost and the seat-rail clamp which is press fit into the post. This measurement will be much more accurate than trying to measure from the center of the crank or the pedal.
All formulas are starting pointsKerry
Oct 27, 2002 4:36 PM
The 0.883 formula was popularized by Bernard Hinault (from Cyrille Guimard) when Hinault was using Look pedals. At the time, those pedals had as much as 1 cm more "stack height" than Time (and later Speedplay) pedals. Before the advent of clipless pedals, the magic number was 109% of inseam, from pedal spindle center to saddle top. The 87.3 number you got from your shop is 108%. Any of these recommendations should be considered a starting point, not the ultimate position. There are too many variables in your crank length, cleat position, saddle fore/aft position, femur/tibia ratio, hamstring flexibility, etc. You CANNOT precisely predict seat height from body measurements.

Start with one of these recommendations, and then make small adjustments up or down, forward or back, and see how it feels after a 100+ miles. If the new position seems better, then make another small adjustment in the same direction, ride 100 miles, etc. Remember that moving the seat forward is the equivalent of lowering it as well (and vice versa).
All formulas are starting pointsFez
Oct 29, 2002 10:10 AM
"Remember that moving the seat forward is the equivalent of lowering it as well (and vice versa)."

Are you sure? I notice on modern saddles like Flite Ti, the rails are angled such that when you move it fwd, it gets a little higher, and when you move it back, it lowers.

Your statement assumes the rails are somewhat level.