Seat Post Height

Burt25

I need some advice regarding my seatpost height. I recently bought a Cannondale synapse carbon which has a very specific carbon seatpost which has to be cut to size and then only has about 10mm of adjustment. I calculated the seatpost height based on the Le Mond formula which leaved the saddle only about 2cm above the handle bars. When I measure my leg angle with a goniometer its working out at 45% (I believe the optimal is about 25-30%) - So it looks like my seat could do with being a bit higher, problem is I have no adjustment left so trying to decide whether to shell out £90 on another seat post??? What should I do??

Monty Dog

Height of the bars has no bearing of the height of the saddle, so isn't a comparative measure. 45 degrees if measured correctly would be too low - suggest you get yourself a bike fit done or set-up on a normal bike before getting the hacksaw out again.

Burt25

Thank Monty- looks like a new seatpost then- I assume I could set the height up on my mountain bike - udjusting until i get a 30 degree angle and then replicate the dimension from peddle to top of saddle on the Cannondale? Should I play it safe and cut the post to set the angle at 25 initially and then shave a little more off if necessary?

defycomp2

Dependent on the length of your femur compared with your tib/fib you might not get anywhere near the "ideal" angle. I'm at 45 degrees even after a bike fit.

Burt25

I worked out that I need to go approx 45mm higher to get a 30 degree angle!! - thats 45mm more that the seat height I worked out using Le Mond formula - a massive difference. Can someone explain how the femur -tibula measurements affects things?

TOM14S

Your very toe down in that photo, level your foot out and it may be about the right length

Burt25

With foot level, measurement changes to 36 degrees (9 degree difference)

andi1363

Seat height should be 109%of inside leg measured crotch to floor in bare feet. Measure from the inside of your cycling shoe or add the sole thickness if setting from the pedal.


"© eBicycles
Diagram showing a rider's leg length measurement.
Back to Top
109% formula
Scientific tests have proven that the most efficient saddle height is 109 percent of the inside leg measurement, although obviously there are variations for individual differences. This seems to give a good combination of both maximum muscle stretch and pedalling fluidity – a win-win. To get this measurement you need to measure the length of your leg on the inside from the floor to the crotch. Do this standing and without shoes on. Multiply this length by 109 percent and that will give you the length from the top of the saddle to the extended pedal at the bottom of the stroke (with the crank lined up with the seat tube).


© eBicycles
Diagram showing the measurement that should equal 109% of a rider's leg length.
If you find your current saddle height vastly different from this formula, then make the adjustment gradually. Do note that saddle height is something you will become accustomed to."

https://www.ebicycles.com/article/deter ... dle-height

TheTallCyclist

Don't forget to include the "stack height"of your pedals+cycling shoes which can add up to additional 2cm in some cases! Stack heights of some popular pedal systems can be found here:
http://www.speedplay.com/index.cfm?fuse ... ompareroad

If you have the opportunity get a PRO fit (Specialized BG is one example). It takes out a lot of the guessing and can prevent injuries.

Enjoy your new bike!

leepez

Funnily enough I had a bike fit done last night and my seat post height was out (too high) as my measurement was 27deg. Seat post was then lowered so we obtained a result between 30 - 34deg which I was told is the most optimum and would result in using all the muscle groups in the legs.
Measurements were taken with foot parallel to the floor.

Burt25

andi1363 wrote:

Seat height should be 109%of inside leg measured crotch to floor in bare feet. Measure from the inside of your cycling shoe or add the sole thickness if setting from the pedal.


"© eBicycles
Diagram showing a rider's leg length measurement.
Back to Top
109% formula
Scientific tests have proven that the most efficient saddle height is 109 percent of the inside leg measurement, although obviously there are variations for individual differences. This seems to give a good combination of both maximum muscle stretch and pedalling fluidity – a win-win. To get this measurement you need to measure the length of your leg on the inside from the floor to the crotch. Do this standing and without shoes on. Multiply this length by 109 percent and that will give you the length from the top of the saddle to the extended pedal at the bottom of the stroke (with the crank lined up with the seat tube).


© eBicycles
Diagram showing the measurement that should equal 109% of a rider's leg length.
If you find your current saddle height vastly different from this formula, then make the adjustment gradually. Do note that saddle height is something you will become accustomed to."

https://www.ebicycles.com/article/deter ... dle-height

My saddle height is almost spot on with the 109 formula, but it gives me a knee angle of 45 degrees so I'm paranoid that its too low??

smidsy

TOM14S wrote:

Your very toe down in that photo, level your foot out and it may be about the right length

+ you have thick sole trainers on. Put your cycling shoes on and re-do measurements.

styxd

Read the following, ignore most of whats been written above.

http://www.stevehoggbikefitting.com/blo ... can-it-be/

http://www.stevehoggbikefitting.com/blo ... oad-bikes/