Maro

Hi, this does not make sense: Two bikes similar distances one good one back pain

I have one 58cm Road Cannondale CAAD Al frame, another 58cm Fuji Touring bike.
Did a couple of brevets (200Km) on the Cannondale, a few tours on the Fuji, no problem.

Few years back I got a nice Cannondale Six Carbon. I did a mistake to listen to some advice and got 56cm. Lower back pain after 1.2 – 2 hours into the ride, and after!!
I adjusted the 56 Six Carbon, similar to the 58 Cannondale:
*Same Bottom bracket to seat distance (higher seat post )
*Same saddle tip to handle bar distance. Longer stem on the 56 (the horizontal tube is only 15mm shorter)
*Saddle to handlebar drop is almost the same in both bikes.

Same back pain, although both bikes have similar above 3 dimensions.

The only difference I see is one frame AL, one CF, and the 58cm bike has 700 x25 tires, compared to 700x23mm on the smaller bike.

To complicate the matters further, the steel Fuji touring bike, has a 50mm smaller tip of saddle to handlebar distance (520mm versus ~570mm the others), and is much more comfi.

Please help me as I do believe in logical things.

thanks

Igualmente

Some questions:

Is the saddle set-back the same on both?

Same saddle on both? Same saddle tilt?

Is the distance from saddle tip to the hoods the same on each bike?

If the answer to all of the above is "yes", or "within a couple of mm or degrees", then I have no idea. The only other thing that comes to mind is that the front end of the Super Six might be harsher (smaller tires?).

Maro

Saddle is similar, not same, although.
No tilt in both.
Saddle to hoods similar.
Setback I will have to measure. How this will make my back hurt ?

Igualmente

Saddle set-back affects the balancing of your body on the bike. If you shift the balance, you may have more weight going through your torso on one bike than the other. It may or may not be the problem, but I am looking for differences.

cruiserhead

It makes a drastic difference for me if the stem or saddle is even 5-10mm off,

different geometry means a lot of differences can account for the discomfort.

You can measure distances, but does not account for the different geometry of the frames.

Theoretically, my track and road bike should measure the same, but they don't because the geo is different.
You have to simply ballpark it w/ the comparison and then fine tune for the specific ride.

jyl

Bars and hoods tilted the same? Tilt can affect the effective reach to the hoods.

Riding same gearing and cadence?

I'd move the saddle between bikes and see if that makes a difference.

berner

I may be helpful to document the measurements that work for you. Park Tools has a handy chart for t his that can be downloaded. https://www.parktool.com/uploads/file...sitionroad.pdf