Sciatic pain on one bike but not the others

[yashicamat]

I have recently linked my slight sciatic pain to only appear after riding my single speed bike. It doesn't appear when I have cycled either my touring bike or my mountain bike.

What do you reckon the problem could be caused by? These are the things I can think of;

- Saddle: The saddle on the SS is quite narrow and hard, compared to the Brooks on the tourer and a fairly wide/soft saddle on the MTB

- Posture: The tourer and the MTB both have relatively upright postures compared to a much lower down, racing type position on the SS

- Grinding: The SS has a 74" gear so there is plenty of grinding when I am riding it, unlike the other two that both have 27 gears

Both the touring bike and the SS have SPDs so I don't think it's those either.

Any thoughts? Cheers.

 

[MacB]

well you can test a couple of them easily, try a Brooks on your SS and also try an easier gear. If the pain persists then it's posture....simples

 

[ASC1951]

May be an obvious question, but are all the bikes set up the same? In particular, is the saddle height - to the top of the saddle - the same?

 

[Ian H]

I get twinges when I'm training. A combination of bigger gears and lower bars seem to be the cause. Back exercises help - sit-ups, raising the shoulders from a prone position (whatever that's called), etc.
If you're grinding a lot of the time in a 74" gear then it's too high. I ride 64" and don't get dropped.