I’ve seen several posts on here suggesting the use of shorter cranks for low back pain issues on a tri bike. I was just curious why this would be the case? If someone riding 172.5mm cranks at a high cadence of around 100 RPM switched to 165mm cranks, wouldn’t they have to ride an even higher RPM? If not, isn’t more torque required to get them around, thus causing more strain on the back? I understand that it opens up the hip angle, but would someone that rides with out a lot of drop even realize any benefit of this? The only thing I could see is that maybe it would keep the hips from rocking as much (on a seat not too high) since each revolution requires a smaller circle? I’m at wits end getting comfortable on the bike, and willing to try anything (actually borrowed some cranks already) but wanted to understand the logic first. Thanks!
a lot of what you are wondering about will make more sense if you remember that bikes have gears on them.
someone switching from 172.5 to 165 can ride at the same cadence, in a different gear.
the crank thing is worth a try, as it saddle position fore/aft, saddle height, saddle, bar height, bar distance, etc
if your low back hurts the first things I would look at are bar height, stem length (bring it closer, your lower back doesn’t have to do as much), seat height (make sure it isn’t too high, making you rock your hips)
I’ve seen several posts on here suggesting the use of shorter cranks for low back pain issues on a tri bike. I was just curious why this would be the case? If someone riding 172.5mm cranks at a high cadence of around 100 RPM switched to 165mm cranks, wouldn’t they have to ride an even higher RPM? If not, isn’t more torque required to get them around, thus causing more strain on the back? I understand that it opens up the hip angle, but would someone that rides with out a lot of drop even realize any benefit of this? The only thing I could see is that maybe it would keep the hips from rocking as much (on a seat not too high) since each revolution requires a smaller circle? I’m at wits end getting comfortable on the bike, and willing to try anything (actually borrowed some cranks already) but wanted to understand the logic first. Thanks!