Crank ratio question and seat-height
 

I'm new to fixed gear riding (5 days) and presently use a 52/18 combination, which I find allows me to get up even the steepest hill around where I live and gives me a decent speed on the flats and back down hills. Skipping to change pedal position is easy enough and skidding possible if I put enough muscle into it but I wonder if it would be easier with, say, a 49/16 combination, which gives the same gear inches as 52/18 (78). Or is the demand of back-pedalling the same as long as the gear inch figure is the same?

About seat-height, I've found that fixed-gear riding has taught me that I need the seat higher than I'm used to on geared bikes in order to use my legs on the complete rotation, particularly on the rear upwards quarter. Is it common for people to realise this when they change to fixed gear riding?

My seat is about the same height on both of my bikes. My seat is only slightly higher on my fixed gear because it has shorter cranks. Still equal height relative to the pedals
Maybe your seat is just too low on your other bike if you have trouble pulling up on the pedals.

I forgot to mention that I use toeclips on the fixed gear whereas my other bikes are all without any kind of foot-retention.

Measure your seat height from your bottom bracket to your seat rails, not from the ground to your seat rails. Track bikes generally have a higher bottom bracket (positioned higher off the ground). If the BB is 2cm higher off the ground than your other bike, then it stands to reason that your saddle should also be 2cm higher. But, if you measured from the BB to the saddle rails of both bikes, they would likely be the same.

Also, 49/16 is not close to being equal to 52/18. Every 3 tooth change in the front ring is approximately equal to 1 tooth change in the rear.

52/18, 49/17, and 46/16 are all approximately the same. The 49/16 that you mention would be a bigger gear ratio by approximately 6 gear inches which would feel significantly different.

I beg your pardon, you're right, I meant 49/17. Would that be the same as regards ease or difficulty of back pedalling?

I always measure my seat height by sitting on the bike with my heels on the pedals and setting them so that my legs are very slightly off-straight with the pedals at their lowest point. With my fixed gear, and toe clips, I find I want to sit slightly further from the pedals.

... continuing, I've just been for a ride on my Hetchins, which is without toe-clips, and realised my seat is too low. I guess I would have realised with any of my geared bikes if I'd ridden them with toe-clips but I haven't as there's been no need, riding almost exclusively in Tokyo. With fixed gear you really need toe-clips and it's quite an education. I still don't feel any need to put them on my geared bikes, though, with the exception maybe of my touring bike.

I wonder, how many people here moved to fixed wheel from geared and from not using toe-clips to using them? Or did most people here start on fixed and clipped?

The total number of teeth is irrelevant. If the gear ratio is the same, the ease of pedaling/backpedaling will be the same.

If the ratio is the same, then the difficulty backpedaling will be the same.

Maybe your seat tube angle is different between the two bikes. Or the saddle fore/aft position (which effectively changes the seat tube angle). When I move my saddle 2cm forward, I have to raise the seat post up almost 1cm to compensate.

That's what I thought but I don't trust my mechanical understanding. Thanks! (to Mihibach, too.)


I think it's simpler than that and just that riding a fixed gear and toe clips has shown me that I've always had more bend in my legs than is good for optimum pedalling efficiency. Without toe clips this escaped me as it really becomes apparent when pulling up at the back for the pedal cycle.

Thanks for the seat fore/aft effect on relative seat height point - my education continues.v:)