Technical FAQ: Of drivetrains and dismounts

Lennard Zinn ponders the age-old question of why your chain is on the right side and finds the answer on a horse.

Dear readers,

Grab the front of the saddle as you swing your right leg over it.

I know that I promised to describe how to eliminate front brake shudder on a cyclocross bike in today’s column, but I only just got the parts today that I think will definitively eliminate it, and I didn’t have a chance to install them today, much less test them. And now it’s Thanksgiving week. So that column will be coming up the week after next.

I also got such a large number of emails about tubular gluing that I have not been able to get through all of them, but I have answered quite a few. It made the follow-up column as long as three columns should be. So I’ll hold some until next week.

So I got sidetracked a bit, when doing something other than working on or riding bikes. The other night, while dismounting from our very tall (16.2 hands) dressage horse, Luminary (Lu), I suddenly had an insight into a question I’ve received a number of times and didn’t have a good answer to, namely, why is the drivetrain always on the right side of the bicycle?

Move your right hand to the back of the saddle and put your weight on it.

I was noticing how dismounting a horse is just the same as dismounting a cyclocross bike at speed for a flat-out dismount. On the moving bike, you swing your right leg over the saddle while holding the bars, then move your right hand to the top tube, put your weight on it, and lean back. Holding yourself up by the handlebar and the top tube, you unclip from the left pedal and hang there as the bike rolls within a couple steps of the barrier and then drop to the ground.

As you can see in this sequence my daughter took of my wife dismounting from Lu, that’s the same thing you do with a horse, except, with reins in the left hand, you lean on the horse’s withers with the left and the front of the saddle with the right as you swing your right leg over the saddle, move your right hand to the back of the saddle and put your weight on it, and slide your left foot back out of the stirrup before dropping down to the ground. And the reason for releasing your left foot from the pedal or the stirrup before dismounting is the same; you don’t want your moving bike, or a horse that starts to move, to drag you along by the foot.

Slide your left foot back out of the stirrup, then drop down to the ground.

So this got me thinking of why we get on and off a bike from the left, and I realized I had always thought that we did it because the drivetrain was on the right, but it could be a case of whether the chicken came first or the egg. I am willing to bet that, since the bicycle originated at a time when a high percentage of the population rode horses, that bikes were dismounted and remounted on the left side, since that’s how it’s done with a horse. So then it would only be natural to put the bike’s drivetrain on the right, since one mounts and dismounts on the left.

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Technical writer Lennard Zinn is a frame builder (, a former U.S. national team rider and author of numerous books on bikes and bike maintenance including the pair of successful maintenance guides “Zinn and the Art of Mountain Bike Maintenance” – now available also on DVD, and “Zinn and the Art of Road Bike Maintenance,” as well as “Zinn and the Art of Triathlon Bikes” and “Zinn’s Cycling Primer: Maintenance Tips and Skill Building for Cyclists.”Zinn’s regular column is devoted to addressing readers’ technical questions about bikes, their care and feeding and how we as riders can use them as comfortably and efficiently as possible. Readers can send brief technical questions directly to Zinn. Zinn’s column appears here each Tuesday.