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I am in process of ordering custom bike, but one thing that makes me super unhappy is the fact all dropouts I see have threads on the right (drive) side.

Is there a way to (or there is some source, i.e. company) to have threads on the left (non-drive) side?

Answering the incoming question -- because when I change a tire I put my bike on the left side, so removing and inserting the axle will be a pain.

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  • Probably a little opinion based but would thing the primary reason is to get the cam leaver out of the way of the drive train. Not sure what sort of custom bike you're ordering but having the leaver in the way of the rear mech on for conventional bikes enough of a headache it has to be non-drive side to make it a standard
    – Hursey
    Dec 14, 2022 at 20:25
  • @Hursey I guess this was the reason to have this way, but not all thru axles have lever. So on one hand you have ease of maintenance (that's my case), on the other possibility to use axle with lever (I am all good with axle secured with allen key).
    – greenoldman
    Dec 14, 2022 at 20:28
  • explainxkcd.com/wiki/index.php/927:_Standards
    – mattnz
    Dec 14, 2022 at 20:46
  • @greenoldman, the thru-axles that don't have a lever require a tool (typically a 6 mm hex key, IME). In either case, not having to worry about interference from the drivetrain is nice.
    – Paul H
    Dec 14, 2022 at 22:49
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    @mattnz many rockshox forks have thru axles inserted from the right and threaded on the left. The only reason for the rear design (inserted from left) found on most bikes can be access around the derailleur to the axle head.
    – Noise
    Dec 15, 2022 at 13:09

2 Answers 2

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In theory, a framebuilder could machine custom dropouts to do what you want. Normally, they buy premade dropouts (which are especially helpful with disc brakes, as the dropouts come with disc mounts located perfectly). It might also be possible to adapt an existing dropout with a helicoil insert, although that seems like a hack. Some framebuilders seem more amenable to doing weird custom work than others. If a framebuilder recommended against doing something like this, I would take their advice.

Edited to add: premade through-axle dropouts typically have a thick barrel for the threaded end on one side, so the idea of adapting existing dropouts probably wouldn't work.

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    Custom dropouts aren't that hard to design - for someone with CAD skills. I designed 2 sets for a couple of bamboo bikes, using some old ones as a template to get the angles etc. Made from aluminium they can be water-jet cut from plate, steel would probably need machining. Cut the threads afterwards
    – Chris H
    Dec 15, 2022 at 10:05
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(note - answer is flawed)

Threads like to unwind if not tightened correctly - which is why pedal threads are handed.

A TA that threads in from the left side of the bike with a right hand thread could unthread itself from the frame, if the torque was low enough that a locked-up bearing could grab and have the wheel rotate the fixed axle through a high-resistance cartridge bearing.

Would you get a left-hand thread in your through-axle? If so, remember to buy a spare because it would be impossible to buy retail. Making a TA should be possible but it will increase the cost of the project, due to machining and heat-treating.

For the convenience of working from one side of the bike when changing a flat, the cost may not be justified.

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    the locked bearing argument would loosen a standard thru-axle and tighten the proposed selection so your answer is wrong on that count ....in my opinion.
    – Noise
    Dec 15, 2022 at 8:45
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    What am I missing here... 'A TA that threads in from the left side of the bike with a right hand' .. that's the standard isn't it?
    – Lamar Latrell
    Dec 15, 2022 at 9:34
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    I don't think the good old precession argument of pedal threads would apply here either.
    – gschenk
    Dec 15, 2022 at 10:42

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