I'm thinking of putting my driveside crank on the left on the fixie (just because I can).

I use Shimano M540 pedals and I will obviously need to swap onto the "wrong" crank arms. Looking at the expoded diagram, it should be possible to swap out the axles so the the fixing threads are correct for the cranks… Has anyone tried this? Easy job? And will me pedals come loose when riding? Is my lockring likely to loosen?

"just becasue i can" – i can jump out the window, but I won't

yes the pedals should work if you swap the axels.

No idea what will happen to the cog though, normaly the harder you pedal the more it tries to screw itself onto the hub, then the lockring stops it it loosening when you brake.
No idea if doing the oposite is safe or not, just strikes me as an unececary risk just to be different (a bit like fixies in general i suppose!)

Simon, I've tried this myself and was told not to by various people on mtbr. They said the pedals would fall off, I thought "rubbish" and one set of knackered cranks later I'd learnt my lesson. Without a set of tandem front cranks, retapping your cranks or BMX cranks it won't work I'm afraid.

Done it on my langster, swoped the pedal axles round (the tiny ball bearings are a nightmare)! Everything else was fine, just make sure the lockring on the rear wheel is nice and tight. Never had any probs wihth it unscrewing but worth checking every few hundred miles, oh and check the pedals are tight on a regular basis cuse they are trying to unscrew themselves the whole time. 🙂

Cheers lookmanohands, you've told me all I needed to hear!

I guess I'll know straight away if the pedals are unscrewing, and I don't run brakeless so I won't die. I've rebuilt pedals like this before and, yes, the tiny balls are a right pain 😉

If it works, this'll extend my cog's life – see, there's a reason to do it 😀

I did it by accident when I rebuilt my xpedo pedals, so yes its possible.

You still got all the other problems mentioned by the others though…

Oh one more thing, make sure you get all the grease off of the pedal threads then they should stay put better! 😉

There is a high chance the pedals will unscrew themselves. There is a reason one pedal has a reverse thread. Its to stop that pedal unscrewing due to the precessional forces that the pedalling motion sets up.

Swap cranks over and both will unscrew

There is a high chance the pedals will unscrew themselves. There is a reason one pedal has a reverse thread. Its to stop that pedal unscrewing due to the precessional forces that the pedalling motion sets up.

Swap cranks over and both will unscrew

The pedal unscrewing thing can be very sudden, the moment you notice that it is loose, if it happens when you're going fast, you can destroy the cranks in a few seconds just trying to slow down. If you really want to do this, I'd use the strongest loctite (the permanent one) to fix the pedals in. I've had it a few times when learning to ride backwards – sometimes it'd hold for a few days, other times I'd crank the pedals up tight and it seemed to go loose after 50 metres of backwards riding.

Same goes for reverse threading a cog – I know quite a few people who've had track hubs fail on a unicycle, and there isn't such massive back pressure there compared to a deliberately fitted backwards cog. You're basically relying on a tiny lockring rather than a great big cog thread. People often get broken bones after lockring failures like this, it's a real sudden complete loss of power that comes as a bit of a surprise.

Joe

You could do it with a disc hub on the back – get one of those cogs that fit onto a disc brake mount – then no worries about that end.

You'd still want tandem cranks or bmx cranks to avoid your pedals breaking things though.

Joe

yep good call joe – get yourself one of these:

and it's not going anywhere.

The pedal unscrewing thing is all wrong.

Pedals will unscrew themselves (if seized) on normal crank set-ups. To check this, put a pedal spanner on, turn the cranks as normal and a few seconds later – clunk.

I once got halfway round a ride when my Time Atac seized and the pedal fell off.

The idea of reverse thread on the left crank was to stop a seized pedal on a fixie (using clips & straps) from ripping your foot off.

I admire your willingness to expend this much effort on something so staggeringly pointless. 😀

been running this setup for well over 10 months now now probs, 20 mile commute each way………just do it 😀

The pedal unscrewing thing is all wrong.

Pedals will unscrew themselves (if seized) on normal crank set-ups. To check this, put a pedal spanner on, turn the cranks as normal and a few seconds later – clunk.

I once got halfway round a ride when my Time Atac seized and the pedal fell off.

The idea of reverse thread on the left crank was to stop a seized pedal on a fixie (using clips & straps) from ripping your foot off.

No it isn't. That is just completely wrong. Please don't anyone read that post and believe it, you'll end up with broken cranks / injuries from your pedals falling off or in the worst case you might fall and damage your bike!

If the bearings are not seized (which they typically aren't), then the effect of pedalling screws the pedals in tighter. It is totally different from the situation where the bearings seize, and also different to the situation when you stick a pedal spanner on it. It is hard to understand, but it is very much the case.

Someone will always say 'the pedals will tend to unscrew themselves on normal setups'. They are just plain wrong. These are people who have never experimented with pedals on the wrong way round. Anyone who has actually tried this knows that if you switch the cranks over, the pedals unscrew when you pedal.

There is a reason that BMX people use special left-side drive cranks and hubs, and it isn't because they are really bad engineers and don't understand the situation at all, it is because when they tried doing what you're suggesting, their pedals fell off, and they didn't like the sudden fall onto the downtube that you get as this inevitably happens when you're standing up and putting a lot of power in.

I know about this from experience, because I've ridden a lot on unicycles. It is easy to fit a wheel backwards on a unicycle, leaving the cranks on the wrong side. When you do that, the pedals unscrew. Loads of people accidentally do this, and damage cranks / pedals. It's one of those things that everybody does once, and then they learn to check. The same thing happens if you learn to ride backwards – you need to keep riding forwards much more than you ride backwards, so as to tighten the pedals up again.

If you want an engineering description of why you're wrong, look on Sheldonbrown.com, he explains it – something to do with precession.

Joe

Sheldon Brown is right (as always)

Pedal Threading

Direction
The right pedal has a normal thread, but the left pedal has a left (reverse) thread.

The reason for this is not obvious: The force from bearing friction would, in fact, tend to unscrew pedals threaded in this manner. The fact is, however, that it is not the bearing friction that makes pedals unscrew themselves, but a phenomenon called "precession".

You can demonstrate this to yourself by performing a simple experiment. Hold a pencil loosely in one fist, and move the end of it in a circle. You will see that the pencil, as it rubs against the inside of your fist, rotates in the opposite direction.

Ignorant people outside the bike industry sometimes make the astonishing discovery that the way it has been done for 100 years is "wrong." "Look at these fools, they go to the trouble of using a left thread on one pedal, then the bozos go and put the left thread on the wrong side! Shows that bicycle designers have no idea what they are doing…"

Another popular theory of armchair engineers is that the threads are done this way so that, if the pedal bearing locks up, the pedal will unscrew itself instead of breaking the rider's ankle.

The left threaded left pedal was not the result of armchair theorizing, it was a solution to a real problem: people's left pedals kept unscrewing! I have read that this was invented by the Wright brothers, but I am not sure of this.

Note! The precession effect doesn't substitute for screwing your pedals in good and tight. It is very important to do so. The threads (like virtually all threads on a bicycle) should be lubricated with grease, or at least with oil.

link

Oh yeah, the other thing I know people have done in this situation (other than super-strong loctite), is weld the pedals onto the crank. Only works if cranks and pedal axles are both steel though, so probably not an option.

Joe

Wow. This is niche taken to the stupid extreme

Why on earth would you bother doing this and risk (Well, it's a bit more than risk really, it's a virtual certainty) mechanical mayhem of the highest order?
Just don't bother. Really. Don't.

I hold my hand up (but stay seated in my theoretical armchair).

I have had a pedal fall off though.