MiloFrance

Evening all. Anyone have any tips on straightening bent pedals? I have several pairs, don't want to bin them, can't get comfy riding them...

SJX426 

No. Ever try to straighten a coat hanger? Did they bend while you were using them? If so, they will likely return to the same condition.

If not, you could take a chance with the following approach:

the assumption is that the bend is either toward the crank arm(hit the road while cornering) or the other direction. You need to determine the bend direction to move it in the opposite direction.

Find a steel crank arm that has the same threads. If both pedals axles need to be "adjusted", you will need both sides.

Mount only the axle to the crank arm. Place the crank arm in a vice as close to the pedal with enough clearance to allow you to be able to leverage the axle.

The bend is likely between the threads and the first bearing surface at the smallest diameter of the shaft between those two locations.

find a pipe with an inside diameter that will allow you to slip it over the axle to the point were the bend is.

Make sure it is long enough to be able to easily apply force. Apply force slowly with small incremental changes until straight. Use a square between the crank and the center line of the axle.

Don't know if this would work but this is an approach. Good luck! Looking forward to reading what other brave soles suggest other than replacing the axle.

repechage

I would not trust one even if you were able to realign one.

Some Lyotard pedals have a reputation for failing even without trauma.
Campagnolo pedal axles can be purchased by themselves.

ramzilla

If the pedal shaft is bent then you need to discard it. Once steel reaches it's yield point (bent) it loses most all of it's strength. Every engineer knows this. Sorry but, those pedals are a disaster just waiting to happen.

MiloFrance

Thanks Ramzilla, but there are far more variables than that. I am an engineer.

LeicaLad 

Yes, but if you've ever had a pedal suddenly snap as you're mashing up a hill. . , trust me, you would not ride such pedals. period.

A good engineer should know that, too. Not to be snide, I only mean that safety really suggests you retire/decommission those pedals.

busdriver1959

I'm not an engineer but there must be more variables. How do fork blades get their curve without losing all their strength? I'm not trying to be a troll here. Really want to know.

SJX426 

@busdriver1959 - The answer to your question is all about material composition, physical configuration (shape), manufacturing process and the resulting mechanical properties.

It is not a given that once steel is bent that it becomes "weaker." More often than not, it becomes stronger but will fail sooner. If you take a piece of sheet metal that you can bend with your hands, you will notice that as you bend it back and forth, the material may actually become some what wavy. The reason is that the first bend becomes "work hardened" and stronger than the rest of the material, so the material bends at a different location. With repeated work hardening as a result of deformation, the material changes its crystalline structure resulting in it being "brittle" prior to failing.

Without knowing the material composition, etc. any answer is speculation as to the results of trying to bend the axle shaft back. There is risk in everything we do, bending an axle back, bending the forks both initially and in repair or riding in traffic.

Again, the mechanical properties of the steel are impacted by the stress and strain it is exposed to. We didn't even talk about the impact of temperature.

In the case of the fork bends, they don't loose all their strength.

Bike tinker man

Considering the pedal shaft is steel & I assume the crank arms you are screwing it into is alloy, I would as above just throw them out, a pedal comes adrift whilst you are pedaling you can pull leg muscles with the sudden release.

SJX426 

In all fairness, the question was how to straighten them, not what to do with them, likelihood of failure or what might happen if they fail.

repechage

True enough. once the pedals get straightened the probability greatly increases that they get used again. I really think that is unwise.

rootboy 

Metal fatigue. Not something to be taken lightly in a component used to transfer power to a drive train.
Especially if the component fails, and you run the risk of castrating yourself.

Salamandrine 

Mechanic here. I won't argue engineering.

They are pretty difficult to straighten. Best I've could ever do was straighter than they were before. It's generally not worth the trouble.

Anyhow, don't try to do it on the crank arms unless it's a really cheap bike you don't care about. You are more likely to bend the crank arm then the pedal shaft. *

Best case: disassemble the pedals, screw the axle into a big chunk of steel that is tapped to take the pedal. Put that into a huge vise, and straighten the axle with a heavy pipe. (of course most people would use an old steel crank arm instead of a custom chunk of steel)

*BTW, sometimes it's the crankarm that is bent, not the pedal.

CroMo Mike 

A competent machine shop could straighten them but the cost would make buying new a better option. As a home machinist I chucked several different good condition pedals in the lathe and found they weren't real straight anyway.

dnbdonaldson

It actually gets stronger when bent but also more brittle (cold worked). More likely to shear b/c it is brittle.

Steel Charlie

Bin them. Pedals are cheap. Life is too short to putz around with such an easily replaced POS that was obviously poor quality to begin with.
Not to mention bent pedal shafts will eat your ankles and knees.

scarlson 

Such zombie
Very resurrect
Much dogpile

I've straightened pedals before. Within reason it's fine. Some vintage pedal axles are quite soft and amenable to all sorts of massaging with minimal loss in durability. I like to use something that spins the axle so I can see what direction the wobble is in. A drill chuck or a lathe or a milling machine. One reason to do it is if you have a pedal that's impossible to get a replacement for, such as the '50s Dural Bramptons whose axles I fixed.

oneclick 

Bending - as in making a permanent bend - is NOT "fatigue".

Engineers (as well as some people who are NOT engineers) know this.

SurferRosa

What is a pedal "shaft"?

zandoval 

It's possible but...

And you know this... Ha

repechage

and you could probably Make replacements given enough time.

I think the trick for a repair would be to replicate the heat treat.
performing a Rockwell hardness test would provide an indication to the extent of the original part.
the Lyotard 460? Pedals with the stepped, axle, spindle, shaft, your choice of name, are the parts I have seen enough of to at least be wary of. Most of these parts are now pretty old, age is not the issue but abuse in service. The abrupt steps in diameter are not the most low risk design.

I am conservative and gravity storm averse.

ramzilla

A bent pedal shaft is fine as long as your going downhill or cruising along a flat road with the wind at your back. But, soon as you climb out of the saddle in order to climb a steep hill watch out. That's when the shaft will snap off and, probably result in a nasty injury.

Without destructive testing how would we ever know...............................RAMZILLA