Is any rotor too bent to bend back?

DIRTWRKS · Mar 9, 2005

Usually depends on how it's bent, most of the time I am able to bring my rotors back into pretty good shape by simply bending them in the right place with pliers etc ,however there are the odd ones that have an "S" shape or an irregular double bend in them that are much harder to get straightened out. Don't think a rubber mallet is going to get that last litttle bend out of a rotor but you can always try.

T0mo · Mar 9, 2005

downhillzeypher said:
do you think I can just beat back into true with a rubber mallet against a flat surface?

Think about it this way, are you really going to hurt anything by trying? I think a rubber mallet might be too soft.

Ciaran · Mar 9, 2005

Buy a new rotor. Sharpen the edge of the old rotor. Throw at annoying cars while commuting.

What size rotor do you need? I have an 8 " hayes rotor you can have. Used but straight.

ioscope · Mar 9, 2005

Tage Rauen
Chemistry A
3/9/05
Chromatography
Roller#5
Title: Chromatography lab

Objective: Conduct a chromatograohy experiment on water based ink.

Methods and Materials: First we prepared microwells with solutions of water, ethanol, and 1 part water 1 part ethanol as solvents. Then we placed the ends of our paper strips in the wells, and enclosed the well in a plastic bag.

Data:

Water:
Rf1: 1/14

Water/Ethanol:
Rf1: 1/13
Rf2: 7/13
Rf3: 9/13
Rf4: 11/13
Rf5:1

Ethanol:
Rf1: 1/9
Rf2: 6/9
Rf3: 1

Data analysis:

sorry,. thjis is my only file transfer facility!1

use a crescent wrench.

Steven · Mar 9, 2005

If you use a vice you can straighten them out easily.

DÃR · Mar 9, 2005

That's not too bent to fix. It might be a major pain in the ass to do, though, and your money might be better spent on a new one. At a shop rate of say $50/hr it doesn't pay to have some dude spend 45 minutes trying to get a nasty S-bend out of the thing when you can get a new one for $30.

If the shop has the Morningstar rotor truing guage it's a relatively quick and simple job; the guage measures and can correct runout to .001" which is as true as a new one.

If you're going to do it yourself, a rubber mallet will be about as useful as a toenail clipper. Leave the thing on the bike, and take two small-ish adjustable wrenches (the kind with smooth jaws, NOT pliers, vise-grips, channellocks, etc) and bend it back, using the brake pads as a reference guide. You have to bend it pretty far in the opposite direction of the bend in order for it to work.

ChainWhip · Mar 9, 2005

Somebody recommended these recently for your exact problem:

http://www.morningstartools.com/products_index.html

DRUMSTIX:

R2.o.c. TECH:

**EDIT** Looks like DBR beat me to it... I was busy looking for pictures and site information.

Mr Tiles · Mar 9, 2005

my buddy booger bent his front rotor 45^ and took it back to the shop and bent it back straight. The front wheel wouldn't even move. It's been at least a year ago and I'm thinking he's still running that same rotor.

lovebunny · Mar 9, 2005

i just use vice grips w/ a towel between the grips and the rotor and bend it on the ground. and you can tell when its straight by laying it on a flat suface and putting pressure in certain areas.

CChase86 · Mar 9, 2005

The key with bending rotors back is that metal has a memory so you have to bend it back farther than it is bent (in the opposite direction).

Mike B. · Mar 9, 2005

Like someone else mentioned, crescent wrenches work rather well. I've set up a dial indicator on a Park truing stand to verify the runout. Also, like CChase said, the stainless does have pretty significant spring back at the ~.080 thickness of the rotor, you'll figure it out pretty quick I'm sure.

mack · Mar 9, 2005

CChase86 said:
The key with bending rotors back is that metal has a memory so you have to bend it back farther than it is bent (in the opposite direction).

DITO

But i have always wondered how they get bent in the first place. :think:

mack · Mar 9, 2005

Yeah, but what bends them to begin with? I dont hit anything with them, and my calipers are even.

OGRipper · Mar 9, 2005

Yeah that little variation is definitely fixable. The shop sounds lame. Sometimes a shop won't want to do it because it's hard to get 'em perfect but still, it's not hard to get a rotor straight enough to pass through without rubbing. The morningstar drumstix work great, I've got some older chainring straighteners that work well too. If you don't have gauge, keep the wheel on the bike and use the brake as reference. When you spin the wheel try to see if the thing is bent near the braking track or lower, near the hub, and try to fix it where it's bent, you don't want to bend it anywhere else...I don't know anyone that has had luck fixing minor variations like that by trying to pound it flat...

DIRTWRKS · Mar 9, 2005

mack said:
DITO

But i have always wondered how they get bent in the first place.

Try crashing during a DH run and then it sort of depends on how the bike goes down and wether or not the rotor catches a rock etc.............

Ciaran · Mar 9, 2005

downhillzeypher said:
hell yeah dude... Are you gonna be at the southridge this weekend?

Not Saturday, but maybe sunday just to check it out. I am either working or riding (if I am lucky) on saturday. I will PM you if I am going so we can hook up there. I really should since other monkeys will be there too. Gotta meet some of y'all.

Alternately, if you are close I can meet you somewhere, I can mail it to you, or you can come pick it up. I am in Pasadena. I am going to shoot for going to Southridge though. I'll PM you and let you know.

mack · Mar 9, 2005

DIRTWRKS said:
Try crashing during a DH run and then it sort of depends on how the bike goes down and wether or not the rotor catches a rock etc.............

I never crash

... i wish

prerogative · Mar 9, 2005

Above info works in most cases - wrenches and all, and I'd start with that. I found a good way to fine tune it to flat that worked good: Put on flat surface (glass or Al plate), and mark all high spots with sharpie. Do this on both sides. Place rotor on a soft wood board (plywood works), and on cement floor. Hit high spots (both sides) with hammer. Like stated above, you have to go beyond straight so it holds position, so don't be gentle. Repeat whole processes to get it right if needed.

I'm not sure it's really worth the time spent, but the satisfaction is great - who said you can't flatten this sucker.

Is any rotor too bent to bend back?

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