slvoid

I have a tiny and annoying warp in my brake disc, it's maybe 1-1.5mm. Not really a problem but I want it out. Any ideas?

jur

Yeah how about bending it? You are gunna have to bend it. No other way for warps to go away...

slvoid

How do I go about bending it or finding out where to bend it and how much pressure?

Moose

Find the highest point of the warped area, then line it up with the seat stay. Now apply pressure with your thumb or finger in the opposite direction of the bend using the seat stay for leverage. Start with light pressure and check your progress after each try.

Moose

oops, should've said chain stay not seat stay, the brake is mounted on the seat stay which ruins the plan.

UCSDbikeAnarchy

for a real good article on bending your disc like a pro, check out utah cycling's page at: https://www.utahmountainbiking.com/fix/diskrotortrue.htm

Al.canoe

I've been looking for those tools. I've got a cheap dial guage for checking run-out on my vehicle rotors. However, you really don't need one for bike disks. Eyeball is good enough.

I think I'll make the tools. Some Oak or White Ash might do the trick if you watch the direction of the grain. I have plenty of scraps.

Al

BostonFixed

Rotate the disc so you find the "high" spot, then true it by slightly bending it. You can use your fingers, just a little pressure, or a cresent wrench with a rag in its jaws, so as not to scratch your rotor. If you use the finger route, make sure to use alcohol or another solvent to clean any hand oils off the rotor after.

Or, if you want to splurge, morning star tools makes a set of disc brake tuning forks.

Check it:

https://morningstartools.com/drumstix.html

slvoid

Wow, I would've thought it would be more complicated than that lol.
Thanks guys, I'll give it a try tonight. I hope my fingers will still be good after 6 hours of golf.

steveknight

or just take to a good saw sahrpening place and they can true it up very well. getting a disc really flat is a bit tricky. easier if you have a surface plate for a reference.

BostonFixed

A table top, granite copunter top, book, etc will all serve as a surface plate.

steveknight

a book? that is not very flat well for a disc it may be ok I don't know how that they need to be. the best way to straighten a disc is a flat invil surface and the right hammer. but it takes a lot of skill to do it.

Moose

Yikes!!! Do not use a hammer on your bicycle disc brake!

steveknight

I did not say beat the hell out of it. but you should see the guys straighten out a saw blade. pretty amazing. then again it takes about 5 years to learn to do it.