Bending rotors

[G-Tek]

So after last weekend I was giving my bike a bit of a clean up and tune and found that I was getting major brake rub on the rear wheel.

Upon close inspection it looks as if I had bent the rear rotor. Sure enough I took it off and laid it on a flat surface and yep bent. Albeit a slight bend, but enough to rub, even after trying to re-align the calipers.

This is the 3rd rotor I've bent in 18 months of riding and I'm pretty over it! So expensive to replace. I'm running Avid Elixir R's with G3 rotors. I like to push myself when I ride and crashes are inevidable riding like this I guess.

So basically I want to know if there is any way to "fix" these rotors? Two of the three are quite minor bends, one is a write off I know that. I had heard somewhere something about putting them in the oven but haven't looked into it.

Anyone got any remedies?

 

[workmx]

I have had this problem before with Avid rotors.

I fixed it using this method:

"In general, if there's something noticeably wrong with the rotor, you should replace it. That means if it's seriously worn, gouged, or bent, you're better off with a new one. You can, however, straighten a slightly-warped rotor.

To inspect the rotor, sight straight along the pads of the disk brake mechanism. Slowly spin the wheel while you watch the rotor.

Straightening a warped rotor:
The right way to true a rotor is with special tools. If you're an upper-level rider who demands precise performance from your bike, you can buy a truing gauge and drumstix.


Now here's the on-the-cheap way to do it.

1. Put the bike in a workstand and spin the wheel. Watch for side-to-side motion of the rotor compared to the brake pads.

2. Identify the warped area. Find the spot where the rotor most closely approaches one pad and mark it.

Marking where the rotor is most "untrue."


3. Rotate the wheel so the "too close" spot comes away from the brake cylinder and pads.

4. Clamp the disc in an adjustable open-end wrench. Tweak gently away from the direction of the warp, then rotate the wheel and watch for wobble. Continue gentle bending until the warp is minimised. Gently bending the rotor outward to correct warp."

 

[r.ayres1]

^^ Awesome tip mate.. Just thought i,d add - ("common sense".. make sure the shifter ( adjustable wrench ) is nice and clean..:biggrin:

 

[G-Tek]

Thanks Workmx, will give the on-the-cheap method a go tomorrow. I didn't really think that simply leaning on it with a wrench in the right spot would do much for it, happy to be proven wrong though!

As for the other method, unless I plan to keep on bending rotors regularly, I think it would be more cost effective to just buy a new one. I just really hate the waste involved though. We already throw away too much stuff.

 

[harmonix1234]

I have saved many a rotor with the old wrench method, however just the other day I had to bin my XT rotor which is only about 6 months old because it wasn't just warped but twisted as well.

sometimes it works, but sometimes they just can't be saved.

 

[3viltoast3r]

I also found some types of rotors are significantly easier to bend back into shape - I had a set of Hayes V7's, which you could bend back with your hands! Currently I have a set of XT's which are impossible to bend back, but conversely are also a lot harder to bend in transit/small crashes.

Whats size rotor is it? If it's a 7/8" rotor on the rear, you might be able to get away with dropping a rotor size.

 

[3viltoast3r]

Oh, and put a rag on the rotor before you put an adjust on it :biggrin:

 

[dhd]

Or if you want to replace the rotor for not much coin I have 203mm rotors I want to flog off real cheap! 6 bolt will work with most brakes. $20 each

 

[G-Tek]

This one that I bent was a 7'' rotor, I'm currently running 7/7 f/r and it seems to be really good. I upgraded from 6'' on the rear just to gain a tad more stopping power, not sure how much difference it made. Was running an 8'' on the front for a while too but bent that as well (big crash not suprised).

There tends to be some fairly long downhill runs amongst the tracks I ride locally to not sure if going back to a 6'' is wise.

As far as 8'' (203mm) goes, pretty sure I dont need to go that big, I'm only 65kg fully loaded!

About to go and have a crack at the wrench trick, will be sure to use a rag between it and the rotor. :biggrin:

 

[muskimo]

the other thing that could be an issue, given that this is a regular occurrence, is the 6bolt face of the hub perfectly flat?
lots of people have made comments about this issue that they cant get the rotor not to rub. maybe look at that?

 

[G-Tek]

Another good idea muskimo, I have wondered this, will check that to be sure as well.

I had a small win though, got the rotor to straighten slightly, avoiding the rub I had before.

Had some further issues pop up though, had a sticky piston that popped out a bit once I took the pads out to check them etc. Took a bit of effort with a screw driver to get it back flush where it should be so I could get the pads in.

Had it sorted (I thought) then tested the brake once back together and the lever went to the bars! It looked like I had put the pads in the opposite way to how they were orginally, they must have been wearing uneven. So I proceded to try and take them out... until I rounded the hex bolt that holds them in place. (I'm blaming a comination of user error, poor tools and soft bolt) So now I have a bolt stuck. I thought cutting it off and then drilling it through would be enough for me to remove it but no. So now I have the head of the bolt stuck in the thread. I've stopped so I dont ruin the thread. :epicfacepalm:

 

[Ryza96]

Yeah man, I bought a cheap rotor truing fork does the job every time. Yes I think we may have a hub were the disc mount surface is out of true. Gonna pull it of soon & skim it. Cheers.