Unanswered Straightening disc rotors

[dobbyhasfriends]

Guide RE brakes, standard rotors. On a recent ride with a very long steep downhill I burned up the brakes a fair bit and the rear disc blued and warped, I straightened it and have ridden it since but its still blue in placs and it warped again when riding..
are these discs shagged after they get too hot?

 

[Mcharza]

Unfortunately, if the brake disc is burnt and blue, it will no longer be good. Going to buy a new one is the only solution.

 

[Mcharza]

Never heard this.....EVER! With super bikes blueing it’s a normal thing! A disks color just tells you the disk reached a certain temp so good on you but try to not let them get so hot again. You can take 2000 grit sand paper and if it’s overly smoothed out (usually from some organic pads) you could resurface it. But realistically just put some sinistered pads on and it’ll work it all out after you burn them in.

Yes, it's your opinion, but..blue and burnt is a different story.

Tried many times after the Alps trip to grind the disk with sandpaper. Yes it works, but not anymore as a good powerful brake.
But of course there is different needs.

 

[dobbyhasfriends]

Never heard this.....EVER! With super bikes blueing it’s a normal thing! A disks color just tells you the disk reached a certain temp so good on you but try to not let them get so hot again. You can take 2000 grit sand paper and if it’s overly smoothed out (usually from some organic pads) you could resurface it. But realistically just put some sinistered pads on and it’ll work it all out after you burn them in.

As for bent rotors, the theory I’ve heard is if they warp due to heat they’ll never be good again there’s a couple culprits both are not fixable as when the disk heats up again it’ll go back to that shape. If you bend one you can bend it back but when they warp from heat the only way to realign the molecules so that the rotor is straight again is extreme heat and cooling which we can’t do. If you send a new one in to a cryo shop and get it treated it just may last for ever.

For your future planning Dobby I’d say 1. make sure your pistons are not seized up and 2. Look in to getting larger rotors!!! Also you may need to bleed the brakes. If they got that hot likely you boiled them and now there’s air in them.

cheers @BAMBAMODA , I did in the end get the rotor lined up nicely again, the pistons are working properly etc as I do maintain the brakes pretty well. its only the second time ive ever done that, I was stuck behind someone on a long fast grassy descent, I couldnt get by and they weighed at least half of what I do so I think bluing discs isnt an issue for them
I have some sintered pads and its getting to that time of year so thanks for the tip, ill bang em on.

 

[Slowroller]

I cook rotors all the time, just ignore it and ride. They'll recook and sort of straighten out again. I only true rotors if they get bent in shipping or something.

 

[RickBullotta]

Guide RE brakes, standard rotors. On a recent ride with a very long steep downhill I burned up the brakes a fair bit and the rear disc blued and warped, I straightened it and have ridden it since but its still blue in placs and it warped again when riding..
are these discs shagged after they get too hot?

203's on both ends? Maybe go with 220's?

 

[dobbyhasfriends]

203's on both ends? Maybe go with 220's?

yea im considering that but the cost ! (along with all the other costs)

 

[dobbyhasfriends]

I cook rotors all the time, just ignore it and ride. They'll recook and sort of straighten out again. I only true rotors if they get bent in shipping or something.

wow really, mine were so bad that when the bike was in a stand and I ran the wheel, I would get about 3 revolutions before the rub brought it to a stop.. I did straighten it in the end and a couple of rides later when it had some more heat in it.. all good now

 

[GrandesRoues]

Shimano Ice Tec for consistency in the Alps

 

[dobbyhasfriends]

Shimano Ice Tec for consistency in the Alps

aren't they all centre lock?

 

[fenwick458]

I used to cook my old guide 180's quite often. truing them was tedious and I never got it right, and it seemed the more you do it, the easier they warped. the next time. I went through 4 discs on that bike, In the end just bought different discs which lasted much better, I can't remember the exact make and model but they were cheap and still just a single disc, one material, nothing fancy like a shimano ice tech with cooling fins or exotic materials. so I put it down to the SRAM centreline discs being crap!

 

[dobbyhasfriends]

I used to cook my old guide 180's quite often. truing them was tedious and I never got it right, and it seemed the more you do it, the easier they warped. the next time. I went through 4 discs on that bike, In the end just bought different discs which lasted much better, I can't remember the exact make and model but they were cheap and still just a single disc, one material, nothing fancy like a shimano ice tech with cooling fins or exotic materials. so I put it down to the SRAM centreline discs being crap!

I had hope E4's on my last bike, blued them but the rotor never warped.. perhaps thats the answer ?

 

[2WheelsNot4]

You can straighten warped rotors to some degree using a shifting spanner set close. Or buy a park truing spanner thingy, but its basically the same.

 

[Akiwi]

yea im considering that but the cost ! (along with all the other costs)

I just went 120 on my Magura MT7's.
I got the 220 Floating disc for €46 and the adapter to move the calliper was €8.99 so the costs aren't too bad when you consider what many parts cost. and it is something that is pretty necessary. I also replaced the pads at the same time as the old ones were done.