Rotors bent on the bike but flat off it!

Chris5.5

Have just bought some new wheels, when I put the rotors on and tighten the bolts, the rotor becomes warped and rubs the pads for around 90 degrees of rotation.

I took the discs off and they are flat. It seems that as the bolts are tightened the rotor is pulled further in.

Does anyone know how to cure this. would it be worth sanding the anodising off around the bolt holes on the hub?

Thanks

Chris

Anonymous

are you sure the disc is properly flat when it's off the bike? It can be quite hard to see any deflection.
How much deflection is there when it's on the bike?

Have you tried re-mounting the disc, but rotating it, say, 180degrees clockwise, and seeing if the deflection is in the same place relative to the hub?

stingmered

The anodising ‘coat’ would not cause the rotor to warp - way too thin (nanometres!) to be of consideration. Added to which, this would only be a factor if the anodising was only on some of the rotor mounting positions, and not all as I’m assuming is the case. Sounds like to me you have what is technically known as a “duff” ‘un. Contact the shop and get a refund/swap.

I wouldn’t put the rotor back on the new hub again ‘just to check’ as it may cause permanent damage.

What hub is it by the way?

Anonymous

Permament damage? Are you on drugs?

Chris5.5

Thanks for the advice, will try and move it round.

The rotors are off my old wheels. I have layed them on a flat surface and they are fine all the way around.

As you tighten the rotors you can see the rotors move inwards at the tip as you tighten the bolts.

It only deflects by about 1mm, but having Juicy 5's this is enough to rub the pads.

Chris

Chris5.5

Its a Superstar Superleggera hub, if this makes any differance.

stingmered

@yeehaamcgee

because warped rotors never occur... if you took it for a test spin and got a bit of heat into it, it is more likely to warp, i.e. permanent damage caused by heating whilst under tension. i've done a fair bit on materials engineering in my time so i'd like to think i know what i'm on about.

p.s. it's too early for drugs, but only just.

Anonymous

I've seen plenty of rotors warped from new, just bad manufacturing. Trying it in a different rotation is never going to damage the hub. And besides, it might still be the hub that's badly designed.
I refuse to believe you're any good as an engineer if you jump to conclusions about what's at fault, without first analysing the conditions and eliminating possible causes.

stingmered

I was referring to the rotor being damaged not the hub.

From the original post, I was giving the guy the benefit of the doubt on the rotor, and from his decent description of the problem, it seems to me like the hub is at fault.

of course this is only my opinion/advice, and I hope it's one to throw in the mix when figuring out what the problem is.

Chris5.5

I think you could be fight on the hub, I have never noticed this on the old wheels.

Thank you both for your advice.

Chris

milfredo

If you tighten the bolts up fully moving in a circular motion you can warp the rotors.

The best way is to snug up oposite bolts at a time: i.e. 12 oclock - 6 oclock, 3 - 9, 2 - 7, 4 - 10, just so they bite, then torqe up to correct setting in the same way. This is the correct way to tighten up any circular bolt pattern accuratly and avoid warping.

nicklouse

milfredo wrote:

If you tighten the bolts up fully moving in a circular motion you can warp the rotors.

The best way is to snug up oposite bolts at a time: i.e. 12 oclock - 6 oclock, 3 - 9, 2 - 7, 4 - 10, just so they bite, then torqe up to correct setting in the same way. This is the correct way to tighten up any circular bolt pattern accuratly and avoid warping.

also make sure the mating surfaces are clean and there are no raised threads.

RupertCommunicator

Sounds like the holes on the hub are not flush to me, although rotors are notorious for being out of true.

And Stingmered. Are you on drugs?