Warped rear disc

Baron Greenback

Hi everyone,


Seems like I've managed to warp my rear disc. YouTube link below:

https://youtu.be/qpDC2vjSDsI

You might be able to see the discolouring around the outside edge of the disc. Looks like I've overheated it? I'm assuming it's not worth trying to adjust the caliper? I must admit, the video seems to exacerbate the actual noise being made.

It's a shimano item, some light research suggests I'll need a bottom bracket type tool to remove it? Are all these the same? Or can someone point me in the direction of what I need please? Also, it states 40nm on the rotor itself. So, do I need a torque wrench and socket, or, just buy a bb spanner, and tighten it by hand to something that feels about right?

It's going to work out cheaper for me to take the wheel into my local shop, however I'd like to at least evaluate what tools I'd need in case I decide to do it myself.

If I'm replacing the disc, should I replace the pads also?

Best regards,


Greenback

The Rookie

It's a cassette lockring oil not a BB tool.

40Nm is pretty darned tight, no need for a torque wrench.

Baron Greenback

The Rookie wrote:

It's a cassette lockring oil not a BB tool.

40Nm is pretty darned tight, no need for a torque wrench.

Right, I see. Many thanks for the reply. Any chance of a link please? Are there many different types?

Thanks,

Greenback

Baron Greenback

Apologies, I've just realised I put this in the road cycling section by mistake.

redvee

I use one of these from Evans

https://www.evanscycles.com/fwe-transfo ... h-EV183201

Though you can buy similar elsewhere.

The Rookie

The cassette lock ring tools are all the same, make sure it's for a cassette not a freewheel though!

kajjal

Check how worn the pads are, I would clean old pads and new rotor with disc brake cleaner to make sure

mr_evil

You don't have to remove a disc just because it's not true anymore. You can straighten it without even taking the wheel off, using nothing more than an adjustable spanner.

daniel_b

I use one of these:

Baron Greenback

Thank you for the replies everyone, really appreciate it.

This has triggered some further questions:

1. The cassette lockring tool, is it used with a ratchet? or adjustable spanner across the hex on the outside? Every photo I've found shows the tool stood up or on its side. I cant see if there is a 3/8" or 1/2" drive square attachment in the rear.

2. Shimano offer an adaptor (SM-RTAD05), to convert from centre lock to 6 x torx bolt fixing. If I was to go for this, would it open up wider options for disc choice, either for superior / more readily available / more cost effective types? This is where the bottom bracket tool is required, sorry, I read the manual to quickly yesterday (TL-FC36to fit the adaptor).

3. Thanks for the links about straightening the disc. Is this commonly done? I'm keep to know what you guys would you do if it was your bike? I cant see how I would straighten it to be true enough. I'm sure I'd be able to tweak it so it fits through the pad gap without rubbing, but that's not really the only aim here is it? or will the play in the pads accommodate a small amount of warping anyway? Is it worth removing the disc, and sitting it on a flat surface to see how warped it is? We have a granite inspection table at work that I can sit it on.

4. Is the discoloration on the outside of the disc normal?

Thanks again,

Greenback

The Rookie

I use the tool with a ratchet (1/2" drive) but you can use a spanner or adjustable.

Other adaptors are available, Ashima is nice but more expensive, I'm using a pair of Aztec, they save weight by using short steel studs to mount the disc and a thin steel plate to trap it in place and come with a lockring that is lighter than the Shimano one.

I've straightened a few discs successfully, just do it on the bike, a little at a time and spin the disc through a lightly pulled on brake to find the 'high spots'. It doesn't always work though, some will never straighten.

mr_evil

Baron Greenback wrote:

...Is this commonly done? I'm keep to know what you guys would you do if it was your bike?..

I have straightened all my rotors at least once. Sometimes because I carelessly let it rest against something, but also because even brand new rotors are never quite perfect.

If it was me, I would try truing it on the bike first.

Baron Greenback

Well, it worked a treat. Popped the bike up in a stand, and dug out a large adjustable spanner. It tweaked back into shape with relative ease.

The disc sits consistently slightly closer to one pad than the other. Not sure if that needs to be adjusted, however the disc no longer rubs at all, not until the brake lever is depressed, almost fully in.

Thanks guys!

Greenback

daniel_b

Baron Greenback wrote:

Well, it worked a treat. Popped the bike up in a stand, and dug out a large adjustable spanner. It tweaked back into shape with relative ease.

The disc sits consistently slightly closer to one pad than the other. Not sure if that needs to be adjusted, however the disc no longer rubs at all, not until the brake lever is depressed, almost fully in.

Thanks guys!

Greenback

If the disc sits closer to one side than the other, but it is straight, then you would need to loosen the calliper and adjust it's positioning on the mounting points.

I have yet to try this with Shimano, but can tell you SRAM is a very fussy bugger when it comes to calliper positioning.

My Shimano setup sounds like yours, as in one side is closer than the other, not sure whether to mess with the positioning of the callipers or not - what is the general concensus, should the disc be bang in the middle of the pads.....?
I suspect I know the answer.

coops1967

Baron Greenback wrote:

The disc sits consistently slightly closer to one pad than the other. Not sure if that needs to be adjusted, however the disc no longer rubs at all, not until the brake lever is depressed, almost fully in.

That's an easy fix - When I changed wheels I had very slight brake rub and did the following:-

Loosen the bolts holding your brake caliper just enough so the caliper can move ( you'll find the holes in the caliper bracket are slotted to allow for some inward and outward adjustment) - then apply your brake, and keep the brake lever applied either by a freind or a zip lock tywrap, velcro strap, rope or whatever.

While the brake is firmly on, retighten the caliper bolts then you can release the brakes and you should be done.

daniel_b

coops1967 wrote:

Baron Greenback wrote:

The disc sits consistently slightly closer to one pad than the other. Not sure if that needs to be adjusted, however the disc no longer rubs at all, not until the brake lever is depressed, almost fully in.

That's an easy fix - When I changed wheels I had very slight brake rub and did the following:-

Loosen the bolts holding your brake caliper just enough so the caliper can move ( you'll find the holes in the caliper bracket are slotted to allow for some inward and outward adjustment) - then apply your brake, and keep the brake lever applied either by a freind or a zip lock tywrap, velcro strap, rope or whatever.

While the brake is firmly on, retighten the caliper bolts then you can release the brakes and you should be done.

That comprehensively does not work for SRAM Rival, despite their guide showing how easy it is!
The issue being, no matter how hard I held the calliper, as I tightened the bolts, the way the bolt 'bit' as it tightened, it rotated, and moved the calliper.
I ended up using this as a starting point, and then just had to tinker with it by hand, and by eye.
It's a long process for SRAM, hopefully Shimano will work with this method.

coops1967

It was for Shimano calipers that it worked perfectly - do they not have a washer below the caliper bolt head and caliper body with Sram?
That should help... sounds a pain in the rear otherwise if tighteing up the bolt shifts things around every time.

The Rookie

Some callipers love to twist, the knack then is to nip each bolt up progressively tighter as you go, try doing one up tight and the calliper just rotates.

The pulling the brake on only works if it was aligned properly so the pads are worn straight, otherwise you realign it wrong with the worn pads.

daniel_b

coops1967 wrote:

It was for Shimano calipers that it worked perfectly - do they not have a washer below the caliper bolt head and caliper body with Sram?
That should help... sounds a pain in the rear otherwise if tighteing up the bolt shifts things around every time.

The Rookie wrote:

Some callipers love to twist, the knack then is to nip each bolt up progressively tighter as you go, try doing one up tight and the calliper just rotates.

The pulling the brake on only works if it was aligned properly so the pads are worn straight, otherwise you realign it wrong with the worn pads.

I can't quite recall the setup, but it was a bike I ordered from Evans online, anb had it delivered straight to my house.
The rear was ok, but the front rubbed.
I spent literally hours on this thing, with ever grrowing frustration, and in the end took it into Evans - it took a bloke there 40 minutes to get it sorted which gave me some sense of satisfaction.

But yes, as I think I remember, it does have washers underneath, but the issue seemed to be caused by the bolt that you tighten up, having a grippy element to it, and the issue was you had to brace against this as you tightened it, and it was almost impossible to get the element of pull right to counteract the callipers desire to push inwards if that makes sense.
Irritatingly, it also seemed to slightly change orientation when you fully tightened it up enough, like you could get the gap even, and centered, but the final tweak with the allen key would rotate the entire calliper in relation to the rotor - not sure if that is making sense, but I know what I mean!

Latterly on this bike I changed the wheels, and of course had to then start with scratch with the callipers, as they were a country mile out - I knew they would be of course!
I have gotten better at it since, and also bought one of the little brake disc guides, which did help a fair bit, but only IF you can get it in there, sometimes it can be awkward.
Cannot remember the name of it, or what it was called sadly, but some kind soul on here took pity and mentioned it, and it is basically a metal sleeve, think of it as in the shape of a bridge, which is the width of the rotor - you slide it into the mechanism, so it is sleeving the rotor, and between the pads, this then builds in the level of clearance you should need, and in theory you just tighten it up and away you go.
In reality with the SRAM's it helped, but still couldn't do the perfect job, but some tweaking afterwards fiinished the job.
I can certainly go and look at the name on the product if anyone is interested, it was only £4 or so IIRC.

Rightarmbad

The Rookie wrote:

It's a cassette lockring oil not a BB tool.

40Nm is pretty darned tight, no need for a torque wrench.

Not all centrelock use a cassette lockring type fitting.
DT in particular use a BB style tool and there are many bike brand adaptions of this.
You can however replace these with a more common cassette type if you wish.

Not all lockring tools will fit either.
There are quite a few incompatibilities around.
Some will seem to fit but not totally engage risking stripping out the ring.