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Discussion Starter · #1 ·
Recently (within the last 1500 miles) I have noticed my rear brake disc may be warped.

When riding at low speed (Below 10 mph), you can hear the disc/ calliper 'squeak', at the same point in each rotation of the wheel. (When the tyre valve is at the bottom of the rotation), and when riding VERY slowly, as in MOD 2, (Slipping the clutch, and constantly using rear brake), you can feel the bike almost 'lurching' forwards, every time the wheel rotates.

I would imagine it has been like that for some time, as the bike has gone through a set of rear pads in less than 4000 miles. You can also see a build-up of brake dust on a bit of the disc (the bit that should be in contact with the pads), which would suggest that this area does not get used, as it is 'bent'.

Also, when the bike is on my ABBA stand, I can place my finger so that half of my 'fingerprint area' is on the back of the pad, and the other half on the calliper mounting bracket. As I rotate the wheel, you can feel the pad moving in and out.

Firstly, I was wondering if this would affect the M.O.T, as the wheels need to rotate freely. The wheel still rotates fairly freely, but not as freely as when I compress the piston so that the pads are out the way of the disc.

Secondly, would this be covered under warranty from Yamaha? I am like the third or fourth owner of the bike, and it is a late 2009 model, with just over 5300 miles, but it must have been wrong for a long time, as like I say, it went through a set of pads in under 4000 miles, and I don't really use the rear brake that much/ heavily. I might phone up Yamaha and see what they say.

Finally, could it even be as bad as a bent wheel or something? (if it is, I will just put up with it! lol)

Benji, I'm sure you will be able to help me out here!
 

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Have you simply tried looking along the disk edge on to visually see if it looks bent?
Does sound it...
 

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Discussion Starter · #3 ·
I can't really look at it, because the tyre 'stick out' too much (if you know what I mean).
 

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R125 Rob said:
I can't really look at it, because the tyre 'stick out' too much (if you know what I mean).
At work truing wheels without rim brakes I use a cable tie and cut off so it near the rim. Tie a cable tie so that you can put it near disc and then spin your wheel and you will see the disc rotor moving away from the cable tie, or not.

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Discussion Starter · #5 ·
At work truing wheels without rim brakes I use a cable tie and cut off so it near the rim. Tie a cable tie so that you can put it near disc and then spin your wheel and you will see the disc rotor moving away from the cable tie, or not.

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Don't really need to mate, something is deffinatley bent!
Just wheter it's the wheel or the disc?

would this be covered under warrenty?
 

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Don't really need to mate, something is deffinatley bent!
Just wheter it's the wheel or the disc?

would this be covered under warrenty?
If it where me i would check rotor first and if bent just straighten it... could save you a lot of time and yamaha agro.
 

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Depends how badly the disc is warped, a small amount of runout is acceptable (0.15mm according to the service manual), this is taken up by the sliders in the caliper, anything more than that, it's new disc time. To check it, ideally use a dial gauge, then set it against the disc, set it to 0, then rotate the wheel, noting the biggest deflection in either direction, add them together and that will give you the runout.

To warp a disc, it's usually getting too much heat, from either sticky caliper pistons, caliper slides, old brake lines or pads stuck in the carrier. Or it can be rider error, trailing the back brake everywhere, sometimes not realising they are doing it by having large feet, that are catching on the brake pedal.

As for straightening a warped disc, I'm curious to how you think you are going to do this to the accuracy required? Once it's got to this point, it's only really fit for the scrap bin.
 

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If it is warped bin it don’t waste your time trying to straighten it, you won’t.

Heat will have distorted it and changed its structure. The only way to reverse this will be with heat treatment and cost more than a replacement unit. Also have you adjusted your chain recently, check your wheel alignment this could have been a contributing factor to the initial heat generation.
 

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you have an abba stand, just take the wheel off and take the disc off, nothing to hard to do, then place it on a flat surface, then youll know if its warped or not, much easier than getting a digital gauge or what not :p does sound like its warped though, think mine was too before i got my wavey rear disc :)
 

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Discussion Starter · #10 ·

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Rob the pads you have you can still use it after you place the new discs on your bike.You don't have to change it.If you see difference on the brake you have to
use harder pads.
 

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Discussion Starter · #12 ·
Rob the pads you have you can still use it after you place the new discs on your bike.You don't have to change it.If you see difference on the brake you have to
use harder pads.
OK, thanks for the advice!
 

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Sorry, got to disagree with using old pads on new discs, this is bad practice, as the current pads have worn to the old disc, by introducing old pads to new disc, you start a premature wear pattern on the new disc. Get cars in at work, were people have done this, and it's a very false economy.
 

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Got to agree with Benji here, even if they have only done 500 miles put new pads in. Its not worth the risk for the sake of a few quid,
 

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Would this disc be suitable: http://www.motopike.com/index.php?route=product/product&product_id=524

I am currently using EBC pads, replaced only about 500 miles ago. Would I need to get a new set of pads with a new disc, or would the pads I have on there be ok still?
I can't really affor a Yammy one, arent they like £150 or something! :eek:
was about to buy one of these but then i had a look at the galfer ones from calsport and in total is only about £10 more if you include postage with the 'factory racing' one, plus they arnt made yet haha, thought i may aswel get myself a new front one to match aswel :p best price is from calsport :D getting new pads with each aswel, not good to have new discs with old pads really, and at 500 there worn in nicely
 

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Galfer did a boxed set at one point, which was a complete set up of discs, pads, brake lines and fluid.
£250 I believe it was?

That's what Omar has!
 

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Hi Guys, I will have the full front and rear disc and pad kit in April. I will make the hoses optional just in case not everyone needs or wants them.
The front and rear disc kit should be about £100. The discs are designed by ourselves and britsh made.

Hope that helps,

Adam
 
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