Brake Disc Warping - Measurements?

I need some more information for brake discs.

What are the measurements for a brake disc that is warped? For instance, I have a measurement stating that the front brake disc is 0.2mm out of alignment on one side and 0.16mm out of alignment on the other side.

This was considered at the time to be within the tolerances of the front brake discs.

I understand that each brake disc might be different, but these numbers seem tiny to me and I wondered whether the actual measurement for when brake discs go is in the 1mm+ range or whether it is 0.3-0.5mm?

I just don’t know what those above measurements mean in terms of how bad the warping was.


Well 0.2mm is the thickness of a hair … I would say that would be within the tolerance of the machine that makes the discs in the first place before they are even mounted .

I would have thought the same, since it is such a low amount, but why would the mechanics make a note of the fact that this is how far the discs were out if it were merely an amount which was within the margin of error?

We tend to do that if we know something is going to come back for its next service, its good to have some baseline numbers to work from . And it looks like we are doing something to justifiy the money we charge :smiley:

it was 0.4mm tolerance on my fireblade (bike mechanic looked it up for me). that sounded very small to me, 0.2mm sounds ridiculously small!

…assuming we are talking about consistent warp across the diameter of the component?

According to the official Yamaha service manual I have here, the runout limit for the FZS1000 is 0.1mm! :blink:

Kaos, as can be seen by these 2 posts, there is it would seem a variation on ‘official’ tolerances across models, you need to find the specific one for the bike you’re looking at, it should be listed in the service manual. If you’re looking at this from a legal standpoint I would assume that a court would base it’s decision on the manufacturers official figures.

From personal experience, even the slightest off alignment makes a huge difference with handling under breaking.

Warped discs are really bad news :frowning:

Thanks for the tip on the manual. Runout is 0.3mm. Now I just have to google “runout” and find out what it means :stuck_out_tongue:

runout = wobble or oscillation .
I have had a look about the net about the sort of sites we use at work for buying stuff and what they say casting/milling tolerances are . They all say very tight or minimal they don’t seem to want to give actual figures . Found some car ones that are mill balanced to within 2oz per inch …so thats weight balance like a tyre on a wheel rather than deformation and not very helpful . They say at over 0.2 on a nonfloating disc is where you might just start to feel a brake judder under serious braking circumstances . Some company out there claims it can make your discs better than manufacturer can by milling to 0.05 increments and a total skim depth of 0.2 over the entire surface . From taking it all in it seems 0.05-0.2 is what yer average quality off the shelf common or garden disc is made to come in at .

I think once you get outside of the distance your floating disk can move laterally, you’re looking at trouble…certainly was the case for mine.

Once they start to warp they get worse quickly too.

Yeah, this is my legal argument. The discs began to warp while under warranty, company knew that they would get worse, they did; they are no longer road worthy, but by this stage the bike was no longer under warranty and the company doesn’t want to fix them.

My argument is that discs warping is rare enough (I have 3 bikes with 47k, 40k and 35k miles…none have ever had front discs warp) and once the company knew it had started they should have acted upon that knowledge while the bike was under warranty.

when mine warped I was told “they tend to go bad around 30.000”

Usual warranty story - if they’re within tolerance then they’ll do nothing even if they know the problem is inevitably going to get worse. If it then progresses to the point of the discs needing replaced but outwith your warranty period, then it’s your problem.

That said, you’re in the legal profession so by the time you’ve sent them 3 letters arguing your case, they may decide it’s cheaper to refund the cost of replacing your discs than to keep arguing with you. 3 mobile are my personal favourites for arguing with :slight_smile: …give the customer a contract but can’t uphold their end, and get very shirty when you try to get them to stick to it!

My favourite was when I signed up to BT years ago, and realised their service was rubbish AND expensive.

They sent me an email, one of those nominal emails, by the way we have changed your terms and conditions you can read them here. With a link to a 1,000 page document with 200,000 words.

So I immediately rang them and said…I would like to cancel my contract…sure thing Mr Kaos…that will be £XX as a cancellation fee.

No, I don’t think so, you have changed the terms and conditions and I don’t agree with that change.

Yes, but we have the right to change the terms and conditions Mr Kaos, it is a part of the contract…

Yes, and I have the right to say “no thank you” and leave, otherwise you could change them to bill me £million a day and I would be stuck with that? No, I have the right to leave the contract if you change the terms of said contract.

Oh, ok then.

Got me out of paying over the odds for crappy internet for 18 months.

^^ :cool: Like it!

3 Mobile… I could end my contract anytime after the minimum term “provided you give notice to Three Customer Services at least 30 days before the date you want to end the agreement”

So I did. About a month into an 18 month contract, I gave them their “at least 30 days” notice as I knew I wouldn’t want to continue with the contract after the 18 months. They didn’t like that at all. Kept arguing it had to be exactly 30 days notice. So I kept arguing otherwise and that I was complying with their contract, and that in doing so I wouldn’t be liable for payment of any bills after the 18 months. They said their system wouldn’t let them enter notice to terminate contract that early. No my problem said I :smiley: In the end I chickened out and still sent them notice to terminate 30 days before the 18 months was up, but I always wondered how long they would otherwise have continued to provide me with a mobile service for, and where it would have gone in terms of chasing me for payment, debt collectors, court, affecting my credit rating etc.

Have found a new target these days… TV Licensing! :smiley: Though having won a 32" flat-screen at Goodwood in July, unless it’s a SmartTV, I might have to finally buy a license :angry:

Being taken to court doesn’t affect your credit rating, only losing does.

You should have stuck it out.

There was a great story recently of a guy who got one of those “easy credit” deals in the mail, so he amended the contract so that the credit company had to give him free credit.

They accepted the returned documents without reading them, and he won in court.

That is the story, which I think is the most excellent thing I have seen done in ages.

I don’t have a TV licence either, they send me letters occasionally and seem incredulous that someone can live without a TV.

^^ Like that one about the credit card. But now the bank is suing him for fraud. I suppose his mistake was to scan the contract and alter it, which they didn’t pick up on. I’m sure if he’d just amended it with a biro pen and the bank didn’t notice, they’d have no defence at all. Reminds me of a guy I used to work with who sent his contract of employment back with his notice period amended to ‘0 weeks’. Told the boss a year later at the end of a days work that he wouldn’t be back in the morning, or ever. Boss was fuming but was politely referred back to his contract which no-one had noticed. :slight_smile: