Not sure if this is true or not, brake discs.

[andym]

So I took my bike for it's MOT today and was told the front discs are slightly warped (only advisory), the tester was telling me that if the bike sits for a while then this can happen because of the pressure from the brake pads on the discs... and that if the bike isn't going to be used for a while it's better to push the pads back a bit so they aren't resting on the disc.


Anyone heard of this before?

[Bhud]

No, not heard that the disc can deform from constant contact and pressure from pads while stationary. My Kawasaki project bike (now wrecked) had been left sitting for years, and the brake pads had seized to the discs. This was fixed by rebuilding the calipers. The discs were fine.
However, that isn't to say your discs aren't warped for some other reason.

If I had to lay up a bike for a while, I would remove the calipers from the discs altogether. It's true they seize up from being left alone.

[Pete.]

He's full of shit. The reason for pressing pads away from the disc is to stop them binding from rust. If you have the type of pads that can do that you can get a pulsing lever for a while as the disc passes over the rust pitting but as for simple pad pressure warping the disc, no, he's full of it.
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a.k.a 'Geri'

132.9mph off and walked away. Gear is good, gear is good, gear is very very good

[andym]

I thought it might have been garage BS, but at least this place didn't offer to sell me new discs.

Thinking about it, the longest the bike hasn't been moved is about 3 months, my (ex) VFR sat for the best part of 2 years without even being moved, and just needed brute force and ignorance to push out of my lockup.

[-]

[xX-Alex-Xx]

Just tell him you wrapped an elastic band around the opposite side of the disk when it was stored to make sure it evened out

If the disks were that soft, they'd fall apart with normal use.
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DILLIGAF

[ThunderGuts]

There's virtually no pressure on the discs at "rest" otherwise you'd never be able to move the bike. They barely scrape the surface until they're applied.
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TG.

[Tankie]

[rpsmith79]

[brains_t]

I had similar in the past but the mechanic told me disc locks tended to be the cause

[sickpup]

[Pete.]

Warping from constant pressure and pitting from corrosion are not even close to being the same thing.
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a.k.a 'Geri'

132.9mph off and walked away. Gear is good, gear is good, gear is very very good

[sickpup]

[Tankie]

In this day and age there should not be any "ignorant MOT testers " left working
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Always learning, everyday is a school day

[JackButler]

I have a £40k surface table & a horrifically expensive ruby tipped CNC measuring arm to prove this . . .

I offer a bounty of £10k to anyone who can produce a genuine, physically warped brake disk. They simply don't exist & the phenomena that is wrongly described as "it's a warped disk innit mate" is something entirely different from a physically warped disk.

P.S. Don't go whacking it with an hammer or pressing it with 4tons of hydraulics . . . We can tell.
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I clean my guns with the tears of the snivelling, left wing scum.

[sickpup]

[Tankie]

Back in the late 80's Yamaha had an issue with warped discs ( FZ, FZR ) caused by semi seized calipers. just because your an engineer does no make you right !
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Always learning, everyday is a school day

[Tankie]

Sickpup , MOT tester now have to go though a much longer education process to get their licence , and go through regular up date course to retain their ticket , so they should be able to give a proper valid reason why he/ she feels that the machine does not comply with the standards required.
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Always learning, everyday is a school day

[Evil Hans]

[sickpup]

[Tankie]

Is this you background,...no your not correct, it was mine .
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Always learning, everyday is a school day

[sickpup]

[Tankie]

But as a workshop it is, when the mot input has been done you revert back to your normal , probably repairing motor vehicles
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Always learning, everyday is a school day

[sickpup]

[cimbian]

NBR, but.

A friend in the US was constantly getting warped discs on his Beemer and would replace them every four months!

When I drove with him he was a shite driver and red-light drag queen. As soon as the light changed it was full-on to the next light where he would brake hard and late, then sit there with his foot hard-down on the brake (automatic Xmission). Then do the same thing, over and over.

I suspected that his discs were heating and cooling unevenly.

Suggested that he grow-up for a few months to see how he got on by using P and releasing the brake pedal when stopped, and it made a difference. Discs (rotors) lasted much longer.

Of course, he then had a choice to make. Drive like a knob and shell-out, or not... He's still a knob.
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22PlusY
Current: Moto Guzzi 1100 Breva. Previous: Honda XL650V TransAlp
Bearded, Balding, Born again Buddhist Biker