Mot Failed! Warped Discs..

mattster · Post by **mattster** » Thu Jan 20, 2011 12:19 pm

Morning folks...

Froze my fingers off headinginto town this morning to get an mot, all fine bar the front discs are excessively warped..

From searching the forum it appears to be a Firestorm trait!! Any particular reason? I know i hardly use the brakes... i just roll off the throttle!

Been having a search round the internet today. best price appears to be Sandy Bike Spares at Â£140 for a pair. Considering that's half the price i was quoted by a main dealer this morning, i'm tempted just to jump in there - Anyone had any experience of discs from here?

rob's red storm · Post by **rob's red storm** » Thu Jan 20, 2011 12:35 pm

My discs are on the way out as well, just passed the mot with them though! If you find a solution let me know! Strange that the front warp, I'm the same that I mainly use the engine braking. Could be that not enough heat gets into the discs for when they are used hard, so sudden heat generation causes the warping (complete guess!)

lloydie · Post by **lloydie** » Thu Jan 20, 2011 1:13 pm

its the same on mine . ebc are good but not cheep ,
when looking for discs all these fit
CBR 600F3 1995-1998
CBR 900RR 1994-1995
CBR 400 RR NC23 NC29
RVF 400 R NC35
VFR 400 R NC30
VFR 750 1994-1997
vtr 1000

tony.mon · Post by **tony.mon** » Thu Jan 20, 2011 6:43 pm

It's travelling at warp speed what does it.

LotusSevenMan · Post by **LotusSevenMan** » Fri Jan 21, 2011 12:37 pm

I had Suzuki that warped its disc. Had it skimmed for a tenner. Thought that being thinner it'd be worse after a short while, but they took only a small amount off and it was fine for a couple of years before I sold the bike. It was almost as if the heat generated initially warped the disc but the heat 'treatment' allowed it not to warp again!!!!!
Good luck!!!!!

Road Runner · Post by **Road Runner** » Fri Jan 21, 2011 4:59 pm

Dont hold the front brake on when stopped (pressing hot pads onto one part of the disk),
use the back brake to hold the bike if necessary.

rob's red storm · Post by **rob's red storm** » Fri Jan 21, 2011 5:49 pm

tbh, I never really use the fronts as the engine can do the same job (and sound amazing through the scorpions whilst its at it

)

Changed out front wheel bearings today, bearing need replacing on the top yoke as well...ho hum, the list of work goes on and on...

alan g · Post by **alan g** » Sat Jan 22, 2011 1:17 pm

The bobbins may be sticking you can free them up by turning them and a little WD40.

I had a problem with warped discs, and sorted them out like this:

Lift the front wheel of the ground, spin the wheel and find the high point of the run out,
Take a medium size hammer and tw@ the high point, spin the wheel and measure again, if necessary reapply the hammer.

tony.mon · Post by **tony.mon** » Sat Jan 22, 2011 1:23 pm

Definitely worth a go; you're only going to throw the old ones away in any case, so you might as well.
I'd suggest a big rubber mallet, though, to avoid dents or dinks.

alan g · Post by **alan g** » Sat Jan 22, 2011 1:27 pm

tony.mon wrote:Definitely worth a go; you're only going to throw the old ones away in any case, so you might as well.
I'd suggest a big rubber mallet, though, to avoid dents or dinks.

Tonyâ€¦ If it canâ€™t be fixed with a hammer itâ€™s an electrical fault!

alan g · Post by **alan g** » Sat Jan 22, 2011 1:35 pm

I put a 5mm cap head bolt through the hole in the bobbin with a nut either side of the bobbin and wiggled and turned the bobbin and sprayed with WD40 (surprising how much cra* came out) there was over 1.4mm of run out before the hammer and less than 0.2mm after! Service limit was 0.3mm!
This is the bike,but the same appies to the Honda

Hope this helps,
Alan

tony.mon · Post by **tony.mon** » Sat Jan 22, 2011 1:39 pm

Good tip, but make sure that no wd40 is left in the bobbins- maybe brake cleaner would do just as well.
Oil on disc- that would ruin your day for sure....

Alan, how did you clean your disc rotor and bobbins afterwards?

alan g · Post by **alan g** » Sat Jan 22, 2011 2:02 pm

tony.mon wrote:Good tip, but make sure that no wd40 is left in the bobbins- maybe brake cleaner would do just as well.
Oil on disc- that would ruin your day for sure....

Alan, how did you clean your afterwards?

Tony, youâ€™re rightâ€¦ the wheel was off for the bobbin treatment and the discs were in the vice. Clean up was with Gunk or break cleaner.
Wheels put back on without callipers and the wheel spun and the run-out measured, high point marked with felt pen and clonked with hammer on that mark. Turn again and measureâ€¦if more is needed clonk again. The high point will move around the disc as the bobbins hold it in that position.
It worked for me and the Hayabusa did about 6000 miles last year and still got the same discs on!

Alan

benny hedges · Post by **benny hedges** » Sat Jan 22, 2011 2:04 pm

alan g wrote:The bobbins may be sticking you can free them up by turning them and a little WD40.

I had a problem with warped discs, and sorted them out like this:

Lift the front wheel of the ground, spin the wheel and find the high point of the run out,
Take a medium size hammer and tw@ the high point, spin the wheel and measure again, if necessary reapply the hammer.

done that meself and got called a rough butt but it saved me Â£150 and a retest.

agree on the bobbins - they are supposed to be floating discs. doesnt take much to make them not float

alan g · Post by **alan g** » Sat Jan 22, 2011 2:37 pm

benny hedges wrote:
alan g wrote:The bobbins may be sticking you can free them up by turning them and a little WD40.

I had a problem with warped discs, and sorted them out like this:

Lift the front wheel of the ground, spin the wheel and find the high point of the run out,
Take a medium size hammer and tw@ the high point, spin the wheel and measure again, if necessary reapply the hammer.
done that meself and got called a rough butt but it saved me Â£150 and a retest.

agree on the bobbins - they are supposed to be floating discs. doesnt take much to make them not float

Well Benny. I was at the point of buying a new set of discs before I gave this a try, nothing to loose really â€¦ It worked for me. There must be a lot of discs thrown away that could be used.

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