Un-warping discs

[ChristoT]

Hi all

I haz a problem with my ZX-4. The bugger's warped a front disc. Now, as I'm skint, but the disc has loads of life in it (binding old brakes caused the issue), I was wondering if there was a way to fix it rather than replace it? Heat it up, and squash it or summat?

Ideas please! 

[AdieR]

Heating it up is probably a bad idea in that it could cause it's own issues.

If there is plenty material, then it might be worth taking it to an engineering machine shop and get them to skim it - but check that machining won't take the disc thickness to / near it's service limit.

If it were my bike, I'd personally bin them discs, but I'm quite fussy.

[mickvp]

Do not heat them further and try and straighten them! This extra heat can cause work hardening of the carbon steel, causing it to become brittle, and meaning the disk could snap during use!

If you can setup a mag base and an accurate DTI on the disk, and it's not running out too much, you may be able to straighten it somewhat through a bit of brute force and ignorance. I personally wouldn't do that either, and it depends entirely exactly how bad they are, but I've seen it done (this could arguably also weaken the disk).

The easy answer, as said above, is to take it to a machine shop and have them turn it down on a lathe or milling machine, I've never heard of it being done to bike disks though, simply because they are so thin to start, I would imagine its impractical to do it without reaching the service limit.

The only practical solution, is to replace the disk(s). Or just don't use your brake anymore

[Hedgetrimmer]

A Mercedes can stop you even more effectively than brakes 

Depends on how far out it is. Skimming motorcycle discs is done, but it doesn't take much distortion to make this unfeasible. Don't foc about with brakes Christo. You know better than that.

[ChristoT]

My current problem is no money, and the fact that no-one else knows what will fit my bike. That, and discs are fucking expensive!

[bri h]

with the way your lucks gone lately i dont think you should tempt fate chris. i know its not what you want to hear but put the bloody thing in the garage till you can afford some decent discs!

[Exupnut]

A Mercedes can stop you even more effectively than brakes 

Lol

Spoke to red yesterday. He's got some cash for u. So u can use that.

[red98]

car discs can be skimmed...in the good old days min thickenss was cast into the discs,might be worth a close look at your discs or the info might be in the haynes book of lies........if you do go this way make sure the people you use know what they are doing......measure them and see how far out they are......as for heating them...isnt that what caused the problem in the first place.....come on christo you know better than that   

[ChristoT]

with the way your lucks gone lately i dont think you should tempt fate chris. i know its not what you want to hear but put the bloody thing in the garage till you can afford some decent discs!

No chance, I need it to commute to work every morning! And my job's out in the sticks.

[ChristoT]

car discs can be skimmed...in the good old days min thickenss was cast into the discs,might be worth a close look at your discs or the info might be in the haynes book of lies........if you do go this way make sure the people you use know what they are doing......measure them and see how far out they are......as for heating them...isnt that what caused the problem in the first place.....come on christo you know better than that 

No Haynes for the ZX-4. Too bloody rare.

Heating made the disc malleable, I was thinking I could repeat the process with high pressure and a bit of heat to prevent snapping.

[Bracechenko]

Have a look at the breakers yards either locally or nationally. Might find a replacement set at an affordable price

[Fazerider]

Are there discs from other models that would fit, such as the ZZR600 or ZXR250?
Manufacturers usually use these sorts of things on more than one model so a bit of research could increase the chances of finding a second hand disc.

[red98]

agree with that fazerider.....do you have a good breaker near you,parhaps taking a disc along and compare to other models 

[JoeRock]

Go onto the EBC website and cross reference the discs. Look up the part number for the EBC discs for your bike, google it, and see what models it comes up as fitting.

As people have said though, don't fuck about with brakes. And fix whatever caused it (I would guess sticking pistons) before it does it again!

[rayburn600]

Years ago I used to use a Compound on the Brake Pad surface itself. It came with a brush in the lid, you painted it on, (it was like black toothpaste)
Let it dry. It dries Hard and then use your brakes very lightly & this would Rub the Discs with the abrasive compound and this on many occasions sorted the problem.


Long shot I know, plus the stuff was expensive, but it lasted ages.
R

[pilninggas]

this is presumably the same as your model:

http://www.ebay.co.uk/itm/NG-Front-brake-disk-Standard-KAWASAKI-ZX-4-400-88-89-/181208625510?pt=AU_Motorcycle_Parts_Accessories&hash=item2a30e03166

These other kawa models have the same part according to the vendor:

http://www.ebay.co.uk/itm/NG-Front-brake-disk-Standard-KAWASAKI-GPZ-S-E1-E10-500-94-04-/181208623102?pt=AU_Motorcycle_Parts_Accessories&hash=item2a30e027fe

http://www.ebay.co.uk/itm/NG-Front-brake-disk-Standard-KAWASAKI-GPZ-R-400-89-/181208622959?pt=AU_Motorcycle_Parts_Accessories&hash=item2a30e0276f

http://www.ebay.co.uk/itm/NG-Front-brake-disk-Standard-KAWASAKI-GPZ-R-600-85-93-/181208622975?pt=AU_Motorcycle_Parts_Accessories&hash=item2a30e0277f

It also shows the sizes - more delving might show more bikes with the same part number

Looks like the GPZ500 disc fits and those are two-a-penny.