WR250R braking problem

[denny]

I have a WR250R sitting on supermoto rims. Recently changed brake lines & front pads and switched the disc on supermoto front with a larger 320mm version incl caliper bracket. Front brake now bites/releases/bites/releases/etc when lever is pressed. Tried cleaning disc & bleeding again with no joy.

Switched rims with oem 18/21's and both brakes work fine. The new disc looks fine, any ideas on what the problem could be, bedding in issue? Cheers

 

[Timolgra]

And you're sure you have the right caliper bracket and the pads are in contact with the whole face of the disc? (Which isn't warped and fitted the right way round)
Also with the pads out is the disc running centre in the caliper?

 

[theoneandonly]

and the mounting surfaces clean , for the disc ?

 

[denny]

Timolgra - Rims, bracket and disc are all Warp9 bike specific. Everything you've mentioned is in check

the1&only - Cleaned with brake cleaner

 

[Monkeynuts]

Double check that the calliper is sliding ok in the guides !

 

[denny]

Double check that the calliper is sliding ok in the guides !

Not sure how I'd conduct such a check. I'm assuming the caliper is fine as the problem doesnt happen when the OEM 21 front wheel is fitted (smaller disc/no bracket)

 

[dean0n0]

Is the big disc running true? Have you put a DTI on it to check?

 

[denny]

Is the big disc running true? Have you put a DTI on it to check?

Don't have access to a DTI, I can however hear a slight pad rub on part of disc when freewheeling, not sure if thats a caliper/pad issue or the disc though. Will be installing old smaller disc to see if the problem continues.

 

[Timolgra]

Don't have access to a DTI, I can however hear a slight pad rub on part of disc when freewheeling, not sure if thats a caliper/pad issue or the disc though. Will be installing old smaller disc to see if the problem continues.

Hi Denny, I did ask if the disc was warped earlier. When you say rubbing on part of the disc what exactly do you mean? If it's intermittent as you spin the wheel then it possibly is warped. You don't need a DTI measure the gap when there is one with a feeler gauge.
Good luck

 

[Neil W]

Work through it logically , get the front end up in the air and remove caliper and its bracket, spin the wherl with just disc fitted and does it appear to spin true, a pencil taped to fork leg touching the disc will act as a gauge .
If it looks okay mount the caliper adaptor and check it is true, if that is okay mount the caliper minus pads and then spin up the wheel. Is the disc central in the caliper and running true.
One of the above stages should confirm that the issue is either with the adaptor plate or disc.

 

[dean0n0]

Clean the mounting surfaces of the disc and wheel thoroughly, try the disc mounted 180 deg. from where it is now and see if it runs true, two small discrepancies added together could make a big run out, if you mount them opposite they may cancel each other out.
Running it catching in one spot will soon knacker the disc.

 

[Timolgra]

Interestingly I was just reading of a similar issue on a bike where it appeared the disc was warped after checking with a DTI.
Several discs later it transpired the disc mounting tabs on the hub were not aligned and needed machining.
Just a thought

 

[mikeyboy]

Interestingly I was just reading of a similar issue on a bike where it appeared the disc was warped after checking with a DTI.
Several discs later it transpired the disc mounting tabs on the hub were not aligned and needed machining.
Just a thought

I’ve had this a few times with aftermarket kit,
Insufficient clearances making the disc run out,not sitting true on the mounting face,
You don’t need a dti spin the wheel and watch the disc visually against the fork leg or other fixed references
On one bike(R100gs) with a 2piston fixed caliper(ie not sliding)
The disc was pushing the pads/pistons back,brakes bled,all good.
Move the bike outside the lever came back to the bars,pump the system up ,all good,push the bike into the workshop,lever back to bars.
Thought I was going mad

 

[denny]

Hi Denny, I did ask if the disc was warped earlier. When you say rubbing on part of the disc what exactly do you mean? If it's intermittent as you spin the wheel then it possibly is warped. You don't need a DTI measure the gap when there is one with a feeler gauge.
Good luck

Yes my bad, looked ok to my untrained naked eye. As suggested I stuck a pencil to the fork butting it up against the disc, when spinning the wheel roughly half scraped the pencil tip the other was off by 1-2mm. Same happened with a longer bolt through the caliper bracket.

Assuming a mm or two off is a sign of a warped disc?

 

[Timolgra]

Possibly disc or as mentioned the hub spigots out line. Quick check woukd be go swop discs.

2mm is a huge amount!

 

[denny]

Old smaller disc back on, caliper on as standard, no braking issues whatsoever. So now I see how Warp9's customer service is regarding warped discs

Thanks for all the input

 

[denny]

Warp9 sent a new disc out no questions asked, arrived Tues last week fitted just now, all working fine


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