Yamaha TRX850 Enthusiasts Forum

Hi there,

Probably more a generic brake question but could be trex related as lots of people ditch the standard non brembo calipers.

My front brakes are pulsing. When I bought the moto it just had new front rotors fitted which I thought was great. Sometimes they pulse more sometimes not at all could be temperature dependant but after seeing that the RHS pads are wearing on a slight angle I suspect the caliper.

Cheers,
Martin

Sounds like a warped disk to me.

could be warped discs as greg says. could be you've got some stuck pistons which are warping your discs and is why your bike had new discs fitted.

Agreed so far, it would be as well to check for warpage which should be easy to do with a pointer taped to the forkleg...

However - I have had a set of PFM cast iron discs (sorry Martin!) on mine for a while, and have noticed a definite 'pulse' on the brake although it isn't transferred to the brake lever... I might take some of my own medicine and run a dial gauge over it to check...

Not hijacking the thread, but I recently received a Magura radial cylinder to replace the faulty Lucas unit - weird braking feel to this puppy as it seems to have very little initial feel, and needs a fair squeeze to get them 'on' but when they start to work they are sh!t-hot..! The cylinder is marked 20 so I'm wondering if the ratio isn't optimum..

I also never realised how dirty cast brakes are! Shltty brown shlte all over the downpipes all the time and it's a bugger to get them clean too!

G

youngy wrote:could be warped discs as greg says. could be you've got some stuck pistons which are warping your discs and is why your bike had new discs fitted.

If you've still got the original grey Sumitomo jobbies, they are very prone to fouling, sticking on and thereby, eventually, warping the disc. If they're sticking, you may get pulsing even without any warp or adverse pad material deposition on the disc. I had that happen to mine way back in the mists of 1998. First thing I would suggest is to unbolt the calipers, pull the pads and give them a seeing-to with the old toothbrush and lots of brake cleaner to try and free up the recalcitrant caliper.

If that fails to get normal action from each piston, get a set of blue-spots from a breakers rather than wasting money on a rebuild kit, as the price will likely end up being similar. Blue spots are much less prone to this problem, and you can avoid it with intermittent preventative cleaning.

Greg wrote:Agreed so far, it would be as well to check for warpage which should be easy to do with a pointer taped to the forkleg...

However - I have had a set of PFM cast iron discs (sorry Martin!) on mine for a while, and have noticed a definite 'pulse' on the brake although it isn't transferred to the brake lever... I might take some of my own medicine and run a dial gauge over it to check...

I also never realised how dirty cast brakes are! Shltty brown shlte all over the downpipes all the time and it's a bugger to get them clean too!
G

I did like the Spiegler iron discs I had on my GSX-R WV. More consistent feel and lots of power in track day use compared to stainless. You just have to get used to orange discs after leaving the bike for 12 hours.

idl1975 wrote:If that fails to get normal action from each piston, get a set of blue-spots from a breakers rather than wasting money on a rebuild kit, as the price will likely end up being similar. Blue spots are much less prone to this problem, and you can avoid it with intermittent preventative cleaning.

Saying that, i have some blue spots and am getting pulsing, not trough the lever but deffinatly there, front and rear brakes. I'm going to check my disks with a pointer and how free the pistons are.

Thanks for your input guys.

I gave each caliper a good clean, checked the wheel bearings, and will do a laser check on the discs to see if they are true.

The first time this happened I gave the calipers a good clean and the problem was gone and then slowly returned after a couple of hundred k's.

That red rubber grease is very good for lubricating the seals. Keeps them from seizing for quite a while.

Excellent, I have a whole tub of that Castrol red grease left over from a job.