FZRSupport: the FZROnline Archive

Greetings FZRers, long time lurker and technical info parasite, first time poster, needing somebody to pull a rabbit out of the hat for me...

91' FZR1000RU so we know what we are talking about here...owned for around 18 months and this problem has been with me since day one and resolutely refuses to be solved!
Original front brake set up is twin Harrison Billet Mini 6 calipers, on fairly newish non OEM (unknown manufacturers, no id marks on them bar serial number) discs, goodridge ss lines, single from the master cylinder to the RH caliper, then piggy back banjo connector looping over to the LH side. Get the picture?

As I said, this fault has been evident for a long while...under heavy braking getting a rather serious judder which feels just like what a badly warped disc would feel like. Under light braking, say pulling up to a junction in town you can still feel it but much reduced almost like the forks are pulsing.

Anyhoo, initial thought is warped disc or discs, even tho on inspection they appear to be pretty good and show no evidence, no obvious warp to the eye if you raise the front end off the deck and check the clearance thru the slot in the caliper as you spin the wheel, no discolouration, so despite the physical evidence I wasn't actually convinced they were warped.

However, slight leak on the left fork seal needed attention anyway, so whilst doing that highly unpleasant job I did a front wheel bearing change, obviously changed both seals, dust covers and filled with new oil, replaced the original discs with shiney EBC's and fitted fresh new pads, pins and R clips (12 of the buggers at best part of £100 a set!!!) and reassembled all nicely greased.
That you would think would have solved the problem...first ride after doing it and the front end is exactly the same, no decernable improvment what so ever. The word "B@ll@cks" springs to mind, especially considering £300+ spent on new discs that replaced what was probably perfectly good originals...

Ok so this leaves me scratching my head...what else could be the problem. Due to the fact I needed to use the bike for a while the fault remained present, and I continued to ride everywhere cautiously ever aware that over braking on the front could be disasterous...

So over the months I notice the RH pads seem to be wearing a bit quicker than the LH ones, which leads me to think that the right caliper and disc must be working harder than the left, soooo....maybe the brake line set up as it goes to the RH caliper before looping thru to the left. Perhaps an air lock in the loop between the two, perhaps a pressure drop between the banjo going in and the one coming out. Complete brake fluid change and bleed, no air present, fault the same. Ok, shot in the dark then, swap the brake line set up from a single line down, to the race set up of two indipendant lines from the master cylinder, one direct to each caliper.
This seemed to slightly improve the problem, but only marginally, it was pretty much still the same.

I'm scratching my head so much now my hair is starting to look like it would be better off on and 17th century monk...

Anyhoo...upshot...MOT test last week, my regular garage...fault is picked up. Touch and go failure, but I explain that it was exactly the same last time the tested it a year ago and hadn't even noticed it then...that and the fact they know I'm aware of it and have ridden around on it for a year like that...and I am actively trying to resolve the problem turns it into an advisory instead, which covers them should I high side it in the near future. They kindly let me use their brake testing equipment for 15mins to try an identify the fault. Taking the RH caliper off and testing the brakes and there is an obvious point in the rotation where the braking force drops momentarily before going back to normal. Refitting the RH caliper and retesting it dampens the effect, in other words the fault is still measureable, but less pronounced.

Cutting to the chase then, I'm left with only a couple of options...
1. Both the discs I removed, and the New EBC's I fitted were both warped (realisically tho...is that really likely...brand new disc exhibiting the exact same problem?)
2. There is some issue with the caliper (having spoken to Billet though, they seem to think not and suggest the disc like everyone else)
3. There is an issue with the master cylinder, perhaps a pin prick hole in a seal...but that's clutching at straws to my mind.

So...anybody got a suggestion as to what it might be before I fork out another £400+ on a pair of discs and a set of pads only to find its still the same, then blowing God knows how much on replacement calipers to much the same effect...etc etc etc...

In precis...what has been done so far....
Fork seals, Dust covers and fork oil replaced (had a new tyre and wheel balance done at the same time now I think of it)
Front wheel bearings replaced.
Front discs replaced and new pads fitted
Front brake lines replaced, brake fluid changed and bled.

ANy advice before I lose more money/sanity/hair folicals would be most appreciated! Cheers!

do you have access to a dial guage?

strap it to the fork and then check the discs AND the wheel rim for run out

Discs (both new and old set) may not be seated correctly against the wheel hub???? Even the slightest of debris will make it feel as if its running out

Is one of the calipers dragging?

cant think of anything else it could be

good luck...........

Me, I would run two lines from the MC to each individual caliper.

Going to one, then looping over to the other seems like it would be theoretically okay, but it DOES introduce variables into the situation that don't need to be there.

And, like Stig said....dial gauge the rotors and wheel-don't forget the tire as part of the assembly.

It could be as simple as a wheel with radial runout(or tire mounted to have such) that is giving you this feel.

Stig wrote:do you have access to a dial guage?

strap it to the fork and then check the discs AND the wheel rim for run out

Discs (both new and old set) may not be seated correctly against the wheel hub???? Even the slightest of debris will make it feel as if its running out

Is one of the calipers dragging?

cant think of anything else it could be

good luck...........

I don't actually, but was thinking along the same lines even if it just does eliminate one other possible problem. Might be tricky getting a gauge mounted firmly enough to the forks to get a decent reading tho. Don't think the calipers are dragging - certainly no evidence of it anyway.
I doubt the rim is out some how, no shake from the front end except when braking, otherwise the front is absolutely spot on, could be a uneven mounting of the disc to the wheel I suppose, even tho i did clean the face fastidiously when I put the new discs on.
Thanks for the input!

reelrazor wrote:Me, I would run two lines from the MC to each individual caliper.

Going to one, then looping over to the other seems like it would be theoretically okay, but it DOES introduce variables into the situation that don't need to be there.

And, like Stig said....dial gauge the rotors and wheel-don't forget the tire as part of the assembly.

It could be as simple as a wheel with radial runout(or tire mounted to have such) that is giving you this feel.

Swapped the front line set-up to a twin line, it did marginally improve the problem but didn't cure it.
Front tyre has been changed fairly recently and no change to the fault, and the handling otherwise is absolutely perfect, so I doubt there's any radial run out of the wheel to be honest.
Looks like I'm going to be on the hunt for a dial gauge then...
Thanks for taking the time to reply, appreciated!

you could clamp the rod to the dial guage to the mudguard mount or caliper mounting bolt or even tie wrap it tight to the fork leg

B,
OK so you have changed out all the old stuff at the front end and it still judders under braking.

Stupid question when was the last time you checked the steering head bearings?

If they are:-
loose
worn
Under braking the whole front end will judder ..................................

yamaha_george wrote:B,
OK so you have changed out all the old stuff at the front end and it still judders under braking.

Stupid question when was the last time you checked the steering head bearings?

If they are:-
loose
worn
Under braking the whole front end will judder ..................................

I was thinking along these lines too or make the off chance that your axle could be bent <---that's just a guess seeing how you have changed almost everything else

sweekster wrote:

yamaha_george wrote:B,
OK so you have changed out all the old stuff at the front end and it still judders under braking.

Stupid question when was the last time you checked the steering head bearings?

If they are:-
loose
worn
Under braking the whole front end will judder ..................................

I was thinking along these lines too or make the off chance that your axle could be bent <---that's just a guess seeing how you have changed almost everything else

I had the problem with a slight shudder because of the front axle being bent. That would be my suggestion too.

Hi,
I have never found a bent axle in all my years but considering some of the wimpy sizes on Yamaha's it would not suprise me.
After talking back in the 80's with Erik Buell I change my axles out to the biggest the wheel bearing o/d will stand in the way of i/d some bearings go up to 4mm bigger i/d with the same o/d and that makes for a FAR SUPERIOR front & rear end flex wise. see my bit in the WIKI

i'd go head bearings too, mate had this on his trackbike under heavy braking.

Hi guys,
Thanks again for the input, sorry for the delayed response, the combination of work and family means I've not been around to catch up with this thread.

Firstly, the front axle is definately true, when I had the forks done and front wheel bearings replaced I asked the workshop to check that just to eliminate it and they seemed to think it was AOK.

I have checked the headstock taper bearings for play - lifted on a swingarm pivot stand, rear wheel tied down so the front wheel was floating, and as much as I wiggled the wheel forwards and backwards, and side to side, I felt no "slackness" in them, no tight spots or grinding/rumbling noises. I'd be suprised if they were gone. No tracking on the road or odd noises front the front under normal riding (ie. not under braking).
Also, during the MoT test, that is one item they do check, and it wasn't noted down even as an advisory.

I'm getting more convinced it's either another warpped disc (unlikely as I've swapped them already), there just isn't much else it can be. Either that or as has been suggested here, a bit of muck between the rotor inner and the actual front wheel that was still there even though I gave it a good clean before bolted the new one on. Considering the EBC discs are fully floating though, it would have to be quite a dramatic distortion to give the problem, probably one that would be visible to the eye I would think. Perhaps because the 6 pot Billets I've got on the front, the actual surface area is a bit longer in the vertical plane than the original calipers and pads (weren't they 4 pots on the first Exup RU's?) so that might be why the disc's can't "float" enough to compensate for the mis-alignment...

Anyhoo...I have finally got around to ordering a dial gauge, so hopefully when it's arrived and I have some time without loved ones or bladdy work getting in the way of the more important things in life I'll get the nose off the ground again and try to finally track down what the problem is once and for all. I'm expecting to be forking out the best part of £400 on a set of Brembo's in the near future though, and yet another £100 on a set of pads!

Cheers for your time folks, we will get there in the end, even if it kills me/makes me bankrupt/drives me clinically insane in the meantime!

sod forking out nearly £500 for bremos....

fit some R1 gold spots with matching M/c. They'll stand it on its nose at 70 with 1 finger if you wanted them to. Difference is night and day compared to OEM
check this link....theres all the info you need, just click the images for more info

http://www.exup1000.co.uk/tech_info_area/brakes.htm

Stig wrote:sod forking out nearly £500 for bremos....

fit some R1 gold spots with matching M/c. They'll stand it on its nose at 70 with 1 finger if you wanted them to. Difference is night and day compared to OEM
check this link....theres all the info you need, just click the images for more info

http://www.exup1000.co.uk/tech_info_area/brakes.htm

Stig,
Brembo's are the Nike brand for bikes just a bloody label I have brembo's on my hitech RD I bought from Y-Geo.and I have used blue spots & gold spot .
Gold spots with their piston coating give far superior feel, over the gold brembo off the fully adjustable monster forks, work well but needed some work to get rid of the wooden feel with very little feedback to my hands.
Thinking back too I had a set of six pot NISSIN calipers I tried out they were mated to 320 mm discs so the swept was ok no juddering but a sphincter tightening experience if you used more than one finger to squeeze the lever

I'm running 6 pot Harrison Billet calipers and the original master cylinder, and (ignoring the pulsing problem obviously) the general feel is good and nicely progressive, so don't think I need to look at swapping them out just yet. Only issue is the cost of a set of pads really (around £100 a set as there's 12 pads in total).

Going to have to swap out the discs though, I fitted EBC's X-Lites when I last changed them, basically as they are a "brand" over some unknown manufacturer from china, so I thought would be a decent swap out (price and quality considered). My local bike shop though said they have had issues with them being warped out of the box apparently though (if I'd known that I'd have thought twice before getting them). Only considering Brembos because their quality control is pretty good by comparison so may be worth the extra money if it's definately going to cure the problem. Having run several bikes with Brembo set ups in the past, I've always been impressed with their performance (my little Mito with a single disc at the front is brilliant under braking and capable of some impressive stoppies...).

Great link though, a lot of options in the discs there, so may be able to search out a decent alternative with some intensive web searching!

Thanks for the input!