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Discussion Starter · #1 ·
The story here is that my 750 L0 I am working through all its little issues had duff front bearings, and when I got it the front wheel would wobble like a scary thing on heavy braking (but OK on light braking, as it happened).

I replaced the front bearings. They were worn BAD. They rattle like a baby's toy if you shake them. It's hilarious!

Anyway, there has been a consequence in that the front tyre has some slight but noticeable feathering, which I am pretty sure is because of this.

I test rode it and noticed there was a bit of vibration/wobble remaining, which I did not concern myself with too much at the time, but it seems to have become a bit worse.

The thing is that it only wobbles when the bike is cold. Once it is warmed up and has been 'tilted over' a bit, then the braking is perfect, under heavy braking or whatever.

My question is, which of these do you think, on a GSXR, is the order of most likely issue for brake vibration when cold;
  • cold cheap-brand pads (they are new HH pads, but a cheaper brand)
  • cold tyre
  • cold fork oil
  • other (or other comments?)

My feeling is it's down to the tyre, because I am quite light on the brakes most of the time so they don't usually get so hot and they cool down again quite quickly (I tend to go faster by not slowing down much, unless it is absolutely necessary, if you see what I mean! ;) Actually this engine has very good engine braking, so can be controlled very nicely, much easier than my 250 2-stroke that had relatively no engine braking.)

thanks.
 

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I have no idea....so obviously I am gonna comment...

First off the tech gurus are gonna ask for pics of the tyre and rotors.

In my uniformed state I would think the tire may be the culprit but I would also maybe check the buttons on the rotors to make sure they are free and the rotor can float as needed.
 

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The front brake rotors “float” on “buttons” that connect the rotor to the center carrier. Brake dust can build up in between the surfaces and cause the rotor to not self center on the buttons.

I theorize that once you hit the brakes a few times and heat the rotor up, expansion of the metal from that heat creates clearance and allows the rotor to float properly.

Shoot some brake clean into that area and flush out as much as you can and see if that helps.
 

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Discussion Starter · #4 ·
I've always been a bit uncertain about this floating button thing, not really convinced as long as the discs are in the right place.

Anyway, it is a zero dollar cost, took ages but anyway, all are now freed and all with turn with just a firm finger pressure, so all done there.

I still am experiencing wheel wobble but it does seem to be reduced. What I think perhaps is that having stuck buttons is not necessarily terrible in itself but if you do have an issue then it will amplify it, that's the sort of conclusion I have come to.

So it is good to have done that but not the root cause.

I am thinking pads next because they are cheaper and easier than a new tyre, and the current pads don't seem to have quite the bite I would expect. I notice that TRW pads are available, were they original 1st tier pad suppliers into Tokico?
 

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Have you tried sanding the discs to remove the built up deposits and then re-bedding them in?

By vibration, I'm assuming this is not side to side but a "slip, grip, slip, grip" feeling as you brake?
 

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Discussion Starter · #6 ·
Have you tried sanding the discs to remove the built up deposits and then re-bedding them in?

By vibration, I'm assuming this is not side to side but a "slip, grip, slip, grip" feeling as you brake?
It's like a regular wheel wobble, like you might get if the wheel wasn't balanced or badly balanced with weights.

I mean, as far as I can tell, not really thought about whether it could be a slip-grip. I guess it could be now I think about it.

The discs are clean and smooth, not badly worn either they have been replaced some time or previous owners have been super light on the brakes. It does seem to be a bike with tons of engine braking performance. It's really not good to fluff a downshift and lose out on that engine braking, I guess you guys know this already?

I have checked for runout (when the buttons were frozen up) and both discs run true. I don't have a precise figure but it is unmeasurable to me, low fractions of a mm at most, and the buttons are freed up now.

I still think the most probable is the bearings were shot and caused abnormal tyre wear. I think if I am gentle maybe they'll wear more uniformly? (Hey, here's to hoping!) It's not so bad an effect, I can live with it, but it'd be the sort of thing you'd have to fix before a track day if it was like that all the time.
 

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I have had the grab, slip issue on my Z1000 for years and the discs are straight and even. I live in a mountainous area and the common complaint with cars is "warped rotors". Most of the time they are not warped but have uneven pad deposits on the rotors which can cause some pretty good shaking.

I've done a mild job of sanding my Z1k rotors and pads and it cures it for about a season. The last time I pulled them off the wheel and went at them with 160 grit paper, new Vesrah RJLs and bedded them in. I might be developing a little bit of the issue again after 10k miles, we shall see.

BTW, there is no pulsing or other feed back in the lever when this happens as you would get if a rotor was warped.
 

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Discussion Starter · #8 ·
I have had the grab, slip issue on my Z1000 for years and the discs are straight and even. I live in a mountainous area and the common complaint with cars is "warped rotors". Most of the time they are not warped but have uneven pad deposits on the rotors which can cause some pretty good shaking.

I've done a mild job of sanding my Z1k rotors and pads and it cures it for about a season. The last time I pulled them off the wheel and went at them with 160 grit paper, new Vesrah RJLs and bedded them in. I might be developing a little bit of the issue again after 10k miles, we shall see.

BTW, there is no pulsing or other feed back in the lever when this happens as you would get if a rotor was warped.
OK, will investigate. Thanks.
 

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The seized rotor buttons were an issue on the Brembo gold line rotors that came as stock fitment on the early Aprilia Mille R spec bikes.

The temp fix was what I described previously, which is the clean the rotor button mating surfaces out with brake clean. A slight step further was to brush some anti-seize on the exposed button surface and rotate the button until the entire contact surface was covered. That’s 10 buttons per disc and an afternoon’s worth of work….over beers.

What most of us ended up doing was to bend the tabs on the spring washers located on the back side of the disc that put tension on the rotor buttons. Doing so frees up the disc float so it’s more like a free floating disc. Complete with jingle jangle noises when rolling at low speed.

As I’ve never had issues in 20K miles of riding the yellow submarine, I cannot say first hand what the issue may be. It is possible that simply deglazing your discs may remedy the situation. Also, maybe remove the calipers and clean the pistons as one or more maybe sticking slightly and not fully returning after braking until you’ve warmed up the brakes.

Both are zero expenditure type actions so worth the labor to find out if one may be the solution.
 

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Did you replace the front tire? Not the wheel, it seems you're sorted that. Replaced/balanced the tire?

I read all this, I'd start there.
 

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Discussion Starter · #11 ·
Thanks, I think so too on the tyre. Just seems a shame to generate all that rubber waste for the planet, whilst also emptying the bank balance, when it is quite a narrow issue simply avoided by not heavy braking with 'not warm' tyres (never a great idea anyway)!

Definitely something not quite right and I agree with the tyres as the most probable. Will go shopping for tyres, see what's ideal. I don't like Michelin (what is on there now).
 

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Discussion Starter · #12 ·
I am getting a bit peed off with this wheel wobble now. I have ordered new Suzuki brand pads (and the shims, which it lacked, if they do anything!?) but pretty sure it will be a fat zero with those. Not sure even to bother. Disc buttons are all super free, and they are flat and perfect, buffed them up a bit to remove glaze.

In fact, all of that might have done something useful because now the effect is extremely consistent and easier to describe now. Not it's the case that for any speed below 50mph, nothing, but the faster over 50 I brake, the more the wobble for a given braking effort. Also more wobble with more braking effort.

I am pretty sure this is a function of the tyre.

However ..... should I not be expecting something better out of the steering damper to stop this? Maybe my steering damper is shot, how can I check this, and would it make 'that' difference and allow the wobble?

Just a reminder that the bearings on this wheel were shot and I think it has feathered the tread. We also have lousy camber on our roads here which aggravates wear.

So, is this a case of a new tyre, or do I need to check out that damper first? How do I test it?
 

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Certainly from your description it is what is referred to as “harmonic” meaning it occurs at or around a given speed/rpm.

I’d just have a new tire fit and see what it does. The thing is, there may be carcass damage internally that you can’t see. I don’t know what kind of mileage you did on the tire with the crapped out bearings.

If it doesn’t solve your issue, at least you have a new tire and you eliminate one more factor from the diagnostic process.
 

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Discussion Starter · #14 ·
Certainly from your description it is what is referred to as “harmonic” meaning it occurs at or around a given speed/rpm.

I’d just have a new tire fit and see what it does. The thing is, there may be carcass damage internally that you can’t see. I don’t know what kind of mileage you did on the tire with the crapped out bearings.

If it doesn’t solve your issue, at least you have a new tire and you eliminate one more factor from the diagnostic process.
Thanks for the post/thought.

Yeah, backs up where I am on this, that was the conclusion I came to but that the tyre does look OK and it's perfectly firm and good braking under 50 so I'm concluding an interaction between the tyre wear and the bike, hence I was thinking I'll have a go at re-oiling the steering damper. I'm a bit limited on the oils I have available at the moment, I have just the 10W//40 engine oil to hand.

At least I will check if there is any damping at all, I did notice the steering felt 'floppy' and turned in to corners a bit too quick that'd I'd exepect when riding at slow speed but tucked (lowering CoG). I can remove and refit the discs too, just in case someone has left a bit of crap under a bolt face and it is slightly skew. I doubt that, the discs seem to have no runout rotated on the bike.

Mileagewise, I have done about 2k since May, the bearings were shot when I got the bike, it was in a state of neglect, still working through all these issues. So a damper re-oil can't be a bad thing, I think. I'll take a look for 5W fork oil, what do you guys recommend for a 'firm' steering response?

Is it worth be buying tyre levers and doing tyre swaps myself? Garages around here want more than half the price of the tyre to fit them!
 

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I’d do some research before just putting in any weight suspension fluid. Also, you want the damper as “loose” feeling as possible. It’s there to stop head shake if the front goes light. Too firm and you may find yourself in a hedge or worse.

Also, since the bike was in a neglected state, did you check the steering head bearings? As to it wanting to fall into a turn….is it the same in both directions or only one?
 

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Discussion Starter · #16 ·
I’d do some research before just putting in any weight suspension fluid. Also, you want the damper as “loose” feeling as possible. It’s there to stop head shake if the front goes light. Too firm and you may find yourself in a hedge or worse.

Also, since the bike was in a neglected state, did you check the steering head bearings? As to it wanting to fall into a turn….is it the same in both directions or only one?
Head bearings is on the list and not a minor candidate for this issue, but I can feel no adverse movement (and neutral, not biased one way or other). I gave them a pinch up they seemed slightly loose but not notchy or clicky. I do want to get the forks off for a full overhaul though.

So probably buy a litre of fork oil anyway to do that job. Not sure what weight the Suzuki actually is. I'll get fully synthetic 5W or 7.5W I think?

Anyway, took the damper of just now, there is modest resistance, I would not say it is a lot. How does it work, is that the resistance 'at low speed' and a current is applied to the solenoid coil to open it up further at high speed, or is that the resistance at high speed and current is applied at lower, if you see what I mean. I'd say it is 'not very damping' but it's clearly working. The coil measures 13 ohms, which is correct.
 

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Discussion Starter · #17 ·
FWIW, how can I jack the front of the bike up? The manual unhelpfully says 'jack the front of the bike up' when there is nothing but header pipes under there.

I was thinking to make a frame I can drop the crash bungs on to.
 

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That’s probably your best bet. Not a whole lot of other options beyond using a steering neck lift….but then you can’t do much else with the steering head; IE inspect the bearings or lube them or even replace them. Sure, you could do the top ones but the bottoms…..
 

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Discussion Starter · #19 ·
That’s probably your best bet. Not a whole lot of other options beyond using a steering neck lift….but then you can’t do much else with the steering head; IE inspect the bearings or lube them or even replace them. Sure, you could do the top ones but the bottoms…..
Exactly. I can probably hang the bike, but then there are other issues to deal with when working on the head.

I think I'm going to check that now, see if I can suspend it and give the headstock a checkover. Been trying to find tyres today, but don't really want that expense if it is nothing at all to do with it.
 

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Discussion Starter · #20 ·
Well, I made a support stand from some wood strapped together and lowered the crash bungs on to it with the front paddock stand I have, that seems to work well but a bit flimsy. I will make something a bit more rigid, or just get some big axle stands should do.

Anyway, I figure the bearings need replacing as the steering drops into the middle. I took the damper off yesterday to inspect. Not that much I think, it is not notching just a tendency to self-centre. That's not normal, right?

Seems a bit stiffer at one extent than the other.

Damn. Don't like head bearing job. Guess I need to do those first though, right? No point the tyre yet?

So that means .. whether to do the struts too. They are not leaking, can I just swap out the oil and leave the seals? that'll be getting old now.
 
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