Issue with front brake shudder & PSA regarding powdercoating

[Mayoisthedevil]

For the past two months I've had issues with shudder/vibration under braking from the front end. The shudder and vibration started after having the wheels powdercoated, and now it has become progressively worse to the point where I feel like I'm one of those mechanical bulls.

A friend had a good suggestion to check the mounting surfaces for the brake discs and sure enough there were gobs of paint build up on them. The paint was so thick it was preventing the disc from mounting flat. I sanded off the paint, and now the disc mounts properly on the wheel. I can't believe I didn't notice this when I got the wheels back. Prior to powdercoating I had rattle canned the wheels myself, and I had the foresight to tape the mounting surfaces. Just goes to show you always have to double-check.

Unfortunately, the vibration is still present, and I discovered a second issue with my calipers. The seals are actually coming out of the bore past the cylinders. I have to think this is what's causing the vibration, but I won't know for sure until I rebuild the caliper next week (waiting on seals).

I've also checked the wheel bearings (they're new after powdercoating), and I checked the disc thickness with a digital caliper. I don't have a dial indicator to check runout, but I find it hard to believe that the disc is bad after 21k miles.

Has anyone seen or heard of a vibration caused by this type of issue/damage to the caliper seals?

 

[greg]

Change those seals NOW, and don't ride the bike until it's fixed. If they are hanging out like that then you could be quite close to catastrophic brake failure. Chance are it's just the dust seal sticking out, if the inner seal had come out then the brake fluid would have leaked out.

I'd say it's very likely that this is causing you problems.

Changing brake seals is fairly easy, get OEM replacements, and use some red rubber grease, and use brake cleaner and a toothbrush to clean them up. I also use metal polish and a soft cloth on the pistons and inside the calliper, and wash the residue off with brake cleaner. I put a smear of red rubber grease on both sides of the seals before refitting.

 

[2007Z6ALL-LED]

So no need to totally bleed/replace the brake oil?

Change those seals NOW, and don't ride the bike until it's fixed. If they are hanging out like that then you could be quite close to catastrophic brake failure. Chance are it's just the dust seal sticking out, if the inner seal had come out then the brake fluid would have leaked out.

I'd say it's very likely that this is causing you problems.

Changing brake seals is fairly easy, get OEM replacements, and use some red rubber grease, and use brake cleaner and a toothbrush to clean them up. I also use metal polish and a soft cloth on the pistons and inside the calliper, and wash the residue off with brake cleaner. I put a smear of red rubber grease on both sides of the seals before refitting.

 

[TownsendsFJR1300]

So no need to totally bleed/replace the brake oil?

I've NEVER seen the dust seals come out like that. Perhaps the previous owner screwed with it.

Agreed 100% with the above post. Pull those calipers off, get the seals and replace. ALL your brake fluid will be drained anyway.

Those appear to be just the dust seals sticking out however they fit very tight in the bore between the pistons. When I did mine the pistons were nice and smooth, no corrosion. You may have some corrosion on the pistons that tore up the seals (just a possibility) and forced them out after tearing them up.. **Those dust seals are likely binding up the pistons, causing them to stick ON, overheating the brakes, etc..

Yamaha recommends brake seal replacement every TWO YEARS.

I've found 4-5 years more realistic.

I've rebuilt the 4 pot calipers on both my old FJR (same as the FZ) and my current FZ. I've done one with brake specific grease on the seals, and the FZ without (just brake fluid-while re-assembling). You'll get packets of pink grease from Yamaha with the seals.

Unfortunatly, Yamaha does NOT address anything about brake grease (or not) on the seals in any of its shop manuals. Perhaps for the rear of the pads, two brake pins, etc...

I prefer brake fluid ONLY as it doesn't attract dirt on the seals. The RUBBER seals, flexing in and out are what's actualy pulling the pistons back in after you release hydralic pressure.

It'll take longer to re-bleed from scratch than to re-build. With your 4 piston pots, an air compressor(even small with about 100 PSI) will make removing all the pistons much easier...

After the rebuild, you should see approx 4 "free spin" rotations, by hand. I'm still getting 4.5 spins or so after 2.5 years..

 

[Mayoisthedevil]

Thanks guys, yep the bike is not being ridden right now. I just need to wait on the seals.

I've had the bike for 1.5 years, so I can't imagine anything the previous owner did messed it up. I'm thinking the initial vibration was caused by the powdercoating, and perhaps that contributed to the problem with the seals. I'm going to pull the old pistons out in the next day or so to get a better look at what's going on.

 

[Mayoisthedevil]

Well I rebuilt the calipers, and the vibration is far less pronounced, but it's still there. The vibration is now more of a gentle pulsing.

I double-checked the mounting surfaces for the rotors and sanded more of the paint off. There is now only the faintest trace of paint in the corners. I'm now thinking the rotors are bad. I did check the thickness again with a digital caliper and across seven spots I'm getting a 0.09 variance in rotor thickness. I'm off to the store to pickup a dial indicator to confirm run out on the rotors.

Does anyone have a suggestion on how to check the rotors off the bike? I want to verify the rotors are bad while eliminating the mounting surfaces as a possibility.

 

[TownsendsFJR1300]

.090" is a BUNCH!

I would bolt the wheel back up W/O the rotors and check the mounting points on the wheel.

There is no disc "thickness allowance" in the manual but should be about nill.

Runout on the rotors (mounted, wheel installed) is .0039"

Not mentioned and worth checking, is the rotor itself. Being a "semi-floating" rotor, it has rivits attaching the inner from the outer sections. You should be able to rotate the rivits (with the gentle help of a pliers) An air compressor will help free up an sticky rivits...

Mounting the rotor to the wheel is also like a cage wheel, criss cross pattern...

 

[Mayoisthedevil]

I should clarify, that's 0.09 mm not inches. I'm using metric because that's what the service manual uses. The spec is 0.10 mm.

How would I check the mounting points on the wheel with the rotors off? Are you thinking of mounting the dial indicator and going from point to point?

 

[FinalImpact]

You're gonna have to be creative but I would want to know the journal where the the rotor mates to the wheel is OK. I guess the hitch is money. Lets say you buy new rotors and find out its the wheel??? Or just check the wheel. - So I would assemble it w/out the rotors and verify the landings. Because the paint went away in layers, it may have wore the landing and the rotors may not run true when bolted down.

Get that dial indicator, some bolts, strapping material (wrap around the fork and leg and pinch it shut with a bolt), then bolt the gauge to the strap.
In the picture below I verified the rotors where true after the tire was mounted. Just to make sure my wheel wasn't dropped.

Checking Rotor runout

From thread above....


FRONT:
Disc Thickness:
Disc Discard limit: 4.5 mm (0.18 in)

***********************************
Checking Rotor Defection:
***********************************

Brake disc deflection limit:
0.10 mm (0.0039 in)

 

[TownsendsFJR1300]

I should clarify, that's 0.09 mm not inches. I'm using metric because that's what the service manual uses. The spec is 0.10 mm. Ok, thanks..

How would I check the mounting points on the wheel with the rotors off? Are you thinking of mounting the dial indicator and going from point to point?

Exactly!!!

You're gonna have to be creative but I would want to know the journal where the the rotor mates to the wheel is OK. I guess the hitch is money. Lets say you buy new rotors and find out its the wheel??? Or just check the wheel. - So I would assemble it w/out the rotors and verify the landings. Because the paint went away in layers, it may have wore the landing and the rotors may not run true when bolted down.

Get that dial indicator, some bolts, strapping material (wrap around the fork and leg and pinch it shut with a bolt), then bolt the gauge to the strap.

Just as Randy goes into more detail above ^^^.

As noted previously, get a good micrometer for checking the thickness of the disc (I have to doubt thats the issue).

**Did you ever bolt the disc's over the powdercoat surface?**

If so, its possible the coating wasn't completly even and tightening the rotor down (critical as it should be done in a criss cross method) may have damaged the rotors slightly bending the center. Of course, if its slightly off towards the inside, the worse it'll get the farther out (where the pads work) it'll be..

 

[FinalImpact]

Most of us (self included) have nothing large enough that is true enough to check a rotor.

In short; a machine shop should have a table that is known to be flat (0.00001").

An option with a known flat surface (hint glass is typically not good enough), would be place something under the mounting registers and space the rotor off the surface say 0.050". Then take a "minus" Pin gauge of 0.050" (or a "plus" pin gauge of 0.049" and verify it rolls under the rotors surface without making contact. You might want to take into account the wear on the rotor.

MUST HAVE:
1) Known level surface
5) Pin gauges for spacing rotor off the surface 0.0500" "plus" size (Cheap and common)
1) Pin gauge of 0.0490" to roll under rotor. Might grab a 0.0480" too.

This would be a "GO/NOGO" type test.

Samples: Pin Gauge Pictures

*******************
Checking the WHEEL
*******************

Here is another idea to check the wheel. It could be done at home without a dial indicator. Same concept tho. Using some strapping material, wrap it around the fork leg and anchor a blunt roll pin punch (Pic of Roll Pin Punch leaving say a 0.025" gap between the end of the punch and rotor surface landing. Now insert "feeler gauges" between the end of the punch and the landing where the rotor resides. Rotate the wheel and insert feeler gauges to determine the space between the punch and the rotor landing. You will have to push the wheel all the way one way while doing this to get the slack out of the bearing.

Does that make sense? Let me know if you have questions....

EDIT:
Also notice in this pic my gauge is held to the beam by a strap. Shown is a magnetic base, but the aluminum fork tube doesn't offer much holding power so the axle bolt combined with the clamp was just enough to hold the base.




As for using that punch; i bet you could also use the quick clamp like above, then vise grip a punch to the clamp and use that to hold the punch on the fork tube.

 

[Mayoisthedevil]

OK, here is what I came up with. I bought a clamping dial gauge and checked the disc run out as well as the mounting flats.

Installed on the bike the rotors have over 0.005" of runout (Note back to SAE here because I couldn't find a metric gauge).

The mounting flats don't have more than 0.002" variance from flat to flat. I checked the flats in three location (outside of the mounting hole, inside of the mounting hole, and as close to the inner lip as possible). I have no idea what the spec for this is, but I feel the mounting flats alone are unlikely to be the issue.

I took a video, but as you'll notice in the video I must have bumped the gauge ever so slightly because when I circle back to the starting flat it's now 0.001" off the first reading. I did this many many times and when I was being more careful off camera I as able to get readings within 0.002" across all five flats.
Checking mounting flats for brake disc - YouTube

I also clamped the dial gauge to my workbench and tried to check the disc itself while off the bike. I realize this isn't the best way to check it, but I was able to achieve consistent readings. I would rotate the disc slowly stopping at every outer cross drilled hole while ensuring the disc was sitting in the same spot on the bench each time. Using this method I came up with over 0.006" of runout.

To answer a few questions.. Yes the rotors were installed on the bike with the coating. I always torqued them down correctly using a criss cross pattern. I agree the powdercoating likely ruined the rotors, either by torquing them out of spec or possibly they were overheated when the calipers were sticking.

I have a friend that's taking a machining course. I'll check with him to see if the college machine shop has the equipment to check the rotors as FinalImpact suggests, but that would mean waiting at least a week.

I think I'm just going to order the new rotors and hope that solves the problem.

 

[FinalImpact]

The mounting flats don't have more than 0.002" variance from flat to flat. I checked the flats in three location (outside of the mounting hole, inside of the mounting hole, and as close to the inner lip as possible). I have no idea what the spec for this is, but I feel the mounting flats alone are unlikely to be the issue.

^^ could this be the amount of play in the wheel bearings?

I also clamped the dial gauge to my workbench and tried to check the disc itself while off the bike. I realize this isn't the best way to check it, but I was able to achieve consistent readings. I would rotate the disc slowly stopping at every outer cross drilled hole while ensuring the disc was sitting in the same spot on the bench each time. Using this method I came up with over 0.006" of runout.

Just a thought; could perhaps use a flat ruler and feeler gauges???


Measured mine on the bike:
Inner - Outer radius:
RS = 0.0002 - 0.0004"
LS = 0.0008 - 0.0013"

 

[Mayoisthedevil]

^^ could this be the amount of play in the wheel bearings?

Possibly, The wheel bearings are new as well.

Just a thought; could perhaps use a flat ruler and feeler gauges???

I actually might have a straight edge lying around somewhere that would work. I'll have to rummage around for it.

 

[TownsendsFJR1300]

Something I just tripped over in the FSM (looking for something else re brakes).

Yamaha, if the rotor run out is beyond spec's, recommends ROTATING the DISC one set of holes and re-checking

IMO, definitly worth a try...

 

[Mayoisthedevil]

Well after a long delay from waiting for rotors and being out of town I got the bike back together, and it's fixed! The new rotors make it feel like a brand new bike. The old ones were totally shot.

I still can't say for sure what caused the rotors to go bad, but I'm assuming it was a combination of the powdercoating and excess heat from the sticking calipers.