"Warped discs" and re-using disc bolts

[MarJay]

Hello,

My trackbike ('08 CBR600RR) has an intense vibration through the front end when braking. There is pulsing through the brake lever.

I found that there was a ton of corrosion between the disc itself and the disc carrier which I attempted to clean as best I can. This did improve the problem, but it's still not perfect. Obviously for track use I need it to be right, so I've been bashing my head against a wall trying to sort it.

The discs may well be warped, but the wheels are not in great nick and have a fair bit of corrosion. I'm thinking I should remove the front wheel, remove the discs and clean behind them, and then re-fit. In the Haynes manual it says to not re-use disc bolts, but If I buy a new Honda set, then I'll only have to replace them again if I end up having to fork out for new discs. Do you think it's OK to re-use brake disc bolts? Anybody had success removing and cleaning front brake discs? I know Robby did a while ago, but I wondered if anybody else had any experience?
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British beauty: Triumph Street Triple R; Loony stroker: KR1S; Track fun: GSXR750 L1; Commuter Missile: GSX-S1000F
Remember kids, bikes aren't like lego. You can't easily take a part from one bike and then fit it to another.

[DrDonnyBrago]

I've had my discs off a few times and reused the bolts. Best and common practice often differ.

I also tried to solve a warped disc by cleaning the corrosion off between the dsic carrier and the wheel, but ultimately it didn't make much/any difference in my case. YMMV ofc.

Maybe check for runout at both the carrier and steel braking surface? See which bit is borked.

[Matt B]

As above ^

Just use the bolts again. Clean the old loctite off the threads (if used) and put some new stuff on.
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[Howling Terror]

Mark-up the bolts when fitted. Quick visual reference aid.
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[MarJay]

For anyone who is interested:

I decided that the corrosion between the disc and the carrier was too much of a faff to clean, and I've booked a couple of trackdays for August so I wanted to make sure the bike was right. I ordered some EBC discs from ebay which were discounted, but then I found out the seller was selling items he didn't actually possess, and that the discs would arrive just before the trackday.

So I cancelled the order and serendipitously found some low mileage second hand OEM ones for a lot less money. I'm going to fit them this weekend. I also replaced the front wheel bearings and seals just in case that was the issue. The left hand wheel bearing was notchy, so that may have also contributed to the issue.

The rear end of the bike is caked in corrosion, so being the bike rides OK apart from the braking issues I'll leave it for now, but I think my winter project is going to be to strip and re-grease the back end and replace any bushes or bearings that need it.

I'm going to re-use the bolts, clean them up with my die set, and put loctite blue on them before re-fitting. I don't currently have any loctite red. I assume loctite blue will be OK?
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British beauty: Triumph Street Triple R; Loony stroker: KR1S; Track fun: GSXR750 L1; Commuter Missile: GSX-S1000F
Remember kids, bikes aren't like lego. You can't easily take a part from one bike and then fit it to another.

[Polarbear]

Loctite blue is nutlock rather than studlock and not so strong. That being said on board ship when I have run out I've ended up using bearing fit instead of either, - never had a problem.
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[kramdra]

You should be using blue, not red.

Buy or borrow a dial guage and measure the runout. Might be wheel.
For my 125 it was much cheaper to buy a used wheel/discs assembly.

[iansoady]

[doggone]

Need to get the old ones out before 'deciding' to re-use.
Usually there is one that has other ideas.

Technically they will have stretched but hard to see a huge risk using again provided you check one or two have not loosened off after a couple of runs.

[RhynoCZ]

[Pete.]

Just re-use the bolts. The only reason they can have for saying use new ones is because they come pre-coated with threadlock. They are the wrong shape and too short to be stretch bolts and they can't possibly have been stressed to or near their yield point because that would render the risk of failure and subsequent liability too high.

Threadlock them in.
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a.k.a 'Geri'

132.9mph off and walked away. Gear is good, gear is good, gear is very very good

[MarJay]

A few notes on this thread so far:

1.) By the time I'd got to post yesterday I'd already completely removed the old discs and replaced the wheel bearings and seals. The disc bolts came out a little too easily for my liking, but they all came out.

2.) I used a steel rule to try to see the warp on the discs. One of them *might* be slightly warped, but I think the issue is more down to corrosion behind the floating disc buttons making the disc out of true rather than warped.

3.) The second hand discs arrived Friday. They were in very good condition, only cost me £100 for the pair and I fitted them yesterday. I cleaned the threadlock off of the original OEM bolts with a die and re-threadlocked them with loctite Blue. The torque in the Haynes book of lies is something like 22nm which is bog all.

So... How does it ride?

F*cking amazing. Really bloody good. I'm surprised people who have these as their road bike/daily aren't all in jail. It's a mental loon of a bike. Admittedly mine has had a lot of the road gear removed and so may be a smidge lighter than OE but sheesh. I was doing 0.1 leptons on an NSL road and realised I was only in third gear! The brakes are transformed. The bike doesn't feel like it wants to vibrate me off over 60mph and I was able to spend a little time trying to run in my new Pirelli Rosso Corsas. It should make an ace track bike. I do need to do a couple more minor things such as give the front brakes another quick bleed and just generally check everything but I think I'm finally ready for a trackday or two.


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British beauty: Triumph Street Triple R; Loony stroker: KR1S; Track fun: GSXR750 L1; Commuter Missile: GSX-S1000F
Remember kids, bikes aren't like lego. You can't easily take a part from one bike and then fit it to another.

[G]

Worth checking bearings too - that can also cause a vibration under braking which you don't otherwise notice.

And yes - reused many disc bolts Ideally some fresh thread lock on it.

[RhynoCZ]

[Itchy]

Thread lock? Doesn't this create a heat barrier and therefore one of the reasons why brake discs warp in the first place?

I've never used thread lock on any bike I've owned so the heat of the discs can conduct into the wheel.

So even when the brakes stick on and I still ride them the discs are fine. Just give them a once over now and again to check they're not loose... though again I've not had any come loose either.
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[haroman666]

[G]

[chickenstrip]

[Itchy]

[MarJay]

[Pete.]

[Itchy]

[sickpup]

[temeluchus]

In any case, a little thread lock is useful insurance for the manufacturer in case someone forgets to torque the bolt down at the factory.
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[sickpup]