DISC/brakes advice please. cbr600f 94

[blinky]

hi guys,

one of my discs are worn quite heavily and/or warped i suppose... as im now getting a shuddering in my front braking.

any options?? (other than buying a new one)

can i service the disc by flattening it out? (has some worn grooves more than the other side)

If i buy a new one, im told i MIGHT have to buy 'TWO' new discs AND new pads ...otherwise the front will be unbalanced.

Another reason for me not buying new parts, is this is a run-around high milage bike... so dont particualrly want to spend money excedding the value of the bike, lol

mot only a couple months ago!
pads good.
brake fluid level good.
stopping power still ok.
overcompensating on the back brake at the moment, but i know this is ill-advised.

any help, hugely appreciated,
Cheers
____________________
Better to ask forgiveness than permission!
Oh i miss my first love, the lovely lil CG!
Rouser 135 2012... Enfield 25... Hornet 600 2002... CG125 2000

[MarJay]

Bear in mind this was a Supersport championship winning bike in 1994. It can't really be run on a shoestring. If the discs are within the wear limit, you *may* be able to skim them. I was going to suggest removing the discs and cleaning any corrosion off of the mountings, but if one side is grooved, then it either needs skimming or replacement.

The service limit will be stamped on the disc somewhere, and needs to be measured with a micrometer. My guess would be, a bike from 1994 with scored discs will need new discs. You can't really just replace one, unless you want a 150mph bike with crap brakes.

So yes, buy decent aftermarket replacement discs, replace the pads and while you're at it strip and clean the calipers and replace the brake fluid. If you can't do that yourself, either buy a workshop manual or ask someone who does know. There may even be someone on the forum who lives nearby who can help you. Maybe.
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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]

It already IS unbalanced.

Have you checked that you don't have a sticking caliper - that can cause the disc to overheat and thus warp?

I would just get a good second hand one on ebay etc.
Wouldn't be surprised if you can get a front wheel with two discs for not much.

Whatever, make sure they confirm the disc(s) are in good nick, so you can claim money back if they aren't.

[andym]

Having just done the calipers on a 93 CBR I can tell you it is extremely easy to strip and clean the calipers, also the pads are pennies, but if they are new then you might get away with reusing them a bit longer (I'd put a sheet of 400 grit wet and dry on a flat surface and give them a little rub on that to take any grooves out if there is enough life left in them).

As for the discs, if 1 side isn't too badly warped, but you know where it is then I'd be tempted to try straightening it with a couple of shifting spanners.... as I done this on my old GPz. Although with that I put the discs on a flat surface and went round them with feeler gauges and marked the high bits on the discs. If they are badly warped then it would be easier to just find replacements.

But I'm a cheap biker

[haroman666]

If the discs look worn (look for a lip on the outer edge) then just that's your first port of call... No use spending ages cleaning up brakes that need replacing anyway.

Go buy a micrometer. Shouldn't be more than £15.
Then you can measure the disc thickness accurately and you can do so again in the future.

If the wear is within the limit then look to cleaning up the pads and calipers. A really simple job that requires a 12mm socket and ratchet and a 5/6mm Allen Key, Brake/Clutch Cleaner and a tootbrush. Possibly a flat blade screwdriver too. This assuming the sizes are all the same as mine.

If you need to replace a disc, replace both. Just don't bother doing one side and not the other. Common practice is normally common for a good reason.

And this might seem like an odd thing to check, but make sure your lever pivot bolt is lubed. I have cheap chinese levers that over time develop a strange feel in the lever. I have to pull harder on the lever to get the same braking force I had say 100 miles ago. I've narrowed it down to the lever pivot bolt. Greasing it immediately eliminates the problem.
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The mistresses: 2000 Honda CBR600f, 2000 Honda VTR1000

[Teflon-Mike]

My CB seven-fifty uses the same wheels & brake set-up I believe & I bought that 10 years ago as high-mile hack, with juddery front brake....

Nissin 'floating' calipers are notorious for sticking on the float-pins, & the steel pins corroding in the alloy housing, in damp and salty British climate.

Pull, strip, clean meticulously, and re-assemble with new grease & if you are indulgent seals & pins from Dave-Silvers.

Popping the pistons & fully overhauling the caliper can save a lot of silly questions later, too.

Likely that pistons are rather flakey and seal grooves gummed up, and most brake failures occur AFTER maintenance.

Usual mechanism, is that an old flakey pitted piston, that has spent 3/4 of its life out in the elements, is shoved back into the caliper when new, thicker pads are fitted, often taking a load of shit with it, to make seals stick, and or leave the flakey/pitted bit of piston wall wearing away the tired old seals.

Cleaning up sticky old float pins and letting the caliper actually float like it should, can do similar, begging the pistons travel twice as far as they have become accustomed.

ISTR pistons in those calipers as OE were chromed mild steel, and they do tend to go rather flakey and pitted in British weather; Stainless replacements from all things old Honda aren't exactly penny parts, but overhaul ops to fit'em are a precaution against causing later problems, and they do seem to last well, even on all weather, out-door living owld dawg like mine!

Discs; Off top of my head, they are aprox 6mm thick when new, with a wear limit stamped on them of I think its 4 or 4.5mm; there's not a lot of 'meat' in them to get them skimmed if warped or scored & they are stainless, which isn't so nice to work with in a M/C shop; I have a couple of good engineering co's round me, who will do such scratty little jobs, but loath to take on one of these....

More helpfully, pulling the discs, good chance you may find that the steel disc bolted against alloy hub for twenty years has a build up of corrosion on the mount flange, which 'may'.. and it is just a chance let the disc 'creep' out of true, when its hotted and cooled under load, & stripping & cleaning & careful re-assembly 'might' help take out a bit of imbalence... but if you fit a new disc certainly advisable to make the mount 'good' before you fit it.

Plenty of Cheapo discs on e-bay, including wavy-ones I am utterly unconvinced by. Not wanting to take chances I got genuine EBC's from Dave-Silver's.. they weren't 'that' much more expensive and they have lasted ever since....

It's not an area of a bike to try cutting corners or taking chances with IMO, and as said, it is a 150mph race winning sports motorcycle, not an MZ250 utiliterian commuter hack! & horses for courses, & if you want 'cheap' wheels, it's not exactly the best starting point. "Cheap" old bike like this will only be 'cheap' if you don't use the performance it has to offer... either saving it as Sunny Sunday toy, in which case it's still not very cheap, and the bills might not come in very often, but still sting when they do... or you ride it like an ER5.. in which case you might as well have bought an ER5, 'cos bills are still going to come in, and still sting when they do.
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My Webby'Tef's-tQ, loads of stuff about my bikes, my Land-Rovers, and the stuff I do with them!
Current Bikes:'Honda VF1000F' ;'CB750F2N' ;'CB125TD ( 6 3 of em!)'; 'Montesa Cota 248'. Learner FAQ's:= 'U want to Ride a Motorbike! Where Do U start?'

[blinky]

Wow!, nice one guys thanks.

This morn jus did a few checks...

1. measured the discs w a tape measure for now.
Right disc. 4.2mm ish. (So, on the limit.)
Left disc. 4.5-5mm. Silky smooth!

2. pulled my calipers off, ...ebc pads have loads of thickness left, but maybe deteriorating a little due to age and was sitting outside for 3years previously. Maybe this is what's scoring my disc... or as someone mentioned, a sticky caliper/piston.. putting uneven pressure on the pad?

It was a bugger to push the pistons in!

But there's a noticeable improvement (less shuddering) driving home...after I sanded the pads a little and sprayed the lot w brake cleaner.

I might just sand paper the pads more and see how it feels... then next step would be to service the caliper. ☺

The value of the bike is only about 400quid. So might as well sell it if I can't get 2nd hand discs w or w.out wheel.... il keep an eye out anyhoo.

Anyways, cheers again lads, great info! Hope you all have a smashing bank hol wkend. 😀
____________________
Better to ask forgiveness than permission!
Oh i miss my first love, the lovely lil CG!
Rouser 135 2012... Enfield 25... Hornet 600 2002... CG125 2000

[blinky]

Hi everyone....

I might just replace the worn front rh disc and keep everything else as is....

I'm still getting increasing brake shudder ufortunately. I just wanna make it rideable and safe.. doesn't need to meet top of the line performance.

What do ya reckon?

Cheers
____________________
Better to ask forgiveness than permission!
Oh i miss my first love, the lovely lil CG!
Rouser 135 2012... Enfield 25... Hornet 600 2002... CG125 2000

[MarJay]

[G]

Worth double checking your bearings by the way - knackered bearings can cause a shudder under braking.

You should be able to see any warp in discs by holding a pen or similar on the fork and spinning the front wheel (with it off the ground, of course) - hold it so there's a small gap and you should be able to obviously see the gap get smaller/bigger if it's warped.

[Bozzy]

[tom_e]

[skatefreak]

These look cheap and cheerful.
If you're not pushing the bike hard then I wouldn't worry to much tbh. My buddy is sporting some cheap wavey disks on a gsxr 600 k1 track bike and they have been performing great, no sign of fade/fractures etc.

[Rogerborg]

[blinky]