New brake discs - warped? How to solve? Machining worth it?

[TTommy]

Hi chaps,

I've just bought an S2K (epic cars, first ever Honda)


The previous owner had fitted new mtec discs & ferodo pads all round approx. ~500 miles ago.

He said he bedded them in for around 250/300 miles, then did 1 trackday.


Now, braking from high speed / hard I can clearly feel the brake pedal pulsating and feels like the front discs are warped. It is thought they may have been overheated from on the track.


Anyway - is the best thing for me to do just straight out replace the discs? The pads should have plenty of meat left on.

Or... I saw online you might be able to get them machined down and straight again - never done this or heard about it - so not sure if legit?


Someone also suggested the discs won't be warped and it will just be 'pad material' stuck on the brake disc. Though I would have thought I would be able to see this - or maybe not haha?


Thoughts from people with actual experience would be most helpful!

Cheers,
T

[GreenV8S]

Replace the discs. They're cheap, it'll fix the problem.

You might be able to recover the discs by sanding with garnet paper but it's really not worth the effort given how cheap decent discs are.

[TTommy]

Thanks buddy.

I thought that may be the case, just lack of actual experience fails me on this.

Cheers man!


Forgot to mention, I think the wheels might be on small spacers too. I'll check it out. (Only owned it a day!)

[GreenV8S]

I recommend you take the opportunity to clean the calipers and flush the brake fluid while you're in there. I'd also recommend that you get a new set of pads and plan to replace those too. If they've been overheated badly you may well find they're worn unevenly and/or heat damaged and will compromise your brakes until replaced. You can always keep the old ones as spares if you decide they're OK afterwards.

[Ray Luxury-Yacht]

Rather boring interjection so forgive me, but it is accepted that there is technically not such a thing as warped discs - especially on road cars.

Here's an interesting explaination

[stevieturbo]

Anyone who says you cannot have, or warp discs on a car is a fool. Even more so if using for trackdays with harder than standard pads on standard or substandard discs.

But yes you can get discs skimmed, but most are so cheap replacement is just as handy. If they were more expensive, then machining can become more viable.

[Mr2Mike]

Ray Luxury-Yacht said:

Rather boring interjection so forgive me, but it is accepted that there is technically not such a thing as warped discs - especially on road cars.

It is not accepted, technically or otherwise. Pad deposits etc. may be a more common cause of juddering brakes, but to suggest a disc can not warp is just silly.

[Ahbefive]

Indeed, brake discs certainly can and do warp which is why there are tools and methods for measuring this and companies that willl skim discs flat again.

[anonymous-user]

Mtech discs (in my opinion) are cheap rubbish people normally buy them because they're the cheapest drilled and grooved discs.

Get some decent oem discs and pads, or opt for a recognised upgrade for the s2k.

[GreenV8S]

BAM225 said:

cheapest drilled and grooved discs.

I'm not familiar with MTech, but drilled discs (especially cheap drilled discs) are a bad idea for anything except show cars. Grooved discs may be necessary on cars with brake overheating problems but should IMO be treated as a solution for that specific problem and not a general styling/performance 'upgrade'. It's the performance equivalent of stick-on carbon fiber film to make the car look more 'motorsporty' without actually achieving anything. Except that plain discs actually work significantly better than grooved discs, if they aren't overheating.

[anonymous-user]

GreenV8S said:

I'm not familiar with MTech, but drilled discs (especially cheap drilled discs) are a bad idea for anything except show cars. Grooved discs may be necessary on cars with brake overheating problems but should IMO be treated as a solution for that specific problem and not a general styling/performance 'upgrade'. It's the performance equivalent of stick-on carbon fiber film to make the car look more 'motorsporty' without actually achieving anything. Except that plain discs actually work significantly better than grooved discs, if they aren't overheating.

Agree entirely with your post, and continues what I was saying.

Tat.

[TTommy]

Oh right.

Thanks chaps. They don't looked massively grooved like normal cheapo's. I'm trying to find them on ebay now but can't see anything similar.

These ones don't have grooves as such, they have what looks like a fishing hook - imprinted around them as (drilled) holes.


Perhaps a starting point would be for me to clean them with some rags and break cleaner?

Is there any implications in running different discs on the front to the back?

As you have said, I'll just get some better ones or OEM. Don't need to be drilled/grooved for normal driving or fast road at all.

Thanks all.

[Krikkit]

Are you going to be using the S2K on track? If not I'd replace with standard pads and discs and see how you get on.

Wave cuts in discs are the best pattern as a compromise for cooling/strength (drilling is, generally speaking, frowned on unless you're using super-expensive discs in proper motorsport application)

[WinstonWolf]

TTommy said:

Oh right.

Thanks chaps. They don't looked massively grooved like normal cheapo's. I'm trying to find them on ebay now but can't see anything similar.

These ones don't have grooves as such, they have what looks like a fishing hook - imprinted around them as (drilled) holes.


Perhaps a starting point would be for me to clean them with some rags and break cleaner?

Is there any implications in running different discs on the front to the back?

As you have said, I'll just get some better ones or OEM. Don't need to be drilled/grooved for normal driving or fast road at all.

Thanks all.

Go out, find a quiet bit of road and do about half a dozen repeated stops from high speed to walking pace. Drive around for ten minutes to allow the brakes to cool and see how you get on. Chances are the problem is pad deposits, not warping.

[V8mate]

The OP says he has been braking hard from high speed... could he simply be feeling the ABS actuating?

[TTommy]

V8mate said:

The OP says he has been braking hard from high speed... could he simply be feeling the ABS actuating?

Actually, funny you should say that.

Today I noticed I can feel it at low speed <10 mph. Just on the pedal. It must be the discs/pads haha!

[The Wookie]

OP, generally speaking a decent quality set of new discs will judder for three reasons:

- pad deposits
- dragging caliper causing DTV
- hub mating surface damaged or corroded

First thing as suggested is to try rebedding with several 60-30 moderate brake applies followed by a few miles of cool down off the brakes as much as possible

Next is to jack the car up and see if the brakes turn freely (obviously driven wheels won’t be as free but should be able to tell if it’s brake drag), if there is any drag then calipers need rebuilding or replacing when you replace or skim the discs

Finally if it’s poor hub surface then skimming them will cure the problem but it will return on the next set of discs unless you make absolutely sure the surface is cleaned with a wire brush and scotch brite.

Two more things are also worth considering:

- a crap quality set of discs may judder for no reason
- worn bushes make a car considerably more sensitive to judder to the point where it may appear when there’s no real issue with the brakes