Edcase

Right, I have just managed to warp a set of 330mm discs in less than 2000 miles.

I bedded them in religiously, and I and incredibly kind to my car. People always laugh at me because I am so thorough in cooling it down etc. I know all the tricks like leaving the handbrake off. I've also been told by several pretty respected people that I am a smooth driver, and not hard on the car / components like some people.

Which leads me to think the only way to solve the problem is to get more air to the brakes. My car is a 2002 WRX, and I have the STI mesh fog covers, so my idea is to remove the fog lamps, which I never use, and run some motorsport spec ducting to the brakes.

So a few questions:

Has anybody removed their fogs on a 2002 WRX? If so, is it an enclosed pod, or is there a hole at the back of the bumper?

If it is enclosed, would it be easy to make a hole without removing the bumper, and to leave it in a condition where I can refit the fogs if I want?

Where can I find somewhere that sells flexible, strong, heatresistant ducting. The stuff that you bend but then it stays in shape?

Where is the best place to duct the air to? The back of the disc? (ie inside the bell) or the side of the disc (ie front-on)

Any help would be appreciated.

Edcase

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ozzy

Have a look on the Scoobymania site. They sell their own kit, but you can get an idea from the pics.

It's been discussed on here before, so hopefully you can find something using search.

Which discs do you have?

Stefan

Edcase

yeah i did a search already. Couldn't find anything specific enough.

the discs are by a well known rally preparation / tuning company

RayC

normal elephant trunking from Brown brothers or similar should do the trick, make up some nice brackets to hold it

Alternativly, my Type R has ducting already there, one of the slots under the indicator is a hole and a nice platic channel guides the air,maybe you could use somehting like this?

any air infront of the disc into the vents between the two surface areas may help.

in my experince bedding is mainly for pad life and effectivness not to prevent disc warping, disc warping is cause by Disc Torque Variation, maily caused by run out changes - i.e the disc is not flat onto the hub, i would suggest using a run out guage to insure less than 60uM of variation across the disc when fitted

pain i know!!

Edcase

Interesting, I had thought it would sit perfectly flush on the hub. Bearing in mind the car is only eight months old.

So how would you adjust it if it was sat slightly wrong on the hub?

Thanks for the reply

ozzy

usually it's due to the hub surface not being flat/clean sufficiently.

Actual disc warping is extremely rare and any excess vibration is usually uneven deposits on the disc surface. This can be fixed if it's not that bad.

I assume your Prodrive (correct me if wrong) discs are the single cast type and not seperate disc/bell. This would further aid cooling.

Stefan

Edcase

Yes they are one piece. I believe 'they' don't do a 2 piece for this kit.

yet.

just looked at the car, there is no real way to get effective piping to the discs without cutting into the inner arch. And I'm not doing that.

Blue_Boy

Well I've warped (and they were warped), 3 sets of dics now - all Brembo's. I'm dreading getting them again on the new car, although I've never had any problems with the brakes on Scoobies - just Evo's.

If you've seen 2fast2furious (I know it ain't good, but it does have one thing to show), the sklyine with the rather nice venting air from underneath.

Well you can get this kit (purge valves) and mount it under the car so it'll cool the brakes if you want to. It ain't automatic, so not as perfect as the air stream your going for, but an idea all the same.

Wizards of NOS sell them on their website - it's CO2 spraying and the nozzels are ajustable to spray anywhere (not directly on the discs I'm told as it's too cold for that).

dela

I have experienced what I thought was warping, but as someone mentioned above, was actually pad residue build up from the Ferodo DS2000 pads I was using. I switched to Pagid Blues and after a couple of hundred miles the residue was gone, along with the disk-warp like vibrations.

So, it might be worth trying some more aggresive pads?

Edcase

I actually think they may be ds2000 i am using. will look into the c02 thing.

thanks guys.

Edcase

PS im fairly sure they are warped as it only happens when they get hot and expand, which exaggerates the warp?

MadGrip

just a word of warning

I remember reading somewhere that modifying the brake cooling can cause problems , as uneven cooling (ie colder on one side than the other) can cause the discs to warp.

if i an remember where i read this i'll try get a link

dela

MadGrip - I remember reading the same thing - I think it was in a post by Pete Croney of ScoobySport. IIRC, the suggestion was to direct the cooling pipe to the hub rather than the disk surface.

johnfelstead

cooling ducts should always feed the eye of the disk, not the surface as the disk acts as a centrifuge and spins air from its centre out through the cooling viens.

Put a dial guage on the disk to test for warp, its more likely to be pad material buildup.

fuz

you know u want them

Floyd

iTrader: (9)

Ed, read the Stoptech white papers for some interesting info on this.

I believe it is also pad deposit build-up and not warp.

DS2500 and seperate disc bell design should sort it. I saw a distributor at JAE last w/e that sold a 2 piece disc that fits as a direct replacement to your calipers and brackets for about £400. I was going to go the same route a while ago but couldn't get them into the UK from MRT, now that's changed.

F

RayC

Sorry for late reply!!

If you want to adjsut the run out to remove Disc torque variation you need to move the disc round one wheel bolt hole, sometimes this means you can't use the retaining screw , you will in therory on an Impreza have 5 differnt locations for the disc.

If it is only hot when the judder occurs, then it is a long shot but you may have a bad set of discs - hear me out this will take some explaining!!

When the disc is cast, and subsequently machined, it is vital that the air gap between the two contact areas is the same, if not, when the disc is machined it will be perfectly true to the hub and have no significant run out, but one of the disc contact surfaces will be thicker than the other, if you imagine (you need to imagine as you won't be able to see it!!) looking at the side of the disc down the venting vanes the whole disc looks like 2 discs stuck together, well the problem is one half of the disc is thin at the top and the other is thick - like having two triangles next to each other, when put together they make a square, this will cause a diferent rate of expansion in the disc and will cause coning of the disc, as this happens accross the whole disc it creates hot judder, which then goes when the disc cools.

i know this is not a clear descrition, but it is hard without pictures and i am not computerised enough to put some in!!

put another reply if you need me to try again at explaining!!

Cheers

Leslie

That explanation is clear enough and very interesting. I should have a close look at the disks and if they are made unevenly the firm should replace them.

Les

RayC

It will take some measuring, it may be possible with a Vernier guage, take some measurements at strategic points at least more than 10 around the disc, you will need to measure both contact areas (from the inside of the vented section to the disc surface) and compare, let me know your figures and i will try to see what effect it will have

Have fun!!

Edcase

Thanks for all the replies, it seems they are going to replace the discs on Monday as after a test drive they agree they are warped.

I am going to try to let them let me keep the old discs and get them taken to an engineering company and measured for any braking surface / hub contact area intolerance.

I think I will also put a new set of 2500 pads on, as I am pretty sure the current ones are 2000.

You might not hear from me for while now as I am going Ice Karting () tonight and then spending the rest of the weekend in a tent at the big chill festival in wales

Thanks again