advice on brakes for track

[ThaCorradoKid]

Hi, I'm looking for some input on brakes for my track car. It's a corrado with a 1.8t swap and built on a tight budget. I drive it to/from the track, and do very occasional street driving. I use it for club events and HPDE's. Run 15" kumho victoracers usually.

First, I had been experiencing a premature DS rear lockup in recent events which i was unable to tune out with my corroded proportioning valve. I bought a new prop valve and 2 new mk4 aluminum rear calipers to fix the issue. I am also due for new front pads, and was considering hawk hp-plus for my application. Is there anything else I should consider? I don't want to swap pads at the track.

For the rear, should I buy the same pads? On one hand I feel like I should to keep the friction variables the same while I try to dial in the proportioning. On the other, since I already experienced rear lockup, and i see many people mis-matching pads for front/rear, I am considering a less aggressive pad back there like a hawk hps. Advice on this? My main fear is that a less aggressive pad may bite harder at low temps and cause some early lap rear lockup, which is exactly what i am trying to avoid..

Advice/experience greatly appreciated. TIA

[mgyip]

Rear lockup is standard fare for FWD VW products of your generation - running a manual proportioning valve will certainly help to dial away that issue but it will be difficult to completely avoid rear lockup.

Hawk HP+ are good pads but your car is a barge with lots of power - 2 things that will turn the HP+ pads into carbon dust in short order. Most likely you'll burn up a set at a single track event. I'd strongly suggest that you re-think the idea of changing pads at the track and look towards Hawk Blue or one of the DTC compounds for track-only use.

With regards to dissimilar pad compounds - I've been running Hawk Blue and now HT-10 pads in the front of my Mk2 GTi with organic pads in the rear. When cold, under heavy braking, the rears lock up...when hot, under heavy braking, the rears lock up. The only time this is a problem is when I had too much rear pad/brake which resulted in a rather lurid spin - there's nothing like facing traffic that's barreling towards you at 100+ mph.

Are you experiencing instability due to the rear lockup? In my case, only under the heaviest threshold braking does the rear start to wiggle. Even so, it's very predictable and consistent.

Out of curiosity, what suspension are you running? Spring rates and bushings? All those have an effect on braking.

[ThaCorradoKid]

Rear lockup is standard fare for FWD VW products of your generation - running a manual proportioning valve will certainly help to dial away that issue but it will be difficult to completely avoid rear lockup.

Hawk HP+ are good pads but your car is a barge with lots of power - 2 things that will turn the HP+ pads into carbon dust in short order. Most likely you'll burn up a set at a single track event. I'd strongly suggest that you re-think the idea of changing pads at the track and look towards Hawk Blue or one of the DTC compounds for track-only use.

With regards to dissimilar pad compounds - I've been running Hawk Blue and now HT-10 pads in the front of my Mk2 GTi with organic pads in the rear. When cold, under heavy braking, the rears lock up...when hot, under heavy braking, the rears lock up. The only time this is a problem is when I had too much rear pad/brake which resulted in a rather lurid spin - there's nothing like facing traffic that's barreling towards you at 100+ mph.

Are you experiencing instability due to the rear lockup? In my case, only under the heaviest threshold braking does the rear start to wiggle. Even so, it's very predictable and consistent.

Out of curiosity, what suspension are you running? Spring rates and bushings? All those have an effect on braking.

Thanks for weighing in.

my car is probably about 2400-2500 lbs and around 200whp/wtq. So for a street car its not heavy or powerful but on the track i guess it is. It's really built to be as simple and "turn-key" as possible while still turning quick and fun laps. I've tried to keep it pretty streetable because it's not a full on race car, and it likely never will be with my time and $ available to spare. she does hang in there pretty well with a few much more extensively built cars however. My last front pads lasted about 20 track days, and they were just a hi-po street pad (can't remember which).

I didn't realize rear lockup was so common on these cars. when i track my s/c-VR6 corrado with street tires, it's never been an issue. Actually that car is biased too heavily to the front with TT brakes up there and stockers in the rear, but thats another story. I obviously don't push it as hard either.

I'm not really experiencing an amount of instability that I can't cope with, but of course it would feel more stable if 1 rear wheel was not locked up and leaving a trail of smoke behind me. more than anything, it's wearing my tires out fast and funky. I could probably brake sooner and a little more cautiously to avoid the symptom but that's no fun.
new bilstein sport dampers with h&r race springs 400#f/260#r. new R32/TT solid rubber rear bushings w/ poly front in the arms. I didn't notice the lockup when the suspension was all oem 12 yrs ago but I also didn't turn laps nearly as fast back then...

[mgyip]

You don't mention the current front brakes but given your wear rate, they're probably quite large for the size/weight of the car. From that, you can probably use the HP+ without much issue - just keep a spare set in your Track Box in case you burn up a set at an event.

Given the weight of the car and the fact that it's street driven, your spring rates are decent. My curiosity was if the front springs were soft, allowing the car to significantly nose-dive.

Back to the original question...there aren't many options to reduce rear lock-up. The bias valve is the most complex but also the most effective - the issue is that you'll have to replumb your brake lines since they're currently designed to work diagonally (LF and RR, RF and LR). In order for it to work with a valve, you'll have to plumb the lines to run front and rear only.

Running organic pads in the rear will reduce lockup to some degree but it will still occur - running a more aggressive pad will only exacerbate the problem. When cold, a semi-metallic would be great because they don't work when cold - unfortunately, that all changes as they get hot. The same goes for all "performance" pads.

Tyre wear will be a bit odd but the rears aren't grinding away too much rubber as they lock up - remember, they're unloaded and while you're creating flat spots, they're minor in comparison to those on a front tyre. Your options are to rotate the tyres frequently or leave the rears only in the rear. As the tyres flat spot, you'll wear enough flat spots that they tyre will ride smoothly (ask me how I know).

For your amusement - one of my competitors used to tell me that he NEVER looked for my brake lights. Rather, he looked for the tyre smoke because that meant that I was BRAKING and not merely slowing down. When one of my crew members decided to obtain his SCCA Competition License, I let him use my POS. He asked "How do I look down the Chute (at Summit Point)?". My reply was 'You're not braking hard enough - there's no smoke".

[ThaCorradoKid]

brakes are all oem sized. single piston calipers on 11" front and pretty small rears.

I also think i'll be ok with the HP+ for now, based on how the front did w/ the old pads. Might keep the old ones on the back since they have plenty of life and should be less aggressive than the hp+.

I did notice that the outside pads were worn more than the inboard pads on the front. I assume that's not a cause for concern? I will make sure to grease the sliding pins when i swap pads, and keep an eye on it.

Yea I think the spring rates are pretty good for what I need. I considered some RSS clubsport coils but they seemed oversprung for my setup, and I had a decent feel for the car on the original dampers+race springs so i didn't want to make too drastic of a change. The front doesn't really dive hard at all when braking heavily. I think I'll just see what this round of changes does and then drive accordingly. I can prob be smoother and cleaner with a little less violent late-braking, and not cost me any time.

I totally know the feeling re: the smokey rear tires. people always approach me in the paddock and say "hey, man in case you didn't know, you're leaving a smokescreen at the end of the straight every lap!"

[ThaCorradoKid]

Just want to update this to keep it informative. So I finally installed all the parts described in the first post and pictured below:

I don't want to count my chickens just yet, but it seems like the problem has been solved, or at least vastly improved. Take a look at the comparison between the old and new oem brake proportioning valve:

The old one was so rusted that I couldn't even flex the joint by hand. So that was definitely the problem. HPP's felt great during the bed-in procedure, and I threw a new set of pagid replacement pads on the rear while i was doing the caliper upgrade. So far, I'm very happy with how things turned out.

[rex_racer]

Isn't the OEM prop valve adjustable? Have you tried adjusting it with the new one?

[ThaCorradoKid]

yes the oem valve is adjustable, but my old rusty one was seized, so it didn't function as intended, and adjustments made no difference. for now, i have the new valve set in the middle of the range, and it feels pretty good based on limited street stops. I won't adjust it until I've put a few laps on it and have a better feel for how its working.

[mgyip]

Yes, be careful which direction you adjust the valve. IIRC, you'll want to push the arm up, towards the body of the car to minimize rear brake pressure - don't quote me on that though since I made an error when I first installed a replacement valve.

To quote a friend driving an AMG C36 (at an MB event), "I thought I'd follow you and see what you were doing in T1...then you were facing me (still on the straight) and I thought that it would be better to NOT follow you anymore".

[notso2slo]

On our 85 Golf chumpcar, we run Hawk Blues front and rear in the dry. Braking is AWESOME! Well balanced, locks up the front first, and breathes confidence into the driver.

In the pouring rain, we ran some random oem pad in the rear with HPS in the front. Also well balanced, and tending to lock up the front first.

At our last event, we ran HPS in the front and Hawk hp+ in the rear. Bad mistake. Trailbraking into turn 3 locked up the rear wheel, and as soon as you let off the brake, the rear would regain traction and pitch the car (a little terrifying when you are headed straight for a wall). Had to switch to straight line braking.

HPS seem to work fine in the dumping rain, but it dried out briefly, and we went through over half the pads in an hour. We're either gonna try HP+ in the front, HPS in the rear, or give the DTC's a go in the front again.

Last time we tried the DTC's, we had an interesting occurance. We broke them in per instructed on a set of rotors that hadn't been turned since we last used them with Hawk Blues. They were in good shape, though, pretty smooth and good thickness left. We ran half a track day on them, and at the end of the day, noticed BOTH of our front rotors were cracked.

Not sure if it was from using used rotors, or just that the DTC's are hard on rotors. We liked the feel, excellent stopping power with improved modulation, and matched well with Hawk Blues in the rear. We'll have to test again with new rotors.

85 GTI all disc with mk3 front spindles and 10.1" brakes. The proportioning valve is stock and tested in working order. H&R race springs with Bilstein struts and Direzza Star Spec tires.

On my stock engine mk3 GTI, I run HPS all day, and just swap the fronts for Blues when I get to the track. The car has ABS (disabled), so it has no proportioning valve on the rear beam, but never seems to lock up the rear with that combo. My mk3 runs H&R RSS coilivers with no sway bars, rear springs bumped to 629lb rear and the original 571lb springs in the front. Well balanced when running Bridgestone RE-11's.

[andrewmartinee]

It's really awesome and helpful advice for every one who loves to drive vehicle. Thanks for sharing such a nice information hear. I used to short break on my vehicle so I have problem with linear. So Every 2-3 month I install it.