Why can't I trail brake?

#1

Am a newby Spec E30 driver. Have HT10’s in front and Mintex OEM’s in back. Rear brakes don’t seem to do much. Car doesn’t seem to want to trailbrake, and I’m thinking that maybe the Mintex pads don’t have as much bite as the HT10’s. It’s so prevalent that a couple times I was trying to trail brake and the fronts chirped.

Am I doing something wrong, or maybe my pad choice causing this, or could something else be goofing my brake bias?

I should be able to do this. Applying a little trailbraking isn’t rocket science.

#2

I’ve got your same pad set-up and don’t have problems. I’m not sure what you mean by your terminology. "Trail braking" refers to where in the corner you apply the brakes as opposed to a specific bias or set-up. Is it really the bias that you don’t think is correct (i.e. either the front or the back is grabbing more agressively than the opposite end?).

Sasha

#3

First I typically use HT-10 front and rear. That or the new PFC 01’s. When I first built my Spec E30 I ended up not having ANY rear brakes. I replaced everything in the system including the booster and all is well. I would at least start with looking at the proportioning device that is under the master cylinder. It limits the pressure to the rear and if the little hole gets cloged it can stop the pressure to the rear. I took mine apart and it helped but I later replaced it.

Good Luck.

Michael
#36

#4

Sasha, I think that we’re saying the same thing. If you attempt to trailbrake, but your rear brakes aren’t doing much, then little or no rotation will occur. And that’s what is happening.

#5

I can’t get enough rear bias in my car for straight line braking and don’t understand how you could drive with street pads on the back. I ran 01 Front and HT10 rear on my car for about 3 sessions before I had to stick 01’s on all the way around. The car had so much front bias it was terrible. 01 all the way around was much better but I still wanted more(I’d bet on a M20 car it’s be better as I have an advantage in weight distribution). I’ll run DTC-60F and 01R next time to see how that goes. I can’t run HT10 anymore I get too much fade.

#6

I ran the Panther with HT-10’s on the front and street pads on the rear. I put HT-10’s on the back for Barber and couldn’t down shift the car anymore without locking up the rears. I had to push my shift point way deeper. It’s all driving style. I tend to do a lot more engine braking which also probably explains why my brakes never fade.

The next car I build will have streets on the rear. I think it handles better and I stop just as fast as everyone around me seems to be able to. I also have no trouble trail braking with that setup.

Look at rear bar, tire pressures, alignment, driving style, etc. Many factors go into rotation into a corner.

#7

FWIW, i ran HT10s w/ the cheap mintex street pads on the rear and on the third HPDE i was on the backing plates in the rear. Quite wild and a HORRIBLE sound. Fortunately that was the last HPDE of the season, but i’ll be on track pads all around next year.

#8

you’re not going to get longer life out of race pads in the rear if that’s what you’re thinking. Sounds like you have a brake bias problem as the rears usually last a looonnngg time.
cheers,
bruce

Dan Durusky wrote:

#9

Thats what i would think and i’m a bit confused by it as well. The car seems fine. Stable under hard braking, easy to trail brake, etc. All calipers rebuilt, several cycles of fresh fluid through it. hrmmm I don’t know how else to check it.

#10

Dan Durusky wrote:

I had the same situation when I ran the cheap street pads on the rear. They were completely gone in a weekend. The last lap I was down to the metal.

JP

#11

I had street minnteks on the rear and wore them down to the plates after a weekend on the track, about 3 hours.

#12

Run cool willy’s in the rear and you won’t be able to keep the car from trail braking.

#13

Am at the BMWCCA Licensing School at Roebling. One of the instructors told me today that E30’s are extremely reluctant to trailbrake. His point was basically that it’s a better idea to just find a good way to make it thru a corner that doesn’t rely on trailbraking.

Note that I started this thread because I was having trouble trailbraking. I put on rear pads with more bite, but I still can’t trailbrake worth a crap.

I’m also getting advice that I don’t understand. Like why would I want to disconnect my rear sway bar to help me trailbrake. How would adding rear traction help me trailbrake. And heck, the last thing I want to do with this understeering beastie is add rear traction.

So what are your thoughts? Am I wasting my time trying to figure out how to trailbrake this thing?

#14

I’m not sure that I follow your question. Trail braking is simply the application of the brakes during a turn. It sounds like you are trying to rotate the car in the turn by unweighting the rear with the brakes. Some people achieve this with left foot braking but I wouldn’t recommend it on a hot lap without practicing at lower speeds first.

FWIW, I would rather have a little less rear bias for more stability under heavy braking. I don’t like the feeling of the car getting loose at the end of the back straight at VIR.

#15

Yes it is a rotation under braking that I’ve been working on. Am a little leary about left foot braking. A man has to know his limitations.

#16

JP Coates wrote:

[quote]Dan Durusky wrote:

I had the same situation when I ran the cheap street pads on the rear. They were completely gone in a weekend. The last lap I was down to the metal.

JP[/quote]Ditto here in the MA pace car we used it for triple session duty and completely ate up the rears 2 weekends in a row. no more of that…anyway, you guys may want to look into BHP pads as another option. the PR1 (Pro Race 1) compound is available for the E30 and they are pretty good. Matt, from Carbotech is the dude there and has brought his expertise and tremendous customer service to BHP. The CR1 compound is good for HPDE but in back to back sessions I got a little bit of fade. They are designed to work up to 1000 deg. The PR compound is what you want to race on.

#17

I guess there are many different ways to do things but I use trail braking only to extend the braking zone and have no problem doing that in an E30. I use my right foot to rotate the car once I have finihsed with the brakes. When would you ever need to use the brakes to rotate in a corner?

Michael

#18

I don’t find that a Spec E30 is reluctant to rotate under trail braking. I’m not at all good at using it, but I can induce rotation under trail braking any time I want to (and even when I don’t want to…). As I understand the process it is primarily a function of vehicle dynamics, not of the relative front to rear brake bias. If you shift weight from the rear wheels to the fronts under braking you’ve shifted grip away from the rears to the fronts and can then induce rotation.

I might have missed something or misunderstood, but the instructors at Skip Barber’s race schools recommended that rotation under trail braking be reserved for tight, low speed, Type 1 corners (e.g. T7 at Road Atlanta, Oak Tree at VIR, etc). That could include at the re-direct point in a carousel when using a double apex, especially if the exit is decreasing radius. That makes sense to me as you’d get the rotation done at the beginning of the corner so as to be able to launch through the apex onto the straight.

I’ve always run the same pads on the front and the rear and the formula cars Skippy uses are configured the likewise. It does take a deft touch to get a controlled rotation and the greater the steering angle the easier it becomes in my opinion. I used to use HT-10’s but have found that the PFC-01’s yield a slightly better pedal feel and are thus a bit easier to modulate. Per above, I’m not very good at this but the times I felt like I got it right (in the formula cars or the E30) I wasn’t using much brake for the rotation. Certainly well short of chirping the fronts.

#19

Jim,

This is what I was getting at with my first reply. I agree that trail braking is simply braking after you’ve initiated the turn, which is considered a more advanced driving technique than braking in a straight line and then turning, like they teach you in DE.

I agree with everything you’ve said about rotation being a function of vehicle dynamics. As you brake hard, not only are the rears unweighted, but the front has been nicely loaded up by weight transfer and they bite well compared to the back. Brake hard and turn the wheel and the back end comes around. I, too, feel the E30 does this pretty damn well. I’ve used this effectively to get through Turn 4 at VIR and also almost crashed as a result!

Sasha

#20

I suspect this has more to do with alignment and the simple fact you’re coming from a 911 (IIRC).