First autocross with new setup done - first impressions.

[Jean]

Attended my first autocross today with SCCA with the m60 swap and thought I'd share my initial impressions here. It's been about 5 years since my last autocross, so was a little rusty and re-learning the car now with more power. Car was previously competitive locally with the M30B35 swap on Dot R 225/50 tires.

Little bit about the current setup to get that out of the way:

- 26xx lbs with full interior and 3/4 tank of gas. I tend to keep the gas tank at least 1/2 full as otherwise fuel starvation shows its ugly head. front / rear balance weight is 52/48.
- ground control coilovers / custom valved shocks / ground control race camber plates and rear shock mounts , cabrio front sway bar.
- late model 325i strut housings/ brackets / calipers front/rear etc.
- currently using medium case 3.46 diff custom built for more lockup
- trm 15x8 c1 e30 wheels and kumho v720 street tire in 225/45 size.
- stock / rebuilt 4.0 m60 swap, 5speed trans and ttv single mass flywheel
- garagistic pedal box bracket / wilwood pedal box and masters

So, I was going in today with low expectations now that I've driven the car for a few months and learning it's weaknesses. So let's get into that in more detail

Quick video from one of the runs - https://www.youtube.com/watch?v=ih7Dsiz88TQ


Brakes are WEAK, I am talking so weak that I had to break super early and would miss corner apexes as the car needed yet more distance to slow down before turning. I went with the recommended masters, dual 5/8 and the balance bar is set at dead center. I can't even lock these summer tires, vs with stock brake booster and oem master I had no problem with slowing the car down or even locking sticky dot r 30 treadwear tires. Perhaps I should have gone with 3/4 size masters vs 5/8 or maybe I just need way more aggressive pads. I am not sure what's out there for stock e30 calipers, but maybe something like Hawk pads (used them before on GTI/R32)? I need much much better bite here.

Traction is hard to come by. First gear is useless, so all my standing starts were done in 2nd gear. Shift up to 3rd and pretty much run the rest of the course in 3rd w/o any issues with bogging down as the current 3.46 and zf 5speed gearing is short.

Gearing - 2nd gear maxes out somewhere in the low 50 mph range, not ideal and requires upshifting to 3rd. I have not had a chance yet to swap to 3.15 to see how things improve with that, but that's on the list of things to do.

Steering - no issues here,I really really like the e46 330i rack that I got from the RackDoctor... I am using PS so no issues there. Transitions and small corrections are instantaneous vs the old stock e30 rack.

Power - to be honest, no complaints here yet. Starting in 2nd gear if you aren't careful with the throttle easily results in wheelspin. Anything more than 3/4 throttle in 3rd easily results in tail-end of the car loosing traction and wanting to swap ends.

So - overall disappointing, but expected. Tomorrow I'll go back out there and might get a video of the car running on the course.

Any recommendations specifically for making the brakes work AT LEAST with the same OEM braking power are welcome. I am thinking I should try aggressive pads first, and if that doesn't fix it then I am not sure if it's worth swapping to perhaps wilwood calipers ? (don't recall if they make anything that bolts up to the e30 strut housing and works with stock rotors? ) Otherwise looks like I'll probably have to get rid of the Garagistic/Wilwood setup and go with something else sooner than I thought.

Traction will be dealt with another set of wheels (15x9/10) and 245+ dot R tires.

My biggest concern right now is to get the car to slow down, this is really hindering my ability to drive the car to it's potential.

Cheers!

[kronus]

aggressive pads don't necessarily brake better, they just don't degrade when they overheat.

for more braking force, you want smaller masters, not larger. Might want to play with your balance some as well. Proportioning 50% F/R isn't typical, since the car's weight distribution shifts forward significantly under braking.

[Jean]

Hmm, well years ago I did try hawk hp+ (Going by memory ) and testing back to back doing 60-0 stops did yield improvement in stopping distance .

So, smaller masters will push less volume for the same amount of travel but will need less pedal force vs. larger masters will need more force . Correct ?

I mean I didn’t guess on MC sizes , went with what Garagistic recommended and also did check with wilwood as well.

[kronus]

Hmm, well years ago I did try hawk hp+ (Going by memory ) and testing back to back doing 60-0 stops did yield improvement in stopping distance .

track pads will work better than duralast whatever-autozone-sells-for-18-bucks pads, sure.

So, smaller masters will push less volume for the same amount of travel but will need less pedal force vs. larger masters will need more force . Correct ?

yup

[FredK]

The balance bar set at the middle is fine for a starting point.

Stock E30 (48mm F / 33mm R) calipers result in a 67% F / 33% R brake bias when using the same size master cylinders. I believe since you have an early 318i, there might not even be a knee valve in your braking system which serves to further bias the brakes to the front.

Pads with better cold bite are a good idea. Usually these aftermarket pedals allow you to adjust leverage ratio, I would max that out at 6:1 if you haven't already. Otherwise, welcome the fun world of manual brakes!

[Bimmerman325i]

I'd recommend a set of HP+ (or the new DTC-30) for pads, but that doesn't sound like the root cause of your issue. I also would not recommend either of those compounds for significant track use, or street use if squealing is unacceptable.

As for diff...what ratio will put you at 60-65mph at redline in 2nd? Go with that one. That will cover the vast majority of courses except the super fast ones that would need 3rd gear anyway....just be comfortable riding the limiter if/when you need to avoid a 3rd up/down shift.

I would recommend against going to a DOT R tire just yet. Figure out your traction issue first, otherwise you're just slapping a pricey band aid on it. You might need to replace clutches in your diff, or adjust shocks/springs/bars/alignment etc. Much of my traction issues (S54+E36+street tires) went away when I went to a diff with fresh clutches and then really went away after some spring/shock fine tuning.

[Jean]

The balance bar set at the middle is fine for a starting point.

Stock E30 (48mm F / 33mm R) calipers result in a 67% F / 33% R brake bias when using the same size master cylinders. I believe since you have an early 318i, there might not even be a knee valve in your braking system which serves to further bias the brakes to the front.

Pads with better cold bite are a good idea. Usually these aftermarket pedals allow you to adjust leverage ratio, I would max that out at 6:1 if you haven't already. Otherwise, welcome the fun world of manual brakes!

Hey,

There was a delay valve or whatever it’s called going to the rear brakes via the 3rd hard brake line coming off the stock master (non abs master in my car had 3 outputs, two for the front and one for the rear). After talking to wilwood they recommended removing it and I replaced that valve with the 2in 3out wilwood valve . It basically takes the two individual inputs from the masters , one is then split for the front two calipers , and the line from the 2nd master is where this valve allows you to dial off the rear brakes . Currently it’s wide open as a starting point , and I have not dialed it back as I have lack of braking power as is.

The wilwood pedals don’t have adjustability for the leverage ratio, it’s a fixed ratio in the recommended range .

[Jean]

I'd recommend a set of HP+ (or the new DTC-30) for pads, but that doesn't sound like the root cause of your issue. I also would not recommend either of those compounds for significant track use, or street use if squealing is unacceptable.

As for diff...what ratio will put you at 60-65mph at redline in 2nd? Go with that one. That will cover the vast majority of courses except the super fast ones that would need 3rd gear anyway....just be comfortable riding the limiter if/when you need to avoid a 3rd up/down shift.

I would recommend against going to a DOT R tire just yet. Figure out your traction issue first, otherwise you're just slapping a pricey band aid on it. You might need to replace clutches in your diff, or adjust shocks/springs/bars/alignment etc. Much of my traction issues (S54+E36+street tires) went away when I went to a diff with fresh clutches and then really went away after some spring/shock fine tuning.

I think hp+ is what I’ve used before on another vehicle , I don’t mind the noise as it’s not a daily driver .

3.15 won’t get me to 60-65, I’ll have to source even lower gearing to get that high in 2nd . I don’t mind actually using 3rd, there is enough torque to use it on the course and not have to downshift to second . That worked out better for me than running in 2nd (for 75% of the time ) and fighting for traction vs 3rd.

Keep in mind I’ve ran on dot-r tires last season, suspension has already been dialed in and the current diff was rebuilt and had fresh and extra clutch discs . Let’s say car was fast enough to win local street modified championship with m30b35 with the current diff and suspension on v710 and a6 tires , that was against v8 mustang on huge dot r tires and street modified Audi TT also on race tires and double adjustable suspension and huge brakes . Only mentioning this to help clear the details that current braking is worse than it was with stock master and booster with same suspension / same calipers / same rotors ...difference is current pedal box/ masters ..and when before I had enough power to lock up on sticky tires I can’t even come close to doing that on 200 treadwear summer tires (v720).

The issue currently is I can’t slow the car down fast enough, I have to give myself a lot more space than otherwise is necessary and am loosing time .

Not worried about diff or tires at the moment , my main concern I am trying to fix here is lack of brakes .

Going with bigger masters probably isn’t the right thing here as my pedal is hard past the initial 1” or so of movement . I’ve confined all 4 calipers are working (all lines and calipers are new/rebuilt ). Going with smaller masters may be the ticket, but i am also trying to understand if I can fix the issue by going with different front calipers (wilwood 2piston) instead of changing the masters as it’s a HUGE pain in the ass to remove the steering column and drop the pedal box to make any adjustments or changes there. As it currently sits after running 8 runs over Saturday and Sunday I could not once lock the tires up and instead was running out of space before corner entry ..

[kronus]

start doing leg presses :)

[FredK]

It appears the Wilwood pedal assembly that installs onto the Garagistic pedal bracket is Wilwood 340-11299, which has a 6.25:1 leverage ratio. That's about the maximum leverage you'll get from a manual pedal assembly.

You shouldn't have to reduce rear line pressure using the adjustable proportioning valve. I would try one more turn on the balance bar towards front bias in the system so that you get more weight shift forward during braking, which might help you feel a little more confident during braking.

You may want to move to an E34 remote booster setup, that's probably the cheapest way to get the assist needed for E30 stock brakes. Otherwise, you're probably looking at getting something like a Massive BBK to get better hydraulic advantage.

[Jean]

Hehe �� only took this long for leg presses joke :)

One of the local national scca champs offered to help me look over the current system and compare it with his (he is using manual brakes in his c4 vette , Tilton stuff but should be comparable ) as to compare how my pedal feels .

One concern I have is that perhaps firewall is flexing too much, for street driving it gets the car to slow down but when you really need to stand on it it’s not even close to where it should be. But, I don’t reallt have a good reference point with regards to manual brakes so hopefully this or next week I’ll have that .

After reading and googling as much as I could find on this topic there have been mentions of switching to different calipers that won’t require as much volume and this way you can gain the clamping force and in the end get more braking power ? Any thoughts on this ?

If none of this crap works and I have to drop the steering column and the Garagistic / wilwood pedal box down one more time it’s going up on eBay and I’ll buy the floor mounted Tilton 600. This way I’ll eliminate any Firewall flex issue (will check for this first this or next week as that is on the list ) and gain the ability to actually adjust the balance bar and swap masters easily vs current setup. It’s unfortunately too late for the remote brake booster setup like e34 with the engine and everything else already in the engine bay :/

Thanks for all the input so far !

[FredK]

Yes, switching to calipers with larger bores will reduce pedal effort.

I have an E30 M3 braking system with 54mm F / 38mm R caliper pistons. I changed out to calipers with 57mm F and 40mm R in order to reduce brake effort.

I did a cursory search of what calipers are out there on Rock Auto. You may be able to use a Girling caliper from a Mercedes 190E, or a 1987-1993 Saab 900, both of which have a 54 mm front piston and 22mm thick rotors. The bracket looks like it *might* match up to the E30.

The way I matched up candidate calipers was to use the brake pad shape and cross-reference it to other cars that used the same pad on Rock Auto.

Out back, there are fewer options. A 1988 M5 has a 35mm rear piston, again, not a huge reduction in brake force, but every bit helps.

What I'd do is to go to Auto Zone or wherever has these calipers in stock, and bring in your calipers, and see if the caliper will assemble onto the carrier.

[Jean]

Fred - that's really cool! I just learned about the option to run e34 calipers, using audi/tt rotors so that might be another possibility (pending that they clear my wheels).

Have you ever by chance measured the hydraulic pressure going to the calipers with a gauge? I am curious what you are getting since your brakes seem to be working fine so I can have some factual data points to compare against.

[FredK]

I have not measured the pressure.

I use the spreadsheet available at this link

http://www.gt40s.com/forum/gt40-tech-chassis-brakes-tires-wheels/35856-spongy-pedal-new-wilwood-setup.html

in order to go through my assumptions.

For a stock E30 braking system running low-ish mu pads, say with a mu of .35, you're looking at a pedal effort of around 135 lbs, which is pretty tough to press and also maintain some level of modulation. If you get better pads you can reduce the pedal effort big time.

My pedal effort is around half of yours (around 60 lbs) by using pads with a higher mu (around .5) and calipers with a much larger piston diameter. The slightly larger diameter rotors help a touch, but not nearly as much as the larger piston calipers and higher friction pads.

[shootnjunky]

Not sure if this will hurt or help lol

After my s52 swap I tried the rx7 brake kit and didn’t like the feel.

I updated to the larger master cylinder (can’t recall but I think .25)

Kept the vow corrado machined rotors 280mm

Bought the massive caliper brackets for the smaller wilwood 4 piston setup

Run hawk hp+ pads

Now I have firm feel from initial press and when I really stomp no flex and just flat out stop.