First autocross with new setup done - first impressions.

[Jean]

I thought so too, until I went out and spent about an hour with local national SCCA champion and checked out his winning corvette.

He's got a manual setup as well, Tilton pedals and masters. 1" rear and smaller front, and massive calipers. This way his balance bar is almost in center / even position while retaining Front bias..but he tunes it for each circuit using the remote balance bar adjuster.

So, we ran my numbers (pedal ratio, the masters I am using that Garagistic/Wilwood recommended, the front/rear e30 caliper piston and rotor sizes, car's weight and pad ratings etc..) and we came up with my car needing 2x the pedal effort that his corvette to get -1.2g of braking force.

Basically he can lock up his brakes with about 40-50lbs of pedal effort, and this is on HUGE racing slicks on all four. He then drove my car and also confirm my feeling that the current braking performance is complete crap, it's really borderline unsafe so it's got nothing to do with me unfortunately. I am all for having some effort and feel, but I want the car to stop NOW vs. having to give it extra 20-30ft and not being able to lock the brakes no matter how hard I try. The corvette driver also tried to lock them up and couldn't so it's not me, and having done this test (I know the two cars and setups aren't the same but at least I now have some point of reference in terms of what a good working manual brake setup SHOULD feel like) we've confirmed using calculations (he's used the same .xls formulas that was used to setup his car and friends Cobra kit car with great results) that the recommended Masters (5/8") are not even closed to what I should be running using the STOCK e30 calipers. So, to double confirm this, I want to measure the brake pedal hydraulic pressure at each caliper to better understand and co-relate what's happening.

So, my next plan of attack is to get a brake pressure gauge to confirm if the current pedal box/masters are doing what they are actually supposed to do pressure wise. Once this is confirmed, I'll either have to replace the master(s) or whatever the fuck is wrong with this stupid pedal box... Or hopefully there is nothing wrong there and I'll then tackle it from the caliper/rotor/pad area instead.

[squidrope]

While I'm not running your set up I wonder if this could be an issue of you not being accustomed to a non boosted brake set up? We've built a lemons car and removed the booster. The pedal ratio has changed (can't remember to what ATM). MC/Calipers are stock and we're using race pads.

One driver hates the set up and says the brakes suck. Second driver wasn't thrilled with brakes at first but has become more accustomed to them and thinks they work fine. I was initially surprised by the force needed to get the brakes to work as I wanted. But have no problem outbraking others and can lock the brakes at 100mph. I love the brakes.
Same car. Same brakes. 3 different opinions.

[Jean]

Rather not put anything vw/corrado on the car :). Lee has been very helpful over emails, doing some final checking and buying a brake fluid pressure gauge to verify if my wilwood pedalbox and the Garagistic and Wilwood recommended 5/8 masters are working as they should as the current performance is very weak borderline dangerous.

[shootnjunky]

You can actually now buy already machined rotors from garagistic

They are found under the rx7 brake upgrade section.

280mm rotor starts with the vw corrado and is bored out 1mm to fit the e30 hub.

[Jean]

Contacting Massive...

[kronus]

So these calipers have multiple 35mm piston size, with 4 of these that's a significant upgrade from the single 48mm front / 33mm rear.

it's about twice the surface area which should be ~ 2x the clamping force

[Jean]

Thanks man, will check out your IG! You got the brackets for these calipers from Massive?

What did you have to machine, stock rotor hat thickness? Or is this with Corrado rotors?

So these calipers have multiple 35mm piston size, with 4 of these that's a significant upgrade from the single 48mm front / 33mm rear.

[shootnjunky]

I am running these calipers

Wilwood 120-9703 Dynapro 1.38" Piston/.810" Rotor Billet

I have 2 sets of wheels 15 and 16" both +20 and I run 4mm spacer front and 8mm in rear.

I had to have the front one machined to make up the rotor hat difference in thickness about a mm.

you can see some pics on ig @vntg_e30

[Jean]

Yeah, slightly different scenario in your case as you are still using stock pedals and booster but I am curious about the wilwood calipers though.

Did you purchase the calipers (what’s the exact model so I can check what piston size diameter they are) directly from wilwood and the caliper adapters from Massive ?

And finally what wheel size diameter and offset / backspace you are using for clearance ?

Thanks

[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.

[FredK]

I have not measured the pressure.

I use the spreadsheet available at this link
http://www.gt40s.com/forum/gt40-tech...ood-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.

[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]

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]

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]

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.