Brake questions

Re: Brake questions

John Reed — Thu, 14 Jun 2012 19:28:43 -0500

Good advice from all, I appreciate it! I wasn't really trying to mix and match old parts, more trying to find the best solution that fits under the 14" wheels that are already existing (so I don't have to waste time doing something custom) and the RX7 calipers are the most popular with brackets readily available. I just find them a little too tight for comfort. I like the idea of the wheels being a "fuse" and being able to take some damage without causing me other issues. Plus I really need to move the master cylinders, for a variety of reasons.

I guess we will see how it all works out when the parts show up. Tilton was very helpful in spec'ing out the pedal set/master cylinders so hopefully I didn't sign myself up for too much fiasco. No matter what, the brakes can't get much worse than they were at OTR. HAHA Next step was to cut the floor out so we could drag our feet.... :-)

Re: Brake questions

Cosworth — Wed, 13 Jun 2012 04:04:19 -0500

You're right Grant, but Aaron is also not out of line, because I would normally recommend the proper stuff. BUT since the guy is looking at doing a mix match of parts and adaptations, too many things can already cause problems, so then why add another denominator in this equasion of fuck up?

Tandem master cylinders need to be properly setup, the fill ratios between the front and rear hydraulic factor need setup so that the initial timing comes on at the same time, or at least a safer the front before the rear. All of this is not counting the proper positioning of the balance bar because that also can cause issues. More than 3 turns from 50/50 (middle point) causes severe bias migration due to the bar pivoting on the master with most resistence.

So with all the mix match and adapting old equipment and machining, etc... all you need is the caliper mounting face not to be perfecly square with the centerline with the disc for you to have a long unpredictable pedal with a constant mild brake drag.

So with all of that being said, why not just run some good pads, good fluid and a prop valve. Less stuff to go wrong and the performance is not too far off from what you would gain with all the other equipment.

Re: Brake questions

NoCoast — Tue, 12 Jun 2012 14:27:01 -0500

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Aaron Luptak

who are you, and what did you do with Cosworth?

I'm aware of that part. It's the "don't do dual m/c's, its not needed" that seemed different than his previous posts.

Ha. I read that literally, like what work, not what set of stairs did you stuff him under.

I'm guessing Paul's point is, if you are looking to hodge podge a braking system together using junkyard parts or 25 year old calipers, you are probably more likely to end up with a fucked up system that doesn't operate correctly and are better off just keeping the system stock, tossing good fluid and pads at it, and going out and having fun.
We won the regional overall at Rally Colorado against three different $40-50k Open class Subarus in a GC with a nearly stock junkyard sourced 2.2T engine, $1000 used DMS struts and stock discs front, stock drums rear with Porterfield R4 pads. We even drove the car to and from the event...

Re: Brake questions

Aaron Luptak — Tue, 12 Jun 2012 14:19:21 -0500

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NoCoast

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Aaron Luptak

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Cosworth
Also dont put in a dual m/c setup. No need and its more stuff to deal with and problems can easily develop if not tuned right. Just remove the booster and redrill the clevis hole closer to the pivot on the brake pedal to gain some ratio. Put a prop valve to the rears and call it a day.

who are you, and what did you do with Cosworth?

Paul is an engineer and works for Performance Friction.

I'm aware of that part. It's the "don't do dual m/c's, its not needed" that seemed different than his previous posts.

Re: Brake questions

NoCoast — Tue, 12 Jun 2012 13:14:36 -0500

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Aaron Luptak

Quote
Cosworth
Also dont put in a dual m/c setup. No need and its more stuff to deal with and problems can easily develop if not tuned right. Just remove the booster and redrill the clevis hole closer to the pivot on the brake pedal to gain some ratio. Put a prop valve to the rears and call it a day.

who are you, and what did you do with Cosworth?

Paul is an engineer and works for Performance Friction.

Re: Brake questions

phlat65 — Tue, 12 Jun 2012 00:42:09 -0500

Adam, I have brake feel issues on my Volvo at the track, I am pretty sure it is the rear axles moving and pushing on the pistons. It did not change with new front wheel bearings.

Re: Brake questions

John Reed — Tue, 12 Jun 2012 00:34:21 -0500

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acrane
I am basically running volvo all around now.
steel 4 piston front,
steel 2 piston rear,
volvo wheels, 14 (stock alloy) or 15 (never run stock volvo 15s).
I only had perfect brakes once. and it only lasted a day.
with the stock stuff, I had done a bolt check, replaced the front wheel bearings, and the MC (still boosted).
I think the pads getting knocked around was the biggest reason for the poor feel. everything else had been replaced.

Here is something Australian . . .
http://www.hachiroku.com.au/2009/06/ae86-tuning-guide-ultimate-stopping-power/

The RX7 setup in that link is what I was looking at (but was worried about fitment), but I talked to T3 today (also in that link) and they have their Wilwood 4 piston setup in a size to suit 13"/14" wheels (using a 10" rotor) so I decided to take the plunge and order that setup. Will make it nice to have such a wide range of pads/compounds available too. Not sure what is available for the rear (I think I have the same Volvo two piston as you).

Re: Brake questions

Aaron Luptak — Mon, 11 Jun 2012 23:03:01 -0500

Quote
Cosworth
Also dont put in a dual m/c setup. No need and its more stuff to deal with and problems can easily develop if not tuned right. Just remove the booster and redrill the clevis hole closer to the pivot on the brake pedal to gain some ratio. Put a prop valve to the rears and call it a day.

who are you, and what did you do with Cosworth?

Re: Brake questions

acrane — Mon, 11 Jun 2012 19:57:25 -0500

I am basically running volvo all around now.
steel 4 piston front,
steel 2 piston rear,
volvo wheels, 14 (stock alloy) or 15 (never run stock volvo 15s).
I only had perfect brakes once. and it only lasted a day.
with the stock stuff, I had done a bolt check, replaced the front wheel bearings, and the MC (still boosted).
I think the pads getting knocked around was the biggest reason for the poor feel. everything else had been replaced.

Here is something Australian . . .
http://www.hachiroku.com.au/2009/06/ae86-tuning-guide-ultimate-stopping-power/

Re: Brake questions

SgtRauksauff — Mon, 11 Jun 2012 14:18:39 -0500

What pads are you running currently?

I've only used my '85 Corolla for cone squishing and for Lapping days, so it's not a direct comparison to yours, but here's my take on the brakes I've got on the car:

I'm not caged, but do run a full interior. No undercoating/etc has been stripped from the car. The car was weighed at 2463lbs, with me and fuel and spare tire, before I put the power steering system on. A cage, codriver, and rally spares and tools would probably add a few more pounds, but I'm not sure how much.

That being said, I'm able to out-brake EVO's and STi's and Z06's and Mustangs at HPDE's, particularly at Brainerd MN, coming in to turn 2 at about 120mph in 5th gear, and most other corners as well. (Part of this may be driver input, rather than the mechanical component.

After a 25-minute session last year, I measured the temperature on the front rotors after a cooldown lap and sitting for 3-5 minutes at ~320Â°F.

I've got stock calipers and rotors. I did actually route some cooling duct from the front bumper to point at the caliper. This may be more difficult to do on a rally car, depending on how your skidplate is set up.

This time I happened to be using some ATE blue fluid (I swap it with clear fluid alternating times, to make sure I get a complete flush.)

The biggest component, in my opinion, is the pads, however. I'm currently running Raybestos ST-45/43 pads front/rear. You get them from Porterfield, so they might just be a rebranded Porterfield pad, like the R4 or R4E, but I'm not sure. I just talked with them about what I was doing with the car, and that I'd used Carbotech XP-10/8's previously. After installing them, and using them, I can honestly say that I've never used a pad that has such a great balance of initial bite and extremely high temperature tolerance. I do a lot of track days at Blackhawk Farms, at which it is not uncommon to go through an entire set of pads through one event, with a re-bleed after every session. I did not have to re-bleed even once with these pads. I don't know the temp of the rotors when actually braking when they're hot, but I managed to get some pad fade on the carbotech XP10s, which have a claimed fade resistance up to 1650Â°F.

So, long story short, I think the stock calipers on this car are mechanically sound enough to work really well. The tiny size fits under whatever wheel you want.

BUT it doesn't have a lot of mass to be able to absorb/dissipate the heat generated.

My way to be able to work with those temperatures was to add ducting, and go with a pad that can tolerate higher heat.

Putting in bigger rotors with bigger (aluminum) calipers will also help combat the heat, as well as having a larger pad friction area on the larger rotor. Depending on the cost of fabrication/adaptation, that could be the best bang/buck around. For myself, because I like to use 13" wheels for cone-squishing, I needed to stay small, so I went with the ducting and really friggin' good pads.

Just some food for thought, since I don't actually rally (yet) so my voice of experience may not be as well educated as some others.

--Jorden

Re: Brake questions

John Reed — Mon, 11 Jun 2012 11:34:19 -0500

Thanks for all the input guys, appreciate it a ton!

I have a few reasons for wanting to go with a pedal assembly. One to improve feel, two to give myself a lot of range to adjust stuff (I like to mess with things almost as much as I do racing) and lastly/most importantly to free up space on the firewall to brace the strut towers a bit more. There is quite a bit of room under the dash to put stuff, but space in that corner of engine bay is at a premium. Ketchum stage at OTR illustrated that a few things need to get moved around. HAHA

If I can't find a fitment of front caliper I am happy with, I will probably just keep the stock calipers for now and run them with a pedal set. I think they would be "enough" but if I can get more under there, I am always happy to have more if I need it, especially if I get a wild hair and do some track day events with it.

The rear setup on the car seems really good already, Volvo stuff.

Re: Brake questions

Cosworth — Mon, 11 Jun 2012 04:28:44 -0500

Run good fluid, and flush it all the way to the bleeder at the start of every rally. Run a good pad. Its all you really need for that car to be good on brakes.

If you start micky mousing the brakes, you are asking for to many problems.

For good pads for that car, get Cobalt Friction preferably and if they dont make your shape go with Carbotech.

Also dont put in a dual m/c setup. No need and its more stuff to deal with and problems can easily develop if not tuned right. Just remove the booster and redrill the clevis hole closer to the pivot on the brake pedal to gain some ratio. Put a prop valve to the rears and call it a day.

Re: Brake questions

mellow65 — Mon, 11 Jun 2012 01:00:26 -0500

Well he had the Volvo rear axle so I'm sure he went back to the stock Volvo stuff.

Re: Brake questions

Dazed_Driver — Mon, 11 Jun 2012 00:51:38 -0500

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mellow65
Any one have info on what Adam did on his? Didn't he end up doing Volvo stuff up front?

I'm not sure. I seem to recall his did something like an entire volvo upright swap? Maybe?

I'm not sure about the rears either... if I'm remembering right he used the volvo wheels, so he could keep the volvo calipers, as they're 2 pots and too wide to fit into a corolla wheel. Or something. They didn't fit...

Re: Brake questions

mellow65 — Sun, 10 Jun 2012 23:55:08 -0500

Any one have info on what Adam did on his? Didn't he end up doing Volvo stuff up front?

Re: Brake questions

sidewaez — Sun, 10 Jun 2012 23:41:07 -0500

Yeah the brakes were always a conundrum on the corolla, it's too bad there's not a ton of room for 15's. Would try the rx7 stuff, because if it doesn't work there's a good market to sell it off and you can return the calipers to the parts store.

You're already running wheel spacers right? I think for pedal feel dual master cylinders would help the most, at least that's the next upgrade we planned to make to the car.

I also have rebuildable calipers and rebuild kits that come with the car.

Re: Brake questions

Dazed_Driver — Sun, 10 Jun 2012 02:01:28 -0500

Yeah, I plan to run pizza cutters. I would try the wheel spacer, then. You keep the wheels/tires, but gain some clearance on the thin side.

Re: Brake questions

John Reed — Sun, 10 Jun 2012 01:51:24 -0500

Those AP brakes are so sweet! I wish my budget had room for those....

The RX7 brake setup everyone seems to run (at least that there are off the shelf brackets available for) use a Honda Civic rotor that is bigger than stock AE86 but obviously smaller than the RX7 rotor. With this setup they will fit certain 14" wheels (I have stock GTS wheels), but not all and if they do the space is very tight.

Re: Brake questions

mellow65 — Sun, 10 Jun 2012 00:26:29 -0500

They slip over the studs.

Re: Brake questions

Dazed_Driver — Sun, 10 Jun 2012 00:11:39 -0500

Ooooh, ok. What sort of rotor is an RX7 front? bolt on the hub style?Or does it slip over the studs?

Re: Brake questions

mellow65 — Sat, 09 Jun 2012 23:14:10 -0500

It would depend on the rotor at that point. If he's doing rx7 rotors then yes he will need 15s. But if he's making the 4 pots fit on his stock rotors then he probably would be ok.

Re: Brake questions

Dazed_Driver — Sat, 09 Jun 2012 22:38:31 -0500

Hmm... read that wrong. I read ".1"...

About how much is a gnat's hair? Literally almost nothing? You might consider just a 1/8-1/4" wheel spacer maybe, to move it way.

I thought you "needed" 15" wheels for the rx7 calipers? What wheels are you running?

Re: Brake questions

mellow65 — Sat, 09 Jun 2012 21:42:38 -0500

An inch is probably more then most people have. The 2 pot Subaru non wrx calipers really take up most all the room under a 15" rim. then there are 15" rims out there that fit over wrx calipers, and with street rims you need 16s to clear them.

I say press on, and just stick with tough 14" rims if you are really concerned about it. Personally I wouldn't give it two thoughts.

Re: Brake questions

Dazed_Driver — Sat, 09 Jun 2012 20:34:52 -0500

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John Reed

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Dazed_Driver
What kind of budget do you have? There are a few different brake kits out there for AE86s.

I didn't have a set dollar figure in mind. The main goal was to just improve them, without wasting money. I have found a lot of options but the 14" wheels are the roadblock I keep running into. The RX7 setup seems to be the best bang for buck, they do fit the 14" wheels, but there is not much space left inside the wheel in the event something gets bent up. I have seen other rally cars where they run them pretty tight, so maybe it is fine like that. I guess the main goal is always, just don't bend stuff up. HAHA

I looked at a Wilwood caliper which would probably fit nice with a custom bracket but wasn't sure how important it would be that it doesn't have dust seals like an OEM.

I have seen your build on EvoM, car is very cool!

Thanks!

grp4fabrications does have two AP brake kits. One is said to fit under 13" wheels. They probably mean motorsport wheels like a mini light or something, however, they would probably fit under stock 14s.

I made a custom Wilwood set up for my fronts, however, if it proves to not work out, I'll be going to that AP kit.

http://www.grp4fabrications.com/product_info.php?cPath=42&products_id=428 <- that is the kit.

Obviously, it's AP, so its a bit spendy. But, it's AP... so its quite nice. The conversion rate isn't TOO killer right now, but I have no idea what shipping would be like. Nor do I know if you can piece together everything in that kit save for the brackets and buy just them. Also, if you can, you could always MAKE your won brackets and run a wilwood/ap/whatever caliper.

Re: Brake questions

alosix — Sat, 09 Jun 2012 16:54:59 -0500

Not 100% sure what's considered acceptable clearance, but my 40mm offset (vs 53 stock) Team Dynamics 15s vs a stock WRX front caliper just barely clears and I doubt I'm the only one with this combination.

I'd wonder if you can bend a rim in an area that would affect caliper clearance without royally fubaring the car/wheel/corner in the process.

Re: Brake questions

John Reed — Sat, 09 Jun 2012 16:51:45 -0500

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Dazed_Driver
What kind of budget do you have? There are a few different brake kits out there for AE86s.

I didn't have a set dollar figure in mind. The main goal was to just improve them, without wasting money. I have found a lot of options but the 14" wheels are the roadblock I keep running into. The RX7 setup seems to be the best bang for buck, they do fit the 14" wheels, but there is not much space left inside the wheel in the event something gets bent up. I have seen other rally cars where they run them pretty tight, so maybe it is fine like that. I guess the main goal is always, just don't bend stuff up. HAHA

I looked at a Wilwood caliper which would probably fit nice with a custom bracket but wasn't sure how important it would be that it doesn't have dust seals like an OEM.

I have seen your build on EvoM, car is very cool!

Re: Brake questions

Dazed_Driver — Sat, 09 Jun 2012 16:43:36 -0500

What kind of budget do you have? There are a few different brake kits out there for AE86s.

Also, how often were you bleeding your brakes? Did you try that to regain some pedal feel? Had you bleed them before the rally?

Brake questions

John Reed — Sat, 09 Jun 2012 16:30:49 -0500

So after Oregon Trail, I decided the first thing that I wanted to change on the Corolla was brakes. Mostly it was a pedal feel (start pumping it early to see what would be there when you needed it) but figured while I was at it I would look at just getting more brakes on the car.

RX7 4 piston front calipers are the cheapest/most common upgrade and I have a set of those but the question I have is: How much clearance do most consider acceptable on a rally car between the caliper and the wheel (I am thinking both for rocks getting up in there, and wheels getting bent)? The RX7 calipers are a tight fit inside my 14" wheels, leaving about 1" between the inner bead and the caliper (most likely spot to bend) and a gnat hair in the inner part of the wheel.

Other options are keep the stock calipers and rebuild them and run good pads, or look into going to 15" wheels (not sure the car has suitable room for that, and I lose a lot of spare wheels it came with).

Thanks in advance!