Brake fitting in 15" wheels

[Skip Fix]

OK guys I have a question for you on fitting big brakes. So many of the aftermarket kits require 16" or bigger wheels for 12" rotors. GM put 12 " rotors on B body cars with 15" wheels. NASCAR requires 15" wheels and uses HUGE 6 piston calipers. Corvettes and early Camaros/Chevelle/GTOs used big 4 piston calipers in 14 and 15" wheels.Why the fit issues from the aftermarket?

Saw a article in newest HotRod of a girl who made custom brackets to fit the larger Wilwood calipers and 11.75 rotors in 15" Chevy Ralley wheels.

Why not kits using a bigger caliper/pad from Wilwood than the dinky Dynalyte? Baer's calipers are similar to factory GM 3rd/4th gen that aren't that tight in factory wheels.

[critter]

Skip, I often wonderd the same thing. Not everyone wants the cookie cutter Pro-Touring look (no offense, guys). Some of us like the resto-mod look that you and I have pursued with our cars.

You know I modified my stock spindles and used the Howe aluminum dual piston calipers. That was a big improvement. I think the 1LE upgrade with B-body spindles would have been better. Too gad someone doesn't make a reasonably priced kit for us.

[Skip Fix]

I also always wondered if the two piston PBR types if they have same piston sq in(force=PSI x sq in) of the factory single pistons are a real improvement or marketing.

Surely these other calipers don't stick outer diameter more than the factory calipers on the 15"s.

Guldstrand years ago welded a bracket on F/B spindles to take a Vette 4 piston caliper.

I've got some 1LE rotors and B body 12" spindles sitting around just pondering caliper choices.

[BonzoHansen]

This has been talked about much here and at nastyz28.com The stock calipers do have pretty big pistons. There are some upgrades out there, but some wheel clearance issues might exist.

The b-body swap is easy & cheap.

[Skip Fix]

So lets use a cheap B body spindle and 12" rotor and figure a easy caliper upgrade swap. Seems alot of options for the first gen guys, fewer for the second gen. I'll bet there are more second gen cars out there for potential customers!

[critter]

Skip, take a look at this and see if it gives you any ideas. I don't know how much space there is with B-Body and a 12 rotor but it might work.

http://www.arkansaspontiacs.org/techstories/BudgetBrakestory.htm

[jake72ss]

Critter,

how do the Howe calipers compare with stock? I've considered using them or the single piston versions from wilwood or outlaw also. After doing the conversion did you notice any difference in pedal feel or travel? I have the Bbody spindle/ 1le setup on my chevelle with seville calipers in the rear, stock booster and master. My chevelle brakes awesome compared to stock disc/drum. I , like you two guys like the restomod look and prefer not to use stuff that limits wheel sizes below 15-16" range.

[critter]

There was more pedal travel because of the additional piston area. I did notice shorter stopping distances. That was tested with a before and after on a Gtech type device called a Varicom. I had 60 to 0 in the 120-130 foot range. That was with drum brakes on the back. I haven't tested again since adding the rear, 79 Trans Am, disc setup.

That said, I would not do this again. I'd rather go with the larger rotor and single piston caliper on the front. I think it would give the same results based on what I've read from other folks.

My real question is, what would this type of caliper do on a 1LE setup and will it still fit in the 15 inch wheel?

[Skip Fix]

I still have a Vericom also! I've had it 15 or so years.Did have it updated to do 1/8 mile stats inthe read out also.

[jake72ss]

critter, to answer your question I believe they would still fit the 15 inch wheel, I have had 15s and 16 inch wheels on my car with this set up using the stock caliper of course. The wilwood gm3 and the outlaw d52 style calipers both look to be a strait forward swap.

[critter]

I do know someone who's use the stock setup with the Wilwood calipers. Worked great for them. I might give the 12 inch setup a run since I already have the calipers. Another project for another day.

Skip, that Vericom belongs to my brother-in-law. We still use it and it's still amazing how accurate it is. I've never used a Gtech but I bet it's comparable.

[SHANE 73Z]

Hey guys,

I just thought I would chime in. On the front of my 73 I am running b-body/1LE with SSBC calipers. These are the 2 piston D52 replacements with the 38mm bores (same as C4 PBR). These were chosen to match with a 12" C4 rear conversion from touring classics.

I can tell you that the b-body/1le arrangement with STOCK calipers will fit inside stock 15" Z28 wheels. With the SSBC calipers there were issues. I am sorry to say that I didnt do any measuring to see wat it would take to make it work. I cannot say if the rear setup fits inside or not.

On another note the second gen cars that have both holes drilled in the pedal, the manual hole only provides about a 5:1 pedal ratio. This makes it extremely difficult to find a MC with a bore small enough to run these small bore calipers.

There is a gentleman on the NastyZ28 website that offers brackets that use a 13" wilwood rotor & superlite caliper that fits a 16" wheel. I believe he is also developing a bracket that would mount the same caliper with a 12" rotor that could potentially fit a 15" wheel.

I am hoping to upgrade to a Wilwood f/r package in the future.

Shane

[jake72ss]

Do you have a link to a post so that we can see what the guy on nasty z28 is offering? That setup sounds interesting.

[SHANE 73Z]

Here is a good thread:

http://www.nastyz28.com/forum/showthread.php?t=58479&highlight=wilwood

Shane

[critter]

Does anyone sell a B-body kit with everything except the calipers? I'm lazy enough to buy it rather than search the yards for the spindles.

[Skip Fix]

At one time Global had one also.
That's the kind of system I'm talking about!

[OLDFLM]

Scarebird has them...

[critter]

Has what? Spindles?

[TheMonkey]

scarebird makes custom brackets to convert to disc brakes. for one of my '61 pontiac full size B body cars, i bought scarebird brackets and it worked great.

buy the brackets (about $90; very well made), and he sends you the brackets & a shopping list). i kept my original spindles. for my application, from rockauto i bought 12" rotors for a '77 bonneville, calipers for a late model 1500 GM truck, new hoses for i forget what. i converted to 12" disc brakes up front for a few hundred bucks. another bonus was that my car came original with very expensive and crappy ball bearings; with the new rotors, it took the much better & less expensive roller bearings. any replacements in the future come from the corner auto parts store.

Mark from scarebird is very helpful and a fellow enthusiast.

i had the brackets powder coated with the rest of my front end and it looked super clean.

www.scarebird.com

[83hurstguy]

I would prefer not to put the B-body spindles on my car, as I would rather change the geometry with the stage 2 package from SC&C to avoid the bumpsteer...

I would also like to be able to run the stock 15" SSIII's that came on my car for some car shows...

Apparently, from reading on thirdgen, the Vette C4 brakes (non-HD) are 12" in diameter and fit a stock 15" wheel. The difference between these and the 1LE brakes are rotor thickness (1" vs. 0.82", 1LE is thicker), and the Vette brakes use a slip-on rotor. LIke I mentioned, I would prefer not to run the B-body spindles... seems like basically all I would have to do is make custom caliper brackets and get a hub to throw the rotor on.

Any input on the C4 brake setup?

[trackrat79]

You guys mite want to look at circle track supliers. Many of the local region racing series run chassis based on production parts if not just modified factory chassis. They have spindles, hubs, arms calipers that are all design around 15" dia wheels because thats what they have to run. It is how I found aluminium hubs, slip on rotors and solid mounted calipers for my truck. It took some digging though some different catalogs and talking to several people but eventually found something that will work. Now it is just a matter of saving up the money. It also helps that I had several suppliers in the area that I could go to in person and take parts with me that I had to use and see what would and would not work before buying anything. A place that has a lot of stuff ishttp://lefthanderchassi.com

[Karch]

Critter, others, do you actually like the Howe 2-piston calipers, or would the GM single piston be better?

I have a Tall B-body and 1LE setup that I am planning on installing later this month, and I just picked up a LS1 rear setup.

I like the idea of the twin piston caliper, and the lighter weight, but when I called Howe to inquire about street use the guy was very elusive....just didn't want to talk about it. I would have signed a waiver if that's what he wanted???

Thanks

[chicane67]

Guldstrand years ago welded a bracket on F/B spindles to take a Vette 4 piston caliper.

I have a set of these if anyones interested........

[Karch]

Anyone want to chime in on my above question about the Howe calipers?

Also, what size piston should I go with if I do go this route?

Thanks.

[PonchoJohn]

Skip,
You might try reading about Cheap Big Brakes on chevelles.com
I seem to remember there was a guy (I think he called himself Bill C.??) who used Suburban parts to make a H/D braking system that would fit in a 15" wheel. From what I remember, the rotors were 1.25" thick, so they can take some abuse.
John

[BonzoHansen]

Anyone want to chime in on my above question about the Howe calipers?

Also, what size piston should I go with if I do go this route?

Thanks.
I'd be curious on input regarding the Wilwood GMIII calipers. I have been told they work for the 1LE 12" setup on b-body spindles that is common on 2nd gens. And they fit better - I think the Howes are bigger and can cause clearance issues on some 15s. IIRC.

Also, I know guys on NastyZ use D61 pads, which have a larger pad area. Sometimes they fit under stock calipers, sometimes they do not. When they don't, they use a caliper for mid 70s Chevy van. Same mounting points, just wider (and larger banjo bolt on the line)

[Bandit]

Skip, I am currently installing Wilwood 12.19" Big Brake rotors and 4-piston calipers on my car. When I am finished I will test fit the stock 15" snowflakes to see if they fit with those brakes. (Now that you have my curiosity peaked) I will report my findings to you.

Paul

[Skip Fix]

Let me know!!

[Bandit]

Forgot to mention, my stock rims are the wider 8" snowflakes, I don't know if that would make a difference over the 7" ones as far as BS or whatever.

[Skip Fix]

All mine are 8" snowflakes.

Interesting note on stock caliper drag. My 81 TA has the "low drag" calipers and they do have less drag thran the stock 78 TAs calipers. But today I spun the 2004 GTOs and there is basically no drag at all on those calipers.

[andrewb70]

All mine are 8" snowflakes.

Interesting note on stock caliper drag. My 81 TA has the "low drag" calipers and they do have less drag thran the stock 78 TAs calipers. But today I spun the 2004 GTOs and there is basically no drag at all on those calipers.
I think many modern calipers (I believe the GTO calipers are made by PBR) will retract the pistons.

As a side note, please be careful when using circle track parts. Some of these parts are not designed for heavy street use and they are not designed to be used on heavy cars. Just a word of caution.

Andrew

[trackrat79]

I have never had a problem. I have seen parts last multiple seasons before needing replacment.

[critter]

Sorry, gone for a while and don't post here a lot.

Karch, yes, I like them but should have done more homework before doing it. The smaller piston size would work better than larger. Now I know.

If I do it again (and I will) it will be the 1LE with a test fitting of the Howes. If they don't work I'll go with the Wilwood GMIII.

Andrew, while I understand where you're coming from, what do you think is more stressful, track or street? How much do we really drive our toys? See my point?

[Skip Fix]

Andrew the Wilwood aluminum GM caliper is the "spec" caliper used on many Late Model Asphalt cars on all 4 corners, although with a 1.25" rotor. These cars aren't that light, pretty sure they are definitely over 3000lbs. and I would bet stress the brakes as much or more than aggressive street driving.

I beleive the 1LEs are closer ot a 1" diameter, not sure if they have Wilwood single piston or Howe dual GM types for that thickness, I thought just .81 or 1.25.

What was the issue with the Howe's and larger pistons, not enough master volume to use them as good?

[critter]

Yeah, Skip. When I pulled the rear drums and replaced them with 79TA rear discs the pedal has a TON of travel and not much feel. Brake feel was great and stopping was very good with the rear drums.

After doing my homework I found that I had too much piston volume for the MC. Swapping to the smaller piston Howe's is a cheap fix if it works. I might try that if I find an extra couple of hundred laying around.

[Karch]

Thanks Critter.

Correct me if I am wrong, but you are saying the large pistons don't give you decent pedal feel?

I spoke to Howe about their calipers, a second time, and they said to go with the largest of the three offerings, when combined with the LS1 rears.

I am right now in the midst of the change from 10-1/2" to 12" 1LE changeover, and I just found my m/c to be leaking. I am going to get a new 1-1/8" replacement tomorrow from CPP. I just bent a new 3/16" line, hooked up a line lock, and the Wilwood adj. prop valve. (I think fluid regulator is a better term?).

[critter]

Yes, that is correct. The larger pistons require a larger volume of fluid. I used a 79, WS6 master cylinder and I "think" that's a 1 1/8 inch master. When talking with the brake experts they all seemed to think that the combination of the big, single pistons on the rear (79 WS6 disc brakes) and the large pistons in the front were too much. Solution? Bigger MC (not possible) or smaller total piston area to be applied.

You do know that the Howe dual pistons are not a direct bolt on, right? I had to do some judicious grinding on back of the spindles for clearance.

[Karch]

I actually wasn't entirely aware they weren't a bolt on deal. I do remember seeing someone had to grind away some areas, but I either thought it didn't apply to the tall spindles, or I just simply allowed myself to blissfully forget there would be any issues...and we know how that always turns out.

I do think there are some m/c's out there that are 1-1/4", maybe even a 1-3/8", just in case you are interested, but I do see your point.

I'll give the iron ones a go for now, and see how well it works. I still need to add the rear discs. I have 2 setups. One off the Elderado's, similar to what you have, with the problematic calipers, and one set off an LS1 type camaro. I have to be sure they'll clear my 15" wheels. While I do want to get a set of 17's, I want to keep the 15's for drag racing.

Thanks again. CPP is having a sale that ends soon. They have new (not rebuilt) m/c's for $42. That's where I am off to.

[BonzoHansen]

I beleive the 1LEs are closer ot a 1" diameter, not sure if they have Wilwood single piston or Howe dual GM types for that thickness, I thought just .81 or 1.25.I'm told you use the #5861 GM III calipers with the 1LE swap. 1" disc width.

The GM III for 1.00" width rotor is machined and fitted with OEM type slide pin vibration dampeners for a direct OEM caliper interchange.
http://www.wilwood.com/Products/001-Calipers/024-GM3/index.asp

[Skip Fix]

I thought the factory single piston cast iron had a bigger piston than that Wilwood, hench more potential clapping torque. So othe than lighter I don't know what you are gaining. Often the cast iron is more rigid also nad less flex in the caliper. Maybe the III is better than their older ones.


Critter if you used the stock single stage booster pedal instead of the 4WD pedal that could have been some of your issues. It has more leverage so easier push less MC travel than the 4WD pedal hole.

[critter]

Skip, already drilled the pedal and dropped the rod 1 inch. That helped but it still has a ton of travel before the brakes start to grab. The car stops well enough once you get there but the pedal doesn't inspire confidence.

I need to ask a question. Does anyone know if the distribution block for the 79TA maintains the 2psi residual pressure to the rear brakes? If not, should I install one in line to the rear to see if it helps?

[Skip Fix]

On my factory 4WD retrofit I just used a T in the front and an adjustable prop valve in the rear.

I thought ususally only drums use a residual P valve. Often the older cast iron masters its in it underneath the flair for the brake line. I haven't seen it in 81 aluminum masters, so they may have moved it in the distribution/prop valve.

[Karch]

Usually the 2lb check valve is for when the calipers are mounted higher than the m/c, such as when the m/c is below the floor of some chassis, I don't see how it would be a problem, especially just to try it.

It seems that would be one remedy, or look for a larger bore m/c?

[Gtrpunk23]

A 12 3/4" wilwood will fit in a 15" torq thrust if the backspacing is right.

[shortrack]

Andrew the Wilwood aluminum GM caliper is the "spec" caliper used on many Late Model Asphalt cars on all 4 corners, although with a 1.25" rotor. These cars aren't that light, pretty sure they are definitely over 3000lbs. and I would bet stress the brakes as much or more than aggressive street driving.

a local track around here is a 1/2 mile paperclip identical to Martinsville Va......Yep I think having your rotors glowing red hot twice a lap for 50 laps qualifys as stress.......