Rotors, calipers and wheels

I am having a difficult time with the selection of these for my DRB. It came with the standard 11.5 corvette rotors. the wheels that came with it would not work with any brand of calipers as the wheels were what I call two stage wheels. That is the inside diameter of the wheel has a step down mid way across the wheel decreasing the inside diameter. So those were sold. Now looking at other wheels that I am interested in, particularly TeamIII, their wheels have the same step with the warning that if the offset is too far, the calipeers will not clear(14" down to 13 3/16" I believe). I still haven't figured out how much is too much, even with conversations with TeamIII.They gave me the wheel measurements, but that didn't really help me.The original wheels I had had about 5" of offset(10" wheel measured from the inside of the wheel to the mating surace of the wheel), and the tires (295's) cleared the wheel wells by about 1/2 to 3/4 of an inch and were very close to the bolt securing the bottom of the upright. I really want to stay with the 15's if possible for the street as Goodyear and others still make plenty of brands with the 295 size. I am having difficuly figuring out:
1. How much offset to use on the rear tire.
2. Which caliper I could use with the original rotor that will clear the wheel.
3.How do the larger rotor and caliper line up with the original mounting bracket?
Does anyone have any numbers on how much backspacing you can go with on the 15" TeamIII wheels(10"). Am I just missing something here? Couldnot find anything researching this.
Bill

Bill,

I'll have to dig out some drawings that Bob William sent me with the backspacing that he used and that Dennis originally designed the DRB to use. My old feeble mememory says that 4.5 - 5.5" was the number. I think around 5 was the optimal. Gotta run at the moment, but I'll check later and take a closer look at your other questions.

Regards,
Lynn

Hi Bill,

I can't help you with the 15" wheel setup as I whimped out of that & went with 17" so that I could use the stock 87 Vette rotors/calipers & got a bigger range of tyres to choose from.

If you get desperate & end up deciding to go 17", I have all the wheel, offset, tyre info.

Kind Regards,

Peter D.

Bill, talk to BOB LACEY at VINTAGE WHEELS who I am sure will help you. VINTAGE WHEELS INC. DEL MAR CA. (619)952 4717

A followup. What type and size rotors/calipers are you guys with 15" wheels using???
Bill

Bill,

You know Denis is on this forum, right? (Saw a post from him in the Chassis Drawings/Blueprint thread in this same forum.) Have you asked him about any of this? I have 17" wheels also, so I can be of much help to you either.

Regards,
Lynn

If you go here http://www.baer.com/ and are interested in their calipers, I seem to remember being able to print out in full size a template of their caliper setup and then stick it in the wheel to check the fit.

Bill,
I went with Baer 4 piston Alcons and 13" rotors, but in a 16" wheel. No way that setup would fit a 15" with a rotor that big. Even with a 16" wheel, there wasn't room to run a two piece rotor that big, so it's a single piece rotor.

I had downloaded the templates Baer provides and they showed the calipers to be VERY close to the wheels using stock brackets. PBR's were also close.

Your best bet is to do what I did. Talk to Ben O'Conner at Baer. I ended up sending an upright/spindle/wheel assembly to them so they could see what they could fit. Took them a while to work my project in, but it ended up they were able to use in stock brackets from another application to fit the calipers.
They would have been probably too close to call by using the templates only, plus the templates are made to check clearance of the caliper to wheel using "stock" caliper mounting brackets. Using different brackets as was done in my case worked out well.

Dave

Thanks for all the advice. Dave, your idea is probably what I will have to do as 15" rims looks to be a dead issue. I am trying to talk to the Corvette people at Mid america Designs, one of the largest in the country. They have some very knoledgable people and have given me straight advise in the past(suspension bushings that would and wouldn't work).Baring no help from them(floating single piston calipers) I will go the Baer route.
Bill

Bill, If you decide to use a 17" wheel and your car will now fit corvette rotors and calipers there are a LOT of options for wilwood brakes including rear 2 piece rotors that use a drum brake hat assembly for the parking brake.

I am at present doing the mock up on my GTD so that I can use superlight II calipers and 12 or 13 X 11/4 Vented curved vane rotors. Looks like 13" rotors are a no problem fit up front.

The only real problem is the cost of adding a parking brake instead of going with a simple two piece rotor at the rear.

I'm really thinking of using a line lock in the rear brake line for a e-brake instead of a mech.operated e-brake.

Wilwood's are a LOT less money than Alcons or Bremos and the difference would pay for the wheels I bet. If you are on a buget they are worth a look.

Howard,
Everything you look at today is 13" rotors. There isn't anyting smaller. Most will say that maybe, just maybe it will work with a 16" rim. Better hope the rim isn't a two step, or you will have to be carefuol with your backspacing. Then you have to find a tire to fit. Looking at Tirerack.com, the largest you will find for any brand is 255. You have to go to 17s. Then you can go to 335 if you like (brand varies and so does price, $125 to $335)with a sidewall ratio of 35-40%. I'm talking Goodyear, Kumo, Pirelli, Avon, etc.. With the 17s you can choose any brand of rotor/caliper you want or your budget will allow. With the power that I am looking at, I don't think I have much choice(wheel size). For me it's more important to be able to stop than go fast. i know that the small calipers will work OK on the street, but what about on the track?? It looks like to me that the guys that want 15" rims will have to put up with inferior braking(read track) or go to something like a brake circuit recirculator. Maybe Alcon or Outlaw make something for the 15" guys, but I'll bet it isn't cheap. As of this wriying I can't find anything. Maybe some of you guys could shed some light???
Bill

If you are going with a 15" setup there are several choices that are used in the stock car scene. They are limited to 15" wheels and have heavy cars. They make up to 12.7" x 1 3/8" (I believe) rotors, etc. I would guess you could make some of that work.

Bill,

Check out Coleman Racing.

Here is an example of what you might find:
Brake Calipers - Series I, 4-Piston Caliper

• Heavy-duty cast aluminum body
• Finned body for better cooling
• Fits discs .810 or 1-1/4" thick, 11-3/4" to 12-3/16" dia.
• Uses HB-101 or 7751 series pads
• Available in two piston sizes and staggered bore
• Fits standard 3-1/2" mounts
• Weighs only 4-lbs.




Regards,
Lynn

The short track guys use 12.18 X 1.25 wilwood GN48 curved vane rotors and superlight calipers. A short race for these guys is 25 miles on a 1/2 mile oval track(pavement)and do 100 stops from about 125 down to about 60 in a row.The cars weight about 500 pounds more than our 40,s.

It's not the diameter of the rotor that makes for a good brake system its the amount of heat that can be rejected over a given period of time.

12 inch rotors are plenty big "IF" they can reject the heat. Quality curved vane race equipment like Wilwood, Alcon, etc should not have a problem with our normal weekend track day type usage.

A couple of other things to consider when it comes to GT40 replica brakes are:

The clearance between the outside of the caliper and the wheel center, outboard clearance as opposed to radial clearance. With 4 piston calipers this comes very close especially with the Team III wheel.

Another is functional brake cooling ducts. Quite a few of the kits don't have them or it's just an option. Can you gain just as much by spending money/time on a cooling system and save on rotational/unsprung weight?

One other thing is diameter. The original cars won lemans with speeds over 200mph with 11" rotors front and rear. 13" may be overkill especially on the rear, unless it's full out racing. An 11" rotor will lock up the wheels, larger sizes only increase endurance for more continuous braking through greater heat dissapation. How much endurance do you need?

A typical Indy car will run from 12"x 1-1/4" to 14"x 1-1/2" depending on the track, and Winston cup is around 12-1/2 because of 15" wheels and that's a 3,000 lbs car.

Howard,
What you are saying is what I'm after. The problem lies in the fitment(see Kalun's post above). You don't want to use a race wheel on the street(or do we?). The wheel manufacturers are the problem. They know that we(read race car replicas) want good stopping power and halfway decent looking wheels.Its just darn hard to put the two together. If it means I have to have less offset, then that is what I will have to consider. Its either that or go to the larger wheel.
Kalun,
The inside of those wheels must be different than those you and I can get, or the calipers are not available to the public, or their cost is beyond us. I wouldn't mind using the Weld wheels that many of the dirt and short asphalt guys use, but their catalog states "not for use on the street" or "not DOT aproved". I find it interesting you have a wheel that is subject to forces that no DOT wheel would survive, yet its not allowed on the street. I don't think anyone out there(law enforcement) would know if it was legal or not. Maybe the cost for aproval is too high???
Bill

Bill I think that if a guy really whats to do a 15 inch car because of orginality then thats fine. There are ways to put 12 inch corvette brakes in there and with the upgrades availble for corvette stuff there MUST be a way to construct a track day car with good to very good brakes.
You still have a tire problem but again there are some options here even with 15 inch tires.

16 inch wheels are sort of the same thing as 15's although I would be worried about a solution on period correct tires fixing the 15 inch issue but not the 16 inchers.

So you have my train of thought and how I got to 17 inch tires. Mainly I was looking for the easiest way to put 12-13 inch brakes on my car at a reasonble cost and have safe track use as an option. My wheels, PS engineering BRMS at 17X8 and 17X10, will fit plenty of brake with room to spare including brakes that can be run at least many factors harder than I will ever drive the car. I plan to do some track days as the car becomes more developed. Something like 10-15 claps at a time a couple times in a day . Sort of a cobra club type thing. I do drive the car VERY hard on the street but it is not possible to overheat good brakes AND drive safely on the street.

As I have raced bikes seriously before I know what a proper race program costs, both in time and money. Both of which I no longer have. Got old and have a family and I am too slow to attract sponsors if you want to know the truth.

I am as we speak I'm mocking up wilwoods on my car and when I get the brakes on the car I will post pictures. It is my intention to use all wilwood parts including the hats. The only thing that will be hand made will be caliper mounting brackets. I intend to post wilwood part numbers, instructions to modify the wilwood hats, drawings of the caliper brackets and my wheel dimentions when I'm done.
I believe others have done pretty much the same thing on their cars but I would like post a sort of how to do yours here on our forum.
So watch this space.

Acording to Bob Lacey and Coleman Racing, 12 inch rotors with calipers will fit the 15" rims. It just matters how much back spacing you do. I am not trying to be period correct in as much as I think the 15s look more "correct" to me. The 17s just look a little to tall, even though the diameters are basicly the same. It's that old aspect ratio thing. Skinny sidewalls look OK on the imports but somehow just don't look right to me for a 40. There are tons of street tires out there for 15s. My Goodyear dealer assures me he has several brands that go to 295. I might even be able to find 335. I'll worry about track tires when that time comes. Need the money for more street things first. So I am going to explore the 15s a little more and see what I can come up with. Will post my findings.
Bill

There is a lot more to consider when mocking up brake positions into the wheels than just size. If your car has a steering rack in front of the axle line ( like the GTD ) then the position of the steering knuckle is very important to get the steering geometry anywhere near right, particularly the Ackermann. On a GTD it is necessary to move the position of the knuckle outwards towards the wheels by some 40mm to get even parallel steering, this in turn means the brake rotor moves outwards and this in turn leaves very little room inside the wheel for the caliper. The whole set up must be looked at as a complete unit, and thats when it gets a bit more complicated. I run PS ENGINGINEERING wheels with AP 300mm rotors and CP5000 calipers, and there aint much room left inside the wheels, it gets down to feeler guage clearances. Frank

Most UK guys run 12 inch rotors (295mm to 305mm depending on calipers) in the 15 inch wheels. However these all tend to be rotors mounted onto brake bells. Why not buy these rotors, have bells turned to suit your desired calipers say from your corvette source, or wherever you fancy sourcing them and then match the two up. If you measure the thickness of the one peice rotors you would need to fit your ideal caliper, search the web for rotors that match. Brake systems are modular and you can mix and match to a degree to suit your application. AP and Alcon do identical rotors and when I need to change mine I go by availability and price as spec is the same.