So in getting ready toi run the C-3 at bonneville this fall we had to go to 300 mPH tires (from Nate Jones) and racing wheels. Right now we need an extra 1/4 - 3/8 inch backspace clearance - the wheels are hitting the calipers.

There are 2 acceptable cures for this - and 1 unacceptable

Unacceptable - wheel spacers - why? because SCTA rules do not allow spacers!

acceptable - find a 1 piece adaptor that will bolt to the suspension and have the lugs coming out of it.

the other option is to just plug the front brake lines and pull off the fromt calipers for the run - of course this only gives you rear wheel braking - but not to bad of an option for very high speed braking (we will have aq chute as well) You don't have to stop fast - just stop!

anyone familiar with where we could find an adaptor setup?

Carl Johansson

 

All of the adapters I have seen are 1" or thicker. This is primarily because you have 10 lugnuts per wheel. 5 for the adapter to the hub and 5 for the wheel to the adapter. The 5 for the adapter have to sit recessed in the adapter to clear the wheel.

I would be leary of removing the front brakes. I guess the chute will keep you straight, but if that fails for whatever reason and you get on the brakes, you run the risk of spinning the car.

A third more expensive option is different wheels that will clear the calipers.

 

VBP has adapter kits. The aluminum plate bolts to the lug studs and the aluminum plate has 5 lug studs mounted to it. The pic is not the best but you can get the jist of it and it may be what your looking for.
http://www.vbandp.com/detail.aspx?ID=184

 

with above. Adapters have to be 1" thick so that the lug nuts don't stick out. The front hub is conical so you'll have to modify the front adapters anyways. I used a file to make them fit, a lathe would be easier. There's a seller on Ebay who sells these for around $75/pair. VBP sells adapters, too but I'm not sure if those are hubcentric.

Here's what my adapters look like (this is the rear axle):

 

I think it would be best to have brakes at all four corners. If all you are looking for is the 1/4 to 3/8 inch you are probably going to need something custom fabricated, unless you are willing to go for 1" thick adapters. Anything custom made is going to cost more than something off the shelf. A thin steel adapter could be made but it would have to be welded on and not bolted on.

 

Wheels that fit specs are very hard to come by - your selection is very limited - the wheel and tire have already been mounted and balance by Nate Jones tire - so we need to make it fit.

carl Johansson

as for spinning - I would think that you have a far greater chance of spinning if only the front brakes were functional - as opposed to only the rear brakes - that assuming you don't lock em up - would have a dragging effect - correct?

You typically don't pop the chute at the end of the run (for this speed and class) it's there as your last resort - popping a chute can have all sorts of other problems associated with it!

 

That makes sense. I forgot it was a straight shot. The rear brakes should be fine.

 

A possible alternative would be to custom machine some spacers that are hub centric (for the car side) and have the correct pilot for the wheel. Then, machine a bolt pattern in the spacers (rotated from the lug hole pattern), and machine the wheels with a corresponding pattern with threaded holes and bolt the spacer to the wheels. Then you have the correct backspace on the wheel. I am in the process of designing such spacers for a set of wheels that I recently acquired.

I know this sounds complicated, so if you need further clarification I will try to explain it another way.

 

Spacers arent a problem if you use studs w/ longer knutls that bite into the spacers (I have it like that), may use additonal (countersunk) allen heads to secure to the rotor. Another way is to use custom rotors and hats where the hats are much thicker, they can't dis-allow running thicker hats can they? You could even make the spacer hubcentric if the wheels have alarge center hole.

 

My Laguna brake kit uses smaller calipers, they might be able to get the clearance you need. Brake torque is almost identical considering the higher coeficient of friction pads it uses....

http://www.corvettengineering.com

 

I was wondering if there weren't some skinnier calipers available Depending on how much clearance you need, it is also possible to grind down the calipers. There is a lot of extra thickness that can be ground (grinded) away. Not sure if there is 3/8" worth tho.

 

Years ago when i was much dumber I aquired a set of 15X10 aluminum wheels with slicks mounted on them. Of course they didn't clear the calipers. So i just took my 8 inch grinder to the face of the mounted calipers and removed a little bit. Then I mounted the wheels (not tight)and rolled them around to make a scribe line of where they were scraping

The aluminum casting was so thick that I was able to grind out the other 3/8ths that I needed.

A smart person has the logical chioce of either installing a smaller Willwood caliper from Corvette engineering. I'd call willwood and find out the exact dimensions of the Daytona bigger calipers and then you could use them for road racing also.

Plan B - Vette Brakes or Van Steel sells Twin turbos idea. They make rotors with aluminum hats. It would be very easy to have a shop TIG weld on a 3/8th spacer

SCTA didn't say anything about my big 2 inch adapters used to clear my 11 inch rear wheels.

This is a real old picture because i still had the rear rubber suspension stops on

You can also see the sway bar to frame spacers that give the sway bar a better working with less angle

 

The Laguna ( Forged Narrow Dynalite ) calipers are 1.9" from the surface of the rotor. kit is $450

The Taladega ( forged Superlite ) calipers are 2.15" from the surface of the rotor. Kit is $510

The Daytona ( Billet Superlite ) calipers are 2.41"from the surface of the rotor. it is $800

 

G'day,
I just popped out to the garage and measured a REAR caliper on a 1981 rear end and the caliper sticks out about 2.5", so the Laguna kit offered by Corvette Engineering should be a good fit. Even the next one might fit, possibly with a bit of filing.

Regards from Down Under

aussiejohn

 

Spacers are a problem - you cannot use spacers on a car running SCTA rules. (bonneville speed trials) I believe there are several other race organizations that ban spacers also!

I'm looking for the safe way out of this - without costing to much money - as soon as we get done at Bonneville - the tires and wheels come off - the 17X275's go back on and we go road racing - so i need a valid reasonably priced option that will be safe!

 

There's huge difference between spacers and adapters. I don't see why some say that adapters are not safe. The adapter is bolted to the axle just like the rim and should fit snug on the hub. The rim is then bolted to the adapter as it would be bolted to the axle.
For additional safety and the warm and fuzzy feeling you can use ARP studs.

I would never sandwich a spacer disc between the rim and the axle, that's simply asking for trouble.

What TT describes is basically a spacer but the knurl portion of the stud holds it tight... not a bad idea...

 

adapters are OK - spacers are not - I am awaiting clarification from their tech inspectors - but I assume a spacer is a disk with holes for the lugs to pass through - while an adaptor is permanently mounted - with bolted to the hub or welded - am I right here?

 

Your correct! What about better brakes or welding?

 

Powertech offers adapters made from steel, these can be bolted, welded or both. Their website is www.powertech.de and is unfortunately in German only (maybe they added the "For English click here" button since I last looked....

 

morning George,

we already have upgraded brakes - and they work great for the road racing stuff we do, so We really don't want to change all of that up.

welding a spacer on would pass tech - but the extra metal will probably unbalance the hub - you could get around that by taking the thing to Nate Jones - he has that patented machine that allows you to balance the complete wheel brake hub setup - while it's on the car. A balanced wheel isn't much good if the brake rotor or the hub structures are not balanced. Turns out getting the whole thing balanced helps significantly - frees up some extra HP.

Nate usually shows up at SCTA speed trials and brings along his machine - we actually loaded Scotts C-3 into the trailer and hauled it all the way to LA to get him to work his magic - ( well - we stopped at spring mountain and willow springs on ther way - just for a few days of fun.) Anyway - he had the tires and rims mounted up - but when we got there - no fitty - the calipers were in the way - crap!

right now we are leaning toward just removing the front calipers - plugging the brake lines - and running. No front brake setups on bonneville cars is quite common - both for safety (less chance of a spin) and because it reduces significantly the rotating mass of the front wheels.

We will be out there sept 13 - 16th - you gunna make it out there this year?

Carl