Opel GT rear disk brakes

[blancojp]

Howdy all!
I have gotten lots of requests to post what my rear brakes look like. In a nutshell, I have Honda 262mm rotors with Cadillac aluminum calipers. The bracket for the calipers I made in house and it is welded to the read end shaft housing.

The same bracket can be used on the front spindles to mount Howe calipers with Honda rotors. Here are a few pics and once I get the garage going at my new location, I will be making a few of these kits.

[namba209]

JB, with what appear to be spacers on the spindles, how far out will that move the wheels from the original location? Right now with the slotted aluminum wheels on Willit? both front and rear tires are just inside the widest part of the wheel wells. I wouldn't want to go any farther out than they are now. The CHP could get technical on me and make me get wheel flaps or narrower wheels. They normally don't mess with us custom rod folks, but there could come a time.........

[tom_laan]

could you make a pricelist of the parts used?
that would be very helpfull.

[Mike Preble]

Ron,

I have the same 1" spacers on my car so I can use the FWD rims on my GT. My rims fit perfect under the wheel wells as the tires are in the same position as the origonal wheels and tires. I am able to use 15" rims with those spacers. I have never had problems with wheel bearings or the nuts coming loose. But I can stick some big brakes under the rims.

The only loose nut is the one behind the wheel.

Mike

[blancojp]

Ron:
I have 25mm wheel spacers because my alloys have a 38mm offset made for front wheel drive cars. With a 195/50/15 in front and 205/45/16 in the rear, the car has a massive stance but neither wheel extend out from the fenders.

To transport the car sometimes I use Saturn metal wheels which are made for front wheel drive applications. I have also tried different wheels with 4x100 bolt pattern but the available area is limited and most brake upgrades will not work.

To be sure everyone understands, you can't use any type of Opel factory wheels when you install this setup, 14" wheels are the smallest you can use.

On my new Opel, I will install 330mm front rotors and 262mm rears which should stop the car rather nicely.

[namba209]

Rats. I won't be able to use your prospective brake upgrade then. All my wheels are 13", and I've got a few bucks invested in getting them chrome plated, 8 right now with one more to go. Maybe further on down the road, before I start on the monza.

[blancojp]

Ron how about this....
Instead of the 262mm vented rotors, you can use a 240mm solid rotor, the same bracket and a Honda rear caliper. The profile is 10.67" which gives you a grand total of 0.375" clearance with mag wheels. This setup can be also used with the stock Opel rims.

[cherokee]

Sounds along the lines of what I did. For FP I have to have solid rotors on the rear of the car. I ended up with 90 CRXsi rotors, I also used Honda calipers. It was pretty simple. I don't know if the stock master would work on my setup, but it was an easy install.

[namba209]

Thanx for the input guys. At least I know there is some avenues for improving the brakes even with the 13" wheels. I haven't had the need, so far, to really check out my brakes, which are newly overhauled/replaced OGTS units. Of course most of my driving is on the surface streets and freeways here in SoCal, not a lot of twisty turnies, that would need some serious braking if I was to do some spirited driving. I'll have to make an effort to really do some panic braking, to see what I actually have or don't have and go from there.

[Paul]

I don't know about anybody else, but I can't a thing in the pictures above... Y'all are asking questions about items that don't even show up in the pictures... what gives?

PS I see the spacers, but that's about all I can see...

[cherokee]

The honda setup that I have fit nice under stock Opel 13" wheels. But again I want to say I don't know if it will work with the stock master. Others might know, but messing with brakes is something you want to do only if you know what you are doing.

[blancojp]

The stock master cylinder will work just fine with this setup. The pedal however will travel an additional 3/4" to meet the new compliance. I have a Honda master cylinder my car which has a 22mm bore and takes care of the compliance issue. Since I increased the volume slightly, I also increased the diameter of my booster to 9" compensate.

I have not figured out what to do with my new Opel yet but any and all upgrades that I do will be posted here step by step.

[PROPEL]

Ha! All you clowns upgrading your brakes...

What you really need to do is downgrade your car. Yup, that's right—swap in a 1.1L drivetrain, and the stock 1.9L brakes will be more than sufficient.

(Alright, I thought it was funny.)

[tom_laan]

haha lol. i think it was funny too :P

[blancojp]

Hi All!
I got a few calls for the rear disk brake caliper brackets. I got 30 sets on order and should be here in the next 10 days or so. They are mostly promised however there are a few sets still available. Let me know if there is any interest on the few left over.

These are for Honda rear solid rotors and calipers which fit the stock Opel 13" wheels. Drawings in Cad or Solid works are available and fully dimensioned just in case you want to build your own.

[jordan]

Great to hear! I am glad you are making a product/kit available to the community.

[opelwasp]

Price for brackets?

I'd like a copy of the CAD/Solid

[GoinManta]

Originally Posted by blancojp The stock master cylinder will work just fine with this setup. The pedal however will travel an additional 3/4" to meet the new compliance.

How did you mate the Honda Master Cylinder to the Opel?

How did you compensate for the float in the rear axle.

When I intially built the Isuzu Swap, it was noted the difference between the early GT and Manta rear axles caused a problem. Supposedly since the early axles are held in by clips they float and that would cause problems with installing rear discs on pre72 axles. Have you seen that as a problem? I am curious as I am wanting to convert my Kadett to rear discs as well.. but I know it will have the clip style rear axles.

Charles

[blancojp]

1) How did you mate the Honda Master Cylinder to the Opel?

I drilled the mounting holes closer together and attached it to the Opel booster. After a minor pedal adjustment, hook all lines and you are done.

2) How did you compensate for the float in the rear axle.

The rear calipers are floating on the brackets so any axial displacement of the axle will not affect the caliper/rotor disc combo. I have this setup on the '72 and works just fine.

Problems develop only if you use a fixed caliper on the rear wheels. The Isuzu setup also has a drum brake built in however the Honda calipers have this built in so it eliminates any fixed point. I have GM metric calipers from an Eldorado in the rear with a 262mm vented Honda rotors, never had a problem since they were installed back in 1996.

[GoinManta]

AWESOME !!

Would love a copy of the CAD file (ACAD is best, but I can work with Solidworks)

Got part numbers for the Master Cylinder, and the Calipers?

Also what did you do for the ebrake cable? Modify a Honda one?

This sounds just like the solution I was looking for, for my Kadett..

If I go forward with the EV Conversion I will need really strong rear brakes to handle the extra wieght.

Charles

[blancojp]

Here are the CAD and Solid works drawings in PDF format.

1) Part 1 is the bolt on bracket for the Honda calipers. This one uses the rear solid rotors and calipers from a CRX.

2) Part 2 is the welded bracket for the Eldorado calipers. This one uses the GM metric rear caliper with a Honda Prelude front vented rotor.

Both brackets will work with all rear ends. Part 1 however needs the holes drilled depending on which rear end you have on your car. There are differences in the stud location which must me marked directly from the target unit. Both brackets can be installed without removing the axles by just cutting the bcaking plate flush with the axle flange.

I should have a few sets of these done in the next few days. I believe the cost was in the $25 ea. area however I will not know the exact amount until they arrive.

Have fun.

[Nathan Acree]

I sent you a PM, but just for the record I would like a set if there are any to spare. Just tell me where to send the money-

Thanks,

Nathan Acree
Albuquerque New Mexico

[blancojp]

Originally Posted by GoinManta AWESOME !! Would love a copy of the CAD file (ACAD is best, but I can work with Solidworks) Got part numbers for the Master Cylinder, and the Calipers? Also what did you do for the ebrake cable? Modify a Honda one? This sounds just like the solution I was looking for, for my Kadett.. If I go forward with the EV Conversion I will need really strong rear brakes to handle the extra wieght. Charles

The master cylinder used is from a Honda with (or without) ABS from any year '85 to '95 or so. They are all the same and made by AISIN with the exception that the reservoir is slightly different. The rear calipers are from any 4 bolt Honda Prelude with solid rotors. Honda uses the same calipers for all their smaller vehicles so just use what it is available.

The E-brake cable I use comes from Lokar, works with the existing Opel hardware and it is adjustable to any length. There are other options but they require a bit of modification.

[BQS4]

JP;
I'll take a set of the rear brackets. Just let me know when and where to send the money

[yellaopelgt]

I'm in as well if there are any left over......
So whats the cheapest way to go here?Parts wise=cost
Part1 with Honda CRX calipers and the solid rotors or
part2 Eldo calipers GM metric calipers w/prelude vented rotors
obviously the GM needs to be welded so taking that into consideration, I'd opt for part1 since its a bolt on.
Joe