Upgrade Rear Wheel Brake Cylinders to 3/4 "

[formula_raider]

I was wondering if anybody knew a manufacture and part number for the 75 Opel Manta wheel cylinder that alot of Opelers are installing in the rear of their GT's for increased stopping power.
I understand that they are 3/4" or 19mm bore.
I did a search and found: Autospecialty W-13002 was a good number and tried to get it through autoparts giant. Well, they recently stopped carrying Autospecialty...too bad because they were $ 10.54 a piece. Parts America said the same and cannot find a listing for the 3/4" bore. Does anyone have a manufacture & part number for these cylinders? Thanks,

[jordan]

yea, I as well wanted to improve my braking by upto 20% with a $25 upgrade. But I have not been able to find a place that sells them other than ogts and it is no longer a $25 upgrade then.

[simplemind7]

www.rockauto.com has them for $19.25, i've never ordered from them though

[formula_raider]

That item is a Beck/Arnley 0721548 which is a stock 5/8" Bore for a GT. Still cant find a good number/manufacture besides Autospecialty for the 3/4" bore

[nobody]

Who are you guys talking to? Out of the factory for 25.99 in 4 days standard shipping. I just had a check of stock done on them and they are in stock.

http://www.partsamerica.com/ProductD...pe=232&ptset=A Ok I was wrong but I think I may have figured it out.

[nobody]

Ok try this one, 3/4 inch bore rear cylinders with the same spacing and 1 mm difference in mounting bore and uses the same line connections. 16 bucks in stock and Opel too. Pop quiz anybody? oh 16 was for a pair not each. Guess the model.

[nobody]

Come on, don't tell me I was the only one that remembered the link. Early 80s Opel.

[nobody]

Ok, yet another hint. they were imported by GM and used an Opel platform and I believe an Isuzu motor. It was similar to a Kadette c or d and rebadged. This was a low seller and pretty much a POS but yeilds newer Opel parts if you look close. Europe got the cross flow 400 with Recaros and the US got a POS about the same year. Come on, I can't believe there isn't even a guess on this one. I about got one just because it was an Opel.

[LeftLaneGuy]

Duh! (I can't believe no-one else has answered)

Pontiac LeMans..
Actually, I know a guy in TN who has one (GSI) that has the opel motor in it. No Sh**! and recaros as well.. He won't sell it for anything. Badged as a pontiac. Says he bought it off a dealership in VA, Wish I could get it from him

-Dave

[oldopelguy]

The Lemans (91 vintage) was basicly a re-badged Opel, but it came with 11/16 wheel cylinders. Not sure yet on the mounting stuff, but it looks close enough to warrant me ordering one to get a good look at.

I think Dave must have been refering to the Chevette, which came with 3/4" wheel cylinders and also looks pretty close. Again, I just ordered one of those to get a good look at too.

Another option might be the Opel Isuzu's 13/16 wheel cylinders, but they mount enough differently to make them a distant third choice, unless you really need more rear braking that is.

[nobody]

Stephen you had me worried there for a second. The LeMans actually came with 3/4 cylinders. Raymold part # 2037625. mount is 1 mm bigger bore and not tapped but uses a clip. if you wanted to drill and tap it as original it would be easy. length compressed is the same as a stock piston as well as offset from mounting face and brake line fitting is the same too. The end bores are 1 mm bigger so it would require a slight opening up of the brake shoe opening, but I haven't measured a pair of shoes yet to be sure yet. All in all, off the shelf and the slight differences are pretty small compared to the cost. I could put those on in about an hour.

I'll stash those for the wagon, I'm happy as hell with the brakes on the GT.

[nobody]

It was all pretty funny. I called to ask for Opel ones and got the wrong ones quoted to me. I let him know that was incorrect and explained why. He started digging through everything he had trying to find it, he came up with nothing for a 75 Manta. He started talking maybe a cross refference of some kind and I threw out the LeMans for him to try. Mount, bore and spacing all were extremely close. I pulled a stock one for comparison and went to have a look see. He was so impressed that I hit it so close he dropped the price on them 2 bucks. I then used the company discount to drop the price another 15 % and make them tax exempt. A little more and I may have walked out with cash too

[RallyBob]

Originally Posted by nobody Ok, yet another hint. they were imported by GM and used an Opel platform and I believe an Isuzu motor. It was similar to a Kadette c or d and rebadged. This was a low seller and pretty much a POS but yeilds newer Opel parts if you look close. Europe got the cross flow 400 with Recaros and the US got a POS about the same year. Come on, I can't believe there isn't even a guess on this one. I about got one just because it was an Opel.

You're right Dave, it was a POS. I had an '88 model (based on the '84 Kadett E) back in '91-'92 or so. The body was made in Korea by Daewoo (ironically from European dies, because if you removed the rear plastic panel the Euro license plate recession was still there), the engine was a German-designed, Brazilian built OHC unit, and the interior was typical GM (blah....).

However, not withstanding the terrible cowl-shake from the poorly engineered dashboard tie-bar, the car actually performed okay. I mean, it was pig slow (I had the 1.6), but with new struts and wheels/tires, it actually cornered very well. I autocrossed it once, it ran in CSP because of the tires, and I won out of a class of 7 other cars (all Civics). You just stuck your foot to the floor, banged it off the revlimiter, and steered. It is still the only front-drive car I've driven that oversteered at the limit.

I wouldn't mind finding an intact US body/Vin number and importing a GSE/GSI driveline from the UK or Germany with the 2.0XE engine all the driveline goodies. Too many projects though....

Bob

[tom_laan]

i'm looking for big brake cylinders too. a mechanic at work said i should look for 22mm brake cylinders. what is your opinion on it? i searched around but didn't find them yet. anyone know an adress to get bigger brake cylinders dan stock? stock is like 19mm am i right? or was it 17mm? want to know what you people would advise. and where to get them (prefered europe)

cheers
tom

[GoinManta]

Just confirmed with Opel GT Source.. It wasnt just Autopartsgiant, etc.. that arent carrying Autospecialty anymore.

Autospecialty, has gone Chapter 11, and will be liquidating. What this means is online resources, Autopartsgiant.com, Rockauto, etc.. may list an Autospecialty part # and price. But will not be able to get the part anymore. In a nutshell, what few parts we could get that were Opel specific from online and local retailers. Has been cut even further.

More reason to support Opel GT Source for new parts, he will be the only one big enough to order a few thousand dollars worth of wheel cylinders, or rotors, etc.. etc.. etc... so we can have them. He will definately be the only big enough to reproduce parts when they are no longer available even in Europe. He has proven that by reproducing lower ball joints, radiator hoses, shift boots, lenses, etc.. for the GT (and in a few cases the Manta).

Charles

[nobody]

I was down at the shop and finally remembered to take a wheel cylinder with me. The pistons fit standard brake shoes. No interference issues. Only thing is the round section that goes through the backing plate. Stock is 28.6 these are 29.6. Internal stock bore is 15.8 and these are 19. It looks like 20 bucks and a drill bit and you get big brakes...

Don't get me wrong, I really appreciate OGTS. I like being able to go to the local parts place and pay 1/6 to get the same result. Then again, Dennis and Gil 10 minutes of machining and I wouldn't have known the difference.

[nobody]

Before I put these in anything I wanted to do some number comparisons. Total stroke was one as well as piston center and piston position from the back plate.

Total stroke is 95 on the big one and around 100 on a stock( I don't think I'd feel good running it out that far tho on the stock ones).

Both pistons are on center to the bore for the backing plate.

Piston center line for the big one is around .6 closer to the backing plate and total depth is the same.

One other issue I'm wondering about is the stock Opel one has a 2 piece piston or piston and push rod type. The bigger one is a one piece. Can anybody tell me what a big brake 75 Opel one is like?

[nobody]

Ok as good of a time as any to speak it. The brakes on my GT may possibly be the best they can possibly ever be. I have gotten a bunch of parts to try out for others that I really don't have a need for, these cylinders are a perfect example. I asked if some of you that know what the stock ones are like and I got stuck talking to myself. I've screwed up so many ways and times it's hard to imagine and could be doing it again. Why is it if I'm trying to help the group as a whole I get to talk to myself? I don't know it all or think I do, I ask questions too. Can I Please get some help when I ask without having to beg?

[namba209]

Dave, I could be guessing here, without the 75 FSM, but my Clymer's shows all rear wheel brake cylinders as having dual pistons, from 66-79. Don't know if that will help or not, but it's a start.

[tom_laan]

you got a photo of your's? i only know how mine lookes like and they are stock. so can't help you on that, whas hoping someone else had an answer to it. what opel had those bigger wheel cylinders on stock? it's really hard to find those things here. and maybe later models opel with 19mm would fit gt.

[nobody]

I can't believe all those that have the larger cylinders or have at least seen one can't spare the time to at least give a description. Are they a floating type like stock? I'm not looking for somebody to endorse the ideas I've had just a description from somebody that's worked with the stock 75 ones. I never have so all I can do is ask and try. Come on people

[bq97]

I have a spare 3/4" wheel cylinder. It is exactly like the smaller ones with a larger bore.

It appears to me the inlet and bleed screw are reversed on the LeMans wheel cylinders. Is this true?

hth
Brian

[nobody]

yes they are reversed, is the 3/4 a 2 piece piston type?

[jerseyopel]

Will all of the air bleed out if the bleed screw is on the bottom??

[nobody]

yes that is no problem. it can be mounted either way.