Big Brake Kit

[Sparky73]

Seen this on eBay and thinking about purchasing. Is this a home fabricated kit, or something that was produced at one time?

Also.. this should fit a GT, correct? I would love to have 4 wheel disc brakes!

eBay Motors: Opel GT/Kadett/Manta/Ascona Big Brake Package (item 290168579912 end time Oct-14-07 12:49:47 PDT)

[opelnut10]

Originally Posted by Sparky73 Seen this on eBay and thinking about purchasing. Is this a home fabricated kit, or something that was produced at one time? Also.. this should fit a GT, correct? I would love to have 4 wheel disc brakes! eBay Motors: Opel GT/Kadett/Manta/Ascona Big Brake Package (item 290168579912 end time Oct-14-07 12:49:47 PDT)

That is stock set of 75 calipers and rotors and larger rear brake cyls. that can be bought a Rock Auto for a lot less money that that. They are not custom made and yes, they will fit on a gt but you will not have four wheel disc brakes. The drum brakes with the bigger wheel cyls. properly adjusted along with the bigger 75 front brakes will stop a GT quite nicely unless you are going to do a lot of extreme braking, in which case you need something better than that setup, save your money.

[hrcollinsjr]

Originally Posted by opelnut10 That is stock set of 75 calipers and rotors and larger rear brake cyls. that can be bought at Rock Auto for a lot less money than that.

The seller is a reputable list member here. You might want to do the math before you make the above statement, I'm not so sure you are correct. Also I believe I see the metal brake lines that have the correct ISO bubble flare that is needed when converting to the larger front brakes. I believe this to be a complete setup.

Harold

[BQS4]

It is a COMPLETE set-up ready to bolt on and bleed out, nothing else is needed. A Saturday afternoon of easy wrenchin' and you've upgraded to about the best brakes you can.

[rowdygt]

It all depends on how high the bid goes...but right now it's a bargain

[David McCollam]

Hi,

Yes, that seller is a site member with a flawless reputation. If you read, nowhere in the listing does it mention four wheel disc braking. Also, you might be able to purchase all those parts at Rock Auto for less. Let's add it up shall we:

Delco Remanufactured caliper-left $49.79, core $26.40-total $76.19
Delco Remanufactured caliper-right $49.79, core $26.40-total $76.19
Beck-Arnely Semi-metallic pads $13.63
Rear brake shoes-Raybestos $23.79
Autospecialty-3/4" wheel cylinders OGTS $54.00 X 2 $108.00
Rotors-OGTS $65.00 x 2 $130.00

Total $427.80

This doesn't consider the '75 backing plates included to fit the rotors or the hard line ISO flare brake connections. True, the calipers aren't rebuilt, but the hard parts are worth about $400, plus you don't have to go all over the country looking for them. That might be worth something.

[opelbits]

A couple of things to add,

I have heard of problems getting actual 75 calipers from suppliers other than OGTS.

I also understand that you should use a brake proportioning valve with the big rear cylinders.

Not to slight OGTS, but I found the 75 rotors at Tirerack for right at $100 for a pair, shipping included. They were Brembo, too.

Does anyone know offhand if there is a problem using the stock 74 and earlier front brake backing plate with the 75 disc and caliper?

[BQS4]

Originally Posted by opelbits Does anyone know offhand if there is a problem using the stock 74 and earlier front brake backing plate with the 75 disc and caliper?

Yes there is, I just did this on my wife's 74 Sportwagon, had to trim the backing plate a little, but, that's what Dremel tools are for :-) You don't have to trim much, but, the 75 calipers won't go on without the trimming being done. As for the 75 calipers themselves, the 77-83 BMW 320i with the ATE system was the same caliper, and as with anything else, ordering something as a BMW and not an Opel, it's cheaper.

[Phoenix]

A lot of those parts are disc'd. NO ONE still carries the 3/4 in the states that are the correct ones. This has everything. You don't have to make anything or cut anything and you won't have to buy anything else unless you. You might need to turn your rear drums and get new rear hardware(probubly not needed). Every once and a while someone sells loaded calipers on Ebay for like 125 for the set but you have to everything else in the kit. Even getting the cheapest parts that you can find, I don't think that you can come out as good as this auction may go, I know.

[Gumby]

And here I was hoping no one would notice it :P

[opelnut10]

Originally Posted by hrcollinsjr The seller is a reputable list member here. You might want to do the math before you make the above statement, I'm not so sure you are correct. Also I believe I see the metal brake lines that have the correct ISO bubble flare that is needed when converting to the larger front brakes. I believe this to be a complete setup. Harold

I never said anything about the sellers reputation all I was saying was that it was not a 4 wheel disc brake system as was brought up in the posting by Sparky73. If my posting was taken in the wrong context then I am sorry you took it that way. If it stays at the present bid it is a deal for someone that does not want to take the time and research what is available for making this same swap using BMW stuff. I bought those wheel cyls. about 6 months ago from Rock Auto for less than $20 each.

[Phoenix]

Autospeciality 19mm rear wheel cylinders have been disc'd for quite sometime. You can get the 5/8 but not the 3/4 like Dave is selling.

[yellaopelgt]

Arent there other issues with this set-up as well? Meaning that the original GT rims wont fit? (if its even going to be put on a GT) And, the original calipers are already biased to the front so adding more stopping power on the front really isnt the best idea.The larger rear cylinders wont compensate for the big calipers. A proportioning valve might be a good idea...but geez...seems like alot of money and work for the effort.
I havent done this, but it seems like there should be a cheaper way to do it....then again, if there was I would have done it already.
I've heard that GTJIM did a rear disc set-up for someone a while back but not sure how it was set-up. Maybe he can elaborate???
Joe

[jordan]

From my understanding certain GT wheels will work and others will not, it is known that the multi-hole wheels are a no go, but I believe that the 4 oval slot '70 gt wheels are supposed to clear (*not confirmed by me though*) The rear wheel cylinder upgrade along with some high quality brake shoes (originals can be relined with modern friction material compounds) and that right there can make a HUGE difference, I have stepped up W/C sizes in other cars and it is very noticeable. Also as a brake proportioning valve is a good idea and should be great for dialing it all in, but if you were concerned with the front having more robust brakes at an already bias why would you be concerned with lessening the rear brakes? I have done a lot of research on this and this seems to be the biggest bang for the buck. Shopping around I purchased (2) rebuilt calipers, (2) rotors, Front set of brake pads, rear shoes and have a total right now of $150 into it. Now if I can find the rear 3/4" W/C at a reasonable price I will be in business for $200-250.

[BQS4]

Originally Posted by jordan but I believe that the 4 oval slot '70 gt wheels are supposed to clear (*not confirmed by me though*)

I can confirm this, at least by my wife's 74 Sportwagon. I upgraded her front brakes to the 75 calipers (had to trim the backing plate a little), but, I put her 74, 4 slot wheels back on and they clear, she has been driving this car for like 60 miles a day back and forth to work, no problems.

[GoinManta]

Brakewarehouse.com – Brakes, Brake Pads, Brake Rotors, Calipers has the rotors for the 75 for $48

You can get them to custom drill or cut the rotors too..

About two years ago.. I had problems getting 75' calipers (or let me say BMW calipers).. problem being was I was constantly getting rights.. (It may have been the other way around) but I ordered a set and got two rights (or lefts) , this happened like 6 times in a row between NAPA, Advanced, and Autozone.. Finally I got a left (or was it a right) on the 7th try. Told others were having this problem too..

But I could order them.. just getting the correct one was the problem.

Brakewarehouse lists them for $49 each with $20 core.

Charles

[opelbits]

Originally Posted by yellaopelgt Arent there other issues with this set-up as well? Meaning that the original GT rims wont fit? (if its even going to be put on a GT) And, the original calipers are already biased to the front so adding more stopping power on the front really isnt the best idea.The larger rear cylinders wont compensate for the big calipers. A proportioning valve might be a good idea...but geez...seems like alot of money and work for the effort. I havent done this, but it seems like there should be a cheaper way to do it....then again, if there was I would have done it already. I've heard that GTJIM did a rear disc set-up for someone a while back but not sure how it was set-up. Maybe he can elaborate??? Joe

Look at it this way, how much does it cost to rebuild the stock brakes? How much more to go with the 75 stuff? If they need to do it, it's not that much. If they just want to, but don't need to, then they shouldn't whine about the cost. We aren't talking Brembos or Wildwoods, here.

I've got the 75s on my GT with 74 Manta wheels. There is a slight amount of grinding I had to do on the calipers, but nothing exstensive or in a critical area. I posted a thread about it. As I understand it, the proportioning valve is not needed unless you go with the 3/4" rear cylinders as well. If the 75's used the same valve as the 74, then it seems necessary only when using the 3/4" cylinders.


I can say that the 75 fronts are well worth doing. The stock brakes are good, but the 75 fronts are impressive. Especially when you consider the cost to install them. If your brake system is up to snuff, new rotors and new or really good unturned drums, new pads and shoes, good master/booster (no vacuum leaks), then the power of the 75's will really surprise you.

[Killer Texas GT]

It is well worth it to upgrade to the 75 Big Brakes for the GT, I haven't had an opportunity to use the 3/4 rear cylinders though. So I can't say if a proportioning valve is required with the 3/4 cylinders. I do know one is not with the 5/8's GT cylinders.
GTJIM's rear disc package consisted of an custom made bracket to replace the rearbacking plate of the GT with some offset in the bracket and cut out and drilled for installing the Caliper and Rear Disc Rotor (solid) from the Piazza. For us in the US it is the Isuzu Impulse 83 to early 87 and these disc are vented, which Charles Goin has written up a Technical How To, and can be found it the tech library I believe. He adds a proportioning valve also, but my personal experience with the 75 big brake package on front and the Impulse package on the rear and using the stock GT master cylinder and booster I saw and felt no need for the proportioning valve.
Now whwn installing the 75 calipers on the GT I recommend using the 75 dust shield and remember to install the bleeder fitting to the top with the line side coming in the bottom of the caliper, you will need to re-shape the ISO bubble much like the GT ISO bubble.
In either case this is definitely a great improvement over the stock GT braking system, as you are adding addition surface area to your brakes, thus allowing you to stop quicker.

[Lindsay]

http://www.opelgt.com/forums/showthr...ferrerid=14028

[Lindsay]

GT uses J-brake tube (hard line) that:
Connects to caliper, routing to caliper bracket.
J-tube connects to flex hose, w/ brake clip to hose & caliper bracket.
Then, flex hose routes to chassis hard line, securing to chassis w/ brake clip.

1975 Big Brake fitting connection at caliper is ISO Bubble flare.

Anyone know where to source the exact adapter fittings to go from the pre-75' brake line to the 75' manta caliper ISO Bubble Flare? (Other than OPGTS Kit?)

[opelbits]

The J tube from the GT is not used when installing the 75 brakes, as far as I know. The line in on the caliper is in a different place (higher I think), so if you use the small brake backing plate, the tube will not fit up to the caliper and the bracket on the backing plate.
I used the 75 backing plate, 75 hard line, and OGTS braided flex line. Maybe some adapters, too, to go from the flex line to the hardline that connects to the caliper. I will take some pics of what I have.

[Killer Texas GT]

Here I cut the upper section off of the right side bracket and installed it on the left side and the same for the right side useing the left bracket.I used the 'J' line from the GT (or use the hard line form the 75 caliper to the flex line) it was a matter of ajusting the bend of the line into more of a 'C/V' or 'U/V' shape which left the flex lines in the same location on the GT, instead of having to route the flex hose from the front of the suspension to the back side of the suspension to the GT hard line.

[jordan]

I don't really know what went wrong when ordering the parts, but the calipers are correct and 1980 bmw 320i calipers, the rotors I bought as well as bmw 320i rotors and they do not seem right, the crown center section is higher (stock gt is about 1.75", bmw is about 2.50") The holes are also larger and may be at a slightly different spacing, the bore in the center of the bmw rotor is smaller Is this correct? I have not tried attaching the rotor to a hub yet. Did I misunderstand the rotor aspect of the upgrade?

[RallyBob]

Originally Posted by jordan I don't really know what went wrong when ordering the parts, but the calipers are correct and 1980 bmw 320i calipers, the rotors I bought as well as bmw 320i rotors and they do not seem right, the crown center section is higher (stock gt is about 1.75", bmw is about 2.50") The holes are also larger and may be at a slightly different spacing, the bore in the center of the bmw rotor is smaller Is this correct? I have not tried attaching the rotor to a hub yet. Did I misunderstand the rotor aspect of the upgrade?

Calipers from non-vented 320i BMW's are the same as 1975 Opel calipers. You must use 1975 Opel rotors with them.

Bob

[neuropel]

Jordan,
Do you have part numbers? When I did this upgrade, I used rotors for a 75 manta. If the rotors you have are truly for a 320i, at LEAST the spacing for the lugs should be right. It might pay you to do a search here to verify.
Todd