School me on GT front brakes, hubs and knuckles

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School me on GT front brakes, hubs and knuckles

Postby wolf » Mon Apr 22, 2019 4:29 am

I have a 1970 GT front suspension set up, with Girling disc brakes, where the brake rotor bolts on to the back of the hub into blind holes. I've seen pictures of other HB disc brake set ups where the rotor bolts through 4 flanges on the inner side of the hubs. The OEM service and parts manuals show both illustrations. I can't find enough info on which models used what in the manuals I have.

Here are my questions:

1. Are just the calipers different between the Girling and Lockheed disc brakes, or are the hubs, rotors and steering knuckles also different?

2. Is the Girling setup I have only used on the HB GTs, or was it used on later models too (and possible other OEMs)?

3. How hard is it to find replacement hubs and steering knuckles for my set up?

4. Does anyone make a high performance replacement disc (drilled and slotted) that will bolt up to my existing hubs?

5. Are there hubs from other applications (with more brake options) that will bolt up to my existing knuckles (ideally with a 4x4.5" bolt pattern)?

Thanks much,

Ed
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Re: School me on GT front brakes, hubs and knuckles

Postby lord13 » Mon Apr 22, 2019 7:49 am

A picture of what set up you have would help because as far as I know all the discs bolt up the same, but I will try to answer your questions...

1. All hubs are the same in the way they bolt up, but on the OHC ones the caliper bolt holes are further out from the center to enable larger discs.

2. Girling set up was used on OHC and OHV viva's,, the lucas set up is the later system.

3. Very hard, everyone wants them.

4. Possibly, I don't know.

5. People have fitted escort hubs, or you can get ally ones made up with any bolt pattern you want.

Incidentally viva hubs are 4 x 4" PCD not 4 x 4.5"

So there you go... I may be wrong on some points as I only know about domestic models and exports may have been different, I'm sure some one will set me right :)
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Re: School me on GT front brakes, hubs and knuckles

Postby 1972nail » Mon Apr 22, 2019 10:21 am

You can fit vented Renault Savanna discs to the original hubs with a slight modification.
viewtopic.php?f=22&t=7157&hilit=savanna

You can fit the imperial Girling P16 or the more readily available metric Girling M16 caliper or it's F@#d ATE equivalent which was fitted to European Crapees etc.

Strictly speaking you need special bolts with imperial threads and metric shanks to fit the metric calipers, however, I have, along with a few other people, fitted them with the original imperial bolts, some Locktite and not had any problems. You will also need a special metal brake pipe with imperial fittings on one end and metric on the other. These calipers can be spaced for vented discs too.

Vented discs of the same diameter as original will NOT increase braking power, they will only improve performance in extreme temperature conditions encountered in racing or prolonged heavy braking such as towing in hilly areas.

The M16 caliper upgrade is very worthwhile as it increases both piston area and friction material area, both of these have direct bearing on braking power and are immediately noticeable. You may notice a little more pedal travel as the calipers will need extra fluid pumped into them to work.
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Re: School me on GT front brakes, hubs and knuckles

Postby wolf » Tue Apr 23, 2019 3:17 am

Thanks for the info guys. I will check out that other thread, but I'm all about weight, so not really interested in big vented rotors (10" is about the limit for the wheels I have). Was just wondering if something like this exists in the aftermarket that will fit the GT hubs: https://rimmerbros.com/Item--i-208715XD

lord13 wrote:A picture of what set up you have would help because as far as I know all the discs bolt up the same, but I will try to answer your questions...

1. All hubs are the same in the way they bolt up, but on the OHC ones the caliper bolt holes are further out from the center to enable larger discs.


Here are the 2 types I was thinking about. The first is my GT setup, the second I found somewhere on the interwebs, on a thread about HB Vivas, but now I have to wonder if it was HC, or something altogether different:



lord13 wrote:2. Girling set up was used on OHC and OHV viva's,, the lucas set up is the later system.

3. Very hard, everyone wants them.


OK that changes my plans. I don't want to modify (and possibly mess up) something rare and desirable.

lord13 wrote:4. Possibly, I don't know.

5. People have fitted escort hubs, or you can get ally ones made up with any bolt pattern you want.


Escort hubs fit right on the Viva spindles with no modifications? What year/model Escort? Having my own custom aluminium hubs made isn't completely out of the question, but then I'd likely change spindles to something less rare at the same time.

lord13 wrote:Incidentally viva hubs are 4 x 4" PCD not 4 x 4.5"


Yes, I need the 4x4.5" to fit the street (14" Rostyles) and race (15" Draglite) wheels. Hence why I was considering modifying the GT hubs.

lord13 wrote:So there you go... I may be wrong on some points as I only know about domestic models and exports may have been different, I'm sure some one will set me right :)


I do appreciate the info. Across the pond here, there's very little knowledge of these cars, and parts interchangeability with other cars is a complete mystery. I have both the UK Vauxhall OEM Service Manuals, and the GM Canada Envoy Epic & GT manuals (and GM parts book) but there's so little information in them, compared to all the other OEM manuals I have for my other vehicles, so they're not much help.

New question: besides the Girling vs Lockheed brake differences, what are the differences in front disc brake setups between the HB GT, the non-GT HB discs, and the HC stuff (as far as spindles, hubs, rotors and caliper interchanges go)?

thanks again for the help,

Ed
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Re: School me on GT front brakes, hubs and knuckles

Postby lord13 » Tue Apr 23, 2019 8:35 am

wolf wrote:New question: besides the Girling vs Lockheed brake differences, what are the differences in front disc brake setups between the HB GT, the non-GT HB discs, and the HC stuff (as far as spindles, hubs, rotors and caliper interchanges go)?



Ed


HB and HC OHV uprights ( stub axles) are the same ( small diameter disc )

HB GT and HC OHC uprights are the same ( large diameter disc)

HB, HB GT, and HC hubs are the same.

Exeception to the rule I think is the Droopsnoot Firenza but I'm not sure on that

HB and HB GT uses single circuit girling servo

HC uses dual circuit Lockheed(lucas/ac?) servo ( some early ones had the girling single circuit i think )

This is as far as I know, anyone with different info please feel free to jump in and correct me :)
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