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Opel GTE rally car - two brake boosters for the front circuit?


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#1 Kneifzange

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Posted 01 April 2024 - 16:19

came along this picture from the Opel GTE rally car of RAC 1978

looking into the engine booth I see two in-line brake boosters.

Why two brake boosters?
How they are connected to the circuits?
One to front circuit one to rear?
Or only to the front circuit, one to the left, one to the right?

Don´t understand the layout.....
and the idea behind

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#2 BRG

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Posted 02 April 2024 - 10:39

The production Kadett C models all had dual circuit brakes, discs at the front, drums at the rear, with a servo.  

 

I believe the Kullang car on the 1978 RAC was running in Group 2 spec (which they won, taking 5th o/a) and this allowed the fitting of rear discs.  It is possible that the extra servo operated on the rear brakes and could be connected or disconnected as a form of brake balance for gravel or tarmac surfaces respectively.



#3 Magoo

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Posted 03 April 2024 - 07:53

I can't make out anything in the photos and rally cars are not at all my area, but aren't they equipped with cutting brakes?



#4 BRG

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Posted 03 April 2024 - 09:04

I don't know what cutting brakes means?  If it is some sort of brake balance adjustment, we are talking about 1978 when such things were not so common, especially in rallying, or may not have been permitted under Appendix J Group 2 regulations.



#5 Magoo

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Posted 03 April 2024 - 16:37

A cutting brake aka turning brake is an extra hydraulic circuit for the rear brakes operated by a hand lever. 



#6 gruntguru

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Posted 04 April 2024 - 02:12

If the car was equipped with an adjustable bias bar operating front and rear master cylinders it would require two boosters - one for each MC. (picture shows in-line boosters not pedal boosters)



#7 Lee Nicolle

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Posted 09 April 2024 - 08:33

If the car was equipped with an adjustable bias bar operating front and rear master cylinders it would require two boosters - one for each MC. (picture shows in-line boosters not pedal boosters)

You can run an inline balance adjuster. And only boost the front brakes. Did than myself at one stage on my Sports Sedan. Idea was ok, booster needed more manifold vaccuum which I really should have known. 

Many late 60s cars did just that, boosted the front discs and not the rear drums. Here in Oz Valiants and Falcons did that. 

Seperate boosters for each end could be done but really why? 

As for 3 wheelers, they are all dangerous and should NEVER have been allowed on the roads. Or anywhere else



#8 GreenMachine

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Posted 09 April 2024 - 09:08

Interesting and timely.

 

I attended the Auto Italia event in beautiful downtown Queanbeyan on Sunday (city adjacent to the national capital, Canberra).  Some lovely exotica there as you might expect, also some great old stuff - a Fiat 2300 coupe caught my eye, and lo and behold, in the engine bay were two brake booster - one behind each headlight!  The owner had only recently acquired the car, and could not explain the operation, and with rain approaching I moved on with no better understanding of it.  Later I found an Alfa GTV 1750 (105 so 1970s?) also with two, the second mounted at 90* beside the first, set up for LHD but operated by a rod from the RHD pedal, as explained to me.

 

BTW, photos not showing for me.

 

ETA:  I recall seeing a (Vegantune? or was that the engine supplier?) rework of the Lotus Elan, with the Lotus/Vauxhall 2 litre IIRC, it had a brake booster/MC down by the driver side headlight, operated by a rod from the pedal.


Edited by GreenMachine, 09 April 2024 - 11:34.


#9 BRG

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Posted 09 April 2024 - 09:26

I just wonder if brake balance adjustment bars had filtered through to tip-tops and rally cars by 1987 when this Kadett was pictured.  On F1 etc, sure but I don't remember such things on rally cars back then?



#10 Lee Nicolle

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Posted 09 April 2024 - 12:12

I just wonder if brake balance adjustment bars had filtered through to tip-tops and rally cars by 1987 when this Kadett was pictured.  On F1 etc, sure but I don't remember such things on rally cars back then?

Balance bars were used on rally cars in the 70s, possibly even the late 60s. 

Circuit cars too were using them. I was using an adjustable rear brake bias by around 85. Knob to the left of the seat, And my budget then was next to zero.