Group-1 homolgation

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AdeyB · #1 Post by **AdeyB** » Thu Dec 08, 2005 1:33 pm

Hi All, 
 
Just sorting the sprint for the next season and wondered if any knew if the Sprintparts brakes conversion would fall into "Group-1". I hope it does! The discs are the same diameter and the calipers are still single piston. Only real difference is the thickness due to venting. No drilling or slot/ grooves. 
 
your thoughts please! 
Adey

davepoth · #2 Post by **davepoth** » Thu Dec 08, 2005 5:49 pm

Best thing to do would be to ask the sprintparts guys, I reckon they would know more than anyone. 
 
The Group 1 Homogolation document, 
 
<a href="http://www.sprintparts.triumphowners.co ... cforgp.pdf" target="top">www.sprintparts.triumphowners.com/uploa ...  
 
Does mention specifically that vented discs are allowed, as is a change of pad material, on page 1.

AdeyB · #3 Post by **AdeyB** » Thu Dec 08, 2005 6:04 pm

I read the document and it does indeed say vented discs. 
 
However the FIA papers do not specify.They do allow twin circiut (and show a picture of the AP calipers) under group-1 but there's no close up to check if it's a vented kit. 
 
Under group 2 there's a 4 pot kit with vented discs etc etc I'll check with Sprintparts and maybe try the "saftey" argument with the scrutineer before I fit them! 
 
ta 
Adey

Carsreunited · #4 Post by **Carsreunited** » Fri Dec 09, 2005 12:33 am

What series are you sorting it for?

AdeyB · #5 Post by **AdeyB** » Fri Dec 09, 2005 11:02 am

Hi 
prepping it for the HRCR road rally series, classed as "classic" ie pre 1981, post 1975. 
 
group-1 homologation only rules apply. (plus only 2 chokes per 4 cylinders - no webers boo...) 
 
cheers 
adey

AdeyB · #6 Post by **AdeyB** » Sun Dec 11, 2005 1:02 pm

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Dolly racer 33 · #7 Post by **Dolly racer 33** » Sun Jan 01, 2006 10:39 pm

The original Group 1 set up consisted of vented discs, the same diameter as the original, the original calipers, spaced to accept the vented disc longer stub axles to allow for the extra thickness of the disc. I used to have an original set of these but stupidly I disposed of them otherwise I could make copies. If the regulations state homologated components then that is what they will insist on. Parts that are similiar but 'safer' will not be permitted. Make some, if you cannot, call me I can.

Edited by: <A HREF=http://p206.ezboard.com/bthetriumphdolo ... er33>Dolly racer 33</A> at: 1/1/06 10:49 pm

bodgerben · #8 Post by **bodgerben** » Mon Jan 02, 2006 3:07 pm

<a href="http://www.bodgerben.com/images/ST-Brake-Disk-2.jpg" target="top">Special Tuning Brakes</a> 
 

Ben 
 
<a href="http://www.dollysprint.com">www.dollysprint.com</a>

tinweevil · #9 Post by **tinweevil** » Mon Jan 02, 2006 7:25 pm

The spacer isn't rocket science. Does anyone have a genuine ST disk and stub that could be measured for posterity? (I've been told that the stag stub is the dolly ST stub, any truth in this?) 
 
Tinweevil

1978 <a href="http://www.triumphowners.com/704">Dolomite Sprint</a> 
1972 <a href="http://www.triumphowners.com/754">Spitfire IV</a> 
1968 <a href="http://www.triumphowners.com/705">GT6 II</a> 
1973 <a href="http://www.triumphowners.com/755">Dolomite Sprint</a> 
39 anorak points on the Nicholas scale

Dolly racer 33 · #10 Post by **Dolly racer 33** » Mon Jan 02, 2006 10:09 pm

The caliper spacer is the easy part. the hard part is the stub axle, as well as being longer they also have a larger diameter thread on the outer end, cannot remember whether this is 9/16 or 5/8 unf, I can check. I have these stub axles on my racer, or rather new ones made to the original spec. Because the stub axle is longer & you use the original hub & wheel bearings obviously the whole hub assembly is moved further out & a spacer is necessary against the upright to take up the excess movement, thus the 'Group 1' spec cars have a front track around 1" wider than standard. 
 
I believe a GT6 stub axle is longer, however, the diamater of the outer retaining nut is of the smaller diameter 1/2 unf. Because of the increased lenghth of the stub axle the increased load on this nut requires the larger diameter.

Edited by: <A HREF=http://p206.ezboard.com/bthetriumphdolo ... er33>Dolly racer 33</A> at: 2/1/06 10:12 pm

Mark Larmour · #11 Post by **Mark Larmour** » Tue Jan 03, 2006 5:46 am

As stated above, the caliper spacer is the easy bit. The stub axle is longer, a spacer goes on the stub to make up the extra length as well as the vertical link is also modified. 
 
We have a set of brand new ST vertical links, stub axles and spacers in stock but they are NOT for sale, as we intend to keep them for reference purposes. 
 
We have been down this road before, and seriously looked at remanufacturing the original ST Vented Disc kit, but felt that the demand would not justify the work and that the cost of manufacturing and modifying all of the components was going to make the cost beyond what most people were prepared to spend. Material cost is not that high but it is a very labour intensive job with many hours of machining. This time and cost can be considerably reduced using CNC machining, but not many people are interested in setting up to make 5 sets of parts. 
 
I have had a set of ST discs on my road Sprint for over 20 years, which are ideal for road applications and competiton work, but most serious racer these days make or have made up big diamaterdiscs with big calipers because they are not using the original Sprint wheel which is where the limitation in size comes in. 
 
Our own Vented disc kit does only use a single piston caliper which gives a 40% larger pad size and still allows use of the standard Sprint wheel. 
 
Reports from people that have been using these kits in both road and motorsport applications is very positive. We have a customer in Denmark who just ordered a set for his Rally Sprint, so that will certainly be a good test.

<a href="http://www.sprintparts.triumphowners.com">SPRINTPARTS</a>

tinweevil · #12 Post by **tinweevil** » Tue Jan 03, 2006 10:43 am

Ah, a bit more complex than first thought. So a kit comprises: 
 
2 off stub axle. 
2 off hub nut. 
2 off hub nut washer. 
2 off upright. 
2 off stub axle spacer. 
2 off caliper spacer. 
2 off brake disk. 
 
Is that all of it? 
 
For low volume manufacture try <a href="http://www.emachineshop.com/">EMachineS ... . You need to download their software and draw what you want made. The software will then give you a finished, delivered price in whatever quantity you specify. 
 
Tinweevil

1978 <a href="http://www.triumphowners.com/704">Dolomite Sprint</a> 
1972 <a href="http://www.triumphowners.com/754">Spitfire IV</a> 
1968 <a href="http://www.triumphowners.com/705">GT6 II</a> 
1973 <a href="http://www.triumphowners.com/755">Dolomite Sprint</a> 
39 anorak points on the Nicholas scale

Mark Larmour · #13 Post by **Mark Larmour** » Tue Jan 03, 2006 11:10 am

Your list is fairly close except you need 4 caliper spacers, 2 off per caliper. There are 2 types of spacers for each caliper, 1 blank and the other needs to have a hole and recess for the caliper bridge seal (to stop the caliper and spacer from leaking). 
 
If you can't source the correct disc rotor you also need to modify an existing disc and more than likely make a "top tap" adaptor spacer to fit between hub and rotor. 
 

<a href="http://www.sprintparts.triumphowners.com">SPRINTPARTS</a>

bodgerben · #14 Post by **bodgerben** » Tue Jan 03, 2006 1:26 pm

As you can see - I use a copy of the original ST setup on my Sprint - and personally I think they are fantastic, much better than the standard brakes. But - they were bloody expensive compared to AP, Sierra conversion, Willwood etc. But they are homologated (if I ever turn the car into a racer). 
 
You can already get all these bits, if you are prepared to spend the money. 
 

Ben 
 
<a href="http://www.dollysprint.com">www.dollysprint.com</a>

Carsreunited · #15 Post by **Carsreunited** » Tue Jan 03, 2006 5:29 pm

Depends what series you race in Ben. You will find that most have brakes as 'free' in the technical regs but with a need to retain drums. 
 
Mine's had the stub axle modification. Jigsaw have obviously got the specs and can get them made on an individual basis. 
 
Scott

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Group-1 homolgation

Group-1 homolgation

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