75 V6 race-car brakes - Alfa Romeo Forum
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(Post Link) post #1 of 29 Old 23-04-16 Thread Starter
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75 V6 race-car brakes

We've done 3 races with the car, now - Mallory and Oulton last year, and Oulton a few weeks ago, but we still aren't happy with the brakes.

The guy we bought the car from had fitted a well-crafted alloy bracket on the front hubs and attached an extra pair of standard calipers - but kept the original master cylinder. Result was a long pedal, with little feel, and a tendency to be able to lock the front wheels too easily. We changed the master cylinder for a larger one (courtesy of a Ford Galaxy ! ) which improved the travel.......then we disconnected the servo, which reduced the tendency to lock the front, but the other weekend in the wet it was awful - brakes were vibrating like hell, had no feel and really didn't give any confidence.

We've been looking at it, and it seems as though the bracket can flex slightly, so we think any minor unevenness in the disc can be amplified by the flexing. Anyway we think we should replace the concoction with some proper 4-pot calipers - maybe Wilwoods.

Anyone any thoughts?

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Not sure re price but Alex Jupe has had an off the shelf 4 pot front brake conversion done for the 75/GTV6 setup developed. looks pretty snazzy.
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What calipers discs and pads are you running and do you have a budget restricting you?
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At the moment, standard discs, 2 x standard single pot Brembo calipers per wheel, and I think Ferodo comp pads.....we should maybe have gone for Yellow stuff.

There's always a budget....we're both pensioners, so the lower 3 figures it can be, the better......
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Not sure re price but Alex Jupe has had an off the shelf 4 pot front brake conversion done for the 75/GTV6 setup developed. looks pretty snazzy.
I'll have to have a natter with Alex, thanks. He keeps suggesting from time to time that I should sell him my GTV6, so I might use that as a lever.......
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There's not much Alex does in 3 figures, but ask him, racing with standard calipers wouldn't be the best, vibration has to be something with how they are fitted,
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My two bits worth: big-series Brembo radial calipers, modified 166 24v discs (310x28mm), custom caliper-mount brackets and wheel-stud rings. You are looking at ~1000 which is 780. I have this set on both my 75's (1.8T/3.2 24v) and its awesome in the track (with DS2500 pads). The least work is when fitting inside 16" wheels. I have 15" Compomotive MO wheels and had to reduce discs to ~307mm and grind outside caliper surface for sufficient clearance.
For bigger wheels, you can build the same set but using 315x28mm BMW M3 (E36) discs. They are L/R items and are actually significantly lighter than 166 discs.

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First thing to do is remove the second pair of calipers - not going to be helping in any way!

What sort of racing do you do? If you're on a budget and you're not doing lots of laps at a time the std system (in top nick) with a proper race pad compound might be absolutely fine.
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Originally Posted by jim K. View Post
My two bits worth: big-series Brembo radial calipers, modified 166 24v discs (310x28mm), custom caliper-mount brackets and wheel-stud rings. You are looking at ~1000€ which is 780. I have this set on both my 75's (1.8T/3.2 24v) and its awesome in the track (with DS2500 pads). The least work is when fitting inside 16" wheels. I have 15" Compomotive MO wheels and had to reduce discs to ~307mm and grind outside caliper surface for sufficient clearance.
For bigger wheels, you can build the same set but using 315x28mm BMW M3 (E36) discs. They are L/R items and are actually significantly lighter than 166 discs.

Jim K.
Thanks Jim - given us food for thought. My racing partner has just turned up armed with your book . We are running 15" wheels so the lightly modded 166 discs could well be an option. Do you sell the caliper-mount brackets? Do you use the wheel-stud rings because of wheel choice? You seem to have redrilled the 166 discs to suit standard PCD?

Sorry about all the questions
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Originally Posted by sprint_veloce View Post
First thing to do is remove the second pair of calipers - not going to be helping in any way!

What sort of racing do you do? If you're on a budget and you're not doing lots of laps at a time the std system (in top nick) with a proper race pad compound might be absolutely fine.

We are going to try removing them, certainly......we run in a club racing series (750MC Roadsports and/or Classic Sports Car Club's Future Classics) - both mini-enduro races of 40 - 45 minute duration with pit/stop for driver change. When we last raced, a few years ago we ran a Porsche 944 Turbo and I think that spoilt us - the brakes on that were very good
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Ah, 45min races might be pushing it on std discs. But with new fluid, and carefully selected pads, maybe ok? The 944 would have only had twin piston brembo brakes, very much the same as 75? Unless the turbo's got 4-pots?
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The stud rings are used to fix the studs solid. 5 of the 10 discs holes are elongated inward (best done on a lathe, the one shown is my hand-ground prototype) for the 5x98mm pcd. The disc central hole has to be enlarged to exactly fit on the hub -same as the stud ring ID. The ring is fixed on the disc with two short M6 bolts and the studs themselves are TIG-welded on the ring.
Yes, the caliper-mounts are available separately but I have specifically designed for the big Brembo jobs and 166 disc offset. The machine shop making them sells them for ~120/pair (95). I am thinking of talking to a CNC guy here for a small run if the price is right. Will probably know more next month.

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Ah, 45min races might be pushing it on std discs. But with new fluid, and carefully selected pads, maybe ok? The 944 would have only had twin piston brembo brakes, very much the same as 75? Unless the turbo's got 4-pots?
++Yeah the turbo has 4-pot Brembos - we've actually been looking at whether we could use these....
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The stud rings are used to fix the studs solid. 5 of the 10 discs holes are elongated inward (best done on a lathe, the one shown is my hand-ground prototype) for the 5x98mm pcd. The disc central hole has to be enlarged to exactly fit on the hub -same as the stud ring ID. The ring is fixed on the disc with two short M6 bolts and the studs themselves are TIG-welded on the ring.
Yes, the caliper-mounts are available separately but I have specifically designed for the big Brembo jobs and 166 disc offset. The machine shop making them sells them for ~120/pair (95). I am thinking of talking to a CNC guy here for a small run if the price is right. Will probably know more next month.

Jim K.
Thanks, Jim,

Be sure to let us know how those discussions go We may need to do something earlier, but I'd still be interested in this. Thanks again!

Richard
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Well after some consideration we've gone for some radial mount Wilwood 4-pots - they are on order now, getting a suitable mounting bracket made up when they arrive in a week or so's time. Pads will be Yellow Stuff.

Will report back when we've tried them.
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Curious, what size master cylinder are you using?

Good luck with the upgrade.

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A friend with a capri 2.8i tarmac rally car fitted Willwood 4 pots as well. They are good value and he's run them for 12 or 13 years now without issue. Until last weekend when he was turning in a carpark at 3mph and a front stub axle failed and the wheel fell off. It broke the willwood caliper off at the mounting lugs so a new one required. He was on the way to a 2 day rally and it doesn't bear thinking about the consequences of the stub axle failing at 100mph on a rally stage...

Shiny - the Willwoods are available in a range of piston sizes so you can match them to your existing m/c, no need to change.
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Curious, what size master cylinder are you using?

Good luck with the upgrade.

Thanks

To try to get a better (shorter throw) pedal we'd already upgraded the master cylinder to one off a Ford Galaxy / VW Sharan / Seat Alhambra (don't know if you get any of those in Oz - they're a 7-seater mini-van) Should be OK with the Willwoods, I think.
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75 race car? You kept that quiet.

The GTV6, is this the silver one I looked at?

*Must move out, must not buy another car*
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75 race car? You kept that quiet.

The GTV6, is this the silver one I looked at?

*Must move out, must not buy another car*
The race car was the one we got all the manuals etc off you for Used to be raced by Dave Messenger.......

Only ever had one GTV6 and its silver......can't remember if you've seen it
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I switched to CL brake pads for my 75 Turbo racer (on otherwise standard brake system), from Ferodo 2500

The change is extreme, has lead to the 4 pot 310mm system stil sitting on the shelf, and other suspension / geometry tweaks have been prioritized.

Try them before you uppgrade to 4 pot
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Quote:
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I switched to CL brake pads for my 75 Turbo racer (on otherwise standard brake system), from Ferodo 2500

The change is extreme, has lead to the 4 pot 310mm system stil sitting on the shelf, and other suspension / geometry tweaks have been prioritized.

Try them before you uppgrade to 4 pot
DS2500 are not a full race pad (with the exception of the rear of a FWD car).
For the front they are a fast-road/trackday pad. And very good for their intended purpose.
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The race car was the one we got all the manuals etc off you for Used to be raced by Dave Messenger.......

Only ever had one GTV6 and its silver......can't remember if you've seen it
DOH!!!

Yeah, it was silver. Still tempted, nowhere to put it!
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If you are suffering brake judder it may be caused by "imprinted" rather than warped disc or any other reason such as bracket flexing. Do a www search on imprinted brake discs and at the end of each session make sure you cool down properly and whatever you do don't rest your foot on the brakes with the car stopped when the brakes are really hot.

You may already know this!
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Thanks - we don't "think" this is the case, but its always a possibility.
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