Brakes

BradGTV · May 04, 2009, 05:34:51 PM

what is a good brake mod. on my 1985 GTV

is it to use gtv6 callipers or something else??

keeping in mind i dont want to change to five stud.

thanks brad..

Sheldon McIntosh · May 04, 2009, 05:48:43 PM

What do you want to do with the car? Medium road, fast road, track? What is the limiting factor with your current brakes?

BradGTV · May 04, 2009, 05:56:38 PM

fast road.

umm really just for better performance.
to stop quicker and better

thanks brad

Storm_X · May 04, 2009, 07:05:19 PM

i was thinking about slotted rotors allround on my giulietta with alfa 75 Calipers but still are single pot.

i have seen volvo 4 pot Calipers been modified to fit the alfas but alot of work involved.

Simon Aarons · May 04, 2009, 07:20:52 PM

A 75 (t-spark or v6) has the same brakes as a gtv6 - two pot brembo's. 4 Cylinders also have twin pistons but i believe they are slightly smaller and only come with solid discs - not ventilated like the v6's.

We have a 4 cyl at home with the upgraded v6 brakes and they are great on the race track compared to the standard ones...but on the road there isn't really a difference. Stopping quicker will probably come down to driver skill... as if you have brakes the bite very hard you are most likely to lock the wheels if you suddenly jump on the brakes.

Sheldon McIntosh · May 04, 2009, 07:34:27 PM

The Volvo calipers fit straight onto a 75/90/GTV6. Is the GTV4 different?

Slotted rotors will make two tenths of f all difference on the road. It will wear your ~~pads~~ wallet out quicker though.

Storm_X · May 04, 2009, 08:50:03 PM

i know the 4cyl /4stud are solid disc`s. i thought the 75 brembro`s where still single pot? i must have been wrong.

Sheldon McIntosh · May 04, 2009, 08:58:22 PM

I'm confused. 75/90/GTV6 is Brembo two pot. Volvo is four-pot. What does GTV4 have? What does Guilietta have?

jimnielsen · May 04, 2009, 09:48:44 PM

Giulietta's & 4 cyl GTV's have ATE single piston (one each side) cast iron calipers as standard. They are non ventilated type disks. Many people retro fit the GTV6 (style) aluminum four piston calipers to the giulietta and GTV 4's along with its ventilated disk as an 'initial brake upgrade, its easy as it fits on the hub and the 'offset' is no problem. The GTV6 caliper is lighter, but MUCH more flexible, however it does provide significantly better stopping, especially on the track where repeated stopping can be 'useful'. Its basically a 'bolt-on' upgrade hence its popularity..

jimn~

Sheldon McIntosh · May 04, 2009, 09:55:00 PM

Jim, I think you'll find the GTV6 'style' calipers are two piston.

jimnielsen · May 04, 2009, 10:02:52 PM

yes.. two per side...

Robert. Dale · May 04, 2009, 10:57:05 PM

Jim, I gather you have not seen a pair of Brembo GTV6 or 75 Front Calipers.

They are Alloy 2 Spot (one piston per side) as Sheldon said.

They are an improvement on the 4 Cyl brakes because of larger Pad area and the Ventilated Rotors.

They are not that good for serious Track use as they flex causing the Pads to taper and therefore losing braking efficientcy and feel.

Thats why my 75 now has 4 Spot (cast iron) Volvo Calipers which give far greater feel and better pad wear due to their stiffness and far greater pad area.

The only draw back is the weight.

If anyone wants a decent front brake setup for a GTV/GTV6/75 call Bruno at Marranello Pursang.

Rob D

Sheldon McIntosh · May 04, 2009, 11:09:46 PM

+1

I have the same set-up on the front and it is almost too much for my standard sprung 90, it just about face-plants itself. Nice to have the confidence going into turn one at Sandown or Phillip Island though. Nice to not have to worry about fade either.

Thanks Rob, I thought I was going crazy for a minute there. I was thinking, 'hang on, maybe they are 4 spot, it's been a while since I saw them....)

A friend came round today in his racing Sud. I went out for a fang in it around the block and had a great time, apart from the brakes. He then went out in my car, and said 'Gee your car is shit, but ohmigod those brakes are almost too good!" That is actually a true story.

jimnielsen · May 05, 2009, 07:16:55 AM

rob/sheldon, you are right, of course. It was late, I was wearing sunglasses etc.

Tristan Atkins · May 05, 2009, 02:07:03 PM

Hey Brad,

The choice depends on what you are after.

If you're after repeatability, upgrading to a ventilated rotor you should be able to stop more often without encountering brake fade. The rotor acts as a heat sink to dissipate all the heat generated from braking and a ventilated rotor has better performance.

For stopping distance, the pad is what determines the vehicles performance. With the original pads I could just lock the brakes up under heavy foot pressure. I since swapped the pads over for 'RB74's' on the front and 'Comp 2's' on the rear. This halved the braking distance at Winton and the car could lock all 4 wheels.

Thus if your just after better baking performance I'd try a set of pads. I got mine from "Race Brakes" and I've been happy with them. A number of the more serious guys use different types for different applications. Ask around and someone will suggest something that suits what you are after.

If you want to keep the 4 stud hubs and upgrade the callipers to GTV6/Alfa 75 for street performance, get a 5 stud rotor machined to 4 stud. John at "Alloy Race Components" are able to do this. I would also swap over the upright as the brake mounts on my 82 GTV's uprights were significantly less gusseted than on the 75's uprights.

If you want serious performance then you're looking at serious cash for larger brakes, rotors, bias bars, bias valves, pedal boxes etc.

This said I would also check/change the fluid as well as check that each brake is working evenly and the brake bias proportioning valve is working correctly. To do this I used a technique that Carrol Smith recommends in "Drive to Win" and it works well on our project car at uni. Place the car on 4 jack stands and get someone to sit in the driver's seat. Straddle the front wheel (a bit trickier on a sedan) and turn it while the driver slowing increased the brake pressure. When you can no longer turn the wheel get the driver to hold that pressure and check the other side, the resistance should be the same. Then check the rear wheels. You should be just able to turn them (this checks the bias.) Then again increase pressure until you can't turn the rear wheel and check the other side. Although this method isn't perfect it should tell you if something is wrong and it gets the bias to within a turn on the bar every time.

That also said technique also plays a big part when you don't have a computer to figure everything out for you so get a copy of "Drive to Win" and have a read on stabbing then squeezing the brakes.

Tristan