ALFAGTV6.COM

Jim K · Post by **Jim K** » Sun Feb 20, 2005 10:45 pm

The SZ rear vented disks are not out of production (maybe AR thinks they are!), Brembo still make and sell them, I got a pair last year for ~130Euros. Call Brembo in France, they should be able to supply your discs.
Jim K.

tectoteam · Post by **tectoteam** » Mon Feb 21, 2005 11:48 am

thank you jim.

got it at brembo site.
ref :09.4536.10
250*20

i get a call tomarrow at a local brembo dealer.

Post by **Michael** » Tue Feb 22, 2005 11:33 am

This is good to know...

I was trying to figure out which way round the 951 calipers should go - the calipers have differently sized pistons, 36mm and 38mm. It was not clear which one was at the 'leading edge'.
This from:
http://www.buybrakes.com/brembo/faq.html#q12

Are Brembo calipers directional?
Brembo's calipers are directional, due to the use of differential piston sizes. The leading pistons are smaller in diameter in order to combat uneven wear of the brake pads. Upon close examination of the caliper, you will find a small arrow cast in place which denotes the direction of disc rotation. Additionally, when mounted on the vehicle, the bleed screw(s) must be at the top of the caliper

tectoteam · Post by **tectoteam** » Tue Feb 22, 2005 11:43 am

exact.....

you need the cross over tube down and the small piston to the top of caliper, because mounted at the front of rotor
this is the small piston that 'gets' first the disc when clamping.

also i get prices for rear vented rotors, and bendix ones are the less than the half on brembo !

i will get bendix ones. and a spacer kit from perfomatek.

Post by **Michael** » Tue Feb 22, 2005 1:59 pm

Yes - it became an issue on my install since the calipers are on the leading end of the disk on the GTV6, and the trailing end in the Porsche. It seems it will not matter as long as I make sure that the arrow (which I did find) conforms to the direction of rotation and the balance pipe is installed on the bottom of the calipers.

Can you post a pic of the Bendix calipers? Just curious

Cheers,

tectoteam · Post by **tectoteam** » Wed Feb 23, 2005 10:17 am

Michael wrote:Yes - it became an issue on my install since the calipers are on the leading end of the disk on the GTV6, and the trailing end in the Porsche. It seems it will not matter as long as I make sure that the arrow (which I did find) conforms to the direction of rotation and the balance pipe is installed on the bottom of the calipers.

Can you post a pic of the Bendix calipers? Just curious

Cheers,

mistake.

i'm wasn't speaking from bendix calipers.....but bendix rotors instead of brembo rotors......about the option to change the rear rotors of a gtv6 by the ones of a alfa SZ/RZ one's are vented.

MD · Post by MD » Fri Feb 25, 2005 1:53 am

Hey, I'm not on the site for a few days and you have Porche Brakes !!

Can't wait to see your test report on the whole set up Michael.

I am assuming the 4 pot calipers will take a larger volume of fluid to move the same distance in compressing the rotor than the original Brembos. This may or may not be an issue for the master cylinder / brake pedal length of travel. I suppose you will find out soon enough. Congrats for takling the brake frontier!

I am staying glued..

MD

MD · Post by MD » Sat Feb 26, 2005 1:22 pm

Michael

I am not very familiar with Porche model numbers. The topic heading refers to a 944 but your threads refer to a 951. Is this a typo error ? If not, could you please a elaborate. Thanks.

MD

joey · Post by **joey** » Sat Feb 26, 2005 6:04 pm

yep, its a porsche thing...

951 is the factory model designation for the 944 turbo.. Mike is making the difference clear from the n.a. cooking model since the turbo scored the brembo 4 pots that mike is using as an upgrade over the 'regular' 944.

cheers

joe

ps: its also important to note the year. Mike says his are 87, which distinguishes them from the bigger 944 Turbo S (88-89) brembos. (the S varient was basically a handling upgrade). At that point the 944 Turbo was brought up to S specs and then came the s2 redesign for 1990. (or something like that)

MD · Post by MD » Tue Mar 01, 2005 2:52 am

Hi Joey,

Appreciate the Porche edumecation!
I think I almost have my head around what you said as well!

Thanks mate.

MD

Post by **Michael** » Wed Mar 02, 2005 1:36 am

Thanks for clearing that up Joe - exactly right. The project is progressing okay. I'm hunting down some brake hoses right now as I'm not too happy with how the stock Alfa ones fit with the Porsche calipers.
I think it will be best just to buy a set of 951 (;)) stainless steel brake lines.

Cheers,

Edit 03/13/2005
For the record, I was able to use my Alfa flex hoses (Earl's Stainless steel hoses) and bent some new 3/16" brake pipe with metric fittings to join from the caliper inlet to the flex hose using the stock GTV6 mounting bracket.

Post by **Michael** » Sun Mar 13, 2005 11:45 pm

Teething problems.

1st test drive ... all OK until I step on the brakes hard and hear horrible grinding noises. The sound diminishes as I drive on so was pretty puzzled. I think what is happening is that the disks are expanding (increasing in diameter) as they heat up and at that point, the clearance between the disk and the caliper is insufficient -so the disk is actually grinding on the caliper. No more contact when they cool and contract. Anyone know if there is a rule of thumb as far as the cold clearance between the outer circumference of the disk and the inner circumference of the caliper? It seems to be 4 or 5 mm on my 944 Turbo - 1 mm on the Alfa

I can’t see a way to increase the clearance without having new mounting brackets (adapters) made since I had to enlarge the mounting holes a tiny bit during installation just to get the caliper to clear the disk…

Some pics to illustrate...

Top pic is on the Porsche, lower pic is on the Alfa.

Cheers,

Post by **Zamani** » Mon Mar 14, 2005 12:16 am

Mike,

Maybe you could try machining the rotor diameter down by 2-3mm if the clearence is actually the problem. That would be much easier than new brackets.

Maurizio · Post by **Maurizio** » Mon Mar 14, 2005 12:40 am

some quick math with some estimated numbers!

Rotor dia = 310*mm
Temp = 400 * K (increase during breaking)
a = 12*10^-6*K^-1 (for simple steel)

Dia increase would be 310*400*12*10^-6 = 1.5 mm !

Post by **Michael** » Mon Mar 14, 2005 12:52 am

Thanks for the formula - I checked the Porsche and found it about 3 mm - almost nothing on the Alfa...

Zamani - have you ever had disks machined down like this? Will a normal machine shop be able to take on this job?

Its a good idea

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