Rear brake rotors & pads?

[prova]

Hi guys just trying to buy some rear brake rotors and pads locally in Geelong. My car is a 1985 GTV4. They do not have a listing on the rotors for my model or the GTV6. They have a listing for Alfettas up to 1983 - OD 250mm with 10mm studs - would these fit my model? Also would pads listed for the GTV6 fit my car?

Any help greatly appreciated as I am keen to sort the rear brakes as soon as possible. My mechanic told me they are knackered which is understandable but what gets me is that they passed a Roadworthy in December last year! Plus both my mufflers needed replacing last month as well with big holes. I should of checked the car out better myself or had an independent mechanic check it over.

I think the inspector could not give a rats!

Thanks guys.

[prova]

Thanks Glen for taking so much time and effort to answer my question. I have ordered a pair of rotors that are 250mm OD and have 10mm stud holes. I hope these are the right ones - they seem to be but the listings are a bit vague (tried two different suppliers. I think I should be alright with the pads. $75 each rotor and price on the pads unsure as they will see what they can get. Does the price sound okay?

Hopefully will be fitted tomorrow or Wednesday.

[prova]

Hi guys. My mechanic took the old pads and rotors off and hey presto everything I bought was wrong. The right ones are coming tomorrow. I have taken the long way round!

[Jekyll and Hyde]

Hi All


Choderboy I didn't know about the 2mm difference in thickness, you learn something new everyday on this forum and i wont to know more thanks for the input
but I cant see any issues as CV joints have 8-10 mm of float so with two CV's  either end of the driveshaft thats almost 20mm freeplay
have had 4cyl discs drilled [8mm holes to 10mm] on my six for 3yrs now with no shaft problems or difference in braking performance
I removed the disc to driveshaft spacers and added alfa 75 shafts they are 50mm longer

Glen

CV joints aren't the issue.  Its the little locating steps which sit inside the disk.  One on the output flange from the gearbox, one on the adaptor between disk and CV.  If you put a 10mm disk between those components which were designed for 12mm ones, the locating step on each part will usually contact each other before the disc is clamped.  Which gives you floating rear discs, which will slowly chew away the bolts, and suddenly you have a driveshaft flailing around driven at whatever speed the wheel is doing....  Assuming of course you don't do the bolts up tight enough to break the casting on the adaptor or output flange.

Are you saying that in your car you've thrown out the adaptors between the disc and driveshaft, and you've just bolted the 75 driveshaft straight to the output flange of the gearbox (through the disc), like some of the 4 cylinders are?  Because if thats what you've done, its no wonder you haven't got any issues with the 10mm disc floating.  75 3.0 and also 90's should still have an adaptor, its just much shorter.  Anyone who tries this trick with most of the transaxle V6s is pretty unlikely to suceed if they have standard driveshaft setups.

There are at least 3 different rear discs for the transaxle cars, and it may actually be more, but I'd have to recheck that.  There is two with 10mm holes, one of which is 10mm thick at the flange where the bolts go through (for 4 cylinders with adaptor), and the other 12mm thick (should cover all v6s from memory - GTV6, 75, 90, although not 100% on 75 2.5).  Don't think the area the pads sweep is any thicker though, and usually catalogues won't actually tell you the thickness in the flange area    There is also one with the 8mm holes (4 cylinder without adaptors, which should include 75TS.  Incidentally, the bolts should be a 6mm allen key, not 5).  I also have a vague recollection that for some reason one or more models of Giulietta is different to all of the above - possibly the offset of the mounting flange, or maybe overall diameter....

[prova]

Now I am even more worried! I hope the rotors I pick up today are the right ones - they are coming down from Sydney. I think they may be as there seemed to be only two choices in the listings catalogue. I will let you know the codes if they are right. The cars been up on stands now for two days and I just want to drive it.

[Jekyll and Hyde]

jekyll and hyde

it didnt even occour to me when i did the driveshaft change that there was a difference in the flange area it all went together easily with no sideways float.
just lucky i guess as i said its been like that for 3yrs now with no issues hill climbes and track days included
just measured the flanges of two spare disks 12.5mm these have a champher on the spacer side and 10mm bolt holes they are v6 disks
and of course you cant just throw away the driveshaft spacers and use v6 shafts there 60mm to short

lucky Glen

Only if you use GTV6 shafts, 75/90 V6 would only be about 25mm too short, although they'd probably still reach due to CV movement.  Couldn't be bothered unbolting mine to see....

I did track down a 4 cylinder disk in my stash today, as I realised that I had never actually measured the flange thickness of one with 8mm holes.  Turns out for some stupid reason, they seem to also be 12(.5 )mm thick in this area, which explains how you've gotten away with it.  Only some very bright engineer at Alfa can explain why the hell they made the 4 cylinder 10mm holed disks thinner than all the others   

Random guess suggests that perhaps when the GTV6 came out overseas, they beefed up the flange thickness, and then modified the 4 cylinder driveshaft system to suit, allowing them to use the same disk casting for both 4 and 6, just with different machining operations...  But I'm sure now I've said that, someone with a mid 80's GTV4 is going to jump in and say their car has the adaptors still (which would fit nicely with the random behavior exhibited by a certain factory in Italy!)  However, my 81 4 cylinder didn't have them, and 75TS don't have them from memory...

[prova]

Finally picked my car up today - now so much better! As it turned out one of the caliper pistons had seized so it was sent off to be rebuilt at a cost of $185 bananas - ouch! The rear Brembo rotors where $160 for the pair and the english made pads $75 - pretty reasonable prices I think. Labour $160 - cheap! Good mate (mechanic) who is now working from home did a great job on the car.

Now on to the next job - head gasket. I think I am getting on top of things now.