Alfa 75 brake upgrade

[Colin Edwards]

Fitted Ferodo DS2500's to rear of the 75 last night.
 
Workshop manual specifies 0.25mm pad/rotor clearance.  Resulted in a non-functional handbrake when set to this dimension.  Kept reducing clearance in 0.05mm increments until handbrake restored to previous performance.  Resultant pad/rotor clearance now 0.15mm - is this normal?  What are we usually setting this clearance to?  I made NO adjustments to hand brake cable etc.

[shiny_car]

Indeed, workshop manual clearance in this instance is too great, if you want an operational handbrake (and brake pedal feel)!

You can generally do it 'by feel':
- safely raise the rear off the ground and have handbrake off, gearbox in neutral
- advance/tighten the outer pad(s) until they just drag against the disc when you rotate the wheel; then back-off slightly
- repeat for inner pad(s)

[Colin Edwards]

Hi Shiny_ Car,

Thanks for the advice.  The rear rotors had a bit of run out due to some earlier hard work.  I didn't want to run too little clearance so used the workshop manual dimension - big mistake initially! 

After yesterday at Broadford the rear rotors now have way more run out so its time to go ventilated given the temperature they were getting to.  I'll adjust clearances as per your advice when I fit the new rotors.

Thanks!

Colin

[Colin Edwards]

Has anyone calculated the front / rear braking percentages on a 75 3.0 running factory dimension calipers and rotors?  If so what were your results?

Colin.

[bazzbazz]

1/ Release Hand brake in the cabin
2/ Completely loosen off handbrake cable at the callipers so it is slack.
3/ Adjust inner pads as per Shiny's instructions - this sets the Callipers so that the foot brakes operate correctly
4/ Now tighten up handbrake cable at the callipers till you feel the pads just drag again, back off a poof-teenth.
5/ Hand brake should now operate properly & solidly.

Also when fitting the new rotors make sure the following

1/ All mating surfaces (hub/driveshaft/new rotors) are clean & free of corrosion ect
2/ Mounting bolts are torqued to the correct valued and done in a cross opposing sequence. DO NOT USE RATTLE GUN for rotors OR wheels - ALWAYS use TORQUE WRENCH !!!  (Can't stipulate this enough)

Rotors/Discs do not run out by themselves it is almost always due to failure to carry out either of the above. Even if you get them extremely hot, they will not "warp" unless one of the above is not carried out correctly.

Colin just thought I would add the above info as I am familiar with your mechanical background and also for the benefit for others reading this who may not be aware of such things. 

[Colin Edwards]

Hi bazbazz,

Thanks for the info.  I've re-adjusted the rears and hand and foot brake now just fine - thanks.

I have ordered a pair of Tarox vented / grooved / drilled rear rotors.  Possibly overkill for a car that will be rarely tracked however these cars are noted for the marginal braking.  Ventilation of in-board brakes on a sedan will be problematic.  I'm looking to optimize braking without resorting to going outboard.  Todays tyre technology seems to have exposed the braking of older cars.   

Performatek provide the attached doco with their rear caliper spacer kit.  This kit and the Tarox rotors (apparently a copy of the original Brembo rotors fitted to the SZ) essentially convert the 75 rear brakes (or any Alfa transaxle car) to SZ specification.  Given the DeDion will also be coming out for other work, I'll be involving professional assistance.

Colin
 

[Divano Veloce]

Ive had three Benditalia brake servos fail (diaphragm split) so decided to do something different. Anyone who has replaced a 75 Twinspark servo knows its not something you want to frequently repeat..and that's if you can find a replacement. A Mk3 Golf/Seat Cordoba/Audi servo will fit with some modification. These will work with the Alfa MC but I had a selection of  different diameter Audi MC's so I trialled a 23.8mm unit (factory Alfa MC is 22.2mm). The fluid reservoir from the Audi is for an angled MC so is not suitable when installed horizontally. A (Nissan?? PBR) reservoir fits perfectly but doesn't have a nipple for the clutch MC. A suitable reservoir was sourced from a Hyundai Elantra (manual obviously).
Brakes hacked - pedal feel is now great.

[Colin Edwards]

Well the ventilated, drilled and grooved rear rotors from Tarox have arrived.  Machined from solid billets, they are an exact replica of the Brembo rotors originally fitted to the SZ.  Arrived too late to test at Sandown so we'll give them a cooking at Winton or Broadford.  Application of AP Racing Thermo graphic paint should confirm a significant reduction in peak temperatures. 

[shiny_car]

Nice! 

[Colin Edwards]

Well the vented rotors are installed, bedded in and pad clearance re-set.  The attached image shows application of AP thermo paint prior to the Sunday drive to Warburton.