75 front brake calipers

[Colin Edwards]

Looking to reduce unsprung weight.
Are the standard / factory 75 V6 calipers aluminium or steel? 
Can someone provide the caliper assembly bolt (4 x off SHCS) and caliper fixing bolt (2 x off hex head) dimensions.   Need dia, thread pitch, thread length, shank length etc.  Haven't had to (yet!) remove calipers yet so not sure of hardware specs and caliper construction.  A few vendors like EB spare have alloy (lightweight?) calipers.

Very grateful for any advice .

Colin

[Craig_m67]

They’re alloy, not steel

Can’t help you with the other info as they’re packed away in a mates shed

[Colin Edwards]

Hi Craig.  Thanks for confirming material.  I would have been surprised if it was steel

The 4 caliper SHCS are probably M8 and the 2 fixing bolts probably M12, however given the price titanium I need to be certain of the dimensions.

Regards,
Colin

[GTVeloce]

They're light! Possibly not quite big enough depending on your usage/vehicle (and a contentious issue I know) but they are certainly not heavy compared to almost everything else.

If you want to reduce unsparing weight look at your wheels. I have three different sets of wheels and none are particularly heavy but the original 14x5.5 wheels are soooo light. Not the ideal dimension but you get the idea. Otherwise it gets expensive for little gain (titanium bolts etc). The rest of the front suspension is also light with the exception of the lower control arm so you could source an aluminium replacement and same with the hub (I have seen aluminium hubs for sale).

[Colin Edwards]

Hi GTVeloce,

Car is for road use only.  No issue with the brakes given ventilated rear rotors and DS2500's all round.   
Car still has its Simmons V5's fitted by the first owner back in 1988!
After a couple of the rim bolts failed I replaced all including nuts with titanium.  Reducing each wheel by near 600g.  Also reduced the bank balance!!
Titanium wheel nuts will be the next project however I need the caliper bolt dimensions so all can be incorporated into the one order.
Aluminium lower control arm and hub possibly not street legal?

Colin

[GTVeloce]

You are welcome to come over and take one of mine off to measure if that helps? I'm not far from you and have two cars with this brake setup.

[Colin Edwards]

Hi GTVeloce,
Thanks a million!  I'll give you a call to arrange.

Colin

[Dcal]

Hi Colin, I've a few calipers apart ready for recoating but haven't decided what to coat them with yet.

The bolts are M10 x 70mm 1.5 pitch with 34mm of thread, however the threads only engage 11 or 12mm. I think they are grade 8.8
The mounting bolts are M12 x 36 x 1,5 pitch with 22mm of thread. They are grade 8.8.
For reference the complete calipers are a few grams over 2kgs including spacers, pistons, seals and connecting bolts.

[Colin Edwards]

Thanks very much for the bolt dimensions.
No problem sourcing the M10 however the M12 is going to be a problem.  Titanium M12 seems to be only commercially available with 1.25 pitch.
Most weight will be saved by changing the M10's so will run with that.

Regards,
Colin.

[Colin Edwards]

Replaced the M10 Caliper screws and the M8 knuckle riser nuts & bolts with 1100MPa titanium.  These substitutions plus others to the caster links, damper mounts and roll bar drop links amount to a better than 250g reduction in unsprung weight to each front corner.  Not much...…………..but it cant hurt!

[shiny_car]

Nice! 250g is actually quite a bit, given the hardware you're changing.

[Colin Edwards]

Thanks.  Next will be titanium wheel nuts.  Probably a 50g saving per corner at best.  Although as the wheel nuts are near the outer edge of the wheel movement arc, their impact is significant.  Then diminishing returns really kick in!