19 replies to this topic

[Aaron D]

Simple question really and I think I have the answer but it seems so simple I can believe i've overlooked something. The VX-Performance big brake upgrade is 299 Euros. This inclusing a couple of brackets to space out the caliper to take a 308mm disc, 308mm discs and longer bolts. Now, am I totally right in thinking that if i fitted two 10mm collars between the radial mount and the caliper, and bought 10mm longer bolts and fitted 308mm discs... that would simply be it??? I ask, as I simply refuse to pay that much when I can spend half as much on discs and engineer me some collars and pick up some bolts. Getting pretty urgent for a disc change so i'm going for it i think. Aaron

[Bargi]

Do you really need the bigger discs? General consensus is std discs are good even for very heavy track use, just make sure you got some good pads.

[JohnTurbo]

But having had a car with big old 4 pots the vx brakes do not inspire the same confidence. Interestingly the 2 Vxs that msv use for ards testing at Oulten are bog standard....except for big brakes.

[Arno]

Now, am I totally right in thinking that if i fitted two 10mm collars between the radial mount and the caliper, and bought 10mm longer bolts and fitted 308mm discs... that would simply be it???

Yes. As long as the 308mm disc has the same offset as the original 288mm so the disc is not moved inside the caliper side-to-side then that's all that would be needed.. Otherwise you'd need to offset the caliper as well.

And of course wheels that allow the caliper to move further out by 10mm would be nice to check first

Bye, Arno.

[The Batman]

Are you just thinking about running 308 discs and standard calipers? What will the actual benefit be? As the brake pad will still cover the same surface area. I suppose it might be better for cooling? But will this outweigh the extra weight (rotational mass etc etc)

[Aaron D]

Now, am I totally right in thinking that if i fitted two 10mm collars between the radial mount and the caliper, and bought 10mm longer bolts and fitted 308mm discs... that would simply be it???

Yes. As long as the 308mm disc has the same offset as the original 288mm so the disc is not moved inside the caliper side-to-side then that's all that would be needed.. Otherwise you'd need to offset the caliper as well.

And of course wheels that allow the caliper to move further out by 10mm would be nice to check first

Bye, Arno.

Thanks

Are you just thinking about running 308 discs and standard calipers?

What will the actual benefit be? As the brake pad will still cover the same surface area.

I suppose it might be better for cooling? But will this outweigh the extra weight (rotational mass etc etc)

Yes. I ran standard calipers with larger discs and control pad on and old car and braking was improved. Cosmetically I want a better look and i'm sure braking will improve because the rotational mass will be slowed down easier on the slower, outter edge on the larger disc.

[The Batman]

Fair enough your car I have 308s on my car and it does look nicer Although with standard calipers I imagine after a month or 2 you will have 2" gap all the way round that will rust up

[Seb.F]

Are you just thinking about running 308 discs and standard calipers?

What will the actual benefit be? As the brake pad will still cover the same surface area.

I suppose it might be better for cooling? But will this outweigh the extra weight (rotational mass etc etc)

With the pad further from the centre of the wheel, less braking power will be needed to apply the same force to the wheels.

Imagine one of those kids roundabouts, your one hand trying to stop it from the centre is quite hard, but the same force applied right on the edge will slow it down much quicker

[The Batman]

Ah didn't think of it like that! Although I now remember slindborg trying 308 discs and said he didn't notice anything

[slindborg]

Pad area = wear rate (eg you could have a pad the area of a pin head at the same point of load as the current pads, which would give the same braking force but for all of a few milliseconds ) Pad centre of pressure from the centre of the disc = fulrum Pressure and friction material = stopping With OEM calipers and GM 308mm discs you need something in the realms of an 11-13mm spacer due to the arc of the 308mm disc being too great than the 288mm specced caliper. Trust me I know this as I fitted 10mm spacers and had the disc jammed against the caliper IMHO there was fcuk all 'gain' bar adding about 50Kg to the front of the car with the 308's

[vocky]

a pair of OEM 308mm disc's weigh about 0.5Kg more than the OEM 288 disc's, I weighed them before fitting

[slindborg]

Felt a lot more

[vocky]

worn discs weigh less than new discs I replaced almost new 288's with new 308's

[Aaron D]

Thanks chaps i'll be pricing it up and machining some spacers this afternoon with any luck.

[slindborg]

Thanks chaps i'll be pricing it up and machining some spacers this afternoon with any luck.

dont forget that 10mm isnt enough

[Mike (Cliffie)]

Thanks chaps i'll be pricing it up and machining some spacers this afternoon with any luck.

Can you machine me a set as well please?

[Aaron D]

I'll make up my first set with what i've got; don't think ill have enough metal left but all being well if it comes out ok ill see what i can do.

[synergy]

Thanks chaps i'll be pricing it up and machining some spacers this afternoon with any luck.

Finally what is the exact spacer to fit 308 zimmermann astra discs on stock 2pot??
10? 11? 12? 13 mm?

[vocky]

I believe it's 11mm

[siztenboots]

iirc but there is still the problem of the caliper fouling due to the arc profile