Rotor Size

[VSEXEC]

Hi guys,

Im doing a brake conversion at the moment using the 4 piston fronts off an R32. I just want to know what the biggest rotor diameter you can use is. I was thinking of using a 324mm x 32mm rotor. Thanks

Edited January 21, 2012 by VSEXEC

[GTSBoy]

Those calipers originally come off a 280mm disc. Without using any adapters they will only suit a 280mm disc. If you use them on a 324mm disc they will need to be spaced outward (radially) using adapters. Note also, that a given caliper and pad really only suits a certain disc size (or at least a narrow range of disc sizes). The shape of the caliper's curve follows the outer cicumference of the rotor. If it is curved to suit a small disc, then it will tend toward hanging off the edge of a larger disc near the middle of the pad. I think that there are adapters to suit the R32 caliper onto 324mm disc, but I don't know what the resulting sweep of the pad over the disc looks like.

[VSEXEC]

Thanks for the info, I bought this conversion a few years back it came with adaptors to bolt to the front hub and it was meant to fit a 330mm x 32mm but the caliper had to be shaved abit, now im just trying to work it out for the rear end.

[Legionnaire]

I've seen sumitomo calipers sitting over variety of rotor sizes using spacers. The most common conversion is 280->324 rotor for obvious reasons, but there are more options out there. Whether they're worth doing is debatable, but since you asked about different options and the biggest possible rotor, here goes:

- There are adapters for 330x32mm rotors, front rotors off V36 skyline/skyline crossover are probably the cheapest option in that size, but you can use two-piece rotors with 332x32 brembo or stoptech friction rings with custom hats.

- Then there are adapters intended for 334x30mm rotors off a lexus GS. Rotor requires slight modifications.

- Adapters for 340mm rotors I saw once were a one-off item, so worth mentioning only because it can be done.

- UAS had an adapter kit to use with 343mm two-piece rotors, but it's apparently no longer available

- There are kits that use 345x32mm rotor off a Merc ML55 AMG, see attached pic. Silvias had 280x30 front brakes from factory, just like the ones you bought, but with steel calipers, so the pic is relevant. Rotors are cheap but have to be modified.

- The biggest kit I've ever seen was R34 Gtt caliper (310x30mm factory size, pad shape same as yours) sitting over V36 skyline sport 355x32mm rotor, see second and third attached pics

For rears there are spacers for GTR34 322 rotors, V36 330mm and 350mm rotors

Edited January 21, 2012 by Legionnaire

[VSEXEC]

Thanks for that very helpful

[Idaten]

Wow.

How the hell do I sit my GT-t on V36 rotors?

O.o

[GTSBoy]

With caliper adaptors.

[Legionnaire]

You would't want to - they weight a tonne each (I think it's mass is close to 14kg, but can measure when I have time), offest is wrong for most wheel designs, and they require 18" wheels. Also you can use smaller rotors and get just as good braking as with these - cooling and pads with higher friction are your friends. There is a guy here who races his R32 with R34GTT calipers and factory-sized rotors.

Other than that - yes, as per GTSBoy's post, caliper adapters are needed. 280->324mm adapters might work, and you'll 100% have to file the edges of your calipers to make them sit lower on the rotor, see attach

[Idaten]

=( Seemed like a viable option while keeping the factory calipers... not so viable huh?

[Legionnaire]

Depends on what result you're really after. If higher brake torque and faster deceleration is what you desire, then starting with rotor size is a poor approach.

If you enjoy the look of massive and shiny chunk of cast iron behind the rims, then it's a good way (not as good as two piece rotors, but still not bad), but keep wheel size and offset considerations in mind.

If you want both, then you're in for big buck expenditure

[Idaten]

Rofl. You're telling me.

I'm at the end of my wits with Endless, Brembo, etc... So expensive...

Don't get me wrong, one day I'll have 8k-10k of brakes under there, but for now, I'd be happy with stopping power... having said that, tiny rotors will look balls under the 18' TE's.

Edit:

Looks like I'll just be getting good (although still 310mm) rotors and good pads and leaving it at that for now...

Edited March 14, 2012 by Idaten

[Legionnaire]

You don't necessarily have to spend 8-10K on the brakes in order to have nice calipers and good braking, you just have to do a bit of research and think outside the box a little.

E.g. a set of rear calipers off an Audi R8 would make a good upgrade for the fronts - just an example.

[Idaten]

I'll admit I'd never have thought of that, but that's probably because it's SO far out of the box.

Honestly, without a million different cars sitting next to mine to test fit, I'd have no idea which calipers would fit. Just a bit vague in that area. Probably why I was opting for bolt-ons.

I love the suggestion though and will try to search the web for some different examples.

[Legionnaire]

A few general tips on what to look for:

1)you'll unlikely find something that would bolt straight up to the hub, so look for calipers that have radial mount holes (parallel to rotor surface), not axial mounts. This makes adapters much easier and cheaper to fabricate

2)look for calipers that take common and readily available pad shape. There is no point in buying a set of calipers and then discover that you have to order a set of pads from the only place that sells them half the earth away, and you need to sell your kidney to buy them and wait for a couple of months for delivery.

3)look for calipers that has variety of pad compounds available for it. This is not exactly same as previous point, because not all common pad shapes have high-performance pads available. And vice versa - not all common pad shapes are available in street compounds.

4)look out for pad friction patch (also known as radial depth, pad swept area, annulus, etc), as a pad too wide/too narrow/oddly shaped can limit your selection of rotors big time

5)look out for rotor thickness and diameter that calipers are intended for. This can also limit your rotor options or effectively make your brake "upgrade" an actual downgrade, say when you buy beautiful calipers that take rotor only 16mm thick

6)calipers should be common enough (or use internals that are common) to be easily rebuildable/refurbishable. Calipers that cost, say, 2k new, can be found for 500 in average or poor shape, but will perform just like new when you throw two $50 rebuild kits at them

Well, those are the gudelines. And try to do lots of reading and develop general understanding for brakes, so you could understand what you really need and why, and tell whether a particular set of calipers is suitable for you. SAU contains wealth of knowledge on the topic, but is not the only source of info.