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[Lesopc]

330mm discs went under 17s on the ST, but if you are going V8 than surely the wheels would be either 18 or 19's?

362mm on the VXR vectra needs 19's

Replacement carriers are generally sold as part of the upgrade kit fairly sure if you are modifying the engine bay to fit a V8 adjusting a couple of caliper carriers will be childs play!

Guess it all depends if you want more area and more pistons or same area and more pistons?

Another thing that will need checking is bore size on the replacement discs as i would assume FWD front hubs have a different bore??

I am looking to go to 18" Ronals so anything that will go inside those is good. I think that for purpose the discs need to go bigger with more pistons in the caliper too?

Couldn't the wheel size change mess up your speedo and odometer!

http://www.miata.net/garage/tirecalcold.html

Just thinking :-? [smiley=engel017.gif] [smiley=engel017.gif] [smiley=engel017.gif] [smiley=engel017.gif] [smiley=engel017.gif]

Not according to some who have replied to a previous post. Just as long as the overall wheel diameter  stays the same, which means lower profile rubber?

[TestOmega]

You are right I did not recognize that, sorry

[Squidy]

if your buying new disks i would get grooved, i've heard that drilled disks can crack and are only ideal for race track

[DodgeyDave]

I'm no expert but I'd be very surprised if drilled discs were prone to cracking, most high powered cars like Porches come with drilled discs as standard these days

[Squidy]

I'm no expert but I'd be very surprised if drilled discs were prone to cracking, most high powered cars like Porches come with drilled discs as standard these days

im not 100% sure its just what ive heard that it can be a concern, plus i think that grooved look better

[aaronjb]

I've heard the same - as I understand it, it all depends how the discs are manufactured.. aftermarket 'drilled' discs were often just that - plain blanks drilled through - and could crack where the drilled holes produced stress risers, whereas Porsche (etc) drilled brakes were manufactured that way (I'm guessing that drilling prior to stress relieving the metal stops the problem, but I'm no metallurgist)

EBC 'drilled' discs are dimpled, though, to stop that problem.

[Lesopc]

I've heard the same - as I understand it, it all depends how the discs are manufactured.. aftermarket 'drilled' discs were often just that - plain blanks drilled through - and could crack where the drilled holes produced stress risers, whereas Porsche (etc) drilled brakes were manufactured that way (I'm guessing that drilling prior to stress relieving the metal stops the problem, but I'm no metallurgist)

EBC 'drilled' discs are dimpled, though, to stop that problem.

Dimpled seems a new way of doing it these days, as the drilling does not go full travel through the disc?

[Kevin Wood]

Drilled or grooved disks are purely cosmetic unless we're talking about motorsport use, though. The holes in drilled disks can act as stress raisers and promote cracking. Not a problem in motorsport use where the disk won't get many thermal cycles before being binned, but on a road car where you might expect the disk to last 60k miles, a couple of years or so I wouldn't bother.

Kevin

[Marks DTM Calib]

One could argue that you dont need to upgrade the brakes unless your planning to drive more agressively

The weight has not seriously increased and its not like you brake against the engine power.

[2woody]

there's lots of stuff to bear in mind here.

weight. My Holden actually weight less that my MV6

tyres. DO NOT UNDER ANY CIRCUMSTANCES do anything which increases the hub height of the the tyre/wheel package. So, if you go for 18" wheels, then lower-profile tyres are a necessary. Actually, you're going along the right lines - decide on the size of brakes you need for the performance you have and then fit the wheels you need to clear the brake package.

I'd suggest that around 330 to 350mm discs are appropriate. But I might be wrong - I only have 20 years of brake designing experience.

I have three Omegas that may be of interest to you :-

Holden Commodore with 300mm discs ( eek ! ) twin-pot GM calipers - hopeless for the performance.

Opel Lotus Omega with 330mm discs ( really good brakes, but unreliable ) 4-pot AP calipers - think £2500 for a complete car's worth.

Opel Omega EVO 500, with a 350mm brake package that I've come up with (18" wheels required) reverse-engineered for about £250

whatever you decide to fit, then you need to have the package developed by a professional braking company, and by that I mean Bosch, Conti-teves or AP racing, and not a second-division outfit like EBC, or indeed anyone who would sell you a grooved or drilled disc.

Unfortunately, I don't carry the third-party insurance that would let me divulge the 350mm kit contents.