Need4Speed

F1 cars have to use 13" (yes 13") rims. Slicks (cut or not) are no use on the road.

Warped discs - You can warp them in a few miles of track use, so a few thousand on the road should be no problem. Just replace them.

DON'T DO IT. My experience of a full de-cat was an out of control boost and a big wheel-spin problem. On my J-spec car it made the power delivery too severe for everyday driving. My personal opinion only here, is that a boost controller is the only way to go. I get the same power as a decat car but it's controlable and you can dial it down when the roads are wet or the air temperature is low. My verdict - highly over-rated.

I cross ref'd the Porterfield part numbers on their web site and found GS300 rears. It may be, of course, that American spec. GS300s are different.

Paul, what's behind all this, now you've got a discussion going? That's about 7BHP used just to shift, let alone switch it on.

Correct me if I'm wrong but I think J rears are the same (caliper) as Lexus GS300.

It's all small items though compared to the engine, transmission, diff, and even the wheels. 1% is about 16kg, thats a hell of a big sub.

only by a very small amount

Alex The sum of the two front corner weights expressed as a percentage of the all-up weight should be 53% and the rear 47%. To prove the point, if anyone has a suitable corner-weight gauge, they should be able to show approx 415kg on each front wheel and 368kg on each rear. The car won't be perfectly balanced left/right, but the principle is there. Generally the weight includes fluids but not fuel in the tank. A full tank would add 60kg+ to the all-up weight and, bearing in mind the position of the tank, about 30kg or so to each rear corner weight. An easy alternative would be to put the front wheels on a weigh bridge and then the rears.

Has anybody put a corner-weight gauge on to verify this? Suspension does not affect it.

JC if you get stuck, I did this last year and photographed it all. First thing to do is check you wheels will fit over the new caliper. Take one J-spec off (leave the pipe connected) and remove the disc. Bolt on the UK caliper and try refitting the wheel. If it clears, you can proceed to dismantle everything, if not you need to sort clearance out before anything else. Fluid; I use AP Racing Fluid available from Demon Tweeks via mail-order. If you want any photos, let me know [email protected]

You're either a total nut case or you have a bit of a problem. I've run mine for a year now with up to 1.1bar, and get 20-22 normally and 7 on the track. I cant see how you can get 12mpg on average. Where do you live? Santa Pod?

Mine recorded 360bhp with both cats in at 1.1bar - G Force RR - The first Supra ever on their dyno.

My experience of j-spec brakes is two hard stops from around 100 and they disappear completely.

I can confirm the Porterfield R4 poads do not fade, but the will heat the discs up to warp factor 1. Absolutely no problem on the road, but the discs do start to shake after a few hard track laps.

Do you mean complete pedals or the alluminium things that are used instead of rubbers? If the latter, try Demon Tweeks.

I have Porterfield pads all round from Whifbitz. The Pads are R4 (race) compound, on UK front and J rear. They're noisy and dusty but you can buy more conventional compounds. I used to have EBC Green on std. J-spec, they were the worst disc brakes I've ever met.

In relation to 19" or bigger rims yes.

Offset and caliper clearance are two separate issues. In fact caliper clearance is nothing to do with offset. The issue is the shape of the wheel centre; once that clears the calipers, the issue is the offset that is correct for the suspension geometry. Personally, that gold Supra looks naff, particularly such big wheels with small discs behind them. This reminds me of Corsas with 15" rims and tiny standard brakes. I'm not going to comment on the high-riding black Lexus.

The one I have is a belt on a slotted 1/2" sq. drive socket that works a bit like a chain wrench; very effective

Maybe I should make some of these tools up!

Am I the only person on this BBS who finds the car better with at least 1 cat in? - Still got that CW 2nd pipe if anybody wants one. MOT on Monday.

It's a good idea to leave the a/c on all the time otherwise the gas will gradually escape.

It never ceases to amaze me that people buy what was a £40k car and then try to work on it without decent tools.

285/40x17" Rear Tyres Is there anybody out there running this size rears, and if so can you tell me what the rolling circumference actually is (rather than a calculation)?