Brakes & Tyres

[Nic]

I've decided after my dice with death, that I'm going to get some new tread on the back and new brakes up front:

 

TYRES

A few people have recommended I fit semi-slicks on the rears to help get the power (430bhp) on the ground. I currently have 18/35/285 SO-2's on the back and 18/40/245 SO-3 on the front, a few questions:

 

1. Should I and if so which make/model to go for?

2. How will the semi-slicks compare to the SO-2's in the dry and wet?

3. I currently only get 8-12 months out of a pair of SO-2's how will the semi-slicks compare?

 

BRAKES

AP Racing 6 pots have been recommended, views or anything I should be aware of? The garage will check they will fit under my wheels (18/AVS) and have said they will give me for a good price as compensation for the near death experience

 

cheers

 

Nic

 

p.s. I will have a pair of UK spec callipers and Project-Mu discs (8 months old) going after new brakes fitted if anyone is interested.

[loks]

Nic

 

PM me about the costs of the brakes. I'm interested to upgrade my J-Spec ones.

 

Glad to hear you came out of a bad situation OK but really sorry to hear about the car. My soop is usually available mid-week if you need to have a run around.... ....in the engine fixing stage.

 

Which garage fitted the problem pipe and circlip? Just for my reference you understand

 

Just exactly where is this oil slick you laid down? Don't want to follow the same pirouette maneouvre as yourself

 

Can't help too much about the tyre and brakes questions, as I have only just fitted the new S-03's all round and yet to test them properly here in HK during the upcoming rainy season.....

 

Hope your luck changes with the car soon

[Chris Wilson]

The road legal (in UK anyaway...) race tyres like Michelin Pilot Sport Cups, Pirelli P-Zero C Corsas, and Dunlop R are fantastic in the dry (worth 3 seconds a lap on my Skyline and Mazda FD at Oulton, but poor in the wet, although usable. They are all a hard compound to witstand the heat generated in track usage, on a very cold day on the road, around town, they won't heat up and may be worse than a normal road tyre. A very low profile tyre, like your 35 section, won't put power down as well as a taller profile.

[Nathan]

Originally posted by Chris Wilson

A very low profile tyre, like your 35 section, won't put power down as well as a taller profile.

 

Is that why F1 cars use massive sidewalls Chris? Then again, if true, why do BTCC use rubber bands with massive wheels?

 

I can vouch for anything Pirelli with the name 'Corsa' on it. Used to use those on my bike and boy did they stick. Only got 1700 miles out of them though :-(

 

Cheers,

 

Nathan

TDI PLC

[Adam W]

If they're a hard compound, will they last as well as a performance road-orientated tyre like Goodyear F1's or S03's etc? Are the main advantages in cornering or is there noticably improved traction as well?

 

I think F1 tyres have tall sidewalls because it's demanded in the regulations - ie if they were allowed to use a lower profile tyre then they would! But most single seaters have a similar setup, so . . .

[Rob]

Maybe using big alloys and low-profile tyres in the BTCC is a selling tool.

[Doughie]

I think v low profile main benefit is really for cornering purposes, in that it maintains max. contact patch and the tyre doesn't deform so much and try to roll off the rim. Also stiffer sidewall inherently on a low-profile tyre, which maintains v good control over contact patch.

 

But for traction, look at, for example, Top Fuel dragster tyres. they're MASSIVELY high profile. All you need there is monumental traction. They also run extremely low tyre pressures (I think less than 10psi) and the tyre sidewall is actually crinkled when the car is stationary, so low is the pressure.

[Thor]

If you are definately changing I will buy the project Mu discs from you if reasonably priced.

 

PM me with a price.

[Nathan]

Hi Stu,

 

I understand why dragsters use low pressures and high sidewalls.

 

What I don't understand is why BTCC cars run a totally different setup to F1 cars, when both require the same criterias: lateral grip and straight-line power transfer.

 

Sorry...bit of a thread hi-jack going on here

 

Cheers,

 

Nathan

TDI PLC

[Need4Speed]

Is that why F1 cars use massive sidewalls Chris? Then again, if true, why do BTCC use rubber bands with massive wheels?

 

F1 cars have to use 13" (yes 13") rims.

 

Slicks (cut or not) are no use on the road.

[Doughie]

Originally posted by Nathan

Hi Stu,

 

I understand why dragsters use low pressures and high sidewalls.

 

What I don't understand is why BTCC cars run a totally different setup to F1 cars, when both require the same criterias: lateral grip and straight-line power transfer.

 

Sorry...bit of a thread hi-jack going on here

 

Cheers,

 

Nathan

TDI PLC

 

yep it is interesting for sure.

i'm quite interested in vehicle dynamics, handling, tyres etc.

Generally speaking low profile seems the way to go on a race car, but the F1 rules demand fairly high profile tyres. I guess the tyres are so specialist that Michelin and Bridge. get round the tall sidwall issue in very clever tyre carcass construction or something.

 

Suspension travel in F1 is so limited that the tyre-wall squash is quite a large part of the whole suspension "area". Those tyrewalls must be mega-stiff cos the downforce on the cars at 170mph plus is huge, and if the sidwalls bent too much it would :

a) give massive sidewall heating, which is not good, increases tyre failure risk

b) risk of the car bottoming out on the "plank" at high speed simply due to tyrewall flex due to massive downforce.

 

interesting stuff indeed.

 

I think we need Chris Wilson to give his opinion here as suspension stuff is a bit of a specialisation for him I think!

 

 

ps. oh and the reason race slicks are no good for the road (apart from not being legal of course) is simply due to the fact that the tyre compund just doesn't generate decent friction levels at the sort of temps. road driving can generate. they need toget pretty bloody hot (and STAY hot) to work. If you made them in a "road" compound (but still a slick tyre) then in the dry they should work really well on the road.

[GavinL]

Originally posted by Nathan

Hi Stu,

 

I understand why dragsters use low pressures and high sidewalls.

 

What I don't understand is why BTCC cars run a totally different setup to F1 cars, when both require the same criterias: lateral grip and straight-line power transfer.

 

Sorry...bit of a thread hi-jack going on here

 

Cheers,

 

Nathan

TDI PLC

 

 

Big brake setups

[Steve Cargill]

Originally posted by Nathan

What I don't understand is why BTCC cars run a totally different setup to F1 cars, when both require the same criterias: lateral grip and straight-line power transfer.

 

No answers, more info though. A leMan car on display at work as 350/40 on the back and 330/30's on the front and I think the rims are 17". Even the 40 profile on the rears is a higher sidewall than normal road cars. The tyres are Bridgestones and look pretty much road legal

[Need4Speed]

What I don't understand is why BTCC cars run a totally different setup to F1 cars

BTCC cars require that the wheel fits under the wheel arch which limits the tyre rolling diameter, but they need bigger front brakes than a standard road car. Hence big diam. rims with very low profile tyres.

 

F1 cars must run 13" rims but have carbon/carbon brakes which don't need to be huge to stop the car.

[Need4Speed]

Doughie - if you're really into this sort of stuff, do you read Racecar Engineering. The really techie stuff is beyond me but there's an awful lot in there that is at the level of common sense engineering. Good article this month on what causes sports cars to take off - like Mercedes at Le Mans in 1999.

[Alex]

Nic,

 

The S-02's are about the best road tyre out there. Great wet or Dry but they don't last long. You can't really have your cake and eat it when it comes to road tyres

 

The Pirelli "system" actually advises that you use Nero Asscemetrico's(SP?) on the rear and P-Zero C's on the front. The C's are for cornering/cutting through the water. The Nero's have a bigger trad block for laying down the power. Unfortunately I'm not sure if you can get the Nero's in the size you need.

 

The Goodyear GDS (or GSD) 3's are probably better in the Wet than the others, and is a very predictable tyre. Not sure if its on the limit cornering in the dry is equal to the those mentioned above.

 

BFGoodrich make the G-force T/A KD for those only using the car on dry roads. And the G-force T/A KDW for those wanting more wet performance at a slight lessening of the dry ability. They seem to get great reviews...

 

You won't gain alot on the road from stepping up from UK's to AP's unless you are regularly standing on them from high speed. IE you'll only really affect the fade

 

The Mu rating of the UK spec brake kit is very good. Higher than many sports cars, if on a dry road you can apply the brakes and get the ABS to cut in your issue is down to mechanical grip and not braking power.

 

FWIW the AP's normal retail for about £1500 for the fronts, do you have the j-spec rears or UK rears? Either way having the AP's on the front may affect the brake balance/bias. So you may need to get an in-cabin bias adjuster.