running slicks with 18's ????

[_Nathan_]

Aps fit under 18s fine, assume you have am suspension already?

[alexk]

I am running M3 E46 18" with Dunlop slicks.
All rims are 9J and I have wider rear slicks (rears are 240 and fronts 210).
They can fit in the AP brakes (and I have the CP5555 calipers with 18mm thick pads // my front rims are 9J).

I run them with OEM suspension.
I am VERY HAPPY with them. The grip is phenomenal.
I don't see any problem in the car.

[shimmy]

Why are you running slicks

Speed

Cost

???

[alexk]

Why are you running slicks

Speed

Cost

???

In the bike I used to run slicks all the time (road use too).
As you know shimmy (you helped with the transfer :thumbs I got the slicks for the car in a good deal.
The traction is so much better compared with the cups so why not to use them ?

[daniel_csl]

Or you can buy 4 x rear 18" bmw wheels, as per AlexK, for around 200:thumbs:. There are other sticky options to consider that are a lot cheaper than cups and maybe safer than slicks.

Thanks for the reply! definitely answered my question

The grip is really good, but the issue is the cost of cups all the time.

I know someone who bought ten sets of slicks, used, with loads of grip for £300 off ebay. they were 18's, and i think were also Dunlop

£1200 for one set of cups seems a little excessive to me. ive just worn mine, i think a change to slicks would be a good idea.

You can buy a brand new set of 18'' super lightweight rota wheels for £800

[alexk]

Or you can buy 4 x rear 18" bmw wheels, as per AlexK, for around 200:thumbs:. There are other sticky options to consider that are a lot cheaper than cups and maybe safer than slicks.

Yeap you can get good deals for 18" bmw wheels.
I am not sure why you say that slicks are unsafe ?
Have you tried slicks ?

[shimmy]

My take on slicks are like this.

Cheap worn used slicks are good value but probably not any quicker than new Cups. New Cups will on a good set up probably last around 5-6 proper trackdays so cost say £200 per trackday, without discount. Used worm slicks will probably run 2-3 trackdays max be costing say £100-£120 a track day

My 18 inch Cups cost me closer to £800 and Kuhmo are similar and on square set up will likely last 8 trackdays and cost around £100 per TD.

You can't run slicks on road so you have to lump around 4 wheels to every trackday which is a real faff. You can't run Geo for slicks and road at the same time so you'll never get the best out if slicks on a road car.

I've always said thatci wouldn't run slicks without cage for many reasons.

[alexk]

8 full day trackdays for a set of cups isn't it a bit optimistic ?
I don't have the experience that you have shimmy (having only bought 2 set of cups up to now) but I find it a bit difficult.

Some colleagues were explaining me that they are supporting slicks+cage for safety reason, but personally I am not getting paid to race my roadcar, I am just a hobbyist having fun.

[shimmy]

8 full day trackdays for a set of cups isn't it a bit optimistic ?
I don't have the experience that you have shimmy (having only bought 2 set of cups up to now) but I find it a bit difficult.

Some colleagues were explaining me that they are supporting slicks+cage for safety reason, but personally I am not getting paid to race my roadcar, I am just a hobbyist having fun.

I think if you run slicks for cost savings then that makes sense as 4-6 TD for Cups is what I used to do. Better geo and understanding of pressure and temperature effects helps you to maximise this, stiff coilovers helps again and square set up allows an extra 2 by swapping front and rear Tyres. My 18 inch Cups did the 8 2010 trackdays for me and are no longer road legal but gave not worn to canvas anywhere yet so could still be used.

[Thorney]

Funnily enough I was talking to a guy on Saturday at Bedford about slicks on his M3 so may as well repeat the advice here.

Identify the reason why you want slicks, is it pace, fun, cost or all of it. There are positives and downsides though.

Positives
1. Fun, slicks are fun, more fun and lateral grip than any cup or cut road tyre.
2. Cost, part worns are relatively cheap and available (this will likely get better as BTCC move to 18" rims)
3. Saves wear on normal road tyres from track work
4.18" rims handle better in track

Downsides
1. Set up, to use a slick on an M3 you need min 4 degrees of camber to make full use of them, otherwise you will just wear them out quicker and compromise the handling rpbably where Shimmy gets the comment that they are no faster than cups, he's right, with 2.5 degrees front camber a front slick will overheat in 2 Laps, get greasy and slow you down). If you look at Alex picture you can see the tyre pick up on the inside edge of the tyre - too little camber.
2. Wear on the car, slicks have 40% more lateral grip than road tyres, that stress goes through the chassis so bushes, suspension mounts will all wear more, this includes the chassis, there's no evidence that slicks will damage the chassis but I would certainly be checking subframe mounts etc more often if I ran them on a road car.

There's no right or wrong on using them, simply personal choice of how to get the best out of your car on track, however what slicks are doing is offering more tyre grip rather than mechanical grip that things like suspension etc offer so compare a car with decent suspension on cups with a car on stock suspension on slicks I'd be interested to see which was quicker.

[Thorney]

Sorry, can't edit post on iPad easily, forgot to mention on set up it also depends on spring rates, OEM springs will be too soft so the car will roll more doling the car onto the outside of the tyres, this heats them up, drops their grip and wears them out.

Also be wary about buying part worns, most people have no idea how to look at a slick to determine its life, there are wear indicators but these are only indicative, most slicks lose about 30% of their grip after 5 heat cycles.

That said, I've got about 10 sets of part worns for CSL cup cars that happy to sell for £100 a set

[DuncanR]

Thx for that input JT, as you know, Im looking to "try" a set out ... just for the hell of it really ... I also wouldnt be doing it without a cage though, as per Shims statement. All i need is some kindly person to let me have a part worn set to complete the exercise whilst I still have a set of empty 18"TD rims to bang them on !:whistle:... good point about the BTCC and the possibility of more availability.

[alexk]

1. Set up, to use a slick on an M3 you need min 4 degrees of camber to make full use of them, otherwise you will just wear them out quicker and compromise the handling rpbably where Shimmy gets the comment that they are no faster than cups, he's right, with 2.5 degrees front camber a front slick will overheat in 2 Laps, get greasy and slow you down). If you look at Alex picture you can see the tyre pick up on the inside edge of the tyre - too little camber.
2. Wear on the car, slicks have 40% more lateral grip than road tyres, that stress goes through the chassis so bushes, suspension mounts will all wear more, this includes the chassis, there's no evidence that slicks will damage the chassis but I would certainly be checking subframe mounts etc more often if I ran them on a road car.

JT thanks for the input as a start.
I think most points are correct, however I want to comment on some things.

The pick up of rubber in my slicks in the photo is from a cool down lap in Spa, full right where is was full of rubber from other cars and I picked everything inside (because my car has camber so in the straight line the inner part of the tyre is applying more pressure on the tarmac).
The extra camber has to do with the driving style + speed.
If your driving style is different (and possibly speed) you might not benefit from excessive camber.
If you see the condition of my cup tyres after 18k road kilometers, 22 laps in Nordschleife, 2 track days in France and drifting in CH, GR and the racetrack, you won't believe it !
I can take some pictures and there you can see that my 'stock' camber (max setting btw) is fine. I don't have uneven tyre wear.
So in a similar way my slicks don't have uneven wear (when I corner the tyre it has a 90 degree angle) so I that case I am not sure how extra camber would help me.

You could say that I am captain slow but I don't think so.
In the French track I could lap 1.32 in my slicks in the wet (backing off 2 fast corners not to have an exit with 180km/h). The 1.29 is feasible AFAIC.
Doing 30 minute sessions I didn't see any degradation of grip nor my tyres became greasy.
What I noticed is that my brakes became EXTREMELY hot, which is justified by the extra grip of the slicks.
And this is a track that an aftermarket suspension would make a difference because it has a lot of tight corners.
It was also interesting to see that a Nissan GTR tuned, with semi-slicks and wheels and suspension and gay-4-wheel-drive wasn't faster than me in the corners (I will say again the tarmac was wet).
I can also quote some other laptimes in the same track in the DRY.
M coupe with michelin slicks, racing suspension, cage, exhausts etc. 1.35
997 GT3 RS with semi-slicks 1.31

Would a CSL with roll-cage, suspension, geo on slicks would be much faster than me ?
100% YES !
But I am a hobbyist so I am happy with what I achieve while having fun and not taking it too seriously (I respect that others see it differently though).

[shimmy]

Alex, i dont think John was having a go!

I think the point being if it is speed you are after with slicks then where slicks get alot of their speed from is running with firm springs, rigid caged car, and the right geo.

I spent alot of time with Dontdobends who was running his m3 race car and previously his CSL on used slicks and i think Johns conclusion was that on a non race car (or non set up race car) used slicks were more or less comparable to new Cups for outright pace, maybe with a slight advantage with slicks if you have a/m suspension

id love to give slicks a go tbh, and maybe next year i might break my rule and run some somewhere or i may have to just wait fior a race drive:smokin:

[DuncanR]

id love to give slicks a go tbh, and maybe next year i might break my rule and run some somewhere or i may have to just wait fior a race drive:smokin:

You get the slicks mate ... and I will supply the car !! seeemple !!!!:thumbs:

Lets make it at Bedford tho shall us ? .. just in case !!