Silver Surfer

Could someone please let me know what size 17 inch slicks I need. They are to be fitted to Mims with an ET45 offset if this makes a difference.

Thanks

SS

Pete Croney

Slicks are measured differently to road tyres, in that the second dimension is the diameter of the tyre when it is uninflated.

A standard Subaru wheel and tyre is approx 60cm in diameter and this is the size slick you should use... ie 200/60 17

A 65 (a common 17 slick size) will increase the gearing by nearly 9%. Fine if you have a very short ratio'd RA but not much fun on a UK Impreza.

Silver Surfer

Thanks Mr Croney, U got my locking wheel nuts in yet?

Hoppy

Silver Surfer, I've said before that 17in slicks are no so hard to get hold of as you're led to believe.

I was wrong! Sure you can get 17in slicks, but as Pete says above the common size is 65cm diameter. This is very big and I think impossible to fit on a standard road car where I believe 62cm to about the realistic maximum.

I'm looking into it at the moment and, at the very worst, I think Michelin produce something suitable - £160 a corner, though!

If I get any joy, I'll post the info here.

Hoppy

Silver Surfer

I take it that 210/620 17 won't fit then?

Help or tips appreciated.

Hoppy

210 no problem. 620 maybe okay, but I've not tried so can't be sure. I'd take the gamble, though. What's your suspension height? If it's low, be extra careful.

Here is my fall-back position. If I can't get exactly what I want (Michelin have yet to respond, and Dunlop appear to list something very close) Yokohama have a new tarmac tyre A006T with semi-slick grooves. They are "championship winning tyres giving maximum adhesion in wet and dry conditions." Sounds good! I'd go for the 190/610x17 jobbies.

Search not over yet. Why am I having such trouble spending several hundred quid?! I spoke to every tyre manufacturer at the Autosport Show and they all knew bugger-all!

Hoppy

Silver Surfer

The car is low - thanks to Leda b - I may have to give it a go!

Thanks & any further info please post!

Andrew O'Hara

Silver Surfer,

A road 205x45x17 measures 616.3mm in diameter so a 210x620x17 is only 9.7mm taller and 5mm wider. A 210x625x17 is little bit too tall. But as Hoppy says maybe a 190x610x17 may be best.

Hope this helps



[This message has been edited by Andrew O'Hara (edited 30 January 2001).]

Silver Surfer

Guys thanks for the help. I have agreed to purchase a set of 210/620 17's in vgood condition for £130 for donno on the 18th. Lets just hope they fit. Hopefully with the removal of the rubber strips on the rear they should be OK

Thanks and any info on Yoks would be appreciated

NITO

Guys,

I was on the phone to Demon Tweeks yesterday, the most suitable I came across..were Michelin S7A 210/61/17 slicks at £140+vat! Personally I'll probably wait until yokohama bring out a semi slick of some sort as I don't fancy using full slicks on my car!

Nito

Silver Surfer

The ones I have bought are Inters which, correct me if iam wrong are a grooved slick.
Price seemed pretty good@ £180 a set new or £130 v good

NITO

I am more than likely wrong here but I was under the impression that intermediate slicks are just a different compound as opposed to having tread on them. They certainly wouldn't be road legal, even the tarmac spec rally tyres are apparently not legal unless you are running on the kings highways in an FIA event or something!!

Nito

Silver Surfer

The inters I have ordered are grooved so does anyone knwo what an Inter compound is?

Mike Tuckwood

Intermediates are sort of half way between Hard compound and Soft compound.

Silver Surfer

Mike thanks for the reply, would you recommend these for track days or do you think I should go soft compound?

Mike Tuckwood

I would go for the Hard compound myself, they will last better and with the weight being carried by our predominantly road cars, (i.e. more than twice the weight of a race car), they will work better.

Soft compounds would get ripped to shreds/worn out very quickly.

Mike. <I>(just my opinion of course)</I>

Andrew O'Hara

Silver Surfer,

Can you tell me where you are getting your intermediates from

You can email if you like. Because I'm looking at about 4 sets tonight for roughly the same price per set


Thanks


[This message has been edited by Andrew O'Hara (edited 31 January 2001).]

[This message has been edited by Andrew O'Hara (edited 31 January 2001).]

Hoppy

Guys, I picked up a set of very good Dunlop SP Sport 210/620xR17 slicks this evening (sorry, last evening 31st Feb) from a guy (Andy McGowan - see ad in Private section) in Milton Keynes who has a whole garage stacked with the things! £130. (Best be quick though, as I drove off, another punter in a P1 pulled up!)

As soon as it's dry, I'll stick them on the car and see if anyhting fowls. I'm hopeful as although the width (and wheel offset) is critical on a Scoob, I'm hoping there might be just a bit more lee-way on the diameter.

Compound is 894 (same as my 16in slicks which got well hot last summer). Dunlop call this "Hard one brand" in their literature (not very helpful) but it sits right in the middle of their hard-to-soft compound table.

I'll let you know how I get on. If everything's okay, AP 6-pots here I come!

Hoppy

Hoppy

Further to my last post, I've now had the tyres fitted and given them a run. Spec as above, fitted to Speedline ST2 wheels with 52mm off-set. Car with two rear passengers, full tank and the bumpiest local road I could find. And it was bumpy! Nothing touched, rubbed or scraped.

Well pleased! After months of searching, I've now got some cheap part-worn 17in slicks that fit!

A couple of further comments. Even with the car stationary, the gap between tyre and wheel arch was minimal. Anything less than 50mm offset would catch (Prodrive lowered suspension). The MIMs with ET45 will not go.

Mike Tuckwood above comments that a hard compound slick is probably best. Judging by the state of my 16in Dunlops (identical tyre and compound to my 17s) he has a point. They get so hot that they pick up loads of crap - lots of rubber off the track and even a few *** ends welded into them from the paddock! More seriously, the inner side walls have a few cracks, presumably from excessive flexing and distortion. I run around 28 psi on track. Any comments appreciated.

Hoppy

Andrew O'Hara

Hoppy,

Try dropping your pressures a bit to 22-24 psi

See how that goes

[This message has been edited by Andrew O'Hara (edited 03 February 2001).]

Hoppy

Andrew, thanks for that. I'll certainly give it a try.

I've done a lot of karting in recent years and, if the tyres were going off through heat, I'd drop the pressures - anything down to 8 psi at times.

But that was to cool them down and in extreme circumstances lowering pressures would reduce side wall stiffness causing flexing and even more heat. Then it was time to do the opposite. On one roasting hot day we started the heats around 14 psi, already pretty low, and as the day warmed up dropped them down to under ten and went quicker. Then we hit a brick wall and dropping the pressures further made the kart slower and harder to drive. So I banged the pressures up to 25 psi and went quickest of all. This is not common practise but on a really hot day there are usually a few front runners doing the opposite of what you're supposed to do. It especially true of fast circuits where reduced rolling resistance is an important factor.

I'm very aware of how critial tyre pressures are on track, it's just that it seems to be more of a black art than a science!

At Donington last year, it was very hot indeed and I wonder if going in the opposite direction, ie up to 35/40 psi might stop the flexing. The more I think about it, and sorry to prattle on if anybody's still reading this, the more Mike Tuckwood's comment about running heavy road cars on competition tyres has a lot of truth in it.

Any further comments appreciated.

Stef, what slicks and pressures do you run? Had any side-wall cracking?

Hoppy

Andrew O'Hara

Hoppy,

I raced Karts on a semi professoinal basis for 11 years including winning the British Championship in 1989 and we never raised pressures to that sort of level, remember a kart weighs nothing compared to a car.

I was speaking to Pete Croney today and he recommended between 24-28 psi which if I remember he said he runs with on track.

Good luck

Silver Surfer

Questions Guys

Will these slicks fit on an MY99 UK car on ET45's if the rubber trim is removed on the rear arches?

Thanks

Andrew O'Hara

SS,

According to Mr Croney, they will fit when you remove the rubber strip cos I bought a set of Mims (ET45) from Pete on Saturday and asked the same question

btw how did you get on with the car & brakes on Saturday

[This message has been edited by Andrew O'Hara (edited 06 February 2001).]

Stef

Hoppy.
I was using Yokohama 16" slicks on my old wheels, but will probably try these 17" ones now. I used 26psi in mine, and got no cracking.

Stef.