Dougal,
My comments on the F1 (235/40YR18) versus Bridgestone S-02 (205/55ZR16):
1: F1 has softer sidewalls = better ride (even with much smaller sidewalls). At 40psi they are not skittish at all but conversely still rather soft and mushy.
2: F1 has Better durability
3: F1 produced negligible improvement in true grip on the road during cornering and braking
4: F1 get worse when hot and do induce more oversteer in the warmer weather
5: F1 less predictable and progressive when on or over the limit than S-02
6: Major Concerns after a few RS4 owners have had their F1s split doen the middle turing hard use! Yes it is true. If no-one reads this I might move this to a new thread under the general car chat threads.
7: Have to admit F1s are cheaper and more readily available than the now limited-producion S-02. Most importantly you can still get some S-02 sizes as they are OEM on some really high performance road cars (Some Astons, Beemers, Honda S2000, Porsches, Ferarris etc).
8: S-02 tyre (as I have always stated) is the best street tyre I have ever tried. Ask John Roberts what he thinks as he has just fitted a set to his RS4 - top choice mate [img]images/graemlins/thumbs.gif[/img]. Would be interesting to see, JR, if you agree with my comparison with your RS4 experience.
Also, not a fault of the tyre make but increasing tyre diameter and width has reduced my top speed by 4-5 mph (GPS figures on the same roads in comparable conditions) and the car now has an increased tendancy to tramline on rutted roads (most motorway slow lanes).
Comments on 235s. These apply only to my Goodyears as every manufacturer has a slight variation in the interpretation of the size labelling convention (revs per mile and section widths vary between manufacturers). Please look on
www.tirerack.com as this is an excellent resource for tyre manufacturer's data. Consider these comments on the fact that I have non-lowered suspension (and cannot lower it practically due to the larger tyres). Oh yeah, 35mm offset and 8" wide rims.
Front: tyre sidewall text very close to the steering arm ball joint. A few sheets of paper can be slipped throug but I think a 1mm spacer would make it comfortable enough since the tyre shouldn't flex too much where it is tight. Since I only had a 6 mm spacer to hand I fitted that which also brought the front tyre more inline with the rears. Since the spacer fitment I have polished the little domed head fastener that holds the plastic shield against the top of the wheel arch when going Kamikaze on bumby back roads. Can't comment if this would happen with 1 mm spacers (suspect not, but couldn't tell for sure without trying it).
No other clearance issues except that the tyre just touches the plastic shield during full lock but this is trivial.
Rear: A typical Audi 'feature' meant I had to use a 3 mm spacer to avoid the stupid suspension upright that they decided to use on the avant (top wishbone is very short and above the tyre to maximise trunk width). The upright is getting on for half a metre tall and has a huge bend in it go around the tyre profile. 3 mm spacers mean that I now have the rears pretty flush (few mm proud if anything!). This means that they touch very slightly when I have 4 people in the car driving over pot holes in the road or am getting carried away on those fast bumpy lanes. Must flare the arches very slightly as there is nothing I can do with rear upright short of fabricating a new one (we have the technology! [img]images/graemlins/wink.gif[/img] ). The same upright is used in the RS2 but the RS2-unique Dunlop 245/40ZR17 tyres and a rim 0.5 inch narrower than the S2 Avus 16" means the sidewall shape clears this upright much better than my present setup.
Another point, the 18" F1 tyres have meant that my speedo is now less than 1% out of accuracy from 50 to 150 mph. I have verified this by GPS over long sample periods.
Lee (Sorry about the rample but hope it is constructive!)