Tyre pressures for 235/40 x 17's

[ericd]

I've looked in a few places but can't find any threads with this, anybody know what the pressures should be or what others are using ?

Cheers

[s2driver]

What make of tyres do you have?

Reccomended pressure varies between manufacturers. My dad's car runs anywhere between 38 and 46 psi depending on his tyre choice.

I run my Goodyear Eagle F1 GS-D3 235/40YR18 at 40 psi always. BTW my Goodyears are crap: will never buy them again [img]images/graemlins/033102bad_1_prv.gif[/img].

Lee

[Greg_S]

On the boot of mine for 225/45 Zr17's audi reckon it should be 41 PSI so it cant be far off that.

[Doug_RS2]

They sound high - I run my 225/40X18 Toyos at 36f and 34r -any higher and it gets very skittery - not even looked at what they should be - just spent a few hours changing pressures and trying it.

Lee-why do you think the goodyears are cr4p - I need new tyres and I was considering getting them to try(I can't fault toyos though). I was also going to 235/35X19 but was wondering if it was too wide to fit under-obviously not if you have 235s.

Dougal

PS-when are those conrods getting fitted?

[ericd]

they're "dunlop sp sport d40's" don't think they make them anymore !

[s2driver]

Eric, not familiar with those tyres. Contact Elite as they should be able to advise on pressures for any tyre make, model and size.

BTW, dropped my rear pressures to 34psi in an effort to reduce the servere lift-off oversteer I am getting when pushing the car through tight-ish bends close to the limit. Might put the standard rear S2 roll bar back on (or make a new stiffer front one!) if it doesn't go away with my next tyres.

Lee

[s2driver]

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!)

[Greg_S]

double checked the label on back of my car and manufacturer spec is 36 PSI all round

[s2driver]

double checked the label on back of my car and manufacturer spec is 36 PSI all round

Yes, but that is for the standard fit 205/55R16 right?

[Doug_RS2]

Lee (Sorry about the rample but hope it is constructive!)

Keep the rambles up - it's the only way we learn!

[s2driver]

I learn by trial and error, and stupidity.

Shame we haven't got the experts like Paul N and Mihnea C from S2Central here. They really seem to know their onions and would probably have hugely valid input on other S and RS weapons...especially considering they are Motronic gurus too! I'm having trouble keeping up with posts. Those talks of monster turbos and huge horsepower really does make me salivate like Homer J Simpson does at the promise of doooonuuuuts!

Lee

BTW, I knew about the possible clearance issues before I bought my wheels. I determined the offset, width and tyre sizes based on measurements I had made. If I put a 1mm thick spacer on front and rear I would probably have no clearance issues whatsoever. Rubbing on the rear upright only happened during hard right cornering without spacers so it shouldn't happen if I put brand new wheel bearings in. 3mm and 6mm were the only spacers I had.

Oh yeah, someone from Dawsons body shop fitted 19" rims to a Nitrous'ed S2 Coupe. Might be worth asking them for opinions too if you haven't placed your order yet.

Mmmmmm 19" = 378mm fully floating discs and water cooled no-dust-seal AP brakes brakes!!!!! Nice one!

[Doug_RS2]

I'll look into the wheel sizes a bit more - I think it might be a bit too tight.

I'm hoping the Paul/Mihnea fully custom chips will get me upto 375/380bhp in the next few weeks - Getting mapped while on the rolling road with Mihnea and Paul there would give me a lot of confidence in it - and the trip to London and paying for a couple of hours on the rollers will still be a bargain - top guys but I think they are struggling to find enough hours in the day!

Big brakes - I suppose I could get custom brackets made to space out my AP 4Pots and get those big discs on the bells I have! What are floating discs?

Have you looked at the pictures/files on the Audi20V_Kruemmer yahoo group - that's what I call serious mods.

Dougal

[Greg_S]

Yeah is for the standard. On the label it has the standard size and 17's listed with tyre pressures being the same for both.

then its 41PSI when the car is fully loaded which is what foxed me to start with.