best tyre pressures for 225/45/18 conti?

[GreyGhost]

IMHO anybody running their vehicle with tyre pressures outside the manufacturers recommended tolerances for said vehicle, will cause a detrimental effect on all aspects of handling, wear and stopping distances.
32 all round on 225 45 18 ZT.

[Hampton Caught]

Originally Posted by pondweed

I must admit, the bit about the inside tyre losing grip out of junctions makes me question sanity... and wont the centre of the tyre tread be at risk of wear?

Pondweed, don't question my sanity...... question my right foot!

In running my tyres above 32 psi (they're at 38 all round currently), I'm trying to even out the tyre wear issues I've had already. The outer shoulders of the first set wore below the legal limit in 11,500 miles (and that was from new), which made me wonder whether the 32 psi was sufficient!

I've had the four wheel alignment checked and 'adjusted' but I believe the only suspension element that actually can be adjusted is the tracking at the front. I would be very interested to hear from any member who has 'hands on' experience of our cars as to whether there is any adjustment possible to the rear suspension......

Steve

[kookiemg]

Originally Posted by pondweed

bit confused now - you've just said bmw (fronts quoted here) run between 34 and 42 ideally... and then agreed with the 32 all round for the 75/ZT 225 tyres right at the end??

If 32 allround is "manufacturer recommmended", can you envisage why bmw are specciing so high on similar tyres? I realise they are rwd, but...

Yes - sorry...I can get confusing...to myself....
In the first instance I was just trying to confirm that bmw do have quite high pressures on some of their vehicle/tyre arrangements - and the difference between 'normal' and fast/fully loaded is extra-ordinarily high on some models. Useless post really...as I don't know the reasoning behind it, other than the rwd/suspension set-ups and weight distribution. I can only conclude that the set-ups have been derived from comfort/safety tests and is an indication on their preferred 'reaction' time from the shocks/springs/brakes.

It would appear that the tyre itself (eg conti M3) can withstand nominal pressures of all those stated (so quite a wide range) but I have no idea what happens to these momentarily, when under various loadings due to suspension, brakes, direction and road surface - this is going to be car manufacturer specific I would think.

In concluding that 32 is probably about right for the 225s, I was relating that to experience on my CDT with 195s and a tall sidewall, needing 34-ish to imo. I'm keeping them within car manufacturers recommends (just...)

I would do a little experimentation, within the guidelines and see how the car feels and whether the tyres are getting scrubbed on the outsides too much - incidentally, I've recently had mine 4-wheel aligned after all 4 tyres wore on the outside edges, it's a lot quieter now and seems a little sharper turning in etc - yet to see if the wear is going to be totally even, but I have a feeling it's improved.
Chris