Non runflat tyre sizes - implications?

[DR-Z]

Del_tl1000r what pressures are you running in your 235/35/19 & 255/35/19 setup?

[del_tl1000r]

34 front and 36 rear

[del_tl1000r]

Sorry that's for the 17s I had. Should be 36 and 38

[mcbutler]

Even though I have practically new RFTs, I'm going to take the (expensive) plunge to go to normal tyres. My 19" 326 wheels are currently crack-free, and I'd like to keep it that way. Also would be nice to soften the ride a little.

Reading around, seems likes the optimum tyre sizes will be 235/35 front and 255/35 rear. That will increase the diameter a little on the fronts, and quite a lot (an inch) on the rears. Apart from the benefits of a better ride, there appear to be a few other implications of upping the tyre size:

• Speedo will read lower - but as it reads a bit high at the moment, should be OK.
• Wider tyres may give a bit more grip
• ..but greater rolling resistance of the wider tyres could affect mpg (which is already pretty poor)
• The car will sit 1/2 inch higher at the rear on the stock Msport suspension. Those of you who have done this, it's this noticeable? (I don't particularly want to start messing with the springs).
• Larger rears will also reduce acceleration - not sure how noticeable this would be.

Not sure if I've missed anything significant. Any views on the above?

Really, none of this is significant! The only thing with wider tyres is you need more weight to force them through water so your wet grip will be less, not that anyone not racing on a track would ever notice.