A note on tyre pressures and tyre wear

[Busterboo]

I had my 35i serviced on Thursday last week. They “corrected” the tyre pressures up to the run-flat pressures. I could tell straight away as it felt much harsher, skipping over rougher roads, bouncing on mid-corner bumps and feeling more nervous on wet roads.
I’ll be setting the pressures back down to f36/r38 tomorrow.

I came to the 35iS from 5 years in an 911, so the 36/44 pressures were no surprise, because they're the same for both cars and neither car could or can be exploited to its best without them.

So, it's tempting to wonder, if yours is "much harsher, skipping over rougher roads, bouncing on mid-corner bumps and feeling more nervous on wet roads", that it's not the pressures that are the problem.

[mr wilks]

I had my 35i serviced on Thursday last week. They “corrected” the tyre pressures up to the run-flat pressures. I could tell straight away as it felt much harsher, skipping over rougher roads, bouncing on mid-corner bumps and feeling more nervous on wet roads.
I’ll be setting the pressures back down to f36/r38 tomorrow.

I came to the 35iS from 5 years in an 911, so the 36/44 pressures were no surprise, because they're the same for both cars and neither car could or can be exploited to its best without them.

So, it's tempting to wonder, if yours is "much harsher, skipping over rougher roads, bouncing on mid-corner bumps and feeling more nervous on wet roads", that it's not the pressures that are the problem.

Comparing apples with oranges Buster my current 997 i run the recommended 36F 44R pressures , it drives right & feels right but then you have a totally different car totally different suspension , geometry & configuration .
The engine being at the rear so over the driven wheels & wheels themselves are 11j wide with 305 30 19 tyres as opposed to a 35is on 9j rims with 255 30 19 or 8.5j with 255 35 18 .

[flybobbie]

I run 38F and 40R 19 inch Goodyear asymmetrics.
Even wear across the tyres but the rear would skip if i went up to 44 and i have come down from 42 as the crown of the tyre was wearing more than the edge on the previous tyres so 42 was a touch too high.

[Lazza]

My 35i doesn’t have a rear engine...

After 15 years of playing with MX5s on the track, I have a fairly good feel for tyres and can feel the difference between feedback & harshness, which people very often confuse.

In summer when the roads are warm I have the rear pressure up to 40 but now the roads are cold and often wet I put it down to 38 to get more compliance & grip.

Definitely nothing wrong with my car. All tyres in good condition. Geo checked annually. Just serviced last Thu at a specialist. Feels great.

[Busterboo]

The three previous posts and some others in this thread obviously contain valuable experience and good sense. When push comes to shove, though, I have to follow the highest authority - the manufacturers. Fortunately, their figures work for me.

One reason they do, I believe, is that I'm on 18" wheels.