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[ss134]

I'm sure most forum members check their tyre pressure on a regular basis but i would just like to share a quick experience. My car went in for a new
front tyre and alloy wheel (puncture which also resulted in rim damage) and i instructed the dealership to ensure that the car was aligned and the new wheel balanced etc etc....i also told them to ensure all tyres were inflated to 2.4 bar (CS3 E90 recommended pressures for less than 3 people in car).

I picked up the car and headed for the autobahn - the car felt strange, lane changes at speed did not feel as controlled as normal, the steering felt lighter and less communicative and the on/off ramps had to be taken slower than usual as the 'planted' mid corner feeling wasnt there. I owned another E90 m3 before this one so i have had plenty of seat time in these cars.

I drove home and started to think that the dealership had messed up the alignment or possibly the handling differences were down to the new tyre being not scrubbed in or different tread depth to the other 3 tyres (although my car is only 4 weeks old so my other tyres had done less than 1400 miles)
I drove the car for a few more days and decided that the reason could be that the temperature this week has plumeted - the road surface is colder and the CS3 are a summer tyre, makes sense that it will grip less and provide less feedback in colder temperatures.

After leaving specific instruction with the dealer to inflate the new tyre to 2.4 bar and check the others (he even wrote it on the work schedule and told me it had been done) i didnt even consider tyre pressures, surely a BMW garage can inflate 4 tyres to 2.4 bar.................wrong. Maybe their compressor was not calibrated but the result was that when cold all four tyres were inflated to over 2.5 bar. Once i had deflated the tyres down to 2.4 the car felt perfect again. I have my own tyre pressure gauge which i keep in the glovebox - garages and petrol stations are notorious for having
compressors which are not calibrated/read incorrectly.

Couldn't believe the difference -0.1 - 0.2 bar made to the feel of the car - especially at moderate/high speeds.

Check your pressures

My pressure gauge if youre interested: http://www.amazon.co.uk/gp/product/i...1&s=automotive

[stega]

Just an FYI digital gauges such as yours are notoriously wrong... I learned this the hard way after spending $40 on a nice digital guage.

Do yourself a favor and buy a cheap mechanical one.

[ss134]

Originally Posted by stega

Just an FYI digital gauges such as yours are notoriously wrong... I learned this the hard way after spending $40 on a nice digital guage.

Do yourself a favor and buy a cheap mechanical one.

Thanks for the words of wisdom but i did some research before i bought it. This guage was reviewed in a UK motoring magazine a couple of years ago in a group test and it was proven to be very accurate under test conditions. In fact quite a few of the digital guages beat the mechanical ones. Nowadays a decent digital guage is just as accurate (or more so)than an analogue guage....looks like you just bought a poor one.

[stega]

I had the digital craftsman guage. Not crappy by any means... I would grab a mechanical from a friend and compare readings. That is how I learned of the problem. I was several psi off of the 3 mechanical's I tested.

You may be correct and your gauge is just fine. But you never know, just looking out for ya.

[ss134]

Originally Posted by stega

I had the digital craftsman guage. Not crappy by any means... I would grab a mechanical from a friend and compare readings. That is how I learned of the problem. I was several psi off of the 3 mechanical's I tested.

You may be correct and your gauge is just fine. But you never know, just looking out for ya.

No problem mate

[GewoW]

ps 1 bar of pressure ~ 15 psi which is a MASSIVE difference. no wonder you felt it.

i'd be worried if you didnt

[ss134]

Originally Posted by GewoW

ps 1 bar of pressure ~ 15 psi which is a MASSIVE difference. no wonder you felt it.

i'd be worried if you didnt

The tyres werent inflated 1 bar too high- it was a typo (fixed)!!! The tyres from the garage were between 2.5 and 2.6 bar so were a maximum of 0.2 bar over - so 2- 3psi - thats why i was so surprised at the difference 2-3 psi over inflation can make.

[kmarei]

I can notice a difference of 2 psi on my M3
I've tried f30/r32psi, too soft
32/34 was perfect
34/36 was too hard
Not sure if it's the car or the PS2s that are that sensitive

[ss134]

Originally Posted by kmarei

I can notice a difference of 2 psi on my M3
I've tried f30/r32psi, too soft
32/34 was perfect
34/36 was too hard
Not sure if it's the car or the PS2s that are that sensitive

I think it must be the car - i have Conti's on mine and its the same.

[jonasaurus]

I was looking at the door jam and the recommendation is 2.4 bar all round for light load and 2.7 / 2.9 for heavy load. On that basis that's a range of 34.8psi to 39/42 psi (based on 18s with load rating of 93 F 97 R and max speed rating Y).

[GewoW]

im at 33 all around. get to 39/40 on the track when hot so it's perfect

[bigjae1976]

Yup, I can definitely tell the difference between a couple of PSI.

[ObviousMan]

I use 38 psi for autocross. At 40 psi, it gets a little too tail happy. 35 psi is about right for regular street driving on the stock PS 2's.

[mdoughty]

i love the feel of the car at 33 or 34 psi, but it wears out the outer tread of the rear tires very quickly on cs3s. anyone else noticed the uneven tire wear at these lower pressures?

[THE TECH]

Anyone running nitrogen instead? Should alleviate some issues.

[raiste]

Originally Posted by mdoughty

i love the feel of the car at 33 or 34 psi, but it wears out the outer tread of the rear tires very quickly on cs3s. anyone else noticed the uneven tire wear at these lower pressures?

The recommended pressure for the rears is 35. So 33-34 would be a little low.
But to answer your question, I found that at even 35 psi, the tires wear a little faster on the outside of the treads (CS3). I have bumped mine up 2psi all around. The ride is a little stiffer, but the treadwear is even, for me at least.

[ChrisK]

I run 36psi in the front and 35psi in the rear.

[Ateam]

So what is the concencus on 19 inch OEM tires?

I run 36 rear and 34 fronts. Any problem with this?

[ChrisK]

Originally Posted by Ateam

So what is the concencus on 19 inch OEM tires?

I run 36 rear and 34 fronts. Any problem with this?

I personally wouldn't run less than BMW suggests.

[cole328]

I have the Pilot sports on OEM 19's M3 Vert I run 35F 38R car handles great and tires seem to be wearing just fine as with the OP, maybe I am overly anal, but I can def feel a difference in handling if one of the tires is off 1-2 lbs so, every sun am, I check all four with the same gauge and adjst as necessary

[yusammyyu]

19'' rim , ps2 tires, what psi do you recommand if go track?