Tyre pressures for running 18's please

[JayB5UK]

Hi all, on behalf of me good mate AliA4, what's a decent pressure for 18's on a 96 1.8 saloon, we put 34 in the other week when he bought it, I know garage guages are a bit suspect, but this was a "digital" one but it feels rock hard now, is lowered and on 40's but I think it's got too much air in them now? Obviously inside the fuel flap is for standard 15's & 16's only.
Help.

 

[SteveS]

i run 30 all round in mine. 225/40/18 on rs6 reps.

 

[doeboy]

i was told about 33 when i had tyres changed in may.

 

[Randomjim]

32 front 30 rear ish

 

[mckay9uk]

i run 30 all round in mine. 225/40/18 on Millie miglia's, 35 mm lowered and uprated shocks/springs, i used to be a tyre fitter, i noticed that any more than 30/31 would make the tyres wear in the middle this indicates over inflation 30 gives a smoother ride as well, you must remember to up the pressure to 32 if you're running a full car, then put it back when back to normal.

 

[doeboy]

ah, ok sorted, i need to check mine tomorrow anyhow.

 

[JayB5UK]

cheers for all the replies. We checked again and after being driven they showed 31 at a different garage, so we left them as was.
Still feels a bit hard compared to mine but i'm only on 16's and what with my squidgy winter tyres and all..

 

[mckay9uk]

I have two pen tyre gauges, in my glove box i always check the garage inflator gauge reading against these, i have seen some garage gauges 5-7 out against my pen gauges, dont forget every tom, **** and harry are using the garage gauges, they're left out in all weathers and some have even been driven over !

 

[JayB5UK]

Yeah, but I only go to the local BP with a digital auto inflate type. Bet they are still crap too.
Lost my digital one I used to have under the seat of my motorbike, think I flogged it with it in there actually! Doh.

 

[ZeroK66]

I run 19's and I used to run about 32ish, till I realised it should be closer to 40. Since upping the pressures it has transformed the car. I would say run 36ish on 18's.

 

[JayB5UK]

Zero. I had thought they should be higher to be honest as when I had a 5 series a few years ago, I went from balloon profile 15's to 18's and the 15's ran 34 standard and the nearest comparison wasn an M5 with 18's, which they suggest 36 front & 38 rear I think it was.
It felt a lot better also.
My mate's A4, which sparked the question only had about 20 odd all round but now with 30 feels rock hard!

 

[mckay9uk]

I run 19's and I used to run about 32ish, till I realised it should be closer to 40. Since upping the pressures it has transformed the car. I would say run 36ish on 18's.

It's all down to personal preferance and how you drive, i would put the above pressures in if i was going on a track day, these pressures would be fine if you were doing a lot of hard cornering, as they will resist sidewall flexing, but for normal every day driving with a normal load you dont need much more than 30/32 the best way to check this is when the tyres need replacing i ran 34 in mine when i first had my 18"s the midlle of the tread wore out far more quickly than the edge's of the tyres, since i dropped the pressure's the wear is far more even, the ride is a lot smoother and there is more feel through the steering wheel, you have to think about the contact patch that the tyre has on the road, another thing to consider is in very bad weather lower tyre pressures have more traction than higher tyre pressures.

 

[hobbsy]

Tyre pressure is determined by the weight of the car not the profile of the tyre so unless anything else has changed (like using it on the track instead of the road or carrying 2 tons of sand in the boot) then keep the pressures standard.

 

[K7ERG]

30 all round here. 225/40/18