Tyre pressure

moranor@axis

///Member
Official Advertiser
your rear tires will run hotter when pushing hard so the higher pressure will keep the cooler...

also if you inflate the front the same as the rear the dtc will intervene too soon because of the change in rotation speed caused by increasing the front tire pressure...
 

Philip Foglar

///Member
Interesting, mine which is also an Exclusive (non-sportpack) indicates tyre pressures for 225/40R18 and 255/30R18 to be as follows:

2.4 front and 2.8 rear (four occupants)
2.8 front and 3.2 rear (five occupants and/or luggage)

My personal advice, invest in a good quality portable mini air compressor and pressure gauge that is decently accurate - I never trust filling station pumps and gauges. Also a firm supporter of Nitrogen in the tyres to minimise moisture etc.

So I would say 2.2 all around is maybe a bit soft, for the rear in particular! Increase the pressures and see how it goes! Ride will of course firm up but at least then the handling will be more predictable and stable! :thumbs:
 

mo_s

Member
I got E90 same tyre sizes...for city driving its usually me +1 in car with no luggage..I put 2.2 on front and 2.5 on the back according to the dealer wen I bought the car..never had a prob :)...used same wit non run flats and never had a prob..the non run flats are michelin pilot sports 3's..awesome tires in my opinion.
 

Philip Foglar

///Member
The thing with RFT's is to make sure that the tyre pressures are always correct since you will not easily see if they are soft. Otherwise you will wear out the shoulders very quickly and of course stress the side-walls. My father in law firmly believes in pumping his tyres up to no more than 1.8 all around - for me this is way too low, and you can see that the tyres "look" soft, but works for him and his driving style.
 

P Smit

New member
Guys, listen to this. I have had a long and very interesting discussion with Steven Morris, racing driver from England now staying and working in SA, 2 weeks ago. He is currentlly with Audi Advanced driving, did development on the new 3-series in Europe, the Subaru Sti, and the current Audi range.

After he drove my M3, he said I am running too low preasures on my car, it was set at the minimum as suggested on the sticker in the doorframe. He says those preasures are the lowest safe and comfortable preasures to be used, but not the optimal preasures for great handling.

He suggested that I set the preasures at the highest suggested figure for the especially for a car like mine that is driven like it was designed for, for following reasons:
1. The tyres flex much less during cornering and more tread surface is kept on the road surface

2. The tyre respond better and quicker during cornering, intial "bite" and steering response is attained

3. If the tyres are set too soft, the shocks are not working optimally as with higher preasures, as the soft tyres soak up too much of the upward movement of the suspension instead of the shocks doing the work.

Do note though, you must distinguish between more sporty and performance orientated driving, and just normal calm driving. If the latter applies the the lower preasures will be fine and a tad more comfortable.

If you go to the track, then you must know what you are doing. I've done quite a lot of track racing and -driving with normal road cars off all sorts and makes and gained a lot of experience as such. You start off with lower preasure settings 'cause the tyres heat up a llot under track conditions. After a lap or two, the tyres are heated up as much as they would, they can easily jump up from let's say 2,0 Kpa to 3,2Kpa. You have to determine by what would be the optimum track preasure, which is the topic for a whole new thread, and then stick to that preasure for optimum laptimes.

The track use preasure will vary between about 2,6 and 3,0 Kpa, depending on the type of track and tyre used.

So, the priciple I want to highlight is that the optimum track use preasure will give you the best handling, steering response and suspension performance. So, if that preasure is used on normal roads, you will also have the same benefits,but due to the tyres not being heated up in the same manner as on the track, the initial preasure would not be influenced much during town road driving which means you can use the higher preasures from the outset..

So, before you want to know which tyre preasures to use, first detemine how you would like to drive the car. If harder tyres rather define sportiness and good handling for you in stead of uncumfortable ride quality, then you may rather go for the higher settings. Otherwise you stick with the mom's taxi mode preasures.
 

moranor@axis

///Member
Official Advertiser
very true P Smit but for most people the recommended temps will serve them well... for psychopaths like us they dont work so well :rollsmile:
 

Philip Foglar

///Member
Yes, very true indeed, but as already said, more suited for track conditions where the overall road surface is a lot smoother and consistent than typical public roads. Also since there are speed limits to contend with, makes little sense to have the tyre pressures that high - uncomfortable ride and ultimately just more wear and tear on suspension components. As least, this is how I see it.

Best is to find what "works" best for your particular car and tyres - many years ago when I was still a Corolla driver I experienced the effect of slightly softer tyres, especially on the rear since the car was a FWD. Basically, was very easy to loose the rear, even you not unloading the rear which is always going to upset a FWD. Front was also very sluggish. And this was at the then recommended 1.8 all around tyre pressures! After this I inflated all tyres to 2.2 and the car's handling was so much better and more predictable - actually was pretty impressive for a FWD in those days. Fair enough, we are talking a lighter and different type of car, and I didn't exactly have really low profile tyres.

But, this was where I learnt how crucial it is to find and maintain the optimum tyre pressures that works best for the car based on typical road conditions... :thumbs:
 
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