Tyre pressure

[mamilapon]

Im running 245/45/17's Khumo Ecsta's and im putting recomended pressure for 225/60/15's, That is 200kpa(front) and 240 kpa(rear). Is that good or bad?
Any suggestions?

[Podmore]

200 kpa (a bit less than 30 psi) is too low - you should be running about 36 - 38 psi (250 - 270 kpa) front and 34 - 36 rear, unless carrying a full load or travelling consistent high speed, then put your rears up to 38 - 40 psi. The ride may be a little harsher than you're used to but you'll lessen the risk of cutting your sidewalls or bending the rims on potholes and manhole covers and other crap you might manage to run over.

[Tiger]

I put in 34 PSI front and 37 PSI rear.

[bsell]

I run 40 psi front and 35 psi rear with 235/45/18 tires. I found that running the rears hard (like BMW recommends) is too much for me most of the time. I drive by myself 95% of the time, thus the rear end is very light compared to BMW's thinking.

When the snows are mounted (stock sizes) I keep the same five pound difference, biased to the front for the same reasons. The car handles better with similar tire roll rates.

Brian

[leicesterboy15]

I am running 17s and 18s and run 32 PSI all round, is that too low? I've never had uneven tread as a result of under - inflation

[bmwrp8]

I am running 17s and 18s and run 32 PSI all round, is that too low? I've never had uneven tread as a result of under - inflation

I run 30 all around

[Tiger]

I find that with equal all 4 pressure, the car is very reluctant to turn and rear seems to be pushing the front out of turn... Just try it... increase your rear by 4 psi and see how car responds on the same road you always drive.

It is not about the rear tire being too bouncy... it is about the handling the steering response.

[bmwrp8]

I find that with equal all 4 pressure, the car is very reluctant to turn and rear seems to be pushing the front out of turn... Just try it... increase your rear by 4 psi and see how car responds on the same road you always drive.

It is not about the rear tire being too bouncy... it is about the handling the steering response.

will try thanks for the input:D :)

[Ferret]

will try thanks for the input:D :)

I tried a 35 front 38 rear combo once, and wont ever do it again - It caught me out twice in one day, the rear end of the car sliding around a roundabout.

I now run it the other way around with 38 up front and 35 at the back. Too much PSI at the back causes the car to yeah, handle well, but when the grip starts to go you've had it. Hard rears on a RWD car is asking for trouble in my opinion...

[bmwrp8]

I tried a 35 front 38 rear combo once, and wont ever do it again - It caught me out twice in one day, the rear end of the car sliding around a roundabout.

I now run it the other way around with 38 up front and 35 at the back. Too much PSI at the back causes the car to yeah, handle well, but when the grip starts to go you've had it. Hard rears on a RWD car is asking for trouble in my opinion...

ill try that also:D :D

[leicesterboy15]

Its worth a try, asc is generally under worked anyway!

[bmwrp8]

Its worth a try, asc is generally under worked anyway!

true true:D

[attack eagle]

I tried a 35 front 38 rear combo once, and wont ever do it again - It caught me out twice in one day, the rear end of the car sliding around a roundabout.

I now run it the other way around with 38 up front and 35 at the back. Too much PSI at the back causes the car to yeah, handle well, but when the grip starts to go you've had it. Hard rears on a RWD car is asking for trouble in my opinion...
that's because you have more torque down low than us petrol guys.

I run about 35 front 40 rear also

[Tiger]

I bet your tires were bald too... or somewhere near that. Have you checked your sway bar links too? We ran as high as 39 front and 43 in rear and never experienced what you have...

Now as I was typing recalled once that our car never had the rear shocks changed and everytime my dad went around a good turn, his rear end always went out of control... Once we changed the rear shocks, no more problem. So I think this is why it happened on you.

[Rick L]

You should always use less pressure up front than the rear (like BMW recommends) for front engine cars. If not, it will create more understeer… Something that all 5 series suffers… I have 35 psi front and 38-39 psi rear. But all this is subjective and each to their own… Whatever fits your driving style... :)


I run 40 psi front and 35 psi rear with 235/45/18 tires. I found that running the rears hard (like BMW recommends) is too much for me most of the time. I drive by myself 95% of the time, thus the rear end is very light compared to BMW's thinking.

When the snows are mounted (stock sizes) I keep the same five pound difference, biased to the front for the same reasons. The car handles better with similar tire roll rates.

Brian

[Podmore]

Hmmm - my thinking is that even with a well-balanced car like the E34, there's a bit more weight in the front than the back, so apart from other considerations such as ride quality, to keep the size of the tyre contact patch pretty even between front & rears, it's necessary to have the front inflated a bit more than the rears. My experience is that LOW pressure in the fronts will cause more understeer than high pressure due to the sidewall flex which allows the tyre to roll more on the rim, thus lifting up the inside edge of the tread on cornering and reducing the contact patch, leading to reduced grip - just another 2 cents worth from me ....

[Rick L]

I'm not talking about low tire pressure that will create the complete roll here... But understandable where you're coming from... That's what I used to think but it is opposite... You can do a search and see for yourself. Tighter rear will bring the tail around...



Hmmm - my thinking is that even with a well-balanced car like the E34, there's a bit more weight in the front than the back, so apart from other considerations such as ride quality, to keep the size of the tyre contact patch pretty even between front & rears, it's necessary to have the front inflated a bit more than the rears. My experience is that LOW pressure in the fronts will cause more understeer than high pressure due to the sidewall flex which allows the tyre to roll more on the rim, thus lifting up the inside edge of the tread on cornering and reducing the contact patch, leading to reduced grip - just another 2 cents worth from me ....