Tyre Pressures - 135

[ExREX]

What tyre pressures do people run - front and rear. I have a 135 on standard Dunlop 18" runflats.

Thanks
Greg

[Bimmerle]

I have a 125i M-Pack with 18" Bridgestone RFT's. I was recommended 40psi all round by the delivery sales guy (who was a BMW mechanic prior to transferring to sales). I check and adjust once per week in my garage first thing in the morning before driving off (cool tyres). Only 6500km at present, so a bit too soon to see how even is the wear.

[BMW86]

I'm running 36F and 38R or I run 36 on all 4.

[Dackelone]

I run these with my winter 17's setup: 205's all around on seven inch wide rims:

In metric = 2.3 bar (34.5 psi) up front, 2.6 bar (39 psi) in the rear

[Bimmerle]

I was told that on low profile, wide rims you need to run a higher pressure to obtain a flat tread in contact with the road across the wheel. Too low, and you get wear on the edges as the middle tends to buckle in. Too high, and the middle wears at the expense of the edges.

40 psi = 276kPa. I used to run about the same pressure on 18" 245's on my RX-8, and wear across the tread was very even.

[Dackelone]

That's how I got them from my BMW dealer/zentrum. I tried pumping up the tires to 2.6 and 2.9 bar, but that made the car ride really ROUGH! I couldn't stand it more then 40 kms that way. So back I went to what my dealer set the pressures too.

It might have something to do with my winter tires. They are run flats, but they have no STAR on the sidewalls. The star denotes that the tires are tuned for bmw suspensions. My dealer told me since I bought the tires late in the winter season, they had sold out of the OE tires.

For the two days I drove with my 18 summers on(in the winter) I thought they rode softer than my winter setup. I might try messing with the summer pressures ONCE summer or spring gets here! Until then I am sticking with my 2.3 and 2.6 bar setup.

[sparoz]

I have non-RFT, but they are on 38F, 36R. I have been driving my wife's 125 for the past few days, and she's on 38 all round with RFT and it's rough enough

[banglemangle]

38 psi all round (I read somewhere that fronts should be +2 due to fractionally more weight than the backs - could be a vortex myth!)

[x5mad]

I am currently runnning the minimum recommended pressures for the 215/245 18" wheels. Feels hard as a rock and every bump, expansion joint and dip is painful on the spine. I used to run 36 all round and this felt fine. I just wanted to experiment, will be dropping pressures back to 36 again.

Interestingly, I found that there was no added benefit in terms of handling neither was the steering any lighter. Just a much noisier and harsher ride.

[Luvmybmw]

Originally Posted by BMW86

I'm running 36F and 38R or I run 36 on all 4.

+1

[Dackelone]

Originally Posted by x5mad

I am currently runnning the minimum recommended pressures for the 215/245 18" wheels. Feels hard as a rock and every bump, expansion joint and dip is painful on the spine. I used to run 36 all round and this felt fine. I just wanted to experiment, will be dropping pressures back to 36 again.

Interestingly, I found that there was no added benefit in terms of handling neither was the steering any lighter. Just a much noisier and harsher ride.

EXACTLY! Thats why I dropped my tire pressures too. I could not belive how hard the car rode with the recomended pressure of near 40 psi. I'll trade off some tire life for a better ride. (I use 34.5 psi & 39 psi rear: 2.3 & 2.6 bar)

Perhaps this is why Runflats have gotten a bad reputation - running what bmw says to set the pressures too. ??? I also think we are on the 3rd or 4th gen of runflat tirs now - and they have tuned the tires better to the suspensions and real world conditions.

This is my first car with run flats, and I was really expecting an awlful ride. But I think the ride is quite good for a sports car/GT. Maybe thats bc I drive on Ultra smooth German roads where they actually spend money to keep the roads in good condition!!! Potholes? What are those? I have to drive to Italy or Czech to see what a pot-hole looks like!

[kevwrx]

Sarah's 135 convert, I run 40 psi all round
Our Prado 40psi all round
Our Mini's 45psi all round
Our Yaris 100psi in the right hand side tyres and 25 in the left hand side tyres

[05C4R]

the large difference in tyre pressure seems to be affecting the performance of your Yaris

[Brissie]

Originally Posted by beemer

the large difference in tyre pressure seems to be affecting the performance of your Yaris

I run 36 all round. Tried 38 and it was too hard. 36 is Ok as far as ride comfort goes.

[Bimmerle]

Originally Posted by Dackelone

EXACTLY! Thats why I dropped my tire pressures too. I could not belive how hard the car rode with the recomended pressure of near 40 psi. I'll trade off some tire life for a better ride. (I use 34.5 psi & 39 psi rear: 2.3 & 2.6 bar)

Perhaps this is why Runflats have gotten a bad reputation - running what bmw says to set the pressures too. ??? I also think we are on the 3rd or 4th gen of runflat tirs now - and they have tuned the tires better to the suspensions and real world conditions.

This is my first car with run flats, and I was really expecting an awlful ride. But I think the ride is quite good for a sports car/GT. Maybe thats bc I drive on Ultra smooth German roads where they actually spend money to keep the roads in good condition!!! Potholes? What are those? I have to drive to Italy or Czech to see what a pot-hole looks like!

I note that you are running on 17" with 7" rims. Narrower tyres shouldn't use as high pressures as on wider, low profile tyres. I came out of an RX-8 running non-RFT's (245 Toyo Proxes - great tyres) at the dealer-recomended 40psi. I would have to say the ride on my 125i M-Pack is pretty much the same, if not better. Let's face it - these are sporting-type cars after all. There are plenty of slush-mobiles out there which will give that pillow soft, wallowing ride if that's what people want.

I find the ride very comfortable and compliant. Unlike nice German roads, the goat tracks that the Queensland government laughingly calls roads are full of pot holes, especially after the recent rains. My car seems to cope with the local conditions very well.

I come back to the point - the correct tyre pressure is that which gives you even wear across the entire tread. It's pretty easy to do: just take a match stick or piece of card, and mark the tread depth at the sides and in the middle. Do this every few thousand km. If it's deeper in the middle, increase the pressure. If it's deeper at the sides, decrease the pressure.

[oz125]

[QUOTE=Bimmerle;6872368]I note that you are running on 17" with 7" rims. Narrower tyres shouldn't use as high pressures as on wider, low profile tyres. I came out of an RX-8 running non-RFT's (245 Toyo Proxes - great tyres) at the dealer-recomended 40psi. I would have to say the ride on my 125i M-Pack is pretty much the same, if not better. Let's face it - these are sporting-type cars after all. There are plenty of slush-mobiles out there which will give that pillow soft, wallowing ride if that's what people want.

Bimmerle, thanks for your perspective.
A bit freaky actually, I also have just traded the RX-8, with Toyo's, for a 125 M sport vert with 18",s. After reading some of the threads, I had feared the Msport , 18's and RFT's may have all spelt a bad combo ride wise.
Maybe thats why the dealer demo hack had stock suspension,and std 17's.
Few more weeks to go and I 'll find out for myself i suppose.

[Dackelone]

yes, I have 17x7j wheels around around with 205/55HR17s. I am running the bmw winter tire package sold thru the dealers. (I use 34.5 psi & 39 psi rear: 2.3 & 2.6 bar)with this tire wheel combo.

Next month(or when ever the snow melts away!) when I switch over to my summer
18's - I will see what feels best to me. Yes, I am mindfull of over & under tire inflation. I will start off with the tire inflation that is on the driver's door jam - and adjust from there. thanks.

[Bimmerle]

[QUOTE=oz125;6873276]

Originally Posted by Bimmerle

After reading some of the threads, I had feared the Msport , 18's and RFT's may have all spelt a bad combo ride wise.
Maybe thats why the dealer demo hack had stock suspension,and std 17's.
Few more weeks to go and I 'll find out for myself i suppose.

Yeah, I was a bit worried when I ordered mine, too. I'll be interested to hear what you think, but my opinion for what it's worth is that this car has a great ride. It's firm, but no firmer than the RX8, and just as compliant without perhaps quite so much body roll. Turn in is great, and the thing sticks like glue.

It is a good touring car. We took it on a shakedown cruise from Brissie to the Hunter Valley after we bought it, and enjoyed every km. We're now looking forward to visiting my daughter down in Bowral after Easter. T

[oz125]

plus it might be fun getting it to rev to 11K like the Rx

[sparoz]

Originally Posted by Dackelone

EXACTLY! Thats why I dropped my tire pressures too. I could not belive how hard the car rode with the recomended pressure of near 40 psi. I'll trade off some tire life for a better ride. (I use 34.5 psi & 39 psi rear: 2.3 & 2.6 bar)

Perhaps this is why Runflats have gotten a bad reputation - running what bmw says to set the pressures too. ??? I also think we are on the 3rd or 4th gen of runflat tirs now - and they have tuned the tires better to the suspensions and real world conditions.

This is my first car with run flats, and I was really expecting an awlful ride. But I think the ride is quite good for a sports car/GT. Maybe thats bc I drive on Ultra smooth German roads where they actually spend money to keep the roads in good condition!!! Potholes? What are those? I have to drive to Italy or Czech to see what a pot-hole looks like!

They have soften the suspension for the 1 coupe to make the ride better. Ie, all the body roll found in the 1er coupe which isn't present in the hatch and the 3ers.