E90 Tyre pressure monitor - and winter wheels/tyres

[RicksAlfas]

Does anyone know how the tyre pressure monitor works on the E90? Is it a sensor inside the wheels? The valves? Magic?

What I'm concerned about is that I've bought some old E90 16" alloys to use with my winter tyres and I'm not sure what will happen to the tyre pressure monitor.

Any words of reassurance would be appreciated!

[phumy]

There are no sensors inside the tyres, it works on differential speed calculated from the ABS sensors. So if you get a lower pressure in one tyre, the rolling circumference is different, then it will trigger an alarm....easy

[RicksAlfas]

I see. Simple! Thanks for your quick reply.

[Gaygle]

phumy said:

There are no sensors inside the tyres, it works on differential speed calculated from the ABS sensors. So if you get a lower pressure in one tyre, the rolling circumference is different, then it will trigger an alarm....easy

Are you sure about this? In my E46 rims there are actual sensors that are screwed into the rim with a special hollow screw. I know this because when i last had my tyres changed, they accidentally broke off the screw holding the sensor in and had to order some screws from BMW to reattach my tyre pressure sensor. And on my E46, it isn't true that it is done by the rolling radius at all - i've had low and flat tyres flash up on my dash the moment i've turned the key, before i've even put it in gear.

Maybe it's different on the E9x, but i can't see why it would be?

This is what it looked like, but was orange and had BMW written on it and was screwed to the inside of the valve IIRC.

Edited by Gaygle on Tuesday 11th October 14:12

[phumy]

Gaygle said:

Are you sure about this? In my E46 rims there are actual sensors that are screwed into the rim with a special hollow screw. I know this because when i last had my tyres changed, they accidentally broke off the screw holding the sensor in and had to order some screws from BMW to reattach my tyre pressure sensor. And on my E46, it isn't true that it is done by the rolling radius at all - i've had low and flat tyres flash up on my dash the moment i've turned the key, before i've even put it in gear.

Maybe it's different on the E9x, but i can't see why it would be?

This is what it looked like, but was orange and had BMW written on it and was screwed to the inside of the valve IIRC.

Edited by Gaygle on Tuesday 11th October 14:12

Sure.

[monthefish]

RicksAlfas said:

I've bought some old E90 16" alloys to use with my winter tyres

Will 16" wheels fit an E90 M-Sport coupe? What sizes of wheels can they accept? (I've seen them on 18"s and 19"s)

I'm assuming the brake discs aren't any bigger on M-Sport spec cars - can anyone confirm?

[RicksAlfas]

Not sure to be honest. If you look at the sticker on the door shut it will tell you the recommended size for winter tyres.
Mine's on 16s anyway.

[RicksAlfas]

phumy said:

There are no sensors inside the tyres, it works on differential speed calculated from the ABS sensors. So if you get a lower pressure in one tyre, the rolling circumference is different, then it will trigger an alarm....easy

Just to confirm this is indeed correct and there are no sensors on the inside of the wheels.

[martin mrt]

monthefish said:

RicksAlfas said:

I've bought some old E90 16" alloys to use with my winter tyres

Will 16" wheels fit an E90 M-Sport coupe? What sizes of wheels can they accept? (I've seen them on 18"s and 19"s)

I'm assuming the brake discs aren't any bigger on M-Sport spec cars - can anyone confirm?

16" wheels will fit all models below 325

[SBN]

yep anything with a 3.0 needs 17's minimum... which is annoying when it comes to winter tyres.

[nicklonguk]

SBN said:

yep anything with a 3.0 needs 17's minimum... which is annoying when it comes to winter tyres.

I've just gone through this, and spent considerable amounts of time trying to find out what wheels do and don't fit.

The 335i (and the other 3.0l models I believe) all have much larger discs and calipers at the front, and so you need at least 17" wheels. However, NOT ALL 17" wheels will fit - the inner diameter and clearance to the caliper is critical.

I ordered a set of aftermarket 17" alloys after getting conflicting responses from wheel retailers, online forums and the manufacturer themselves - in the end I saw a photo of the wheels I was after (Rial Como) on a 335i on E90post.com and took a punt from there.

What I wasn't expecting was the huge improvement in ride quality - not sure if it is the smaller diameter or the non-RFTs, but I suspect the later has the biggest impact. The wheels still fill the wheel arches well too.