Tyre size advice/ABS needs to function

[senna]

Currently the 325 is on 205/55/15 tyres.
But since I have just taxed it for 12 months I have decided to change the tyres, lower it a bit and replace the bushes.

I think 205 is a bit excessive at the front and I was wondering what options would be good?

Eg: 195 front 205 rear

Or 195 front/rear

What profile should I use to allow the ABS to remain fictional

Thank you

[Blitz]

Just leave it alone. Theres a reason why BMW spec that size tyre.

[steve_k]

tyre size has nothing to do with the ABS, so whoever told you that was talking out their arse.

as for size, i used to run 205/50/15's all round & the speedo was only slightly out.

it's only mainly the speedo it might affect not ABS.

[bss325i]

Tyre size can effect the ABS if they have different rolling radiuses as the wheels will be rotating at different speeds and the sensors can trigger the ABS when braking.

More so on cars with ASC or DSC.

[Kos]

I would normally suggest 205/50 but as of recently (thanks to Audi) 205/55's are now again more plentiful in choice


Suspension wise H&R cup kit

But before you go spending money I may have someone interested in the car as it is

[senna]

Tyre size can effect the ABS if they have different rolling radiuses as the wheels will be rotating at different speeds and the sensors can trigger the ABS when braking.

More so on cars with ASC or DSC.

Totally correct.

Infact some puncture sensors work of this principle

[senna]

I would normally suggest 205/50 but as of recently (thanks to Audi) 205/55's are now again more plentiful in choice


Suspension wise H&R cup kit

But before you go spending money I may have someone interested in the car as it is

Thank you Kos,
I have decided to rest the M3 over Summer and use this. Hence I taxed it for 12 months.

But let me know if this chap is interested.
In the interim I would like to put a couple of tyres on as I think they last saw service a good few years ago
205/50 are excellent (had this on the iS)

[Blitz]

205/50 looks gash. Got to be 55 profile.

[senna]

What about 195/50/15?

I think visually identical from the side.
Less rolling resistance

[Grrrmachine]

195/50 looks way too small in the arches. Hated them on mine.

[senna]

Ok
205/55/15 it is then

[Demlotcrew]

tyre size has nothing to do with the ABS, so whoever told you that was talking out their arse.

as for size, i used to run 205/50/15's all round & the speedo was only slightly out.

it's only mainly the speedo it might affect not ABS.

Tyre OD has a massive impact on modern ABS regulation, in fact so does speed as all new ABS/DSC systems have compensation tables for tyre expansion at higher speeds.

The very latest generations have tyre compensation/trim adjustments sent from the main engine ecu over CAN.

For the E30 ABS, as long as the front and rear tyres are both the same size you wont have any issues as the system is so primitive!

[HairyScreech]

tyre size has nothing to do with the ABS, so whoever told you that was talking out their arse.

as for size, i used to run 205/50/15's all round & the speedo was only slightly out.

it's only mainly the speedo it might affect not ABS.

Tyre OD has a massive impact on modern ABS regulation, in fact so does speed as all new ABS/DSC systems have compensation tables for tyre expansion at higher speeds.

The very latest generations have tyre compensation/trim adjustments sent from the main engine ecu over CAN.

For the E30 ABS, as long as the front and rear tyres are both the same size you wont have any issues as the system is so primitive!

He's right you know.

ABS/traction control/tyre deflation monitoring can be a real pain swapping wheels about on newer cars.

[Demlotcrew]

With new BMW's you can simply code a new wheel option to the Chassis and it will automatically send the correct 'Bit' for the wheel choice to the ABS ECU.

But OD is only a fraction of whats needed for ultimate ABS function.

[maxfield]

I've got a mate who works at Citroen, had a new C5 I believe. Had random ABS faults and also wouldn't go into sixth gear on the autobox. That's because the owner put unbranded tyres on, re fitted michelins and it worked fine.

[senna]

I've got a mate who works at Citroen, had a new C5 I believe. Had random ABS faults and also wouldn't go into sixth gear on the autobox. That's because the owner put unbranded tyres on, re fitted michelins and it worked fine.

I am also aware of a friend with a Mercedes 4x4 ML that activated it's warning lights whilst driving on a space saver

Even the E30 will light up its warning light if for example one tyre is 15psi

[Demlotcrew]

Even the E30 will light up its warning light if for example one tyre is 15psi

Above 70mph it would yes.