[iks-10]

Hi everyone. I have a 435i (rear wheel drive).
I'm going to change my tyres from the standard potenza S001 RFT to Michelin Pilot Sport 4s (non-RFT).
I also am going to go for wider front tyres to 245/35/19 (from standard 225/40/19), to increase front grip and reduce understeer. I'm going by what I've read on this forum.
I have two questions:
Any disadvantages to this?
What tyre pressures would be appropriate for this.
I have the 442m alloys.

The rears will also be changed to MPS4s but with the original size of 255/35/19.

Thanks

[jbiswurm]

Originally Posted by iks-10

Hi everyone. I have a 435i (rear wheel drive).
I'm going to change my tyres from the standard potenza S001 RFT to Michelin Pilot Sport 4s (non-RFT).
I also am going to go for wider front tyres to 245/35/19 (from standard 225/40/19), to increase front grip and reduce understeer. I'm going by what I've read on this forum.
I have two questions:
Any disadvantages to this?
What tyre pressures would be appropriate for this.

The rears will also be changed to MPS4s but with the original size of 255/35/19.

Thanks

Several folks including me have made this change with good results.

Primary downside is slightly higher price of the wider tire. Secondary would in theory be a slightly mushier turn in feeling because the wider tire on a thinner rim, but i havent found this to be noticeable.

Do it. You wont regret.

For pressures, should be roughly the same as stock. Maybe boost them 2-3 psi, see how it feels to you, and adjust from there.

[BBri89]

Just changing to MPS4S will make a big difference already

[Tengocity]

Only downsides will be slightly lower fuel consumption as the wider tyre will have more rolling resistance and ever so slightly more drag as it will disrupt the airflow around the front wheel arch area more. But it's marginal, and probs no worse than spacers for example. Also, perhaps a bit more tendency to follow ruts and cambers.

Well worth it I expect though, and something I'm planning to do come time to change, though maybe just to 235s. I'll go 265 on the rears too, which is what the Alpinas run.

[Mick.86uk]

Going from RFT to non RFT MPS4S will be the biggest difference in terms of ride comfort regardless of width.

Huge improvement when I did the change.

I've found the 245 35 19 MPS4S on the front to be more stable in higher speed corners and less outer shoulder wear. Only downside was slightly less nimble in low speed corners.

[Watsey]

I've been running 235/40 and 265/35 (12mm spacers all round) for ~20K miles and found that additional negative camber is also essential to reduce understeer.

There are several ways of achieving this.

245 fronts should be ok unless you lower the car significantly.

[M140_BCS]

I run 255/35/19 on BBS 8.5J front rims with zero tyre contact.

Lowered on eibach pro springs around 20mm drop at the front.

[iks-10]

Awesome. Thanks everyone for the advice.
Also, since the rolling radius of the fronts will be different to the originals, do we anticipate any problems there. I know the Speedo will be slightly off (slightly overestimating my speed). Any issues with the TPMS?

[Watsey]

The rolling circumference will only be ~1.1% difference compared to the 225/40, and will be around 0.8% of the rolling circumference of the 255/35.

In terms of speedometer readings and also the DSC the 245/35 should be fine.

[Alscoob]

Originally Posted by Watsey

I've been running 235/40 and 265/35 (12mm spacers all round) for ~20K miles and found that additional negative camber is also essential to reduce understeer.

There are several ways of achieving this.

245 fronts should be ok unless you lower the car significantly.

I tried 235x40 on the front of my previous F31 330d with 12mm spacers and they rubbed on the wheel arch liner at the front especially with the suspension working and on slight left / right hand curves, but it was on standard suspension.

[Watsey]

Originally Posted by Alscoob

I tried 235x40 on the front of my previous F31 330d with 12mm spacers and they rubbed on the wheel arch liner at the front especially with the suspension working and on slight left / right hand curves, but it was on standard suspension.

Standard suspension will certainly allow the body to roll more than if the car is running a stiffer aftermarket setup, and the tyres could rub especially on a bumpy road.

Prior to running more negative camber there were times when my front tyres would brush against the wheel arch liner. The arch liners on the F3X are not a smooth and consistent surface - there's a protruding 'wedge' at around 2 o'clock (looking at the right hand wheel) , but it's not going to damage the tyre if there's some contact.

It's not been a problem since my car has been running additional negative camber, as the tyres are a little more tucked into the arches at the top.