19" wheel / tyre issue

[M5 TT]

I specked my car with 19's for a few reasons. I like the M5 look and I hate road noise, lastly the 2.5k premium for the 20's was not worth it.

Anyway,

Got a HUGE tank slapper on last night while passing a few cars on a "A" road.

Nailed it, pulled out hit the white lines then the car started to swing from side to side ( wheels were not spinning), backed off a bit it steadied out, nailed it again then moved back to my side of the road and again crossing the white lines the car was just about uncontrollable.

Thinking this was a once off for some reason I found a quiet bit of road and tried it again, although still did it, it was miles better but the white lines were not so pronounced. Looks like the tyres struggle with new high, thick white lines.

I wonder if the higher tyres wall of the 19s are flexing under full throttle then when hitting white lines exaggerates the issue??

Not sure but not how a 70k car should perform.

My rear tyres are at 2.2 bar. Will up this a bit maybe they are just a fraction low?

I did read on here someone complained about his car feeling sloppy at the rear and was blaming his spacers ( I don't have spacers) wonder if its the same issue. Anyone else suffered from this ??

[JOHNBMWM5]

Originally Posted by M5 TT

I specked my car with 19's for a few reasons. I like the M5 look and I hate road noise, lastly the 2.5k premium for the 20's was not worth it.

Anyway,

Got a HUGE tank slapper on last night while passing a few cars on a "A" road.

Nailed it, pulled out hit the white lines then the car started to swing from side to side ( wheels were not spinning), backed off a bit it steadied out, nailed it again then moved back to my side of the road and again crossing the white lines the car was just about uncontrollable.

Thinking this was a once off for some reason I found a quiet bit of road and tried it again, although still did it, it was miles better but the white lines were not so pronounced. Looks like the tyres struggle with new high, thick white lines.

I wonder if the higher tyres wall of the 19s are flexing under full throttle then when hitting white lines exaggerates the issue??

Not sure but not how a 70k car should perform.

My rear tyres are at 2.2 bar. Will up this a bit maybe they are just a fraction low?

I did read on here someone complained about his car feeling sloppy at the rear and was blaming his spacers ( I don't have spacers) wonder if its the same issue. Anyone else suffered from this ??

I set mine to 36 PSI all round, pick it up Sunday.
If I load it up 36 front 38 rear fully loaded 36 front 40 rear.. Try it.
PS) i'm on 20" wheels.

[Netwon]

M5 TT I just took a quick check of Scotland weather (Glasgow) once you get below 15 deg C you need to start being careful when you walk on it from my personal experience. 7 deg C the stock Michelin PSS tyres are useless. I can break the back end loose at 100km/h easily and have to take care when changing lanes when it is < 15 deg C (worse if damp). Pull out to pass then apply power or things can get squirmy!

2.2 bar is a little light. A hair over 2.5 bar works good for me (36PSI)

Netwon

[M5 TT]

That's a big difference over mine. You are running 2.5 bar

My current pressures,

One rear tyre is at 2.2 bar. 31.9psi. Other rear is 2.3 bar. 33.3 psi

[Used2be]

Originally Posted by M5 TT

I wonder if the higher tyres wall of the 19s are flexing under full throttle then when hitting white lines exaggerates the issue??

I believe Newton has it right. I picked my car up in December and the daytime temps were low 40s to high 30s F, and the rear tires would slide with minimal throttle input, even without white lines. When it's warm they're great, but very slippery in the cold. I use 36 psi front and rear for the street. Oh, and I have the 19s also.

[JOHNBMWM5]

Winter tyres are the way to go, I have 20" wheels and Michelin PS4 alpines.
They are very sticky.

[Danmar]

I have noticed a similar but less pronounced problem. When I pull out to pass I often feel a lack of control when going over the centre line, a little disconcerting. Not a temperature issue. I have 20's. Maybe I should check the tire pressure.

[eddiedent]

FYI ,20" tire option is only $1300.00 MSRP.

[M5 TT]

Originally Posted by eddiedent

FYI ,20" tire option is only $1300.00 MSRP.

Yeah where u live maybe. UK is £2500 extra

[Netwon]

Originally Posted by Danmar

I have noticed a similar but less pronounced problem. When I pull out to pass I often feel a lack of control when going over the centre line, a little disconcerting. Not a temperature issue. I have 20's. Maybe I should check the tire pressure.

Unless it is a really hot day (35C+) and the road is dry of you walk on it while changing lanes you'll feel the center line. I guess that what 500 ft-lbs @ 1500 rpm gets you!

[M5 TT]

Originally Posted by Netwon

Unless it is a really hot day (35C+) and the road is dry of you walk on it while changing lanes you'll feel the center line. I guess that what 500 ft-lbs @ 1500 rpm gets you!

35c haha it's the uk that is never going to happen. You said Glasgow was 15c today that's our summer

My 535d had around 780nm around 570lbs ( crazy fast diesel) and never did anything like this.

I don't mind feeling the lane change but this was pretty extreme. Will try more pressure tonight and see how it goes.

[JOHNBMWM5]

Originally Posted by M5 TT

Yeah where u live maybe. UK is £2500 extra

I paid £2450 for these 20" wheels and Michelin PS4 Alpines.

[M5 TT]

I am looking for 20s at the moment and was going to use my 19s for winter tyres.

Struggling to find a 20" wheels that are a bit different to the norm.

[M5 TT]

Increased pressure to 36psi. It is better. I would describe it as squirmy now. It was down right dodgy at 32psi. Still not good though

[M5 TT]

The more I play the more I think it's the rear springs that are too soft. Wonder if the issue goes away with H&R spring or similar?

[JOHNBMWM5]

Originally Posted by M5 TT

The more I play the more I think it's the rear springs that are too soft. Wonder if the issue goes away with H&R spring or similar?

You say that but some who have tested the car leave the suspension settings at "Comfort" to aid in putting the power down

What setting are you driving hard on?.

[M5 TT]

I have tried all 3. The hardest setting reduces the squirm but that only makes the shocks harder and does nothing too the springs.

I think you are right. Soft setting in straight line will allow more transfer weight to the rear wheels but it seems when you add steering input it starts to move around.

I wonder in the fight to make this car comfortable ( which it is) they have gone for a slightly softer spring and upped the ARB diameter to stop body roll making it a bit sloppy under certain circumstances. i.e crossing the centre line on "A" roads. Never happens on the dual carriageway.

I guess it's because I nail it combined with quick steering input and crossings the centre line is enough to unsettle the car.