BMW's Question

[Barry Scott]

255/30/19.

Bridgestone Potenza Run Flats.

Why do you buy run flats? They add unsprung weight and reduce the handling. Surely as a car nut I'd have thought you'd be onto some lightweight tyres and alloys.

They say unsprung weight is equivalent to 6-10 times the amount of sprung weight. Reduce tyre weights by 2kg a corner, you then have a weight reduction in terms of feel, of up to 80kg or nearly like chucking a 13 stone passenger out.

[borgnan]

I completely agree, i always change the existing runflats on mine to regular rubber. Myself, like you won't be blessed with a spare, although i've not had an issue yet, i will just call the AA and get them to take the car to a tire shop and i'll simply replace it. Looking at your tire size i'm guessing you drive a 3 or 5 series m-sport with big wheels? If so you will be aware of the, how shall i say, very firm and jerky ride, changing to regulars drastically improves this in fact you almost wouldn't recognise it to drive. Not to mention improved handling at speed, although that does depend how keen a driver you are 

[Ralphy]

Because the car came with run flats from new, has a pressure indicator built in and no spare wheel !

The ride is fine and it handles fine. I don't chuck the car about anyway. Too nicer car and I'm 30 not 18.

[nochee]

Because the car came with run flats from new, has a pressure indicator built in and no spare wheel !

The ride is fine and it handles fine. I don't chuck the car about anyway. Too nicer car and I'm 30 not 18.

 

[borgnan]

Fair enough, mine is exactly the same in terms of sensors and no spare, It's personal preference i guess. I can just never resist offering an opinion about Bimmers. I'm also 30, however it sounds like i may be immature then 

[Barry Scott]

Sensors still work though don't they? (And I'm also immature!)

[borgnan]

Yeah they work exactly the same as they would on runflats, it's basically a little individual unit on each wheel, which i only know as i had to replace one on a previous car a few years back, not a cheap bit of kit either (£70 per sensor). It does exactly what it says on the tin though, it's set to the air pressure inside the tire and will alert you when there is a difference (of 5psi I think) from the set parameters.

[Ralphy]

Fitting non run flats will also invalidate your warranty. BMW are fussy about stuff like this.

I know a guy off a BMW forum who bought a brand new 335i Coupe. After 10k miles he changed all the tyres to non run flat Michelins. The car developed a problem with the tracking and was wearing the inside of the tyres very badly. BMW refused to fix under warranty because he'd not fitted BMW approved tyres.

[borgnan]

That is also very true, i do hate BM main dealers with a bit of a passion though. How a tire of the same exact size and probably make could cause a tracking problem is anyone's guess. I think this i where i differ as i don't worry about warranties, i don't buy cars any newer than 3 years old purely for the fact you get better value at that age. I do a lot of miles each year, so i only keep a car for 18 months max. If i had just spent some hard earned cash on a new one, i probably would have done the same as you.

[borgnan]

On a totally different note as there are some BM owners here, in anticipation of some snow this year i've ordered a pair of snow socks, purely to get me out of the village to the main road as in recent years i haven't even got close to getting up the drive. Has anyone tried them before?

[Ralphy]

On a totally different note as there are some BM owners here, in anticipation of some snow this year i've ordered a pair of snow socks, purely to get me out of the village to the main road as in recent years i haven't even got close to getting up the drive. Has anyone tried them before?

No. I walk everywhere when the snow comes down or use my dad's Ford Ranger !

Beemers are utterly useless in the snow. Mine has the worse possible combination, rear wheel drive + massive wide tyres + auto gearbox.

Snow socks might be better on a car with thinner tyres though.

[borgnan]

Snap, other than the walking bit as most of my clients are a bit too far for that. I've read some pretty positive stuff about them, although i'm not expecting much success, more of a £50 punt really. I'm not one of these people who soldier on through, which usually ends in an accident or getting stuck, but it does wind me up when people have been getting about for a few days after the weather has cleared and i still can't get my car up the drive.

[Samdy Gray]

Jeez, get a room you two.

[Ralphy]

The snow socks are meant to be good on front wheel drive cars. Certainly give more traction.

The problem in this country is most people don't use different tyres for summer and winter. In some European countries, you can be fined for driving with summer tyres during the winter months.

[suttonred]

BMW. Economical.

Please explain.

Mine does 80mpg motorways 69 mpg combined by the book. The motorway one is not far off that in reality, the combined is probably nearer 55. The only thing two things to think about with a bmw, are they are very undignified getting in and out of, and never ever erver drive one in the snow, bar that best car I've ever had.