Tyre sizes

Author
Discussion

x5x3

Original Poster:

2,424 posts

260 months

Friday 7th November 2003
quotequote all
a word of warning.

recently had to change my rear tires (24K so not too bad!).

Original tyres were Bridgestone, but none in the country, dilema was get other tyres or drive (illegally) on slicks.

So spoke to dealer and checked that Pirelli's would be ok - they said yes as same size/profile, etc.

Bit of a mistake as it turns out that although the Pirelli are also 235/55/R18 they are not the same!

What this means is that the electronics are easily confused - even at low speed! Had a major moment the other day in the wet, still not sure if it was the electronics or me that saved it.

According to the dealer - you need to have exactly the same brand of tyres all round - shame they didn't tell me that before I bought them!

rassi

2,480 posts

258 months

Saturday 8th November 2003
quotequote all
x5x3 said:


Bit of a mistake as it turns out that although the Pirelli are also 235/55/R18 they are not the same!


I think you mean 255/35/18? Otherwise they gave you the wrong size!

What car - E46 M3? Why would a different brand in the exact same size "trigger" the electronics or make the car less stable (to any noticeable degree)? Unless the Pirellis are crap, which they probably are not, or in the wrong size (which I think is a typo from your side)I don't understand why you had an incident that is tyre related.

Webdunk

194 posts

254 months

Monday 10th November 2003
quotequote all
I was guessing an X5 from the user name... in which case 235/55/R18 makes sense as does the car's bafflement if it's getting different tyre characteristics front / rear.

x5x3

Original Poster:

2,424 posts

260 months

Monday 10th November 2003
quotequote all
yes you are right - I cannot type.

It is an E46 330, now with Pirelli's on the back and Bridgestone on the front.

Dealer has confirmed that the sizes are different (although they both claim to be the same) and that it is confusing the ABS/DSC/CBC/etc.

m-five

11,440 posts

291 months

Tuesday 11th November 2003
quotequote all
If that's the case then the car would be unsafe to drive on any tyres due to the fact that the front and rear tyres will only be the same size if you put four new tyres on at a time.

If the new tyre has 8mm of tread and the older tyres have 2mm of tread left then the older tyres will be 12mm smaller than the new ones.

If you drove too hard as soon as the new tyes were put on then that would explain the skittishness of the car as the new tyres will have a sealing compound on them which will take 50-100miles to wear off - take it easy until then, or switch the electronics off and drive it with more care!

I have an M5 with no electronics and the back end only slips when I want it to!

mondeoman

11,430 posts

273 months

Wednesday 12th November 2003
quotequote all
'scuse me but thats a load of bullsh@t.

As long as you do have the right profile (330 will be 255/35R18 rear and 235/45R18 front IIRC), then different makes on different axles is not a problem and will NOT confuse the eleectronics. New tyres take a while to scrub in before working properly ....

You can even have different makes on the same axle, as long as the profile is the same - but that would lead to odd handling, as different tyres have different characteristics

x5x3

Original Poster:

2,424 posts

260 months

Thursday 13th November 2003
quotequote all
Interesting what you say mr mondeo,

if you are correct then I have a more serious problem?

anyone have any ideas?

I know about skittish by the way - used to have a TVR!