Tire wear

NickXX · 4 Mar 2006 at 23:06

L0rdMike said:
Is it possible your wheels got swapped around?

Fronts put on the back?

Might explain your tyre wear on the fronts?

I don't think so, as the tires on the front would be wider than the ones on the back if they had been swapped which I assume would be wrong.

I guess the previous owner put the wrong profile tires on last time. Maybe it's normal though. I wish the BMW manual was some use, but it doesn't even mention the 18" wheels :rolleyes:

.

L0rdMike · 4 Mar 2006 at 23:07

NickXX said:
I don't think so, as the tires on the front would be wider than the ones on the back if they had been swapped which I assume would be wrong.

I guess the previous owner put the wrong profile tires on last time. Maybe it's normal though. I wish the BMW manual was some use, but it doesn't even mention the 18" wheels .

Ah yes I for got about that. Silly me.

Oracle · 5 Mar 2006 at 00:04

Umm, its not a lower profile! The rears are 255 WIDE whilst the front are only 225!

The 35 and 40 are a percentage of the width, and as the rears are horrifically wider than the fronts, the profile of the rears will be equal to if not larger than the fronts!

This is obvious............ blindingly obvious!

The 225 / 255 is the section width in mm. the 35/40 is the 'aspect ratio' in relation to the width! So for example you could have 285/30R18 on the rear, and the profile would still be larger than 225/40 fronts.

Aspect Ratio
Often referred to as the profile or series, the aspect ratio of a tyre is determined by dividing a tyre's section height by its section width when the tyre is inflated to its maximum recommended air pressure, mounted on the approved measuring rim, and under no loading

Nick, your rears do have a larger profile than the fronts. The fact that they are (what appears to be)5% different is just peoples lack of understanding. Your rears are wider, and the profile is a percentage. So you'll find the rear profile is bigger.

PS, yes it is right!

L0rdMike · 5 Mar 2006 at 00:17

Shows how much I know.

Oracle · 5 Mar 2006 at 00:21

^lol,

NickXX · 5 Mar 2006 at 00:23

Oracle said:
Umm, its not a lower profile! The rears are 255 WIDE whilst the front are only 225!

The 35 and 40 are a percentage of the width, and as the rears are horrifically wider than the fronts, the profile of the rears will be equal to if not larger than the fronts!

This is obvious............ blindingly obvious!

The 225 / 255 is the section width in mm. the 35/40 is the 'aspect ratio' in relation to the width! So for example you could have 285/30R18 on the rear, and the profile would still be larger than 225/40 fronts.

Aspect Ratio
Often referred to as the profile or series, the aspect ratio of a tyre is determined by dividing a tyre's section height by its section width when the tyre is inflated to its maximum recommended air pressure, mounted on the approved measuring rim, and under no loading

Nick, your rears do have a larger profile than the fronts. The fact that they are (what appears to be)5% different is just peoples lack of understanding. Your rears are wider, and the profile is a percentage. So you'll find the rear profile is bigger.

PS, yes it is right!

Brilliant - thanks for clearing that up mate!

Oracle · 5 Mar 2006 at 00:25

np, anytime! Nick, stick me in trust, I dont know everything about every car, but E46s (330d especially), well......anytime my friend.

Doonhamer · 5 Mar 2006 at 06:09

Oracle said:
Not on the front wheels of a rear wheel drive car it couldnt! That would be impressive!

erm...yea....erm....

*feels silly for not reading everything carefully.*

Joe T · 5 Mar 2006 at 09:52

8mm (basically brand new) on all of the tyres on my 330d I bought yesterday

TomO · 5 Mar 2006 at 11:05

225/40 and 255/35 are almost identical rolling radius. hence my original question and the fact that its a fairly standard combination due to the matched radius after allowing for width and aspect ratios.read me for lots of tyre info

caluclator for comparing widths/ aspect ratios about half way down.

NickXX · 5 Mar 2006 at 11:24

That's a great link - thanks Tom

Scania · 5 Mar 2006 at 11:57

L0rdMike said:
Is it normal to have a lower profile on the rear at all?

Strikes me as odd but I know little.

I've got 235/50/18 on my front, 255/45/18 on the rear. - I'd say its normal.

Those tyres, whilst being legal in terms of the law, imo, won't do you many favours should you hit some standing water, at speed & cornering...

Think about it mate, that rubber is what keeps you planted to the road, nothing else.

Just 'cos its legal to run a tyre down to the legal limit, in no way implys its safe, it isn't.

New tyres > Smashed up car / child / self.