Anyone got a technical explanation for this?

[Abo Bob]

A little while ago I was punting around a corner I know very well. Sometimes, when I'm feeling frisky, I hit it hard in 1st (tiptronic) and can get a smooth drift til traction catches up with me. This was with 235/45ZR17 tyres.

Now tonight was different because it was the first time I'd hit that corner since I got the 225/40ZR18 tyres on.

I had actually decided to go quickly but within traction around the corner and changed into 2nd gear before I got to the apex so I was barely on boost but with next to no warning the back let go in the same fashion as it would have if I'd meant to drift it. I didn't lose it, just grabbed it back the way I usually would but I was surprised.

Now my question is; Is it just my imagination or do lower profile tyres by their nature give less warning at the limit of traction or is it possible that the width was an issue?

As a side; Can anyone translate the full codes I posted above?

PS. I felt the slide was smoother with these tyres.

[Milo]

um well you have 10 mm less tire on the road if i read it right.

[Abo Bob]

What I'm trying to ask is about the feel you get from the tyres that they are about to let go.

[crooser]

that "feel" you talk about could just be the wall of the tyre flexing.

hence, you notice this less now with the even lower profile you have changed to.

you obviously knew the old tyres intimately well... sounds like you've been having fun anyway

[Al]

235/45/R17:

235=tyre width in mm;

45=thickness of sideway as a % of the trye width (ie: 45% of the tyre width.);

R17=17" tyre, Radials.

Yes a smaller profile tyre will have less flex and be more responsive. Having less width will also have less traction. Different Brands/models will have different road holding characteristics, due to the different compounds. Finally whether and foreign residue on the road will also play a major part on road handling.

[Jay95R33]

It also depends on the compound of the tyre.

Being different brand (I presume) they will handle differently.

Some tyres give you heaps of warning before they let go, some stick really well right to the end and then let go really fast.

J

[Duncan]

OK Sarpi, last 1 first.

225/40ZR18 means a tyre 225mm across the tread, 40 means the height of the tyre from the rim to the tread is 40% of 225mm (=90mm in this case). Z is the speed rating (= lots, not sure exactly but over 230), R is radial (they all are these days) and 18 is the size of the rim they fit on.

So the main thing about your new tyres is they are 1 cm narrower and on 1inch bigger rims.

As for "feel"....

firstly, are they the same brand and type of tyres? that's the main factor, there is a huge range in feel when tyres let go....generally the worse the tyres the more warning you get...with top ® tyres they basically stick like mad until they very suddenly let go.

If they are the same type of tyres you might be noticing the difference in sidewall height....but both 17s and 18s are big wheels which will have minimal sidewall flex.

Also make sure your tyre pressures are right for the tyres, normally up to 45 hot is about right.

[blind_elk]

Being a lower profile tyre, the sidewall is narrower. Therefore there is less flex available in the sidewall to absorb distortions. The tyre presumably puts a smaller footprint on the road. So the limit of adhesion (forwards + sideways) is going to be different (presumably less) with the 225/40ZR18 than with the 235/45ZR17.

[Abo Bob]

Cool, thanks guys.

And for everyones info. they are exactly the same brand and model, barring the obvious difference in size.

[GTRgeoff]

If it is a little bumpy, you will find that there will be a tendency toward 'sudden' traction loss on hard cornering due to the reduced sidewall flex.

This is why I went from 235 30 ZR17 to 255 40 ZR17 for daily driving

[Al]

Also if the tyres where only a few km's old, they may still have the silicon film on them, too make them look shinny. This will wear off after a few trips, but may have caused less traction.