Tyre Width...

[RobBentley]

Hi All.

I've been asked by the place that I want to get my RS6 replica alloys from... do I want 225/40/18 or 235/40/18 tyres...

Presuming these are the same rims.. I had no idea you could fit a wider tyre on the same rim?

Am I correct in thinking this protects the rim a bit from kerbs? Our FreeLander Sport runs 235/50/18 and I notice the tyre seems offer some protection to the rim by bulging out either side a little?

Presuming I am barking up the correct tree - what are the benefits or downsides of me choosing 225 or 235 ?


Cheers,

 

[HDi fun]

Don't rely upon sidewalls to protect the rims. The sidewalls, if damaged, can cause the tyre to deflate suddenly (blowout) and create a critical situation. Some tyres have rim protectors (Bridgestone RE-720s I mentioned a few days ago do have these). They're not perfect and the best thing is to not hit kerbs at all.

All rims can accept a range of tyres. Do not fit an over-wide tyre as you'll cause it to be stressed constantly and therefore it will overheat. All tyres come with a rim width range specified. Even modest 195s can got on anything from about 5" to 7.5", for example.

 

[thexav]

It does mean more grip though and its not much wider. Look at the cost of replacing them cos I bet there is a big difference in price.

 

[RobBentley]

Think i'll stick with the 225's and save myself some cash then as the car is far from short of grip.

 

[HDi fun]

An extra 10mm isn't going to add anything in terms of grip. If anything you'll probably just wind up making the ride harsher.

 

[old-git]

If the tyre is made of the same compound and inflated correctly then there will be no more grip as the size of the patch in contact with the road surface will be the same regardless of tyre width

 

[HDi fun]

If the tyre is made of the same compound and inflated correctly then there will be no more grip as the size of the patch in contact with the road surface will be the same regardless of tyre width

The shape of the contact patch can change though, even if the overall area remains the same. This can lead to changes in handling, which may not always be to the benefit of outright longitudinal and lateral grip.

In general you're better off with a high performance tyre of standard size than with a cheap one fitted to oversized rims. To take full advantage of wider and bigger diameter rim/tyre combinations you need to assess the whole suspension setup.

Stiffer does not automatically mean more grip. It can totally bugger up a well designed car and leave wheels with inadequate downforce if the road is not perfectly smooth.

 

[old-git]

The shape of the contact patch can change though, even if the overall area remains the same. This can lead to changes in handling, which may not always be to the benefit of outright longitudinal and lateral grip.

In general you're better off with a high performance tyre of standard size than with a cheap one fitted to oversized rims. To take full advantage of wider and bigger diameter rim/tyre combinations you need to assess the whole suspension setup.

Stiffer does not automatically mean more grip. It can totally bugger up a well designed car and leave wheels with inadequate downforce if the road is not perfectly smooth.

Yup.

The advantage of a wider tyre is that, as the contact patch is shorter (but wider) it is in contact with the road for less time so has more time to cool down. This allows softer compounds to be used, which WILL improve grip. However it is very unlikely that you will be able to get a 235mm tyre in a softer compound than a 225mm in the same make and model.