A Dumb Question Regarding Tyre Width And Handling

[Kinkstaah]

Hi all.

Sorry to post what must be a very basic question.

I have just recently obtained a set of new tyres. Previously I had 4x 255/35/r18's.

However, when I went to replace them I was advised that smaller tyres are better for handling, in general. The car is a RWD Skyline, so I was advised I'd get far better handling by running something like 235's up front, and 255's at the rear.

I hadn't heard of anything like this before. Is this true? Is it just weight that would make a difference? We'll assume that the rims involved can fit both tyre widths fine, is there actually a disadvantage for running wider front tires on a RWD car?

Again, sorry if there's a lot of people facepalming away at what is a very basic question that I couldn't find any info on, anywhere.

[blind_elk]

... I was advised that smaller tyres are better for handling, in general.

... so I was advised I'd get far better handling by running something like 235's up front, and 255's at the rear.

These 2 statements contradict each other.

The tyres are there for GRIP. Wider tyres at the rear will, in general, increase the rear grip levels, and that may induce understeer. And, if you are going to fit 2 different size tyres front & rear, then you really should fit 2 different size rims front and rear, because tyres have an optimum rim width which they are designed to fit.

My 2c worth.

[Kinkstaah]

Sorry, I should revise and say that smaller tyres at the front

As in reducing size from a 255 to a 235 at the fronts would improve handling of the car in general, and that going larger would actually cause the car to handle worse. This was irrespective of rim size (i.e, with an appropriate rim for whatever tyre size ultimately selected)

[blind_elk]

Still stands - smaller tyre at the front / larger at the rear means that the rear has more grip, conversely the front has LESS grip. Result - understeer.

Consider the ultimate in tyre size discrepany in a Top Fuel dragster. They have minimal requirements for front grip because they basically don't need to turn corners, so have VERY SMALL front tyres, but have HUGE rear tyres for acceleration grip.

[Kinkstaah]

I realise that, which was why I was skeptical. Surely more tyre, more grip?

Unless he was suggesting somewhat of an offset to counter for a skyline's (somewhat) natural desire to ....oversteer? Uh. Would have thought they were more prone to understeer.

I'm just trying to understand why, when presented with a customer who wanted to buy 4x 255's, that he would try and sell them a cheaper tyre (as its smaller) under the premise of providing better handling.

The angle he was going was that it was physically harder to handle the car (i.e, turn the wheel) if you have big fat fronts.

Is this, for lack of a better term - Completely incorrect? Or one of those things thats technically correct but so infintely small an effect as so it wouldn't be there at all?

[r31slpr]

At carpark speeds you may notice it's slightly heavier, but thats what power steering is for. Highway speeds you won't notice a difference.

He probably tried to sell you the 235's beacause they're cheaper for him to buy, which means more profit when selling.

I'm guessing 235/40/18 to keep close to the same rolling diameter as the rear ?

[Duncan]

well there are some reasons that might be true in some cases. but clearly as a general rule, wider tyres in the same compound will grip better.

some reasons smaller may be better:

* you can buy a better tyre for your money. A good 225 will certainly grip better than a bad 255

* tyre is too wide for the rim - 255 is too wide for an 8" rim but 225 is not

* wet and loose/gravel grip can be better with a narrow tyre because it cuts through the water/dirt to a better surface below.

but generally, a wider tyre grips better because each bit of rubber has longer off the road.

a wider tyre does NOT result in more rubber touching the road. the amount of rubber touching the road is the same for any tyre size for the same weight of car and same tyre pressure, it is just the shape of the rubber in the road that changes.

[bubba]

He's probably remembering trying to do a U-turn in a Torana a couple of decades ago with 265/14's up front and no power steering.

Edited February 6, 2011 by bubba

[NickR33]

get the same size all round then you can rotate tyres and get the most use from them... being rwd you'll use rears faster than fronts... also helps with the understeer (heavy iron block at the front etc)

[Kinkstaah]

Thats more or less what I was thinking, the car had 255's all round before on Potenza RE050A's. He recommended I go smaller. I just found it odd. In the future I'm happy to go back to a 255 profile for better grip. I wasnt exactly being stingy, the tyres he ended up selling me (which grip well, at least atm for what the car is, I can't complain, though I don't notice the steering to be noticably better) were considerably cheaper than the ones I walked in and attempted to buy.

So as this is odd from a sales point of view, I thought I'd ask the wiser minds here. Thanks for the! feedback.

[simpletool]

Yep smaller tyres give better handling. Wider tyres give better grip. When it comes to tyres then grip and handling are commonly considered to be inversely related, all other things being equal.