Do wider tyres improve handling?

[iOnic]

Current debate at work.

Yes or No. Give reasons.

[Stott69]

Theres a few depends in there. Will depend on such things as starting size, run preasures type of driving being done.....

[KinLoud]

Answer is complex....
I would start with "mostly/sort of"

Wide tyres have the same contact area touching the Tarmac as a narrower tyre
Contact area depends on tyre pressure (lower = bigger, low pressure for driving on soft surface)
The contact area is wider but shorter for a wider tyre
Advantages
- more grip for turning (braking doesn't change unless its wet)
- looks cool
Disadvantages
- maximum grip is at a smaller slip angle and decreases rapidly at bigger slip angles (narrower tyre loses grip more slowly = more forgiving)
- in the wet will aquaplane at lower speed than narrow tyres

[iOnic]

Lets say its on a factory RX8. Factory tyre width is 225 all round. Will going to a F-235/R-255 stagger like mine runs (or 235 all round) improve handling? Everything else being equal.

Bear in mind that traction/= handling.

[Mr Ree]

Putting a wider section on the rear of the 8 will make the car slightly more prone to understeer.

But it wont make too much noticeable difference unless you do a before and after direct comparison at the track

[jondee86]

I imagine that once the factory have done with designing the
shiney parts of the car, they just chuck on whatever wheels and
tyres they have lying around. So, yeah, any Joe Hunt should be
able to improve the handling with a set of rimz and wide tyres

Cheers... jondee86

[iOnic]

I think ideally it should have the same size tyres front and rear and no wider than 235. My steering response is noticeably slower than a factory rx8 and as you said it tends to understeer especially at low speeds eg doing a u-turn. I'm going back to factory tyre sizes on it. I strongly believe that increasing tyre width doesn't do anything good for handling.

My workmate's son has fitted something big like 245-285 on a basically factory 350z (has Nismo wheels and Nismo springs) and it drives so much worse than it did before the change.

[KinLoud]

Go for good tyres in a factory size
e.g. Goodyear Eagle F1 Asymetric

http://www.tyrereviews.co.uk/Article/20 ... e-Test.htm
http://www.tyrereviews.co.uk/Article/20 ... e-Test.htm

I've got the Goodyear Eagle F1 Directional5 (model below the Goodyear Eagle F1 Asymetric) - fabulous grip!

LOL - reading tyre reviews...
I see they now use fuel use/rolling resistance as part of the judging!
So a tyre with less wet and dry grip wins
I know that the cost of a crash will cost more that any fuel saved!

[KinLoud]

Also remember that a brand new tyre (lots of tread/tall blocks of tread) will feel a bit squirmy for a while compared to your worn tyres with very low blocks of tread.

[2jayzgte]

I think alot will depend on how your suspension is in your car if you still have stock suspension it may not help.

I noticed going to a wider track with the suspension I am using it gave more rear end stability under acceleration and the car felt more pointy in the front.

I think alot has to do with the profile you use.I think going to a 30 profile does nothing for handling.I still keep a 40 profile on all 4 corners I think that works well especially in the rear when your car squats under hard acceleration having that slightly higher profile helps or thats what I have found anyway.

[rollaholic]

Bear in mind that traction/= handling.

this is probably the crux of the debate, you and your workmate are essentially arguing about different things

[THA SHZ]

alot of whether it would benefit would also come down to rim width , if its too wide for a narrow rim then no , if its too narrow for a wide rim then no

[Luke - BZG]

Wide tyres have the same contact area touching the Tarmac as a narrower tyre
Contact area depends on tyre pressure (lower = bigger, low pressure for driving on soft surface)
The contact area is wider but shorter for a wider tyre

I'm Confused, how would a 185 tyre at 30psi have just as much rubber touching the road as a 315 wide tyre at 30psi?

id say tyre diameter would play a part just like air pressure. Bigger diameter would give a bigger contact area.


*edit*

Does recommended tyre pressure decrease as tyres get wider?

[iOnic]

If the same amount of weight is being exerted (ie same car), the wider tyre will have a wide but short contact patch where the narrow tyre will have a narrower but longer contact patch. Area will be the same so you dont actually have any more rubber on the road. To increase the area you have to reduce pressure/increase vehicle weight/use tyres with less tread (ie semi/full slick).

The conclusion we came to is that you want a contact patch that is as wide as it is long for the vehicle's given weight in a good tyre compound. Outside of that, you're most probably compromising straight line acceleration or cornering grip/response. Having too wide tyres on a car that is too light to exert enough force to maintain the ideal contact patch will actually reduce cornering grip/induce understeer.

Just random bored mechanic musings with no scientific evidence to back it up though

[molex]

There are many aspects to handling better.

To add another interesting angle - serious autocross cars have ridiculously wide rim/tire combos, usually limited only tire availability and rules. General consensus in that realm of motorsport is that more tire = faster almost without exception. That's certainly backed up by the results.

Is the same true in a higher speed circuit scenario? Probably not, or at least not for the same reasons. More tire in a high speed situation could potentially improve performance due to having more rubber to spread around heat load, in turn allowing for a softer compound.

It's an interesting discussion. My personal experience has been wider = worse, in terms of general road behaviour and 'feel'. I don't have any comparative lap time data unfortunately.

[Grrrrrrr!]

Answer is complex....
I would start with "mostly/sort of"

Wide tyres have the same contact area touching the Tarmac as a narrower tyre

That would only be true if tyres were flexible like a balloon. Since tyres have an inherent stiffness of their own its not quite that simple. The local pressure where the tyre touches the road varies. I have seen pressure plots of a ball bouncing, most of the pressure is on the outside edge and only a little in the center. (tennis balls turn partially inside out). Obviously a tyre is designed to spread the load, so is probably more even across the tyre but i'd still bet there is a reasonable amount less pressure (against the road) at the dead center of the contact patch than just inside the perimeter. And then there is the effects caused by the fact the whole thing is spinning... its messy, and there are plenty of big horrible mathematical models of tyres, and you could easily get a Phd in developing a better model of tyre traction etc.

[2jayzgte]

I tell you what having under inflated wide tyres in the wet comprimise's handling big time.In the wet you actually want less rubber on the road so it cuts through the standing water basically running 3-4 psi more a corner stand the side walls up a bit more helps big time.

[KinLoud]

2jayzgte - yes, higher tyre pressures = higher speed before aqua planing occurs.
For aircraft tyres the formula is:
Aquaplane speed in knots (nautical miles per hour) = approx 9x (square root) tyre pressure in psi
So 100 psi tyre pressure = 9 x 10 = 90knots = 166kph
So if you increase tyre pressure the minimum speed for aqua planing is higher

Car tyres will have a slightly different but similar speed due to tyre width and different tread pattern

[fielderz]

2jayzgte - yes, higher tyre pressures = higher speed before aqua planing occurs.
For aircraft tyres the formula is:
Aquaplane speed in knots (nautical miles per hour) = approx 9x (square root) tyre pressure in psi
So 100 psi tyre pressure = 9 x 10 = 90knots = 166kph
So if you increase tyre pressure the minimum speed for aqua planing is higher

Car tyres will have a slightly different but similar speed due to tyre width and different tread pattern

Wow cool, an aquaplane and an airplane all in one convenient craft.

More seriously, very interesting discussion- what iOnic said above certainly sounds correct for an equilibrium stationary (static) situation: The car exerts a force downwards due to gravity proportional to its mass, while the pressure in the tyres counteracts by exerting a pressure over the area of the contact patch, where P(A) = F . Would be very interesting see what actually happens in a dynamic situation though.. I suspect its complicated.

[matt dunn]

I tell you what having under inflated wide tyres in the wet comprimise's handling big time.In the wet you actually want less rubber on the road so it cuts through the standing water basically running 3-4 psi more a corner stand the side walls up a bit more helps big time.

I run the wets on my race car at about 20psi higher starting pressure than my dry tyres.