Do bigger wheels = less grip?

antodeco

Hi Folks,

Changed my 16" wheels to 17" wheels and have noticed a severe drop in grip. Could this be the tyre size or bad tyres? They are new wheels and tyres.

Thanks

colm_mcm

are you driving a jeep or a car? What size and brand did you change from/to?

BreadBoard

antodeco wrote:

Hi Folks,

Changed my 16" wheels to 17" wheels and have noticed a severe drop in grip. Could this be the tyre size or bad tyres? They are new wheels and tyres.

Thanks

Could it be weather related? I've noticed my car sliding a little more recently due to the icy weather.

antodeco

Ive had the tyres 3 months, and its always been there

Driving an 06 almera. Went from Nissan standard Dunlop 16's to Autogard 17's. If i accelerate in a straight line, it slips sideways fighting for grip. Its also kicked out on me a few times. Checked the pressure and get them re aligned, but still the same

colm_mcm

I've never heard of Autoguard tyres. maybe it's because they're not as good as Dunlop?

BreadBoard

antodeco wrote:

Ive had the tyres 3 months, and its always been there

Driving an 06 almera. Went from Nissan standard Dunlop 16's to Autogard 17's. If i accelerate in a straight line, it slips sideways fighting for grip. Its also kicked out on me a few times. Checked the pressure and get them re aligned, but still the same

Could be the tyres ... are they the same width as the 16's you had?

antodeco

Thats what I was thinking. I was thinking of changing the tyres and going for something slightly wider anyway (dune buggy look )

colm_mcm

I reckon the answer is in the brand you've got. I've noticed big differences in grip even between big name brands, This might be unfair, but I suspect the tyres you have now are cheapies

layke

To answer your question, yes.

Don't ask me the physics though. I've just heard it from a few people who I would consider reputable.

antodeco

Hmm!! The grip is considerably different on these. Whilst on the subject (sort of), is it possible to get wider tyres for a wheel?

colm_mcm

yeah, no problem getting wider tyres, but the profile of the tyre (the percentage of thickness of the sidewall to the width of the tyre) has to be reduced to prevent the outside radius of the tyre getting too big for the car. Also, too wide a tyre and you will scrub the arch liner on full lock.

greglo23

with a wider tyre you have less grip as the weight of the car is spread over a wider area. just look at the ice racers and snow tyres; they are really skinny tyres so the footprint of the tyre is smaller which gives more grip.
it looks to me that the cheapie tyres are your problem though. if you want serious grip get high end pirelli's. amazing grip but they dont last long :rolleyes:

antodeco

right so ill try wider tyres out the window then!! I do alot of driving, so dont want no squeaky tyres when i turn Id love a set of pirelli's but ill have them gone in around 2 weeks!! Any other advice on tyres?

Seth Brundle

never heard of Autoguard tyres but seemingly they are cheap high performance yokes from Pirelli. Where did you get them and what sales pitch were you given?

antodeco wrote:

Thats what I was thinking. I was thinking of changing the tyres and going for something slightly wider anyway (dune buggy look )

Your driveshafts, etc. may not be able for the extra strain.

antodeco wrote:

Hmm!! The grip is considerably different on these. Whilst on the subject (sort of), is it possible to get wider tyres for a wheel?

You can but they would probably be an unusual size and therefore more costly. What size are the new ones?

antodeco wrote:

Driving an 06 almera. Went from Nissan standard Dunlop 16's to Autogard 17's. If i accelerate in a straight line, it slips sideways fighting for grip. Its also kicked out on me a few times. Checked the pressure and get them re aligned, but still the same

What kicked out? The rear? If it slipping in a straight line then I would ditch them asap!

Hagar

Pirelli's on a fully loaded Citroen Dyane FTW.

antodeco

Probs the best idea! Just get new tyres. In this weather im noticing it alot more. Both front and back kick out. Went around a corner and the front slipped out, turned around a roundabout and the front just "drifted"!

fletch

greglo23 wrote:

with a wider tyre you have less grip as the weight of the car is spread over a wider area.

Bull****....perhaps in the wet/snow a narrower tyre is more favourable as it is less likely to aquaplane but in dry conditions, a wider tyre will most certainly provide more grip.

greglo23 wrote:

just look at the ice racers and snow tyres; they are really skinny tyres so the footprint of the tyre is smaller which gives more grip.

It gives them more grip as each tyre is exerting more pressure per square inch and therefor is better able to displace the snow

greglo23 wrote:

it looks to me that the cheapie tyres are your problem though.

Would definitely agree....my car is on cheapy tyres at the moment(bought it 2nd hand not so long ago) and the thing feels like its on ice skates! :eek:

311

I'm not an authorithy on cars or anything ,but I thought that there is certain tyres that have to go on one way.
If tyres are put on the wrong way ,what happens ?

greglo23

How can you seriously believe that the same weight spread over a wider area gives more pressure. in fact a wider tyre exerts less pressure because the weight is distributed over a greater amount of road. take the example of snowshoes. you can walk over loose snow wearing snowshoes where you would sink wearing boots. the same principle applies to tyres.

Blitzkrieger

_Brian_ wrote:

I'm not an authorithy on cars or anything ,but I thought that there is certain tyres that have to go on one way.
If tyres are put on the wrong way ,what happens ?

That's an interesting point. I took my father's car for it's NCT and the guy noticed that one of the tyres was on backwards. I had kinda noticed that the tail wanted to kick out when turning left. Maybe they did put them on backwards.

apeking

_Brian_ wrote:

I'm not an authorithy on cars or anything ,but I thought that there is certain tyres that have to go on one way.
If tyres are put on the wrong way ,what happens ?

I got myself 4 new alloys, bought the second hand so i went and tried fitting them myself, went to the garage two weeks later to get a puncture fixed and the lad told me my wheels were on the wrong sides.


I was wondering why i was sliding around all over the place in the rain, not a good idea, at all

fletch

_Brian_ wrote:

I'm not an authorithy on cars or anything ,but I thought that there is certain tyres that have to go on one way.
If tyres are put on the wrong way ,what happens ?

I'd say you'd notice quite a difference if you put these tyres on the wrong way around

Owen

I've 18's under my MINI, and they improved both grip, and ride quality. So no, larger wheels do not detract from Grip (Larger wheel, larger tyre, larger contact patch = more grip).

Iompair

It depends on the conditions, big wide tyres are best on dry smooth roads. On wet irish roads narrower tyres are better, less liable to aquaplane.

Anyway get a better set of rubber, Perrelli are good, I've got a set of bridgestones on now, way better then the goodyears I got with the car.

Barr

The width of a 16" could be the same as 17" so it may not even be down to the size
I used to run 16" Dunlops on my present car then changed these for a set of 18". The tyre that came with them was some cheap crap I never heard of. The car used to slide all over the place especially in the wet. Went back the following week and changed to Semperits and the handing is definately on a par if not better than the dunlop 16"

As said before its your tyre make thats giving you such poor grip.With a bigger alloy you'd want decent quality tyres

with a wider tyre you have less grip as the weight of the car is spread over a wider area. just look at the ice racers and snow tyres; they are really skinny tyres so the footprint of the tyre is smaller which gives more grip.

I'd have to disagree with this statement if this were the case why would'nt Formula 1 cars have skinnier tyres. They spent millions looking to gain a extra tenth and look at the width of those rear tryes!

Geek Nose

I just got all new 18" Pirelli Zeros on my XK8. When it's dry, the grip is amazing, but over the last few days I've noticed the back spinning out a bit on roundabouts & turns - obviously when it's icey or wet, and without even going that fast!
Wider tyres are much better in dry conditions, but worse in wet or ice. It's simple physics.

Avns1s

Geek Nose wrote:

Wider tyres are much better in dry conditions, but worse in wet or ice. It's simple physics.

This is exactly right.

Hagar

Barr wrote:

I'd have to disagree with this statement if this were the case why would'nt Formula 1 cars have skinnier tyres. They spent millions looking to gain a extra tenth and look at the width of those rear tryes!

F1 cars have are aerodynamically designed to exert downward force on the rear wheels to increase the traction. Hence the massive wings on the back.

My earlier post about the Citroen was based on a test Top gear did many years ago where they discovered to their amazement that the pressure exerted by a Citroen's tyres on the road per square inch was greater than a Porche simply beacuse of the very small footprint of the narrow tyres. However the Porche had more grip because it had more square inches of rubber in contact with the road surface albeit at a lower pressure, the sum of the pressure was greater.

Barr

F1 cars have are aerodynamically designed to exert downward force on the rear wheels to increase the traction. Hence the massive wings on the back

This is all ever well but his point was narrier tyres have more grip than wider ones.
By that logic an F1 car should be running on narrier tyres which is not the case, huge wing or not.

Barr

F1 cars have are aerodynamically designed to exert downward force on the rear wheels to increase the traction. Hence the massive wings on the back

This is all ever well but his point was narrier tyres have more grip than wider ones.
By that logic an F1 car should be running on narrier tyres which is not the case, huge wing or not.

Hagar

I heard you the first time.:D

colm_mcm

colm_mcm wrote:

I reckon the answer is in the brand you've got. I've noticed big differences in grip even between big name brands, This might be unfair, but I suspect the tyres you have now are cheapies

The cheapness doesn't affect anything. Even though we don't generally use winter tyres in this country, some thread designs are better for wet weather than others.

TomMc

Tyres should be viewed as the most important part of your car. Irrespective of whether your car cost big bucks or is just a cheap runabout, you should buy the best tyres you can afford. I like Good Year Eagle F1 GSD3 - A great all-rounder.

The most important factors when upgrading wheel size (width), is to get a wheel with the correct offset so they fit properly under the arches and do not rub any bodyparts on full lock or indeed protrude the arches themselves. When buying tyres for same, the rolling radius (circumference) should be roughly the same as before - i.e. similar to the standard manufacturer set up. That means, if you upgrade to wheels that are 1" larger, you need a lower profile tyre to balance things out. Roughly speaking a unit of 10.

Bigger wheels and lower profile tyres mean better handling but shorter tyre lifespan. Also if you look at the thread pattern of directional tyres (like the photo a few posts back), and think how the tyre interacts with the road surface you will see why they can only work properly when placed in a particular direction. Do you want the tyre to dispurse the water away from under your path as you move or channel same back under the tyre, further risking aquaplaning. Its a no-brainer.

For me, having wider tyres and so more rubber on the road is a good thing. The other factor when buying wider rims is to make sure they are not much wider so as to cause problems with a cars steering set up.

antodeco

Hmm! I have been thinking of getting lower profile tyres anyway. The acceleration has naturally decreased by the larger tyre. My main worry is that with a lower profile tyre, the risk of ruptering the alloy increases. With the current state of irish road, the last thing I want is to hit a pot hole and buckle the wheel.

zuutroy

the more rubber in contact with the road, the better the grip because more of the force or the cars motion will be absorbed by the friction between the tyre and the road, so there'll be less of a tendency for it to go in an unwanted direction.. So wider tyres have more grip, as do underinflated ones. The problem could be that your tyres are over-inflated (or just crap )

Henry Ford III

Some insane posts here. Laughable.

Avns1s

Henry Ford III wrote:

Some insane posts here. Laughable.

I think I know what you mean but maybe an elaboration would be useful.

Geek Nose

Henry Ford III wrote:

Some insane posts here. Laughable.

The irony...

SouperComputer

Henry Ford III wrote:

Some insane posts here. Laughable.

Have to agree. I could elaborate but I dont know where to start!

Henry Ford III

Geek Nose wrote:

The irony...

Of what?

Ernie Ball

The answer, for anyone who still cares can be found on this page. I didn't have the stomach to wade through it.

Wishbone Ash

Ernie Ball wrote:

The answer, for anyone who still cares can be found on this page. I didn't have the stomach to wade through it.

Hope you don't mind Ernie - I've narrowed it down:

Fat or thin? The question of contact patches and grip.

If there's one question guaranteed to promote argument and counter argument, it's this : do wide tyres give me better grip?
Fat tyres look good. In fact they look stonkingly good. In the dry they are mercilessly full of grip. In the wet, you might want to make sure your insurance is paid up, especially if you're in a rear-wheel-drive car. Contrary to what you might think (and to what I used to think), bigger contact patch does not necessarily mean increased grip. Better yet, fatter tyres do not mean bigger contact patch. Confused? Check it out:

Pressure=weight/area.

That's about as simple a physics equation as you can get. For the general case of most car tyres travelling on a road, it works pretty well. Let me explain. Let's say you've got some regular tyres, as supplied with your car. They're inflated to 30psi and your car weighs 1500Kg. Roughly speaking, each tyre is taking about a quarter of your car's weight - in this case 375Kg. In metric, 30psi is about 2.11Kg/cm².
By that formula, the area of your contact patch is going to be roughly 375 / 2.11 = 177.7cm² (weight divided by pressure)
Let's say your standard tyres are 185/65R14 - a good middle-ground, factory-fit tyre. That means the tread width is 18.5cm side to side. So your contact patch with all these variables is going to be about 177.7cm² / 18.5, which is 9.8cm. Your contact patch is a rectangle 18.5cm across the width of the tyre by 9.8cm front-to-back where it sits 'flat' on the road.
Still with me? Great. You've taken your car to the tyre dealer and with the help of my tyre calculator, figured out that you can get some swanky 225/50R15 tyres. You polish up the 15inch rims, get the tyres fitted and drive off. Let's look at the equation again. The weight of your car bearing down on the wheels hasn't changed. The PSI in the tyres is going to be about the same. If those two variables haven't changed, then your contact patch is still going to be the same : 177.7cm²
However you now have wider tyres - the tread width is now 22.5cm instead of 18.5cm. The same contact patch but with wider tyres means a narrower contact area front-to-back. In this example, it becomes 177.7cm² / 22.5, which is 7.8cm.


Imagine driving on to a glass road and looking up underneath your tyres. This is the example contact patch (in red) for the situation I explained above. The narrower tyre has a longer, thinner contact patch. The fatter tyre has a shorter, wider contact patch, but the area is the same on both.

And there is your 'eureka' moment. Overall, the area of your contact patch has remained more or less the same. But by putting wider tyres on, the shape of the contact patch has changed. Actually, the contact patch is really a squashed oval rather than a rectangle, but for the sake of simplicity on this site, I've illustrated it as a rectangle - it makes the concept a little easier to understand. So has the penny dropped? I'll assume it has. So now you understand that it makes no difference to the contact patch, this leads us on nicely to the sticky topic of grip.

The area of the contact patch does not affect the actual grip of the tyre. The things that do affect grip are the coefficient of friction and the load on the tyre - tyre load sensitivity. Get out your geek-wear because this is going to get even more nauseatingly complicated now.


The graph up above here shows an example plot of normalised lateral force versus slip angle. Slip angle is best described as the difference between the angle of the tyres you've set by steering, and the direction in which the tyres actually want to travel. Looking at it, you can see that for any given slip angle, a higher coefficient of friction is obtained with less vertical load on the tyre.


As the load on the tyre is increased, the peak obtainable lateral force is increased but at a decreasing rate. ie. more load doesn't mean infinitely more lateral force - at some point it's going to tail off.
Rubber friction is broken into two primary components - adhesion and deformation or mechanical keying. Rubber has a natural adhesive property and high elasticity which allows it readily deform and fill the microscopic irregularities on the surface of any road. This has the effect of bonding to various surfaces, which aids in dry weather grip but is diminished in wet road conditions. Look at this next drawing - this depicts the deformation process as the load varies.


As the load is increased the amount of tire deformation also increases. Increasing the load also increases the contact between the tire and road improving adhesion. As the load increases, the rubber penetrates farther into the irregularities, which increases grip but at a diminishing rate. This next little graph shows the change in deformation friction (Fdef) and the deformation coefficient of friction (Cdef) with change in load.


As far as cars are concerned, any reduction in load usually results in an increase in the coefficient of friction. So for a given load increasing the contact patch area reduces the load per unit area, and effectively increases the coefficient of friction.
If this change in coefficient of friction were not true then load transfer would not be an issue. During acceleration grip is reduced partly from the change is suspension geometry and party from the transfer of load from one set of tires to another. Since the coefficient of friction is changing (non-linearly lower for higher loads), the net grip during acceleration is reduced. In other words maximum grip occurs when all four tires are loaded equally.

That last paragraph also explains why dynamic setup on your car is pretty important. In reality the contact patch is effectively spinning around your tyre at some horrendous speed. When you brake or corner, load-transfer happens and all the tyres start to behave differently to each other. This is why weight transfer makes such a difference the handling dynamics of the car. Braking for instance; weight moves forward, so load on the front tyres increases. The reverse happens to the rear at the same time, creating a car which can oversteer at the drop of a hat. The Mercedes A-class had this problem when it came out. The load-transfer was all wrong, and a rapid left-right-left on the steering wheel would upset the load so much that the vehicle lost grip in the rear, went sideways, re-acquired grip and rolled over. (That's since been changed.) The Audi TT had a problem too because the load on it's rear wheels wasn't enough to prevent understeer which is why all the new models have that daft little spoiler on the back.

If your brain isn't running out of your ears already, then here's a link to where you can find many raging debates that go on in the Subaru forums about this very subject. If you decide to read this, you should bear in mind that Simon de Banke, webmaster of ScoobyNet, is a highly respected expert in vehicle dynamics and handling, and is also an extremely talented rally driver. It's also worth noting that he holds the World Record for driving sideways...........

If you decide to fatten up the tyres on your car, another consideration should be clearance with bits of your car. There's no point in getting super-fat tyres if they're going to rub against the inside of your wheel arches. Also, on cars with McPherson strut front suspension, there's a very real possibility that the tyre will foul the steering linkage on the suspension. Check it first!

antodeco

Damn, I do have Mcphearson struts on it! Overinflation tho may be the key! When I got the tyres they were around 20psi. I asked the lad in the garage and told me they should be the same as before (31psi). So they are currently sitting at around 32psi. If anyone can enlighten me as to what the actual psi should be, it would be very handy, and may solve the case! Tyres: 215/45Z R17 91W

Thanks and Happy Christmas!

Wishbone Ash

antodeco wrote:

Tyres: 215/45Z R17 91W

One would have to know the weight bearing down on those tyres. For example, a 3 litre diesel engine would be considerable heavier than a 1.4 petrol.

Henry Ford III

Wishbone Ash wrote:

In the dry they are mercilessly full of grip. In the wet, you might want to make sure your insurance is paid up, especially if you're in a rear-wheel-drive car.

Got this far. Perfect thanks

My Mk2 escort is awful in the wet. 175 tyres. It's fun but you wouldn't push it.

I drove a Nissan 200SX in very wet conditions which was actually worse. The boost comes in and the rear goes it's own way without any driver input.

Jumpy

_Brian_ wrote:

I'm not an authorithy on cars or anything ,but I thought that there is certain tyres that have to go on one way.
If tyres are put on the wrong way ,what happens ?

I would assume that the air nozzle would be pointing inwards :P

maidhc

Jumpy wrote:

I would assume that the air nozzle would be pointing inwards :P

Umm no.

Directional tyres can only be on the left or right.

Only experience I have of such tyres is on JCBs and tractors. If they are put on the wrong way the effect is much worse than a bald tyre.

Hagar

Jumpy wrote:

I would assume that the air nozzle would be pointing inwards :P

The tyre itself may be on the wheel the wrong way around. The air valve isn't a part of the tyre.

antodeco

Ive checked the tyres, and does say "outside" on them, so theyre facing the right way anyway, but whether theyre on the wrong side or not i dont know! :rolleyes: Ill have to double check the threads and see which way they are facing. Ive dropped the psi by 5 so its running around 29/30, and so far it doesnt seem to be slipping as much, but that could be wishful thinking!

antodeco

well so far so good. Handling seems better, but I hope im not wrecking the tyres! Plus about to fit eibach springs and drop it by 40mm so may feel a little better underfoot