High grip or lower grip tyres for road use?

[300bhp/ton]

Inspired by the improving wet wether traction thread running at the moment.

I'm wondering what the consensus is on how much grip a road going weekend car should have?


At present I'm in the process of getting my TR7 V8 back on the road, as I haven't used it much for a few years. I'm considering tyres. To which my thoughts were some semi-slicks.... just because...

The car will never be used for commuting. Only for fun and pleasure driving. I've run semi-slicks in the past on it. And should I choose to do a track day or even an auto solo with it, they would be a much better choice.

But semi slicks make it much harder to wheel spin and requires higher speed and a more aggressive driving style to get the back to be playful. As there are no trophies, podiums or prize money for driving on the road. Do I really need the higher cornering speeds and late braking that semi-slicks offer?

Or would it be more fun to take a leaf out of the GT86's ethos and fit some relatively crappy tyres to it and just enjoy going most places sideways?

I can see the arguments for both camps. But that doesn't make me any less torn in making a decision?

[300bhp/ton]

LordGrover said:

I suspect a TR8 would be a little tail happy and unpredictable at the best of times anyway, no?

It's quite a sideways car, but nice and progressive. Not snappy. Love sliding it about, it's all part of its character. It's not mega quick. 200'ish hp. Sort of DC5 ITR straight line pace (0-100mph in 15'ish sec) and weighs a shade over 1 tonne.

Used to run Michelin Pilot Sport Cup tyres on it many years ago. Lots more grip, but less hooliganism. Has been on a variety of road tyres since then though.

[300bhp/ton]

GravelBen said:

I generally prefer a lower grip tyre for fun, but with consistent response and feel (no soft wobbly sidewalls) and avoiding really budget tyres which are often ok in the dry but teflon in the wet. Its hard to find a lower grip tyre with a firm sidewall though.

The 'won't somebody think of the children you must have the grippiest tyres you can possibly afford' brigade are wrong when it comes to enthusiastic driving IMO - with stickier tyres you won't have any less desire to play with their limits at times, but the speeds will be higher with less margin for error when you do.

I had semislicks on a turbo MX5 for a while. They were actually still better than most road tyres I've had in the wet, but they raised the limits in the dry so high that road driving became less fun. On an interesting road you were often limited by visibility before you felt like you were really working the tyres, and if you did let loose and have fun you quickly found yourself in irresponsible territory. Magic on track though, you could still play sideways games just at higher speed and without melting and falling apart like road tyres on track.

I’m glad you posted this. As it is exactly my thoughts. Grippy or semi slicks just mean you are going a lot faster to enjoy the vehicle. And they tend to make it more snappy at the limit, because of the speed.

Therefore a less grippy tyre in many ways seems a safer road option. As you’ll be able to have fun at lower speeds. But I completely agree about the sidewall, I don’t want to dull the turn in or make it feel a squidgy mess just because of the tyre choice.

I’m also very glad you have said about wet weather grip with semi slicks too. My Pilot Sport Cup tyres were brilliant in the wet. Much more grip than most normal road tyres, on the proviso there wasn’t standing water or heavy run off.

[300bhp/ton]

xjay1337 said:

Sorry these opinions are unfortunately wrong.
Backed up by data on wet braking data from Tyrereviews.co.uk .

Also the statement "a less grippy tyre is a safer road option" - absolute BS . Sorry.

So you reckon cornering say 10mph faster with a more sudden brake away is safer than a progressive breakaway at lower speeds?

Haven’t followed the link yet. But is that site just people posting reviews based on personal opinion. Or is it scientific testing of tyres? I’m assuming you are referring to semi slick wet weather performance?

[300bhp/ton]

This track tyre is rated at B for wet use. And is marketed as good in the wet.

[300bhp/ton]

xu5 said:

While it is fairly hard to argue against a more grippy tyre being safer in absolute terms, if there was a slight trade off in feedback and feel so that you could access your cars balance more easily I can see the argument. I don't think OP was meaning to fit some Chinese recyled coat hangers in the name of sliding about on every corner.

I do think that the quest for all out grip can be at the cost of enjoyment, particularly if you favour a cars balance at sane speeds. Obviously you would drive to the conditions.

Absolutely spot on.

[300bhp/ton]

xjay1337 said:

Please look at the link, and have a read .

You are also assuming that a premium / sporty tyre has a more aggressive break away than a "lower grip" tyre when you have absolutely no evidence to back this up?

Michelin PS4 for example are incredibly nice breakaway.

Then again I would ask why are you using this as an example of why you want to justify fitting stty tyres.

Cheaper lower grip tyres have worse breakaway, they are not consistent.

You've posted about NS2-R
Which are not very good in the wet at all (i've driven on them in the wet).

They are a "semi slick" (IE a track based summer tyre).

Do you do any track days? Regularly? If not, fit some PS4's and be done with it ffs.

where have I said about fitting crappy tyres??? Are you reading the wrong posts or something?

If the NS2R isn’t good in the wet. Why is it marketed as being so? As said my semi slick Pilot Sport Cup tyres were brilliant in the wet.

[300bhp/ton]

Johnspex said:

Someone on here told me to get back in my box and get someone to lock it .


A person of my acquaintance did a speed awareness course and during that course he was told of the investigation that took place if you were involved in a fatal accident. I was astonished, what you'd had for breakfast and investigations into your private life amongst others.
Imagine what they would make of someone who went on a public forum asking about tyre without too much grip.

Heaven help you if you have the misfortune to be involved in a fatal accident. Never mind me being locked in a box, how do you fancy being locked in a cell?

Are you being unreasonable on purpose or just plain not understanding? 99.9% of cars sold by car makers do not come on tyres offering the most grip.

You are off your rocker if you are saying they all shouldn’t be on the roads.

[300bhp/ton]

xjay1337 said:

Marketing can LIE... maybe you've only just realised this.

I'm telling you that NS2R are crap in the wet and Cup2s are also pretty crap in wet with any standing water.
Up to temp on a "damp" circuit they're OK up to the point of water dissipation limits. PS4 are faster on a properly wet circuit.

As I said , if you're not doing trackdays , buy PS4 or your other choice of premium UHP summer tyres.

Are you doing trackdays? Does the car get driven in wet weather regularly ?

I still maintain fitting deliberately lower grip tyres is dumb and so is any sort of drifting or "getting tail out" on the public road. Incredibly so. Certainly not impressive to brag about either.

Only need to read on these pages about the guy who was out on a leisure drive who ended up in Jail.

Don't be that guy. Take it to the track.

And on track - there is no reason to not use your premium UHP tyre

I think you are getting mixed up.

High grip = semi slick
Lower grip = normal road tyre

Are you really trying to say fitting a normal road tyre is not acceptable?

[300bhp/ton]

xjay1337 said:

I'm not getting mixed up.
But thanks for clarying.

Just FYI

Semi slick have a narrower window of operation than most UHP summer tyres.

So on the road at road speeds your UHP tyre will have more grip more of the time.

I had a set of Dunlop Direzzas on my Scirococo track car for a while.
My normal tyres were Vredestein Vorti at the time but I had a couple of trackdays over a 2 week period so I had them fitted and used them on the road for commuting and a little trip to the beach


On the road I remember I drove to Mcdonalds , it was around 10 degrees. I turned into a roundabout at normal speed around 3 miles from my house ..... and the back end came round.
ESP intervention meant I didn't really need to do anything but it was snappy and unexpected such sedate speeds.

Why? Because the tyres were cold, the road was cold, they werent up to their operating temperature.

They were the only set of tyres I had to be mindful of warming up properly. I also had AD08R fitted to the car. These were fitted only when :

1) the car was not being used every day as I had a daily
2) the car was only ever used in good weather

However I did get caught out a few times with the weather as you can imagine in the UK.
On the road in the wet they handled very much like a lower end tyre. My car had a very aggressive geo with nearly 3 degrees of negative camber set up and also corner weighted to put as much weight on the front axle as possible . So i generally had better wet grip than a "standard " car anyway but still you had to be mindful of it.

I also had to do a very very very wet Snetterton on them and it was horrible. Snetterton can be slippy when wet but this was ridiculous. My mate had PS4s and had zero issues! I was getting wheelspin in 5th! In a diesel!

If it was a car that was used mixed weather then I'd only ever fit PS4 (or your preferred choice of premium UHP tyre).
As I do with my M135i.
As I said I had a set of Cup2s and sold them. I'm not compromising day to day grip in wet and cold conditions for a few % extra performance on the track which the car spends 2% of it's total miles on.

So hence why I ask

Do you do trackdays reasonably regularly
Do you only ever plan on using the car in dry warm conditions.

Only if yes to both of those questions then look into buying an AD08R (not the newer RS. They're awful) or R888 or whatever semi slick you want.

Otherwise just put some normal UHP summer tyres on.

I'm not really a track day goer. But thinking about getting into it more so.

Have done autosolos and gymkhanas (called targa rallies these days). Which are all held on closed courses.

Then just country lane driving. Mostly near'ish to home. Wouldn't take it if it was raining or expected heavy prolonged rain.

However as said, the Pilot Sport Cup tyres were pretty awesome all the time in all conditions.

If there was standing water or heavy run off. I'd simply pull over or slow down. No biggy tbh.

The car is quite modified. Only the doors and bootlid are standard. It is also currently geared for short course work. Tops out at about 115mph in 5th at around 5500-6000rpm. So on dual carriage ways I tend to cruise at around 60mph. Although I have a new diff and may regear as the gearing is probably too short for bigger tracks.

Need to remember, it's a classic car. The entire vehicle is setup to move about a heck of a lot more than a modern M car. Even if it was 100% standard. There is no ABS, no TCS, no ESP. It doesn't even have PAS!

I've also owned this car since 2001 and spent many many hours in it.

[300bhp/ton]

DonkeyApple said:

You’re problem with pulling over or slowing down as a tactic is that there aren’t many other road users left who naturally understand how cars such as yours work and so don’t expect you to be doing those things. Part of the compromise with setting your car up is that you have to consider the mindset of the average person who is behind you and how infrequently they, for example, adjust their stopping distances based on what the car in front of them is. It’s not 100% about how you can easily cope with a situation but how much you also have to factor in how little someone following you may cope.

Isn't this true of all traffic at all times though? I drive various vehicles on the roads, some stop very well. Some much less so. And that's in the dry.

[300bhp/ton]

camel_landy said:

I'm another fan of sticking to manufacturer spec of sizes and to not go for the 'Bling' options. The smaller rims mean you get larger side walls and a more comfortable ride. The drop in width also means you're going to benefit when the weather turns...

M

I think it might depend on the car in question. My TR7 would have had 175 or maybe 165's from new on 13" rims. Not sure I'd really want something that narrow with a 200hp V8 under your right foot. Not to mention 13" rims wouldn't clear the brakes now anyway.

[300bhp/ton]

camel_landy said:

<sigh> Yes... You're going to have to chose a suitable rim to fit.

...but don't forget the TR8 was a production car, so so you probably want to be using the TR8 rather than the TR7 specs.

The point I made earlier is that without any extra weight, you're not going to be able to make use of any extra rubber. You should hopefully get better traction from the modern tyre compounds but you're not going to gain much from going wider. (OK, there's a bit more to it than that but it's a good starting point.)

M

Edited by camel_landy on Monday 13th July 13:03

TR8 also has 13" rims and low CR 137hp motor. Think they were 185's.... hardly a real improvement in traction. And also very different gearing to what I'm running.

The works rally cars used much wider tyres however, I bet they gripped a lot better than a standard car on standard sized tyres did. But who knows, maybe they should have come to you for advice

[300bhp/ton]

camel_landy said:

Here's a useful explanation from a Pistonheads thread a while back:

carbibles said:

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 of the rubber compound and the load on the tyre. As far as friction is concerned, the formula is relatively simple - F=uN, where F is the frictional force, N is the Normal force for the surfaces being pressed together and u is the coefficient of friction. In the case of a tyre, the Normal force basically stays the same - mass of the car multiplied by gravity. The coefficient of friction also remains unchanged because it's dependent on the two surfaces - in this case the road and the tyre's rubber.
The coefficient of friction is in part determined by the rubber compound's ability to 'key' with the road surface at a microscopic level.

This explains why you can slide in a corner if you change road surface - for example going from a rough road to a smooth road, or a road surface covered in rain and diesel (a motorcyclist's pet peeve). The slide happens because the coefficient of friction has changed.

So do wider tyres give better grip?
If the contact patch remains the same size and the coefficient of friction and frictional force remain the same, then surely there is no difference in performance between narrow and wide tyres? Well there is but it has a lot to do with heat transfer. With a narrow tyre, the contact patch takes up more of the circumference of the tyre so for any given rotation, the sidewall has to compress more to get the contact patch on to the road. Deforming the tyre creates heat. With a longer contact patch and more sidewall deformation, the tyre spends proportionately less time cooling off than a wider tyre which has a shorter contact patch and less sidewall deformation. Why does this matter? Well because the narrower tyre has less capacity for cooling off, it needs to be made of a harder rubber compound in order to better resist heating in the first place. The harder compound has less mechanical keying and a lower coefficient of friction. The wider tyres are typically made of softer compounds with greater mechanical keying and a higher coefficient of friction. And voila - wider tyres = better grip. But not for the reasons we all thought.

What about lateral force in cornering?
In terms of the lateral force applied to a tyre during cornering, you eventually come to a point where slip angle becomes important. The plot below shows an example of normalised lateral force (in Kg) versus slip angle (in degrees). Slip angle is best described as the difference between the angle of the tyres that you've set by steering, and the direction in which the tyres actually want to travel. As you corner the lateral force increases on your tyres, and at some point, the lateral force is going to overcome the mechanical grip of the tyres and that point is defined by the peak slip angle, as shown in the graph. ie. there comes a point at which no matter how much vertical load is applied to the tyre (from the vehicle weight), it's going to be overcome by the lateral force and 'break away' and slip. So why do wider tyres perform better when cornering? Well apart from the softer rubber compound giving better mechanical keying and a higher coefficient of friction, they have lower profile sidewalls. This makes them more resistant to deforming under lateral load, resulting in a more predictable and stable contact patch. In other words, you can get to a higher lateral load before reaching the peak slip angle.

M

I'll admit I'm not a mathematician.

A bit of Googling has resulted in several places same the same sort of thing:


That while tyre pressures and tyre widths do indeed alter the contact patch shape. They also alter its size. Unless I'm reading this incorrectly, it is saying the wider the tyre, the bigger the contact patch. Maybe at higher pressures it would change or be less so?

[300bhp/ton]

camel_landy said:

300bhp/ton said:

A bit of Googling has resulted in several places same the same sort of thing:

^^^ That's for a bike tyre...

M

Does the physics work differently with bike tyres?

[300bhp/ton]

camel_landy said:

...conveniently forgetting they choose different tyre/wheel combinations, depending on the rally.

...and conveniently forgetting you are driving on the road and not a rally stage.

M

Some of the events described in my op are a bit like tarmac stage rallies

And yes, they did run different tyres for different surfaces. I don't recall them running narrow 185's on any tarmac rallies however.

[300bhp/ton]

Honeywell said:

I'm often impressed by the GT86 brakes. Once warm they have amazing stopping power I find (on PS4 rubber). The size and specification of them is rather hum drum but some combination of the low weight and ultra low centre of gravity makes them feel tremendous. More so than any other cars I've owned of considerably higher performance.

Plus a conventional handbrake lever means you can handbrake turn in the car park when nobody's about and you can't do that in in any new Ferrari!

Think my smart Roadster stopped the best out of the cars I've owned. Although you could still cook the brakes on it. A little wooden feeling through the pedal, but you got used to it.

Had a '20 Ignis as a curtesy car this last week. Was surprised how poor the brakes were on it. Came flying down one of my local routes, went to stand the car on end, as you do.... and it just didn't want to slow down. Was quite shocked at how little it wanted to shed the speed.

Even more surprising, it wouldn't or couldn't lock the rear wheels to perform a handbrake turn.

[300bhp/ton]

DonkeyApple said:

The world is arguably a little different today but when I was younger it was pointed out to me by a family friend, who I believe still holds the record for the highest number of professional race wins in the UK, that the cheapest and best upgrade to do to a car to make it faster was to improve the brakes.

I would agree, especially on a race track, but I think in some road cars and some road driving, you don't actually use the brakes all that much. But then I was taught to use engine braking a lot more than people are today. There are no podiums when driving on the road, so you don't need to always heavily brake at the very last tenth of a second. Getting the speed right for the corner before you enter it, can result in rapid progress and generally a lot smoother too.

[300bhp/ton]

DonkeyApple said:

Yup. The same chap pointed out that the engine was for moving the car forward and the brakes were for taking speed off. He was quite expressive on not using the engine for braking as you were obviously only applying braking to two wheels. FWD is going to be more forgiving.

I’ve watched many a TVR driver spear their car off before a corner because they were only braking with the back wheels.

Guess they wouldn't be much cop as at driving old trucks or tractors with heavy loads then

Engine braking serves a good purpose outside of the race track. And in a lot of different types of machinery.

Watch how little the brake lights come on...
https://youtu.be/tl8UY6GuLe8?t=113