35 replies to this topic

[mariner]

Interesting article here from autocar

 

http://www.autocar.c...tch-slick-tyres

 

I guess its sort of half the history of recent motor racing - tyres and downforce = lap speed.

 

Mind you the point about value for money is valid. £1,000 worth of track tyres can make a Megane as fast as a Prorsche Cayman - no handling slouch itself.

 

I wonder if the perceived good handling is partialy due to the stiffness of modern bodyshells. The car can work the sticky tyres without flexing?

[Tenmantaylor]

The reason it feels better is that there is massive amount more rubber in contact with the road. About 20-30% I'd guess depending on the tyre tread. Slicks are much more liable to aquaplaning though, a lot of the slick wet performance could have come from being a very stick short life compound maybe that wouldn't last anywhere near as long as a road tyre. Road tyres are designed for practical everyday use, water displacement, safety and lifetime, not lap time.

Edited by Tenmantaylor, 23 October 2013 - 15:12.

[Greg Locock]

No, I don't think you need an especially stiff bodyshell to get an advantage from decent tires, and in terms of max latacc stuff I doubt the body stiffness makes any odds at all. I've just been at a seminar where some nerds (or geeks, or both) had run 1000 variations of body stiffness and also run the same bodyshell through our standard handling tests, and a bunch of other tests like crash and noise and durability so we could come up with an optimum body. From this we will be able to plot handling vs torsional stiffness...

 

Interesting point about the slicks in the rain

[gruntguru]

More rubber on the road = more grip is a bit simplistic. Slicks offer higher grip levels for several reasons.

 

Less tread squirm - all the little blocks of tread are connected to each other so there is much more strength and rigidity. On its own this offers better feel and response but not necessarily better grip however - because the tread is better supported, the compound can be made softer without exceeding the shear strength and removing layers. Softer compound = more grip.

 

More rubber on the road - on its own not much advantage in grip terms, but the greater area available to share the shear force during cornering means the shear stress (force per unit area) is reduced allowing (again) a softer compound and better grip.

[Tenmantaylor]

Great explanation gg

[desmo]

 

 

Interesting point about the slicks in the rain

 

Indeed, indeed.

[Lee Nicolle]

The Avon road tyres are road tyres. Will do 20 plus thousand KM, give decent grip in all conditions and surfaces. Put some street legal semi slicks [ Yokohama, Toyo, Dunlop] on it and the times then would be similar to the slicks on a road car.And may give 2 thousand km on the street, maybe! And probably track faster in the wet [not monsoon] Then stiffen springs and bars then the slicks should outperform the semi slicks.
But to drive on slicks on the road,, sorry but that would be scarey, great grip initially, after a few days no grip at all as the heat cycles are used up. And little puncture resistance in comparison to road tyres, and no performance on dirt either.
All the hooha about body stiffness is just that. The majority of modern sporty cars are fairly good and could be raced totally unmodified.Except ofcourse springs and shocks to get the use of the tyre grip available. They may be a fraction better with a stiff cage etc [and safer] but it will not be huge. The cage though will hold it together after a while as the shell gets softer as all cars do.
Though there is some very quick and also very rusty cars out there in classic racing!!

[Rasputin]

First of all, I believe you will find the tarmac out there on the road quite different from the track.

 

Regarding those smart-comments about slicks and rain, think nothing of it, everything is sped-dependent.

[Greg Locock]

Having just watched my wife's son race a 600cc bike on slicks in the rain against others on wet tires I thought it was actually quite interesting. But I bow to your superior knowledge. Now, about the tarmac thing, last time I checked the guys laying the tracks in Australia at least are the same ones laying the roads. Odd that.

[gruntguru]

I would imagine a motorcycle slick would be much better at "parting the waters" than a car slick due to the long slender shape of the contact patch. I often wonder when I see treads on a 23mm wide bicycle tyre - such a tiny contact patch (especially at 100+ psi) and relatively low speed too.

 

The racetrack surface is different once "rubbered up" with sticky racing rubber.

[desmo]

On pavement the tread pattern on a typical 23mm road bicycle tire is just there for styling purposes.  In fact the narrow tire section is primarily dictated by style, empirical testing has shown wider section tires roll more efficiently. But they "look" slow.

[Lee Nicolle]

First of all, I believe you will find the tarmac out there on the road quite different from the track.
 
Regarding those smart-comments about slicks and rain, think nothing of it, everything is sped-dependent.

Race tracks use the same material as do roads. That material can and will differ quite a lot depending on the amount of traffic, the expected speed of the traffic, how thick the bitumen will be and the type and quality of the road base. and ofcourse what gravel is in the mix.And weather conditions play a major part in the choice. Many governments have road test strips, all the different materials. It has been known to test it on race tracks too.
After all that the hotmix on the main road outside the racetrack gate will often be exactly the same on the racetrack.

[munks]

On pavement the tread pattern on a typical 23mm road bicycle tire is just there for styling purposes.  In fact the narrow tire section is primarily dictated by style, empirical testing has shown wider section tires roll more efficiently. But they "look" slow.

I'd be interested in a link for that if you happen to have one. What about the aerodynamics?

[desmo]

Bicycle Quarterly which I subscribe to has done some empirical tests.

 

https://janheine.wor...mance-of-tires/

[Greg Locock]

Great stuff. When Michelin designed tires for our solar car they also sent a graph showing rolling resistance vs pressure, 55 psi was the optimum. Any more than that and the extra vibration in the suspension drives the shocks. It sounds like they think the rider has a similar effect on a push bike.

[Canuck]

Looking forward to a faster tire pressure...once the snow leaves.

[Rasputin]

Perhaps I did not exactly refer to the chemistry of the tarmac, but the difference in overall smoothness, level and quality in general between the track and the typical pothole roads we face north of the equator.

 

But I guess we should draw a picture everytime we make a statement crossing the stalwarts of this here forum.

[gruntguru]

Great stuff. When Michelin designed tires for our solar car they also sent a graph showing rolling resistance vs pressure, 55 psi was the optimum. Any more than that and the extra vibration in the suspension drives the shocks. It sounds like they think the rider has a similar effect on a push bike.

 

http://www.michelinb...irpressure.view

[mariner]

I know many car performance tyres are assymetric with respect to tread pattern and, I presume , construction.

 

Does anybody know if there are tyres with a assymetric compounds?

 

I imagine that realy difficult but in theory you could set the tyres up at lots of negative camber with harder long wearing surface in contact then as the car rolls under hgh G the soft grippy rubber would come into play.

 

I imagine it would be trickery but it could, potentially, reduce rolling resistance and improve stabilty as the grip would rise as lateral G rises

[Fondles]

Does anybody know if there are tyres with a assymetric compounds?

 

It's done with some motorbike tyres so it should be possible with car tyres.

[John Brundage]

I know many car performance tyres are assymetric with respect to tread pattern and, I presume , construction.

 

Does anybody know if there are tyres with a assymetric compounds?

 

 

 The Michelin Pilot Sport PS2 has two different compounds

[MattPete]

Does anybody know if there are tyres with a assymetric compounds?

 

 

 

Bridgestone had a mid-range touring tire back in the 1990s that had an asymmetric compound (re92?)

[Lee Nicolle]

Bridgestone had a mid-range touring tire back in the 1990s that had an asymmetric compound (re92?)

RE92 was a high mileage family car tyre. A good tyre in its day for the towcar!

 

Many tyres these days that make some pretence of being a performance road tyre are asymmetric. Better deal than the generally noisy directional tyres manufacturers inflicted on the public in recent times. The asymmetric are generally quiet and wear better too.

Nobody would make a road tyre with different compounds across the tread. Really a waste even for a race car. Though in the past a harder outside rear tyre was often very handy. Most tracks predominantly turn left or right. Generally no faster but more consistent. Though the big time hero racing these days seems to have banned all commonsense like that and make pitstops every 10 laps instead.

Edited by Lee Nicolle, 05 November 2013 - 07:53.

[John Brundage]

RE92 was a high mileage family car tyre. A good tyre in its day for the towcar!

 

Many tyres these days that make some pretence of being a performance road tyre are asymmetric. Better deal than the generally noisy directional tyres manufacturers inflicted on the public in recent times. The asymmetric are generally quiet and wear better too.

Nobody would make a road tyre with different compounds across the tread. Really a waste even for a race car. Though in the past a harder outside rear tyre was often very handy. Most tracks predominantly turn left or right. Generally no faster but more consistent. Though the big time hero racing these days seems to have banned all commonsense like that and make pitstops every 10 laps instead.

Lee,

Below is a copy and paste from the Tire Rack info about the Michelin PS2 that I mentioned above. These are my favourite summer tires for my car.

 

On the outside, Pilot Sport PS2 features two different tread rubber compounds (a hybrid silica/carbon black compound that begins at the tire's outer shoulder and continues across the tread until it joins a high-silica compound that continues to the tire's inside shoulder) molded into an asymmetric design with large outer shoulder blocks and continuous intermediate and center ribs to enhance steering response and cornering stability. Both tread compounds are specifically formulated for their location to combine dry and wet traction with crisp corning and high speed capability. The tread design also features wide circumferential grooves and lateral notches that help channel water through the footprint to enhance wet road traction.

[Lee Nicolle]

Lee,
Below is a copy and paste from the Tire Rack info about the Michelin PS2 that I mentioned above. These are my favourite summer tires for my car.
 
On the outside, Pilot Sport PS2 features two different tread rubber compounds (a hybrid silica/carbon black compound that begins at the tire's outer shoulder and continues across the tread until it joins a high-silica compound that continues to the tire's inside shoulder) molded into an asymmetric design with large outer shoulder blocks and continuous intermediate and center ribs to enhance steering response and cornering stability. Both tread compounds are specifically formulated for their location to combine dry and wet traction with crisp corning and high speed capability. The tread design also features wide circumferential grooves and lateral notches that help channel water through the footprint to enhance wet road traction.

Hardly a mainstream tyre. Very expensive and made in very few sizes. And they go hard very quickly so I am told by a Porsche owner I know. As do any very hi performance tyre. They are however a step away from a true semi slick, though they are a lot faster on a racetrack.

[John Brundage]

Hardly a mainstream tyre. Very expensive and made in very few sizes. And they go hard very quickly so I am told by a Porsche owner I know. As do any very hi performance tyre. They are however a step away from a true semi slick, though they are a lot faster on a racetrack.

 

These are mainstream here. Accoding to Michelin these were "original equipment on renowned sports cars like BMW M3, Porsche 911, and Corvette ZR1". Further on their site they list the OEM codes for these tires on Mercedes, Audi, Cadillac, Ferrari, Dodge etc. Tire Rack notes that some of the first OEM fitments were on the Porsche GT2/GT3, McLaren SLR, and the BMW Alpina Z8. Michelin lists 85 different tire configurations for this model, Tire Rack carries 76 of them.The wear of these tires on my car was excellent--the car was not tracked. I got about 45,000 miles on a set. They gave excellent grip dry and wet. Here, the 225/45ZR17 costs $200- each.

[Lee Nicolle]

These are mainstream here. Accoding to Michelin these were "original equipment on renowned sports cars like BMW M3, Porsche 911, and Corvette ZR1". Further on their site they list the OEM codes for these tires on Mercedes, Audi, Cadillac, Ferrari, Dodge etc. Tire Rack notes that some of the first OEM fitments were on the Porsche GT2/GT3, McLaren SLR, and the BMW Alpina Z8. Michelin lists 85 different tire configurations for this model, Tire Rack carries 76 of them.The wear of these tires on my car was excellent--the car was not tracked. I got about 45,000 miles on a set. They gave excellent grip dry and wet. Here, the 225/45ZR17 costs $200- each.

The Michelins here in Oz are national debt expensive and from what I am told good for about 4500km before they go hard and are useless. This on an upmarket 3-4 y/o Porsche. He is using mainstream Bridgestones which are less than half the price and are far more consistent. And I sell cheaper [not nesecarily lower performance] brands for half the price of the Bridgestone.
I suspect also those $200 Michelins are not multiple compound, just their normal road car offerings which are OEM on many passenger and sporty cars these days. An ok tyre but really too expensive. The aftermarket replacement ones never seem to wear as well as the originals either. A common failing in most OEM tyres it seems. Which never seem to balance as well as the originals either.

225x45x17 is a tyre that suits many small/ med size Euro cars for a 7" rim. I supply an asymmetric tyre in that size for under $120 AUD in a couple of brands

[Kelpiecross]

Speaking of Michelins in Oz - back in the 60's I found that the XAS was very good on Minis - but Michelin X and ZX were dangerous to the point where the tyre designer should have been sent to jail.

[seldo]

The Michelins here in Oz are national debt expensive and from what I am told good for about 4500km before they go hard and are useless. This on an upmarket 3-4 y/o Porsche. He is using mainstream Bridgestones which are less than half the price and are far more consistent. And I sell cheaper [not nesecarily lower performance] brands for half the price of the Bridgestone.
I suspect also those $200 Michelins are not multiple compound, just their normal road car offerings which are OEM on many passenger and sporty cars these days. An ok tyre but really too expensive. The aftermarket replacement ones never seem to wear as well as the originals either. A common failing in most OEM tyres it seems. Which never seem to balance as well as the originals either.

225x45x17 is a tyre that suits many small/ med size Euro cars for a 7" rim. I supply an asymmetric tyre in that size for under $120 AUD in a couple of brands

Lee, I would proffer a different experience .
For a start, I have always found the OE tyres to last a lot worse than the replacements - on my current car, a 300+kw atw Senator, the OE 235/40x18 Bridgestone SO3s lasted less than 20k and the replacement SO3s lasted about 33k, as did the next set of SO3s and the current Michelin PilotSport 3s will make similar or better, and imho, a much better tyre to drive on at a cheaper price than the Bridgies.
And, as I'm sure you would agree, having driven on race slicks on the road, they are not pleasant at all - tram-tracking and pulling, and generally totally impractical under any circumstance.

Edited by seldo, 09 November 2013 - 07:19.

[Lee Nicolle]

Speaking of Michelins in Oz - back in the 60's I found that the XAS was very good on Minis - but Michelin X and ZX were dangerous to the point where the tyre designer should have been sent to jail.

40 years ago ZX were an ok tyre for a family car. 45 years ago they were Bathurst winning tyres!
The X was the first mainstream radial over 50 years ago
Edit,, I think XAS were the Bathurst winners, the story goes with the belts hanging out at the end!!

Edited by Lee Nicolle, 12 November 2013 - 22:56.

[Greg Locock]

 The Michelin Pilot Sport PS2 has two different compounds

 

A tire chemist (not a career path that I had thought of) reckons that multi compound tires are the next big thing, as standard OEM fitment in the USA. Reason is cold weather performance vs rolling resistance vs wet braking (from what I remember).  Given how modern tires are made (laid up from layers in the flat) then it seems not especially difficult to get the rubber in the right place, getting adjacent strips to bond is probably the trick. Incidentally if you cut through almost any old radial tire you'll see some different rubber is used in the shoulder region, there all sorts of odd wedges and strips. These prevent the belts from eating the main rubber, and is turns out are hugely important in steering. I got the impression from a tire OEM that much of the tuning they do is concerned with the shoulder wedges.

[MattPete]

I found it: it was a Turanza.  I remember seeing adds that touted a second softer compound that was revealed after there was significant tire wear. I think the idea was to increase the stickiness to partially counteract hydroplaning when there was less tread:

 

http://www.tirerevie...f_24_cents.aspx

[gruntguru]

Softer compound doesn't help with true aquaplaning. The tyre is not touching the road but water-skiing above it.

 

The softer compound may compensate for the normal hardening that occurs with age and use - ie by the time the "soft" compound is exposed, it has similar grip to the tyre when new.

[indigoid]

A tire chemist (not a career path that I had thought of) reckons that multi compound tires are the next big thing, as standard OEM fitment in the USA. Reason is cold weather performance vs rolling resistance vs wet braking (from what I remember).  Given how modern tires are made (laid up from layers in the flat) then it seems not especially difficult to get the rubber in the right place, getting adjacent strips to bond is probably the trick. Incidentally if you cut through almost any old radial tire you'll see some different rubber is used in the shoulder region, there all sorts of odd wedges and strips. These prevent the belts from eating the main rubber, and is turns out are hugely important in steering. I got the impression from a tire OEM that much of the tuning they do is concerned with the shoulder wedges.

 

Already happening with motorcycle tyres. For obvious reasons they are not asymmetric but there are a few now with a hard compound around the middle for long boring highway and soft compound to either side for when you are getting up it in the mountains

 

I have Pilot Road3 on one of my bikes as of a few weeks ago, and had a few sets of its predecessor (Pilot Road2) before that. The Michelins consistently yielded 20-25kkm per set before hitting the wear limit markers, which is obscenely long for bike tyres. Most of the others I've tried have managed 10kkm at best

[Lee Nicolle]

Softer compound doesn't help with true aquaplaning. The tyre is not touching the road but water-skiing above it.
 
The softer compound may compensate for the normal hardening that occurs with age and use - ie by the time the "soft" compound is exposed, it has similar grip to the tyre when new.

Tread depth is the principle thing to stop aquaplaning. 4 wd tyres resist it very well. Useless ofcourse as a performance tyre. Though a decent 4wd is actually quite agile on wet bitumen. for me comparing the Landcruiser over a Falcon on wet twisty roads. The cruiser is about the same pace as the dry,,[not all that fast!] The Falcon is slipping , wheel spinning and damn slow on the same piece of road. Those big tyres and high roll centres help a lot in those conditions.
The ever noisy directional passenger tyres that were the go in recent times are a bit better in very wet conditions. And just noisy in the rest!!

[MattPete]

Softer compound doesn't help with true aquaplaning. The tyre is not touching the road but water-skiing above it.

 

True, but I always assumed that it was "well, when the tire does come in contact with the pavement, it will have more grip"...