[sagarpadaki]

This question is there in my mind since a long time.Is the "Grip" quotient of a tire determined by the quality of the road surface that is laid? Why i am asking this is because of an experience i had few weeks back that triggered this sleeping doubt in my mind

I was driving my i20 CRDi(Fully loaded with 34 PSI). which is shod with Apollo acelleres on mysore roadAs many of you might know here its got one of the finest surfaces with almost no potholes-just clean plain surface(with ocassional monster speed breakers!!).When driving at around 80 kmph i had few situations of cows and stray dogs running across and whenever i braked the tires performed as per my expectation .Later on took a diversion and entered a single lane "Well Laid" carriageway.At one point a motorist cut across in my lane suddenly and i did a panic braking at around 70 kmph.And the ABS kicked into action . I thought this was a one off case and on further down the same road i found a long straight stretch and thought i would try it again.After ensuring that no one was behind me i pressed the brakes with the SAME PRESSURE at 80 kmph as i applied on mysore road at the same speed and the ABS kicked again.And the road was relatively newly laid.It had that fresh appreance on it.And there was no gravel on it either.

So this got me thinking.What factors of the asphalt quality affect the grip of the tire apart from the rubber compound of the tire.Experts and knowledged persons on this forum can give a few explanations to this phenomenon

[srishiva]

@sagar, the road surface along with how flat the road is, should matter. You need the contact patch between the road and tyre to be maximum as much as possible. Even well laid roads with unevenness will reduce the contact path.

[dhanushs]

Grip means, friction between Tyre and Road. Just like this friction is affected on a wet surface, it is also affected by road quality.

So.. Yes, the road surface matters a lot. That's exactly why we have rubberized roads these days.

[sgiitk]

Also, how is the surface laid, and whether wet or dry. remember the lot of noise about new Mumbai roads (Mastic Asphalt) becoming skid traps in the wet due to improper laying.

[ghodlur]

Originally Posted by dhanushs

Grip means, friction between Tyre and Road. Just like this friction is affected on a wet surface, it is also affected by road quality.

So.. Yes, the road surface matters a lot. That's exactly why we have rubberized roads these days.

Would the grip then be different for the asphalted road and concrete road? The why does the braking more confidence evoking on a concrete road than asphalted road even though freshly laid although the contact between the tyre and the road surface is same in both cases.

[mayankjha1806]

I have found the grip to be better on concrete road as compared to Tar road. More so when its wet and Tar road gives a feeling of slipping where as concrete does not. The other factor on Tar road is when even a small layer of dust or rubble the brakes skid a little, this does not happen on concrete.

The only time i don't like concrete is on a two wheeler and somehow fall down on the road. Any skids on the concrete road will leave you with lots of scratches on bike's and self's body.

[MadhanBabu]

Every surface(road) and material(in this case rubber) has its own friction coefficient. Hence the grip level keeps changing constantly while the vehicle is travelling. It also depends upon the load in the vehicle, the tire pressure, road surface dryness, dust on road,bumpiness, etc. That is why the races like WRC where the track surface keeps changing (like ice, asphalt, mud) is very challenging for the drivers and is interesting from spectators perspective.

[dhawcash]

Also, some newly laid road surfaces ( especially single lane ones in rural areas) are pretty badly built. The inter-granular bond is very weak and the road is kind of soft. i remember how i parked my bike on one such road to take a few pics of the scenery, and while doing that heard a loud thud. The road surface was so poorly built that the bike's stand pierced through it's surface and into the soft soil below, making the bike fall. Such a surface would act like gravel for fast cars.

[Aroy]

The braking depends on the friction between tyres and the road surface. As in this case the tyre are constant it will depend on the road friction.

All road surfaces are designed with a pre determined friction coefficient, and proper geometrics. In case the formulation is tampered with or due to bad construction (both method and materials) the surface friction can decrease due to
. Incorrect material resulting in a slicker surface. This is especially evident when the temperatures cross 45 degrees and the surface just flows.
. Incorrect laying so that there are a lot of micro undulations, which present lesser surface to tyre patch.
. Bad base material or bad labour practices, which results in differential road settlements along and across the road. If the undulations are small enough they will have the same behaviour as the point above. I have seen a lot of so called "new" roads deteriorating in just a couple of months of use.

Other factors which affect braking
. Minute amounts of sand/water/oil which act as lubricants during braking. As SH may have lighter traffic these contaminants may accumulate longer on SH than on NH which has heavy traffic.
. Bad road design, primarily incorrect camber at curves. Braking at those curves will slew you to the outer edge.

That said, in your case the NH is built with tighter supervision in both materials and labour, so has a better over all ride quality, braking and high speed performance. A SH has looser controls, and at times left on the contractor's discretion. This may result in a poorer performance. Mind you both roads may look same to a driver when new, but behave differently as stated above.

Regarding better braking on concrete roads. Concrete roads are rougher and have a lot of micro surface undulations, which give these roads higher friction coefficient while braking. At the same time modern concrete roads are laid with sophisticated machinery which ensures proper material and road laying methodology, resulting in better over all quality of construction.

[Mpower]

Absolutely, its a pleasure to drive on freshly laid asphalt.

On the other hand, shiny smooth cement roads have the worst grip.

[sagarpadaki]

So does it mean irrespective of how good the tire is it finally boils down to the quality of asphalt laid on the road? Does a softer compound and well engineered tire stand a better chance of maintaining the composure of the vehicle when driven and braked on these kind of rural roads?

[roadie_swift]

Originally Posted by mayankjha1806

I have found the grip to be better on concrete road as compared to Tar road. More so when its wet and Tar road gives a feeling of slipping where as concrete does not. The other factor on Tar road is when even a small layer of dust or rubble the brakes skid a little, this does not happen on concrete.

The only time i don't like concrete is on a two wheeler and somehow fall down on the road. Any skids on the concrete road will leave you with lots of scratches on bike's and self's body.

IMO, I've always found the tar roads to offer better grip in a car, and I have been in a couple of hairy situations myself. I think the reason is that the tar molecules are slightly less tightly packed (on a molecular scale) than the concrete ones. As such, there is a minor sponginess to the tar surface, may be just like a mouse-pad, which results in them offering a better grip.

Also, in wet conditions, the tar roads are slightly more apt to absorb the water on the road, than concrete is. As such, they turn out to offer more grip and (slightly) lesser chances of aqua-planing.

Coming back to the OP, I think the asphalt quality very much affects tire grip. Even within tar roads, we have types - some that are really smooth like Sharjah pitches (pardon me!!) where on a hot day you can see your reflection, and some that are rougher in texture, due to the little higher content of gravel, which would as such offer more grip, although also along with bit more tire wear. Also, I've found the gravelly roads to be better in wet conditions.

Cheers,
R_S

[Aroy]

Originally Posted by sagarpadaki

So does it mean irrespective of how good the tire is it finally boils down to the quality of asphalt laid on the road? Does a softer compound and well engineered tire stand a better chance of maintaining the composure of the vehicle when driven and braked on these kind of rural roads?

Softer compound will give better grip on any surface, but at the cost of higher wear rate.

Tyre pattern is designed for a particular environment
. No pattern for hard rock.
. Block pattern for mud and snow.
. Designs with drainage channels for wet roads.
Similarly
. Hard compound for longer life
. Soft Compound for better grip
. Special compounds for low temperatures

As tyres heat up during use, special care is taken to cool them. At very high speeds the tyres may disintegrate due to heat build up, hence always use proper speed rated tyres for high speed. That is one of the reasons for high speed tyres to be low profile - they have less rubber hence dissipate heat faster. As sidewall flexing contributes a major portion of heat build up, high speed tyres have softer sidewall thus prone to damage due to side impacts compared to normal tyres.


Theoretically bald tyres will give the best grip on a dry road, but will aquaplane if there is any water. Patterns and thin sipes (groves) are provided for drainage. As the tyre presses on the wet ground the channels squeeze the water towards the sides, to maintain a dry patch for tyre to grip. There is no such thing as a tyre perfect for all cases, only optimised compromises.

For those who are interested, the tyre nomenclature is

225/55 HR15

225 = rim width in mm (most bias ply tyres have the width in inches and a normal profile, hence numbers like 7.5/15)

55 = profile, that is ratio of width to depth. Thus 225/55 will have a tyre depth of 225*.55 = 123.75 or ~ 4.9 inches (2 x depth + Rim Dia = Tyre Dia)

R = Radial, no letter is bias ply

15 = rim diameter in inches

H = Speed rating
Q- Up to 100mph
R- Up to 106mph
S- Up to 112mph
T- Up to 118mph
U- Up to 124mph
H- Up to 130mph
V- Up to 149mph.
W- Up to 168mph.
Y- Up to 186mph
Z- 149mph and over

H and Z are most popular rating in the premium market

Links
Goodyear Jamaica || Tyre Knowledge || Reading a Tyre Sidewall
What does W and V in tyre name stand for? If there are other names tell me about them too? - Yahoo! Answers

[ghodlur]

Originally Posted by Mpower

Absolutely, its a pleasure to drive on freshly laid asphalt.

On the other hand, shiny smooth cement roads have the worst grip.

Thats strange coz I though the concrete roads are specifically groved to establish the grip. Whereas the freshly laid asphalt road have the chances of the growels/small stones used to come off and get stuck in the tyres therby reducing the road grip. I may be wrong here. But I dread driving on the road which is being laid with the tar for the pure reasons of the tar sticking to the underbody and the parts.

[Durango Dude]

If things are fully under control (meaning you are sure of the braking distance of your car), ABS cuts out the drama of panic braking situation making the car come to a halt in a linear fashion plus allowing you to steer the car. Braking distances can increase if there is loose gravel and also if there road is water logged and also if the tyre's get bald and also on smooth concrete surfaces.