Saturday, December 10, 2011

Why one should respect the tires - Understanding tires Part 1

This is the 1st of 5 posts about tires.
1(this) is about how important it is to understand tires and what to consider when buying them.
2 is about the tire measures and proportions one can see in the tire walls.
3 is about tread design
4 is about compound and structure
5 is about maintenance and repair

I've seen lot's of people driving around worrying about how their car looks, how polished it is, how lowered it is and just how much more horsepower they have after installing a muffler...but ignoring the rubber their 1000miglia rims are running on. Most of them drive on normal "street" tires and some even go the budget tire way.
I've also seen the average guy that squeezes all the buck to buy a BMW or VOLVO or SAAB, and then buy the 50€ plastic tire.

Tires are your connection to the ground...their the one that maintain you ON THE ROAD. It's pointless to spend 60.000€ on a car and then go cheap on the tires, eventually spending 10.000€ on a new front-end every other month!
This is one of several tire topics as these are important parts of you vehicle package, subject to a tremendous amount of stress, with maintenance need and normally the only thing that prevents you from crashing every 10 seconds on the road.

This first part goes towards tire choice.
There is a reason why manufacturers have several tire lines. Some are better in the dry, some in the wet, some are more comfortable, others more stiff... and that's not all; The compound, the tread pattern design, the side wall, the proportions, the wheels they are fitted to... and so on.

I've seen people chose tires because they look good, because they are cheap, because their best friend told them to, because the car had them as standard, etc etc etc. These are all bad and even worse reasons for tire choice.
You chose a tire following a checklist that should have an order similar to this:
1 - The weather you're driving it into
2 - The type of road and driving style you use them on
3 - The type of car
4 - The weight of the car
5 - The life time you expect for the tire
Now please keep in mind that I haven't even considered cost as the new front-end every other month costs a lot more.

About point 1 on the check-list
Some countries have extreme weather, creating a healthy habit of choice towards the conditions. Most people have (at least) 2 sets of tires that change according to the time of year (winter and summer tires). In Portugal this is very difficult to come across. I have this habit, but I also have a Honda S2000, so I respect weather and it's conditions...and survive that way.

About point 2 on the check-list 
I normally see tuned-up cars driving around on normal tires. This is a bad thing. The simple fact of lowering the car and not correcting the cambers will increase the load on the inner tire wall, making most tires unfit immediately as they'll be working all times under extreme deformation conditions.
Even if you don't change a thing in the car, most road cars come of the line with compromise tires. Far from being the best tires (most are the result of a protocol signed between big tire manufacturers and the car manufacturer). They, as most things on the car are chosen according to country and average driving habits and normally aimed for comfort and fuel economy.
Take this example:

This tire is brand new... it only has 200Km on it. The thing is that it's the STANDARD rear tire of a BMW 118D that was enjoyed to the maximum in a mountain b road.
It used to be like this:

So why is it like that? Because it's a standard comfortable all weather road tire.
It wasn't built to endure abuse like that and as a result, it didn't endure.
If you are driving hard, and in a road with degraded tarmac, this will happen to standard tires:
1 - The groves that will allow the tire to channel water out in the rain will become surface fracture points and LITERALLY enable the friction against the tarmac to torn chunks of rubber out of the tires as you can see in the picture.
2 - The soft compound rubber that allows your tire to grip even on cold weather will start to melt with the friction caused by heat, making the tire greasy and also creating that melting pattern you can also see in the picture that will later became rips.
3 - The comfortable and SOFT tire sidewall that deforms to absorb road irregularities will bend, reducing the amount of rubber that actually touches the ground and eventually will oval your tire profile leading to bad handling and eventually uneven wear punctures.

On the 3rd Checklist point - Car type.
Most cars around are FF (Front engined Front wheel drive). This makes the tire choice very difficult. The same tires have to be good putting the power on the ground and also steering the car. These are very different design orientations. Something I'll be talking about in the 3rd post about tires.
The FR (Front engined Rear wheel drive) and MR (Mid engined Rear wheel drive) cars are better in this matter. Some manufacturers even sell tire "Systems" instead of tire models like Pirelli's PZero system witch has the "assimectrico" (asymmetric) for the rear tires and "direccionale"(directional) for the front ones.
The AWD (All Wheel Drive) is probably the most odd. Some 4WD systems are fixed bias (meaning that the same amount of torque goes to the wheels every time)...but others behave like front or rear wheel drives until traction is lost an the bias shifts to the other wheels at that precise moment, returning to previous setting as the traction is restored.
Again, a topic for the 3rd and 4rth articles (better register to the blog if you really are interested).

On the 4rth Checklist point - Weight.
It's an issue to address in the 4rth article. But the rule of thumb is, the heavier the car, the more load you'll constantly put on the tires. This will then be related to tire lateral wall structure and tire compound. See ya in article nr4.

On the 5th Check-list point - Life time and wear.
It's a simple rule. If you have summer tires, as long as you buy a good tire (meaning that you'll have the same compound all the way into the tires life) it really doesn't matter much. The Slicker they are the more contact with the ground they have and the better they'll grip. This statement assumes the tire is good enough to maintain it's geometry and not bend under load.
However in terms of rain tires or all weather tires, than I'd suggest not to buy with wear resistance in mind. You need grooves to channel water out. If the tires wear fast, then you'll buy new ones fast and have new grooves. If they wear fast then the rubber compound grips better and that means that it will grip good even on the wet and cold.
So make your choice based on these points and avoid accidents.

So how did I choose my tires:
1st Portugal has some very hot and dry summers, and some wet with severe raining winters. Portugal is also a 3rd world country meaning that out roads are poorly built and the heavy rains will create large pools (sometimes authentic rivers crossing the road 5 meters wide).

These conditions mean that the tires will grip good and also wear a lot during summer, and during winter they'll be half-life and far from perfect to resist aquaplaning. Since I've got a 240Hp Rear Wheel drive car with little lock angle, no driver aids electronics and an explosive tendency, choosing rain tires is crucial to survive the winter.
That sealed part of my buying options. I should try to have a winter tire setup in my original Honda wheels, and a full dry tire setup to may 5zigen rims.

My car had these Bridgestone RE050A as standard.

You can understand how good it is in terms of grip not only for the compound (probably the best compound around in street performance tires) but also by the design that creates several lines of constant contact with the ground, especially the inside part of the tire (here to the left).
This design however is poor in terms of water flow towards the sides of the tire, something very important in aquaplaning situations.
These tires normally endure 30.000km before becoming illegally SLICK, but they are NOT suited for aquaplaning resistance after the 15.000Km. Hell they are not brilliant as new, so any wear will only make it worse.

So If I was to go extreme in tyre choice, that a full flow design should make up the winter choice. Two became an option.
1st the Toyo T1-R

2nd the Falken FK452

Both designs use heavy groves to flow water "out of the tire's way". The Toyo uses a central 100% contact band with a Zig-Zag'd design and adds lateral full 100% contact bands on each side of the tire. This will CLEARLY make it an excellent cornering tire, but this also means that the water being pulled from the inside will hit this wall and travel along it...and this in not so good when you try to prevent aquaplaning.
A good look at the Falken will show the same central 100% contact band (though it's area is around 75% of the 2 Toyo bands combined), and a flow oriented design all the way from the V grooves to the side of the tire without blockage. This clearly make the tire a lot more aquaplaning resistant.

The 1st choice was made. Falkens FK452 it is for the winter.

Now for the summer tire choice... well I was thinking of buying full race slicks, but then I came across these and the Toyo R888 was the choice made.

Some people have asked why didn't I stick with Bridgestone. Well, BS gives-me a 30.000km tire that is no good for aquaplaning, and clearly dangerous in the aquaplaning matter since it's half-life.
For the same money, I can buy 2 sets of Falken that will last 25.000km each and maintain a better aquaplaning resistance with 20.000km than the bridgestone with 15.000km.
And during summer, the R888 are in a different league and incomparably better than any road tire.

Next I'll be talking about tire sizes and all those references you can see on the tire wall.