Quote:
Originally Posted by Mark IV
Always amused by people who b!tch about the cost of the Avons.
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I'd like to say "I don't find the cost of Avons amusing", yet the English language is so weird sometimes. I don't find the cost of Avons amusing, but yet I can also say the price is laughable.
Quote:
Originally Posted by Mark IV
Everything your Cobra does must be done via four relatively small contact patches of rubber; acceleration, braking, turning, are all dependent on the tire contact patch.
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True, but all but braking is a matter of choice. Braking isn't because it could be required during an emergency caused by someone else. Acceleration and braking? You may have a point on the track, but public roads are not a racetrack. I'm sure we all choose to ignore that at times, but I, for one, still can drive in a spirited manner without pushing my car to its limits where the increase of risk is substantially higher.
So... for all of you who have Avons on your car, do you also have the best brake pads money can buy? Or did you get fooled and installed race pads for the street where they won't work well as they don't get hot enough.
What about the best wheel bearings? We don't want a wheel falling of while driving.
There's a lot of things that can make a car safer or more treacherous, but the most dangerous thing of all is the driver.
Anyway, we disagree, but here's some facts I recently posted in another forum and will repeat here:
Coincidentally, I recently bought a durometer…. Just for fun. This one reads rubber hardness on the Shore A scale. So I can check my tires. Softer ought to mean better grip. Unfortunately tire manufacturer’s do not seem to list a Shore rating for their tires. Oddly, many manufacturer’s of Radio Control car tires do. That’s where I got the idea. Hmmm…..
What it is useful for, is to use it on a brand new tire, and then monitor its hardnesss as it ages (and is heat cycled by driving).
Research
I tried doing some research, and here’s some things I found:
1/ According to an old document I found on the net, my BFG Radial TAs have an initial Shore number of 62
2/ From a Corvette Forum:
Mid 50s to 70ish--anything above that & things will get a bit slick, especially on the rears
3/ From a Research Paper:
During a tyre's lifetime, the rubber hardness of individual tyres may increase by up to 15 Shore A, which is equally large as new tyres may differ in hardness due to construction and material design.
4/ From the same source (my interpretation of a chart/table):
Increase in Shore number for tires made in 1990 (with a new Shore rating of 58 ) and stored for 10 years is an increase of 0.9 per year. This was for some unknown model of tire. Other brand tires, or made with newer (or older) technology, or with a different new Shore number would likely vary from this.
5/ From PitStopUSA.com:
I learned that rubber doesn’t have a set shelf life. When stored properly, tires (rubber in general) can last a very long time. Tires can degrade over time but what degrades a tire the most is exposure to heat and light. So if a tire is stored in a dark, cool place it shouldn’t show much signs of aging.
I have been told for most of my life that “Tires get old and should be replaced every five years no matter how they look and how much tread is left.” I have also been told that as a tire ages it gets harder and looses traction. These two things don’t necessarily jibe with what I learned to during my research. Confirming or dispelling what I have been told for so many years seemed relatively simple. Measure the hardness of older tires and compare them to newer tires.
I believe that old tires don’t necessarily need to be discarded just because they are old. I also think I dispelled the myth that older tires get harder as they age. If stored properly tires can have a very long service life. It is not the age of the tire itself that causes problems but extended exposure to the sun and heat that degrades it. Certainly, years of exposure to sunlight and blistering temperatures will ruin a tire and cause it to get hard and crack.
Testing
Before I start, it must be stated that Shore readings increase the colder a tire is and really ought to be measured at room temperature (somewhere I read 23 degC). So my testing doesn’t mean all that much this time of year.
At any rate, I did some testing outside (zero degC), some inside my unheated garage (7degC) and one test at room temp (about 20degC).
First, my BFGs which I bought around 1996 and still look like new due to low mileage and being stored in a dark garage, came in at 78. Even when the summer heat comes around, I doubt I’ll be anywhere close to the “new” value of 62. So they are harder than new, and that means less grip.
Interestingly, using that 0.9 per year figure, mine could be at almost 83, but perhaps lack of sunlight helped. The other source lists a max increase of 15, so that would bring mine up to 77... almost bang on 78.
The 78 number is high based on the Corvette Forum limit of about 70.
I then tested the Michelins on my Toyota, which was outside in the cold and got 62.
It just so happens I had a brand new winter tire inside in the warmth and it measured 58. I then put it outside for about 2 hours, not enough to really get it cold, but enough for the Shore number to increase to 60.
Looking at graphs of tire age vs. Shore values, the hardening of tires (the Shore number) goes up rather quickly over time and starts to level off with a total increase of about 15.
It looks rather exponential with a lot of Shore increase in the first two years. So this means a brand new BFG might have better traction than an Avon that's several years old. Of course that won't happen as the Avons probably won't last that long.
Although Alfa02 (member here) doesn’t appear to like BFGs, I do like his quote:
“…our cars were meant to (Slide) with 15" tires, not stick…”