Quote:
Originally Posted by redpoint5
I'm ignorant when it comes to the tire industry, but it seems a simple test as I suggest, with a dynamometer measuring power required to spin a certain speed under certain load and temperature conditions; you could pretty quickly get a rough estimate of efficiency.
Or does the problem have more to do with breaking in the tire so that it performs in a consistent way?
|
Quote:
Originally Posted by Stubby79
You'd think they'd be able to calculate it fairly closely with computer models, calculations based on tread design and material selection...
Yeah, it won't be perfect in the real world, but it ought to give an idea without the cost of testing every size of a particular tire.
|
If I recall correctly, NHSTA was insistent that a test be performed. They were not going to accept estimates. Given that a recall could be the end effect, the tire manufacturers objected - and the GAO (General Accounting Office) agreed, so the proposed rule was withdrawn.
The test isn't difficult and getting correlations between test sites was possible, but it does take time to do it - and since there are literally hundreds of makes and models of tires - and many sizes in each make and model, and each needed to be tested, the task is quite formidable.
If NHTSA had proposed using estimates - and I'm an advocate of that! - this probably wouldn't have been a problem.
What I find funny about this is that NHSTA already has procedures in place for treadwear ratings that allows for estimates - or more precisely stated: They only ask for the treadwear rating to be traceable back to the official test. That could be done with RR as well, but that's NOT what NHTSA was stating in their proposed rule - and they wouldn't commit off the record to allowing estimates or traceable ratings.
But as I said there was more than one problem, and one I didn't mention was how to display the result. NHTSA wanted to use RRF (Rolling Resistance Force) because smaller tires give smaller values and they thought that this would encourage people to buy smaller cars - while the tire manufacturers wanted to use RRC (Rolling Resistance Coefficient) because people don't buy cars based on the performance of the tires, but they DO buy replacement tires based on their performance and they argued that larger tires (with their better RRC values) would discourage people from buying tires with smaller load carrying capacities (which is what using RRF would appear to be better) and that was directionally safer (less risk of tire failure).
So I was hopeful that this month we would see a revised rule with reasonable expectations, but that is not to be.
Today
Other popular topics in this forum...
