Archive for the ‘Tires’ Category

Pet Peeves

February 27th, 2011 Comments off

What’s wrong with this picture?

2012 Saab 9-5 Sportwagon

If you’re thinking, “It’s a new Saab, but Saab went the way of coelacanth when GM went through its extreme makeover a couple years ago,” you’d only partially be right.  While GM did shed the Saab brand, Dutch company Spyker Cars NV picked up the reins (for a cool $74M), and the brand lives on.

No, the problem with this picture (and ALL of the pictures of Saab’s new 9-5 Sportwagon) is with the tires.  The directional tires.  The directional tires that are mounted in the wrong direction.

Michelin Pilot Sport Tread Pattern (mounted correctly)

The tread-pattern on a directional tire is designed such that, as the tire rolls forward, the channels in the tread evacuate the water from the center towards the outside, allowing the tire to more safely move over wet surfaces.  But to do so, the tires must be installed correctly.  When mounted in reverse, the tread acts in the opposite direction, pumping water directly under the center of the tire – and significantly reducing wet traction in the process.

I’m constantly surprised at the number of cars I see with directional tires that are mounted incorrectly.  I figure, either the owner (or their service department) doesn’t really understand how tires work, or the driver really enjoys hydroplaning.  It’s a pet-peeve of mine.  …But for a car company to release photos of a new model shod with the rubber reversed?

…Am I the only one bothered by this?

Categories: Tires Tags: , ,

Eco-Tires Revisited

November 12th, 2009 Comments off

Bridgestone EcopiaA few months ago, I wrote about eco-friendly tires, and postulated that the decrease in rolling resistance of such tires may result in slightly less grip.  Well, that was a case of a little knowledge being dangerous.  Reading an article this month (in Automotive Engineering International, of course) about Bridgestone‘s new Ecopia line of tires, it was explained that the decreased rolling resistance comes from a sidewall design that “offers improved carbon dispersion.”  In other words, the sides of the tire are stiffer, and flex less as the tire rotates on the road under the weight of the vehicle.  (Yes, it takes energy to bend the tire sidewall – a stiffer sidewall = less bend, and more energy transferred to the road.)  I surmised incorrectly that grip must suffer.  I was wrong.

But now I have to ask:  Why is this technology reserved only for the ECO tires? Stiffer sidewalls are a good thing from a performance standpoint – that’s one reason higher performance tires typically come in lower profiles.  (It allows the suspension to more precisely do the job for which it was designed.)  Is there any downside to making tires of all performance categories more efficient?

…Of course, until people learn to keep their tire-pressures properly inflated, it’s probably a moot point…

Categories: Tires Tags:

Eco-Tires & Eco-Racing

July 3rd, 2009 Comments off

I love tires.  And I love racing.  I especially like the sort of racing that involves both right AND left-hand turns.  Not so long ago, I made sure to watch every Formula1, American Le Mans, Grand-Am, and Speed World Challenge race that was broadcast.  (My wife’s 30th birthday present to me was VIP tickets for the Petit Le Mans – best present ever!)  Unfortunately, I now seem to have much less time to devote to sitting in front of the tube every race weekend…

Of all these series, the ALMS has made the most effort to “go green,” (with involvement from the EPA and DOE).  It started a few years ago, with Audi’s “clean diesel” R10 cars dominating the LMP1 class (and the whole series).  Since then, ALMS cars have raced using E10 and cellulosic E85 fuels as well as hybrid technology.  This year, there’s even the Michelin-sponsored Green X Challenge, which scores the race-finishers based on highest performance with least environmental impact.  (Yeah, I’d love to see the NASCAR folks try to implement a program like this…)  And, yesterday it was announced that the ALMS has even partnered with The Nature Conservancy!

Yokohama Advan ENV-R1Adding to the Green Theme, Yokohama is now supplying the eco-tires used in the Patron GT3 Challenge series (a support series for the ALMS).  This tire (the Advan ENV-R1) is a race-tire that replaces 10% of the petroleum used in the tire’s construction with citrus-derived oil.  The impressive performance and durability characteristics of these tires demonstrate that this technology is applicable to street tires as well.  (Now, I would like to know just how much petroleum is being displaced, both in the tire construction itself as well as from a life-cycle perspective.  Is the extraction of the orange oil and incorporation of it into the manufacturing process any more energy-intensive than the conventional method?)

In another take on eco-friendly tires, NHTSA has recently proposed a tire-rating system that adds fuel-efficiency ratings (in addition to revamped traction and treadwear ratings) to the mandatory tire-labeling system.  Yes, the tires you buy do have an impact on your car’s fuel efficiency!  On the whole, I think this is a good idea; however, one thing does bother me a little.  Tires improve fuel-efficiency for the most part through decreased rolling resistance.  Decreased rolling resistance almost always means less grip.  (NHTSA states that this doesn’t have to be the case, with the disclaimer that higher costs would be involved otherwise.)  And think about it – the only thing connecting your car to the road is the four tire contact patches, each about the size of your hand.  Less grip at the four corners of your car means longer stopping distances and less traction when going around corners.  In an effort to (slightly) improve fuel economy, is it so far-fetched to question if there may be a (slight) increase in traffic accidents?

I wonder how much fuel could be saved through low-rolling-resisitance tires.  Though I haven’t done the analysis, I would guess it would be small compared to how much could be saved if people just maintained proper tire pressures!  And how does it compare with the effect of using orange oil instead of petroleum in the tire construction?  …Yeah, I’m gonna have to figure this one out…