Michelin's Run Flat PAX tire cut-away

For the curious: http://a33…ax.500.jpg

The article (words) that go with the picture: http://www.edmunds.com/ownership/driving/articles/117588/article.html

Thanks for the info - makes me want to avoid them at all costs!

From years of bicycle racing my understanding is tires is the first place to cut weight to improve performance. Given the following quote has there been any study of possible decreased gas mileage in addition to poorer handling?

Heavier tire weight ? Run-flat reinforcements add weight. And it’s all unsprung weight, the bad cholesterol of vehicle mass that degrades ride and handling. In SSTs, this may amount to a few pounds per tire. However, I measured a single 2006 Honda Odyssey PAX assembly at 75 pounds, compared to 50 pounds for a standard Odyssey EX wheel and tire. That’s a huge 25 pounds per corner, 100 pounds per car of added unsprung weight.

Vehicles equipped with Run Flat tires are also not equipped with a spare tire and rim, a jack and a lug wrench, not to mention the additional weight to store and secure the spare. So that total has to be deducted from the increase in weight. The net effect is that even though the 4 tires and rims weigh more, overall the vehicle weighs less.

It seems as though history repeats itself. I remember the captive air tires in the early 1960’s. As I remember, the three seat Rambler station wagons around 1961 came with these captive air tires and had no spare tire. The third seat took up the place where one would normally put the spare tire. I also remember the same discussions of these captive air tires that we now have with the run flat tires.

IMHO,if manufacturers can’t come up with a better design so that there is a place for a spare tire, let’s go back to side mounts or “continental” spares.

It may weigh less, but I’d much rather have that weight in the trunk than spinning around on my wheels and punishing my suspension. And eliminating my ability to find ready replacements when they wear out.

Looks good, but I think these look much cooler and I think they are trully run flat…LOL as their is no air.

I’m remembering some article in Popular Mechanics/Science in the 70s about a run flat tire that had an inner support, like the Michelin, but it was black rubber or plastic with a honeycomb kind of look to it. Anyone remember that?

There are two types of run flats common to the market, the one Kit sent the cutaway of (thanks Kit) and one that mounts on a standard wheel but has sidewalls designed to support the car corner’s weight without air. The PAX tires are extremely expensive to replace and maintain (repair). The others less so.

Hopefully, the latter type will prevail.

Waterboy, as a former cyclist I concur that you’ve made excellent points.

I used to ride my mountain bike through the winter (in NH) on studded tires (home-studded) with flat strips inside. Man, if you want to feel how much of a difference added weight to the rotating mass makes when far from the apex, try that!

My son races on a team in southern California. He also commutes to his full time job 30 miles each way on his bike…most of it along the California coast. Lucky fella.

I wish they’d hurry up and come out with those things

In my opinion anyway, the cons far outweigh the pros.

That roughly 25 extra pounds per wheel is a lot of additional mass to be bouncing up and down and it would appear to me that the suspension components and struts/shocks are going to be taking a proportionally larger beating than normal.

Capri Racer, your math is off.

The Honda Odessey PAX system still adds about 50 lbs to the weight of the van net, assuming a full-sized spare, and 100 lbs of unsprung weight, because a secured spare is considered sprung weight. Still a bad combination.

As any serious bike rider knows, rotating weight has twice the impact on performance of non-rotating weight. Shaving one ounce off of the wheels is as good as shaving two ounces off of the rest of the bike. Adding 100 lbs of rotating weight to a car (or van) is the same as adding 200 lbs of static weight.

You made me laugh. You brought back a memory. I was riding during the years when every part was shaved to its lightest weight. Some of us learned the hard way that untralight aluminum seatposts on mountainbikes were not such a good idea…