Video: Can Skinnier Tires Increase Fuel Economy?

[jonr]

When you increase tire weight, you increase the rotational energy stored in the tire and you coast further. Ie, you might conclude that some new lighter wheels and tires are worse when they are actually better.

Summary - coasting distance is a poor way to measure rolling resistance.

Newer tires are also worse than old worn tires.

[Miller88]

On my parents' 2004 wrangler rubicon (replaced by 2008 rubicon), we used two different snow tire sets for the vehicle over the 4 years we had it.

The first was 205/75-15 tires. The gas mileage went down (but it was WAY low geared with them) ... but it beat anything to 60mph.

The second set of tires was LT215/85/16 Goodyear Workhorse tires. Much skinnier than the 265 tires that were on it for summer. The winter we used those tires, gas mileage didn't change much at all. Now, it did actually get better mileage, because when those tires were on it was winter and mom would idle it in the driveway for 20 minutes (poor piston rings) before leaving for work and then idle it in the parking lot at work to keep warm. It is a 40 mile round trip.

If I ever owned a truck vehicle, these are the tires i'd get. They have little rolling resistance for the tread.

[whitevette]

Originally Posted by HotRod

This is probably a totally dangerous/unfeasable option, but I was at the Lowes the other day and walked past their trailer tires. 12" just like the metro, but skinny, and a VERY high psi rating. ??? ummm...to bad they were a 5 lug.

Trailer tires are not designed for heavier, high speed operation; ie, unless I miss my guess, the trailer sidewall info will tell you volumes ... all bad! For instance, the load range...is it within your car's range? Is the trailer tire a bias-ply construction? If so, she'll run hot from all that weight and tire flexing ( all tires flex at the tread...it's where the "flat spot", or footprint, starts...and stops).
Short answer...BOOM!

[whitevette]

Originally Posted by dremd

new tires = lots of tread depth = worse mpg VERY TRUE I've witnessed it my self.

Maybe us EcoModders should buy used tires?

There is a good reason why new tires yield lower MPG readings ... it's called "tread squirm". This is requiring energy to do ... and the energy has to come from somewhere. Would you believe gasoline? The effects of a squirming tread can be reduced by pumping up the tire! Hey! Where have you heard this before? The higher pressure firms up the carcass foundation...thus firming up the tread "tower". Result? Stiffer tread ribs = LLR tire!

Regarding Ecomodders buying used tires.... Don't most Ecomodders buy used cars? Then, they DO buy used tires! LOL ( Sorry...couldn't pass this up)!

[whitevette]

Originally Posted by cbergeron

Safety first - but that sounds like a great research idea. I looked at some trailer websites, but all of the wheels seem to be 5 lug.

Most of the wheels that I'd be interested in using are made overseas (so the shipping would be too expensive).

Perhaps there is a reason for the 5-lug pattern ... to keep these tires off small 4-lug car hubs...?

[wagonman76]

Actually, for the most part, trailer tires are designed much heavier than car tires. I honestly havent looked at the 12" tires, but for the 14" and up that I am familiar with, PSI rating is higher, and sidewalls are a LOT heavier. The 14" tires on my camper are rated at something like 1760 lbs each. Try to find a 14" car tire thatll hold that kind of weight. My old 900# trailer had the same tires and I didnt even know they had no pressure once because the stiff sidewalls kept their shape.

The reason for the bolt pattern is most trailers tend to use only a few bolt patterns. The very small ones are 4 bolt. Up to 3500 lb axle is usually 5 bolt 4 1/2" BC, same as Fords and Jeeps and some others.

Trailer tires really take a beating. First of all, the weight. And trailers rarely have shocks. And many trailers have brakes that will lock up so those forces are the same. Only thing different is the cornering forces, but the super heavy sidewalls should handle the forces of a car with no problem, compared to the wimpy sidewalls of passenger tires.

Trailer tires are also usually designed for higher speed operation, at least the smaller ones. Reason is it is turning much faster than the tire of the vehicle that is pulling it at highway speed.

I think they say "trailer use only" because then they dont have to be built to the same safety standards as those for cars.

[aerohead]

My opinion is that while "narrowness" appears to be a condition of LLR tires,it is not a governing parameter.On the second page of the sticky,I briefly addressed MPG as a function of rolling resistance.And perhaps rolling resistance should be the guiding parameter,however it is achieved.--------------------------------------------- The ultra-low rolling resistance tires on Ultralite and PNGV cars by GM were narrow in comparison to "performance" tires.They were also high-pressure(65-psi),cast-elliptic sidewall,low aspect ratio,on larger(18-inch) wheels,to provide a large circumference,with reduced cyclic deflections,and very careful combination of both high and low hysteresis rubbers,to take advantage of those attributes,where they would do the most good.The aspect ratio was compromised to maintain a given air volume without going to a heavier,wider tread ( which would also aggravate polar moment of inertia).Tread block design was also a key to LRR,with many transverse hinges,while controlling noise propagation to meet stringent EPA noise criteria.---------------------------- One ancillary consideration for the "narrow" profile was to enhance the frontal area capabilities of the cars,reducing drag via a "bolt-on" modification.

[Chris D.]

Originally Posted by whitevette

Trailer tires are not designed for heavier, high speed operation; ie, unless I miss my guess, the trailer sidewall info will tell you volumes ... all bad! For instance, the load range...is it within your car's range? Is the trailer tire a bias-ply construction? If so, she'll run hot from all that weight and tire flexing ( all tires flex at the tread...it's where the "flat spot", or footprint, starts...and stops).
Short answer...BOOM!

how old are you?
tires way back when were bias ply..
lots of large trucks had these as factory equipment as well as muscle cars, ect..

[FunkSkunk]

Man! I was hoping by now someone would have come up with a solid conclusion on this debate! Doesn't somebody out there know somebody in the tire industry to answer this question?

[Chris D.]

google is your friend.. try "bias ply passenger tire"

http://www.conti-online.com/generato...istory_en.html