Wide tires the great conspiracy.

[Floordford]

Ive thought about going from my factory 245 wides to 235. But I was told that wider is better. I guess you can run the psi higher in a wider tire because the manufacturer expects it to shoulder more weight. Plus it distributes less weight per square inch.
http://ecomodder.com/forum/showthrea...mpg-17802.html

Originally I wanted thinner tires to kind of cut the air better. I thought the taper would help seeing how the wall would need to stretch out to meet the rim.

[suspectnumber961]

My car came with 205-50/16s...I am moving to LRR tires...specifically Kumho Ecowings. They tend to be a lower weight...narrower tread tire than some of the regular tires in this size.

I like the lower profile tires...on this car they allow some serious cornering for those inevitable emergency situations.

I inflate to 40-42 PSI...so I MIGHT be seeing a +10% gain from stock tires at stock pressures...when I have four LRR tires?

[jamesqf]

Originally Posted by zonker

i guess i should clarify - on a production made passenger car, mounting the thinnest tires possible will help fuel economy but at a huge sacrifice to safety, braking, cornering, and general roadholding.

Again, I have to ask if this has been tested. I can't see it myself. (But since I'm not an automotive engineer & have done no testing, I can't say for sure.) I'd agree, intuitively, that wider tires would have advantages on smooth, dry roads, but how about in the rain? Seems as though wider tires would make hydroplaning more likely. (And if you've ever suddenly found yourself doing 65 mph down the highway, backwards, you'll know hydroplaning is nothing to joke about.)

Similar arguments would seem to apply for gravel, snow, etc. Looking at what's best for Formula 1 cars, which run on a prepared track, is perhaps not the best source of data for general road use.

[Ryland]

Originally Posted by jamesqf

You're sure? Has anyone ever tested it?

As I recall, most of the human & solar-powered vehicles use pretty narrow tires.

The pressure inside of the tire has to be high enough to support the weight of the car with the given foot print of the tire, solar and human powered cars tend to be much lighter weight, my electric car came with 135/80R13 tires stock but it also only has a 1,400 pound curb weight, I weight 250lb and have found that even with 100psi bicycle tires I have to be careful not to go to narrow or I end up creating to long of a foot print with the tire thus increasing rolling resistance.
So tires are getting wider partly because finding a new car that weighs less then 3,000 pounds any more is nearly impossible, but it is also partly for looks.
I would like to see a chart or formula to figure out how wide of a tire you do need for a given weight at a given pressure because if wider was always better then we would all drive around steam rollers.

[d0sitmatr]

Originally Posted by jamesqf

Again, I have to ask if this has been tested. I can't see it myself. (But since I'm not an automotive engineer & have done no testing, I can't say for sure.) I'd agree, intuitively, that wider tires would have advantages on smooth, dry roads, but how about in the rain? Seems as though wider tires would make hydroplaning more likely. (And if you've ever suddenly found yourself doing 65 mph down the highway, backwards, you'll know hydroplaning is nothing to joke about.)

Similar arguments would seem to apply for gravel, snow, etc. Looking at what's best for Formula 1 cars, which run on a prepared track, is perhaps not the best source of data for general road use.

your correct in some of your assumptions, a wider tire *can* be a deterrent in inclement weather conditions, but not always.
case in point, my 99 Ranger XLT as a perfect example.
the stock tires were 235/70/15, and I had serious problems with cross winds, and changes in the road itself, constant swaying and even some curves on the hwy made me feel like I might tip. when it was raining, I continuously hydroplaned, in even the smallest of standing water. I changed rims (but with the same diameter) and put 255/70/15's on it. which helped it a TON in both clear skies and stormy weather (drove through 2 different tropical systems without a problem) not to mentioned increased my cornering capacity by (guessing) 15-20%.
then just prior to trading it, I got even wider, but with lower profile, tires @ 295/50/15's and my ranger stuck to the road like it was glued down, regardless of the weather, not to mention increasing its handling even more, maybe another 20-25% (again, guessing)

my old subi outback, I put aftermarket 17" rims with 215/50/17 tires on it, and I had to fight all the time with it hydroplaning, but then I put the stock rims back on with a brand new set of 225/60/16's on it and it never hydro'd after.

extrapolate from that as you will. but in both instances, going with a wider tire gave me better handling, both in clear and stormy weather conditions.

[mort]

About hydroplaning, tread design and depth may matter. Hydroplaning occurs when the pressure of the wedge of water is greater than the pressure required to deform the tire. Various tests have show that the critical speed (in mph) is 10 * (psi)**1/2.
-mort

[Varn]

As far as safety narrow tires have superior adverse weather traction in my experience.

In the 70s we used to go to the sports car ice races on the big lakes in northern Wisconsin. I was weird seeing the performance cars out there on the 1-2 mile ice tracks wearing extremely narrow tires. It influenced my thinking on vehicle traction my entire adult life.

In bad weather you want to stay at in contact with the tarmac, wide tires inherently will have more frontal area and will plane quicker. If your tire is 8" wide you have a larger potential for hydroplaning than if you have a 4-5" tire.

The trick with a narrow tire is that some of it will stay in contact with the road when the leading edge is planing.

I used to have a 1969 Renault 10. It had great all weather traction and wore 135x15 Michelin X tires. Later I had similar great luck with a 1978 R5 which wore 145x13.

Good handling is not a problem with dry roads. Even my Econoline is safe driving with the stock 235x16 tires.

Bicycles are resistant to hydroplaning because of their high pressure and narrow design. I only had one instance of hydroplanning with it. I was in a 30+ cross wind on a rainy day near the end of a century. I could only go 12 mph before it would skate sideways.

[tjts1]

Originally Posted by diesel_john

IMHO wide tires have cost consumers billions of dollars unnecessarily. In fact i would go so far as to call wide tires a conspiracy. With all the money spent on vehicle control from 4WD to stability to compensate for wide tires being worthless in poor traction conditions when it really counts. The only reason cars are safer is because they crash safer. People will drive in over their heads no matter what controls are on the vehicle. Wide tires increase the difference in traction between dry road and poor conditions, thus causing the public to be lawed in to a false sense of security. IMHO

What you fail to realize is that wide tires reduce the difference in traction between wet and dry roads. Try slapping some 185 wide tires on a new camaro and go drive it in the rain.

Originally Posted by Varn

I used to have a 1969 Renault 10. It had great all weather traction and wore 135x15 Michelin X tires. Later I had similar great luck with a 1978 R5 which wore 145x13.

You forgot to mention the 1100cc engine pumping out 40 something HP in a 750kg car. We don't drive tin cans like that anymore. I had both an R8 and R10.

[Varn]

tjt Obviously you disagree that wide tires amplify the difference in wet and dry traction. It is easy to handle a vehicle when running on dry pavement. The challenge begins with rain and then gets worse in snow and worse yet on ice.

I would say that the R10 is about what a lot of drivers here have. Particularly considering the 40 years since then. As you say "tin cans" , no argument, they are small and built with lighter weight parts.

My vw diesel is somewhat similar to an R10. A 2300 pound car with 65hp.

I was holding my breath last Sunday night as by the grace of God, I missed a deer while stopping for another.

Originally Posted by tjts1

What you fail to realize is that wide tires reduce the difference in traction between wet and dry roads. Try slapping some 185 wide tires on a new camaro and go drive it in the rain.


You forgot to mention the 1100cc engine pumping out 40 something HP in a 750kg car. We don't drive tin cans like that anymore. I had both an R8 and R10.

[Thymeclock]

Originally Posted by zonker

i guess i should clarify - on a production made passenger car, mounting the thinnest tires possible will help fuel economy but at a huge sacrifice to safety, braking, cornering, and general roadholding.

True. Wider tires give better handling and cornering capability. That makes the car safer if it responds better in avoiding a collision. (I would expect that those who are primarily concerned with or obsessed with fuel economy will be dismissive of that aspect. If you call wide tires a "conspiracy" that shows a certain bias.)

Hydroplaning has relatively little to do with the width of the tire and is much more due to tread design. You can find both wide and narrow tires that are prone to hydroplaning. Usually you get what you pay for. I prefer to avoid tires that are poorly rated, especially if they have poor wet traction.