Tire width

[1sttruck]

One needs to be careful about what assumptions you buy into when using off-the-shelf solutions to problems. 'Wider is better' may work well on dry pavement within some speed/temp/load range, but wider tires can end up with less traction on wet pavement and other conditions. On wet pavement tires often end up relying upon mechanical 'locking' with irregularities on the road, and a layer of water can effectively makes the road smooth, like at too high of speed where hydroplaning becomes a problem. Wider tires will tend to 'float' more on a layer of water compared to thinner tires, which is one reason why the 'Aquatread' kind of looked like two adjacent motorcylce tires. The thinner tread results in higher normal loads, allowing the tire to make better contact with the road surface. Wider tires these days often seem to have generous, directional grooves for channeling rain, sometimes also with agressive shoulder lugs for other conditions.

I can remember testing how well my motorcycles handled heavy rain with standing water on the road at speed, and typically I was good up to over 80 mph throwing the bike side to side in my lane before I noticed the traction starting to suffer. In SoCal when it rains it's almost like ice storms in other parts of the country, as a lot of people have wide, high performance tires, many with marginal siping and rain grooves.

 

[slugsgomoo]

1sttruck: well, that was a major problem in the past, and is still a problem if you buy bargain basement tires. If you look at something like the BFG KDW/2 tires, you're looking at a very wide, speed rated (Y) tire that is one of the best wet-weather performers out there PERIOD. Of course @ 165/ea they're not terribly cheap either...

The real problem is that people don't buy tires for the conditions they're going to experience. Azenis are great autox & dry tires, but maybe not the best in the rain, for example.

 

[1sttruck]

The KDWs appear to have generous grooving, shoulder lugs and decent siping, both complementing a very good tire compound. Without these you start having problems. As I recall aircraft tires are pretty basic in configuration, like a lot of highway tires on heavy duty trucks, where they're ribbed in order to provide a channel for water. As long as the rib width and depth is adequate they'll do fine in rain. In effect you end up with a set of smaller, adjacent tires.

 

[Mitch Alsup]

quote:

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Originally posted by andrews:
If I was to want to put wider tires on a passenger car (crown vic), what are the advantages/disadvantages to this?

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Since nobody else mentioned this:

Wider tires corner with lower slip angles, and thereby, feel like you have more traction. An unfortunate side effect is that when the car does transition from slipping to sliding the traction lets go much faster--making "catching" the car harder.

Wider tires are more sensitive to camber changes in the suspension than narrower tires, and should be run with slightly smaller toe.

Wider tires on wheels with the correct offset will not change the loading on the axle bearings, nor will these create steering geometry issues. Incorrect offset can increase the axle bearing loads and cause steering geometry issues.

However, simply being wider will increase the effort required to turn the steering wheel as the inside and outside edges are further apart and require higher force leves to counteract the contact patch traction.

Not generally understood is that 16" and 17" tires have sidewall heights that are more optimal for acceleration/deceleration and cornering than 18"-20" tires with ultra low profile tires. The best drag racing tires have rather tall sidewalls so that engine torque can crinkle the sidewalls and deliver a better launch. The best (streetable) max performance tires also have rather compliant sidewalls which help deal with the camber issues and deliver more predictable handling at the limit.

As you get wheels bigger than 17"; the wheels start getting heavier at a faster rate thean the tires get lighter (shallower sidewalls) to the overall package weights more, and takes more energy to accelerate and brake. Taken to an extreme this results in the shocks getting out of synch with respect to the compression and rebound levels required for the original ride characteristics.

Finally, wider tires with more traction can enable the driver to over use the brakes and result in fade issues.