best tire width for wet roads

All other factors being equal, a narrow tire will have less tendency to hydroplane on wet roads. There differences between static friction, dynamic friction, and the tendency to hydroplane. When most people talk about wet performance of a tire, they are thinking about hydroplaning. To avoid hydroplaning, a tire has to push water out of the way without lifting off of the road surface. A narrow tire has less planing surface and a higher loading, so it is less likely to lift.

Tom

 

<div class='quotetop'>QUOTE(qbee42 @ Oct 25 2007, 03:01 PM) [snapback]530382[/snapback]</div>

Hi Tom,

I agree with you re greater likelihood of hydroplaning on wider tires (I think back to the only times I've ever seriously hydroplaned in my life, they were when driving sports cars with very wide tires).

I was wondering what you thought about narrower versus wider tires for (1) wet braking, and (2) wet driving traction short of hydroplaning conditions (if that makes sense)?

Thanks in advance.

 

<div class='quotetop'>QUOTE(Boo @ Oct 25 2007, 03:31 PM) [snapback]530397[/snapback]</div>

These are tougher questions, as friction is a slippery topic (sorry for the pun; well, I'm not really sorry, or I wouldn't have used it in the first place.) Let's look at some of the factors involved with tire traction:

1) If we were dealing with ideal materials, the width of the tire would be irrelevant in relation to traction. The reason for this is simple: If we have a wider tire, then the tire has more surface in contact with the road, which would make you think it should grip better. On the other hand, the pressure (psi) pushing the contact surface onto the road is reduced, since the car weighs the same but you have a larger contact area. In the ideal case, these two factors cancel each other.

2) In the real world, contact surface has an effect. One is surface loading. A larger tire will have less pounds per square inch (psi), which is good if you are running a dune buggy over sand, but bad if you are trying to dig down through snow and slush, or push water out of the way.

Another factor is surface deformation. Too much force and you will burn rubber, or peal away the road surface. A larger tire spreads the force over a greater area. This is the reason race cars and dragsters use large slick tires. It is also the reason race cars and dragsters don't do well in rain. Racers are willing to burn away a fair amount of tire for an increase in traction. This is done at the expense of tire life.

3) Looking at 1 and 2 above, what we have are two incompatible forces driving our tire choice. No one tire or tire width is best for all conditions, which should be obvious when we look at the variety of tires available for ordinary cars.

So what's the answer to your question about wet tire performance? There is no one hard and fast truth, but we can narrow it down a bit. If we stipulate, as you did, that we are not dealing with hydroplaning conditions, then wider tires should allow more ultimate traction for driving and braking, due to their ability to spread the forces over a larger area. However, there is the very real possibility that the higher forces on a narrow tire would better dry the contact area and therefore provide more driving and braking traction. I believe there are too many variables to allow for one solid answer.

Tom

 

Thanks Tom (qbee42)!!!

I really appreciate your taking the time to explain this, and explaining it so well.

-- Tom (Boo)

 

<div class='quotetop'>QUOTE(Boo @ Oct 25 2007, 04:02 PM) [snapback]530479[/snapback]</div>

You might try spending some time on tirerack.com. They have good articles on tire tests in wet conditions. Here is one:

http://www.tirerack.com/tires/tests/chartDisplay.jsp?ttid=60

 

Karen,
If I were you (living in a rainny area), I would focus more on the block pattern of the tire I choose than the width.
tirerack.com is the resource you may use to choose the best tire to fit your need. There are also user survey and
review on any specific tire. I usually choose the top 5 in rating and pick the lowest price among the 5.
If you choose the OEM size, Costco might have the best deal since they mount them for you (and with $60 off now).
If you change to a different size, try tirerack.com or discount tire for best deals.
I live in CA, I am going for 205/60R15 high-performance all-season, when the time comes.

 

<div class='quotetop'>QUOTE(Grdn2 @ Oct 26 2007, 01:02 PM) [snapback]530748[/snapback]</div>

Hi Karen,

Yes I don't think the extra 1/4" (10 mm) will make much difference.

That said, here are some reasons (whether they're good, I don't know) for going with the 195 over the 185 size:

* Generally slightly better handling and braking.

* Slightly better looks - the 195s seem more proportionate to the size of the Prius. (Note that 185 is the narrowest width offered by Michelin for the Hydro Edges.)

* 195 is the standard width for the Touring Edition, and the standard width tire for the Prius sold in much of the rest of the world. Some here have argued that the Prius was made for the 195 size.

* I think there are a lot of PriusChatters who are very satisfied with their 195 size Hydro Edges or Goodyear TripleTreds (very similar tire), and report that their wider HEs or TTs "stick like glue" in the rain.

* * * * *

I wish there was a publicly available tire test of the Prius comparing the 3 widths commonly used by Prius owners -- 185, 195 & 205 mm.

 

A big factor in wet-weather performance is how fast the tire can evacuate water underneath it. That's what a wet-weather tread design is optimized for - getting the water out from under the tire and out to the sides as quickly as possible. All other things equal, the shorter the distance the water has to travel, the faster it can evacuate water, so a narrower tire should have a slight advantage (shorter distance from center of tire to the side). However, I think it's a safe assumption that tread design has a much greater effect on how well water is evacuated, so that extra 5mm of distance (half of the 1cm difference in tread width) probably isn't going to make a difference. Choosing the tire with the best tread pattern and compound for wet weather grip will make much more of a difference.

 

Let me make this simple: I have Hydroedge's in the OEM size and they stick like glue in the rain, and work well in the snow, and reasonably on ice.

Nate

 

<div class='quotetop'>QUOTE(Grdn2 @ Oct 25 2007, 02:20 PM) [snapback]530359[/snapback]</div>

Think of it this way. Narrow on dry,snow and water...wide off road & Mud. You'll love the Hydro-Edges.

HarryB

 

I put the 195/60 R15 Hydroedges on my Prius, and I love them.
I live in an area that has rain that can be described as "driving through a car wash"... or worse.
The Hydroedges are the best. The little bit extra width just helps the car feel a tad more stable. That's subjective, but it's my subjective