FuriousDonuts

We all know wider is better in the dry and narrower is better in the snow (all things in moderation of course). What about rain tires? In racing conditions, with a rain tire like the Hoosier H2O, is it better to go wide or narrow?

My initial thoughts were that a narrow rain tire is preferred in order to reduce hydroplaning. But, rain tires already have tread designed to pull the water away. If the tread is indeed effective, wouldn't it be better to increase the contact patches on the asphalt?

Open to thoughts/discussion.

rithsleeper

I only race spec classes so I dont have a choice, However ill tell you a 275 is too wide. Even brand new rain tires cant dissipate the water quick enough. Especially at 140mph... if im at a track day with my vette ill use street tires for rain and its better than nothing but I know my rx7 can cut the water so much better on 205's. Night and day between the two.

Hi Volts Z06

Rule of thumb is one or two sizes smaller than your dry set up. On my C5 I run a 335 rear and 315 front set up. For rains I run 305 rear and 275 front. Oh....and FYI.... this just happens to be the two largest sizes that Hoosier makes in the H20's.

brkntrxn

FYI - 305 Hoosier Rains are wider than a 315 Hoosier R6/A6 when mounted on the same wheel. Keep that in mind.

Rob31

At Gingerman last year I was 6 average seconds faster on a 315 A6 than a 3 year old 275 Kumho XS had tread ,but heat cycled allot in the rain .my best lap was 12 seconds faster ,but it quit raining for about 40 minutes . one lap AX, no warm up
Point being compound is more important than size

Hi Volts Z06

It's probably prudent to mention a few things for the purpose of this discussion. When it comes to rain tires it's compound that's more important than tread pattern. That being said rain tires are made to operate at a temperature of about 105 degrees. This is the reason that a rain tire that gets run on a dried out course will be garbage in just a few laps. I wouldn't be so hung up on size. I would be more interested in hearing other drivers opinions regarding what brand of rain tire they prefer. I have only run the H20's from Hoosier once and really can't complain since I won that race...lol.

0philstireservice

Narrower is better in the rain - period.

Hi Volts Z06

And on that note....it was Phil who sized and sold me my Hoosier H20's and the rims they are on!

fatbillybob

Phil,

If running 295's dry what is your wet rec?

0philstireservice

Are you running 295 all the way around?

If so, then 275's all the way around.

If 275 front and 295 rear the above will work also.

Most Vettes run: below is the most popular and preferred set up.

Front - P275/35R18 46215 10.0 25.2 79.2 10-11 9.5 11.3 $341
Rear - P305/30R18 46220 11.8 25.6 80.4 11-12 11.0 12.7 $376

There are 1 or 2 other setup options also depending on what you run in the dry.

troyguitar

Period as in 195's are the way to go? 315 dry, 195 wet?

FuriousDonuts

Sent a PM.

fatbillybob

Many if us is Socal us our rains so infrequently that we never wear them out. Are there general lifetimes of rains like we want fresh rubber for dry tires? Are rains really only competitive in the season they are purchased vs. left lightly used into the 2nd and 3rd season? Anything help for longer life? bagging them out of the sun? tire softeners liquids before use?

What is the degradation of a rain tire? Does it heat cycle out? 1/2 tread means it's dead? Can you breath in more life with custom siping?

0philstireservice

Oh yes - let me know how that works out for ya...

troyguitar

YOU are the one who said it. I've never run one of these cars in the rain at all and was genuinely interested to hear the experience of others...

Narrower is better period means exactly that, bicycle tires are faster than Hoosier H20's in 305 wide.

What did you mean, then, if narrower is in fact NOT better PERIOD?

Is a 245 better than a 275? 215 better than 245? 195?

Obviously there is a line, however those of us who do not own tire shops have no cheap means of finding that line - hence this thread. If you do not wish to contribute, then fine.

Black89Z51

I'm pretty sure he contributed a good bit to this thread. And obviously you are going way overboard with your bicycle tire statement. There is a point where a tire is too wide and doesn't allow enough time for the water to escape and causes a hydroplane effect. So you have to balance that with contact patch, which more is better. Pretty sure Phil gave that to us in his 2nd post.

0philstireservice

I didn't know I had to state the obvious.

Trust me I have run many cars in the rain -

To spell it out - The narrower the better means this:



In the rain, the less precipitation you have to push out of the way the better the car will handle. Hence why we don't use the wide tires in the wet as we do in the dry.

Now with that said, there are certain rain tires that can evacuate a lot of water in a short amount of time and are still the same size as the dry tires. These are high dollar wets and not necessarily available in this country. Also, even with the ability of these tires to dissipate a great deal of water in a short span of time many race teams still run the narrowest tire that will still handle the weight of the car as well as handle well in the wet conditions.

It comes down to testing testing testing !! Which cost money money money!!

BryanPendleton

So what kind of rain are we talking about? A good Texas rain storm or an April shower in Ireland? Having no practical experience with rain tires and only mechanical engineering experience to fall back on here are my thoughts:

Tire Temperature
The key with choosing any tire is making sure you operate the tire at its optimum temperature range. Too wide of a tire and you may not be able to get the heat into the tire. Too narrow and you may put in too much heat. In the rain, well that water will suck to heat right out of the tires, so a rain tire will have a compound that will operate at lower temperatures.

Water Evacuation
Another variable that must be considered in rain is can the tire evacuate any standing water. Based on speed, weight on tire, water depth, thread patterns and other variables any standing water much be evacuated from the contact patch otherwise the tire will skate accross the top of the water offering negligable traction. You can improve water evacuation by running narrower tires, over inflating your tires, reducing your speed, avoiding deeper water. Th tread pattern will also play a big role in the tires ability to evacuate water. Note that the same variables that tend to improve water evacuation, actually increase contact pressure and thus potential for heat in the tires.

Choosing
So ultimately its up to you to perform lots of expensive testing or you can talk with those with experience in rain racing and find out what they used and in what conditions it was used. Make sure you ask detailed questions, not just what tires they are running. Ask details about the conditions the tires were used in. Details about the vehicle they were used on. Tire pressures? Temperatures they were measuring if available? Data and more data. The more data you have the more educated of a decision you can make.