Mixing V and H rated tires?
 

I currently have 4 Micheling MXV4s which are V rated. One of them had a slow air leak and before I noticed it, it wore along the sidewall. Since the other 3 tires are good but have worn ~30%, I cannot replace either one or two of them with new tires. I have been looking on Ebay for used ones but the only ones available are H rated. Would it matter much if I installed 2 H rated tires and kept 2 V rated ones?

Thanks,

Matt

IMHO I would not mix any tires, tread, wear, or rating. In the long run, it just isn't worth it. :)

I'm with Earl, I'd advise against mixing any tires on an AWD vehicle.


4 new tiires now.....or a new tranny later:eek:

a possible minority opinion....
 

As to tranny wear and tear, I suspect the biggest issue is rolling radius. More on this later.

First: I certainly wouldn't run differing tires side to side. That said, H & V rated tires will have differing handling characteristics because the primary difference (as I have been lead to believe) is sidewall stiffness. So on this basis I believe you could mix speed ratings front to back as long as you were ready to deal with any induced handling quirks.

Now to rolling radius: A stiffer sidewall nominally means less generated heat (but under what conditions?). The size of the tire is a function of both static pressure and of heat expansion. I found the OEM difference in air pressure just didn't work for the Fulda 225x50x16 Z rated tires I'm currently running. I must use an 8PSI difference to get the same rolling radius front to back. I have casually checked hot and cold radius and it seems consistent - and the tire does grow, forget now but I seem to remember about 1/8" growth in radius from heat. Since the H & V tires will likely heat up differently, the rolling radius may not stay consistent, and thus induce AWD issues from size changes. This would argue against mixing speed ratings; however, the real issue is just how much difference, i.e., 5% or 0.05%.

mbtoloczko & I have exchanged a couple of PMs on the issue and I plan a few tests to see how static measured radius differs from physical rolling radius over a variety of cold/hot conditions. mbtoloczko measured a one-time/one-temp difference of only about 0.12% (given static radius was checked and pressure adjusted first) between static and physically rolling the car.

I have no access to tires with different speed ratings, but if some folks (and hopefully with several different brand and speed ratings) would be willing to check and report cold vice hot radius I could add it to a table I plan to build. (However, first I need to find time to replace the old worn out rear struts with the new units sitting in my garage). If you're going to contribute I'd like to suggest a common measurement system: measure from the road surface to the top edge of the wheel (not the top of the tire) and make sure the tire is pointed straight ahead and not side loaded (from parking on a hill or???). This allows one to sight through the center of the wheel axis and hopefully increase accuracy vice trying to figure out where to determine the middle of the wheel.

So what am I trying to say???? I have in the past employed a different brand & size tires front to back on 2WD vehicles with no issues aside from the previously mentioned handling issues. Not really recommended but when $$$ are tight....I have no idea how differing speed ratings affects tire rolling radius - I suspect not much at US legal road speeds and moderate corning demands. But frankly I don't know. If money demands are such you have to follow this route, I would pay particular attention to the rolling radius of the tires, cold, city driving warm, and highway hot. I would also put the higher speed rated tire on front as it encounters a greater load.

Hope this helped. :)

Also hope that if I have made a conceptual error someone will be kind enough to point me in a better direction.:confused:

Lee

So, the informaton you want is the road surface to the top of the wheel, front and back. Hot, warm or cold. Size and rating of the tire, brand and model. Anything else? :) Do this for the different temps and PM you with the figures. :)

I realize I'm asking for a bit of effort, but YES, that is what I'm asking for. I'll gladly take partial readings as some data is better than none. :)

For anyone reading out there...if your front to back radius as measured isn't the same, you need to adjust either the front or back tire pressure until they are the same. Said another way, if the tires measure different, then that's the same effect as if you bought different size tires.

Thank you Lee. This clears up a lot of confusion for me anyway. I will try to get several reading for you on different brands that I have. :)

Depending on how tight $$$ really is, how long you expect it to be that tight, and what kind of conditions you generaly drive in (as well as how aggressive you normaly drive) You may want to consider just buying 4 "cheap" tires, keeping the other 3 XV4's till you can replace the one bad one. At least this way you have 4 tires with the same tread, and rating.

That still is a bad situation. All 4 should be replaced at the same time. Having 3 worn tires and 1 new one can be a real problem.

True enough if the other tires are really worn, but given that he said the tires are only 30% worn, and it seems he's guessing so they could be less, it MAY not be that big a problem. However that said, if they are more then 30% (but less then a true 40%) worn, at the very least, I'd buy 2 new tires keeping the one, out of those replaced, that is in the best shape as a spare.

It looks like I found some V rated tires that should match the wear of what I currently have. I will replace one pair, and keep one as a spare in case another tire needs to be replaced.

Thanks for everyone's feedback.

Matt