Just replaced the outside rear tires due to "weather checking" and not an hour went by that I was told the inside tires will get torn apart because they aren't the exact same diameter as the new skins. The insides are in great condition, and I could put them on the same side, and put the new ones on the other. At over 250 a skin I'm trying to conserve bucks but need to get down the road too. Any help will be gladly accepted.

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Dan & Suzy Z
'81 Euro 28

Define "not the same size" Do you mean they are actually a different size or, the inside ones are more worn down?

This site might help answer your question.
http://www.miata.net/garage/tirecalc.html


[This message has been edited by eric (edited September 15, 2004).]

They all are 8x19.5 and I couldn't measure more than 1/4 inch difference in diameter. Straight edging inside to out looks pretty good but there could be a 5 degree or so offset.

Danny, measuring the circumference is much more accurate than diameter. The manufacturers' spec sheets will also tell you a lot. There can be variations from brand to brand within the same size. How close to capacity are the old and new tires? The greater margin, the less of a concern.

Another major consideration will be temperature. May I suggest buying or borrowing a laser heat reading gun? They are under a hundred, and can be quite useful for checking tire temps as well as a lot of other things. I "shoot" my tires at every stop. Crossing the Mojave so often has made me a paranoid tire checker. Lots of dead alligators there. I shoot my brakes after every steep downhill. (Actually, I get out, kneel, kiss the ground and offer a prayer of thanks, too) They will detect a dragging brake long before you would know it otherwise, for example.

What are your other tires? How about putting the new ones up front? I would like my best tires on the front, regardless. My modus operandi is to put new on front and move oldest to the tag axle.

BTW, were your outside dual tires weather checked just on the outside? How old were they?



[This message has been edited by bill h (edited September 15, 2004).]

DO NOT TAKE CHANCES WITH TIRES OR BRAKES! BOTH CAN RUIN A GOOD OUTING OR VACATION IF THEY FAIL OUT ON THE ROAD.. I KNOW--I SPENT THE 4TH OF JULY IN THE MIDDLE OF A COTTON PATCH,IN HOT CENTRAL TEXAS, WHEN BOTH RIGHT REAR TIRES BLEW, AFTER CROSSING OVER A RAILROAD TRACK. COST US $750.00 AND DOWN TIME OF 6 HRS(HOLIDAY RATES) THATS WHEN THE IRRIATE WIFE SAID SELL THE BARTH!!! WE DID AND BOUGHT AN AIRSTREAM. AIRSTREAM SAYS REPLACE TIRES EVERY 5 YEARS.(I HAVE) IF THEY BLOW OUT IT CAN TEAR UP MORE THAN COST OF NEW TIRES...GOOD INSURANCE!! I STILL MISS THAT OLD BARTH.--BUILT LIKE A TANK.

Bill, I checked the circumfrance with a string and they are pretty close. The old Michs were great treadwise, but the checking bothered me. Especially when I took off the spare cover and saw a six inch rip in the sidewall of a Mich that looked exactly like the ones on the coach. Don't know about the other side because I neber got a chance to see them. I'm checking in to a heat gauge, which sounds like a good investment. Thanks for the advice.

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Dan & Suzy Z
'81 Euro 28

How close to capacity are the old and new tires? Has each wheel been weighed? The greater the margin, the less of a concern.


BTW, were your outside dual tires weather checked just on the outside?

How old were they?



Age can be an issue. The more a coach sits, the shorter the tire will last. Mine gets a short drive once a week. I retired some tires that were 9 or 10 years old, with nary a crack. Tire rubber has a preservative in the mix that goes away when exposed to air. Driving causes flexing and heating which causes the tire to "bloom", a word used to describe the movement of new preservative to the surface. In addition, sitting causes flexing in just one spot for a long time, which can fatigue that spot, both rubber and sidewall ply cord. Over the road truck tires last through several recaps and many years because they don't sit much.

Re: Rips & weather checking on Michelin tires. - I had a set of Michelins on a GMC f.w.d. motor home some years ago. The previous owner spent a fortune trying to solve a vibration problem that began when he installed the tires. It still vibrated when I bought it. Turned out to be a belt that had shifted on one rear tire. Apparently the problem was there when the tire was new.

I drove the rig for two years. One winter we were in a condo in So.Cal., while the rig reposed in storage. I checked it once a week, and noted a spot of missing tread the size of a pencil eraser on one rear tire. I thought I'd run over something that gouged it out, but each week it seemed to grow larger. Finally, the tire self-destructed while sitting there, gashing the fiberglass fender skirt when the side plies separated from the bead.

The tires were five years old, with about 80% tread. No weather checking, no other signs of age or damage. Michelin said they were out of warranty.

My opinion of Michelin tires since then, is like Bill H's opinion of all French products.

The GMC wore Bridgestones when I sold it. A couple truckers have told me that Toyo is the way to go nowadays.


[This message has been edited by olroy (edited September 16, 2004).]

I am certainly not a tire experted but I had the same problem as Olroy on a conversion van. A tire dealer just transferred the offending vibrator to the rear where it blew in the driveway. I have Bridgestones on my Regal, but have also heard good reports on Toyo's but the name reminds me of Pearl Harbor.

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quote:

Originally posted by olroy:

My opinion of Michelin tires since then, is like Bill H's opinion of all French products.

Well, not quite. I love certain Laguiole knives and corkscrews, and the Pierre Jadot French wine from Costco.

But back on subject, my previous SOB came with almost-new Michelins. Present owner found bulges in several sidewalls within two or three years of purchase. Natch, they weasled on warranty, said they "must have been run low". Previous owner was a UPS OTR trucker who was meticulous about tire pressures. He and I now have Bridgestones. Happy campers so far.

Bill, I'm not sure what you mean by how close to capacity and margin. The fronts were new in May and match th new rear outsides. They are all BS. The rear insides are Michs. I've also talked to a bunch of truckers who swear by Toyo.

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Dan & Suzy Z
'81 Euro 28

Might want to look at the tire ratings at www.nhtsa.dotgov. Look under utqgs.

I too don't have much love for Michelins. I blowed the sidewall out on a stepdeck that had more than half the tread left on it. B.S. for me . When my brothers new Pete came in, he told them if it didn't have B.S. don't call me! I always put drive tires on 4 at a time. You want both sides the same circumference. If not its hard on differential. Also road heat makes tires grow in size.

Danny, each tire manufacturer has a max load it can carry at a stated max pressure. It is usually marked on the tire. The farther you are under that capacity is the margin. One could consider it a margin of safety. Most manufacturers have a spec sheet that lists a tire's load carrying ability at a particular pressure. I like to weigh each corner and inflate a little above that weight.

If you can't find a chart for your brand, a Tire Guide should have a generic chart for the size.

OK!! I'm convinced! When I get the Euro back from getting the new fridge installed it's going straight back to the tire store for new inner BS's. Then they'll all be new and I don't have to worry about that anymore. I will have to worry about the 5 notes it'll cost to do it but at least I'll know it in advance and not in the middle of Podunk Al. Thanks to all for your advice.

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Dan & Suzy Z
'81 Euro 28