tires------again

[Jeff Miller]

Why would you need a "stronger" sidewall? Driving through
construction sites with a load of gravel? City bus service rubbing
curbs? Stiffer/thicker is not always better. In fact from an
engineering standpoint, the flex/strain has to be distributed over as
large an area as possible for good tire service. The
Michelin's "soft" sidewall flexes over its entire surface avoiding
the stress-riser effect of a stiff sidewall which will flex more at
the tread/sidewall junction where a "zipper failure" is so very
common.

I'll take the Michelins. Air holds up the coach, the sidewall holds
in the air. My last Toyos lasted 23months (from DOT sidewall date)
before I took them off due to sidewall cracks.

I know that there is a lot of opinion regarding tire manufacturers,
but my personal experience has been that I have had failures and
trouble with every brand that I have owned on a 'Bird (Toyo,
Bridgestone, Goodyear, Firestone, Dunlop) except for the Michelins. I
am including BFG tires made by Michelin in the latter group. I have
had more than twice as many Michelins as all other brands combined,
and the Michelins were often original equipment and up to 23years old
when I buy the coach and some significantly cracked. Still, it is the
younger and non-cracked SOB tires that blow out on my way home (5 to
date) not the Michelins. The Michelins also enjoy being more
desirable when selling a coach, and worth more at trade-in time at
tire dealers as (according to my dealer) they retread very well and
truckers like the long service life (7 years / 700,000mile warranty
for the XZA-2 in truck service). Michelin is standard equipment on
most high-end trucks, buses, and RVs.

If the Michelins are a good deal, I'd say buy them. I'm not
discounting the value of saving a buck on a less-expensive product,
but I'm a bit of a safety freak and don't skimp on tires.

As far as tire life and failures, I will go on the record as saying
it is not the age, but the condition. Age does affect condition, but
if the tire is treated well and in desirable conditions it will last
significantly longer and age more slowly than if in agressive
conditions and not properly cared for.

Good conditions: Cool, Dry, inside or protected from light (U.V.)
which includes protection from some inside lighting, low ozone (not
next to a welding station or brush-type motors for example), isolated
from concrete (I prefer HDPE cutting boards from Sam's Club, double
as leveling pads) or other ground, cleaned frequently with soft brush
and mild soap-and-water, kept properly inflated (or higher when
parked), not run over speed or overloaded/underinflated, high-temp
running might require more air pressure or less speed. Supporting the
coach with leveling jacks might also help the tires.

Less desirable: High sun load outside, higher temps accelerate aging,
Ozone exposure, run hot/overloaded/underinflated, parked for extended
periods without isolation from concrete etc., infrequently cleaned or
treated with a tire dressing that is not compatible with the tire
(most tire mfgrs suggest no tire dressings) and damage from
curbs/road hazards (I'm likely missing something here).

My tires have typically been on a coach in west Michigan (near zero
direct sunlight, moderate to cold temperatures) under trees at my
house on pads, weight on leveling system, inside when not-used for
extended periods, tire pressure correct, cleaned after every trip,
never overloaded or underinflated, driven more slowly in hot road +
weather) and tend to last a long time. My first set of Michelins were
a little over 10years old when I sold them to a busnut, no cracks,
got $100/ea and he was very happy. After replacing those with
Dunlops, then Goodyears, I went back to Michelin for the more
desirable effect of round tires ;~)

If you don't know the tires' history, it is difficult to determine
whether they have ever been run overtemp (usually from
underinflation). If the tire has ever been overheated, its life has
been significantly decreased and it can fail without warning. The
tire will begin to delaminate internally, leading to the classic
tread separation or a "zipper failure" where the tread leaves the
casing or the sidewall. This cannot be detected externally but most
tire dealers can tell you what happened in the post-mortem if you
still have enough tire. Overheating sometimes leaves a tell-tale dull
stripe near the base of the tread, but not always.

Some of those among us "snow birds" types who travel south and north
a bit notice how much rubber you dodge on the southbound freeways as
the weather warms up. Marginal tires get to warmer roads and warmer
air and overheat, eventually failing. The same stretches of highway
northbound usually have far less "gators" (tire-tread strips).

What I read about two years ago regarding a study of truck-tire
failure (the 11Rx22.5 is a truck tire) is that the most common
failure of these tires including retreaded ones is
underinflation/overloading. Look for an inflation guide for your
tires (Michelin has one on their site, Toyo did also when I had my
Toyos, probably still does, Bridgestone/Firestone does). Inflate
tires to the worst-case loading (weigh each tire position, remember
the effect of full vs empty tanks, especially on rear-tank coaches
like the FC where the front axle is heaviest with empty fuel and
water, full waste). Dual tires should be same
size/construction/wear/inflation in a pair. Check the speed rating of
the tires (most are 75mph, some older tires are 65 like older XZE
tires, so an additional 10psi might be required for 75mph travel per
MFGR information). Stop on hot/sunny days and check the sunny-side
tire temperature, ... without a temp gauge you will notice that a hot
day will be enough to make your hand sting when touching the
sidewall, slow down some. There is a matrix: Heat comes from tire
flex. More flex comes from more load. More air pressure reduces flex.
Localized flexing (too stiff a sidewall?) can cause localized high-
pressure and fatigue or delamination. More speed, more load, less
pressure, hotter road, sunlight, all cause more heat. Less speed,
less load, more air pressure (within mfgr guidelines) will reduce
tire temperatures.

Sorry to be long-winded, but I feel that posting a couple of
website/urls of tire guides tells part of the story only. Similarly,
telling people that any tire in any application is good for X number
of years from DOT date is also not IMO useful. Well-kept high-quality
tires with a known history have run my coaches for many years, I have
been able to inspect the inside after dismounting them, even used 20-
year-old Equal over in a new set of tires at a tire dealer's
suggestion. Treat tires well and they'll treat you well. Abuse them
and don't expect even 3years out of them.

- Jeff Miller
http://www.wanderlodge.net
http://www.millercoachworks.com


--- In WanderlodgeForum@yahoogroups.com, George Lowry
wrote:
> Dan,
>
> I paid only $2700 for 8 Toyo 12R22.5 tires that were brand new -
> manufacture date less than a month old. And the Toyo has a
stronger
> side wall than the Michelin...<<snip>>