Re: [ST] Tire Pressure on a Worn Rear

[Craig Tate <craigtt@xxxxxxxxxxxxx>]

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Blake,
I'm going to try to be tactful in my response to your post to avoid a 
flaming war, but I want to tell you up-front that I thought your comments 
tended to be more of an attack rather than a well reasoned or supported 
argument.  I was somewhat take aback by your post and immediately re-read 
my initial post to see if I had said anything to warrant your 
approach.  Frankly, I didn't see a problem with what I wrote - I was 
offering an opinion, my intent was not to present a formal, documented 
argument.  And, I certainly didn't direct my comments at you.  That having 
been said, if you found my initial post offensive, I apologize.  That was 
not my intention and would not further the interests of this list.

But, as I focus on your rebuttal, I find it uncompelling and 
unsupported.  In fact, when I read your citations I had to wonder if you 
actually read and understood them as neither addressed the issue under 
discussion.

At this juncture, let me also say that I responded to STeve through the 
list, in a separate post, clarifying my position.  You may want to read 
that post prior to proceeding here.

As we both found, the Michelin's and Dunlop's motorcycle tire specific 
pages don't substantially address tire wear from over or under inflation, 
but check out Michelin's main page for a neat online tire diagnosis 
(http://michelinman.com/mastapp/servlet/Controller/site.care.MainPage). 
This is under the Car & Truck tire section, but there is no reason to 
believe motorcycle tires behave any differently (or bicycle, go-cart, 
golf-cart tires, etc.).  Many other tire manufacturers have similar 
pages.  If you doubt this basic premise, it's not likely I'd be able to 
change your mind (or care to, for that matter).

I found your documented citations to be interesting.  Let's look at the 
first one a sentence at a time.

1. But the most important factors affecting tire life is controllable by 
the rider.
I agree with this, but it doesn't support either of our positions (i.e., 
it's not relevant to the discussion).

2. The number-one factor that leads to premature tire wear is underinflation.
This sentence addresses "premature" tire wear.  The scenario under 
discussion presented a tire near the end of its useful life due to normal 
wear, with a worn center section but tread on the margins of the tire.  We 
had no indication the tire had been under inflated and I did not suggest 
George ride the tire under inflated.

3. Mike Manning travels to motorcycle events around the country with the 
Dunlop Tire Inspection Crew.
Nice job if you can get it, but not really relevant to our discussion.

4.  They provide tire care and free tire inspections to all motorcycles.
Nice guys, but again ditto regarding the relevance.

5. He tells me that 85% of all tires that they check are underinflated.
Did he check George's tire?  Did anyone tell George to run his tire under 
inflated?

6. Not only is that dangerous for the bikes handling, but it can shave 20 
to 40% off the tires life.
Again, I'm not suggesting George ride his bike under inflated.  I do agree 
that in a general sense, riding an under inflated tire will reduce it's 
lifespan.  However, that's not the issue here.  The issue is whether 
reducing tire pressure slightly in "George's specific situation" (thin spot 
in center of tire) would allow him to gain a few additional miles on the 
tire.  My explanation of enlarging the contact patch (in the post to STeve) 
is basic physics - it's putting more rubber on the road, which limits the 
wear in any specific spot.  If you doubt this, further argument would be 
pointless.

7. Mike recommends that you look at the tire manufacturers suggested tire 
inflation pressure rather than the number the motorcycle manufacturer puts 
in the owners manual, to get the optimum performance from the tire.
This appears to be a controversial area.  Michelin recommends you to use 
the motorcycle manufacturer's quoted setting. 
http://motous.webmichelin.com/tires/safety.htm#inflate

Dunlop isn't sure what you should do.  First they tell you to follow the 
motorcycle manufacturer's guidelines and then they tell you that for a 
touring motorcycle (George is riding an ST), the rear tire must be kept at 
36 PSI (light loads).  This would tend to support my position for general 
riding, but doesn't address the worn tire issue.

http://www.dunlopmotorcycle.com/infocenter_tiretips.asp?id=31#tip

Now, lets look at your second citation 
(http://motous.webmichelin.com/tires/safety.htm#under).

The section makes no mention of "wear."  This is a safety related section 
that tells you not to run a tire under inflated.  And, they're talking 
about a tire that is so under inflated that it can cause the tire to spin 
on the wheel.  Now honestly, do you think that's what George or I had in mind?

Lastly, and I'll apologize for this up-front - I just have to get this off 
my chest.  Do you realize that in the time you spent mounting your ill 
conceived attack, you could have updated the TSRA webpage so that viewers 
wouldn't think Sprint riders were a bunch of dolts counting down (or is it 
up) the days for the 2002 Rallye?

http://www.tsra.cc/dawgs/index.html

Craig

At 05:13 PM 3/2/2004 -0800, you wrote:

>On Mar 2, 2004, at 3:17 PM, Craig Tate wrote:
>>The question is, "what part of the tire will be worn when the tire is 
>>under inflated?"  Rather than take my advice, or the advice of others 
>>here, look at any tire manufacturer's web site.  You will see that under 
>>inflated tires wear on the shoulders, over inflated tires wear in the center.
>
>That is certainly true for automotive tires, but automotive tires have a 
>completely different tread profile.  It is flat, quite unlike a motorcycle 
>tire profile which is rounded to allow for the lean angle a bike is 
>capable of (and a car, obviously, is not).
>
>(The flat automotive profile is prone to arching upward of the center 
>tread when under-inflated, causing the outside shoulders to have greater 
>contact with the road and wear faster.  Similarly, when over-inflated, the 
>middle of the tread in an automotive tire will wear faster because the 
>center is arched downward, lifting the shoulders of the tread.)
>
>I checked Michelin's and Dunlop's motorcycle web sites, and aside from 
>articles on cupping, could find no articles to support your assertion.
>I'd be happy to read the ones you found if you'd post the URLs.
>
>Here are a couple of articles I found that seem to disagree with your 
>assertion, too:
>
>Here's what an interview 
><http://www.motorcycle-usa.com/Article_Page.aspx?ArticleID=442&Page=1> 
>with a Dunlop person (Mike) had to say:
>
>"But the most important factors affecting tire life is controllable by the 
>rider. The number-one factor that leads to premature tire wear is 
>underinflation. Mike Manning travels to motorcycle events around the 
>country with the Dunlop Tire Inspection Crew. They provide tire care and 
>free tire inspections to all motorcycles. He tells me that 85% of all 
>tires that they check are underinflated. Not only is that dangerous for 
>the bikes handling, but it can shave 20 to 40% off the tires life. Mike 
>recommends that you look at the tire manufacturers suggested tire 
>inflation pressure rather than the number the motorcycle manufacturer puts 
>in the owners manual, to get the optimum performance from the tire. You 
>can safely inflate the tire up to the maximum tire pressure shown on the 
>sidewall of every tire, so it offers more load capacity when you are 
>riding with a passenger and luggage."
>
>This is what Michelin has to say about under-inflation:
>
>         <http://motous.webmichelin.com/tires/safety.htm#under>
>--
>Blake "Dawgbert" Sobiloff <sobiloff@xxxxxxxxxxxxxx>
>President, Triumph Sport Riders Assoc.
>San Jose, CA  (USA)
>
>
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