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Old 09-01-2013, 03:01 PM   #1
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Strange tire wear pattern

I noticed a strange wear pattern on the front tires of my 2008 Berkshire 390BH. There seems to be a small, concave 'groove' that is wearing on the inside and outside edges. I thought that it might be under-inflation, but according to the charts, I am right at the recommended pressures for the weight on the tires (LF tire is at 97 lbs, weight is 4830, RF tire is at 96 lbs, weight is 4510). Not sure why the tire is wearing this way. Any ideas?
Thanks,
Tom

I have attached pictures that I hope will show what I am trying to describe. Tires are Michelins 255-80x22.5.
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Old 09-01-2013, 03:47 PM   #2
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Wear on both edges of tires is an indication of under inflation regardless of what charts say about tire pressure vs load.
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Old 09-01-2013, 03:50 PM   #3
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If you don't use the weight/pressure charts, how do you determine the pressures for the tires?
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Old 09-01-2013, 04:10 PM   #4
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If you don't use the weight/pressure charts, how do you determine the pressures for the tires?
It is a good starting point, but as you are experiencing, you are wearing the outside and inside edges of both tires indicating under inflation. If it were me, I would increase both front tires by at least 15# or to be safe and to even out the wear, inflate to whatever the max sidewall pressure says.
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Old 09-01-2013, 05:01 PM   #5
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Here is a pic of over and under inflated tires OC is dead on!!

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Old 09-01-2013, 05:29 PM   #6
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it may be that the pressure gauge you are using i out of calibration or the weight is greater than thought
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Old 09-01-2013, 05:41 PM   #7
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Here is a pic of over and under inflated tires OC is dead on!!

Attachment 39009
awwall,
I see where the tread wear pattern for under inflation involves the outside edge of the tire. However, the tread wear on my tires shows just a small, concave area along the edge. Not the entire outside edge as shown for under inflation.
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Old 09-01-2013, 06:06 PM   #8
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There are numerous posts on tire inflation in these threads.
Here is one such post.

Many who are posting are providing answers based on their personal experience or what they have heard round the campfire.

As a Tire Engineer i would like to provide a slightly different perspective. One based on 40 years experience working for a major mfg. as many posts by non-engineers are not completely correct.

Your motorhome should have certification label (tire placard) that the RV manufacturer applied to the vehicle. This

Here is a post on my blog on load & inflation

Also on gauge accuracy

The basic answer is that for motorhomes you need at least enough inflation pressure to carry the actual load on the tires.
Trailers should use the inflation on the tire because of unique side loading of tandem axles.

Until you get the real loading on each corner of your RV I strongly suggest you set your cold inflation to the inflation on the placard or 5 to 10 psi higher but not exceeding the inflation molded onto the tire.



tmmar
Do you have any idea what your actual tire loading is? You provided the tire size but not the Load Range. Also what are the axle ratings on your placard. GAWR Front & GAWR Rear and what inflation F & R are shown on your placard? Having this information makes providing accurate answers easier.
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Old 09-01-2013, 06:08 PM   #9
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awwall,
I see where the tread wear pattern for under inflation involves the outside edge of the tire. However, the tread wear on my tires shows just a small, concave area along the edge. Not the entire outside edge as shown for under inflation.

You take good in-focus pictures. Can you get one looking over the tread (similar to that seen in the drawings) not from the side?

There are a couple different types of circumferential wear with different causes. I really don't like guessing.
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Old 09-01-2013, 06:22 PM   #10
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Tireman9,
Dark and cloudy now but hopefully it will be nicer tomorrow (although the forecast is for cloudy and rain). The loading on the left front is 4830 lbs and the right front is 4510.
Tom
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Old 09-01-2013, 06:32 PM   #11
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Tireman9,
Dark and cloudy now but hopefully it will be nicer tomorrow (although the forecast is for cloudy and rain). The loading on the left front is 4830 lbs and the right front is 4510.
Tom
Also, Tireman...... I've been told that all tires on the same axle have the same pressure, regardless of the individual wheel weights. True or False?? Enquiring minds want to know.

Boowho??

P.S. "You da man" when it comes to tires. Your credentials are impressive. I also notice you are from Akron.
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Old 09-02-2013, 09:40 AM   #12
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Also, Tireman...... I've been told that all tires on the same axle have the same pressure, regardless of the individual wheel weights. True or False?? Enquiring minds want to know.

Boowho??

P.S. "You da man" when it comes to tires. Your credentials are impressive. I also notice you are from Akron.
I was also under the same impression that Boo stated that tires on the same axle have the same pressure. If you could verify if this is true or if it is not it would be appreciated.

I also agree with Boo's statement about you being the tire expert here.
Thanks for your input.
Tom
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Old 09-02-2013, 11:58 AM   #13
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tmmar & boowho
Yes all tires on any axle should have the same inflation.
For motorhomes like immar's that would mean his minimum inflation should be capable of handling 4830.

For motorhomes, Look up your size in the tire mfg's load/infl table and find the inflation that is rated for 4830 or more. That would eb your MINIMUM cold inflation. I suggest you add about 10% to that so you don't have to mess with adjusting inflation when the ambient temp changes.
Don't exceed the rating for the wheels.

For multi axle TT I suggest you run the inflation molded on the tire. This will help decrease the internal structural loads that are trying to tear the tire apart.

Different loading dynamics need different solutions. Most of the published information is based on old single axle TT.

TT owners might want to read THIS post.


General info on Inflation HERE and HERE.
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