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Topic: Causes for Cupping on RF inside shoulder  (Read 496 times) previous topic - next topic

Causes for Cupping on RF inside shoulder

Took our coach to the shop to have our tires inspected before heading out this summer. All looked good except right front which had some minor cupping on the inside shoulder. I had them switch the outside rear with the right front as a precaution. Without any symptoms of that alignment, or out of balance, what are the potential things I should be looking for as the cause of this where pattern.
Randy (N4TDT) and Karen Crete
Sarasota, Florida
SOLD:  2000 U270 34' WTFE Build 5756 "Ole Red"

Re: Causes for Cupping on RF inside shoulder

Reply #1 –
Doesnt that change the tires rotation?  I avoid that  for the big tires.

Re: Causes for Cupping on RF inside shoulder

Reply #2 –
The switch was passenger front to passenger rear outside.  Same rotation.
Randy (N4TDT) and Karen Crete
Sarasota, Florida
SOLD:  2000 U270 34' WTFE Build 5756 "Ole Red"

Re: Causes for Cupping on RF inside shoulder

Reply #3 –
Andy,

There can be several causes of cupping.  The cause is the tire bouncing because of:

Out of balance tire

Worn suspention componants

Tire out of alignment.

Run over a smooth road at different speeds and see if you can detect even the slightest vibration in the steering wheel.  Go up to at least 65 mph.

If you can't do it yourself have that wheel lifted so the suspension is not bearing any weight then check for worn or loose components.

If all is OK have the alignment checked at a place that does big truck alignments.  A good machine will be a computer aligner that will not only check front end but rear as well as front to rear alignment.

Keith
Keith, Joyce & Smokey the Australian Cattle Dog
1995 U320 SE Extreme 40' WTBI Build # 4780, with a Honda CR-V hopefully still following behind.
Motorcade # 17030
FMCA # F422159

Re: Causes for Cupping on RF inside shoulder

Reply #4 –
Can the rear be adjusted if its out? I was told by the alignment place they could not but I have never looked to see if it was able to be done but they do not want to do it.

Re: Causes for Cupping on RF inside shoulder

Reply #5 –
If the coach is not crab crawling there is nothing an alignment shop can do. If it is crab crawling something is worn out or broke.
1999 40 ft. U-320 wtfe build 5563 Chuck & Lynda's "Rollin' Inn"  2030 watts solar
prev. mh's 71 GMC 5 yrs. 73 Pace Setter 1 yr. 78 Vogue 5 yrs 81 FTX 40ft all electric 18 yrs. 1996 Monaco Signature 3 yrs.
2014 Grand Cherokee Overland
Dream as if you will live forever. Live as if you will die today.  James Dean

Re: Causes for Cupping on RF inside shoulder

Reply #6 –
Quote from: craneman –
If it is crab crawling something is worn out or broke.

My top 3 reasons Trailing arm bushings slop, Panhard bar bushings slop, or bulkhead joint failure.

Mike
Pamela & Mike 97 U 320

"It's not what happens to you, but how you react to it that matters."

Re: Causes for Cupping on RF inside shoulder

Reply #7 –
Could the cupping possibly have been the tire rubbing on the bottom of the rearmost air bag?Remind us,have you installed new shocks recently?I would consider having the balance beads installed or getting the concentric system.
96 U270 BUILD 4810
85 380SL
Drummonds TN.

Re: Causes for Cupping on RF inside shoulder

Reply #10 –
Quote from: John44 –
Could the cupping possibly have been the tire rubbing on the bottom of the rearmost air bag?Remind us,have you installed new shocks recently?I would consider having the balance beads installed or getting the concentric system.

John - new Koni's in the last 3 years.  Since they're 295's from previous owner that may be a factor.  Gonna have a closer look at the airbag mount tomorrow.
Randy (N4TDT) and Karen Crete
Sarasota, Florida
SOLD:  2000 U270 34' WTFE Build 5756 "Ole Red"

Re: Causes for Cupping on RF inside shoulder

Reply #11 –
I asked because we just saw one of Bob's (journey roam and explore)tires with a gouge that could have been mistaken for a
cupped tire.
96 U270 BUILD 4810
85 380SL
Drummonds TN.

Re: Causes for Cupping on RF inside shoulder

Reply #12 –
Could be a loose or failing RF wheel bearing. If you take it in for an alignment it might be a good idea to have both front wheel bearings checked for clearance/failure before doing the alignment.
Greg & Cathy
2000 U320 4010 DGFE Build #5650
Had: 1999 Tradewinds 7370

Re: Causes for Cupping on RF inside shoulder

Reply #13 –
They track poorly  with loose bearings. Wander etc. Zero plus a pinch .