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Old 12-27-2012, 10:34 PM   #1
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tire wear - shackle issue... flipped???

On the way home from picking up my 2012 21RR not new, but never slept in... at the second gas stop... I noticed tires looked low, even though an employee assured me, they were properly inflated with dry nitrogen the day before. I read the sidewalls say max 50# so I filled them to 48# (now hot) and monitored wear. It was a marathon drive home and when nearly there I noticed all 4 tires mildly wearing on both edges, indicating either low TP or too heavy a load. Since it was bone empty, I filled to 50# cold (overnight stay). Fast forward a few weeks. It looked like the tires continued to get worse, so I filled to 53# cold and maintained this during a 3000 mile trip to Missouri. I've scratched my head as I have noticed the wishbone on the curbside is always angled different than the other side, but didn't notice why. The wear continues to get worse but, the curbside rear tire inside is really almost gone. So, using a straight edge I finally checked alignment of the tires along sidewalls as they relate to each other. I found the tire (curbside rear) had a gap of nearly 1/2" as compared to the front tire. The tire on the other side on same rear axle is not all that bad, but the rear tire is set in maybe a 1/4" but in line with the front. I jacked it up and pulled the tires and made a measurement form the front of the tongue to the front axle grease hubs on each side... it showed the curb side was 3/16" longer than the traffic side. I figured what the heck, I'll adjust it. I unbolted both axles and elongate the holes I reasoned would have to be done to allow the necessary corrective movement, then managed to get the front axles even and both axles parallel then re-torgued the bolt; installed the wheels; put the weight back onto the wheels. The toe out on the curb rear wheel was noticeable better and both front wheels seem to be toed in evenly. I drove out and stopped slowly and checked again... it was a little bit better yet. By the way, all 4 wheels show what I would estimate to be 1% to 2% of positive camber. I started looking for a local axle shop online when thoughts of the tilted wishbone came back into my head. I went back out to take some measurements... of spring length, etc. and it finally dawned on me that the reason for the tilt is that the shackle was flipped down on the front side of the wishbone. I don't know why I haven't noticed this before... this was the shackle on the rear of the front spring... while the shackle on the front of the rear spring was angled up... or correct... matching both shackles on the other side. The measurement of eye center on the rear spring showed 26" as compared to 25 5/8" for the front spring on that problematic curb side. That seemed like too much difference. I jacked it up, pulled the front wheel, and placing a jack under the flipped down shackle, I managed to flip it back up, with little effort. The toe on the rear wheel looked straighter, so I got the straight edge out again. It is considerably better now... in fact, it might have negative toe-in. Camber still looking good all the way around.

I think this shackle has been this way since I picked it up, but wonder if it happened while I was pulling it. I also wonder if it will happen again. I wonder if the shackles this way loaded the rear axle heavier??? And, it still may need an axle doctor to really get it right. I have nearly worn out (only on the edges) tires with less than 6000 miles and will have to soon replace the tires. I've been searching on the web for tires, would like D rated 14" tires, maybe Kumho, but it sounds like all brands are pretty much junk with one being about as good as the other. I might just go with a C rated, better grade Carlisle (spelling?) from Discount Tires. I can't believe how pricey the tires are getting... sign of my age, I suppose.
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