FG cupping

GR8ADV

Explorer
Having discussions with the previous owner of our new to us fuso he chased the cupping tire issue in the front. Rotation to smooth them out seems to be about the only answer. In talking with a truck alignment expert locally he said that one could expect cupping running the open shoulder traction tires on the front of a 4x4 fuso with highway driving.

Just curious how folks with the SRW conversions are finding this issue. Are the 315's on the 16's cupping as well? How about the 19.5 folks? What are you seeing?

Thanks.
 

pugslyyy

Expedition Vehicle Engineer Guy
I had that issue. My 19.5 tires didn't come with a good balance. I took them to a place that specialized in truck tires and got them rebalanced, and also added 10 ounces of Counteract balance beads to each tire. Everything runs super smooth now.
 

GR8ADV

Explorer
I had that issue. My 19.5 tires didn't come with a good balance. I took them to a place that specialized in truck tires and got them rebalanced, and also added 10 ounces of Counteract balance beads to each tire. Everything runs super smooth now.
Atw? Came not balanced new? Great they run smooth now. Are you getting any cupping with these. Miles and rotation? Thx.
 

pugslyyy

Expedition Vehicle Engineer Guy
Atw? Came not balanced new? Great they run smooth now. Are you getting any cupping with these. Miles and rotation? Thx.
I've got maybe 15,000 miles on them - 7000 since properly balancing them. I rotate / do oil changes / etc between trips.

They were cupping until I got them balanced right. I balanced/rotated so that the tread was reversed and had no more issues. Don't flip sides when you rotate - left front goes to left rear, right front goes to right rear.
 

gait

Explorer
19.5in Toyos. I have after market camber kits fitted. No cupping. No balancing. I have feathering aound the tyres (not across) and some out of balance since fitting parabolics.

I have some new unused camber kits for 2004 FG649 if anyone wants to buy - one king pin bearing failed and supply mix up halfway round the world left me with too many.

The kits are two eccentric bearing holders (top and bottom) with bearings.
 

pugslyyy

Expedition Vehicle Engineer Guy
Atw? Came not balanced new? Great they run smooth now. Are you getting any cupping with these. Miles and rotation? Thx.
... an update. I just replaced my M608Zs at about 30,000 miles. The issues driving the replacement was cupping (from the front axle) and scalping (from traction mats on the rear axle).

I had to harangue Les Schwab to do a better balance on the front axle. When I get back to North Carolina I'm going to have all 4 wheels rebalanced by a place that I know and trust to balance truck tires correctly.
 

Butch1979

Family Adventurer
Interesting to see this come up... my Toyo front tire was cupping bad on the passenger side, so I took it into the dealer for a look.

They said my passenger front shock was toast and caused the cupping. They swapped the tires, realigned and order a new shock (haven't installed it yet).

Shock: I was about to start a new thread on this. Seems strange that I would have a bad shock with less than 10K miles on the truck.... Do I need beefier shocks? Suggestions?

Cheers

Butch
 

pugslyyy

Expedition Vehicle Engineer Guy
What I called cupping can be more accurately described as heel-toe wear.

(not my tire, but an example of what I was seeing)

 

yabanja

Explorer
I believe the cupping is a direct result of binding of the rear limited slip differential causing friction on the front tires around corners. Ford makes a product called friction modifier specifically for clutch style limited slips which will eliminate this binding when added to the rear differential fluid.

Allan
 

gait

Explorer
What I called cupping can be more accurately described as heel-toe wear.

(not my tire, but an example of what I was seeing)

that looks like what I called feathering. I observed it after changing to parabolics which also coincided with replacing a king-pin bearing and alignment check - doesn't mean its the only cause though.

I believe the cupping is a direct result of binding of the rear limited slip differential causing friction on the front tires around corners. Ford makes a product called friction modifier specifically for clutch style limited slips which will eliminate this binding when added to the rear differential fluid.

Allan
thanks, that hadn't occurred to me. Sorry to be pedantic, is that cupping as in Puglsys image?
 

Aussie Iron

Explorer
I myself doubt you will see that type of wear on the rear, it is normal wear on front tyres that have block tread. Caused by the way the wheel leans going around corners (from caster and camber) and can really be noticed if you travel a lot of roundabouts on the inner side wheel/outer edge. Also from fast cornering - Open freeway and fairly tight corner for the Canter may not be tight for a normal car.

My Idea,
Dan.
 

pugslyyy

Expedition Vehicle Engineer Guy
Could this be related to not having a rear axle in alignment? Just a thought.
Could be but I don't think so. More likely that it was caused by all the flex I was getting in the old frame as it was slowly breaking in half.
 

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