Caster adjustments to suit 11.00X20 changeover

[dikwks]

I recently put 11.00X20 radials on the deuce. It rides smoother for sure, but has the same symptoms that others have noted: a poor return to center and a squirrely feel to the steering. The steering system is tight so it's not a parts issue. I'm pretty sure it is a caster problem. As in there ain't enough.

I've been looking through the threads about caster changes, but can't find specific info with regard to how much change is needed. The amount of change on the spring perch modification by gringeltaube calls out a 2.5º, someone else got a 3.5º shim, and someone else had posted a picture of a 4º shim. I would prefer not to alter the spring perch as it would be a permanent modification. Adding a wedge would be my first choice.

So, my questions are: 1. How much change have others made? 2. What shims did you use? 3. Where did you get them? 4.The picture I found shows a shim that is 2.5 inches wide and 5" long, but the contact patch of the perch to the spring is 2.5" by 6.5" long. Is 5" long enough? And last, 5. Was your locator pin in the spring pack still long enough?

Looking forward to hearing from everyone, Dick.

 

[OD_Coyote]

I ran Firestone T831 11.00R20 on my 1985 M35A2C and never had any issues with return to center or handling with no changes to the caster....If anything is handled better with the 11.00s vs the 9.00 NDT bias tires.

 

[Hainebd]

Check your toe in first. Need 3/16" or better narrower in front compared to back side of front tire.

 

[Hainebd]

I am running 395 and have no issue either.

 

[dikwks]

Anybody got something to share on shims? Pretty sure that is the problem but would like some input about what shims were used. Toe is already set slightly positive.

 

[Flyingvan911]

The Firestone 11.00x20's don't seem to cause trouble. It's the G177's that need caster adjustment. Look up a thread my Aswayze. He showed how he made his faster adjustment.

 

[wheelspinner]

I am getting ready to put the G177s on as well. Look forward to this information.

 

[peashooter]

Check out this thread it has some good info: http://www.steelsoldiers.com/showth...-G-177-tires&p=1497451&viewfull=1#post1497451

 

[sandcobra164]

Peashooter, Thanks for your link to this thread. The different perches would explain why Firestone T831's made my truck a handful to drive while others seem to have no issues. On my truck, it would follow every pebble in the road and had very poor return to center. I ground my spring perches according to the advice that Gringletaube had provided and I reference that since the OP has apparently read that thread as well. My truck drives just fine now and I'm able to enjoy my drives in it once again. For what it's worth, mine is a 1971 AM General but of course any of these trucks can be a combination of old and new parts. I have a friend who has a 1974 M109A3 that no longer has the box and now has a bed. We put Goodyear G177's on his truck and it drives just fine with no modification of the spring perches. To dikwiks, I'd say that we must have similar spring perches and since you do not desire to grind them down slightly, research the options Peashooter has provided. I'm now curious to compare the part number on mine to the image Peashooter provided. I'll post which one's they are once I get some time to crawl under there and look.

 

[Clay James]

My 109 would wander really bad when I first put on the T831s so I shimmed it and that took care of it. Now I put those T831s on my M35A2C and it wanders some over 55 but it's manageable. Not as bad as the 109 was. Going to shim it some. Like others mentioned, it just depends on the truck.

 

[welldigger]

I think the need to shim has to do with which front spring pack you have and how worn out (flattened out) they are. Just a theory I have.

 

[dikwks]

Update to the thread: I got some two degree shims ( from Summit Racing, I think). After measuring the thickness of the shim at the hole, I decided not to use them as I would have lost too much of the pin engagement of the spring to the upper side of the perch. The shim was .250" thick at the hole and the pin wasn't but about 1/2" long. I used gringeltaub's grind the spring perch method to get the angle change needed. I thought about having them machined, but ended up using a grinder, straight edge, and file to get the extra 5/32" out of the perch. Worked out pretty good. Got them reinstalled today and drove it around some. Return to center is much better and it doesn't feel as squirrely going down the road. I haven't decided for sure that I'm completely satisfied, it does feel different from the bias-ply tires, but how it feels may be skewed a bit by the fact that I have only been driving the M925A2 for the last few weeks. Now that it's done, I'll be able to safely drive it around some to get a better feel for the truck. As a side note, the front tires are inflated to 60 #. That leaves a little bit of a bulge in the sidewall. I may play with that some in the next few days. Hope this helps. Dick