I noticed when driving my F4 this weekend that the wheels didn't turn very sharp. The turning radius is a lot larger than I think it should be for a truck with a 134" wheelbase. I checked the stop bolts and they were adjusted out 1 1/2" and 1 5/8". I removed them and the wheels will turn quite a bit farther each way. I put in shorter bolts and adjusted them both to 1" long. There is still plenty of clearance lock to lock on both tires front and rear. I don't have the fenders on yet, but I can't imagine they would be an issue. Am I missing something, do the stop bolts need to be adjusted out as far as they were?
Thanks, Mark

 

Perhaps I'll get a chance to play with that area on my F4 tomorrow or soon. No, it does not turn sharply. As long as the tie rod does not go into an unrecoverable, over center angle I see no problem. My guess is the stop is put there to eliminate an oversize tire from contacting the frame. Perhaps brake hose angle is a concern, also. Full spring compression against a fender check will be required.
This brings to mind that old country song, Give Me Forty Acres and I'll Turn This Rig Around.

 

Can the worm/sector in the box go too far?

 

Thanks, Ray It would be interesting to see how the stop bolts are adjusted on your axle. I don't think the spindles would ever be able to turn far enough to take the tie rod over center and lock the steering. I will look at it again tomorrow.
Mark

 

Ross, Even with the stop bolts removed, the steering gear would go farther than the spindles would allow. When the spindles were turned as far as they would go either direction, you could see the drag link bending the steering arm trying to move it further. The tires never touched anything on the frame even without the stop bolts.
Mark

 

All you are doing is checking the static adjustments, and not factoring in for inertial vector forces that take place during a turn in motion. These will want to change the static geometry. Also, a higher rate of advance will create higher forces that will have to be compensated for. An analogy would be like hitting a speed bump at an angle.

 

True, but you will only be turning against the stops at a very slow speed. I don't believe the geometry has changed sufficiently to cause the steering to be harder to turn back to straight.
Mark

 

I'm trying to recall this stuff from memory from my truck R&D days at PACCAR in the '70's. When I get back to my truck I'll check the length of the stops.

 

I measured the stop length on my F4 at 1 1/2", both sides. I have drivein this truck for two years and several thousand miles but can find no witness marks on the axle to indicate I've turned it sharp enough to make contact. I see no problems with making the stops a bit shorter. I have installed upper shock brackets that would be the closest point of contact if the stops were not present but even that is a long way from contact. BTW, my tires are about 32" diameter, G225x19.5s.
Edit: Perhaps the function of the stop is to keep the angle of the tie rod to the steering arm where there is still a MA that can turn the steering wheel with the wheel in a tight, in a rut or against a curb condition. The greater the angle between the tie rod and steering arm, the more effort required to turn the steering wheel. Did I explain that?

 

Thank you Ray for checking your truck. I have 8R 19.5 tires on the front now, IIRC they are 34", and I don't have any clearance issues even with the stops removed. I will have two new 225R 19.5s installed on the front when I am ready to start driving. The ones on the truck have probably 90% tread, but they are old. I think I will set the stops at 1" and carefully drive it and see if there any problems.
Thanks again, Mark

 

Bob, Thank you for your replies. I hope I didn't sound argumentative in my replies to you. I mentioned to Ray in my reply to him that I was thinking of setting the stops at 1" and carefully driving it to see if I have any issues. It doesn't appear that there will be any clearance problems, so in your opinion, what do I need to look out for as I test it? I will be able to test it on pavement, no curbs or speed bumps though.
Thanks for your help, Mark