1979 K20 pitman arm rubbing my 315/75/r16 - is this normal?

[LuckyLightning]

I'm usually a 1960-1966 truck guy, so this is my first square body. Also my first 4x4 with straight axle.

I have some Nitto Grappler 315/75/r16 tires with stock 2000-2003 HD aluminum wheels on my truck and every time I crank my steering wheel all the way to the right, my front driver tire rubs the pitman arm pretty good. It leaves a mark on my tire and is tearing up my output shaft seal on the steering box. So naturally, I try not to do this right now.

I bought the truck a few months ago the way you see it now. I don't think there's a lift installed, but who knows (there's no block at least).

My question is: is this normal? I see other drivers with this size tires (usually with a 2.5"-4" lift too) and no one has any issues with their pitman arm. I doubt it's a back spacing issue, since no one else with these wheels seems to complain about this issue, but again you never know.

Is it possible to remove the pitman arm and re-install it "re-keyed" so it's turned away a little from the tire so it doesn't touch anymore?

I have 4.56 gears so I really don't want to go to a smaller tire. Would love to know if there's something about the pitman arm that can be changed to fix this... or maybe I just need to go back to the old steelies...

[b454rat]

Those wheels have a lot of back space. Put a small spacer on it will be fine, 1" or so.

[Mike C]

And they are narrow as well. My 33 14.5 Mickey Thompsons on an 8" wheel rubbed on mine, but when I went to 10" rim with same backspacing that went away.

A 315 is really too wide for that 6.5" rim so the best thing to do would be get some wider rims, probably not what you want to hear...

[kwmech]

Wrong rims with the wrong tires on the wrong truck sums it up

[special-K]

I was confused till I saw the last picture, then...BINGO! New style wheels have too much backspace. As mentioned, you want at least an 8" wheel with those tires

[LuckyLightning]

Thanks everyone. I guess that makes sense. So I guess the stock steelies would be too thin as well? I think they are also 6.5" wide.

[special-K]

You want 8"-10" rims with those tires

[snj8198]

What trans are you running LL? if you had OD you could drop your tire size down to 33's like we chatted about and not raise the R's. The 255/85 runs a true 33" where 315's usually run 34". Granted, you'll lose a lot of width if that was what you're wanting. Again, my 315's measured 12.9" wide on 8" wheels vs 10" with the 255's.

[LuckyLightning]

Hey there snj8198. I think it's a sm465 because it has a 3 speeds (L, 1-3, R). I think I can get an OD for it, but haven't really looked into it much. It's a really nice "nice-to-have" though, so it's low on my list of priority upgrades/fixes.

I think 255/86 might be the way to go for me. I've always liked the 235/85 tires but think they are too small for my gearing. The 255/85 tires should fit my 16x6.5 steelies, right?

Otherwise I'm eye-balling military 37's but I'm pretty sure I would need a lift to get those on.

[Mike C]

The 36" bias military tires will fit with a 4" lift. But they suck on the street. I just got rid of mine. They were exactly the same size as the 35" BFG MT's that used to be on the truck but the 8 lug swap needed larger diameter rims and the combo I found at the time fit the budget. The 37's will need 6" lift and maybe some trimming as they are a LOT bigger.

What gear is in the truck? 4.10 or 3.73? (or 4.56 for that matter if a CUCV donor).

3.73 would be fine with 33" tire and no OD and a 4.10 gear works for 35's just fine once again without od. If you have 4.56 the 37's would be OK, but 4.56 and 33's would be a lot for running around on the street. (Although that is the exact combination I am putting together for my '79 CJ5.

And maybe will see you around? Just noticed we are darn near neighbors.

[enaberif]

You need rims with a minimum backspace of 4"

For those tires you may even need 4.5" of backspace to clear everything properly.

[snj8198]

Originally Posted by LuckyLightning

Hey there snj8198. I think it's a sm465 because it has a 3 speeds (L, 1-3, R). I think I can get an OD for it, but haven't really looked into it much. It's a really nice "nice-to-have" though, so it's low on my list of priority upgrades/fixes.

I think 255/86 might be the way to go for me. I've always liked the 235/85 tires but think they are too small for my gearing. The 255/85 tires should fit my 16x6.5 steelies, right?

Otherwise I'm eye-balling military 37's but I'm pretty sure I would need a lift to get those on.

ya, that would be the 465.

I've never had a problem running the 255's on the 6.5 or 7" wide wheels, in fact I prefer that pizza cutter performance of that combo. You are still going to need to address your wheel situation since your current backspacing is still not going to work for you even with the 255's.

33's with 456 gears are steep. I've ran that before and did not like it without an OD. Unless you're towing, town driving, and not hitting the hiway often i'd be looking into an overdrive trans in the future.

hope im helping.

Steve

[special-K]

The 'widest' wheel you want with a 255/85 is 8". Stock wheels are fine. find yourself some Accurides (7" Ford). They are the newest and widest 16" factory steelie you'll find

[LuckyLightning]

Thanks everyone, I really appreciate everyone's help with this.

Originally Posted by Mike C

The 36" bias military tires will fit with a 4" lift. But they suck on the street. I just got rid of mine. They were exactly the same size as the 35" BFG MT's that used to be on the truck but the 8 lug swap needed larger diameter rims and the combo I found at the time fit the budget. The 37's will need 6" lift and maybe some trimming as they are a LOT bigger.

What gear is in the truck? 4.10 or 3.73? (or 4.56 for that matter if a CUCV donor).

Oops, I thought I included that in the OP. I do have 4.56 gears. And I don't really want to add such a high lift (maybe 2.5" spring lifts... someday), so maybe I'll stay away from the military tires.

Originally Posted by snj8198

I've never had a problem running the 255's on the 6.5 or 7" wide wheels, in fact I prefer that pizza cutter performance of that combo. You are still going to need to address your wheel situation since your current backspacing is still not going to work for you even with the 255's.

33's with 456 gears are steep. I've ran that before and did not like it without an OD. Unless you're towing, town driving, and not hitting the hiway often i'd be looking into an overdrive trans in the future.

Well, I have the 6.5" original-style steelies. It looks like I can safely use those with the 255/85 tires. I'm looking for some all-around performance (towing, in-town driving, hiway driving), so it's a shame BFG doesn't make their All-Terrain's in that size, those are my favorite tires. But I can look at the Toyo MT's that you're running.

[LuckyLightning]

Oh, and Mike C, I'm in north Round Rock but I get into Austin every now and then. Definitely honk if you see me on the road.

[LuckyLightning]

Thanks again everyone for your help. Finding used 255/85/16 tires on craigslist is difficult. I may have to bite the bullet and buy them new. In checking prices and reviews, it looks like I might be going with Maxxis MT-762 Big Horn tires.

Pros:
- a LOT of positive reviews on the internets (grip, sidewall strength, ride quality, road noise, 40k-50k miles tread wear)
- price is better for my budget
- has the look I like

Cons:
- I do mostly road/highway driving
- hardly do any 4x4 wheeling
- want to be able to tow a vehicle on a flatbed
- 40k-50k miles tread wear (it's both a pro and a con)

For what I'm looking for, I realize all terrains are a better choice (BFG's are my absolute favorite [I got about 70k-ish on my first set], but not available in 255/85/16). However selection and price are my hurdles. I wonder, anyone think it's just a terrible idea? Otherwise, I think I'm going to do it.

[LuckyLightning]

Oh, I forgot: if I go with the Maxxis tires, should I stay with the aluminum wheels or switch to steelies? Would the weight difference really affect my fuel economy so negatively?

[snj8198]

The Maxxis Bighorns are just an all right, middle of the road traction tire. Some of my logging co workers have run those as a cheaper alternative to the Toyo's but they dont get the longevity out of them. Their work rigs are usually heavy and weighed down with transfer tanks, tools, parts, etc. I wouldn't chose this tire if you are primarily road and hyway driving. There has to be an AT tire in your size that would be much better suited for your needs especially if you want the longevity.

Steel vs aluminum: i'm not sure if i have an opinion on this. i dont think i've ever been able to tell the difference fuel wise between them.

good luck LL

[b454rat]

I don't think you will notice the difference in weight between the two. Now if you have an import with 50lb of torque then I would think you could tell. IMO, I would go with 35s (315 like you have now) to go with those gears. I had a truck with 4.10s, 35s and 4-speed as was bout perfect. Low would still get you going, and on highway the tach was bottoming out. Course depends on what motor you have too. SB might need the gearing, whereas a big block doesn't. 4" will clear 35s with the right b/s, 37s with some trimming. The tall skinny will be best for performance, less rolling resistance, but the fat tire look is always nice too. Check on c-list, I see tires and wheels for sale all the time.

[special-K]

I don't know why you aren't looking at the Cooper Discoverer S/Ts. They are an All Terrain, yet a far better M&S tire than a BFG A/T. They wear long, haul a load well, are about the best priced, and are nearly 34" tall. I am totally happy with mine. They ride smooth, too. I haven't even balanced mine.

In a 10" wheel, steel vs alloy is about 10#. If your truck's suspension and drivetrain feels that in any noticeable way you don't have much of a truck. Steel wheels have used on everything that rolls and they do it just fine. I had the factory steel wheels on my '92 K3500 for 335,000 miles with 285/75s or 255/85s the whole time, hauling weight the whole time, and it was just needing it's first ball-joint replacement on an all original front end. You have heavy old steel wheel, heavier bigger tires, diesel engine weight, payload weight, and a wimpy no good front end, yet never a front end wear issue.

[LuckyLightning]

Thanks everyone. Part of my issue (which is all me) is that I like the knobby look. I know mud tires are excessive, wear faster, get poorer fuel economy, and are louder. So when looking at AT tires, BFG and General offer the knobby look I like without the hit in performance MTs get.

snj18198, your input is invaluable. Real world heavy lifting experience. I'll keep an eye out for AT tires in the 255/85/16 size, but Pep Boys is having their special of buy 3 tires get the 4th free and they only have Maxxis in my size. It ends this Sunday, so I don't have a whole lot of time if I want to take advantage of their special.

b454rat, I have 315/75/16 on now and they are causing my rubbing issue currently. Also, it seems to be the common consensus they are too big for my 6.5" wheels (aluminum and steel). I don't have the budget for new wheels plus these are my favorite kind of wheels. Lastly, I prefer the pizza cutter look.

Special-K, I've had Cooper Discoverer tires before. They were 285/75/16 on 10" (or 8", not too sure now) aluminum moto wheels wheels on my '62 3/4 ton I used to have before my square. I hated it. I could feel every bump and I didn't care for the look very much either.

On that '62 I switched over to BFG AT (okay this is my 3rd set) 235/85/16 on the original steelies and loved it. That truck also had 4.56 gears but I didn't have the truck long enough to really get it on the highway more more than a few times, but I rarely took it over 55-60mph.

I have Nitto Grapplers now on this square and they are okay, but when the roads are wet I have almost zero traction. Adding to the sense of urgency, I want to remove them and sell them before the tread gets any lower (reducing my asking price).

[snj8198]

sounds like you've got it worked out LL. Sell the items you dont need to free up some quick cash and take advantage of the Pep Boys sale.

I can't remember where we left off on wheel backspacing... you sure you wont have rub issues with the new Maxxis and your 6.5 wheel backspacing?

[LuckyLightning]

Hey there snj1898, actually not yet. I called Pep Boys and they said the discount does not apply to the Maxxis tires. I'll just have to keep looking.

And yeah, I forgot the aluminum back spacing is also an issue! I think the steelies are supposed to have .5" less/more (whatever it would be) that will prevent the issue with my pitman arm that my aluminum wheels are causing.

So with the steelies, and skinnier tires, I should be able to get this solved. I'll do more research on the backspacing issue, to be more certain before I move forward (but the skinnier tires are going to happen no matter what).

Thanks again for all your help sir.

[b454rat]

Dunno how much your looking to spend, but swamper makes a 34" tall tire that is skinny and 16" rim. Plus being it is a swamper it will closer to size than most other brands. Plus it's a mud tire, so you will have the look

Go to Summitracing.com, you can look at every tire size they have for a 16" rim. Also if you like rims you have now, you can order spacers there as well.

[LuckyLightning]

I'm wondering if any of you guys have any experience with this kind of tire, both in durability and traction?