I've had this setup since last April and have had a problem but could never figure it out. I put an 8" lift on my '99 Super Duty and put a set of 38x14.5 Thornbirds on 16x10 rims. The problem is that whenever I turn the wheel so far either direction the tires hit the leaf springs. Its a real pain because its the side lugs that catch and its pretty rough. I thought maybe the side lugs weren't part of the measurement but i went from side lug to side lug and it was around 14.75". This still shouldn't be a problem according to the charts I've seen saying that with an 8" lift I should get 38x15 on 16x10 rims.

One more thing I can't really figure out. If you'd look at my gallery and tell me if you think my front axle seems to be sitting off center, as if it is forward where it should it?

 

Change the springs to dual shocks on the front or get smaller tires, theres really not a way to stop then from hitting the leaf springs, the tires are too wide

 

if u go with a 12" wide wheel it won't hit the springs

 

I have the same problem with my 8inch lift and 37inch tires, except only on left hand turns. My old solid axle toyota had adjustable stops on it where you could limit how far the knuckles turned by adjusting a bolt with a nut on it. The dana front axle does not have this adjustment on it, so I was thinking about drilling and tapping the stop that is on it so I could adjust it. You basically are reducing the amount the knuckles can pivot, increasing your turning radius, but stopping the annoying (and embarrasing) rubbing noise.

 

Yea you can take that route if you want

 

After looking at your pics, I now know what you are talking about your axle being off center. I thought you were talking side to side at first. Most lift kits move the whole axle forward an inch or two by putting the locating pin further forward than stock. This moves the tire forward and away from the fender/firewall area so that bigger tires won't rub. It does move it closer to the front bumper/dam, but that is easier to fix than the fender/firewall. Either trim the dam or space the bumper out.
After putting my superlift springs on my tires were hitting the dam on turns so I spaced the front bumper out with about half an inch worth of washers. That was enough to do the trick but I might go to one inch just for looks(so the tire appears centerd)

 

As was metioned you can drill and tap your steering stops and prevent the tires from rubbing.
12" wide wheels would solve the rubbing on the springs but create clearance issues with the fenders and front bumper........and will place more stress on the front end components.

 

Alright, so now that I know that the axle being forward is normal I am going to go ahead and space the bumper for the look. But back to the tires rubbing, I got a set of 35x12 tires for the winter because those Thornbirds are like driving on oil in the rain, I didn't want to chance them in the winter. The 35x12s do run fine without rubbing, I just wanted to find out about the wider tires. If you guys are saying they're too wide, then why does the chart on the natltire say that with an 8" lift that 38x15s work? I'll be getting a new set here soon and I just wanted to figure this out because I was looking at some 38" ground hawgs.
Thanks for all the quick replies.

 

You might want to just limit your turning radius. If you go to a wider rim or space out the wheel you will increase your pinion inclination or scrub radius. That will add a ton of load on your steering and your truck will go through parts really fast. Most 8" spring kits out there move the spring pin forward to get better wheel recesion so you will have about 1"-2" more wheel base. so its normal to see the front end forward in the wheel well. SOmetime you need to give something up like turning radius to keep everything happy. The WORST thing you could do for the truck is to widen the wheel or space it out.

 

Got the same problem with my 34" tires, grubbin springs. soooo unless you got back full stock, don't think a smaller tire gonna do it

Oh well, who needs less than a football field to turn anyway.

 

yEAH, OR TRY 14" wide rims....

 

...or ditch the Thornbirds!!



Sorry if this sounds harsh bmlang, but there is no way to sugar coat this... The single worst tires I have ever had -- bar none -- were Thornbirds. As you already know, these tires ARE dangerous on slippery roads. The idea of the tire design was an aggresive off road tread, that also worked well on road. Unfortunately, in practice, they are not good for either task. These tires are extremely noisy on the highway, with very little traction on wet or icy surfaces -- and they suck off road! Interco recommends mounting their 38.5 x 14.50-16LT (load rating is 2500 lbs.) Thornbirds on a 10" to 12" wide wheel, so going to 14" wide rims is not the answer. If you look at the profile of these tires, there should be little doubt as to why there are rubbing problems here. As I suggested at the top, I would seriously consider getting rid of these tires.

 

Driver's side drilled and tapped

Passenger's side drilled and tapped

Really easy and cheap fix and you can see that I lost very little turning radius. Besides are you really going to notice an extra 8" of extended radius?

 

One other option for the thornbirds is to cut off each 3rd inner tread lug on the fronts (the longest lug out), evenly with a sawzall, and have them rebalanced. I did this on my truck and it worked fine without having to mod my truck. I only did this because I had already paid for the tires, mounting, etc. and new I would be changing them as soon as they wore down enough (as someone said earlier these tire are worthless for any purpose other than "looking cool", they suck on wet pavement and in the mud plus you get the early morning flatspots from being a bias ply etc., these tires really suck - I wound up giving mine away and will never buy another thornbird). I switched over to XTerrains and they are a great all around tire, just a little narrow for my tastes. I'll be switching over to the 36x14.5 Parnelli Jones dirt grips in about a month when these X's are worn out, a buddy has those and they are really an awesome tire if you are considering switching. hehe

 

I'm running an 8" lift with interco 39" tires, front bumper has already been spaced, you can look at my gallery the only time mine rub is when I turn a real "HARD" turn, other than that no problems.