The Stovebolt Site Forums The Shop Area General Truck Talk tire sizes

Hi all I have a 58, 3600. It sits on 17.5 inch newish old school tires. I would like to put on radials because I hear it ride smoother and straighter. 1. Is this true? 2. I would like to lower thr profile a bit. Can I put 16' or 17 on these rims? I dont want to get into changing tie rods. 3 If I cant put 16 or 17 on these rims, Is it a problem getting 16 inch rims and tires that wont rub?
Thanks Rick

1; Yes, it will ride smoother. Straighter, not so much, as that's more of an alignment issue than a tire issue. 2; The only tire that will work on your existing wheels are the 17.5s. You will need to get replacement 16 or 17 inch wheels to use modern radials. 3; You'll want to look for a wheel with no more than 3 1/2" backspacing. There recently have been 8 lug 16" wheels released on the market, they may be worth looking in to.
Since you're loking for a lower profle tire than stock, I would suggest an LT245/75/16, which will maintain the proper load range to support the truck.

Thanks Bill this is all great info. I will see if I can find anything about the 16" or 17 8 lug wheel and tire. I am not sure what you mean by 3.5" backspacing. Is this the distance from the centre of the rim outward to the edge of the rim. on the motor side rather than the outside

Also Bill the truck wanders somewhat. Doesnt drift to one side all the time but wanders around. lots of steering required. Is this normal

You're pretty close. The backspace dimension is on the inside (motor side) of the wheel, but it is the measurement from the mounting surface where the wheel bolts to the hub to the edge of the rim.
On the wandering, I would say it's most likely the steering box is out of adjustment. There's an adjustment screw on the side of the steering box to take care of that. Another possible cause would be paly in the tie rods, especially the original rebuildable style. Those can be adjusted for play as well, you will need a drag link socket to do this.

Rickyt- I will agree with Longbox on going with the radial tires. Look for 16" rims off a 80's to mid 90's Ford Van. They seem so have a little more backspacing than their GM and Mopar counterparts. I have Ford rims on my 54, they clear everything just fine. You may also be able to find 17's off of a late model GM Truck or Van, but you will need to pay close attention the backspacing. I will have to disagree with LongBox55 on using LT tires though. Most of the Standard Load "SL" radial tires in the 245/75/R16 size have a load rating in the 2200-2400 range, which is equivilent to their bias ply 17.5" counterpart. These trucks only weigh in around 3600 lbs, even fully loaded you're still under 5000 lbs. Going up to a heavier LT tire doesn't really seem necessary, unless you need to beat out some kidney stones. My 09 F150 came with "SL" tires on it from the factory and it weighs over 5000lbs empty!

Hi guys thanks for your help. I understand what the backspacing is now. I wasnt clear in my explanation. I was trying to say the same thing. As for the steering adjustment, I have heard of that and am going to attempt that when I get 'er out in the spring. I have checked the tie rods and they are snug.

Whitedog, aren't I looking for less backspacing. I was assuming more backspacing means a wider tire which would get closer to rubbing on the tie rod. Also when you talk about getting rims off 80 to 90 faord etc. Where are you getting these old rims and parts from? Do you have ample scrap yards in your area. Or are there other places I could be looking
Again thanks for your help
Rick

On a 3/4 ton, I would not consider anything less than a C range tire (6 ply), even if I wasn't going to load it to capacity. While it is true the P rated Standard Load version (4 ply) of the tire mentioned has sufficient maximum load capacity, it is not designed to carry said load 100% of the time. I've seen plenty of tire failures from people using underrated tires on heavier trucks. The LT rated tires are only give a harsh ride if inflated to max pressure. run that at about 40-55 psi, they ride very well and will still handle the weight of the truck.
At the tire shop I work at as the brake and alignment mechanic, we've had a few customers come in wanting to either save money by buying P rated tires, or they want the white letter version of a tire not available in the LT, for their 3/4 tons. They always end up coming back with premature wear, or in 1 case involving a '72 C20 (whice was never loaded), sidewall failure.

RICKYT- Yes, you are right. I actually meant to say that the Ford rims have LESS backspacing than the GM or Dodge rims. My mistake, sorry for the confusion.
Actually, we do have quite a few junkyards around here. There's a few less now than there used to be, but we still have plenty. Anyhow, I actually got my rims for free. My Dad runs a service shop and when guys junk cars, they bring the wheels to him to dispose of the tires. They don't always come back for the rims.

Thanks for your help guys this helps me know a bit more of what to look for

Hi guys I took some measurements off my wheel. The rim is 18.25 across. The tire is 30 " across from one side to the other. The tire is 5.5" from the rim to the road. The tire says 8 17.5 LT. Does this all make sense.