NissanDiesel Forums

Sorry to ask such a basic question, but I couldn't find it in my manuals anywhere. What is the recommended tire size for these trucks? I am trying to figure out why my front tires rub on the firewall going over bumps with the wheels turned (driveways, turning around on hills etc). I have adjusted the ride height up to spec but the problem persists. There are 195-75R14 on the front now, is this the problem?
Also it occured to me that I should be adjusting my speedometer (mentally) and calculating my mileage figures to compensate for the 27X8.5R14's on the rear. I got an indicated 30 mpg (270 miles on 9 gallons) on a recent trip over the Cascades. I'd like to convert that to actual when I find out the stock tire size. Thanks much.

EvergreenSD wrote:What is the recommended tire size for these trucks?

The tire size may be indicated on the data plate that is riveted to the driver's side door jamb, and which includes the truck's production date.

Thanks for the tip. The plate on the door jamb specifies 185R15B. It does not give an aspect ratio. Is this enough of a difference to cause the rubbing or should I be looking somewhere else? What size tires are you running on the front? It doesn't seem likely to me that the caster could be off enough to cause this since the front end handles fairly well (though not like new) since I corrected the ride height. Funds are extremely limited for me right now or I would spring for new ball joints and an alignment. This truck is soon to be our only ride but the rubbing freaks out my wife. Is it possible that I have wheels with the wrong offset? Thanks again for all the sage advice, I couldn't do it without you.

EvergreenSD wrote:Thanks for the tip. The plate on the door jamb specifies 185R15B. It does not give an aspect ratio. Is this enough of a difference to cause the rubbing or should I be looking somewhere else? What size tires are you running on the front? It doesn't seem likely to me that the caster could be off enough to cause this since the front end handles fairly well (though not like new) since I corrected the ride height.

CAMBER is the small amount of wheel tilt you see when sighting along the length of the truck with steering straight ahead. CASTER (aka: king pin inclination) changes camber as you turn the wheels away from straight ahead. Less caster = less camber change when steered away from straight ahead.

My thought regarding caster is that it effects how close the wheel comes to to the rear of the inner fender. From the marks on the fender I think this problem has existed for awhile but I would certainly like to get it cleared up.

EvergreenSD wrote: My thought regarding caster is that it effects how close the wheel comes to the rear of the inner fender. From the marks on the fender I think this problem has existed for awhile but I would certainly like to get it cleared up.

Referring to the 1982 FSM 2wd truck, the wheels are 14". The 15" wheels were fitted only to 4wd.

A short course on WHEEL ALIGNMENT

Caster would have to be SEVERELY positive ... far outside the limits of shim adjustment to affect camber sufficient to make the tires touch the inner fender during a turn.

Front Suspension Tale

I had read your suspension tale previously, but what caught my eye this time is the photo where you are measureing the three inch gap between the rear tire edge and the fender well. I also have a 3" gap though it is the same amount front and rear and the control arms are mounted correctly. What size tires do you have on your front Phillip? The other thing I have noticed is that I believe that the outer edge of the tire rubs during turns but not the inner edge during turns in the other direction. This is what had me wondering if my front wheels might be incorrect. I am not sure where to find the specified offset for front wheels or how to measure the ones I have. In brief, I am willing to buy new tires in a slightly smaller size but I need to be sure that this will be enough to correct the problem before I go to the expense. I appreciate all of your insight and patience.

EvergreenSD wrote:I had read your suspension tale previously, but what caught my eye this time is the photo where you are measureing the three inch gap between the rear tire edge and the fender well. I also have a 3" gap though it is the same amount front and rear and the control arms are mounted correctly. What size tires do you have on your front Phillip?

The door jamb ID plate calls for 185SRx14. I have 185/75x14 passenger car tires installed. These particular Big O brand tires are a little small but make the steering very low effort.

EvergreenSD wrote: The other thing I have noticed is that I believe that the outer edge of the tire rubs during turns but not the inner edge during turns in the other direction. This is what had me wondering if my front wheels might be incorrect. I am not sure where to find the specified offset for front wheels or how to measure the ones I have. In brief, I am willing to buy new tires in a slightly smaller size but I need to be sure that this will be enough to correct the problem before I go to the expense. I appreciate all of your insight and patience.

14" ... not 15" on any 720 2wd truck.

Well I have figured out that my problem is the wheels. The pictures in Phillip's suspension tale made me realize that the rusty old wheel I have as the spare is actually a stock wheel, so then I had something to compare to. The outside rim of the stock wheel is 1" past the seating surface of the lug nuts. On the wheels I am currently using the rim is 3" out from the lug nut surface. The tires do stick out visibly from the wheel wells a bit. With the wheels turned all the way to the left, the driver's side wheel only clears the firewall by about 1/2" on the outside rear of the tire with no load on it.

Now I need to figure out if I can find new wheels inexpensively enough or if I should go hunting at the junkyard. I haven't learned how to estimate what a junkyard will charge for things nor have I been able to find a price for basic steel wheels yet. Any thoughts?

I painted my wheels bright orange so I will need to paint whatever I find to match before new tires go on. I am excited to get this sorted because I think it is really going to make the front end feel better and reduce steering effort. This is the only 720 I have driven so it can be tough to evaluate with nothing to compare to.

EvergreenSD wrote:Well I have figured out that my problem is the wheels. The pictures in Phillip's suspension tale made me realize that the rusty old wheel I have as the spare is actually a stock wheel, so then I had something to compare to. The outside rim of the stock wheel is 1" past the seating surface of the lug nuts. On the wheels I am currently using the rim is 3" out from the lug nut surface. The tires do stick out visibly from the wheel wells a bit. With the wheels turned all the way to the left, the driver's side wheel only clears the firewall by about 1/2" on the outside rear of the tire with no load on it. SNIP

Rim Offset. Ok, now you're onto something. While you're looking for the correct wheels, keep both "off-set" and total rim width stock. Steering effort will be lowest with the 185SR tires. BTS (back to stock).

EvergreenSD wrote:Now I need to figure out if I can find new wheels inexpensively enough or if I should go hunting at the junkyard. I haven't learned how to estimate what a junkyard will charge for things nor have I been able to find a price for basic steel wheels yet.

The U-Pull-It variety of JYs up here get about $10 for a steel wheel, when you can get them.

I don't have any stock 720 wheels here, but take a close look at the pics toward the bottom of this post ("Vashon truck"). They look like Les Schwab rims and IIRC are painted a medium blue. If you can find a set of "rollers" to put back on that truck, I bet that those wheels could be yours. Peter owns that truck, and it's definitely a parts truck.

The yard here in Eugene told me the same thing, $10 for a steel wheel with no tire. I went after work yesterday but I kind of ran out of time so I didn't get anything. It wasn't until I was on my way out that I found their mountain of wheels. I had been looking by the 720's; sometimes you just have to know what to ask for I'll probably go back tomorrow because Les Schwab wanted $25 each for used wheels. I will see if I can get lucky and find a matching pair with tires and save myself some $$$ I did find a set of four Pathfinder wheels but that's a whole other can of worms.

This concern is being forced onto the back burner by another problem. The cooler weather here has resurrected my cold-starting woes with a pronounced miss and a bunch of smoke. Not happy. I'll be pulling the injectors and having them rebuilt soon. The shop told me $50-60 each to rebuild them and that's going to put the squeeze on the old coin purse.

Also I am trying to sell our trusty Subaru right now so the Datsun will be our only car for my wife and I. That's alot of pressure on me and the old 720. Wish us luck . . .

EvergreenSD wrote: SNIP-
This concern is being forced onto the back burner by another problem. The cooler weather here has resurrected my cold-starting woes with a pronounced miss and a bunch of smoke. Not happy. I'll be pulling the injectors and having them rebuilt soon. The shop told me $50-60 each to rebuild them and that's going to put the squeeze on the old coin purse.

Also I am trying to sell our trusty Subaru right now so the Datsun will be our only car for my wife and I. That's alot of pressure on me and the old 720. Wish us luck . . .

Subject matter is continued in the SD22 Engine Forum.

Cold Weather Starting Difficulty

I just wanted to let you all know that I did get this sorted out. After a long time (two trips) mulling through the junkyard I found a pair of Datsun wheels that only set me back $20. After cleaning them up real well and painting them bright orange (an old Datsun's got to have a sense of humor) I had a set of 185/70R14 Kumhos mounted and the truck drives MUCH better. The truck is much more pleasant to drive now that it steers so much lighter and it also follows ruts much less and doesn't kick going over bumps. No more rubbing either. My wife is even more pleased than I since she used to struggle with making tight turns at low speed. Thanks for all your patience and help.

Love efforts that have a happy ending!