Stock L320 tire size? (Decision made, pics!)

[KFunk740]

OK, so I got really lucky on the tire size.  I didn't pay attention to 'tread width.'  These kinds of measurements aren't used on most online tire calculators.  Even though the section width is 195mm from outer sidewall to outer sidewall on the proper rim width, the width of the tread itself on the Hankooks is only 4.8", compared to 5.5" or so on normal 195s  That actually puts it pretty damn near the original bias ply tire size in terms of tread width, and thus I ended up with the right tall/skinny tires that I wanted.  I would've been OK with wider tread widths, but this seems more appropriate.

 

The steering is light, the ride is comfortable, and it really brings down the RPMs compared to my 195/60-14s (still have no tach to tell how much, though).  It can still haul a heavy load up hills just as well, too (maybe even better).  I've been hauling mulch home every day, and have done the same sized load with both sets of wheels/tires.

 

I still need to borrow a GPS to determine if speedo is accurate, but it feels much closer now.

 

This is what I got:

http://www.summitracing.com/parts/hkt-10702

 

Actually not much different than these:

http://www.cokertire.com/695-14-bf-goodrich-5-8-whitewall-tire.html

 

The BFGoodrichs have a much more impressive shape, but the Hankooks are pretty damn close in terms of dimensions.

 

Whatcha think?

[DanielC]

That looks like a really good "close to stock size" tire for almost every Datsun truck from 320 to 620.

 

I like the red truck, red wheel, white stripe sidewall, stock hubcap look.

[wayno]

Stock 620 hubcap look Daniel, 320 hubcaps are really hard to find.

[KFunk740]

Stock 620 hubcap look Daniel, 320 hubcaps are really hard to find.

Yeah, more than 99.999% of people wouldn't know the difference, though.  If I had real 320 hubcaps, I don't think I'd want to risk losing them on a daily driver.

The wheels came with the truck (still have 2 extra), along with three 620 hubcaps.  I bought 2 more 620 hubcaps on ebay.

[Stoffregen Motorsports]

They look good. I like 'em skinny.

[KFunk740]

Any idea what kind of pressure I should be running?  The 320 manual isn't much help.  It says 22 to 24 psi in the front, depending on model (which isn't clear).  It says anywhere from 30 to 60psi in the rear, depending on the model.

 

For now I've been doing 23psi in front and 33psi in rear, but I have no idea how air pressures should be in a truck for the best setup.  I'm used to adjusting pressures for handling and racing. :confused:

[DanielC]

"I'm used to adjusting pressures for handling and racing. :confused:"

 

Then you probably know more about adjusting the pressure than the most of us do!

 

I think the 320 was rated to carry one ton of payload, and this was probably done in some countries of the world that did not have full sized "American" pick ups.

Adjust the pressure too high, the truck rides even harder that is does now, but fuel mileage increases.  And the center of the tires wears more.  Adjust the pressure too low, the truck rides smoother, but wears the edges of the tire more than the center.  Fuel economy also suffers.

[datsunaholic]

Also, bear in mind the Factory ratings were for bias ply, tube tires.  These are tubeless radials.   Radials generally use more pressure, but not always.

 

I'm no expert on tire pressure... I generally run 30-35, depending on the tire rating, but the key is, more load, more pressure needed.  On a 320, unless the bed is loaded the front weighs more, so it should have more pressure, BUT if you plan on hauling heavy weight the rear would need to go up.

[KFunk740]

Ah, so maybe I should go up some in the front?  22 to 24 seemed low.  I may put it closer to 30.

 

I've been hauling loads of mulch that probably weigh 400 to 800 lbs. the last 4 days, along with a passenger.  So more pressure in back is probably better.  I didn't know if too much, plus weight, might be too hard on the tires though.

 

With my cars I usually go with high pressure (35psi or so) in the front for sharper steering, but if you go too much the front tires lose grip in the corner.  I go low pressure (27psi or so) in the rear to make it a little more flexible and grip better.  If you go too high the rear will lose grip.  This is with very light RWD cars though and extensive suspension work. :)

[datsunaholic]

If you drive a 320 fast enough that 35PSI in the tires makes any difference in handling, you've got more balls than me.  Then again, I've never even chirped the tires on my trucks (except the Chevy which has lockers in both axles and hates turning under acceleration), and at 35PSI I get around 60,000 miles on 35,000 mile rated tires.

[KFunk740]

If you drive a 320 fast enough that 35PSI in the tires makes any difference in handling, you've got more balls than me.  Then again, I've never even chirped the tires on my trucks (except the Chevy which has lockers in both axles and hates turning under acceleration), and at 35PSI I get around 60,000 miles on 35,000 mile rated tires.

 

I actually did run the 320 at an autocross fun event once, for fun.  Too bad nobody got any pics.  I managed to get the rear end to come around a bit, but it was a struggle.  The bigger problems were rear brake drums locking up, spilling gas, and pinning my left arm against the door in tight corners which makes it difficult to steer.

Nothing too fast at all, but a good way to find the weak points of the vehicle while not going very fast in a controlled environment.  Afterwards I got new brake drums, and a better gas cap.

[K_trip]

- removed -
 

[KFunk740]

Neat truck, it sounds like you're having fun with it AND getting work done with it - very cool B)

 

You might find dialing in the tire pressure based on contact patch better for your truck, instead of the "handling" approach you use on your cars. A poor-mans approach to dial in pressure to adjust the contact patch is to simply drive it over dry pavement with a puddle of water.  You'll want to take a look at the tread pattern left behind from the puddle, to see that you're getting all of the tread making contact. 

 

I like filling the tires up to max pressure, do the drive-thru a puddle thing, look at the tread pattern left on the ground - let some air out, repeat until full contact is being made.

 

Cool looking Datsun you've got there!

 

Ah, which gives me an idea, which may apply to both racing and hauling!

 

I forgot one of the most useful functions of my new infrared temp gun ($25).  The same basic idea as yours.  You just measure the temps across the width of the tread after driving/racing for a bit.  If its uneven (hot in center, or on shoulders), you know you're not making good contact with the ground, and you adjust as such.  Some of the better autocrossers did that before, but I had to wait until prices of IR temp guns came down to reasonable levels.  I will give it a shot in a little while, and see if it works.

[K_trip]

- removed -

[satcat808]

OK, so I got really lucky on the tire size.  I didn't pay attention to 'tread width.'  These kinds of measurements aren't used on most online tire calculators.  Even though the section width is 195mm from outer sidewall to outer sidewall on the proper rim width, the width of the tread itself on the Hankooks is only 4.8", compared to 5.5" or so on normal 195s  That actually puts it pretty damn near the original bias ply tire size in terms of tread width, and thus I ended up with the right tall/skinny tires that I wanted.  I would've been OK with wider tread widths, but this seems more appropriate.

 

The steering is light, the ride is comfortable, and it really brings down the RPMs compared to my 195/60-14s (still have no tach to tell how much, though).  It can still haul a heavy load up hills just as well, too (maybe even better).  I've been hauling mulch home every day, and have done the same sized load with both sets of wheels/tires.

 

I still need to borrow a GPS to determine if speedo is accurate, but it feels much closer now.

 

This is what I got:

http://www.summitracing.com/parts/hkt-10702

 

Actually not much different than these:

http://www.cokertire.com/695-14-bf-goodrich-5-8-whitewall-tire.html

 

The BFGoodrichs have a much more impressive shape, but the Hankooks are pretty damn close in terms of dimensions.

 

Whatcha think?

 

 

Aloha K.

 

Looks great!!!  May have to get a set myself.  

[KFunk740]

It sounds like you "caught the drift of it" (pun intended) ... I just offered my poor-man's approach.

 

Of course there is a simplification of principles being applied here - that is - assuming maximum tread contact is best.

My poor-man's approach works well to maximize tire wear, getting the most miles out of them.  We rotate regularly too.

Racing is where this simplification of principles may be an issue, but it's a good starting point.  Wow, a new IR gun for $25 :)

 

 

I tried the temp gun shortly after hauling mulch home yesterday.  Fairly even 99 to 100F across the tread in the back.  In the front it was 101 or or so on the shoulders, and 99 or so in the center.  Sounds like I just need a bit more air pressure in the front.

 

Yeah, the IR thing is fun to have.  I forget if I got it through Harbor Freight or Amazon, but I read lots of reviews to make sure it was decent.  It's just fun for measuring temps of anything around the house, and I use it as a laser pointer occasionally when I'm teaching (if I can't find my regular laser pointer).

Soon I'm going to get a USB borescope for just $15 off Amazon, and I'll hook it to my tablet computer.  Fun tools are are cheap these days!

[Stoffregen Motorsports]

Word to the wise, tires don't always wear in the middle when pressure is high. Most modern tires actually wear in the center when the pressure is too low, because the pressure keeps the sidewalls pushed out. Old bias ply tires definitely wore "the old way" and skinny modern tires may too. My advice...wear out a set and then get back to us!