Re: [ihc] Tire & Wheel Questions

["T.R.E.Jr." <T_R_E_Jr@xxxxxxxxxxx>]

---Sorry, this one has been hiding in my inbox for some time now, just
thought I would touch on this before it gets lost again.

----- Original Message ----- 
From: "Mac @ TRIAD" <mac@domain.elided>

<snip>
> tread width.  always a question.  and never quite what the manufacturers
> tell you it is, either.  as specified in more detail below, our TravelAll
> runs tires listed by the factory as 33"x16.5"x12.5", and the 800A runs a
set
> labeled as 31"x15"x10.5".  the actual measurements of these tires,
however,
> differ from what they are labeled as.  the Scout's tires in reality
measure
> only 29.75" tall and have 9" treadwidth (the width of the sidewalls at
full
> inflation is 10.25", with 10.5" at the sidewall bulge where the tire rests
> on the ground).  the TravelAll's tires are 31.5" tall and have a
treadwidth
> of 11.25", with a sidewall width at full inflation of just over 12 inches,
> and a width of the sidewall bulge at the ground of 12.5".  when mounted on
a
> wheel and at full inflation, laying flat on a table or spinning freely, i
> have no doubt these tires measure what the factory says they should, at
> least for height.  when mounted on a vehicle and that vehicle's weight
> resting on them, the measurements fall quite short.  the spare tire on the
> TravelAll, unmounted on a rim and laying flat on the roof, has about 20%
> tread left on it, and measures 32" diameter.

---Mac, what the manufacturer says the tire is, is just what the tire is
when mounted on the rim  the tire was made for. When you consider the tire
is said to be 9.4" x 30.1" x 15"  (235 75 R15) when mounted on a 15 x 8"
rim, if you mount it on a 10" rim, the rubber you took to make it wider and
fit the rim, has to come from somewhere. Each manufacturer specifies what
rim each tire is made for and when you buy tires that are made for the rim,
the tire will be the specified height.

---For instance, I bought a set of Dunlop OWLs for the Scout two years ago.
The set I ordered were 265 75 R16s for a 16" x 8" rim. I mounted them on the
rims and they were 31.6" tall and 10.6" wide (sidewall to sidewall). If I
were to mount them on a rim that was 16" x 10" they would get shorter. If I
mounted them on 16" x 7" rims, they would be taller.


<snip>
> to be honest, i don't know much about wheel offset, either.  i've got an
> excellent old '70s offroad handbook put out by a guy named Bob Waar
> ("Offroad Handbook with back country travel tips" by Bob Waar, copyright
> 1975, H.P. Books, ISBN 0-912656-15-8), and it has a lot of really
excellent
> information in it.  according to this book, wheel offset is measured
> positively or negatively from the wheel mounting surface.  zero offset
> places the wheel mounting surface exactly centre of the wheel, positive
> offset is with more wheel outboard than inboard, and negative offset is
with
> more wheel inboard than outboard.  the book also says that you should get
> the measurements of the original wheels the vehicle came from the factory
> with, and recommends that when acquiring new wheels, one should get wheels
> with as close an offset to stock as possible.  i'm not absolutely
positive,
> but i'm fairly sure that most IHC products with the smaller 5-lug wheels
> came with zero offset.

---There is a tool for this, and the name of it escapes me now, so we will
just call it the offset finder. It looks like a large micrometer attached to
a bar with a clamp on each end. You mount this to the wheel well... somehow
and then slide ou the one end of the forcepts to the wheel mounting surface
of the axle/spindle. It tells you just what your offset should is, and then
by doing the math, using your desired width tire, it tells you what offset
you should use. The whole idea is to keep the mounting area as close to
center as possible as you stated. I believe someone said that the stock
offset for Scout rims was 4. FWIW, most custom rims for trucks are being
made with a 4-5 offset, but the companies like to hear the word custom.
However they have other sizes in stock and don't advertise, they might have
what you want. Never hurts to email or call a company and see what they have
on the shelf. You might also find something that is about to get scrapped
;-)


<snip>
> our Scout has 15x8" wheels up front and 15x10" wheels on back, these are
> what it came to us with.  it's running 31x10.5" tires all the way around.
> these tires appear to have exactly the right tread to rim width on the
> front...  but on the back, they look positively dangerous for offroad use.
> the rim overhangs the tread on these wheels by at least an inch on each
> side, which to my thinking puts WAY too much sidewall at risk for puncture
> in rough terrain.

---The rims were obviously made for a 7" wide rim, maybe even 7" wide
maximum. Some tires are made for 7-8" rims and that might be what you
have... or a tire made for a 7" rim only, but my first statement seems more
likely. If I am not mistaken, when you get into the standard sized tires as
oposed to metric, the 10.5" that your tire says is actually a 10'5" rim. The
265mm that my tires say, are actually sidewall-to-sidewall measurement (and
the manufacturer says the tire has a 9.5" tread IIRC). My rule of thumb is
to keep no less than 1.5" smaller on rim width in relation to tread for
street and 1-1/2" to 2" inset of rim to sidewall for off-road tires.


<snip>
> as far as it goes, i haven't seen any really good guidelines published
> anywhere, though that doesn't mean there aren't any.  my rule of thumb is
to
> run wheels about two to three inches skinnier than the tire being mounted
on
> them.  10.5" tires on 8" wheels, 12.5" tires on 9.5 to 10.5" wheels, and
so
> forth.  it's hard to get wheels in a width that meets this criteria for
> tires wider than 12.5", though.
<snip>
> as far as it goes, i haven't seen any really good guidelines published
> anywhere, though that doesn't mean there aren't any.  my rule of thumb is
to
> run wheels about two to three inches skinnier than the tire being mounted
on
> them.

---There was, a while back, in a Petersen's Publication. Back then I recall
them having some intelligence in their the tech department. It lasted three
issues IIRC. A wheels and tires article, a lift (dos and don'ts) article and
a meats for cheap lift article (or something to that effect). They broke
down the measuring system for the tires and explained the difference between
measurements in passenger vehicle tires and trucks. Also told how to easily
convert the metric to standard.


<snip>
 ... eventually i'd like
> to run a set of tires and wheels from a HMMWV (there's a guy locally here
> that sells these used--about 70% to 80% tread left--from the military for
> cheap).  HMMWV wheels are 16.5" on 8 lug, in exactly the same pattern as
> what my TravelAll uses.  the tires themselves vary from 36" to 38", and
are
> invariably Goodyears.  i don't remember the width, but i *think* they're
too
> wide for the mags i've currently got, hence the change to HMMWV wheels as
> well.  i'll need about 2" of lift front and rear, and about an inch all
the
> way around the rear fenders trimmed to fit 36", and i'm not keen to do
this
> anytime soon, so it's going to be a while before i try it.  but this is
one
> of the possible future plans, especially if we wind up staying in this
place
> for a long time.  the tires are cheap enough to justify the work required
to
> mount them, i think.  especially since i wanted to be able to run 36"
tires
> on this beast anyway.

---ARR ARR ARR ARR ARR ARR <Tim Taylor/Allen Grunt> I am soooo jealous. I
wish they made those tires in a 16", I would love to have some of those
meaty beasts on my Scout. I knwo I can easily swap axles on the Scout and
make the wheels 8 lug, hmmmmm, unless someone can come up with a larger
backing plate and caliper bracket for larger brake options. The biggest
thing I like about `em is that they are pretty much tall and narrow. Super
Swamper has a nice new tall and narrow that I was checking out a while back.
The LTBs. 4 Wheel Parts even had an insane sale price on them the second
month they had them. They were mounted and balanced on a set of black Rock
Crawlers. $540! Not bad considering the price per tire from them is $116.

---Thank you,
-T.R.E.Jr.
-`73 Scout II (StoneThrower)
-`51 Farmall H (Heinz)
-`49 IH fridge (presently unnamed and in need of a compressor)
-`49 Plymouth Special Deluxe 4-door Sedan (Papapalooza)