Re: [ihc] Tire & Wheel Questions

["Ryan Moore" <baradium@xxxxxxxxxxx>]

----- Original Message ----- 
From: "T.R.E.Jr." <T_R_E_Jr@domain.elided>
To: "Mac @ TRIAD" <mac@domain.elided>; "Allan Ericson"
<lowvolt@domain.elided>; "Peter Ferris" <binder@domain.elided>; "IHC Digest"
<ihc-digest@domain.elided>
Sent: Thursday, October 30, 2003 04:08
Subject: Re: [ihc] Tire & Wheel Questions


> ---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>

In any case, you do *not* want to put a 10.50" tire on a 10.50" rim!   BTW,
a 10'5" rim is pretty big IMO!

That width is not the width of the rim you want to use....   10.50 you want
around a 7 or 8" wide rim...

-Ryan