Date: Sat, 11 Jul 1998 23:02:14 EDT
Reply-To: SyncroHead@AOL.COM
Sender: Vanagon Mailing List <Vanagon@vanagon.com>
From: SyncroHead@AOL.COM
Subject: Tire Size Information (was: Re: Wheels & Deals)
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In a message dated 98-07-11 15:16:53 EDT, jeannemaly@email.msn.com wrote about
tire sizes for a Vanagon Syncro & the upcomming trip to South America:
> >This plan would be aided by using a light truck (LT) tire like the
> >BFGoodrich Radial All-Terrain T/A. Size 27x8.50R14LT.
> Is 27" the same as 205? <snip>
No. 27" tires are a bit larger. A larger tire works better in dirt or other
rough terrain. I'd expect most areas in South America won't have exactly
"interstates!
27" is a "nominal diameter of the tire. The actual diameter varies from maker
to maker & model to model and is usually about 25.5" to 26.5". The 205/70HR14
tires are about 24.5-25" in diameter.
> Do me a favor and tell me to shut up if I become really annoying.
Not annoying..................................................yet. :)
Tires are a much more complex subject than it would originally seem. There
are several different systems just to describe the size of a tire! Confusing
for someone without much experience.
PASSENGER CAR TIRES:
The "205" tires are sized "metric", "P-metric" or "euro" sized tires. The
format for this sizing method is described in this example:
Example: P205/70HR14
P=Passenger car tires. I think that not all maker put the "P" on the tires.
Basically if they don't have an "LT" in the size number, they're passenger car
tires.
205 = overall width of the tire in millimeters, basically the width of the
tire from side to side. Narrower tires would have numbers like 195/70HR14
which is 195mm wide and is 10mm (about 3/8") narrower. The next size up would
be 215/70HR14. In general, wider is better. This width is limited by the
width of the rim that you're mounting the tire on to. A 6" wide rim can take
a variety of tire widths, perhaps about 185 to 215. Tires generally are
somewhere between 155mm (very narrow, econo car size) and 285mm (very wide,
sports car size). Probably 9 of 10 cars on the road uses tires from 175mm to
215mm.
70 = the "aspect ratio" or "profile" of the tire. Keep reading, this is NOT
that technical...
The aspect ratio defines the proportion of the tire's shape. It is the
percentage of the tire's width as a percantage of it's height, the ratio of
height to width. Here when I discuss the tire's height, I don't mean the
overall height from ground to the top of the tire, but from the ground to the
bottom of the rim before the wheel is installed on the van. This height is
usually about 3" to 7". A tire 6" in height and 10" in width is a 60 series
tire. In our example size, the height of the tire is:
205mm x 70% = 143mm = 5.6". Now, you say "Why go to all this trouble with
percentages & stuff? - Just use the actual height!" Well, tire makers make
tires in "series" or families. The example tire is a 70 series tire. They
make a 60 series family of tires & so on. These range from about 35 series to
80 series. 35 series tires are VERY low profile and are only used on extreme
sports cars. These tend to look like the tire is flat! They're great for
cornering and handling. Quite poor for passenger comfort since the sidewalls
are so short that they have very little flex when hitting a bump. A lot of
"sporty" cars use low profile 50 or 60 series tires. 70 or 80 series tires
are often used on typicall passenger sedans wher passenger comfort is favored
over handling. Tall sidewalls like 70 or 80 series are better for dirt roads,
bumps, (occasional rocks) etc.
H = the "speed rating" of the tire. Our example is H speed rated. A rating
of H means that the tire is safe up to 130 MPH. In our Vanagons a speed
rating is not an important consideration, since they won"t go that fast unless
you've driven off a cliff! Many tires ar not speed rated.
Q=99 MPH, 160km/h
S=112 MPH, 180km/h
T=118 MPH, 190km/h
U=124 MPH, 200km/h
H=130 MPH, 210km/h
V=149 MPH, 240km/h
Z=149 MPH, 240km/h and over
W=168 MPH, 270km/h
Y=186 MPH, 300km/h
R = radial. Almost all tires now use radial construction.
14 = rim diameter in inches. This is the size of the rim that you're mounting
the tire onto. Yes, even in Europe they use rime measured in inches. Cars
typically use rims from 13" to 17" in diameter.
LIGHT TRUCK TIRES
"Light Truck" means pickups, vans, & sport utility vehicles - NOT trucks like
commericial vehicles or semis.
Example: 27x8.50R14LT (or LT27x8.50R14)
Some LT tires use the tire sizing method above for passenger cars, where "LT"
replaces the "P".
27 = the nominal overall diameter of the tire in inches. It's important to
call this "nominal" since I've found considerable differences between tire
makers. A 27" tire us typically 25.5" to 26.5" in diameter. I've never seen
a 27" tire that is actually 27" in diameter. 27" is about the smallest size
made for LT tires. Many full size pickups use 31" or 33" tires. For off-road
use larger is clearly better and many use up to 35" tires. 27" inchers are
about the largest size that a Vanagon can use without clearance problems or
modifications. Changing the overall tire diameter can also have a significant
impact on the overall gear ratio, and acceleration. On my Syncro the odometer
overstated the actual miles driven. With the 27" tires I have on it now the
odometer is within 0.5% accuracy, about as accurate as a car's odometer can
get. 27" tires are a bit difficult to install in the spare tire carrier and
require a bit of pushing. It helps to install a few large washers ABOVE the
carrier on the large fron mounting bolt. This allows the carrier to sit about
3/8" lower providing a skosh more room for the tire.
8.50 = the tire width in inches. This is typically 1" to 3" wider than the
rim that the tire is mounted on.
R = radial construction, again.
14 = rim diameter in inches, again. All Vanagons imported to the USA were
equipped with either 14" x 5.5" steel wheels or 14" x 6" alloy wheels. A few
rather rare Syncros used 16" wheels, but VW didn't import any to the USA.
For more detailed information see also:
http://www.tirerack.com/tires/tiretech/tiretech.htm
Also, it might be a good idea if all the Syncros on the trip used the same
make, model & size of tires and rims. The interchangibility might come in
very handy.
> Thanks, Jim
Glad to be of service.
Regards,
Jim Davis
87 GL Syncro
88 GL Wolfsburg
