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Tue Apr 13, 2010 12:25 pm

Folks, I've searched through old threads and read several discussing the appropriate PSI for inflating tires. But I'm such a newb to all this — I know bike tires, but not car ones — that I don't think I understand most of what I read. So apologies in advance.

We recently bought a 1988 Westy (2 WD, AT). It came with four Signet Radial SV-820 tires.

According to the BusDepot ( http://www.ratwell.com/technical/TirePhotos.html#signetsv820 ), these are the stats for the tire:
size: 185R14C
load index: 102
speed rating: P
load range: LRD
load rating: 1875 lbs
max pressure: 65 psi

Could somebody help me figure out how high to pump them? I've been running them at 37-38 psi, but am wondering if this is too low.

I do know that my steering feels mushy, and that we're getting something like 15 MPG, which seems low.

Reading other threads here, I see that some owners with other 185R14C tires are running them as high as 40-55 psi, but they're not using this particular brand, and I don't know whether all 185R14C's are the same in this regard.

<flails around, begs for help>

Tue Apr 13, 2010 12:44 pm

I have Agillis 81's and I run 40 in the front and 50 in the back.

Tue Apr 13, 2010 12:49 pm

The Diesel I have sitting out back says 38 front, 55 rear for a 185R14 6 ply. This should be considered just a starting point. Adjust as needed to give good handling and wear.

Tue Apr 13, 2010 1:01 pm

I have Yokohama LT 195/75/14 Y370 tires and I run 50psi front and rear. That's what the tire shop recommended.

Tue Apr 13, 2010 2:09 pm

Typhon2222 wrote:

size: 185R14C
load index: 102
speed rating: P
load range: LRD
load rating: 1875 lbs
max pressure: 65 psi

Reading other threads here, I see that some owners with other 185R14C tires are running them as high as 40-55 psi, but they're not using this particular brand, and I don't know whether all 185R14C's are the same in this regard.

How high you go with pressure is relative to the particular tire.
The manufacturer will tell you that you can go up to 98% or so of the max pressure that's shown on the tire sidewall, and to never exceed that.

My last set of 185r14 vanco's had the same numbers that you've listed,
load D, 1875#, max 65, and I normally ran them at 60#.
You can run them at a lower pressure for a softer ride, but you'll give up a little bit to gas mileage and tire wear.

Some folks religiously stick to the pressure recommended by VW, regardless of the tire they have on there, which seems a little strange, such as a posting I read yesterday where the guy says he runs at 50psi even though the tire is rated at 35max.

Tue Apr 13, 2010 2:14 pm

37-38psi seems kind of low..

When I had 'em, I ran my fronts (185/85r14 Load rated C) at 45ish psi.. and the rears a bit higher... 48-50. Beyond that they felt like running on bicycle racing wheels.

I would find them sometimes losing air to just below 40.. but I never saw worse than 17mpg in town.. and usually 19-20 HWY.

You may have some tune and/or gas delivery issues in addition to underinflated tires.
Fuel filter clean? Run some injector cleaner?

Tue Apr 13, 2010 2:23 pm

Fifty in the front and fifty in the rear on Yokohama 185R14 Y356 .Nice even tire wear and a smooth comfortable ride.

Tue Apr 13, 2010 2:33 pm

This question came up a little while ago and my van was still in storage. It's out now and I looked last week.The proper tire psi is marked on the panel inside the front door.

Of course today my van is in the body shop and I'm at work but I'm pretty sure it's 39 front and 48 rear. With a tire with a higher max psi you could obviously run them higher. I'm not certain tire wear and fuel mileage would be affected at all. You should at least run them at the minimums.

I have a TDI Golf and my last tires were filled with nitrogen because the sales person said some people get up to 10% better mileage. That would be significant in this car. It was a load of bull.

In a Westy why would one want to add any "extra pressure"?

Brian. :wink:

Tue Apr 13, 2010 3:03 pm

I run my BFG's at 50 PSI all the time. I like having as much extra load rating as I can possibly get. The ride is a little stiffer but I like the peace of mind.

Especially after weighing myself last weekend. 5200 lbs with a half tank of gas and very little gear. holy cr@p! I always figured I weighed about 4000 empty. I think the BFG's are rated at 1768 each at 50 PSI. Fully loaded for a vacation is still cutting it close if you're not aired up properly. I had figured last summer that we were pushing 6000 pounds but after weighing myself empty I bet we were closer to 6500 or so. 125 pounds per tire isn't a lot of cushion.

Tue Apr 13, 2010 3:08 pm

I have those tires and I usually run 55 rear, 45 front if I recall correctly.

Wed Apr 14, 2010 12:21 pm

Thanks guys! Good to know. I'm definitely going to pump mine up, maybe 45 front and 50 rear, and give them a try. :D

Wed Apr 14, 2010 12:38 pm

Typhon2222 wrote: We recently bought a 1988 Westy (2 WD, AT)>

Automatic Transmission vans usually have lower mpg so it is possible that you don't have a tune/fuel delivery issue. My westy AT has similar mpgs.

Wed Apr 14, 2010 12:39 pm

try this formula as a starting point

van weight divided by max load capacity times max psi

4 tires, 1875lbs load each, at 65psi
assume for sake of example a vanagon that weighs 4000lbs loaded, but find out for your own Van (my loaded syncro westy weighs 4750)

add up the load capacity of all 4 wheels..4 x 1875 =7500

run the formula with values plugged in
4000/7500*65= 43psi front, +4 rear

source
http://www.4x4now.com/sfjun96.htm
"Tire Pressure and Footprints

Right next to your wheel, on the tire, find the small black print that specifies maximum load pressure. For example, my BFGoodrich Radial All-Terrain T/A 30x9.50R15LTs state 1990 pounds at 50 pounds per square inch (PSI) cold. Most folks, generally including those who install tires, run them up close to this, and neglect the actual term, "MAX. LOAD" pressure. The street pressure, TREAD FOOTPRINT figure below represents Coyote assessed over inflation.

Do you really need maximum load pressure?

Consider that standing flat and level (static), loaded the way you normally run is one thing. Now further consider you lose full tread width contact as the 4X cruises at higher and higher speeds. Centrifugal force tries to increase the diameter of the tread. You only have to look at dragster tires when they light 'em up to convince yourself of this tire reality. The sidewalls tend to hold the outer edges closer to their static diameter than the center of the tread and hence the center of the tread spins into an ever increasing diameter with increased speed. In other words, while moving at highway speeds, the tire is trying to run more on the center of the tread than the edge. That’s why I feel my full width, static contact test (described below) is conservative. My tire life and wear pattern prove putting more rubber on the ground increases longevity.
Full tread width contact, street pressure

Since this article deals with sand tire pressure, see a back issue of Ecological 4-Wheeling for full details on how to safely determine your exact, full tread width contact, street pressure. Summarizing Tire Pressure, April, 1990 4-Wheeling, you don’t want to overheat the tire and should only be able to slip a business card under the outside and inside edges of the tread less than 1/4 inch. Reprints of past 4-Wheeling articles available for $4.00 each.

Follow along with some arithmetic that scopes in the same results. Four tires times 2000 pounds each (1990 MAX. LOAD rounded up to simplify math) equals 8000 pounds total (tire) load capacity. My Explorer weighs 4000 (3800 rounded up), or half the maximum capacity of all four tires combined. That roughly says half the pressure should yield ample load capacity.

As a result of both methods above, I run 26 PSI, night and day, seven days a week, and typically get 60,000 to 80,000 miles out of a set of BFG T/As, including sand runs at much lower pressure. I trust this information will add practicality to determining your street pressure and encourage you to accept overall lower tire pressure."