14" tire options?

[Wildthings]

[dixoncj]

[regis101]

Very interesting six pages. I never would have given a thought to tire pressure for the tire.
I even Googled tire air pressure vs ambient temp and found a chart.

Our Weekender has the 39fr 48rr sticker. The data plate gives the GVWR with fr and rr weights. I don't know if fuel and passengers are taken into account. No worries for now.

I crunched the numbers and came up with pressures for the
Herc Power CV 195's.

Great for the peace of mind if nothing else. Great baseline to work from.

Usually I just pumped them up to 10# of max and run with it, on any of my vehicles, for years. Hmphh.

Thanks again,
_________________
Peace, Regis

[geo_tonz]

[regis101]

Tireack lists them as Trailer tires (only)
http://www.tirerack.com/tires/tires.jsp?tireMake=Kumho&tireModel=Radial+857
_________________
Peace, Regis

[geo_tonz]

[Jon_slider]

The Hankook RA08 is also listed as a Trailer tire:
http://www.hankooktireusa.com/Product/product.aspx...FnCode=046

hmmmm...
I run Nokians
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My Soapboxes: Inflation; Handling; Gearing; Decoupling; Swepco

[regis101]

To each, their own.

I didn't care for the RA08's after they had some miles on them. iirc, they are a Summer tread.

I'm trying these out in the 195's. Only have <2k miles. They seem worthy so far and are listed as an all-season tire.
But I've noticed many glitches on many websites.
http://www.herculestire.com/tire-gallery/passenger-and-light-truck/light-truck/power-cv/
_________________
Peace, Regis

[Jon_slider]

[regis101]

If my math is correct, psi works out to 41fr and 44rr.
Data tags show 5160 GVWR, Fr 2646 , Rr 2866

The Hercules search shows a shop in Pleasanton. Valley Tire Service.

I think is was in the 5-6 hun range out the door for five on loose rims.
AND, they are about the only shop that knows how to read the red and yellow dots on the tires. But that's another thread.
_________________
Peace, Regis

[geo_tonz]

**edit: I was responding to comments which have now been edited out by the poster. Unable to delete my posting now.

You can see the thread I linked to for my impression of the Kumho 857.

I originally had Herc's on my van and didn't like them much, although they were old and fairly worn (not worn out but came with the van) so I'm not really giving them a fair shake. The Kumhos definitely track much more solidly than the Hercs did though and have less flex when cornering.
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"Ron Burgundy": 1991 Vanagon Multivan (Weekender) 2.1L Auto - Driver/Camper

[Jon_slider]

Herc 195R14
Max Load 2095
Max Psi 65

[regis101]

The data tag shows GVWR at 5160 . GAWR is, Fr 2646 so half of that is 1323. Rr 2866, so half of that is 1433.

I then used this formula?
Fr 1323/2094 x 65
Rr 1433/2094 x 65

Fr 41
Rr 44

The other tag on the hinge side of the door gives the 39 and 48 for the 185/r14 6 ply but I don't know what tire it was based upon.
_________________
Peace, Regis

[Jon_slider]

[regis101]

I'm kinda missing something. But it'll come.
How are the load inflation targets calculated.

I was thinking that per given axle weight, a specific tire gets inflated to meet that weight.
_________________
Peace, Regis

[Jon_slider]

> How are the load inflation targets calculated.

here is how I do it

VW used a 185 tire rated
1710 lbs at
55 psi
and they said to inflate to 43 front, in 1989

the way I do the math is
tire pressure for the 185 tire, divided by the max pressure, times the max load, like this
43/55x1710= 1337 pounds of load inflation

next use the 1337 in relation to the tire you have, example

195R14 tire rated
2095 lbs @
65 psi

calculate
vw load inflation, divided by new tire max load, times new tire max pressure, like this
1337/2095x65= 42 psi

this is the definitive source of info
http://www.roadhaus.com/tires/guideline.html

I hope that helps

your idea of using the GVWR is not bad, but its not how VW did it

what VW did is they told us what tire they used, and its specs, and they told us what inflation to use

they also told us what a load table says those pressures mean in terms of load capacity.
Load table VW used here:
http://www.roadhaus.com/tires/OE%20Tire%20Load%20Inflation%20Table.html

according to that table, the 185 tire at 43psi front, carried a load of 1480 pounds.

so the 1337 that I calculate linear math, is the same as what a load table calls 1480

but load tables are, in my opinion, exaggerated. I don't use 1480 for my math, I use the 1337

IF you wanted to use the 1480 target, for your 195 tire you would have to look up a load table for your tire, then find the pressure that produces 1480 on that tire.. I find that more complicated, and less valid, because load tables, in USA, assume that even with 0 air in the tire, that the tire can still carry 21% of the total load. So for a 185 tire, they assume that even totally flat, it can carry 21% of 1710, which is 359 pounds.
To me that is total bullshit. And in Europe they agree with me, that american tire load calculations are overly optimistic. Its all politics.

the linear math I use, says all of the load is carried by the air, and none of it by the tire carcass with no air in it. So my way is going to produce a higher air psi than a load table. Meaning, my way will use more air pressure than the load table. So my way is "safer", in my opinion.

Once you get a tire pressure that you think is in the right ballpark, you should still drive the vehicle and see if you are OK with it.

personally, I tend to like my tires on the harder side, to reduce body roll in curves, so my linear math, inflates higher, producing harder tires, that I prefer.
_________________
My Soapboxes: Inflation; Handling; Gearing; Decoupling; Swepco

[denwood]

Jon, what I found in the load tables, is that the relationship is not linear..so calculations may or may not be correct. In another thread, I did work through this example, and it looks like VW did use the GAWR at each axle in this syncro to set tire pressure recommendations:

"I can see where the confusion comes from, particularly as the AT2 tires are spec'd in some sizes as LT, in others as iso-metric. The jam sticker on your syncro shows 36 front and 40 psi rear, so OE tires were the Michelin MXL 205/70R-14. That reinforced tire carried 1580lbs at 40psi. It does not get de-rated as it is a specially reinforced passenger tire. So 40 psi (on the OE tires) at the rear gets you to 3160lbs (1580 x 2) over two tires. Guess what your vehicles rear GAWR is? 3042lbs.

Your new AT-2 tires are iso metric, therefore the load capacity of 1764lbs is rated at 36psi (different than for LT tires, where max load is specified at tire pressures of 50 for load rated C, 65psi for load D etc.). An iso metric 215/75R15 carries 1764lbs at 36psi, however in that particular size of General Grabber AT2, are not spec'd as LT tires. You should de-rate 10%. Therefore the load rating at 36 psi is more like 1587lbs when de-rated as required. An 87 Syncro Westy GAWR Front is 2866lbs, and 3042lbs rear. Your OE tire was spec'd at 36 PSI, so reading off the table (page A12 in link below for reinforced tires) for a OE Tire 97 load rating at 36 psi, we get 1433 lbs..so over two tires corresponds exactly to the front GAWR of 2866. So if you want to approximate OE pressure up front, From the link below, page A 11 (iso-metric load table), the pressure values for a tire with load rating of 100 (like your AT2s) indicate ~28psi up front, however we need to derate 10%, so 32 psi would be a safe minimum up front assuming GAWR of 2866lbs.

The pressure differential between front/back can be used to effect understeer/oversteer (as an autocrosser, this is basic tuning), however VW wasn't trying to do that with your van. The OE spec of 36psi front/40psi rear reflects the GAWR differential of ~200lbs. Chazz, if VW was trying to increase understeer (the so-called safer handling characteristic), they would increase pressure in the front over the rear...less pressure up front actually increases oversteer. This tendency on a properly aired Westy is evident if you enter a corner a bit "hot". Rather than braking, back off the throttle. The change in balance (and a bit of rear wheel compression braking) can be felt immediately at the wheel in terms of reduced understeer. The back end gets a bit lighter due to mass balance shifting forward...so you are helped around the corner. Autocrossing a well balanced car, slight trailing throttle oversteer is a great way to corner fast in a FWD car Smile

So based on a 215/75 R15 iso metric tire with a load rating of 100, derated for truck use, your minimum pressures to get close to OE spec for an 87 Syncro Westy should be ~32psi front, and ~36psi rear. There is no reason that you can't run 40 and 44 to improve highway behaviour, with a hit to ride harshness. I'm running the AT2 14s, therefore require 50psi in the back and 40psi front based on a 1990 2wd Westy GAWR. My personal comments on these tires are basically great ride, however somewhat vague on the highway with respect to stearing input. In other words, Ok, but not ideal IMHO.

All the numbers above came from the load tables here: http://www.toyotires.ca/sites/default/files/loadinflationtable.pdf "
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Cheers,
Dennis Wood
The Grape

[regis101]

On the vanagonauts site, they address tire pressure. If I'm reading correctly, the formula for (my) tires is very close , within a decimal of Jon's calc's.

It reads as follows.
OE tire max load X Sticker recommended PSI / OE tire max PSI

Then multiply that to the

New tire max PSI / New tire max load

My new PSI numbers come in at 41.4 Fr and 50.~ rr

A copy/paste from the Vanagonauts

**It is as follows:
[Original Tires Max Load Rating] * [Sticker's
Recommended P.S.I.] / [Original Tires Max P.S.I.] *
[New Tires Max P.S.I.] / [New Tires Max Load Rating]

The tire manufacturer should be able to provide you
with a load rating vs tire pressure chart also for
your particular tire.



These are the numbers that I use for my tires:
Original Tire - Load rating "C" or 1,433lbs @ 48 psi
MAX
New Tire - Load rating "96" or 1,609 lbs @ 44 psi MAX

Recommended Original Pressure, 39 psi Front, 48 psi
Rear

Calculated Pressure for my tires, 33 psi Front, 40 psi
Rear
** end copy/paste.

I'm still fu'd, huh.
_________________
Peace, Regis

[Jon_slider]

[regis101]

This is the article.

http://www.vanagonauts.com/Tire-Pressure4.htm
_________________
Peace, Regis