C and D Load Tires

[fredn]

conti vanco
_________________
1982 Air Cooled Vanagon Carat Weekender Interior

[hippiepilot]

Thanks, I will see if my shop can order them for me.
_________________
83 air-cooled Westy
91 Carat (daily driver)
http://www.changeisland.com

[tomkat73]

Very few 'acceptable' 205R14C or D options out there. Here's one:

http://ssl.delti.com/cgi-bin/rshop.pl?dsco=150&...htweiter=1

Don't know if the Kumho 857 in this size is available in the US.

As r39o sez - a lot of us still running 14" wheels are on Hankook RA08's. 10mm width difference between 195 and 205 is not noticeable IMHO.

You WILL notice a vast improvement in the way your Carat handles, drives, tracks and stops with properly rated rubber.

Function and safety win out over fashion IMHO.
_________________
Tom

90 Bordeaux (Wine Wagon) Syncro Westy
87 Flash Silver (Silver Slug) Syncro Westy (1996-2011)
86 Bronze Beige Metallic Westy (Tourist Delivery - 1996)

[Ahwahnee]

[elsyr]

[hippiepilot]

[r39o]

[hippiepilot]

I'm so confused after reading this thread that I hope someone can tell me the "safe" tire to purchase. I currently have unsafe tires they are 205/70/14 95s and only have lasted about a year, with maybe 12K miles on them. The back left tire is starting to get a budge that was shown to me when I was having my rack installed. My door sticker on my 91 carat states http://www.vwvid.com/m/photos/view/tire-specs and I would like to stay with the 205's so my van doesn't look like it is running on bicycle tires. If I'm reading the sticker correctly as long as I purchase 205/70/14 97r I should be ok. I have found something close but it has a rating of 98t which is above the recommended rating. http://www.tirerack.com/tires/tires.jsp?tireMake=G...mpare1=yes I know these are cheap tires but I'm just using them as an example. Would it matter if the load range exceeds the recommended range? Or am I still lost in tire-land?
Thanks for any advice.
_________________
83 air-cooled Westy
91 Carat (daily driver)
http://www.changeisland.com

[jadatis]

You cant add a file to a post in this forum, I see now I am writing this.
Some fora have that possibility.
But there are sites like Imageshacj where you can post a file and paste the link to it in the reply. But if you have a Hotmail-adress or make one, you can use the skydrive like I did.
Then you can link to it the same way as I do.

But using power 1 is not that bad for calculating the pressure for a given load. Only the calculating back of the load the car-maker used for the original tires is unsertain in America, Because diferent powers where used for diferent kinds of tires.
P-tires or Standard load ,or I think A-load tires power 0,5 for calculating a load for a sertain pressure.
P-tires with aspect ratio of less then 50% ( 185/50R 14 ) power 0,65
From C load tires power 0.7 XL the same as Standard load.
After 2005 0.8 for A and B load tires ( P and XL), and still 0,7 for C and higher-load tires.
J.C Daws , from wich I have an article in the public map with link in my own reaction, states that if you keep using the power formula, youu better use for large tires with high refence-pressure power 0.9 to 0.95, so even higher then the 0.8 Europe uses for decades and I ask myself why they keep to 0.7.
If you want to turn the formula around to calculating a pressure for a sertain load you have to take a power of 1/ P . So the lower pressures from the original tires give lower loads when you calculate back with power 1 as you do. So the new tires are calculated for a to low load so still to soft . Power 1/ 0.5 = power 2 and that is the same as square.
Power 0.5 is the same as root, maybe this will make you understand what this powerthing is all about. But on a sciencetific calculator, as you can swich the calculator of windows too , there is a X^y button to use for it.

I will stop now because it is 23.00 H here and I am going to bed.
But this all to be continued.[/b]

[Jon_slider]

thanks for adding to the detail jadatis

my formula is linear, what your spreadsheet calls a power of 1 I think.. thanks for sharing your spreadsheet. I would like to know how to post mine..

if your formula produces higher inflation recommendation, I would like to understand how to use it.. I respect the fact that the equation may not be linear, and wonder what percent variance your pressure results are to the 42/52 the following example produces

here is my spreadsheet template.. dont know how to post it as a file yet, but someone could build similar

Original doorjamb
OE front psi 39
OE rear psi 48

Original tire specs
OE max load 1710
OE max psi 55

calculate load on front 1213 =oe front psi/oe max psi*OE max load
calculate load on rear 1492 =oe rear psi/oe max psi*oe max load

proposed new tire
new max load 1875
new max psi 65

proposed front psi 42 =calculated load on front/new max load*new max psi
proposed rear psi 52 =calculated load on rear/new max load*new max psi

I think thats enough hot air from me about tires for now, time to go driving..

enjoy the ride

[jadatis]

reaction to last post

What you are doing , with calculating part of the load = part of the pressure, can be translated in the universal formula the tire-makers use , as using power =1 in the formula, Europe uses 0.8 and America for LT tires still 0.7
Beter is to use for LT tires and higher 0.9 to 0.95 power.
So what you are doing is not so wrong, only the calculating back of the used loads for the old tires gives to low loads, because tire-maker in America calculated with power 0.7 at highest but mayby even 0,5. wich lead to lower pressures . Calculating this lower pressure back with power =1 you get lower loads then they realy calculated with .
Beter is to go from the Gross Axle Weight Ratings wich are mostly somewhere on the vehicle, and calculate with you power 1 the needed pressure.
Made a spreadsheet for that to, where you can fill in your own power and the data of the tire. Then you get the same list as the tire-manufacturer gives.
https://skydrive.live.com/?cid=a526e0eee092e6dc#cid=A526E0EEE092E6DC&id=A526E0EEE092E6DC%21601
You can give 3 powers and the formula is stated in the spreadsheet.

[Jon_slider]

> my inflation sticker says to be at 30 psi front and 44 psi rear.

I think you mean 30 front 40 rear, not 44?

If so, that means your van came with a 205x70x14 rated 1580 lbs @ 40 psi

1. now the math for what each tire carries at 30psi front and 40 psi rear
30/40*1580 = 1185 pound carrying capacity front
40/40*1580 = 1580 pound carrying capacity rear

> Wouldn't the tire pressures be relatively the same even with differnt sized tires as what the sticker says?

NO! each tire has its own load rating and max inflation. That producs vastly different doorjamb specs. For example, my doorjamb says 39 front, 48 rear, but it came with a 185R14 tire rated 1710 @ 55 psi.

to inflate the 185 tire to carry the same load as the 205 tire here is the math, starting with the results on item !.

1185/1710*55= 38 psi, very different from 30psi front
1580/1710*55= 51 psi, very different from 40 psi rear

> Am I thinking this out correctly?
not yet, but you are asking the right questions..
do you follow the explanation?

next math request:
> “185R14 — LT — 8 P.R. — Load Range D”
“Max load Single 1875 lbs at 65 P.S.I. cold”

> So if I crunch the figures correctly, I should inflate to 42 PSI front, and 52 rear?

YES YES YES! I have been heard, thank you!

lets review the math for those interested, first your stock tire was rated 1710@55 and was set to 39 front, 48 rear, lets calculate the load carrying inflations

39/55*1710= 1213 lbs front
48/55*1710= 1492

now to calculate the inflation of your tire rated 1875@65

1213/1875*65= 42 psi front
1492/1875*65= 52

[jadatis]

So now I will try to place a link.
https://skydrive.live.com/?cid=a526e0eee092e6dc#cid=A526E0EEE092E6DC&id=A526E0EEE092E6DC%21128
this leads to my public map with the pressurecalculation with temperature playing clicked on the I at the end. Then on the right you can click download.
After viruscheck you can open it in Excell or compatible programm to work with it. In the browser wont work because it cant handle some things in it.
If questions pup up , ask me here. And from this link you can navigate my complete public map by clicking the other "I " at maps and spreadsheets and articles the same way.

One thing I use in it is the Load- or Gripp-Percentage( further L%) and that is introduced by myself to get an idea of comfort and gripp. L% is the part what the real weight is of the weight you calculate the pressure for.
So 85% L% of 850 lbs can be calculated like this. 850/0,85 ( 85%) = 1000
, Then calculate the pressure for 1000 to get a loadpercentage of 85%.
This 85% is the border I concluded by reactions about bouncing. Under this discomfort begins by bouncing. Over 100% L% tire-damage begins.
So trick is to keep the pressure between L% of 85% and 100% , then you have a save pressure with comfort and good gripp .
The higher the L% the more gripp.

[jadatis]

I kept myself busy with calculating tire-pressure since 2007, with use of the formula the European tyre-makes use since decades, and the American since 2005. Learned myself Excell to make spreadsheets for it and translated a few to English to go worldwide with it.
Reacting on several fora in America , I discovered the diferences between the systems in America and Europe.
I will not post links in my first post , because sometimes they are seen as spamm.

In Europe C on the sidewall stands for Cargo or Comercial tire, and is mostly what in America is called a D-load tire with 65 psi.
But all this is not important, yust look what is written on the sidewall in the form of "maximum load xxxx lbs at yyy psi" ( Europe mostly KG and kPa, 100kPa =1 bar) . Then the XXXX is the maximum load and the YYY is the reference-pressure as it is called in the formula I got hold of of the ETRTO ( European Tire&Rimm Technical Organisation) .
For Normal car( P-tires or SL standard load) and Extra Load tires only the maximum pressure is written down and the reference pressure, so the pressure that is calculated with, is in Europe 36 psi and in America 35 psi.
For EXTRA Load/XL/reinforced ( all the same) Europe 2,9 bar, America 2,8 bar ( converse it yourself to psi). In europe many exeptions , in America not.
America calculates the maximum load for the referencepressure up to maximum speed of tire or if lower 99 miles/h( 160km/h) and puts it on the tire. Europe calculates the same way but rounds it down to the nearest load-index. Because Europe calculates for SL and EX load with a higher reference pressure, it mostly gives 1 load index higher load. But technically both tires are the same , so You can calculate the pressure for lower then maximum load for american tires with the better European formula. Though America now calculats since 2005 with the same power in the universal formula, there are many old lists in America whit to my opinion wrong calculation, wich gives to low pressures for the load , or to high load for the pressure, wich can give tire-damage at a higher speed.

Because a D load tire is stiffer then SL, it may deflect less then the SL.
This gives less surface on the ground, so at the same load the pressure must be higher to compensate that.

In my next post I will give a link to my public map of skydrive of hotmail, in wich maps with spreadsheets to calculate. Fist I want to read if I can that soon.

Greatings from Holland
Peter
And because I only signed in, to give this information, I will not introduce me in an opening topic.

[j_dirge]

When I bought my van (3rd owner, I think).. It had 4 Bridgestone Dueller ATs. The tires looked nice. Meaty. But they rode like crap... and showed very uneven wear.
In fairness, the front end was worn and the alignment was left out of whack for WAY too long.

I eventually flatted a rear tire, then shredded it (destroyed) getting to the side of the road.. At least I *think* that is how it went down.

To replace those tires, I was in a pinch and installed two P-rated Michelins.
They were improperly sized (225/70r14), and they were under-rated sidewall. They handled better than the BstDATs, but I could not rotate since they would not fit on the front without a spacer. I eventually found 2 OE sized tires new and left them on the front. We drove 20k on that setup.. Mixed driving, heavy loads, no loads. Snow, rain, dry.

That entire mess has since been reworked.. 16s all around.

Moral of my story. I think I could destroy ANY tire if I tried.
But I'd not go back to P-rated tires if I had ANY choice in the matter. And for me, a cost difference of $150 for 4 properly rated, properly sized, tires is chump change.

There's other places to skimp.. tires are not the place to skimp.
Nor is the "look" of the tire at all important when stacked against rating and handling.

Your experiences, mileage, and opinions may vary.
_________________
-89 GL Westy, SVX.. finally.

-57 pan f/g buggy with a 67 pancake Type 3 "S"
"Jimi Hendrix owned one. Richard Nixon did not"
-Grand Tour, Season 1, episodes 4 and 5

[0to60in6min]

here's my experience with passenger tires on an 85' Weekender...

in 1990 I bought an 85' Weekender with no knowledge on what tires should I get.. After a year of purchase, it need new tires... so I got a set of 205/70/14 of passenger tires, the guys at the tires shop didn't tell me what kind to get...

300 miles later, fully loaded, me and my wife 2 kids and camping gear we went to Death Valley. On the 395 near Adelanto, one of the rear tire blew up and we got to the road side OK. Guess what..? a fairly big gash on the side wall...I put the spare on, get another tire in town and keep going...

when we got back home I talked to another tire shop and they recommend LT (light truck) tires.. I got them but forgot what brand because it was so long ago...

now my current Carat is running on 195 Hankook RA08. 2 years ago I wanted 205 Vredestein but they are out of stock and waiting list is 6 months or more and I can't wait...

my syncro has BFG 27 X 8.50 R14 LT/C but it's another story

so in short DO NOT get passenger tires for vanagon.. you could hurt yourself your family or hurt someone too...

http://www.vanagon.com/info/tires/index.htm

[Ahwahnee]

That's about what I get when I do the numbers (by that formula) for my Hankooks. I have always used the door jamb spec for those but may try the slightly higher pressure as see how it feels/rides/handles.

[Typhon2222]

[Randy in Maine]

[GWTWTLW]