[StanVan]

As a new member, I've noticed that a quick tutorial about tires might help in answering some questions. Not necessarily about what size will fit what year, but some basic info that could help answer questions before you ask. Basically what the numbers mean, and more important, making sure that AWD owners get what they need. It has been pointed out that AWD owners already know that different size tires don't do well, but do they know why, or know when they are being led astray by a tire dealer?

The sizing is a 3 part "sentence". The last part of the tire size is the easiest. It's the size of the rim. I believe our vehicles(stock) take 15". The first part is the width, in millimeters. Here's the tricky part. The middle part is a percentage of the first part, and represents tire height. So this means that the height of a 235/70/15 is different from a 245/70/15. Height has everything to do with circumference, and that has a dramatic affect on AWD vehicles.

How I learned this lesson: I bought a set of 4 tires. They sold me(on the receipt) 70 series size tires, but the tire they installed was 75 series. Not a problem in itself, but 2 years later, when I went to another branch of the same company to get 2 of them replaced, I flashed the original receipt and they sold me the 70 series. The difference between 70s on the front, and 75s on the rear ate up my transfer case in about 3 weeks. It was my transmission guy that figured out why, and that info forced the tire company to pay for the transfer case repair, about $800.00, about 7 or 8 years ago.

This experience has taught me that I should never trust that I actually get what I bought.

 

[DanoT]

Maybe someone can help me. If I get Impala SS rims what tire size should I put on to avoid rubbing? The van is stock height anyone have these and have luck with there tire size?

 

[StanVan]

I believe this is being discussed here: viewtopic.php?f=66&t=1033

 

[astroturf91]

Wow, thanks, great post. I just got my van and the previous owner had truck tires on the rear. They are fugly! Thanks for posting this.

 

[cesar_glez]

Hello, i'm thinking to put a set of 2008 tahoe rims on my 2005 astro van awd, is that posible? if yes i want to know what tire size i will need too....... My van is as factory any modifications

 

[chevy57bert]

Maybe this helps.
Tire Sizing conversion

 

[GaryZ]

Good info StanVan. I have lost count of the discussions that I have had with guys trying to get them to understand aspect ratio. The conversation usually starts with them saying "I want wide tires, maybe 60's".

 

[tedanderson]

The conversation usually starts with them saying "I want wide tires, maybe 60's".

Yeah.. that gets me too... :rofl:

But they probably say that because most plus sizing custom wheel mods start with 60 series tires.

 

[webcat]

 

[94 Van Guy]

Turf gave me this site, makes comparisons easy.

http://www.rimsntires.com/rt_specs.jsp

You can enter what ever size you want and see all the specs, way kool.

 

[Uncle Fester]

Here is a GREAT link (IMHO) for sizing up, down, wider, or skinnier tire sizing . . . . .

http://www.miata.net/garage/tirecalc.html
:bow:

 

[doyoulikeithere]

I'm not positive how yur sposed to measure these rims, but
Here is a set of BFG T/A 275-60-15 on rear, and 245-60-15 on front, on AR 15x7.5 rims I spose.
The sliding door opens all the way. Fronts dont rub in sharp turns or bumps.

 

[JT!]

i'd like to add to this great post:

For AWD owners:

-not all tire brands / models are made to equal diameters.
-it is important that you ROTATE your tires frequently, front-to-back only ALWAYS keeping your tires on the same side of the vehicle.
-keep the same air pressure, all around.
-if you replace a tire, unless they are within 5000mi or km, you will be running a larger diameter on the new tire. best to find a used one with similar tread depth or youll have to buy a whole set of 4

 

[TontoYoder]

..... The last part of the tire size is the easiest. It's the size of the rim. I believe our vehicles(stock) take 15". .....

Is that part true?
My 95 Astro quit, so I bought a 2004 to replace it.
When I needed a new tire this past weekend, the stock size was listed as 215/70/16 so that's what I had installed.

BTW, I felt silly driving on the donut spare, so I thought I'd get a used tire for a leftover rim from the 95 and make that my spare. Then I realized it WAS a 15 inch rim/ tire from the 95 and 5 lugs, not six (as on the 2004).

 

[JT!]

2003-2005 models of our van have 16'' rims x 6 lugs
2002 and older run on 15'' rims x 5 lugs.

 

[Mr. Phudd]

I have a 2001 2wld stock it has bald 235/70/15 I want to put on 235/75/15 (all 4) should I try some used 235s to make sure the front will work ?

 

[brickyard]

The stock tire size for a 2001 2wd should be 215/75/15. This creates an overall diameter (including the tire) of 27.70" when changing the width, aspect ratio, or rim diameter you should always strive to maintain, as close as possible, the overall diameter. The biggest affect of altering this to much will be a change in the accuracy of your speedometer because the revolutions per mile will change enough to through it off. With newer cars that have traction control, stability control and those type of computer aided features, altering the overall diamter to much will cause these systems to have a fit and constantly make adjustments becuase the revolutions per mile will make it think something is wrong and it will try to compensate for it. A 235/75/15 tire will have an overall diameter of 28.8" and be 1" taller than stock. That will also make your van sit 1" higher off the ground and is enough to most likely make your speedometer inaccurate.

If you want to put a 235mm wide tire on your van, you should go with a 70 series tire. A 235/70/15 tire will have an overall diameter of 27.95" and only be 1/4" taller than stock. The other thing you must always keep in mind when putting wider tires on a vehicle is the rim width. There is a point where it is unsafe to have a much wider tire on a narrower rim. If you look at the specs for a tire, it will tell you the rim width range for it. A 235mm tire should have a rim width range between ~6" to 8".

I know a 235mm tire will fit on the Astro since that is what came stock on my 98. I purchased it with the sport option that included 235/65/15 white oulined letter tires. I maintained those for a while but they were only made by Goodyear and that is a very odd size that nobody made. I don't think you can even get them anymore from any manufacturer and they were very expensive.

For those that want to learn how I arrived at most of my numbers, it is just a matter of doing some math. Let's use the example of the 215/75/15 tire.

1. Take the width of the tire in milimeters, 215 and multiply it by the aspect ratio, 75. (215 x .75 = 161.25mm) This tells you the height of the sidewall.
2. Since there is a sidewall above and below the rim, we need to multiply step 1 by 2. (161.25 x 2 = 322.5mm)
3. The rims are measured in inches, not mm, so we need to convert the sidewall height to inches. there is 25.4mm to 1" so, (322.5/25.4 = 12.70")
4. Now we just need to add the sidewall height to the rim diameter and we will have the overall diameter. (15" + 12.7" = 27.70")

Just follow these same calculations for your new tire/rim size and you can see how close it matches the original height.

Hope that helps.

 

[Mr. Phudd]

I put the new 235 75 15 on the van they are a tight fit I mean tight !

 

[thegreenmachine]

......... A 235/75/15 tire will have an overall diameter of 28.8" and be 1" taller than stock. That will also make your van sit 1" higher off the ground and is enough to most likely make your speedometer inaccurate.

actually it will make your van sit 1/2" higher. measurements are from center of hub.
30" tires make it go up 1 1/2"

 

[buggymancan]

I plan to run a 245/70r16 tire on my Astro. Stated tire casing width is 9.75 (tred width 7.6). Has anybody it a 245/70R16 on the Astro. Seems that the inside tire casing will get awfully close to the rh front sway bar when front wheels are cranked.
Any input?