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Old 06-04-2010, 12:03 PM   #1
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Suggestions for tire size for 17" rim in new 2010 EB 4WD

This is an interesting article previously posted on this forum on the physics behind tire tread and size.



http://www.expeditionswest.com/research ... _rev1.html



I am in the process of building a EB 50 SMB and live in Portland, Oregon--land of mud, wet roads, snow and ice. This will be a year round camping vehicle, especially during the ski season. What would be the ideal tire size for the 17" rim? Would a 265 be better with 1" less width and almost 1" less radius? Or even 255? I would avoid the low profile tires and have .75 or greater height to width ratio. SMB recommends the Nitto Terra Grapplers 285, but I hear they are poor in the ice and snow.

Any thoughts are appreciated.

John.
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Old 06-04-2010, 12:37 PM   #2
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Re: Suggestions for tire size for 17" rim in new 2010 EB 4WD

I am debating tire size myself right now as I currently have 315/75/16 terra nitto and they are big 35" and wide. I am considering a 285/75 and a 255/85 toyo MT as replacement and going back down to 33".

Here is a good visual comparison for you to look at........ I am concerned the look of the 255 may be too skinny for the van as it is a big van!!! Pictures don't give it justice until you have it in person.

http://www.expeditionportal.com/forum/s ... hp?t=14555
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Old 06-04-2010, 12:47 PM   #3
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Re: Suggestions for tire size for 17" rim in new 2010 EB 4WD

Also I am concerned the 255 size is too skinny for these vans weight. Meaning the wider the tire the more float it will have in the steering which I prefer after driving mine on the highway for a long period. The van needs to have less responsive steering otherwise it could get scary. The skinnier tires will give it more responsive steering and more road feedback which is bad for these vans in my opinion as it is a 10,000 lbs beast your wanting to keep on the road.... specifically in between lines on the highway.

Alternatively I have seen some on this site add steering stabilizers which would help a lot if you went the skinny route.
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Old 06-04-2010, 12:53 PM   #4
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Re: Suggestions for tire size for 17" rim in new 2010 EB 4WD

Glad you posted this question and the tire article. Very interesting.

I'm considering switching to a 17" rim and am also curious about tire issues. I think the 285s are the most common size for the SMB. I have used 285s on the 'stock' 16" rims for more than 4 years.

In my limited research thus far, I've found that a 17" rim is a bit of an orphan size with relatively few tire choices available.....at least in an E rated tire. Since many of our rigs exceed 10k pounds loaded for a trip, tire load capacity is very important. Also, the 285 size tire seems to have a substantially higher load capacity, with D or E rating, than the 255s or 265s. That is probably why they are popular with SMBs.

For broad use including snow/ice, many prefer an all-terrain tire. They may not be optimal for snow/ice, but an all-terrain tire is a compromise and the nitto terra grapplers seem to be very well regarded. FWIW I'm running Goodyear silent armor AT and have used them in wide variety of conditions. So far, so good.

For a 17" rim, Toyo seems to offer the broadest selection of E rated tires. The Toyo open country ATs are also highly regarded. If I switch to 17" rims, I'll be going with those. In the 265/17 size the Toyo AT E are rated for max load of 3,195lbs. In size 285/17 size Es the load rating is 3,750. To each his/her own, but when it comes to tire load capacity, more is better in my opinion.

Good luck.
Rob
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Old 06-04-2010, 02:09 PM   #5
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Re: Suggestions for tire size for 17" rim in new 2010 EB 4WD

Interesting tire article. A couple of points to consider regarding heavy vans vs. the Landcrusier, Land Rover, Jeep extreme off-road crowd that article was primarily written for.

1. An E-rated tire isn't going to deflect or conform to offroad obstacles near as well as a D-rated tire with softer sidewalls and fewer tread plys. So a lot of the what the article is comparing is kind of moot.

2. I would be afraid that a skinny tire on a heavy SMB or even regular van (mine weighs 4 ton and its just a passenger van) will likely really sink in any kind of soft sand or mud. Think pizza cutters.

3. According to the BFG AT web site a 255/75-17 D-rated tire is 32.1" tall and 10.2" wide. The width difference between a 285/70-17 (11.5"), 305-65-17 (12.2"), and 315-70-17 (11.8") ranges from 1.3" to 2" (or 11 to 16 percent wider). It would be interesting to drive both "skinny" and "wide" tires on our vans and see if you could really tell a difference.

4. Looks. Our van came with the factory 245/75-17 street tires and it looked just silly with fender flares and a 4" lift.

The 17 inch tire size may well be going the way of the Dodo Bird as the standard for most new trucks is 18 or 20 inches.
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Old 06-04-2010, 03:01 PM   #6
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Re: Suggestions for tire size for 17" rim in new 2010 EB 4WD

315's and you'll never look back......
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Old 06-04-2010, 05:08 PM   #7
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Re: Suggestions for tire size for 17" rim in new 2010 EB 4WD

My other thought is tire type. Here is the only E rated snow tire I am able to come across that are 285, and they do go larger.

http://www.1010tires.com/tire.asp?tireb ... &pc=173900

LT285/70R17 121Q 10/E BW $285.99

Other ones I am considering are these...

1. Toyo M55 They come in the smaller 265/70/27...2" smaller height (1" less radius) and thinner by an 1"
2. Toyo Open Country MT (mud terrain)
3. Nokian Vatiiva A/T or M/T. I am unsure the winter nokian tyres are E rated.

I would love insight for a good off road and snow ice tire to consider. I considered a second winter studded tire--the Nokian Hakkapelitta 5 SUV (E rating is unknown for this size). I love them for my 96' 4runner.

http://www.nokiantires.com/tyre?id=1189 ... itta+5+SUV

I welcome thoughts on Tires as well.
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Old 06-04-2010, 06:21 PM   #8
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Re: Suggestions for tire size for 17" rim in new 2010 EB 4WD

What Jeffrey said:

315 X 70 X 17
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Old 06-04-2010, 07:18 PM   #9
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Re: Suggestions for tire size for 17" rim in new 2010 EB 4WD

Point / Counterpoint
Goodyear Wrangler MT/R with Kevlar

285/70/17 have a 33" diameter, and therefore a 16.50" radius
305/17/17 have a 34.1" diameter, and therefore a 17.05" radius
315/70/17 have a 34.7" diameter, and therefore a 17.35" radius

I'm all for large tires if absolute maximum clearance is needed, but going up in size doesn't gain you much clearance, and it's even less if you air down. It does cost you more wear and tear on axles, somewhat reduced mileage, and some small amount of stability.


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Old 06-04-2010, 07:35 PM   #10
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Re: Suggestions for tire size for 17" rim in new 2010 EB 4WD

Quote:
Originally Posted by BroncoHauler
Point / Counterpoint
Goodyear Wrangler MT/R with Kevlar

285/70/17 have a 33" diameter, and therefore a 16.50" radius
305/17/17 have a 34.1" diameter, and therefore a 17.05" radius
315/70/17 have a 34.7" diameter, and therefore a 17.35" radius

I'm all for large tires if absolute maximum clearance is needed, but going up in size doesn't gain you much clearance, and it's even less if you air down. It does cost you more wear and tear on axles, somewhat reduced mileage, and some small amount of stability.


Herb
I just wanted to add that another factor to consider to picking tire sizes is the diff gear ratio related to the tire size you want to have.
What's the diff gear ratio running the 315/70/17?
You just don't want to be geared to tall.

For example, running 285/75/16 with 3.73 Diff gear ratio is at the limit of being to tall, climbing hills might be a prob versus using a diff gear ration of 4.10. 305 or maybe 35in max with a 3.73 would be asking for it on the tranny for climbing extreme hills. I'm still debating if 4.10 is the ideal gear ratio. What's everone diff gear ratio running em huge tires?


Is 315/70/17 the same size as 315/70/16?
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