Tires: Wide or Narrow?

[Pskhaat]

...they asked me this question. Why does the American market want wide tires and huge rims when they don't work in any off-road testing model we have tried...

Scott, I pray you told them there are a few of us who want the 85 series + aspect ratios back, and that I expect my 275/85r16 to be ready to ship LTL to my door At least Michelin asked this. From what I've lately seen, I'm quite certain there's no one at most major players any longer that has the time to consider questions of that nature.

 

[Redline]

No worries, I was not offended.

Today I was doing some errands and stopped by my favorite tire shop, Les Schwab Tires, to get their latest newspaper advertisement and do some window shopping. I (again) looked at some 235/85s and compared them visually to 265/75s.

When I can come up with some cash I may buy a set of 4 E-range 235/85s and try them on the Mall Crawler 4Runner. I need to decide if I want to buy a set of mellow all-terrain/all-seasons, or a more 'aggressive all-terrain'/medium-duty traction tire in this size. I know I don't need full-muds as I have enough of those right now. My back-up plan is that if I don't care for the 235s on my 4Runner then they will become the everyday/street tires on my F350.

The 265 and 235 part of the size designation is actually the "Section Width" in millimeters and not the tread width you are measuring. 265mm / 25.4 = 10.43"

Also note changing rim width will also effect the tire's section width measurement.

 

[J_L]

I'm definitely no tire expert, my head is spinning after reading this thread. I just went thru this decision on which BFG's to get, 285/75/16 AT or 255/85/16 MT. The narrower tire was appealing for less friction but I really didn't want the MT for road use; most approaches to trails are fairly long highway drives for me. Ended up getting the AT's which are about 1.25 inches wider, I had convinced myself that the difference was minimal. Is it really that significant for friction, ect?

 

[7wt]

I never considered the 235/85's before. I have been looking into a new set of 265/75's for the end of the summer but I am now seriously considering the 235/85's. Question is, would the 235's give the same benifits as the 255/85's without the regearing? Would they be "better" than the 265/75's for fuel economy and mild desert driving?

 

[Redline]

I think you made the right decision. I like having an aggressive tire for off-highway, but I used to buy "aggressive all-terrains" (or wimpy mud tires) until I started using two set of tires for my 4x4s.

I recently purchased a set of BFG 255/85R16D M/Ts for my F350. I like them, but they don't appear to be as true (as round) as my recent Toyos and need more weight to balance. They are a little louder than the Toyo M/Ts but much quieter than the Michelin XZLs Scott wants to try (I had a set on my F350 briefly several years ago . With lots of highway miles to cover to get to trails, and possibly for daily-driving, a good A/T is hard to beat for everything except serious slop.

I'm definitely no tire expert, my head is spinning after reading this thread. I just went thru this decision on which BFG's to get, 285/75/16 AT or 255/85/16 MT. The narrower tire was appealing for less friction but I really didn't want the MT for road use; most approaches to trails are fairly long highway drives for me. Ended up getting the AT's which are about 1.25 inches wider, I had convinced myself that the difference was minimal. Is it really that significant for friction, ect?

 

[Redline]

I'm sure others can/will answer, possibly with valuable & contradictory opinions...

I think all three sizes are good choices, but it might be easier to make a better choice if choosing 265s compared to 255s or 235s. It really depends on the vehicle. I don't see one listed in your signature, and the answers will always 'depend' on lots of other things. You, vehicle, conditions...

265/75 & 235/85R16 have the benefit of both being about 32-in. tall. If that is your maximum before re-gearing then that is a major factor. Almost all 255/85 are load-range-D. Almost all 235/85s are E-range. 265/75 can usually be found in C,D, or E-load-range, often in the same tire/tread design.

Depending on the vehicle, 235s could be great "IF" you find the right tire/tread for your platform. Although I love the size, there are less choices in 255/85R16. They should all handle "mild desert driving" well, and narrower/lighter should be better for MPG.

I never considered the 235/85's before. I have been looking into a new set of 265/75's for the end of the summer but I am now seriously considering the 235/85's. Question is, would the 235's give the same benifits as the 255/85's without the regearing? Would they be "better" than the 265/75's for fuel economy and mild desert driving?

 

[7wt]

Redline, I have had really good luck with my Revo's for the driving I do. They have done everything I have asked and then some. I screwed up when I bought them though, I got P metrics. Next set will be LT for sure. I don't carry a whole lot of weight as most of my trips are only two or three day at most and all of mt gear is light weight backpacking stuff. I am not sure I need an E rated tire. You are correct, the Revos are E rated in that size and the 265/75's come in both C or E ratings. I have always had P metrics so I don't fully understand the load ratings....C, D or E. Could anyone explain?

 

[Redline]

I'm not suggesting you need a Load-Range-E tire. My observation that some of these tires are available in C through E load range is that I/you may prefer a softer ride much of the time. A load-range-C is still an "LT" tire but softer riding than a D or E. The compromise is that in general the C-range tire will not be as tough/rugged as a D or E. You pay for that strength with a firmer/stiffer ride.

The load ranges are just exactly that; how much weight the tires are designed to carry at a certain PSI. It will vary with the tire size (an E-range 285/75 can carry more weight) but here is an example:

In the LT265/75R16 size, maximum load in a single rear wheel application (not a dully pickup):

C-Range: 2,470-lbs @ 50-psi (cold)
D-Range: 3,000-lbs @ 65-psi
E-Range: 3,415-lbs @ 80-psi

In addition, you will also hear of the load ranges referred to as: 6-ply for C, 8-ply for D, and 10-ply for E. But manufacturers use the plies they need to make their tires withstand their designed parameters, and they don't necessarily have that many plies to make the rating these days.

An 8-ply rating (or 8 P.R.) is synonymous with 'Load-Range-D'. One example are some used LT255/85R16D tires I have in my shop. They have 4 tread plies + 2 sidewall plies, only 6 total plies, but have an 8-ply-rating/Load Range D.

Redline, I have had really good luck with my Revo's for the driving I do. They have done everything I have asked and then some. I screwed up when I bought them though, I got P metrics. Next set will be LT for sure. I don't carry a whole lot of weight as most of my trips are only two or three day at most and all of mt gear is light weight backpacking stuff. I am not sure I need an E rated tire. You are correct, the Revos are E rated in that size and the 265/75's come in both C or E ratings. I have always had P metrics so I don't fully understand the load ratings....C, D or E. Could anyone explain?

 

[7wt]

Thanks for the feedback. I still may go the 235 route because of the skinny factor and the E ratings are tougher.

 

[devinsixtyseven]

Cut 'em up?

Just thought I'd throw this out there...

I've noticed (as I expected, actually) after running 265/70/16, 265/75/16, 285/75/16 and 315/75/16 that the wider I have to go (for the height I want), the more the truck floats when I don't want it to...for example puddles on the road at speed.

The only reason I end up wide is because there are plenty of choices in the 33" size for both wide and narrow tires, but few in 35...I don't want to be reworking the tread pattern on pizza-cutter boggers just so I can have a certain tread width at the height I want.

It doesn't get halfway decent again until you get to 37" tires...then you're back to tall ratios, but they're still as wide as the 35" tires.

I seems to me that of two completely smooth tires, one narrow and one wide, the wide tire would be a worse performer in any situation where the tire were pushing something out of the way--water, slush, sand, mud--but better at high speed in corners, side loading, etc...

So to get the best of both worlds, why not a reasonably wide tire (not even talking about height, now, just width) with the same contact surface as a narrow tire? Think of those two tires again, one wide and one narrow, both same diameter, both perfectly smooth...now cut a couple grooves around the circumference of the wide tire, so it presents the same contact surface as the narrow tire.

Am I nuts?

-Sean

 

[Scott Brady]

Sean, you are correct for rock situations. Hence the Irok works so well with a nearly 40% void ratio. Unfortunately, you will still need lots of HP to push the big tires through sand and mud as the frontal resistance cannot be eliminated (wind resistance on the road too)

 

[slooowr6]

I'm not suggesting you need a Load-Range-E tire. My observation that some of these tires are available in C through E load range is that I/you may prefer a softer ride much of the time. A load-range-C is still an "LT" tire but softer riding than a D or E. The compromise is that in general the C-range tire will not be as tough/rugged as a D or E. You pay for that strength with a firmer/stiffer ride.

The load ranges are just exactly that; how much weight the tires are designed to carry at a certain PSI. It will vary with the tire size (an E-range 285/75 can carry more weight) but here is an example:

In the LT265/75R16 size, maximum load in a single rear wheel application (not a dully pickup):

C-Range: 2,470-lbs @ 50-psi (cold)
D-Range: 3,000-lbs @ 65-psi
E-Range: 3,415-lbs @ 80-psi

In addition, you will also hear of the load ranges referred to as: 6-ply for C, 8-ply for D, and 10-ply for E. But manufacturers use the plies they need to make their tires withstand their designed parameters, and they don't necessarily have that many plies to make the rating these days.

An 8-ply rating (or 8 P.R.) is synonymous with 'Load-Range-D'. One example are some used LT255/85R16D tires I have in my shop. They have 4 tread plies + 2 sidewall plies, only 6 total plies, but have an 8-ply-rating/Load Range D.

Great info, one more thing to add from what I learn when I own a 86 VW Vanagon Camper. Load range is more specific on the strength of the side wall like Redline said. VW is a tall and heavy van with narrow track width, 4400lbs with a wheel base not much longer than a Miata. The P rating tire with proper load-index (vertical load) rides smoothly until I get hit by cross wind it sway so bad I felt the van is going to change lane by itself. After replace with a set of C load-rage LT tire the sway from cross wind is much much less. I'm not sure how much this affect the newer trucks but I'm going to replace my tire on my 06 Tacoma with E load range tire when time comes. My GVW is around 6000lbs I think. :Wow1: I'm also thinking getting 235/85/16 after reading the whole thread. :elkgrin:

 

[highlux]

I joined the tall/narrow club about 4 months ago...got a wicked deal on a set of 9.00R16 Michelin XLs. Holy crap what a tire! So far no real offroad use, but I can feel the traction difference on ice between these and my old 35x12.50s...same heavy truck, but more pressure (more friciton) on the road because of smaller contact patch. Gotta say these are heavy suckers, but once yer rollin' it's a breeze. Stopping is a whole nuther story. I can kinda notice less wind and road resistance (I can coast longer and faster). They also fit surprising well on my truck... they are about 35-36" actual height and my truck (89 hilux) has about 2.5-3" lift. They do rub the leafs while turning sharp, but will fix that when I can get some more negative offset ALUMINUM (lighter) rims. Despite being really hefty, they ride straight as a arrow even though they are not balanced right now. Must be due to high quality construction, which gives them steel belted 5/8" thick sidewalls (I think), and about an inch thick rubber providing the tread (forget the spare, don't need em'!). Actually I have a fifth one in the garage, just no where to keep it right now. One thing I don't really care for is the directional tread pattern...makes it hard to rotate yer tires effectively without remounting 'em.

 

[devinsixtyseven]

Wherever do you find 9.00R16 XLs, anyway?

I was thinking about the tall/narrow thing yesterday...it occurred to me nobody would run "bicycle" tires because it just doesn't make sense, any more than a guy would run 29x20 tires (without a custom airbrush job and a lowering kit ).

The reason that ratio is so important is tread stability...running narrow means less resistance to the front like Scott mentioned, and for a given weight I assume you can reliably run up to a certian width--really heavy rigs have no trouble with a 12.5" section width, but a 2T rig does...so we minimize the width as much as possible.

BUT we want a large contact patch and plenty of room between the dirt and the rim, and it's easier on components to go tall and air down--less inertia from a narrow tire, and easier to fit. This brings on another problem, folding the tire over on itself at low pressure and side loading (corner, sidehill, both at once, etc)--think of a bicycle tire but with a really big sidewall, as if an aero roadie wheel were all inflated rubber around a tiny hub--so as we get taller, the width must increase to keep the tire from folding. For all the semi-humorous references to bicycle tires, they are an extremely low-profile tire compared to what we're running.

I'd hypothesize that's why we see 75%-90% ratios on "performance" offroad tires, vs 50%-75% on "fashion" tires. That IROK I'm drooling over is about 83%, Michelins are even higher ratios...tall tires, with just enough section width to keep the tire stable at lower pressure. Unless they're floatation tires (tall AND wide), they bias toward height rather than width, width is only a necessity for stability.

I guess that means get the tallest tire you can find, and get a width that's stable at low pressure...and I bet you find something in the 85% range.

Does that sound right?

I'm not really sure where Pit Bull tires fall in this hypothesis. They look like flotation tires, and I'm sure they're stable at low pressure, but personally I wouldn't use them for mixed driving or "overland" stuff.

-Sean

Aha: the link I was thinking of...
http://www.garbee.net/~cabell/photos5.htm
that's not the only link, i'll see about the others...

 

[Redline]

Very true, I have found the same thing with my limited experience with tires 235, 245, 255, 265, & 285mm wide. Wider tires do provide unwanted 'flotation' on-highway sometimes. Many times on-road with wider tires I have experienced 'float' and/or hydroplaning that might not have occurred with a narrower tire. Related to this float, is the tires void or lack thereof. A wider tire with more void may be able to dissipate water, snow, slush and avoid hydroplaning better than a narrower tire with a low void ratio, to a point.

I also like how a narrower tire doesn't catch edges as easily and handles the ruts in the pavement better caused by semi-trucks on heavily traveled/worn roadways.

When I had my Jeep (and for my futures Jeeps I had similar thoughts and concerns about 33s vs. 35s. Like you point out, there are a few good choices in the narrow 33 & 32-in range but above 33-in you need to go with wider tires, Michelin military 9.00R16 and the like being the exception. I don't plan to run 37s anytime soon...

With your smooth tire with grooves idea I think you are touching on some of the points addressed in Mr. Brady's "narrow tire white paper" I'm not so sure that if you cut those groove in the wider tire face that you will eliminate the rest of the 'smooth' tires contact and its other 'wide' negative affects?

redLine/James

Just thought I'd throw this out there...

I've noticed (as I expected, actually) after running 265/70/16, 265/75/16, 285/75/16 and 315/75/16 that the wider I have to go (for the height I want), the more the truck floats when I don't want it to...for example puddles on the road at speed.

The only reason I end up wide is because there are plenty of choices in the 33" size for both wide and narrow tires, but few in 35...I don't want to be reworking the tread pattern on pizza-cutter boggers just so I can have a certain tread width at the height I want.

It doesn't get halfway decent again until you get to 37" tires...then you're back to tall ratios, but they're still as wide as the 35" tires.

I seems to me that of two completely smooth tires, one narrow and one wide, the wide tire would be a worse performer in any situation where the tire were pushing something out of the way--water, slush, sand, mud--but better at high speed in corners, side loading, etc...

So to get the best of both worlds, why not a reasonably wide tire (not even talking about height, now, just width) with the same contact surface as a narrow tire? Think of those two tires again, one wide and one narrow, both same diameter, both perfectly smooth...now cut a couple grooves around the circumference of the wide tire, so it presents the same contact surface as the narrow tire.

Am I nuts?

-Sean