Anybody convert to 16" Wheels?
#11
04-22-2020, 10:24 PM
I have ran 265/70R18, 285/65R18 275/65R18 and 33x12.50R18
265/70 no rubbing worked fine but hated the tires General Grabber AT2
285/65 minimal rubbing at full lock only, this size was phenomenal in the show covered trails at winter romp
275/65 my favorite all round size for trails and daily drive
33x12.50 great for all the off road parts but definitely notice the big tire around town and the highway
My truck is modified lifted and has an aftermarket bumper
I also think the tire tread pattern will play a huge role in your satisfaction
265/70 no rubbing worked fine but hated the tires General Grabber AT2
285/65 minimal rubbing at full lock only, this size was phenomenal in the show covered trails at winter romp
275/65 my favorite all round size for trails and daily drive
33x12.50 great for all the off road parts but definitely notice the big tire around town and the highway
My truck is modified lifted and has an aftermarket bumper
I also think the tire tread pattern will play a huge role in your satisfaction
#13
04-22-2020, 10:45 PM
Super Moderator
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purseon (04-23-2020)
#14
04-23-2020, 12:33 PM
Camel Trophy
Definitions:
Friction: (Mech.) The resistance which a body meets with from the surface on which it moves. It may be resistance to sliding motion, or to rolling motion. [1913 Webster]
Adhesion: Intermolecular forces that hold matter together, especially touching surfaces of neighboring media such as a liquid in contact with a solid.
Momentary Bonding: The brief molecular connection of two surface elements under heat, pressure or mixing.
Deformation: The change in geometric size, shape, form or position due to force.
Mechanical Keying: The interlocking of surfaces.
A tarmac has a good tactile surface and hence offers good traction due to excellent adhesion and momentary bonding.In this scneario a wider tire would perform superbly.
On the other hand a OTR trail is made of ledges,rocks,ruts,sand and mud which dosent offer a good tactile surface ,hence adhesion and momentary bonding is poor.However on such a surface traction is achieved by Deformation and mechanical keying.
A wide tire distributes the vehicles weight over too large of a surface, preventing deformation from occurring at the same rate as a narrow tire with the same pressure (force).
…but a wider tire in that circumstance doesn’t need to deform as much because it’s already got a greater amount of contact with the surface due to the width.
A narrow tire will hold better than a wide one by keying to the surface aggregate due to the greater vertical force.
…but the author states later (see the diagram) that the vertical force is the SAME in each case; which is true. So this statement is simply false.
A narrow tire also presents less rotating resistance on a soft surface, like shallow mud, snow and sand.
…less rotating resistance because the wider tire presents greater adhesion? If not, then why? Because it’s heavier? That’s not necessarily true. So this is either a counter-point against narrower tires or it’s nonsense.
Additional performance is gained by the assumption that most vehicles can fit a taller tire if it is narrower, which provides greater axle clearance.
….assumption indeed. This is dependent on the vehicle and may not be true at all.
Final arguments are made for the benefits related to reduced rotating mass and unsprung weight.
This is ridiculous. Why is a narrower tire less MASS? Those are two different variables. Author is not isolating “Narrow” versus “wider” in this case.
• Rolling Resistance: A narrow tire presents less rolling resistance on improved surfaces, increasing fuel economy and performance.
….I can buy this. There is more tire surface on the terrain so yeah more rolling resistance; however, the discussion was about off-road performance not fuel economy….and wouldn’t the flip side of this be that there is greater adhesion (for the wider tire) due to more rubber being on the road?
• Frontal Resistance: This is another key benefit of using a narrow tire. When driving through mud, snow and sand a narrow tire presents less surface area to the medium. A narrow tire will cut easier through mud, snow and sand than a wide one (due to resistance). The best example of this is when turning in sand. When the front tires turn, they present a wider surface to the sand. You can feel speed reduce immediately when a turn is initiated because of the resistance.
I agree with this. It is what I alluded to in my initial response.
• Rotating Mass: A narrower tire weighs less than a wider one of the same height. The difference in weight between a 33x10.5 and 33x12.5 is about 8 pounds, coupled with the narrower, lighter wheel, the effect on rotating mass is significant. A lighter tire and wheel is easier to accelerate and stop.
“…of the same height” is the key here. That makes the overall statement true. This is more of an observation against a heavier tire than specifically a wide-versus-narrow argument.
• Size Fitment: All things being equal, a narrower tire is almost always easier to fit with less fender trimming and total suspension lift that a wider tire of the same height. Wider tires affect turning circle, compression travel (which needs to be limited by lowering the bumpstops, etc.).
Speculative and irrelevant to the main argument.
• Weight: Without making this an article about suspension, one of the jobs of a properly engineered suspension is to control the cycling of unsprung weight, which is comprised of the axles (control arms, knuckles, etc. in an IFS), tires and wheels. The lighter those assembly's are, the easier it is for the suspension to control it, improving performance.
“OBJECTION Your Honor!”…again this is a weight argument not a width argument.
• Airing Down: This is another critical concept highlighting the advantage of a narrower tire. Airing down a taller tire will not reduce the GC significantly
As quoted from Sahara Overland, a Route and Planning Guide by Chris Scott (2004, ISBN: 1-873756-76-3):
"...Note that it's the diameter or height of the tyres that makes the difference in sand, and not, as many imagine the width... For the desert, you want tyres with a high aspect ratio of around 80 because this represents a taller sidewall so corresponds to added ground clearance when firm, and a longer contact area when deflated"
This is a comment about the aspect ratio, not the width.
Traction in soft surfaces: It is a common misconception that airing down a tire for off-road traction only makes the tire contact patch wider. That is not the case. In fact, only 20% of the increased contact comes from the width. 80% of the increased contact patch comes from the tread patch becoming longer. A tall, narrow tire allows for a very long contact patch when aired down. That, coupled with the minimal frontal resistance (area), negates much of the downside to narrow tires in flotation situations. The taller tire allows for a long contact patch and still maintains good ground clearance.
How does a narrower tire allow for a longer contact patch when aired down than a wider one? That just makes zero sense to me. If anything they’d be the SAME, and then looking at the contact AREA when aired down, the wider tire will have a greater contact area.
Traction on rocky trails: Another common misconception is that when airing down it is the increased amount of tire on the rock (more contact patch), that allows better traction. It is not the contact patch that creates better traction, but the tires ability to conform to the surface irregularities (deformation and mechanical keying). When an aired down tire comes in contact with a rock on the trail, the tires tread collapses under the vertical and horizontal forces, causing the tire to wrap the rock, as opposed to sitting on top of it. The wrapping effect provides greater shear resistance, and in turn better traction. (Technically: the shear load is distributed over multiple planes, not just a horizontal one).
Okay….but a greater contact patch increases the chances that deformation and keying will occur, especially when aired down.
Tire spring rate: One of the great benefits of airing down a tire is improved smoothness. Less pressure allows the carcass to flex. A taller tire has greater sidewall compression, and in turn a better ride. (expressed as compressive strength=N/mm).
Real world example: When climbing a ledge with a jagged surface, the narrower tire will wrap the protrusions with more contact due to the increased deformation depth. The wider tire will rest on the surface of the protrusions and will have a greater chance of spinning (shearing).
Why is there greater deformation depth? If we are saying that the OD of the tire is the same so the sidewall provides greater deformation I’d agree, BUT, that extra rubber is going to be on the outside, it’s not going to cause the central lugs of the narrow tire to turn soft and ooze into the cracks as the figure shows. Furthermore, the wider tire will already be putting more rubber on the edges so less deformation is needed. The figure below is just plain stupid. I’m no Chemist, only a Physicist….but there is no air in the LUGS of the tire, so the sort of crack-filling shown in the figure is just not going to happen.
[img]file:///C:\Users\ao653a\AppData\Local\Temp\msohtmlclip1\01 \clip_image001.jpg[/img]
Friction: (Mech.) The resistance which a body meets with from the surface on which it moves. It may be resistance to sliding motion, or to rolling motion. [1913 Webster]
Adhesion: Intermolecular forces that hold matter together, especially touching surfaces of neighboring media such as a liquid in contact with a solid.
Momentary Bonding: The brief molecular connection of two surface elements under heat, pressure or mixing.
Deformation: The change in geometric size, shape, form or position due to force.
Mechanical Keying: The interlocking of surfaces.
A tarmac has a good tactile surface and hence offers good traction due to excellent adhesion and momentary bonding.In this scneario a wider tire would perform superbly.
On the other hand a OTR trail is made of ledges,rocks,ruts,sand and mud which dosent offer a good tactile surface ,hence adhesion and momentary bonding is poor.However on such a surface traction is achieved by Deformation and mechanical keying.
A wide tire distributes the vehicles weight over too large of a surface, preventing deformation from occurring at the same rate as a narrow tire with the same pressure (force).
…but a wider tire in that circumstance doesn’t need to deform as much because it’s already got a greater amount of contact with the surface due to the width.
A narrow tire will hold better than a wide one by keying to the surface aggregate due to the greater vertical force.
…but the author states later (see the diagram) that the vertical force is the SAME in each case; which is true. So this statement is simply false.
A narrow tire also presents less rotating resistance on a soft surface, like shallow mud, snow and sand.
…less rotating resistance because the wider tire presents greater adhesion? If not, then why? Because it’s heavier? That’s not necessarily true. So this is either a counter-point against narrower tires or it’s nonsense.
Additional performance is gained by the assumption that most vehicles can fit a taller tire if it is narrower, which provides greater axle clearance.
….assumption indeed. This is dependent on the vehicle and may not be true at all.
Final arguments are made for the benefits related to reduced rotating mass and unsprung weight.
This is ridiculous. Why is a narrower tire less MASS? Those are two different variables. Author is not isolating “Narrow” versus “wider” in this case.
• Rolling Resistance: A narrow tire presents less rolling resistance on improved surfaces, increasing fuel economy and performance.
….I can buy this. There is more tire surface on the terrain so yeah more rolling resistance; however, the discussion was about off-road performance not fuel economy….and wouldn’t the flip side of this be that there is greater adhesion (for the wider tire) due to more rubber being on the road?
• Frontal Resistance: This is another key benefit of using a narrow tire. When driving through mud, snow and sand a narrow tire presents less surface area to the medium. A narrow tire will cut easier through mud, snow and sand than a wide one (due to resistance). The best example of this is when turning in sand. When the front tires turn, they present a wider surface to the sand. You can feel speed reduce immediately when a turn is initiated because of the resistance.
I agree with this. It is what I alluded to in my initial response.
• Rotating Mass: A narrower tire weighs less than a wider one of the same height. The difference in weight between a 33x10.5 and 33x12.5 is about 8 pounds, coupled with the narrower, lighter wheel, the effect on rotating mass is significant. A lighter tire and wheel is easier to accelerate and stop.
“…of the same height” is the key here. That makes the overall statement true. This is more of an observation against a heavier tire than specifically a wide-versus-narrow argument.
• Size Fitment: All things being equal, a narrower tire is almost always easier to fit with less fender trimming and total suspension lift that a wider tire of the same height. Wider tires affect turning circle, compression travel (which needs to be limited by lowering the bumpstops, etc.).
Speculative and irrelevant to the main argument.
• Weight: Without making this an article about suspension, one of the jobs of a properly engineered suspension is to control the cycling of unsprung weight, which is comprised of the axles (control arms, knuckles, etc. in an IFS), tires and wheels. The lighter those assembly's are, the easier it is for the suspension to control it, improving performance.
“OBJECTION Your Honor!”…again this is a weight argument not a width argument.
• Airing Down: This is another critical concept highlighting the advantage of a narrower tire. Airing down a taller tire will not reduce the GC significantly
As quoted from Sahara Overland, a Route and Planning Guide by Chris Scott (2004, ISBN: 1-873756-76-3):
"...Note that it's the diameter or height of the tyres that makes the difference in sand, and not, as many imagine the width... For the desert, you want tyres with a high aspect ratio of around 80 because this represents a taller sidewall so corresponds to added ground clearance when firm, and a longer contact area when deflated"
This is a comment about the aspect ratio, not the width.
Traction in soft surfaces: It is a common misconception that airing down a tire for off-road traction only makes the tire contact patch wider. That is not the case. In fact, only 20% of the increased contact comes from the width. 80% of the increased contact patch comes from the tread patch becoming longer. A tall, narrow tire allows for a very long contact patch when aired down. That, coupled with the minimal frontal resistance (area), negates much of the downside to narrow tires in flotation situations. The taller tire allows for a long contact patch and still maintains good ground clearance.
How does a narrower tire allow for a longer contact patch when aired down than a wider one? That just makes zero sense to me. If anything they’d be the SAME, and then looking at the contact AREA when aired down, the wider tire will have a greater contact area.
Traction on rocky trails: Another common misconception is that when airing down it is the increased amount of tire on the rock (more contact patch), that allows better traction. It is not the contact patch that creates better traction, but the tires ability to conform to the surface irregularities (deformation and mechanical keying). When an aired down tire comes in contact with a rock on the trail, the tires tread collapses under the vertical and horizontal forces, causing the tire to wrap the rock, as opposed to sitting on top of it. The wrapping effect provides greater shear resistance, and in turn better traction. (Technically: the shear load is distributed over multiple planes, not just a horizontal one).
Okay….but a greater contact patch increases the chances that deformation and keying will occur, especially when aired down.
Tire spring rate: One of the great benefits of airing down a tire is improved smoothness. Less pressure allows the carcass to flex. A taller tire has greater sidewall compression, and in turn a better ride. (expressed as compressive strength=N/mm).
Real world example: When climbing a ledge with a jagged surface, the narrower tire will wrap the protrusions with more contact due to the increased deformation depth. The wider tire will rest on the surface of the protrusions and will have a greater chance of spinning (shearing).
Why is there greater deformation depth? If we are saying that the OD of the tire is the same so the sidewall provides greater deformation I’d agree, BUT, that extra rubber is going to be on the outside, it’s not going to cause the central lugs of the narrow tire to turn soft and ooze into the cracks as the figure shows. Furthermore, the wider tire will already be putting more rubber on the edges so less deformation is needed. The figure below is just plain stupid. I’m no Chemist, only a Physicist….but there is no air in the LUGS of the tire, so the sort of crack-filling shown in the figure is just not going to happen.
[img]file:///C:\Users\ao653a\AppData\Local\Temp\msohtmlclip1\01 \clip_image001.jpg[/img]
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purseon (04-23-2020)
#15
04-23-2020, 10:22 PM
Thanks for taking the extra time to comment on that article. I agree with the point that some of this will be very vehicle dependent. And also very situational. There is no one tyre that can be best in all categories, even off-road, because there are so many variables. Deep mud, shallow mud, dry, rocky, boulders, slick, and then add in vehicle-specific parameters like weight, clearance, traction control, etc.
I'm pretty happy with my 265/65's Nittos right now, albeit my offroad experience has been limited. Only once last year did I have issues, going up a steep incline with a lot of loose rock, and I probably could have tried airing down to see if that helped, but I didn't have a compressor with me. I guess I'll see where my current tyres take me (literally) and keep some notes on where they don't work so well, so I can try something else if it makes sense next time.
Just for fun, here a few more links I found on tyres, narrow vs. wide:
https://www.physlink.com/education/askexperts/ae200.cfm
https://www.fourwheeler.com/features/1811-skinny-vs-wide-tires-versus/
https://www.fourwheeler.com/features/1811-skinny-vs-wide-tires-versus/
https://justruns.com/test/2017/10/13...vs-wide-tires/
https://expeditionportal.com/forum/t...erience.52523/
Seems like a much debated topic. From a purely aesthetic viewpoint, I have to say I like the look of tall skinny tyres over wider ones. Kind of like the old Land Rovers used in Mutual of Omaha's Wild Kingdom episodes (for those of you a bit older like myself).
I'm pretty happy with my 265/65's Nittos right now, albeit my offroad experience has been limited. Only once last year did I have issues, going up a steep incline with a lot of loose rock, and I probably could have tried airing down to see if that helped, but I didn't have a compressor with me. I guess I'll see where my current tyres take me (literally) and keep some notes on where they don't work so well, so I can try something else if it makes sense next time.
Just for fun, here a few more links I found on tyres, narrow vs. wide:
https://www.physlink.com/education/askexperts/ae200.cfm
https://www.fourwheeler.com/features/1811-skinny-vs-wide-tires-versus/
https://www.fourwheeler.com/features/1811-skinny-vs-wide-tires-versus/
https://justruns.com/test/2017/10/13...vs-wide-tires/
https://expeditionportal.com/forum/t...erience.52523/
Seems like a much debated topic. From a purely aesthetic viewpoint, I have to say I like the look of tall skinny tyres over wider ones. Kind of like the old Land Rovers used in Mutual of Omaha's Wild Kingdom episodes (for those of you a bit older like myself).
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houm_wa (04-23-2020)
#16
04-23-2020, 11:44 PM
Camel Trophy
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loanrangie (04-26-2020)
#17
04-24-2020, 07:16 AM
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