Bigger Badder Tires with Minimal Performance Loss

[goodtimes13]

Hello, this is my first post after joining not to long ago. Love the community. Lots of friendly people with exciting and inspiring stories and advice. This site has already been added to my daily routine. I'm beginning to really appreciate my vehicle and I'm starting to put some love into it. I have a tire question. I have a 99' Rodeo LS 3.2 4x4 and am looking to upgrade my tires so I can take longer trips with more confidence. My tires are on their last breath. I was curious if anyone could shed some light on the whole loss of power thing that goes along with taller tires.

Stock tires: 235/75R15
Sidewall Height: 6.94
Section Width: 9.25
Overall Diameter: 28.88
Circumference: 90.72
Revs per mile: 698.39

New tire Choice A: 235/85R16
Sidewall Height: 7.86
Section Width: 9.25
Overall Diameter: 31.73
Circumference: 99.68
Revs per mile: 635.65

New tire Choice B: 245/75R16
Sidewall Height: 7.23
Section Width: 9.65
Overall Diameter: 30.47
Circumference: 95.72
Revs per mile: 661.93

I guess the question is should I get 235/85 or 245/75? I would prefer to get the the taller ones and fill my wheel well out a little more. How significant will the power loss be for either of them? Can I get away with the 235/85? Or should I play it safe? I have no immediate plans of gear swap but it's on the list (really long list). This is what I found for info on my current (stock) gears "Final Drive Axle Ratio 1)4.30" if that helps. I'm pretty sure I will be getting the Goodyear Wrangler DuraTracs. It looks like I will be stuck with class E with 235/85 but I have the choice between class C or E with 245/75. Any positive of negative experiences with these tires? Thank you all in advance for any and all feedback or banter. It is much appreciated!

A picture of Cliff


THANKS
-Kyle

 

[drifter_r6]

Don't be too concerned with the diameter differences of the tires you listed, the performance loss is negligible (Stock 29" vs 32").

The major power loss will be the weight at the hubs. 1) you are going to a larger wheel size (16") and 2) the larger size/higher load rating. The E rated tires are 10ply, some wheel/tire combos weigh close to 80-100lb each.

Whats the GVWR of the vehicle loaded with gear? All you need is a tire that can handle that amount of weight. Do you have the torque to turn the extra weight (ie. power loss)? Your mpg will suffer to. Yes, there is the added benefit of side wall protection. I assume this is a daily driver. Do you really plan on driving through that rough of terrain very often?

Not trying to discourage you. There is practical and there is going overboard. Then again if we didn't like going overboard we wouldn't be on this forum.

 

[mvbeggs]

Hello, this is my first post after joining not to long ago. Love the community. Lots of friendly people with exciting and inspiring stories and advice. This site has already been added to my daily routine. I'm beginning to really appreciate my vehicle and I'm starting to put some love into it. I have a tire question. I have a 99' Rodeo LS 3.2 4x4 and am looking to upgrade my tires so I can take longer trips with more confidence. My tires are on their last breath. I was curious if anyone could shed some light on the whole loss of power thing that goes along with taller tires.....

Take a look at a power curve for your engine. A larger diameter tire, in effect, gears your vehicle higher. (i.e. if you were running 2500rpm @60mph before the tire swap, and you change to a tire that is 10% larger, your new rpm's at 60mph will be 10% lower, or ~2250) You want the vehicle's engine to stay in its power range at your cruise speed. If you get out of the engine's power band, you'll see a lot of downshifting on hills, or if you go too large, not able to shift into overdrive at all.

You also need to be concerned with correcting speedometer and odometer for the new tire size. In some vehicles a change in tires make the shift points get real weird, if you don't let the car's computer know you're running different tires.

Tire weight will also play a roll in your gas mileage and power needed to get things rolling.

 

[HenryJ]

Is there a reason you are moving to 16" wheels?

I would suggest that a 30x9.50-15 tire might be a good choice. It is a couple steps up from the stock size and will have less interference issues. Much less expensive. Those would be the best choice given the parameters of your post: "Bigger badder tire with minimal performance loss." Check out the BFG TAKO $155 ea. or for a more aggressive tire the Dunlop mud Rover $149 ea.

If a wider tire is what you seek, the 31x10.5-15 has lots to choose from. It too would offer more clearance than the 16" tire choices you have listed.

It you are set on a 16" tire and have room, the 235/85-16 is a good tire. I prefer it to the 245/75-16.

 

[goodtimes13]

Whats the GVWR of the vehicle loaded with gear? All you need is a tire that can handle that amount of weight. Do you have the torque to turn the extra weight (ie. power loss)? Your mpg will suffer to. Yes, there is the added benefit of side wall protection. I assume this is a daily driver. Do you really plan on driving through that rough of terrain very often?

Not trying to discourage you. There is practical and there is going overboard. Then again if we didn't like going overboard we wouldn't be on this forum.

Class E (~12,000) tires aren't necessary for the weight of my vehicle, Class C (~8,000lbs) is much closer. I prefer the 235/85 but if the load rating being overkill is an issue then 245/75 it is. 205 HP and 214 lb torque. I'm okay with mpg loss. This is my daily driver and it sees pavement probably 10-15 times more than it sees dirt. I definitely don't play as hard or go as far as you fine gentleman do but I hope to get there some day.

Take a look at a power curve for your engine. A larger diameter tire, in effect, gears your vehicle higher. (i.e. if you were running 2500rpm @60mph before the tire swap, and you change to a tire that is 10% larger, your new rpm's at 60mph will be 10% lower, or ~2250) You want the vehicle's engine to stay in its power range at your cruise speed. If you get out of the engine's power band, you'll see a lot of downshifting on hills, or if you go too large, not able to shift into overdrive at all.

I'll take him out for a spin on the freeway in a bit! Thanks!

Is there a reason you are moving to 16" wheels?

I want something with a longer contact patch and to get anything over 30" while still staying skinny I found the only option was to move to 16". I plan to test fit both sizes soon to be sure I have the room, but I don't think they will have any trouble.

 

[HenryJ]

I want something with a longer contact patch and to get anything over 30" while still staying skinny I found the only option was to move to 16". I plan to test fit both sizes soon to be sure I have the room, but I don't think they will have any trouble.

I really loved my 33x9.50-15 tires Trierack shows them for $179ea but back ordered. Interco shows a 32x9.5-15

I do know the 33x10.5 are available BFG TAKO and a little cheaper to buy

I like more sidewall and the ability to air down for traction. Aired down a little they float over the terrain. Those 10 ply tires are not going to flex on a light rig. They will be a rough ride for sure , as well as packing around lots more unsprung weight.

 

[goodtimes13]

I really loved my 33x9.50-15 tires Trierack shows them for $179ea but back ordered. Interco shows a 32x9.5-15

I do know the 33x10.5 are available BFG TAKO and a little cheaper to buy

I like more sidewall and the ability to air down for traction. Aired down a little they float over the terrain. Those 10 ply tires are not going to flex on a light rig. They will be a rough ride for sure , as well as packing around lots more unsprung weight.

I would love to be able to keep my current wheels and save $500! 31" or 32" with 9.5 width would be ideal. I don't think I can run 33s especially not 10.50s.

 

[chasespeed]

Yes you can run 33x10s. Had that size swamper on a previous Rodeo.

Running a 265/16 C Duratracs now. This one is a stick, so, I dont really notice. I noticed the weight on those TSLs though.

With 4.30 gears you have a manual trans. I also run a set of 235/85/16s, but, those were load range E... stiff and heavy.

Thats my current toy... bad picture though..

Chase

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[goodtimes13]

Yes you can run 33x10s. Had that size swamper on a previous Rodeo.

Running a 265/16 C Duratracs now. This one is a stick, so, I dont really notice. I noticed the weight on those TSLs though.

With 4.30 gears you have a manual trans. I also run a set of 235/85/16s, but, those were load range E... stiff and heavy.

Thats my current toy... bad picture though..

Chase

Oh mine is an auto so what does that make my gears? I do have a 3" suspension lift but I was under the impression that I would still have to do some trimming for 33s. I definitely don't want to do that if that is the case. Are there no 31" or 32" class C skinnys that I can run?

Rodeo looks great!

 

[rxinhed]

For a daily driver with occasional offroad use, I have had extremely good luck with my 31x10.5 BFG all terrains. On a light Isuzu, I don't understand why you'd prefer the 10-ply LT tires...really stiff ride. Second, I am confused about your statement that rim diameter size contact patch size. For a given diameter, I think that the rim width is your bet on increasing the contact size. Also, a larger diameter rim will decrease the tire sidewall height and reduce sidewall flexibility. While this improves steering performance when aired up, it doesn't allow the tire as much flex when aired down. Third, why go skinny?

Anyway, check out these:
32x9.5 Swampers
http://www.intercotire.com/tires.php?id=10&g=1

31x9.5 TSL Radial
http://www.intercotire.com/tires.php?id=14&g=1

LT215/85-16 Goodyear DuraTrac
http://www.goodyear.com/en-US/tires/wrangler-duratrac?pc=31200702700000#

 

[chasespeed]

Yes, you'd need some MINOR trimming. If you looked at mime, I'd have to point it out.



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[goodtimes13]

For a daily driver with occasional offroad use, I have had extremely good luck with my 31x10.5 BFG all terrains. On a light Isuzu, I don't understand why you'd prefer the 10-ply LT tires...really stiff ride. Second, I am confused about your statement that rim diameter size contact patch size. For a given diameter, I think that the rim width is your bet on increasing the contact size. Also, a larger diameter rim will decrease the tire sidewall height and reduce sidewall flexibility. While this improves steering performance when aired up, it doesn't allow the tire as much flex when aired down. Third, why go skinny?

Anyway, check out these:
32x9.5 Swampers
http://www.intercotire.com/tires.php?id=10&g=1

31x9.5 TSL Radial
http://www.intercotire.com/tires.php?id=14&g=1

LT215/85-16 Goodyear DuraTrac
http://www.goodyear.com/en-US/tires/wrangler-duratrac?pc=31200702700000#

I prefer the size of the 235/85 and wish they were offered in class C. I want a larger contact patch when aired down and off-roading. To achieve that I need a larger diameter tire. But from what I've found, I need to move up to a 16" rim to have a 31"-32" diameter while still remaining skinny(~9.5"). My ideal tire would be a 235/85 class C T/A KO or DuraTrac, but unfortunately that won't happen. I've always preferred skinny tires for lighter vehicles. They seem to slip less. Also I don't have the largest wheel wells and skinny only helps for clearance. Oh and I am a broke college student with ridiculous tuition and every penny counts.

 

[rxinhed]

I've always preferred skinny tires for lighter vehicles. They seem to slip less.

The appearance of less slip has to do with contact pressure. A narrower tire has a higher contact pressure than a wide tire. In dune sand this would work against you. I presented links to two 15" tires with a narrow section. You could also hunt down some mil-spec tires such as a 6.5-15, 7.00-16, etc. and still be within your 'preferred' range.

Military Tires:
http://militarytires.com/

Universal Military Tires:
https://www.universaltire.com/truck-and-military/military.html?p=1

Oh, and I am a broke college student with ridiculous tuition and every penny counts.

While I was studying, I had a 4x4 LUV. Max tire diameter was about 27 inches, so I can relate. However, while you're matriculating, you could practice the KISS principle and wheel with what you have until after graduation, loans are paid off, and you're earning the big bucks.

A thought.

 

[chasespeed]

Btw, sorry... if you have an auto, it should be 4.10s.

FYI, only need to trim the from fender.

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[goodtimes13]

The appearance of less slip has to do with contact pressure. A narrower tire has a higher contact pressure than a wide tire. In dune sand this would work against you. I presented links to two 15" tires with a narrow section. You could also hunt down some mil-spec tires such as a 6.5-15, 7.00-16, etc. and still be within your 'preferred' range.

Military Tires:
http://militarytires.com/

Universal Military Tires:
https://www.universaltire.com/truck-and-military/military.html?p=1



While I was studying, I had a 4x4 LUV. Max tire diameter was about 27 inches, so I can relate. However, while you're matriculating, you could practice the KISS principle and wheel with what you have until after graduation, loans are paid off, and you're earning the big bucks.

A thought.

Haha thank you for the wise and helpful words!