Topic: Tire size arguments

[bootguy]

94 YJ 2.5L, Automatic, 2.5" lift, 4:88 gears.  I currently have 31" tires on stock rims but it is getting time to replace the tires.  I have been shopping around for new tires and have found  mostly all 31" tires.  If wanting to go up to a 32" or 33" it would be special order and would need to replace the rims.  Price difference is only about $20 to $40 between the tires unless I went with a high end specialty tire.  So the dilemma is, as a daily driver stay with 31's as they are very common and usually able to replace the same day or special order new size?  Pros and Cons is what I am looking for.

P.S. - does the weight of the steel rims VS aluminum really make that much difference?

[Jeffy]

For a daily driver, I'd stick with 31's.  Just so you know, you can fit 31's onto a 15x6" stock wheel.  Though 15x7's are better.  The difference in weight between aluminum and steel does come into play although not that much since you're still dealing with stock size wheels.  Also note that cast aluminum is going to be heavier then forged or billet.

I personally wouldn't recommend 32's jsut because they are an odd size.  Also, you could save up to 5lbs with going with a 33x10.5 as opposed to a 12.5" if you go with BFG's.  There's also a 33x9.5" BFG makes as well which should be even lighter.  If you do go with 32's or 33's, I'd recommend going with a 15x7 stock wheel if you want to stay cheap or go no larger then 15x8.

Also pay attention to the backspacing/offset.  The stock 15x7 is 5.5" IIRC.  I wouldn't go no less then 4.5" BS and more like 4.75" if you want your wheels to stay tucked under the stock flares.  Though you will have to adjust your turn stops if you do.  If you went with the more common 3.75" BS your tires are going to stick out past the stock flares.  Some people like the roller skate look while others don't.  I'm not really a fan when they're under 35 tires.

[jfrabat]

I'd say go with 33's X 10.5 tires.  BFG are really good, by the way...  I have been running them (33 X 12.5) for years now.  Handle well in the city, and are pretty good in the muck (they are not super swampers, but they are no slouch either).

[sharpxmen]

you lose quite a bit of mpg going to bigger tires, but then again is not that great to begin with so depends on what you're looking for (looks much better on 35s :)

[jfrabat]

you lose quite a bit of mpg going to bigger tires

If that's your worry, get a Prius!   

[dwtaylorpdx]

BFG has a almost 33x9.50 AT.. (Its really about 32.5) but I find with my 4 banger too wide just kills freeway speed and mileage.

Cheers

[Jeffy]

BFG has a almost 33x9.50 AT.. (Its really about 32.5) but I find with my 4 banger too wide just kills freeway speed and mileage.

Cheers

For most tires you'll find the AT's are typically .5" shorter when advertised and MT's to be around .2-.3" IIRC.  The only time you'll see as them as advertised or taller is with bias ply tires like Interco.

[dwtaylorpdx]

:) What marketing people lie?? Perrish thet thought ! Bwahahah..

Yea the 9.50 BFG on 15's is a really nice all purpose tire, Not gonna win the hammers with it but for your daily search and destroy missions on the commute an dally around driving its a great tire.. And it fills the wheel wells out nicely so it doesn't look weird with a lifted jeep.

I tried a set of Toyo mud terrains on my YJ same size but at 20K miles they are wearing pretty fast, probably go back to the BFG's when these wear out..

[Jeffy]

:) What marketing people lie?? Perrish thet thought ! Bwahahah..

Yea the 9.50 BFG on 15's is a really nice all purpose tire, Not gonna win the hammers with it but for your daily search and destroy missions on the commute an dally around driving its a great tire.. And it fills the wheel wells out nicely so it doesn't look weird with a lifted jeep.

I tried a set of Toyo mud terrains on my YJ same size but at 20K miles they are wearing pretty fast, probably go back to the BFG's when these wear out..

I wouldn't go that far.  It's like when you buy a TV.  It's never actual length but rather the diagonal.  A good consumer knows and the mfg. will give a more acurate height in the specs. anyway.  The other problem with tire height has to do with the wheel width.  Narrower wheels will pinch the sidewalls and make the tire taller then a wider wheel.

[Wrench]

My opinions based on several years of noting fuel mileage and tire size differences and running a "few miles" offroad:

-wheel material doesnt seem to make any noticeable difference in weight or fuel mileage.  The design has far more effect on this.  Bling-bling thick aluminum chromed dubs are lead weights compared to a good set of inexpensive common steel wheels.
-wheel DIAMETER can have a very dramatic difference.  Larger wheels are heavier and the weight is carried further from the axle centerline.  This will hurt your fuel mileage.  Switching from 15" to 20" wheels can drop mileage by over 20 percent, even if overall tire diameter remains the same.
-MT's vs AT's:  MT's are most often heavier than AT's due to the deeper tread.  Once again, more weight further from the axle centerline will hurt mileage.  For a DD, AT's will do much better for you.  
-hate to disagree, but there is no way wheel width will ever pinch a sidewall and increase tire diameter.  Running too narrow of a wheel may angle the outer tread down toward axle centerline and make the contact patch screwey, but never make a tire "taller".    I will say that running a standard 33/12.50-15 on a 15x8 wheel works very well, especially for keeping the bead seated when running very low pressures offroad.  15x10's with the same tire loose the bead WAY easier.
-most companies post tire weights, or you can find them online.  Lighter tires will have a ton of advantages over heavier ones.  Unless you are running rocks and need a ultra-thick sidewall, go as light as you can.  
-the Interco Iroks wear fast and are not a great DD tire, but they are some of the best performing and lightest offroad tires out there.  They are also available in 31" and 33" sizes as the Irok ND (non-directional).
-for offroading, I prefer to buy a tire with Road hazard Warranty.  I am running Firestone Destination MT's (33x12.50x15).  They are a really great all-around tire with great treadwear performance.
-with 4:88 gears, I think you are better off with 33's than 31's.

[bootguy]

[quote
-with 4:88 gears, I think you are better off with 33's than 31's.
[/quote]

I get around 15 MPG right now, would I get a better MPG's going to a 33's?

[sharpxmen]

[quote
-with 4:88 gears, I think you are better off with 33's than 31's.


I get around 15 MPG right now, would I get a better MPG's going to a 33's?

no way, you increase both the weight and the frontal cross-section area (that's of course with the same tire width) so your mpg will decrease or stay the same best case scenario.

[Jeffy]

My opinions based on several years of noting fuel mileage and tire size differences and running a "few miles" offroad:
 
-hate to disagree, but there is no way wheel width will ever pinch a sidewall and increase tire diameter.  Running too narrow of a wheel may angle the outer tread down toward axle centerline and make the contact patch screwey, but never make a tire "taller".   

This is bit of an extreme but still holds true.  Of course the PSI being equal.  Now to get the same contact patch you would need to adjust the PSI.  A narrower wheel would require you to decrease the PSI a bit.  For instance when I was running 35x12.5R15 on a 8x15" I would run about 27 PSI to get a full contact patch.  The difference between running a wheel the same with as the tire and one 3-4" narrower is probably .5" or less.  Now the biggest difference is that some people don't like running the tire low on pressure.  You get more heat and the tires feel a lot softer.  But on hte plus side, like you said the bead doesn't break as easily.  An added plus is that the rim of the wheel is better protected as the tire tends to wrap around it.

no way, you increase both the weight and the frontal cross-section area (that's of course with the same tire width) so your mpg will decrease or stay the same best case scenario.

Well, if he's running 31's with 4.88's it's probably hurting his gas mileage some.  It's great for offroading but not so great for DD.  Though, going with larger tires has it's own hurdles.  The biggest one is unsprung weight.  That will hurt you're gas mileage as well.  Roll resistance is also a concern that most off roaders don't take into account.

But like I said, I'd probably try some skinny 33's if you want to DD it.  BFG is the only place to get skinny 33's though.  The AT's are 9.5" wide while the MT's are 10.5".

[dwtaylorpdx]

At one point I switched width only ,, I run 16" forged AL wheels, I switched from a measured, 32x12.50 to a 332.5x9.50,, I gained 4 MPG and its has not changed. Both toyo mud terrain, both Load range D. I think the tread hanging out in the air has much to do with it.

[Jeffy]

At one point I switched width only ,, I run 16" forged AL wheels, I switched from a measured, 32x12.50 to a 332.5x9.50,, I gained 4 MPG and its has not changed. Both toyo mud terrain, both Load range D. I think the tread hanging out in the air has much to do with it.

It sure doesn't help.  Especially if those tires are hanging way past the flares.  You can hear worn down interco's from a mile away.  When the main lugs wear down to the point where all the lugs are then touching the ground, they howl like a banshee because of all that turbulent air.