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Oversized Tire Question

J

jstrickl

Charter Member
SM 2003
Full Member
Joined
Feb 27, 2002
Messages
2,027
Location
Twin Cities, MN
If one was to install 32"-33" aggressive rubber on the stock rims (let's just assume it will fit the 16" or 17" factory rim) or on a larger 10" wide rim, how noticeable:
? a loss in performance (acceleration)
? a drop in mileage
? change in ride quality (bouncier?)

Just curious as this is something I have been tinkering with in the back of my mind. Maybe not on this Av, maybe on the next. I just am curious to know how much economy and ride is compromised in a more utilitarian rig.

Jamie
 
I am no where near the expert that some others here are, but, I can share my experience. I have the stock Z71 wheel (17x7.5") and I have 305/70R17 Goodyear Wrangler MTR tires. (I have a 3" body lift for the clearance) Acceleration and mileage I am sure changed on paper, But I did not notice any seat of the pants change. Making the tires bigger effectively changes your rear end gear ratio, thus in theory acceleration will get a little worse, mileage might get better. My ride got a little better. The stock tires are only a 2 ply tire and the new MTR's are an 8 ply tire. This is a stiffer tire giving a more solid feel. My mileage is still the same as it was. Just my opinion, on acceleration. I never ran 0-60 times to see if it is different.
 
Thanks for the info. Hoping for more answers like yours. I have seen some very cool "hooked-up" Avs at my dealership so I would like to know what effect tires can have in the event my next Av (2.5 years away) should be a lifted one.

Jamie
 
Jamie!

Sorry I didn't catch this topic (until you mentioned it in the 4X4 forum)!

I don't actually know how wide the stock 17" wheels are, so I cannot speak effectively to what size tires you can get away with on those wheels. I will, however, offer the following observations, after putting about 3000 miles on my BFG Mud Terrains.

I have mine mounted on 8 inch wide wheels and the wheels appear to be just the right width for the 285/75/16's that I'm running. Seems to me with a little "puffiness" you could certainly get away with a rim width as much as one inch narrower (7inch wheels) with this rubber. I'd hesitate to go narrower than 7 inch wheels with the 285's... but that's just IMO.

The tire noise on the street is noticable, but by no means intrusive... and that's with Mud Terrains. An All Terrain tire would be even quieter. The ride is, if anything, a tiny bit better, although I did notice that at highway speeds the steering is a little more vague on center.

Fuel mileage is hard to nail down exactly, as my driving habits and routes change frequently, but based on the numbers I've gathered, it looks as if I'm losing between .2 and .8 miles per gallon with the larger tires. This is further complicated by the fact that the dealer's largest computer setting isn't as large as my tires...thus the speedo (and odometer) are a bit off (about 4%) and I've actually traveled farther than the odometer indicates.

Performance seems unharmed by the larger rubber... my Av seems to have a rather flat spot just off idle that bugs the hell out of me, but it was present with the stock tires as well. I've not actually run a 1/4 mile, so I have no objective data but "seat of the pants" feel makes it hard to tell the difference, leading me to think that you'd lose maybe a 10th in the quarter, if that.

This is all just IMHO :)
 
jamie said:
? a loss in performance (acceleration)
? a drop in mileage
? change in ride quality (bouncier?)
Click to expand...

If the new tire rolling OD is larger than acceleration will decrease but top speed will increase...are you gonna notice not likely for 1" in tire OD.

Fuel milage would be difficult to say....too many parameters to llok at....You have wind resistance of the tires while rolling, also rolling tire friction, weight, etc I would say any effect would be small for a 1" change in tire OD......Heck just hammer it a few times and this messes with our Miles per tank.... >:D

I think ride quality would also depend on new tire chosen...heck with in the same size tire but varying brands the ride quality can greatly change as well as noise and stopping distance...

I realize I did not answer questions but well it is hard to answer....I would look for people with tires you are interested in and ask them questions...

HTH


 
Jamie, you asked about 32" - 33" "aggressive rubber" on stock rims. I mounted 32.4" Goodyear Wrangler MT/Rs (certainly "aggressive") on the stock Z71 (they are 7.5" wide) rims. 275/70R17s

I also recalibrated my speedo with the HPP3.

I always had a little, very slight flat spot off-idle, still there but I think it may be that this Av is the heaviest rig I have ever owned and it takes a big push to get her in motion.

I reprogrammed the Av with the HPP3 at the same time I recalibrated the speedo (ie just after the tire swap) so I did not have a chance to "before and after" impressions on just the tire swap. Plus I went from stock Av Firestone Wilderness LE's on 16" rims, a 30.6 OD I think, to the MT/Rs - pretty big difference, perhaps a tad more oversteer on hard corners but that might be about it. No vagueness at highway speed - big tread yes, but very stiff sidewall on the MT/Rs. I do notice a bit of noise, but only if the windows are down, quiet as ever otherwise.

Definitely not bouncier, the very car-like ride quality is still there.

Oh and no clearence problems with new bigger tires using stock setup
 
I tend to agree with much that has been written on this topic. ?

~ a loss in performance (acceleration) ?
Not noticable unless you jump several sizes larger. This doesn't consider air pressure in larger tires and stiffness of sidewalls.

~ a drop in mileage
If you are actually doing it for better off-roading adventures, then oh yeah you will see a drop in mpg. Simply because you will be out on the trails more, in 4wd more, and hopefully in 4lo a lot more. All while working the engine and suspension.

~ change in ride quality (bouncier?)
It will vary with the tire you put on and the tire pressure you ride them with. Some stiff sidewalled tires may give you a less 'bouncy' ride under the right air pressure.

Main thing to consider is why are you doing it? For show or for go? ?For go - - the off-road handling increases will far outshadow any on-road handling differences.
 
These have all been great answers. Thanks all for your valued input. I have been considering (just considering) similar setup to jackalanche's utilizing the stock rims. Just wanted to be sure that the ride won't go to heck with bigger, wider rubber. You have all done a great service to us all who envy the big aggressive tire setups!

Jamie
 
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