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| North American Grand Cherokee Association | ||
| Your one stop source for Jeep Grand Cherokee Information | ||
We ZJ Staffers
regularly face the oft-asked question, "what's the best tire for my rig". In
fact we're asked this so often that it's hard to answer the question any more. There are
so many variables and different individuals' requirements that there is no
"correct" answer. You just have to try and figure out what is best for you.
Since I've recently had to do just that, here's a case study for the purchase of 31x10.5
R15 BF Goodrich Mud Terrain.
How do you decide?
Most of us do 95% or more of our driving on the street. Hate to admit it don't you! So of course the most reasonable choice is something that delivers very good street performance and acceptable off-road performance, in other words, All-Terrain. Having followed this sound advice for the last 20 years, it's about damn time I got the tires I always wanted! The BFG MT's used to be gnarly tires. Oh sure you could get Ground Hawgs or Gumbo Monster Mudders if you were a real glutton for punishment. Now days, compared to Interco Super Swampers and Boggers, the BFG MTs look mild.
How do they ride?
On road:
As expected, they make more noise than
the stockers, especially when decelerating and around 25 mph. They make more noise than
the Borla exhaust and FIPK combined. At least, given the Grand Cherokees' good sound
insulation, it's not at all unpleasant - 2 points for good stereo. At parking lot speed,
you know they're there as you can almost feel every lug slap the pavement. This sensation
diminishes a bit after the tread rounds off a little from wear. Handling is a little
stiffer at my current inflation, near 40 PSI compared to 33 PSI on the Wrangler GSA's they
replace. Their street manners aren't bad at all, I expected worse. I plan to sipe the
center lugs for better wet pavement handling and slickrock traction. The increase in final
drive ratio (about 7%) is not as noticeable as expected to my modified V8, though mpg is
suffering, about a 1 MPG decline with corrected speedometer. Don't kid yourself about this
though. It costs more energy to move bigger and knobbier tires and more brakes to
stop them.
Off road:
WOW! The improvement was much greater than expected. When aired down to a conservative 18 PSI, the one inch increase in section height offers much more cushion against rocky dirt roads than the previous carcass. The tread so far has proved to be non-slip, even in places where I'd previously spun with four wheels on the ground. This brand, with patented Tri-Guard Construction, is legendary for its toughness. It is comforting to have tires you can count on when you are out there. Finally, when it comes to minimum ground clearance, there's no substitute for taller tires.
How do they fit?
Oh 31s, how do thine wheel wells clear thee?
First of all, 31-inch diameter tires will NOT fit stock Grand Cherokees. On the street, there is plenty of clearance. But off road, wheel well clearance with 31`s is an issue, even with a 3.5-inch lift.
But when off-roading, that is,
compressing your suspension while turning, they'll get the lower front edge of your fender
lips. The bottom, leading edge and the inner front face of the wheel wells are subject to
contact under compression and turning. You need at least 3 inches of lift. I have 3.5
Teraflex; that and about 1.25 inches of trimming off the lower, inner front fender and
they almost clear. But it is possible to relieve these areas an inch or so without
disfiguring the vehicle. I did a little dirt pile testing - with the anti-sway bar
connected, the tires clear at maximum compression. But so what? When I 4-wheel, I air-down
and disconnect, that's the rules! When disconnected and at full-stuff, there is still
fender contact even with mild trimming. I'll live with that for now, at least until I'm
ready to hog out that precious plastic, or the trail does it for me. As a bonus, this size
tires still fits in the stock interior spare location.
Final thoughts - Speedometer recalibration - just do it. It's cheap and easy. Changing your speedometer gear is way easier than changing your oil! For details on how-to, check out our great article on the subject. One of the intangibles that's hard to put a price tag on is appearance. Knobby tires just look so much more purposeful and four-wheel-drive-like than milder tread patterns. While I'm not given to vanity, I'll admit to sometimes just standing there admiring my vehicle, day dreaming of the pull of low range and nothing but blue sky over the hood. They look great. So what's the hardest part about choosing new tires? Is it the brand, the size, the style? Nope, it's deciding whether to put the white letters out or in!
North American Grand Cherokee Association
www.nagca.com
Copyright © 2006 by NAGCA All rights reserved.