re_guderian
SILVER Star
Uh, turning corners???
Tire rotation question (1 Viewer)
- Thread starter 70 FJ40
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Leave it to the internet to micro manage everything. Running equally sized tires with different tread wear is COMPLETELY fine. They're open differentials and not that sensitive AT ALL.
Five tire rotation every 5k miles here - the corners have no idea if they're seeing a primary wheel or a spare as there's zero difference...
Concerns about tire diameter are not necessarily about open diffs vs. locked or limited slips diffs. The issue may be with the many sophisticated electronic controls of our 100s that depend on input from wheel speed sensors. How much of a difference in wheel speed (revs per mile) does it take to have ABS, ATRAC, VSC, etc. operate incorrectly?
The difference in wheel speed (revs per mile) between a fully worn AT tire and a brand new AT tire is almost as much as the difference between adjacent sizes. For example, a new 275/65-18 BFG T/A K02 tire has 15/32” of tread depth. If fully worn, the difference in diameter from new is therefore almost an inch. That’s about the same diameter difference as between a new 275/65-18 and a new 275/70-18 BFG T/A K02. So, if the difference between and fully worn tire and a new tire is the same as the difference between new tires of adjacent sizes, it seems advisable to not run tires that are worn to very different depths. 21 revs per mile difference in this example.
A couple of references:
1. From my owner’s manual:
“Toyota recommends that all 4 tires, or least both front or both rear tires, be replaced as a set.”
2. From a Tire Rack article:
Matching Tires on Four-Wheel Drive & All-Wheel Drive Vehicles
DirtDawg
"It'd be alot cooler if you did"
I completely agree. I was just agreeing with him in the sense that it will cause no mechanical damage.
I do know that our vehicles are sensitive, my '00 will set off the light around certain highway mountain bends. I am curious as to if the vehicles electronics will handle the wear difference in the same size set of tires, as compared to a differently sized set.
I do believe a small spare or equivalent is acceptable to limp you off the trail or into town at 20 mph.
You might want to check your sources on that Audi number. References I have indicate they only allow 1/8 inch rolling radius difference in tread depth, which comes out to far less that 12% difference in circumference. 12% difference in circumference would mean close to 3 inches difference in diameter on a Q5 tire.
That Tire Rack article seems to make sense.
Yet, with reference to the center diff, I have a hard time believing that T engineers haven't anticipated this debate especially considering the design intent for these rigs (rugged terrain, 3rd world countries, etc.). That includes using mis-matched tire diameter due to wear/spare/ etc. I would buy into the argument for other "non truck based" AWD platforms since the are strictly pavement runners (audis, porches, etc.).
Admittedly, I am ignorant w/r to fluid based differentials. But if fluid shear is used to transfer torque in our center diffs, and that fluid shear properties degrade, how will that cause a hardware failure in the drive-line? Just drain and replace. As if life where so easy!
Now, I certainly buy into the traction control, anti-skid, etc. problems as those seem to depend on judicious brake applications. But again, these are "world" trucks (or at least were in their pedigrees (fj40/60)). Even the 80's are world chassis with world tire diameter challenges baked into the design.
Inquiring minds want to know.....
Yet, with reference to the center diff, I have a hard time believing that T engineers haven't anticipated this debate especially considering the design intent for these rigs (rugged terrain, 3rd world countries, etc.). That includes using mis-matched tire diameter due to wear/spare/ etc. I would buy into the argument for other "non truck based" AWD platforms since the are strictly pavement runners (audis, porches, etc.).
Admittedly, I am ignorant w/r to fluid based differentials. But if fluid shear is used to transfer torque in our center diffs, and that fluid shear properties degrade, how will that cause a hardware failure in the drive-line? Just drain and replace. As if life where so easy!
Now, I certainly buy into the traction control, anti-skid, etc. problems as those seem to depend on judicious brake applications. But again, these are "world" trucks (or at least were in their pedigrees (fj40/60)). Even the 80's are world chassis with world tire diameter challenges baked into the design.
Inquiring minds want to know.....
re_guderian
SILVER Star
You guys are killing me... As if a bunch a yay-hoos on the internet are going to discover a tragic flaw of mere millimeters that a whole generation of dedicated, educated, highly paid and focused engineers at Toyota overlooked over 2 decades ago when they were designing this...
C'mon, use your smarts. There's all kinds of things that cause rolling diameters to be different. Tread wear, pressure, weight distribution, etc. etc. If LC's were SO sensitive to these factors, we'd have seen the disastrous results literally a decade ago, given that some of these rigs are nearing 20 years old. As to the electronics, I also think you're vastly over-simplifying the algorithms that go into them. Think road bank, steering, overall speed, individual wheel speed, gear, throttle position, elapsed time, etc. etc.
Rotate all 5 tires, you'll be fine. Or don't, panic, freak out, and never, ever be able to sleep at night knowing that your tires will never be the EXACT same rolling diameter ever again after leaving the installer...
C'mon, use your smarts. There's all kinds of things that cause rolling diameters to be different. Tread wear, pressure, weight distribution, etc. etc. If LC's were SO sensitive to these factors, we'd have seen the disastrous results literally a decade ago, given that some of these rigs are nearing 20 years old. As to the electronics, I also think you're vastly over-simplifying the algorithms that go into them. Think road bank, steering, overall speed, individual wheel speed, gear, throttle position, elapsed time, etc. etc.
Rotate all 5 tires, you'll be fine. Or don't, panic, freak out, and never, ever be able to sleep at night knowing that your tires will never be the EXACT same rolling diameter ever again after leaving the installer...
You guys are killing me... As if a bunch a yay-hoos on the internet are going to discover a tragic flaw of mere millimeters that a whole generation of dedicated, educated, highly paid and focused engineers at Toyota overlooked over 2 decades ago when they were designing this...
C'mon, use your smarts. There's all kinds of things that cause rolling diameters to be different. Tread wear, pressure, weight distribution, etc. etc. If LC's were SO sensitive to these factors, we'd have seen the disastrous results literally a decade ago, given that some of these rigs are nearing 20 years old. As to the electronics, I also think you're vastly over-simplifying the algorithms that go into them. Think road bank, steering, overall speed, individual wheel speed, gear, throttle position, elapsed time, etc. etc.
Rotate all 5 tires, you'll be fine. Or don't, panic, freak out, and never, ever be able to sleep at night knowing that your tires will never be the EXACT same rolling diameter ever again after leaving the installer...
You have the 6th human sense....known as Common Sense. You're rare and horrify people in life and on the internet
uHu
Bridgeburner
Real world experience:
I put a spare wheel on one of the fronts which was more worn than the rears. No problems driving, until I engaged CDL. It was impossible to get the CDL to disengage without rocking a bit back and forth, which could be a bit awkward some places. I then moved this slighly smaller spare to the rear, and I would still have binding with the CDL on, but now I could turn a bit left or right to get it to release (as the fronts would then roll a bit longer distance/faster, which compensated for the larger diameter up front).
No problem with any of this, just an example of the effects of a small difference in tire diameter.
I put a spare wheel on one of the fronts which was more worn than the rears. No problems driving, until I engaged CDL. It was impossible to get the CDL to disengage without rocking a bit back and forth, which could be a bit awkward some places. I then moved this slighly smaller spare to the rear, and I would still have binding with the CDL on, but now I could turn a bit left or right to get it to release (as the fronts would then roll a bit longer distance/faster, which compensated for the larger diameter up front).
No problem with any of this, just an example of the effects of a small difference in tire diameter.
5 tire rotation every 5k miles with my 35's BFG KM2's. I did a 4 tire the last time and left the 5th tire hanging behind my my ARB bumper ( thinking I would be buying the same tires again), but noticed 3+ yrs later when I put it into rotation with another new set it showed plenty of cracking... so I just assume get the use and longevity of a 5 tire rotation when they're in their prime.
