Swapping out one single tire - will this affect the full-time 4WD system? (12 Viewers)

[200 series]

So I noticed this small crack on the pax front, seperating the sidewall from the tire. Don't know what the previous owner did to cause this, or maybe even the tire shop that pulled the winters off to put this all-season set on.

This better image shows the scale of the crack relative to the valve stem:

I know I am asking on Ih8mud, but other than "throwing these stoopid 21' set away and putting on some proper 35 in. M/Ts with a 10 foot lift", can I throw in the spare tire which looks to be brand new and never rotated before by the previous owner , or will this destroy the full-time 4WD system? Or, should I put this defective tire on the rear axle, where a blow-out would be presumably less catastrophic (btw, I have driven on these tires HARD for about 3k kilometres before noticing this today). I would say the other tires have about 70% of tread life remaining.

Feels so wrong asking about these spaghetti sidewall 21inches on Ih8mud, but thanks in advance for all your help!

 

[bloc]

Your owner's manual will have the final say, but the one for my 2013 cruiser says to avoid mixing tires of "remarkably different treadwear."

Personally I wouldn't consider 30% tread depth difference remarkable.. on my stock-sized Defender LTX that works out to about .2" diameter in the whole tire/wheel, or something like 2% difference in circumference. IMO the all wheel drive system should be able to handle this with ease.

 

[doru]

I'll just use the spare. Although sidewall separation is not so unheard of, and some people drive like that for years, I would not play roulette with such a heavy vehicle and so little sidewall with 21", especially with an owner that drives hard.

Are you going to use the damaged one as the spare? I would rather buy a new tire instead.

 

[Sandroad]

Please don’t ever use that tire again, for your sake as well as others.

What is the age of the spare?

If you get a cheap thread depth gauge you’ll know exactly what you’re dealing with.

 

[bloc]

Age of spare is also a consideration.. the manual I cited specifically says 6-year limit.

 

[hoser]

A few millimeters difference in diameter won't matter. Match it up with the next largest diameter tire. If still concerned, some tire shops (particularly near race tracks) can shave down tires. Or if buying new, Tire Rack can shave it down for you.

 

[200 series]

Personally I wouldn't consider 30% tread depth difference remarkable.. on my stock-sized Defender LTX that works out to about .2" diameter in the whole tire/wheel, or something like 2% difference in circumference. IMO the all wheel drive system should be able to handle this with ease.

What are the potential damages of running a tire with mis-matched tread life? As far as my little mechanical understanding goes, only when driving in a perfectly straight line, will there be a constant difference in wheel speed which the front differential will counteract for. Unless driving on a straight highway (which there are very few of in the PNW), the diff will have to work anyways, as we rarely ever sit in a perfectly straight line for hours like someone in Texas might. I guess when turning one direction, the diff will also have to counter act for a bigger difference in speed due to mismatched tire diameter, but then turning the other direction, the diff will counteract less speed differential, so they should equal each other out? Feel free to correct my limited knowleadge, especially if there is more to it than just the diffs. I would really appreciate to learn more. Thanks!

 

[gaijin]

So I noticed this small crack on the pax front, seperating the sidewall from the tire. Don't know what the previous owner did to cause this, or maybe even the tire shop that pulled the winters off to put this all-season set on.View attachment 3923407
This better image shows the scale of the crack relative to the valve stem: View attachment 3923408 I know I am asking on Ih8mud, but other than "throwing these stoopid 21' set away and putting on some proper 35 in. M/Ts with a 10 foot lift", can I throw in the spare tire which looks to be brand new and never rotated before by the previous owner , or will this destroy the full-time 4WD system? Or, should I put this defective tire on the rear axle, where a blow-out would be presumably less catastrophic (btw, I have driven on these tires HARD for about 3k kilometres before noticing this today). I would say the other tires have about 70% of tread life remaining.

Feels so wrong asking about these spaghetti sidewall 21inches on Ih8mud, but thanks in advance for all your help!

Are all 5 tires (the 4 you have mounted now (1 damaged) and your spare) the same brand, model and size? Specifically, you state you had a tire shop put on "this all-season set" of tires - is your spare the same brand, size and model of all-season tire as the four you have mounted?

If the answer is, "No," then you need to buy a replacement tire that is the same brand, size and model as the good all-season tires you have mounted.

If the answer is, "Yes," then by all means take off the damaged tire and mount your spare - it should be fine (assuming it is not over 6 years old).

The only remaining question then is what to do with the damaged tire.

I would not use that damaged tire for anything, not even a spare. It is a dangerously damaged sidewall and is not repairable.

Ideally, you could purchase a replacement tire that is the same size, brand and model all-season tire as the 4 remaining tires.

HTH

 

[bloc]

What are the potential damages of running a tire with mis-matched tread life? As far as my little mechanical understanding goes, only when driving in a perfectly straight line, will there be a constant difference in wheel speed which the front differential will counteract for. Unless driving on a straight highway (which there are very few of in the PNW), the diff will have to work anyways, as we rarely ever sit in a perfectly straight line for hours like someone in Texas might. I guess when turning one direction, the diff will also have to counter act for a bigger difference in speed due to mismatched tire diameter, but then turning the other direction, the diff will counteract less speed differential, so they should equal each other out? Feel free to correct my limited knowleadge, especially if there is more to it than just the diffs. I would really appreciate to learn more. Thanks!

You aren't wrong, but it is a bit more complicated than that. On an all wheel drive system we need to consider not just the differential in the axle with the mismatched tire, but also the center diff.

For the tire diameter differences we are discussing here, it is basically a non-issue. But imagine we had a tire/wheel with, just for the sake of example, a 30% smaller circumference. When driving in a straight line the that wheel will be turning 30% more times per mile than the normal sized one.. now technically an open differential is literally designed to allow differences in rotating RPM for the sides of the vehicle, but as those rotational differences get too large we start asking too much of that differential. If one tire was stationary and the other spinning at 50mph.. you can imagine the little spider gears and thrust bushings saying "NOPE" before too long.

Now even without such an extreme RPM delta, over a long enough time, a smaller delta can also be a problem. Where exactly that is depends on the individual parts, fluid condition, all sorts of things. That is one reason toyota just left it open saying "remarkably different" treadwear.

With our center differential, if you have smaller tires on the front than the back, it will be asked to do the same job as an axle differential after the torque makes it out of the transmission. The nice thing here is only one tire on an axle being undersized means any RPM delta between front and rear (aka what the center diff needs to address) is half of that tire's relative undersize... because you still have one full-size tire on that axle still, and that axle diff averages those two.

All of that is in the context of an open differential, meaning no limited-slip functions. Any typical friction-based limited slip system would also be working to fight against a rpm delta from one side to the other.. but our axle diffs are open.. so that's not a concern.

But, our center diff is a Torsen design.. which means our hypothetical 30% difference at the front axle becomes a 15% difference between front and rear at the limited slip center diff... for potentially hours on end?

Fortunately toyota is well-known to over engineer their drivetrains, and OP's relative tire diameter difference is so small, that (IMO, as a judgement call) they aren't to the point of damaging anything, even over the long term. But I guess it comes down to what toyota meant by "remarkably different" treadwear.

An owner that upgrades their primary tires 2-3", but not the spare, then has to install that spare to get home on a lonely stretch of road in Utah? Whole different ball of wax.

OP is in the unfortunate position that avoiding all risk means buying four (if the spare isn't dated out) or five (if it is) new tires, because of one sidewall issue on 30% worn tires. I just can't see toyota having designed these amazing vehicles to be so fragile, personally.

 

[doru]

I'm with @bloc on this. This is real life scenario not idealized precise solid tire diameter. Think about driving with an under/over inflated tire as an equivalent scenario. That is such a common scenario.

 

[rherrco]

I'm with @bloc on this. This is real life scenario not idealized precise solid tire diameter. Think about driving with an under/over inflated tire as an equivalent scenario. That is such a common scenario.

I’ve heard it explained that an under inflated tire still has the same circumference, so it will not have a speed difference.

 

[hoser]

I’ve heard it explained that an under inflated tire still has the same circumference, so it will not have a speed difference.

That is incorrect. Indirect TPMS detects low pressure via ABS/Wheel speed sensors.

 

[bloc]

That is incorrect. Indirect TPMS detects low pressure via ABS/Wheel speed sensors.

At least one of my prior vehicles worked this way.

 

[rherrco]

That is incorrect. Indirect TPMS detects low pressure via ABS/Wheel speed sensors.

I agree with you, but had not thought about the TPMS function.

 

[gaijin]

Is no one else concerned that OP has not confirmed that all his tires are the same size, brand and model?

If they are not, then all this other discussion is moot, right?

@200 series , you still with us?

 

[200 series]

Is no one else concerned that OP has not confirmed that all his tires are the same size, brand and model?

If they are not, then all this other discussion is moot, right?

@200 series , you still with us?

Spare is same ofc! I believe they are Dunlop tires from factory. I tried switching out the spare last weekend, jacked up the AHC on high, then turned it off to reduce the amount of hand-jacking (trick learned from here). Only to find out that the toolbox is friggin' missing! I have a full-size spare but no way to lower it! Just extremely mad at the prev owner. Like how much can you even sell that toolbox forr?? Considering that there are only a few LXs and ZERO LCs sold here in Canada!!! Also, the owner's manual is missing too. Lessons learned, never buy a lease vehicle, at least not without REALLY thoroughly inspecting it and negotiating with the dealer, something that we clearly didn't do. At least we didn't find out that the toolbox is missing in the middle of the highway, hundreds of kilometres from home, that is a bullet dodged. So, status is still waiting for the toolbox to arrive...

 

[doru]

Here is a tool that is better for the garage than the OEM one for $26:

https://www.amazon.com/dp/B007TME6SO?ref_=ppx_hzsearch_conn_dt_b_fed_asin_title_2&th=1

You only need to shorten the side pins a bit with a grinder, Dremel, etc.
Works a lot better than the OEM and you can also use a power tool to make quick work of it.

While in there don't forget to apply FluidFilm to the chain and more importantly to the lift mechanism. On the side of the road you do not want to have the tool but the chain be stuck.