2 Tire Replacement Questions?

[VXNIT]

Tire dealer said that I could not replace jsut front two tires due to wear differences and TOD system would misread and cause problems. Said had to be 5/32. Anyone know if thei accurate or tire sales propiganda?

[twistedsymphony]

that's completely correct...

you could seriously screw stuff up.

if two tires are bald and two tires are fresh there is enough of a difference that at highway speeds you could blow the TOD system. As in literally overheat and explode. I've seen it happen to more rugged vehicles than the VX.

it says this in the manual in large print too... all 4 tires MUST be replaced at the same time...

this is hard-fast rule for any AWD/4WD vehicle.

basically when there is a difference in tire sizes between the front and the rear the axles are spinning at different speeds. The problem with a AWD or 4WD vehicle is that they connect in the transfer case so it's paramount that they spin at exactly the same speed.
Where the TOD has an electronically controlled clutch the difference in speed would be enough that the system thinks that the tires are slipping and engages the clutch to try to divert power to the front, at which point it wont help because the wheels ARENT actually slipping and the result is that rather than diverting power to the front you're just burning up the TOD... enough of that at a high enough speed and something WILL break and it will NOT be pleasant.

This will also completely screw up the ABS computer as well.


I cannot stress enough how bad of an idea it is to only replace 2 tires on an AWD vehicle... it is a very very bad idea.

I'm sure you can find people who have done it and didn't have problems, but they should consider themselves lucky.

[circmand]

for rotating your tires on a regular basis so wear happens on all 4 tires at the same rate

[VXNIT]

What if two rear tires are great and fronts are bad due to poor alignment and wear on insides significantly????????????????So what if I rotate two good rear tires to front and replace bad fronts placing new tires on rear?

[VXNIT]

bp

[VX1032]

Kia uses the same TOD system in their Sorento. They allow only an eigth of an inch difference in the circumference of each tire. Anything greater and the difference will cause damage to the transfer case over time. The greater the difference the faster the damage.

[circmand]

I have bought used rubber on this site and have had no problems swapping them out. Of course all were in good shape less than 10000 miles on them. Frankly I am surprised if it is so specific that the little spare works properly and a full size is not needed.

[tom4bren]

Correct me if I'm wrong but ...

If you HAVE to purchase only 2 new tires, they should go on the rear since the 'smaller diameter' old tires will be read as turning faster by the speed sensor. This will mean that the TOD will not be trying to engage to compensate for rear wheel spin.

That said, I don't advocate replacing only 2 tires. My front are also worn due to lack of rotation. I'll be replacing all 4 soon (anyone want 3 decent 33x12.50 Wranglers???)

Tom

[VehiGAZ]

it says this in the manual in large print too... all 4 tires MUST be replaced at the same time...

this is hard-fast rule for any AWD/4WD vehicle.

basically when there is a difference in tire sizes between the front and the rear the axles are spinning at different speeds. The problem with a AWD or 4WD vehicle is that they connect in the transfer case so it's paramount that they spin at exactly the same speed.
Where the TOD has an electronically controlled clutch the difference in speed would be enough that the system thinks that the tires are slipping and engages the clutch to try to divert power to the front, at which point it wont help because the wheels ARENT actually slipping and the result is that rather than diverting power to the front you're just burning up the TOD... enough of that at a high enough speed and something WILL break and it will NOT be pleasant.

This will also completely screw up the ABS computer as well.

I cannot stress enough how bad of an idea it is to only replace 2 tires on an AWD vehicle... it is a very very bad idea.

I'm sure you can find people who have done it and didn't have problems, but they should consider themselves lucky.

I don't agree with this.

It is paramount that the front tires are no larger than the rears in order to keep from freaking out the ToD system, but they don't need to be the same size all the time. And you definitely don't need to worry about slippage between the axles in the ToD - the ToD system is always slipping some - that's what it does.

If the front tires are larger than the rears, then as the truck rolls down the road, the speed of the back axle will be faster than the front, making the ToD system think you are losing grip at the rear, so the ToD engages the clutch pack to transfer more torque to the front axle to try to even out the grip. That's bad when it doesn't need to happen. In the opposite case, there is no problem because the ToD computer doesn't engage the front axle when it seems to be spinning faster (I am like 98% sure of this, but I might be wrong - it seems the ToD only tries to keep the rear axle from spinning, not the front).

This is why the manual tells you to use the mini-spare only on the front axle so as not to cause major driveability problems due to a very confused ToD system (exacerbated when only one rear tire is smaller!). If you get a flat on a rear tire, they want you to take a front off, put the spare in front, then use the one that was on the front axle to replace the flat rear.

So - my point is that you can mix-and-match tires of different circumference only if you put the larger (newer) tires in back.

[tom4bren]

IIRC the donut goes on the front because of the LSD rear as well as the reasons you stated.

[LittleBeast]

Tom made a reply on a tire thread so I had to come and see what kind terrible offset nonsense he was talking about but I am now disappointed, oh well.

[Thmstec]

Tom made a reply on a tire thread so I had to come and see what kind terrible offset nonsense he was talking about but I am now disappointed, oh well.

The love in this forum
So proud to be a member
(sincerely)

[VehiGAZ]

IIRC the donut goes on the front because of the LSD rear as well as the reasons you stated.

That's right! I didn't even think of that.

[tom4bren]

"Tom made a reply on a tire thread so I had to come and see what kind terrible offset nonsense he was talking about but I am now disappointed, oh well."

Coulda-Shoulda-Woulda. Unfortunately I couldn't figger out how to work it in since offset is a rim thing & not a tire thing

Offset like hope "is a good thing - maybe the best of things"

Shawshank Redemption

[LittleBeast]

Offset like hope "is a good thing - maybe the best of things"

Shawshank Redemption

Haha, wow, lol, that is awesome!!!!!

Oh and I left a tin can under a tree in VA with a surprise in it a few years back you should try to find it




















Years later.............
Tom finds the tree and opens the tin can to see a full set of wheel spacers made just for him..............