Running staggered tires

[VehiCrow]

Hey all,
I am getting ready to start looking at tire options.
I was wondering if any one has run a staggered set up.
Like a 255 in front and say a 265 or 275 in the rear.

I mainly use mine as a daily driver. I also run it like I stole it every chance I get.
Any input would be greatly appreciated.
Thanks

[PK]

I don't think your TOD will like you very much. It is very sensitive to tyres of different diameter. Even same size tyres new mixed with half worn will make it go crazy.

IMHO, you couldn't pick a worse car to try this on.

PK

[Cobrajet]

One word... NO!!

[WormGod]

That would be an AWD fail. Negative sir.

[JoFotoz]

Ditto above...

TOD would likely go CRAZY :eek:

Only way this would work IMO...
..is if you disconnect TOD under pass seat and drive 2w rear drive only.

Jo

[MSHardeman]

Like the others said, I would recommend against running different sized tires. The TOD does NOT like it and will go crazy shifting into, and out of, 4WD. In case you don't know the TOD works by sensing the speed of each wheel. When it senses one wheel spinning faster than the others (like spinning your wheels on ice), it activates the clutches in the transfer case and sends some percentage of the power to the front wheels. It does this in quick little spurts and does not lock the transfer case into four wheel drive. It will continue to do this until all four wheels start rotating at the same speed (you stopped skidding on the ice), at which point it goes back into monitor mode and leaves the transfer case in two wheel drive mode (sort of). IF you use different sized tires, the TOD senses that some of the tires are rotating faster than the others (due to different diameters) so it thinks that the tires are slipping and it goes into it's little dance of pulsing power to the front wheels, but since it can't ever correct what it sees as a dangerous situation (wheel slip) it will continue to pulse power to the front wheels which puts a lot of wear and tear on all of your drive train components. (sorry for the explanation if you already knew how the TOD worked)

If you really want to do this, I would think that you would have to disconnect the TOD computer to take it completely offline so it won't be fighting against the different tire sizes. You could still manually drop the transfer case into 4lo, but that would be about it.

[VehiCrow]

Hey all,

Thanks for the input.
I thought I would give it a shot.
Given I had a Porsche Macan Park next to me when I was out.
I saw they have there set up Staggered but I am sure they Don't have TOD.
Thanks again guys

[MSHardeman]

Does a Macan have different diameter tires or just different widths? I would think that you COULD use different width tires on the VX as long as the diameter is the same. :_confused

[Cobrajet]

Does a Macan have different diameter tires or just different widths? I would think that you COULD use different width tires on the VX as long as the diameter is the same. :_confused

They are actually "staggered" sizes, but the electronics take all of that into consideration.

[VehiCrow]

The one that was parked next to me was running 235/19 in front and 255/19 in rear.
I was more curious about the width then the Diameter. Still keeping same size rims.

[PK]

You left out the most important dimension - the height profile.
235 and 255 are the tread width.
19 is the wheel rim diameter.

After the 235 and 255 there would have been the height profile (anything from 35 to 75% of the width.

It is only when all 3 dimensions are known, that you can calculate the rolling diameter of the tyre.


PK

[VehiCrow]

I am sure they were 45's on both

[Starglider]

The only way this would work is if you changed the differential gearing to match the change in tire circumference. But even if you could find the appropriate replacement diff it would be very difficult to get it exactly right.

[JoFotoz]

Diffs dont have to be changed.. IMO :)


The only way this would work is if you changed the differential gearing to match the change in tire circumference.
But even if you could find the appropriate replacement diff it would be very difficult to get it exactly right.

Many have changed tire diam, hence Cirumf and run OEM diffs.
(Tire width doesnt matter to the gearing of the diffs.)

It will give false speedo/mileage readings with larger/smaller tire diam/circumf...
.........but TOD etc will all still work as long as all 4 are matched.

And if you do change diffs... as some, including me have....

...you must change both :smack:

Jo

.

[Starglider]

It will give false speedo/mileage readings with larger/smaller tire diam/circumf...
.........but TOD etc will all still work as long as all 4 are matched.

And if you do change diffs... as some, including me have....

...you must change both

What I meant was, in theory you could run different sized tires on the back vs the front if the differential ratios were varied by the same amount, so that the RPM seen at the transfer case would still match. i.e. if putting larger tires on the back on, replace rear diff with one that has slightly more reduction.

However this wouldn't work in practice because;
a) it would be really hard to get exactly the right ratio and
b) I just remembered that TOD uses individual wheel speed sensors, not drive shaft sensors, so it would still see slip and constantly engage.

In theory you could fix (b) by hacking the wheel sensor electronics or magnet ring, but that's a crazy amount of effort just to have different tires.

[JoFotoz]

Yea..NO...not in theory..not even in practice !!

To make the transfer case/TOD work in harmony ...

...front AND rear diff need to be equal.

AND..all tire sizes need to equal.


You have a VERY limited set of options of diff gearing on the 10 & 12 bolt
Isuzu diffs.
( so..the "matching the ratio"...is not possible..you get as close as you can!)

I run 4.77's..It close! for my 35's..but could be better!

If you have different diff front to back..
...you"ll
(A) explode the TOD..
..and
(B)..grenade the transfer case...
and
(C) never get going!..at all!


Please ...do correct me if I'm wrong..
.....but I have re-geared several VX''s :)

I think I have this right :)

Jo

[VehiCrow]

Hey All,
So in Short 235/45/18 & 255/45/18
Will have different diameters.
I thought just the width would be different.
I just want to run a little bit wider in the rear then the front.

[Cobrajet]

Hey All,
So in Short 235/45/18 & 255/45/18
Will have different diameters.
I thought just the width would be different.
I just want to run a little bit wider in the rear then the front.

Definitely not the same diameter. Check a few different tire spec sheets on tirerack.com, and you can find out which tires will have the same diameter.

One I checked:
235/45/18 = 26.4"
255/45/18 = 26.7"

By comparison, the stock Bridgestone Dueler 245/60R18 is 29.7".

[Mile High VX]

285/65 18 is 32.6" diameter with a width of 11.22".

265/70 18 is 32.6" diameter with a width of 10.43".

Not sure what might be available in these sizes but the calculator I used said they were the same diameter.

[VehiCrow]

Hey guys thanks for the info.
I guess I will have to do some more digging to match diameters.
Thanks again

[mdwyer]

b) I just remembered that TOD uses individual wheel speed sensors, not drive shaft sensors, so it would still see slip and constantly engage.

I'm not sure this is true. There are wheel speed sensors, but they only feed into the ABS system. I'm pretty sure the TOD speed sensors are completely separate and only on the drive shafts, and it is only able to detect front/back differences.

Doesn't change the fact that it is probably a bad idea to run different sized tires! I'd be curious if tires the same diameter would work okay, though... I just wouldn't be curious enough to do it on MY VX. :)