Tire Aspect Ratio myth put to rest...

Casper

Casper

New member
As of today that I can now say that mixing aspect ratio tires together (at least close in ratio) will not set off the VSC.

I have been running 275/60/17s in Toyo Proxes S/Ts and they have been fantastic. But today in an absolute emergency I had to go off road and run over a crap load of bushes/cactus and i got a puncture in the sidewall (of course..they are sport truck tires). I then changed the tire with the OEM sized Dunlop spare (265/65/17) and had absolute no issues with the VSC going off as many have theorized about running mixed Aspect ratio setups, incase of an upsized Revo or such going out and having to use the OEM spare

just wanted to inform the board...if no one had posted this kind of information yet.
 
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Well, your Toyo and Dunlops are very close in size (diameter)...a diameter difference of only 1.87%.

For most people on this board, they are going from 265/65/17 to 265/70/17 (about 31" to 32" tires). The difference in diameter is about 3.3%.

Therefore, i wonder if VSC will have more issues with a change of 3.29% in diameter. From what i understand, anything above 3% change in diameter is significant.

Thanks for the info.
 
I've wondered about this issue too. I have a set of Revo's on 16" OEM steel wheels for winter use, but only have 4, so I keep the OEM 17" Bridgestone spare onboard. Because I went with the 16" tire, the overall height difference isn't that much. I just went through the factory manuals, and can't find any reference to how the VSC actually is triggered. I'm pretty sure it uses the ABS wheel sensors to monitor wheel spin, but nothing on what difference will set it off. I would think that it has to allow for some difference between wheels or it would go off when you make a turn. Anybody have any more in-depth info on how this system works?
 
VSC utilizes a system of sensors of which include the ABS, yaw sensors, steering angle and such.

A simple 3% or even 10% is not going to trigger this system as it's major input would be the yaw sensor.

The fear in running different height tires is more in wearing out the diff's in a 4wd vehicle than tripping the VSC.
 
Don't forget...there is also traction control, whose main function is to detect wheel speed differences.
 
Thai,

i know that you previously mentioned that 3% is what you heard...just wondering if you have a reference on that one? Its not tech info that is listed anywhere.
 
Thai said:
It's not what i have heard...it's easily calculated. Go to this thread: http://www.toyota-4runner.org/showthread.php?s=&threadid=70

Scroll down to the last post by me and use the calculator. 3.3% is accurate.
Click to expand...

I think Casper is looking for a reference to the "From what i understand, anything above 3% change in diameter is significant."

I too am curious, because if I could buy 4 instead of 5 tires, that would save some $$, not to mention the problem of carrying an oversized spare..
 
Mnrunr, do the calculation (from link above) and you will see why 3% is significant....
 
Thai said:
Mnrunr, do the calculation (from link above) and you will see why 3% is significant....
Click to expand...

My bad, I thought this was the miata calculator..
Didnt know or think about brake failure..
 
MnRunr said:
My bad, I thought this was the miata calculator..
Didnt know or think about brake failure..
Click to expand...

Well, i am not sure if THAT statement is more CYA (cover your ass) or true physics. I doubt brake failure because this modification (upsizing to 32" tires from 31") is the most popular thing since sliced bread! But, it is still something to keep in mind in terms of how much you want to upsize (say 33" or 35" boggers) and also how it affects the computer brain in your 4runner.

My guess is that you can drive a short distance at slow speed if you were in a jam with one 31" tire and the rest 32" tires. However, i would not do much else...and replace tire ASAP. Of course, it would be nice if someone has the balls to test this out once and for all. I don't.:D
 
Thai..

i trust your math brother. I was asking since you stated that

thai said:
"Therefore, i wonder if VSC will have more issues with a change of 3.29% in diameter. From what i understand, anything above 3% change in diameter is significant."
Click to expand...

I am totally aware that 3% is rather large but does anyone really know the cut off for the VSC system or are we just guessing that its in the 3% range?
 
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