1337computing
New member
phattyduck":1gt395ek said:
Awesome thread but totally agree with phattyduck. AWD man can't mismatch tire sizes, width yes, size no. Very bad for your drive line.
Dred's Rahtid 165
- Thread starter GT4_DRED
- Start date
Awesome thread but totally agree with phattyduck. AWD man can't mismatch tire sizes, width yes, size no. Very bad for your drive line.
phattyduck
New member
NO.GT4_DRED":qr26k6w7 said:
225/40/18 and 215/40/18 have about 0.3" difference in rolling diameter. You need to stay within 1/16" (0.0625") and it is better to try to stay within 1/32" wear with regular tire rotations (which you can't do with mismatched tires).
See link:
http://www.tacomaworld.com/forum/tireca ... -225-40r18
-Charlie
1337computing
New member
phattyduck":clfofo8t said:
Phattyducks right man.
It actually measured out to be a 2mm-3mm difference front to rear, which I'm not worried about. I totally get your point, but the same difference can be had with tire wear, different brands of tires (same size) front to rear, or even the same set/size that grows differently at speed. I've seen guys use tires of the same size stretched across staggered 17x8/17x9, with the same or slightly greater variance and no ill effects. My experience is that there is some wiggle room around the numbers. You guys will be the first to know if there is catastrophic failure1337computing":12c3pm52 said:
alltrac101
Member
I wouldn't worry about it, i ran different size tires with the gram lights for years with a difference in diameter as much as 1/4", dyno, 1/4" mile, I went back & forth between the odd sized 18's & even sized 17's. I just changed it to mario's up-rated unit recently.MWP":2k8aqcw0 said:GT4_DRED":2k8aqcw0 said:You guys will be the first to know if there is catastrophic failure
There probably wont be.
Just give it a couple of years and your AllTrac will only be FWD because the viscous center is worn out.
Most of these guys with multiple alltracs have spare tranny/transfer cases available to them anyway & are capable of doing the switch themselves.
alltrac101":113y6flz said:I wouldn't worry about it, i ran different size tires with the gram lights for years with a difference in diameter as much as 1/4", dyno, 1/4" mile, I went back & forth between the odd sized 18's & even sized 17's. I just changed it to mario's up-rated unit recently.MWP":113y6flz said:GT4_DRED":113y6flz said:You guys will be the first to know if there is catastrophic failure
There probably wont be.
Just give it a couple of years and your AllTrac will only be FWD because the viscous center is worn out.
Most of these guys with multiple alltracs have spare tranny/transfer cases available to them anyway & are capable of doing the switch themselves.
You know it! With these cars we need spares for everything.
I wouldn't worry about it either.alltrac101
Member
What are you doing typing....shouldn't you be looking for some ting
underscore
Well-known member
GT4_DRED":48iaswv0 said:
You should never run different brands F/R on an AWD car. Running different sizes of the same tire is one thing, but running different brands or even models of tire means you need to physically measure the tire to 1/16 accuracy.
GT4times2":2a23obz6 said:alltrac101":2a23obz6 said:
You know it! With these cars we need spares for everything.
So you are going to knowingly kill a viscous center because you are too cheap/lazy to buy the correct tires?
Who knows how long Mario will keep making replacement centers availiable, and then there is the big job of changing it over.
Doesn't make much sense to me. :twisted:
alltrac101
Member
Dude, You need to get off your high horse & let it go.
Truth is, it doesn't have to make sense to you. "Cheap/lazy"? I'm gonna take the high road on this one..MWP":13mglcwf said:
The very fact that someone has tested and proved it out, with no ill effects, makes it debatable. Are you saying it to help, or rather to justify your own logic? Gotta be willing to accept new information so that your logic can expand. That's just one of the "sacred cows" that retards growth in the community; I'll file it next to the "17 psi max on pump gas" cow.MWP":13mglcwf said:
killemalltrac
New member
Dred you make me smile hahaha!!
GT4_DRED":grularc6 said:
He didn't say it had no ill effects.
If he does think that, i would like to know how he tested his old VC before and after running different tires sizes for some time to prove it did have no effect.
Actually, if it had no ill effects, why would you then change the viscous unit.
Why would you do this if the original VC was still working fine?
I am saying this to help, and i would love to be proven wrong (running miss-matched tyres sizes would be great).
It doesn't take much thought to work out that running different sizes causes the VC plates to always be turning against each other which does wear them out prematurely.
This is why Toyota say you shouldn't do it.
But hey, its your car, do what you like with it, but you've been warned.
BADNEWS
Member
Running tire sizes different like you are:
Front 225/40-18
Rear 235/40-18
Tension put on VC
10mph=3.8rpm
20mph=7.6rpm
30mph=11.5rpm
40mph=15.3rpm
50mph=19.2rpm
60mph=23rpm
70mph=26.8rpm
80mph=30.7rpm
90mph=34.5rpm
I know Mario had a stock VC tested and all his upgraded ones are done at 50rpm. At 50rpm the stock unit gives 130 ft/lbs or 175NM to the slower moving wheel.
For an example of what 50rpm difference is on the center diff: If you are cruising with all 4 wheels of 225/40-18 at 10mph and say you floor it. Now with some power you can break the front tires loose. If your rear tires have 100% traction at 10mph and your front spin, to achieve a 50rpm difference in the center diff your front tires will be going 13.75mph. So a difference of less than 4mph or 6.4km. And that speed difference is the same always. So if you're going 70mph, to strain the VC at 50rpm one set of tires has to be going 4mph faster or 74mph.
I personally wouldn't do the staggered tire size cause as you can see the higher the speeds the easier it is to mess up your VC. That is just my opinion with no real world testing to see if 50rpm is fast enough to get ill effects. Maybe someone else knows more about how much abuse/rpm difference a VC can take before it starts to go bad.
Front 225/40-18
Rear 235/40-18
Tension put on VC
10mph=3.8rpm
20mph=7.6rpm
30mph=11.5rpm
40mph=15.3rpm
50mph=19.2rpm
60mph=23rpm
70mph=26.8rpm
80mph=30.7rpm
90mph=34.5rpm
I know Mario had a stock VC tested and all his upgraded ones are done at 50rpm. At 50rpm the stock unit gives 130 ft/lbs or 175NM to the slower moving wheel.
For an example of what 50rpm difference is on the center diff: If you are cruising with all 4 wheels of 225/40-18 at 10mph and say you floor it. Now with some power you can break the front tires loose. If your rear tires have 100% traction at 10mph and your front spin, to achieve a 50rpm difference in the center diff your front tires will be going 13.75mph. So a difference of less than 4mph or 6.4km. And that speed difference is the same always. So if you're going 70mph, to strain the VC at 50rpm one set of tires has to be going 4mph faster or 74mph.
I personally wouldn't do the staggered tire size cause as you can see the higher the speeds the easier it is to mess up your VC. That is just my opinion with no real world testing to see if 50rpm is fast enough to get ill effects. Maybe someone else knows more about how much abuse/rpm difference a VC can take before it starts to go bad.