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supercazzola said:
Had to share this...
I've seen a good amount of people who do that. As long as you keep it off the rear end and don't lock up your front end, I believe it'll work. It'll look really goofy tho!
 

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or maybe his tire dealer only had 4 of what he had put on and the 5th is on order. I am going thru that right now. dealer had 4 raceline raptors and had to order in a 5th.
 

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I would think that the electroinc nanny might have issues with this setup no matter where it is installed. I have heard that if you dont rotate the spare and use it the ESP will think you are skidding even if it is a few mm off. I could not put it in the rear of my rig due to the LSD, and in the front the lean would be dangerous. I see this all the time around here, even the tire shop thought it was strange that I wanted to change all five new tires...
 

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I would think that the electroinc nanny might have issues with this setup no matter where it is installed. I have heard that if you dont rotate the spare and use it the ESP will think you are skidding even if it is a few mm off. I could not put it in the rear of my rig due to the LSD, and in the front the lean would be dangerous. I see this all the time around here, even the tire shop thought it was strange that I wanted to change all five new tires...
I think you've been given some bad info there chief.
Some people never use their spare tire, don't even put it into the rotation, I havent heard of any of them skidding off the road. My spare gets rotated, but when its not in the rotation, I'm also not skidding off the road.
You could use it on your LSD axle, but just for a short distance, say to get you to a tire shop, but if you had a bit further to go, yes put one of the front tires on the rear and the spare on the front.
 

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I assume it would mess with your traffic control...

The axle on which you install the tiny spare will have both wheels turning at different rates the whole time. So...steering wheel is straight, vehicle think one tire is rotating at a different rate (because it is)...heck, folks have issues installing a lift and not re-centering their steering...
 

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I think you've been given some bad info there chief.
Some people never use their spare tire, don't even put it into the rotation, I havent heard of any of them skidding off the road. My spare gets rotated, but when its not in the rotation, I'm also not skidding off the road.
You could use it on your LSD axle, but just for a short distance, say to get you to a tire shop, but if you had a bit further to go, yes put one of the front tires on the rear and the spare on the front.
I am fairly sure I am correct, perhaps you did not read correclty? :hide:
It is not that you are sliding off the road. Since one tire would be turning slower than the other the computer would see it as slippage and try to correct. The tires have to be very close in diameter or else the stability control calibration will be thrown off. The ESP will kick in more easily one direction, while being less sensitive the other steering direction.

On a non-drive wheel, up front, it would be ok to limp home, unless you had to slam on the brakes, and your ABS and stability control, etc, went crazy trying to figure out why your steering angle said you wanted to go straight, but you were obviously turning towards the side the larger tire was on (As the smaller tire would tell the computer that it was going faster/was the tire on the outside tack in a turn, etc...)

Similarly, in an emergency maneuver, the difference in steering input and tire speed signals would make the jeep think your were on ice or something, and it would kick in measures to keep you from spinning out, etc.

The spider gears don't normally turn when going in a straight line. Putting different size tires on each side of the diff will cause the spiders to spin. That will indeed cause more heat than normal.

Now put that in a limited slip and you have clutch wear too.

So, if you were careful, you could probably limp home, but there could be drama. Or turn off the ESP.

Even a 1/8" could cause issues depending on how sensitive the computer is.
 

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I would think that the electroinc nanny might have issues with this setup no matter where it is installed. I have heard that if you dont rotate the spare and use it the ESP will think you are skidding even if it is a few mm off. I could not put it in the rear of my rig due to the LSD, and in the front the lean would be dangerous. I see this all the time around here, even the tire shop thought it was strange that I wanted to change all five new tires...
I have 5 M/T's with no sensors and the only irritant is the tire icon that is always on my dash. I ignore it. Or are you referring to having one tire smaller than the rest?
 

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MaskMan said:
I am fairly sure I am correct, perhaps you did not read correclty? :hide:
It is not that you are sliding off the road. Since one tire would be turning slower than the other the computer would see it as slippage and try to correct. The tires have to be very close in diameter or else the stability control calibration will be thrown off. The ESP will kick in more easily one direction, while being less sensitive the other steering direction.

On a non-drive wheel, up front, it would be ok to limp home, unless you had to slam on the brakes, and your ABS and stability control, etc, went crazy trying to figure out why your steering angle said you wanted to go straight, but you were obviously turning towards the side the larger tire was on (As the smaller tire would tell the computer that it was going faster/was the tire on the outside tack in a turn, etc...)

Similarly, in an emergency maneuver, the difference in steering input and tire speed signals would make the jeep think your were on ice or something, and it would kick in measures to keep you from spinning out, etc.

The spider gears don't normally turn when going in a straight line. Putting different size tires on each side of the diff will cause the spiders to spin. That will indeed cause more heat than normal.

Now put that in a limited slip and you have clutch wear too.

So, if you were careful, you could probably limp home, but there could be drama. Or turn off the ESP.

Even a 1/8" could cause issues depending on how sensitive the computer is.
I don't think u would have these issues as the sensors are not at the outer diameter of the tire. Your abs sensors are all reading at the same distance away from the centerline of your axle. With different sized tires, the rpm at which they turn would be the same no matter what the difference is in diameter. Your surface speed is what changes though as this is affected by the circumference.

So as long as all the sensors are set at the same distance away from the centerline of the axles, and are not mounted at the very outside diameter of the wheel, then you should be fine.

The other option is to air down the 3 larger tires as much as safely possible to get your vehicle to sit more level. This will just help with road manners so the jeep does not want to pull one way or the other.

Another little side note, the absolute dead center of your axle (or any rotating part) doesn't actually rotate.

Bryce
 

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FreezerJeep said:
Another little side note, the absolute dead center of your axle (or any rotating part) doesn't actually rotate.

Bryce
Any "spinning" part (where axis of rotation passes through the object). Some "rotating" parts have the point of rotation outside of the body (think orbital mechanics)... Ok, enough deep thought for today
 

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I don't think u would have these issues as the sensors are not at the outer diameter of the tire. Your abs sensors are all reading at the same distance away from the centerline of your axle. With different sized tires, the rpm at which they turn would be the same no matter what the difference is in diameter. Your surface speed is what changes though as this is affected by the circumference.

So as long as all the sensors are set at the same distance away from the centerline of the axles, and are not mounted at the very outside diameter of the wheel, then you should be fine.

The other option is to air down the 3 larger tires as much as safely possible to get your vehicle to sit more level. This will just help with road manners so the jeep does not want to pull one way or the other.

Another little side note, the absolute dead center of your axle (or any rotating part) doesn't actually rotate.

Bryce
I think your logic here might be missing something. I calculate the difference between a 32 and 28 inch tire at 60 miles an hour would be .5 revolutions per second or 24 revolutions per minute. where the sensors are mounted does not matter, its about total tire circumference. I would say it seems likely that this would affect the ESP in some way or another, just how much is the question. That being said I would likely run the same setup for several reasons, the main one being that I have never used my spare.

Frogy
 

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The question really is, how much faster does one wheel need to be turning than the other three to cause the computer to attempt to correct something? I would think it allows a pretty significant difference, say 15%? The limited slip rear axle will allow a pretty big difference it seems, that's how it lets you go around a corner without issue, same corner issue for the electronic systems.

I would venture a guess that a 32" spare on a vehicle where the other tires are 35" might drive just fine.
 

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Sounds like you have a lot of theoretical knowledge maskman....have you tried it?... ;)
Not on a Jeep, but I had an Acura where the ESC went nuts when riding on a space-saver spare. Similar application I would think. Once the system was disabled there was no more drama.
 

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I think your logic here might be missing something. I calculate the difference between a 32 and 28 inch tire at 60 miles an hour would be .5 revolutions per second or 24 revolutions per minute. where the sensors are mounted does not matter, its about total tire circumference. I would say it seems likely that this would affect the ESP in some way or another, just how much is the question. That being said I would likely run the same setup for several reasons, the main one being that I have never used my spare.

Frogy
What he said ^^^

There are quite a number of sensors for the ESP system.

Wheel Sensors are mounted at the wheels and are designed to pick up minor speed differences at each wheel, other sensors steering angle and yaw-rate.

Even a small change in the wheel speed can cause the computer to think there is slippage. I do not know how sensitive the Jeeps calibration is so I cannot speak to how much that difference would need to be. The yaw-rate would also be really messed up with a large difference of that theoretical 15% posted above.

Best thing to do if you have this problem is to Fully Disable (not just the switch in the Jeep) ESP and make sure you put the tire on a non-locked or LSD axle.

I am not saying that you cannot do this, I am just saying that it is advisable not to do so. I know people who have driven on donuts spares on the rear for a week and burned up their diff or tranny.
 

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I don't think u would have these issues as the sensors are not at the outer diameter of the tire. Your abs sensors are all reading at the same distance away from the centerline of your axle. With different sized tires, the rpm at which they turn would be the same no matter what the difference is in diameter. Your surface speed is what changes though as this is affected by the circumference.


Bryce
So, explain to me why a different sized tire would not spin at a different RPM, when the outside circumference is larger/smaller than the other tires?

This is why Mars landers end up missing the whole planet...
 

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Cheap. How could you spend that much and not spend a little more to getting the matching 5th? It looks soooooo stupid. If you can't afford all 5 save more. It must be my OCD, but man that's stupid and annoying looking....
 
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