Difference between daily tires and spare?

[Bamsi]

I have read many time in different threads in this forum about maximum tire size. So far I have not read about different size between daily tires and spare, being our BSs AWD. What is the tolerance in size differences among those tires? Can I use my 225 65 17 Pirellis with my 235 70 17 Coopers or 245 65 17 Wildpeaks? Would it damage my vehicle? How far I can go until damage tire repaired or changes? Can anyone shed science over this matter? Any person? Ford? Falken? Tire Direct?

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[gatornek]

Haha. That’s so funny. Just had a side conversation with some forum members about this very thing.

Super interested to see the responses.

 

[Art4All]

I have read many time in different threads in this forum about maximum tire size. So far I have not read about different size between daily tires and spare, being our BSs AWD. What is the tolerance in size differences among those tires? Can I use my 225 65 17 Pirellis with my 235 70 17 Coopers or 245 65 17 Wildpeaks? Would it damage my vehicle? How far I can go until damage tire repaired or changes? Can anyone shed science over this matter? Any person? Ford? Falken? Tire Direct?

I would like to know the answer to this, too! @Discount Tire

 

[Mark S.]

Discount tire is not the best source for this info. Your owner's manual has a section on "dissimilar size spare" tires which has all the info you need. You can use one, but it should be temporary (long enough to drive to the shop and have your damaged tire repaired), and the computer may disable the 4WD system until you put the right size tire back on.

 

[jkeaton]

Discount tire is not the best source for this info. Your owner's manual has a section on "dissimilar size spare" tires which has all the info you need. You can use one, but it should be temporary (long enough to drive to the shop and have your damaged tire repaired), and the computer may disable the 4WD system until you put the right size tire back on.

Sensibility has entered the chat.

 

[magicbus]

Speaking as someone who recently retired from 40 years of designing and writing all manner of software, I would suggest that the computer that controls the clutches that control your BS can easily accommodate and compensate for these size differences.

Trust the force Luke… oops sorry, Bamsi.

 

[Bamsi]

Haha. That’s so funny. Just had a side conversation with some forum members about this very thing.

Super interested to see the responses.

Me too!

 

[Bamsi]

Thank Obi Wan Magicbus...

 

[Mark S.]

I would suggest that the computer that controls the clutches that control your BS can easily accommodate and compensate for these size differences.

It can, primarily by disabling the 4WD system. In the section of your owner's manual under the heading Information Displays you'll see "4WD Off" as one of the possible messages you might see. This means:

The four-wheel drive system temporarily turns off to protect itself from overheating or if you are using the temporary spare tire.

The manual cautions that dissimilar tire use should be TEMPORARY, so I would prioritize a shop visit for repair if I were driving on a dissimilar size spare.

 

[Colonel Angus]

Sensibility has entered the chat.

I always respect a man that reads his owners manual.

 

[Bamsi]

It can, primarily by disabling the 4WD system. In the section of your owner's manual under the heading Information Displays you'll see "4WD Off" as one of the possible messages you might see. This means:


The manual cautions that dissimilar tire use should be TEMPORARY, so I would prioritize a shop visit for repair if I were driving on a dissimilar size spare.

Thanks Mark!

 

[PugDad]

Discount tire is not the best source for this info. Your owner's manual has a section on "dissimilar size spare" tires which has all the info you need. You can use one, but it should be temporary (long enough to drive to the shop and have your damaged tire repaired), and the computer may disable the 4WD system until you put the right size tire back on.

Owners manual…..2.0 ….Mark S.

 

[PugDad]

I always respect a man that reads his owners manual.

What do mean reads it??? He wrote it!

 

[Robink]

So if I'm understanding this correctly then if I'm somewhere that I'm having to use 4wd and I get a flat and change it it will disable 4wd?? I replaced the donut on my BB for a full size tire and wheel. I put one of the original street tires that was on it when I bought it to the spare. And I put 225 65 17 Toyo tire's on it. The spare is the same size. Will I have trouble with 4wd then?

 

[Mark S.]

So if I'm understanding this correctly then if I'm somewhere that I'm having to use 4wd and I get a flat and change it it will disable 4wd?? I replaced the donut on my BB for a full size tire and wheel. I put one of the original street tires that was on it when I bought it to the spare. And I put 225 65 17 Toyo tire's on it. The spare is the same size. Will I have trouble with 4wd then?

The manual isn't clear about the details regarding when the system disables 4WD. I assume it would be almost immediate if you are using a donut, but any significant difference in overall circumference will likely have the same result eventually.

The 4WD system uses sensors to compare speeds for all four wheels. When one or more spin at a different speed from the rest clutches engage in the power transfer unit (PTU) to divide power between front and rear. A persistent speed difference, such as would occur with one tire of significantly different circumference, would keep the PTU clutches locked up all the time. The PTU in non-Badlands models is air-cooled, and therefore not designed for full-time operation. It would quickly overheat due to the constant friction on the clutches, causing premature wear. That's why the system disables itself if it senses a persistent difference in speed between the four wheels.

If your spare tire is the same circumference as the rest of your tires you should be fine.

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