Jump to content

Spare tire size


Dr Fildo

Recommended Posts

I recently had a flat tire. First flat with this car. I have a 2008 AWD edge with 20" rims. I like that the spare is in the cargo area, but I was surprised to see that spare tire/donut is 17".

 

I was under the impression that with AWD it was important to run all 4 wheels with the same tire size. The spare tire area is big enough to store the full size tire in there when the spare is on the car, so why wouldn't they supply a 20" spare on all vehicles with the 20"rim/tire?

 

I bought the car used, so maybe the dealer switched the spare??

 

Has anyone else run into this issue?? Is the 17" spare standard on an AWD with 20" rims? Or is it no big deal to run a smaller spare tire?

Link to comment
Share on other sites

  • 3 months later...
  • 1 month later...
  • 4 months later...

You got me curious enough that I just checked the spare tire in my 2013 Limited. I purchased it new with the 20" wheel and tire option, and know that the spare has never been exchanged or even taken out of the vehicle. BIG DIFFERENCE between the two sizes used as shown!

NOTE- I have a FWD model, not an AWD. Don't know if those spare sizes would be different.

 

Factory tire size is 245 50 20

Spare tire size is 165 80 17

 

The first number is the factory 20 inch tire, the second number is the factory 17 inch spare tire as shown on a tire size calculator site.

 

Tire diameter
29.6 inch
27.4 inch
Sidewall height
4.8 inch
5.2 inch
Rolling circum.
93.1 inch
86.1 inch
Revs/Mile
680
736
Ride height difference
-1.13 inch
Rolling circumference difference
-7.6 %
Speedometer difference
+8.2 %
Speedometer reading at 60 mp/h
64.9 mp/h
  • Like 2
Link to comment
Share on other sites

If AWD is disabled during this time, or there is enough tolerance built into the PTU to handle it, I can see that happening. If AWD is NOT disengaged, however, and the PTU is marginal, I wonder if it would still be safe.

 

Why would Ford sell it that way if it wasn't safe? That's my point. It came that way from the factory.

Link to comment
Share on other sites

  • 1 month later...

I have a 2009 Ford Edge with the 20" wheels. Had a flat tire due to a cracked rim. Spare was installed @ tire shop,and I was directed to a place to have my wheel repaired. I made it about a quarter of a mile down the road when my car began to violently pull, jerk, grind, and clunk. I pulled over quickly wondering if my wheel had come off the car or something.(??) At this point car was un drivable in drive or reverse without doing the same. Long story short,wheel was repaired,reinstalled on the vehicle,and it was back to normal. Although I wondered ever since how much damage was done before I was able to stop the car. I have since had some intermittent clunks, until this week all of a sudden I'm getting a whining,grinding sound coming from the all wheel drive unit (verified by a very reputable auto repair facility in my area).. the spare is about 7 inches smaller in diameter as was pointed out earlier in the comments. I checked with the dealer to make sure this was the original spare size that Ford Motor Co. provided with this vehicle since I bought it used (and It is). Bottum line, I need some expensive repairs on this vehicle because of this issue. If there is supposed to be some sort of override to disengage the AWD while using the (obviously dangerously undersized) spare tire, IT DIDN'T WORK! Who do I even begin to complain to?

Link to comment
Share on other sites

Sounds like the PTU was already on the way out when the first incident happened, probably due to overheating due to low fluid level. No resort that I know of ... so far ... but to fix at your own expense. Could be a coincidence that it happened with the spare tire (meant for limited range driving, but sounds like you were WELL under), maybe not.

 

Try calling Ford National Customer Service, or if that doesn't work out, Lincoln Customer Service. I hope our Ford rep on here (Tricia) will see your post soon and step in with advice.

 

BTW, the difference is about 3" in height, I believe between the stock wheel and the spare:

http://www.tacomaworld.com/forum/tirecalc.php?tires=245-50r20-165-80r17

 

which is still way above the difference the AWD can compensate for.

 

Interesting tidbit I was unaware of (OM):

"You should replace your spare tire when you replace the road tires or after six years due to aging even if it has not been used."

 

"If your vehicle is equipped with AWD, a spare tire of a different size
other than the tire provided should never be used. A dissimilar spare tire
size (other than the spare tire provided) or major dissimilar tire sizes
between the front and rear axles could cause the AWD system to stop
functioning and default to front wheel drive and could damage the
system."

 

"Each tire, including the spare (if provided), should be checked
monthly when cold and inflated to the inflation pressure recommended
by the vehicle manufacturer on the vehicle placard or tire inflation

pressure label. (If your vehicle has tires of a different size than the size

indicated on the vehicle placard or tire inflation pressure label, you

should determine the proper tire inflation pressure for those tires.)"

Edited by WWWPerfA_ZN0W
Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...
×
×
  • Create New...