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Hello I apologize if this has been answered but I could not locate exactly what I am looking for. I am trying to purchase a basic steel wheel for a full size spare. I know 18x7.5 and the lug patterns have to match but I am a bit lost when it comes to offset etc. Has anyone found a good alternative to buying a 5th oem full size wheel?
 

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You should find a 55mm offset rim, and the same Falken tire.

I bought 5 aftermarket rims, and five identical tires.

Also, remember, if your road tires wear more than 2/3" then you need to have your full sized spare shaved down very shortly after you put it on.
 

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Just to be clear, are you looking for a full size spare hoping you can drive on it longer than the factory spare? Unless added into your tire rotation, you'll still have to worry about variance in tread depth and your drivetrain.
 
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Here's the full tire specs, both for your 18" OEM setup, and for the 20" OEM setup for anyone else following along:



18"
Tire size:
245/60R18 105H @ 35psi
--- Rated at 2039 pounds
Wheel size: 18 x 7½ J
Inset: 55mm (2.17)
P.C.D. (bolt pattern): 114.3 (4.5) by 5
682 revolutions per mile


20"
Tire size:
245/50R20 102H @ 33psi
--- Rated at 1874 pounds
Wheel size: 20 x 7½ J
Inset: 55mm (2.17)
P.C.D. (bolt pattern): 114.3 (4.5) by 5
681 revolutions per mile

Tires are load rated based off GAWR-R and a safety factor. ALL OEM regular use tires (in other words, NOT the limited use spare) are speed rated at 130 mph. The Ascent is governor limited to 130 mph (max speed noted by one owner is 129 mph - do not attempt except in the proper environment, such as at a track).

ALL TRIMS:
  • GAWR-R: 3,296 pounds
  • GAWR-F: 3,021 pounds
 

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I understand that all tires including the spare needs to be the same circumference and I understand that as tires wear the circ. changes, but I doubt if anyone gets the OE temporary tire shaved (if you even could) as their regular tires wear. So, is it really necessary to do so for a full size matching spare, if it would only be used as long as needed to get to a tire shop and have the flat fixed or replaced (and shaved if needed)? Is the limited use of the OE temporary because of possible differences in circumference due to wear of the regular tires or because of durability/ratings of the OE temporary tire? Or both?

I am asking because I think I want to carry a matching full size spare to use if needed while towing a trailer, but I do not want to mount it on a more expensive matching rim, have a TPMS sensor in it, and include it in the tire rotation. But maybe I am thinking wrong, and this is not the best way to go.

If you have a full size matching rim and spare that is included in a 5 tire rotation, how is the TMPS sensor handle? The Ascent's TMPS cannot store more than 4 sensor IDs. Does the Ascent auto relearn sensor location? Any idea what the shop cost will be to have a 5 tire rotation with sensor programing/relearning done each time?
 

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I understand that all tires including the spare needs to be the same circumference and I understand that as tires wear the circ. changes, but I doubt if anyone gets the OE temporary tire shaved (if you even could) as their regular tires wear. So, is it really necessary to do so for a full size matching spare, if it would only be used as long as needed to get to a tire shop and have the flat fixed or replaced (and shaved if needed)? Is the limited use of the OE temporary because of possible differences in circumference due to wear of the regular tires or because of durability/ratings of the OE temporary tire? Or both?

I am asking because I think I want to carry a matching full size spare to use if needed while towing a trailer, but I do not want to mount it on a more expensive matching rim, have a TPMS sensor in it, and include it in the tire rotation. But maybe I am thinking wrong, and this is not the best way to go.

If you have a full size matching rim and spare that is included in a 5 tire rotation, how is the TMPS sensor handle? The Ascent's TMPS cannot store more than 4 sensor IDs. Does the Ascent auto relearn sensor location? Any idea what the shop cost will be to have a 5 tire rotation with sensor programing/relearning done each time?
I run a full sized spare when I run my all terrains (and I am running those all except my upcoming track weekend in September). Before I go on my nearly 9,000 mile road trip this August (it's growing still, lol), I plan on getting my full sized all terrain shaved.

As for the fifth sensor, I honestly have no idea, but am very curious. It's installed in my full sized spare, but never been tested or used. I will let you know.

As for the donut compared to stock, the stock tires don't have thick tread, and neither does the donut, so, it's near impossible to get beyond the 2/3" tire size difference that's problematic for a Subaru AWD.

In MY case, my all terrains have some beastly tread (well, more so 24,000 miles ago, but still quite a lot), so, for me, it's important, and I likely couldn't run the donut, hence my full time spare. Additionally, because I off road and such, I needed a full spare anyway.

Regardless, the donut is limited use anyway. It's intended for low speed driving (50mph or less, which none of us do on the highways except for in the event of traffic) and limited travel (to a tire shop). So, even then, it's different.

The suggestion I see repeatedly, over the years, has been if one is using a full sized spare (such as mine), or needs to replace a tire, to have it shaved to match, or to replace all four to match. Overheating a differential will eventually burn it out. "Eventually" is of course quite a variable time frame depending on a lot of factors, so, I've chosen to not take a chance, because, the criteria is so variable (eg: 3/4" size difference with 2-3 trips a month to the grocery store half a mile away maybe won't toast anything, but a little over 2/3" difference at 80mph (yay, hitting 80mph zones!!!) on my massive road trip may end up costing me a differential.

I've seen it happen (burning out a diff because of mismatched tires), so, I do what I do, and recommend what the tire experts recommend. But, again, with the very small tread on both the spare and the stock tires, I am not sure it's possible to have such a difference in size, even after wearing down the stock tires.

Hmmm....
 

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Using the stock spare while towing: The manual for the Ascent makes a couple of statements about the OE temporary spare that I do not understand and which makes me wonder if they even apply to the spare in the Ascent.

1) "The temporary spare is not designed to sustain the towing load." The regular stock tires have a Load index 105 = 2039lbs. The spare has a Load Index 107 = 2149lb. If properly inflated why could the spare not handle the load?

2) "Do not drive over obstacles. "This tire (spare) has a smaller diameter, so road clearance is reduced." Is that true? The diameter of the regular tire is 29.6". The diameter for the Falken spare is 29.7". Considering the AWD system, a new OE temporary spare and new OE regular tires should have the same dia./circumference.

I understand that towing or not, you should get the temporary spare replaced with a standard tire as soon as possible, and you must limit you speed and drive cautiously especially when cornering. But should you really not use the Ascent's temporary spare at all while towing?
 

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But should you really not use the Ascent's temporary spare at all while towing?
Yes, you should not do that. It's just about vertical load, but about a bunch of other things that get stressed. There's a reason that these compact/temp spares are so, um...spare...and for the warnings around speed, etc., when using them. Some other vehicles actually replace the "donuts" with a "full size" spare when you order a factory towing option. Grand Cherokee is like that, for example. A "full size" spare will have the same diameter and full duty cycle as the tires on the four corners. It may be narrower in some cases (like with the JGC) so it's easier to store, but it is otherwise a normal, road-worthy tire that can support the load, at speed and with equivalency of the regular tires.

So if you're towing and only have the compact spare, if you have a flat, you'll want to get off the road, drop the trailer, install the spare, drive to where you can get your tire fixed and then return to pick up your trailer to continue if you want to be sure of safety.
 
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Jim_in_PA - Agree, and that is why I now carry an OE tire and rim in place of the temporary spare. There is no way that I want to leave my camper sitting besides the road especially along the back-roads and FSRs I often travel.
 

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desmog - what type of tires do you have on your Ascent? Is the avatar pic your car?
Continental TerrainContact A/T 245/60 18 - I now have around 4,000 miles on them and they have been great. I like the way the car handles and I have not noticed any reduction in gas mileage or distrubing road noise. Most of the miles are towing a trailer. I have only been off pavement on forest service roads (rough gravel/dirt) and wet sand/mud roads, but tires were fine.
 

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Hello all,

I've ALWAYS replaced the spare with a full size tire in all my cars. Does anyone have a photo of how much a full size tire protrudes in the spare tire well?
 
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