Auto Authority Spare Tire Kit

[22GBMach1]

Just checking if anyone has recently ordered a spare tire kit from Automotive Authority for their Mach 1. I just received the kit and it came with a 155/60/R20 tire. Using a 20" spare tire with 19" stock wheels just does not seem to be the best option. This is my first Mustang. Previous muscle or sport cars I have bought spare tires for have been the same wheel size as the stock wheels. I checked back with AA ref. the 20" spare and they responded with the following.

"Thanks for providing these. Your front tires have a rolling diameter of 26.2" and the rear is 26.4" compared to our 27.3" rolling diameter. These are 4% and 3.3% difference in rolling diameter respectively which is well within specifications. It will not harm your Torsen differential at all. We used to offer the 135/70R19 Kumho or our 155/70R19 Tri-Ace before we switched over to our second generation 20" spare with the 155/60R20 tire. The 135/70R19 Kumho tire did not provide a high enough speed tire or tread life that we were looking for. Our custom made 155/70R19 tire has a 99 MPH rating and a 30,000 mile tread life which is what we want to offer, however it has a 27.5" rolling diameter and some customers had trouble getting it to fit into their wheel well. The 155/60R20 tire provides the same 99 MPH rating and tread life as our 155/70R19 but it has a slightly smaller 27.3" rolling diameter which makes it easier to fit in the trunk wheel well. We made the switch over to the second generation 20" wheel for the Mach 1 models a couple of months back. The Mach 1 models also can come equipped with different tire sizes from Ford based on your package. The 155/60R20 lands right in the middle of both of these sizes."

The one inch difference in rolling diameter seems significant. Is AA correct and the 20" spare will work and not damage any driveline components or cause limp mode activation etc..?

The 20" spare tire/wheel does fit inside the wheel well.

Thanks and look forward to your responses.

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[Charlemagne]

It's fine, you won't have any issue with 155/60 R20. Be glad for an upgrade. Though spare tire speed or life is not something I would consider as priority

https://tiresize.com/tyre-size-calculator/

+1.1% / -1.4% diameter difference to standard 255/40 and 275/40 R19
+4.2% / +3.4% diameter difference to HP 305/30 and 315/30 R19

The max recommended difference for normal driving is 2.5-3% but this is not normal driving and people have been using more than 3% as well too. It'll work fine and there won't be any damage to the differential.

 

[cerbomark]

I have the AA spare too. I assume it s the 20 which doesn t matter. it s the overall diameter and this seems to be within the specs. Now you can drive with some peace of mind. Driving my other car last week 800 miles from home at 4am and had a bolt go thru the tire. Thank God for the spare. The self sealer would not have done a thing. I have had a few Porsche s and they don't have spares and I hated that. They also didn t have the room for one, LOL.

 

[22GBMach1]

Thanks so much Charlemagne.

 

[22GBMach1]

Thanks cerbomark. In the past, I also have needed a spare where the manufacturer provided the gooey inflator setup but the stock tire was beyond repair.

 

[cerbomark]

don t forget the jack!!

 

[22GBMach1]

Yep!

 

[Weeee]

What are folks using for a scissor jack that fits into the space compartment? I've heard of the toro big red mentioned.

 

[cerbomark]

AA jack that can be ordered with spare. I didn t overthink it.

 

[19gtaz]

I bought the 155/70/19 spare right before they changed it to a 20. It is a very tight fit in the trunk wheel well. I kind of wish I would have gotten the 155/60/20.

 

[cerbomark]

so I bought mine in aug/22... lol, not sure what size I got. it did fit in well.
.2 difference in the 19 and 20.

 

[TrackMeisterWannabe]

I am opting for a different jack than what AA offers. They could not confirm fitment with my Steeda Jacking Rails. A quick search on Amazon shows many alternatives at lower prices that look like they will fit better with rails than the top of the AA scissor jack. Lifting capacities are higher on many models as well.

 

[murick]

I am opting for a different jack than what AA offers. They could not confirm fitment with my Steeda Jacking Rails.

I am not sure any scissor jack will fit with the rails (unless you have an adapter, the rails are about two inch wide and flat).

Thing is that the scissor jack AA sells with the spare have some funny "head" (https://www.mustang6g.com/forums/threads/spare-tire-kit-for-brembo-brake-stangs.183855/post-3703098), which I have no idea how to match properly to the car . I asked AA and their replay was that the jack is an exact same as the Ford OEM (which Ford no longer gives) - which seems true, the Ford OEM jack has the same head, but everyone I showed it to, was clueless as I .

I believe the best would be jack with rubber insert with a split you could put on the pinching weld without any worry.

 

[Oakley]

i got the kit for my PP1. had to use a hockey puck and fab a better tie down bolt but the wheel and jack are good. i also carry the goo machine/compressor, and plugs so this is like a third line of defense that I hopefully will never need.

 

[IanKar]

Just checking if anyone has recently ordered a spare tire kit from Automotive Authority for their Mach 1. I just received the kit and it came with a 155/60/R20 tire. Using a 20" spare tire with 19" stock wheels just does not seem to be the best option. This is my first Mustang. Previous muscle or sport cars I have bought spare tires for have been the same wheel size as the stock wheels. I checked back with AA ref. the 20" spare and they responded with the following.

"Thanks for providing these. Your front tires have a rolling diameter of 26.2" and the rear is 26.4" compared to our 27.3" rolling diameter. These are 4% and 3.3% difference in rolling diameter respectively which is well within specifications. It will not harm your Torsen differential at all. We used to offer the 135/70R19 Kumho or our 155/70R19 Tri-Ace before we switched over to our second generation 20" spare with the 155/60R20 tire. The 135/70R19 Kumho tire did not provide a high enough speed tire or tread life that we were looking for. Our custom made 155/70R19 tire has a 99 MPH rating and a 30,000 mile tread life which is what we want to offer, however it has a 27.5" rolling diameter and some customers had trouble getting it to fit into their wheel well. The 155/60R20 tire provides the same 99 MPH rating and tread life as our 155/70R19 but it has a slightly smaller 27.3" rolling diameter which makes it easier to fit in the trunk wheel well. We made the switch over to the second generation 20" wheel for the Mach 1 models a couple of months back. The Mach 1 models also can come equipped with different tire sizes from Ford based on your package. The 155/60R20 lands right in the middle of both of these sizes."

The one inch difference in rolling diameter seems significant. Is AA correct and the 20" spare will work and not damage any driveline components or cause limp mode activation etc..?

The 20" spare tire/wheel does fit inside the wheel well.

Thanks and look forward to your responses.

Even though I have not driven with it, I checked fit especially over the front brakes as the Ford OEM spare wheel they said would fit, did not. So my AA spare fits okay and outside diameter works out fine as Nick said.

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