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AWD systems and donut spare #5398321 04/09/20 11:06 AM
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Drew99GT Offline OP
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Ive been researching the topic at hand, and most manufacturers recommend removing a good full size tire from the back and putting it up front if you get a flat on any of the front tires. Subaru even makes you put a special fuse in to disable the AWD system.

I read that some Chrysler vehicle computers have an algorithm that can sense when the donut spare is installed and it disables the AWD system so nothing gets damaged.

My question, does anyone know for certain whether most modern cars will do this by disabling the AWD system when the donut spare is installed? Specifically Mazda?

Thanks!

Re: AWD systems and donut spare [Re: Drew99GT] #5398372 04/09/20 11:55 AM
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UG_Passat Offline
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Do most manufacturers that recommend you to put the good spare up front give you 2 jacks?

What does your owner's manual say?

What's the rolling circumference of your spare vs actual tire?

Mine, 235/50r18 vs 145/80r18, the spare is only 0.4% smaller circumference

Last edited by UG_Passat; 04/09/20 12:11 PM.

2016 VW Tiguan|APR Stage 1|Neuspeed P-Flo|Osram CBI|Redline 5w30
Re: AWD systems and donut spare [Re: Drew99GT] #5398386 04/09/20 12:09 PM
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Drew99GT Offline OP
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Just one jack; if you have a flat in the front, you first jack up a rear, remove a good tire and install the donut spare, then put the jack under the flat, remove it and install the good full size you took off the rear! Seems like a PITA to do on the side of the road...

Re: AWD systems and donut spare [Re: Drew99GT] #5398415 04/09/20 12:34 PM
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wog Offline
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Buy full size spare,is this an option?

Re: AWD systems and donut spare [Re: wog] #5398451 04/09/20 01:17 PM
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slacktide_bitog Offline
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Originally Posted by wog
Buy full size spare,is this an option?


approved

This is what I do for every car with a stupid donut, AWD or not thumbsup

Re: AWD systems and donut spare [Re: Drew99GT] #5398455 04/09/20 01:27 PM
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Wolf359 Online Content
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I think that depends on the split for the AWD system. Mercedes is set up the other way, most of the power is to the rear not front and it's full time, doesn't shut off. Standard advice has always been to put the spare on the non drive wheel so for FWD, the rear, for RWD, the front. For AWD I guess whichever wheel gets the least power. Although a donut on the front means you get less braking power.

Re: AWD systems and donut spare [Re: Drew99GT] #5398464 04/09/20 01:42 PM
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PimTac Offline
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For my 2017 CX5 it does not mention anything about the AWD. They are specific in requiring that the spare be installed on the rear wheel and that it be driven as few miles as possible.

It is a true spare. Estimated tread life is 3000 miles max. I believe it said to be used no more than 30 miles in any situation.


2017 Mazda CX5
Mobil 1 Annual Protection 0w20
Roki OEM filter.
Re: AWD systems and donut spare [Re: slacktide_bitog] #5398525 04/09/20 02:43 PM
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LoneRanger Offline
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Originally Posted by slacktide_bitog
Originally Posted by wog
Buy full size spare,is this an option?


approved

This is what I do for every car with a stupid donut, AWD or not thumbsup


That is what I did when I had my 2009 Subaru Forester. The well under the rear cargo floor plate was just large enough to accommodate a full size spare.

Re: AWD systems and donut spare [Re: Drew99GT] #5398551 04/09/20 03:17 PM
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IMSA_Racing_Fan Offline
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Sounds like you would need to have a NASCAR pit crew riding in the back like in those commercials.

Last edited by IMSA_Racing_Fan; 04/09/20 03:18 PM.

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1997 Ford Aspire
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Re: AWD systems and donut spare [Re: IMSA_Racing_Fan] #5398577 04/09/20 03:46 PM
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Wolf359 Online Content
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Originally Posted by IMSA_Racing_Fan
Sounds like you would need to have a NASCAR pit crew riding in the back like in those commercials.


That's why I have my Milwaukee 2767-20 just in case, 1400 foot pounds of torque in reverse. A full won't fit in the space in the trunk. Plus a full size tire for my car is around $200 so somewhat overkill. Although I've had flats, most of them were nails that couldn't be repaired but I didn't have to use the donut.

Re: AWD systems and donut spare [Re: Wolf359] #5398586 04/09/20 04:07 PM
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Unrepairable nail punctures? I've been repairing them forever with fiber plugs and rubber cement.


2012 Cadillac CTS 3.0
1997 Ford Aspire
1991 Jaguar XJ6
1986 Kawasaki ZG1000 Concours
Re: AWD systems and donut spare [Re: Drew99GT] #5398679 04/09/20 05:56 PM
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Kawiguy454 Offline
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get yourself a 12 volt compressor and a Plugger kit and you'll never need to change to spare unless it explodes. I have a version of this in 2 cars and 2 motorcycles https://www.amazon.com/dp/B0018EUDHW/ref=psdc_15709141_t1_B0006NE3KE. 5 minutes and youre on your way ...get a tire guy to change it later.

Last edited by Kawiguy454; 04/09/20 05:56 PM.
Re: AWD systems and donut spare [Re: IMSA_Racing_Fan] #5398732 04/09/20 07:18 PM
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Wolf359 Online Content
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Originally Posted by IMSA_Racing_Fan
Unrepairable nail punctures? I've been repairing them forever with fiber plugs and rubber cement.


Yeah, you know how it goes, nail puncture in the outer rib. No chain tire store would fix it. Would be a coin flip as to whether it'd be worth plugging. Didn't feel like gambling that much so just got a new tire. I drive fast sometimes....

Re: AWD systems and donut spare [Re: LoneRanger] #5398748 04/09/20 07:48 PM
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Gasbuggy Offline
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Originally Posted by LoneRanger
Originally Posted by slacktide_bitog
Originally Posted by wog
Buy full size spare,is this an option?


approved

This is what I do for every car with a stupid donut, AWD or not thumbsup


That is what I did when I had my 2009 Subaru Forester. The well under the rear cargo floor plate was just large enough to accommodate a full size spare.



It doesn't really solve the problem, if the tire wear isn't reasonably close you create the same problem as running the spare not having the same diameter. Then you factor in variances between different brand tire diameters...


Cadillac CTS-V 6.2L 10w30PP
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Re: AWD systems and donut spare [Re: Drew99GT] #5399090 04/10/20 08:52 AM
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Drew99GT Offline OP
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I got my situation figured out! Mazda specifically used a 155/90 R18 on AWD CX-7s, and that tire is listed as a specific tire for the CX-5, but in the US we got the tiny donut instead.

https://www.mazdas247.com/forum/index.php?threads/2017-spare-tire-mod-for-u-s.123861462/page-2

So I found a CX-7 spare wheel and tire on Ebay for 60 bucks. Its the exact same diameter as the regular wheels and tires. It fits in the spare tire well perfectly! So no more worrying about whether I'll cook the AWD system if I get stranded with a flat. I tried putting a regular wheel and tire in the spare tire well; way too tall.


Last edited by Drew99GT; 04/10/20 09:12 AM.
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