Using old spare

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Using old spare

Postby lalojamesliz1 » Sun Jun 09, 2019 9:53 pm

I've been wanting to take out my spare tire to reduce my all-trac's weight since I only use it in town (mainly to and from work) and it weighs 46lbs. I took it out to air it up and just inspect it and I forgot how old it is.
It's a Michelin mxv2 and the date code after the DOT is 402.... that's April of 2002!? Am I correct?
It doesn't show any cracks and I only have it at 20psi now. The size is 215/50 R15 and the tires on my all-trac are 225/50 R16. Can that size difference damage one of the differentials on my all-trac.
My current tires are in great shape and I've had them on for a little over a year so I'm not worried about them. Plus I have towing now. I still don't want to have to use it though. What would you guys do?
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Re: Using old spare

Postby underscore » Sun Jun 09, 2019 10:20 pm

I think the date code system changed at one point but that sounds like a very old tire either way. Like you I have towing support so the only reason I left my spare in is for if I somehow damage the tire enough that driving it onto the trailer would damage the rim. Other than that there isn't much use to it since if I get a flat I'll either trailer it home or swap all 4 wheels.
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Re: Using old spare

Postby lalojamesliz1 » Sun Jun 09, 2019 10:49 pm

underscore wrote:I think the date code system changed at one point but that sounds like a very old tire either way. Like you I have towing support so the only reason I left my spare in is for if I somehow damage the tire enough that driving it onto the trailer would damage the rim. Other than that there isn't much use to it since if I get a flat I'll either trailer it home or swap all 4 wheels.


I see what you mean. Like if I hit a curb and broke a wheel/blew a tire..... I'll just leave it in and keep it at 20-25 psi.
My all-trac is fun to drive but sometimes I forget it's no race car, IT'S A F-ING RALLY CAR 8) :P Thanks man
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Re: Using old spare

Postby FC Zach » Mon Jun 10, 2019 12:31 am

lalojamesliz1 wrote:The size is 215/50 R15 and the tires on my all-trac are 225/50 R16. Can that size difference damage one of the differentials on my all-trac.


That's ~6% difference, which is a lot! Over an inch in diameter. Anything that far from matching isn't good in my opinion. If you get a new spare tire, I'd get one close to what you're using.
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Re: Using old spare

Postby 93celicaconv » Mon Jun 10, 2019 1:26 am

The full size spares on our two 1990 All-Tracs are Bridgestone Potenza P215/50R15, as well as the full size spare on our 1992 GT-S. Given yours is a Michelin, I suspect yours is not the original spare, but it is an original size spare. The OD of a P215/50R15 tire is 23.46".

Your current P225/50R16 tires have an OD of 24.84".

Generally speaking, on an AWD with viscous coupling, tires of the same brand & size specification and same air pressure should not exceed a tread depth difference greater than 2/32" (or 1/8" diameter). That is the key reason Toyota put full size spares on the ST185's instead of the industry-standard TEMPORARY spare. Tires of the same size will have variation in diameters greater than this, so mixing different brands of tires of the same size is not wise. Same with having two new tires and two tires 50% worn at the same time.

Do as you will. Just be aware of the guidance.
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Re: Using old spare

Postby lalojamesliz1 » Mon Jun 10, 2019 1:31 am

93celicaconv wrote:The full size spares on our two 1990 All-Tracs are Bridgestone Potenza P215/50R15, as well as the full size spare on our 1992 GT-S. Given yours is a Michelin, I suspect yours is not the original spare, but it is an original size spare. The OD of a P215/50R15 tire is 23.46".

Your current P225/50R16 tires have an OD of 24.84".

Generally speaking, on an AWD with viscous coupling, tires of the same brand & size specification and same air pressure should not exceed a tread depth difference greater than 2/32" (or 1/8" diameter). That is the key reason Toyota put full size spares on the ST185's instead of the industry-standard TEMPORARY spare. Tires of the same size will have variation in diameters greater than this, so mixing different brands of tires of the same size is not wise. Same with having two new tires and two tires 50% worn at the same time.

Do as you will. Just be aware of the guidance.

I'm here for the guidance.
Would a 215/60r15 tube be okay? I saw its .3" different in diameter than my 225/50r16. Or am I seeing it wrong?
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Re: Using old spare

Postby 93celicaconv » Mon Jun 10, 2019 4:25 pm

1/8" of diameter different is 0.125" diameter difference. So no, a 0.3" diameter difference is not OK on one of these Toyota AWD platforms. OK on a 2-wheel drive (best if the difference is not on the driving axle, but rather on the rolling axle).
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Re: Using old spare

Postby underscore » Mon Jun 10, 2019 9:38 pm

93celicaconv wrote:That is the key reason Toyota put full size spares on the ST185's instead of the industry-standard TEMPORARY spare.


My 184 came with a full sized spare and my 185 came with a temporary donut. I haven't tried but looking at the space I doubt it has the depth for a full size.
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Re: Using old spare

Postby alltrac801 » Mon Jun 10, 2019 10:14 pm

When I got my St185 it had a 205/50r15 and fit just fine.
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Re: Using old spare

Postby 93celicaconv » Tue Jun 11, 2019 12:53 am

underscore wrote:
93celicaconv wrote:That is the key reason Toyota put full size spares on the ST185's instead of the industry-standard TEMPORARY spare.


My 184 came with a full sized spare and my 185 came with a temporary donut. I haven't tried but looking at the space I doubt it has the depth for a full size.

According to my information, all hatchback models received full-size spares (ST184 & ST185). Are you the original owner of your ST185? If not, it is possible the PO substituted a TEMPORARY spare in on your ST185 to save weight. Good to save the weight - bad to use.
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Re: Using old spare

Postby underscore » Tue Jun 11, 2019 5:10 am

Definitely not, my 185 was originally sold in Japan while the 184 has always been in Canada. The anchor, cardboard piece and carpet all fit perfectly with the thin space saver though. Maybe they used different trimmings to fit a smaller spare for the Japanese market. At some point I will be storing a full sized spare in the trunk so I can see if it might fit nicely but since the donut is about half the width of a real tire I'm doubtful.
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Re: Using old spare

Postby 93celicaconv » Tue Jun 11, 2019 10:38 am

In looking at Toyodiy.com, I do see references to a temporary spare (size 135/70 D16) on some ST185's, so if that is what you have in your ST185 from Japan, then I stand corrected.

The 135/70 D16 tire has a 23.44" diameter (compared to 23.46" diameter for the original 215/50R15), so the diameter difference (0.02") is well within the acceptable range for the Toyota AWD platform. So Toyota ensured the temporary spares matched the OD of the original tires, which I would expect from them. Again, this is all guidance, you are the owner, you do what you feel you need to (and take the associated risk if what you choose is outside of this guidance).
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Re: Using old spare

Postby alltrac801 » Tue Jun 11, 2019 2:29 pm

underscore wrote:Definitely not, my 185 was originally sold in Japan while the 184 has always been in Canada. The anchor, cardboard piece and carpet all fit perfectly with the thin space saver though. Maybe they used different trimmings to fit a smaller spare for the Japanese market. At some point I will be storing a full sized spare in the trunk so I can see if it might fit nicely but since the donut is about half the width of a real tire I'm doubtful.


That's so interesting. So is your trunk carpet completely flat? My St185 has a hump in the carpet to fit the full size spare.
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Re: Using old spare

Postby underscore » Tue Jun 11, 2019 5:28 pm

It has a hump but it's fairly small. Using the sizes 93celicaconv has it's over 3" narrower than the original tire which is quite the difference considering how shallow the space is.
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Re: Using old spare

Postby alltrac801 » Tue Jun 11, 2019 6:44 pm

I've never looked at a GT4 on person or even another all-trac so I just would think they were different, so I find that very interesting. Guess I learn something new everyday!
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