Spare tire with WRX wheels?

thefultonhow · Post by **thefultonhow** » Wed Apr 05, 2006 12:56 am

I was talking to Gnuman on the IRC channel yesterday, and mentioned that I was going to get WRX wheels and then use my steelies as full-sized spares for long trips. He said that this would be a bad idea because the smaller diameter would cause torque bind. Is this true? If so, how far would I have to drive with a steelie on to cause torque bind?

Manarius · Post by **Manarius** » Wed Apr 05, 2006 2:01 am

It won't cause torque bind, but it will fry the center diff. Torque bind comes from aging 4EAT's.

555BCTurbo · Post by **555BCTurbo** » Wed Apr 05, 2006 2:19 am

Just make sure the overall diameter is the same (read: taller tire on the 15" rim)

206er · Post by **206er** » Wed Apr 05, 2006 2:33 am

a stock wheel/tire is a lot better than a space saver spare.
hmmm maybe I need to pick up a wheel/tire off craigslist. for some reason there is always someone selling one wheel.

thefultonhow · Post by **thefultonhow** » Wed Apr 05, 2006 2:59 am

555BCTurbo wrote:Just make sure the overall diameter is the same (read: taller tire on the 15" rim)

What if I run it with the stock tire size... torque bind? Or would I be okay for a hundred miles or so?

douglas vincent · Post by **douglas vincent** » Wed Apr 05, 2006 4:12 am

I picked up a spare wrx rim and tire for $50. Fits in the wagon wheelwell if nothing else is there.

Subtle · Post by **Subtle** » Wed Apr 05, 2006 5:31 am

If you are out in the boonies and had a tire failure I would sooner drive out on a more standard tire and rim.

What was the tire size on the 16-inch WRX rim

thefultonhow · Post by **thefultonhow** » Wed Apr 05, 2006 5:33 am

Subtle wrote:If you are out in the boonies and had a tire failure I would sooner drive out on a more standard tire and rim.

What was the tire size on the 16-inch WRX rim

Standard WRX size -- 205/55R16. Eventually I will replace them with 205/50R16 to be closer to the original circumference.

BAC5.2 · Post by **BAC5.2** » Wed Apr 05, 2006 3:25 pm

206er wrote:a stock wheel/tire is a lot better than a space saver spare.
hmmm maybe I need to pick up a wheel/tire off craigslist. for some reason there is always someone selling one wheel.

Why? The space-saver-spare is the same diameter as the stock wheel.

I use a WRX wheel with a stock RE92 (205/55/16) as the spare for my 17's.

thefultonhow · Post by **thefultonhow** » Wed Apr 05, 2006 4:04 pm

Phil -- what tire size is on your 17s?

BAC5.2 · Post by **BAC5.2** » Wed Apr 05, 2006 4:19 pm

225/45/17

thefultonhow · Post by **thefultonhow** » Wed Apr 05, 2006 4:27 pm

Oh... so the circumferance is pretty close. Darn.

How much would it cost to get a roughly matching spacesaver tire until I can get another WRX wheel?

BAC5.2 · Post by **BAC5.2** » Wed Apr 05, 2006 4:31 pm

Get a WRX space-saver and call it a day.

That's what I'd do.

thefultonhow · Post by **thefultonhow** » Wed Apr 05, 2006 5:02 pm

Hah! Didn't think of that. Thanks.

Post by **Legacy777** » Wed Apr 05, 2006 5:59 pm

Yeah, I picked up a WRX spare tire as well since the stock one wouldn't fit over any of the brakes.

thefultonhow · Post by **thefultonhow** » Tue Apr 18, 2006 6:50 pm

Ooooooookay.

So I got a WRX spare tire from a guy locally. It was never used -- he got a full-size spare and put the stock one in his garage. The sizing on the spare is 135/70-16.

Okay, fine, but I found a set of WRX wheels locally with almost-brand-new tires. They are Falken Ziex ZE-502, but in a completely non-standard size -- 205/40-16 (stock is 205/55-16). So I went to Miata.net and calculated the tire size differences between the stock size, the size of the tires on the wheels I may be getting, and the spacesaver spare. I wanted to know if I needed a new tire for the spacesaver to prevent torque bind.

The results were surprising:

Code: Select all

Specification  Sidewall  Radius  Diameter  Circumference  Revs/Mile  Difference
205/55-16         4.4in  12.4in    24.9in         78.2in        811        0.0%
135/70-16         3.7in  11.7in    23.4in         73.6in        860       -5.8%

Specification  Sidewall  Radius  Diameter  Circumference  Revs/Mile  Difference
205/40-16         3.2in  11.2in    22.5in         70.5in        898        0.0%
135/70-16         3.7in  11.7in    23.4in         73.6in        860        4.4%

Well that's weird. Subaru's OEM spacesaver for the WRX is a completely different size than the WRX wheels. Wouldn't that cause torque bind? My curiousity was piqued, to say the least. So I wondered whether our cars had different-sized spacesavers too. I went outside, opened up the hatch, and took a gander at the spare.

The size? 135/70-16! The exact same size as the WRX spacesaver! WTF mate?

Here's a calculation from Miata.net for the stock wheels and spacesaver:

Code: Select all

Specification  Sidewall  Radius  Diameter  Circumference  Revs/Mile  Difference
185/70-14         5.1in  12.1in    24.2in         76.0in        834        0.0%
135/70-16         3.7in  11.7in    23.4in         73.6in        860       -3.1%

So, does wheel diameter not matter for torque bind?

entirelyturbo · Post by **entirelyturbo** » Wed Apr 19, 2006 1:27 am

Torque bind doesn't happen on 5MT's, only on 4EAT's.

The 4EAT clutch pack will TRY to make the fronts and rears spin the same speed and get really mad when it realizes they can't, while the 5MT viscous center diff will just kinda let it happen and wear itself out faster.

thefultonhow · Post by **thefultonhow** » Wed Apr 19, 2006 4:26 am

subyluvr2212 wrote:the 5MT viscous center diff will just kinda let it happen and wear itself out faster.

How much faster? If I were to run on a stock wheel/tire for, say, 500 miles while on a cross-country trip, would the diff be toast afterwards? Or would it just take several thousand miles off the (probably fairly long) life of the diff?

legacycentral bbs

A forum for 89-94 BC-BF(BJ) Legacy Owners and Fans

Spare tire with WRX wheels?

Spare tire with WRX wheels?