I blew one of my snow tires. Hooray. They are just over 1/4" worn from new, how bad is the risk?

[SnatchedHatch]

EDIT:

Yikes, I may have misinterpreted the 1/4" RoT

"All four tires must match in circumference within 1/4 inch."

For those wondering, http://www.tacomaworld.com/forum/tirecalc.php

is a great online tire size comparison caluclator.

It shows that a size 205/50R16 compared to my 205/55R16 is a whopping 2.54 inches off in circumference. Looks like the level of tolerance the Subaru AWD system defines requires the exact same size tire, within 2 or 3/32" in tread depth.

EDIT2:

SOLUTION, I ordered a shaved tire from Tire Rack.

They didn't have my Mastercraft (Cooper) tire, so I had a choice between:

the Goodyear Ultra Grip and the General Altimax Artic.

Some reviews pointed to soft sidewalls on the General Alti's, susceptible to bubbles or bursts, especially the smaller 16" sizes.

Ultra Grip's with the $25 shaving fee, are being shipped to my local tire shop for ~$120

 

I looked around for a used tire of the same wear and dimension: Craigslist, online as a new unit, and finally found that eBay has quite a few of such at reasonable prices. I could pick up a matching tire for ~$60.

Check your local shops as well, I didn't have luck in my area.

 

 

I looked around and found these two useful threads, in case anyone else is in the same boat:

http://www.ultimatesubaru.org/forum/topic/96012-tire-blowout-from-pothole/?hl=%2Btire+%2Bblowout

http://www.ultimatesubaru.org/forum/topic/90673-replacing-1-snow-tire/?hl=%2Btire+%2Bblowout&do=findComment&comment=760818

I blew out one of my snow tires... they had two seasons of use so I'm looking for the same tire with similar wear. Can't do that on short notice,

the best option I have is a new matching tire from the interwebs, identical in every way.

My tires are just over a 1/4" worn (7-8/32", new they have 13/32").

 

I have zero drivetrain issues, car is rock solid.

 

What exactly am I risking running the line so close? How bad is
it/the chance of wear... I suppose I'm asking for anyone with experience
with a mismatched tire on an AWD enabled Subie.

Edit: Seeing as a new tire is far out of the acceptable dimensions, I will have to look around for an appropriate used tire.

I'm still interested in the following:

 

Another option I see fit, is moving the new tire to the rear, and disabling AWD ==> FWD

 

Am I wrong to have noticed a trend in members developing strange issues from prolonged "FWD enabled" usage?

I've looked at the FWD fuse.. removal (or insertion?) in the past out of curiosity and picked up on a number of individuals developing torque bind. Maybe that information was misleading :/ still would like to hear your two cents on this, thanks.

 

 

 

Side note, my 17 year old wagon seems to never have needed it's spare. The jack and tools are..were mint.

Hmm.. wasn't used to not having a lift jack and a flat surface, no complaints.

 

Edited February 3, 2015 by SnatchedHatch

[forester2002s]

Just noticed that you posted this twice.

Here's what I wrote in the other post:

 

A bit of math:

1/4" tread-depth is 1/2" wear on diameter.

And that is pi x 1/2" = about 1.5" on circumference.

Definitely a mismatch!

[Fairtax4me]

How bad did it blow out?

Did it cut the sidewall or just put a hole in the tread?

If you didn't drive far after the tire deflated there may be a chance the tire can be saved IF the puncture was in the center of the tire.

[SnatchedHatch]

Just noticed that you posted this twice.

Here's what I wrote in the other post:

 

A bit of math:

1/4" tread-depth is 1/2" wear on diameter.

And that is pi x 1/2" = about 1.5" on circumference.

Definitely a mismatch!

Thanks again, but you must have skipped the content of my message!

Post has been modified.

 

Edit: Looks like I just missed you!

Edited February 3, 2015 by SnatchedHatch

[SnatchedHatch]

I'm afraid it's a true and cut blowout of the sidewall. I've got a bit of experience with tires, just not the whole AWD transmission end of the stick.

 

I had thought I might have just unseated the bead, the rim only got a nick on the exterior, seriously unscathed.

Once I had it in my trunk, I saw it was sadly toast.

How bad did it blow out?
Did it cut the sidewall or just put a hole in the tread?
If you didn't drive far after the tire deflated there may be a chance the tire can be saved IF the puncture was in the center of the tire.

 

 

I guess this post can be retitled, "Has anyone had any issues with their auto-trans drivetrain after disabling their AWD?"

[Fairtax4me]

Buy two, stick them on the front, run the rears a bit over inflated and the fronts a bit under inflated for a few 10 thousand miles.

I did that on my 96 (don't tell anyone) and it turned out Ok, but its a manual trans and less susceptible to wear from doing something stupid like that.

 

Or you could put it in FWD and do a couple good burnouts and wear some tread off.

[SnatchedHatch]

Very insightful information on the former..

..waaiiit a minute, I think you need to double check your claims pardner.

Do you mean one or two psi under/over?

Buy two, stick them on the front, run the rears a bit over inflated and the fronts a bit under inflated for a few 10 thousand miles.




Or you could put it in FWD and do a couple good burnouts and wear some tread off.

Oh yeahhh wheewww we have a winner here.
Mah! Where are my jack stands?!

Edited February 3, 2015 by SnatchedHatch

[naru]

You might look for a local shop w/a tire truing /shaving machine.

They could match the circumference of a new tire to your old ones.

[SnatchedHatch]

You might look for a local shop w/a tire truing /shaving machine.

They could match the circumference of a new tire to your old ones.

It's about 90minutes or so from me, I have to weigh the added cost, and time.

My car is hobbled for the time being.

 

Having some headway on a set of winter tires/steelies. It's the best bet I have so far, besides working off of a new tire.

since two of the tires are near bald, I'll use the pair that have about 5-6/32" tread depth left (again mine: 7-8/32")

Salvage the two, and utilize the rims.

 

For the sake of this thread, I'll update if I take the shaving route, or resort to my FWD fuse.

Edited February 3, 2015 by SnatchedHatch

[lvsarge]

I always thought the tollerance was much smaller than 1/4 inch... somewhere around 3/32"

[heartless]

donut spare should be put on the rear of the car, AND FWD fuse inserted (on AWD automatics) until a proper tire is put on the car. the reason for this is it lessens the impact/stress of the mismatched tire on the drivetrain (donut spare is a fair bit smaller).

 

source: owners manual (for 1st gen Legacy's - have several)

[Fairtax4me]

Very insightful information on the former..

..waaiiit a minute, I think you need to double check your claims pardner.

Do you mean one or two psi under/over?

 

Oh yeahhh wheewww we have a winner here.

Mah! Where are my jack stands?!

A brand new tire (more tread) will have a larger diameter, and will spin slower (fewer revolutions per mile) than a worn tire.

A worn tire (less tread) will have a smaller diameter, and will spin faster (more revolutions per mile).

Under-inflating decreases the diameter of the tire.

Over-inflating increases diameter.

By decreasing the diameter of the new tire, it will spin faster (more revolutions per mile) and will be closer in rpm to the worn tire.

 

Put the new tires on the front where they're going to wear the fastest, under-inflate by 3-4psi. Old tires on the back, over-inflated slightly, 2-3psi.

The difference in rotational speed isn't quite as far off as it would be with them properly inflated, and the tread will wear a bit faster. After 8-10,000 miles they should be about even.

 

 

Disclaimer: I do NOT :wink: :wink: recommend that anyone actually try this.

Edited February 3, 2015 by Fairtax4me

[SnatchedHatch]

"

Another option I see fit, is moving the new tire to the rear, and disabling AWD ==> FWD

 

Am I wrong to have noticed a trend in members developing strange issues from prolonged "FWD enabled" usage?

I've
looked at the FWD fuse.. removal (or insertion?) in the past out of
curiosity and picked up on a number of individuals developing torque
bind. Maybe that information was misleading :/ still would like to hear your two cents on this, thanks.

"

 

 

donut spare should be put on the rear of the car, AND FWD fuse inserted (on AWD automatics) until a proper tire is put on the car. the reason for this is it lessens the impact/stress of the mismatched tire on the drivetrain (donut spare is a fair bit smaller).

 

source: owners manual (for 1st gen Legacy's - have several)

[SnatchedHatch]

A brand new tire (more tread) will have a larger diameter, and will spin slower (fewer revolutions per mile) than a worn tire.

A worn tire (less tread) will have a smaller diameter, and will spin faster (more revolutions per mile).

Under-inflating decreases the diameter of the tire.

Over-inflating increases diameter.

By decreasing the diameter of the new tire, it will spin faster (more revolutions per mile) and will be closer in rpm to the worn tire.

 

Put the new tires on the front where they're going to wear the fastest, under-inflate by 3-4psi. Old tires on the back, over-inflated slightly, 2-3psi.

The difference in rotational speed isn't quite as far off as it would be with them properly inflated, and the tread will wear a bit faster. After 8-10,000 miles they should be about even.

 

 

Disclaimer: I do NOT :wink: :wink: recommend that anyone actually try this.

 

That's not exactly how under and over inflated tires wear, not evenly that is.

Hence why I questioned your advice, and my suggested marginal pressure difference.

 

For those wondering, under inflating a tire significantly will wear it at the edges, the shoulders.

An over inflated tire suffers the same at the center of the thread, or if not properly aligned, the left portion or right portion of the thread, depending on the setup.

 

I personally don't recommend FairTax4Me's strategy either, I think it's results have the same chance of helping as hurting your situation, whether it be a negligible difference on the drive train, or the adverse effect on your tires.

 

Edited February 3, 2015 by SnatchedHatch

[idosubaru]

can you post a link to a thread where someone says they  have torque bind issues after using the FWD fuse?

[SnatchedHatch]

can you post a link to a thread where someone says they  have torque bind issues after using the FWD fuse?

 

It may have been misleading info, as there was a general trend of those complaints coming from individuals with high-mileage (by our standards) subarus, in which they resorted to keeping FWD on after discovering a bit of torque bind.

 

Also, I've read and heard a notice from SOA mentioning that the FWD-mode is intended "for towing and diagnostic purposes" with no mention of DDing.

I just turned on my FWD mode today, and rotated the other two tires.

Dash light on.. front's a spinnin'.. I'm only driving like this til Friday.

 

Thread update, ordered a shaved winter tire. It was about $125 including shipping to my local shop.

[Olnick]

Just curious, Snatched--how do you order a shaved tire?  Did you give them the circumference to match?

[keith3267]

WHY???  1/4" is 8/32", that means all your tires are down to 4/32" tread, they don't have much life in them.  In this case, you should have just gotten 4 new tires.  When my tires are down to 4/32", I'm looking for a sale on new tires and if the price is right, I'm buying.

 

Keep the best tire in case the new set blows one when they are half worn.

[SnatchedHatch]

Just curious, Snatched--how do you order a shaved tire? Did you give them the circumference to match?

I had to call them, and I gave a tread depth. Chose a bit higher than what the rest are at.

[SnatchedHatch]

1/4" is measured by the tire circumference , not the thread depth.

No doubt, 1/4" depth is basically a bald tire to me.

 

WHY??? 1/4" is 8/32", that means all your tires are down to 4/32" tread, they don't have much life in them. In this case, you should have just gotten 4 new tires. When my tires are down to 4/32", I'm looking for a sale on new tires and if the price is right, I'm buying.

 

Keep the best tire in case the new set blows one when they are half worn.

[keith3267]

1/4" circumference, that makes a difference.

[SnatchedHatch]

1/4" circumference, that makes a difference.

Yes, yes it does.

[funk]

You do not want larger tires on the back. Overdriven back tires will try to walk around on slick road, very unstable. Put the new ones on the front & keep the back tires slightly overinflated, remember that the back tires carry less weight and have a greater circumference at the same PSI than tires on the front which bear more load. Just a few extra PSI should make up the difference ~ this way you won't have to subject your new tires to uneven wear from underinflation or sacrifice their longevity by trimming down tread. On a level surface, carefully measure and adjust PSI accordingly.

[Fairtax4me]

That's not exactly how under and over inflated tires wear, not evenly that is.

Hence why I questioned your advice, and my suggested marginal pressure difference.

 

I didn't say I was a good idea.

A few psi (2-4) won't cause a significant difference in treadwear, especially if you're a "spirited" driver where you're driving style will cause more wear anyway. The shoulders of a slightly under inflated tire will wear more than usual but the center still wears too. A tire has to be grossly under inflated to have a major difference in treadwear from center to shoulder after 10k miles.

 

But when you compare the cost of a set of tires to the cost of a center diff or clutch pack... Which one really costs more?

[SnatchedHatch]

I didn't say I was a good idea.

 

"I personally don't recommend FairTax4Me's strategy either,"

 

You have a point about a spirited driver wearing a tire more evenly. However, those levels of spirit would be beating on this kind of car, with this age. Not recommended haha, but I do get you.

Edited February 8, 2015 by SnatchedHatch