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Guest Message by DevFuse
 

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damage from unequal tread?


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13 replies to this topic

#1 subestyle18

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Posted 07 September 2012 - 02:29 PM

I have a 93 legacy awd with a manual. I have one tire that went flat on the highway and needs to be replaced. The rest of the tires are quite worn and will be replaced in the spring when i take my snow tires off. My spare is full size with almost new tread. What and how much damage will i cause running the spare for another month? 1500 miles including a 700 mile trip from seattle to bozeman.

on a side note: if anyone has a used tire in a 185/70/14 in the seattle/woodinville area between now and sunday, id be happy to buy it from you.

#2 1 Lucky Texan

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Posted 07 September 2012 - 03:03 PM

I doubt anyone can tell you precisely - only that it's a bad idea. And the torque bind damage is expensive to repair - might be hazardous too.

have the spare shaved to match the other 3 .



note, a replacement used tire needs to be the same brand/model and if possible age of the other 3 (in case the manufacturer made changes to the model)

check ebay for used tires.

or get a new, matched set.

Edited by 1 Lucky Texan, 07 September 2012 - 03:07 PM.


#3 Ricearu

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Posted 07 September 2012 - 03:55 PM

i have purposely went to a used tire shop and told them to bring me a tire out with 4/32's of tread to match the others. been like that for 5 months. They are hella bald now.

#4 quazi

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Posted 07 September 2012 - 05:27 PM

I waited and waited until I had the CASH to replace the tires on my Forester.

Towards the end, they really seemed to wear quickly.

Then I started to get that rubbery torquebind shudder at slow speed turns.

I quick dug deep to find $700 to buy 4 new tires.

Too late. Wednesday I plopped down 700 bones on the PLASTIC to buy a new V/C and bearings. Yesterday, I rolled around in grease and tranny fluid all day. Today, I re-assemble.

Next time, I buy tires on credit and pay cash for a flight to the Islands.

JW

#5 The Dude

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Posted 07 September 2012 - 07:36 PM

I have a 93 legacy awd with a manual. I have one tire that went flat on the highway and needs to be replaced. The rest of the tires are quite worn and will be replaced in the spring when i take my snow tires off. My spare is full size with almost new tread. What and how much damage will i cause running the spare for another month? 1500 miles including a 700 mile trip from seattle to bozeman.

on a side note: if anyone has a used tire in a 185/70/14 in the seattle/woodinville area between now and sunday, id be happy to buy it from you.


Here's the thing with a VC, you frequently don't get any warning. When you notice a problem it's too late, the permanent damage has been done.

And MEASURE the circumference of all the tires, especially the replacement tire. I think the spec is only 1/8", which is very, very tight.

BTW, if you had an AT, you could just slap a fuse in the engine compartment fuse box and run the car indefinitely in AWD. MTs have advantages over ATs, but not always.

You're going to need new tires anyway. I would buy them now and not even have deal with the possibilty of an expensive VC replacement.

#6 nipper

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Posted 07 September 2012 - 08:12 PM

IN an emergency. you can get away with 2 tires, both on the same side of the car. This is ONLY if you do not have a VC in the rear diff.

This is why i carry a full sized spare. I have it in my tire rotation.

VC give no warning anything is wrong untill it is to late. An automatic will give you hints and clues before doom.

Edited by nipper, 10 September 2012 - 09:29 PM.


#7 heartless

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Posted 10 September 2012 - 08:15 AM

I have a 93 legacy awd with a manual. I have one tire that went flat on the highway and needs to be replaced. The rest of the tires are quite worn and will be replaced in the spring when i take my snow tires off. My spare is full size with almost new tread. What and how much damage will i cause running the spare for another month? 1500 miles including a 700 mile trip from seattle to bozeman.

on a side note: if anyone has a used tire in a 185/70/14 in the seattle/woodinville area between now and sunday, id be happy to buy it from you.


being a 93 - is there a fuse holder under the hood to put the car into FWD mode? (dont know about this on a manual car, since all I have here are autos) should be somewhere near the passenger side strut tower (90 it is at the back of the tower, closest to the firewall) Should have the letters "FWD" on the top (if the top is still attached)

If there is, put the odd tire on the rear of the car, and use a fuse (any size will work) to force FWD only. Not the ideal solution, but works in a pinch.
Just had to do this with my car a couple of days ago - picked up a screw in a tire, tire went flat. Put on a full size spare (used from a parts car), popped a fuse in, go get the tire fixed without worry of doing serious damage to trans.

I will say it 'felt' odd being in FWD mode after being used to the AWD...

#8 MilesFox

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Posted 10 September 2012 - 09:02 PM

IN an emergency. you can get away with 2 tires, both on the same size of the car. This is ONLY if you do not have a VC in the rear diff.

This is why i carry a full sized spare. I have it in my tire rotation.

VC give no warning anything is wrong untill it is to late. An automatic will give you hints and clues before doom.


you can run 2 matching tires that may be different than the original size mounting them diagonal from eachother as the front and rear diff will soak up rotational difference and the center coupling stays constant with a matching tire on each axle.

the torque transfer will assume the ratio of the smaller tires. You can do this if you are just buying 2 new tires in the original size but don't want to drop the bones for 4 tires and not ruin your transmission.

#9 grossgary

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Posted 11 September 2012 - 09:01 AM

being a 93 - is there a fuse holder under the hood to put the car into FWD mode? .

that is for automatics only, manual trans are completely different.

you can run 2 matching tires that may be different than the original size mounting them diagonal from eachother

this is what the tire shops do around here to all the Subarus who can't afford new tire sets. like so:

take two tires (A & B) of the same circumference and put A on one of the fronts and B on the opposite side (of A) rear.

that works if A & B are both new and larger tires...not sure about your situation where one is larger.

a FWD car is really only one-wheel-drive and your 4WD legacy is really only two wheel drive....so if the one front and opposite side rear that are being driven have the same tire tread you're golden.

not positive still on how that shakes out with one larger and 3 old though....

#10 1 Lucky Texan

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Posted 11 September 2012 - 09:18 AM

I've read some folks will over-inflate the small tire and under-inflate the others - but that is also less than ideal to possibly dangerous.

#11 nipper

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Posted 11 September 2012 - 04:09 PM

a FWD car is really only one-wheel-drive and your 4WD legacy is really only two wheel drive....so if the one front and opposite side rear that are being driven have the same tire tread you're golden.


Not really, that one wheel example only applies if you get stuck or loose traction.. On dry ground you have 2wd and 4wd respectivly. A differential is a mechanical computer. It divieds the power between two spinning wheels

http://www.howstuffw...ifferential.htm

Simplistically.. if the car goes straight, 4 turns of the drive shaft (1:1 final drive for math sake) will result in 4 turns of the wheels. Making a hard turn the outside wheel turns faster, the inner wheel turns slower, so one wheel will turn six times, one wheel 2 times, with the same 4 turn input.

If traction is lost, then one wheel will turn no times, the spinng wheel will turn 8 times the drivshaft 4 times. This is why you never (on a 2wd open diff) never take a wheel faster then 30 mph because on that one wheel it would be 60.

If both wheels are off the ground they may even spin in differnt directions.

#12 1 Lucky Texan

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Posted 11 September 2012 - 09:33 PM

off topic but, this is the most fun explanation of a differential;



#13 nipper

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Posted 11 September 2012 - 10:35 PM

Actually that was on topic, but i love how it was before they invented the driveshaft tunnel.

#14 TahoeFerrari

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Posted 15 September 2012 - 05:54 AM

off topic but, this is the most fun explanation of a differential;


And we think we're so smart! Those early designers/engineers definitely had more fun than we do.




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