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SICK-92-AWD
02-16-2006, 06:35 AM
hey, my back 2 rims are stuffed and had to be removed, is it ok to have a set of wheels on the rear that are 10mm larger? will this cause issues with the constant awd? need advice asap. thanx - phill

Wiscon_Mark
02-16-2006, 07:42 AM
yeah, don't do it. It will fry your differential.

Pwise2326
02-16-2006, 08:06 AM
HUUUUGE NO-NO!! Even having 1 newer tire on there that has a little more tread than the other 3 will cause you some serious issues. If you ever have to replace everything, make sure all the wheels are the same, and make sure that you get 4 tires at a time! You can't just replace two like on a FWD or RWD car. A little more money out of the pocket, but we all know the benefits of the AWD.

Huffer
02-16-2006, 10:55 AM
is it ok to have a set of wheels on the rear that are 10mm larger?

Definitely not. Backing up what people have said - even seriously worn tire tread can play havoc with the center diff.

That's why it's so important to rotate your tires regularly. It also means that Subaru's are a big consumer of tires - one blowout and you only have two options - repair or 4 new tires.

belladonna
02-16-2006, 11:17 AM
so this brings about the question of how often should tires be rotated...i used to do mine every two oil changes. i know it's excessive, but oh well. i feel better knowing things are done.

NewGenSTi
02-16-2006, 12:36 PM
every other oil change doesnt seem excessive to me. I was always told every 6000 miles. so I do the 2 oil change also

Huffer
02-16-2006, 12:37 PM
so this brings about the question of how often should tires be rotated...i used to do mine every two oil changes. i know it's excessive, but oh well. i feel better knowing things are done.

Every season change for me.

shazapple
02-16-2006, 12:50 PM
I change mine every season.

You can get new tires shaved down to match your current tires. I forget what Subaru says is an acceptable difference in diameter. It should say in your manual

Pwise2326
02-16-2006, 01:13 PM
I think the tolerance is a very small fraction of an inch, I think an 1/8th of an inch difference MAX, but I think it may be even less than that. You can't excessively rotate your tires, once is usually more than a lot of people bother to do...not to mention the sick amount of lazy people that will pay to get their tires rotated...when all it takes is a jack and 10 minutes of your time.

Wiscon_Mark
02-16-2006, 01:37 PM
Every season change for me.

yep, same here. Which means about every 6k

Huffer
02-16-2006, 01:47 PM
I get an alignment prior to every winter/summer too - and when that happens I have them rotate the wheels. So I only have to do it myself twice. HA!

Go the Firestone Mastercare Lifetime Alignment for $199!

PWise - for most people rotating tires takes much longer than 10mins... and a lot of people don't actually have the right tools to do it quickly.

Plays_with_Toys
02-16-2006, 02:54 PM
Yeah, how are you rotating your tires with one jack? You criss cross correct?

Huffer
02-16-2006, 03:26 PM
This is a good illustration:
http://www.sullivantire.com/trainingcen ... ation.aspx (http://www.sullivantire.com/trainingcenter/tire_rotation.aspx)

95legacy
02-16-2006, 04:47 PM
You could just pull the FWD fuse for time being couldnt you? Or is that not going to help or anything.
Peace,
Kyle

Huffer
02-16-2006, 05:31 PM
You could just pull the FWD fuse for time being couldnt you? Or is that not going to help or anything.
Peace,
Kyle

If the car is 4EAT it might.

ivwarrior
02-16-2006, 10:13 PM
While I haven't timed myself, I'm sure I could rotate in 10 minutes or less. Once all the tools are out of the basement, and the air compressor has filled its tank, of course.

I never cross, tires always stay on the same side of the vehicle.

I used to work at a tire shop. If you bought tires from us, you got lifetime free rotation on those tires. The shop recommended rotation every 3,000 miles.

strat81
02-17-2006, 01:48 AM
most tire manufacturers recommend every 6,000 miles... if you have your owner's manual/service manual it should tell you what the intervals are for tire rotation in there.

SICK-92-AWD
02-19-2006, 05:54 AM
If I had driven with the different wheels on would something have blown straight away or is it a slow damaging process? Like would I be safe driving 2km down the road to the mechanic?

Sarra
02-19-2006, 06:40 AM
What happens is, if the front and rear wheels are rotating at a different speed:

If you have a 5MT, the two outputs on the center diff will spin at different speeds, and so the fluid in the diff will heat up, causing the friction coeffecient of the fluid to increase. However, this won't do anything since you aren't in a slippery condition, so the fluid will continue to heat up, until the diff will spring a leak, then you have Vicious fluid flowing into your gear case. :(

If you have a 4EAT, the sensor might not catch the difference, so you'd be 90/10, front rear bias. Gradually, it will overheat and burn the clutch out. Otherwise, if the sensor does catch the difference in rotation speeds in the front and rear, it may kick the clutch into 50/50 bias, and then it would overheat quickly.

The best thing you could do would be to get it towed with all 4 wheels off the ground (flatbed or have them put the wheels under your rear wheels like they have done for me three times now). Driving 2 km shouldn't be a big deal, but if the center diff or center clutch is worn down, at the end of it's life, or in bad shape, it may fail. Then you have a contionious 0WD car. :p

As mentioned, if it's a 4EAT, you should be able to drive it without problem if you put the FWD fuse in it's little place.

Oh, for the record... My current car has been driven for about 30k miles with 3 summer tires and 1 all season tire on it. The all seasons were getting down on tread while the all season tire was bald and flatspotted. I haven't had any problems other than fuel pump going out, factory defective oil pan, bad coil pack, bad spark plugs, and a few other minor things. Mostly not related to the tires. I'm just waiting for my gearbox to crap out on me now. :(

Edit: If you absolutely HAVE to run 2 "large" and 2 "not so large" tires, if you know that you have open front and rear differentials, you can put the 2 "large" tires on the left, and the 2 "not so large" tires on the right. The front and rear diffs, if they are standard open diffs, won't honestly give a flying monkey poo if the output shafts are rotating at different speeds. If you have a GT or turbo, you probably have a LSD rear diff, and that woudln't be a good idea either. :(

SICK-92-AWD
02-19-2006, 07:17 AM
Thanx man, thats helpful. so if i have sprung a leak will it be coming out of the diff at the rear?

gator gt
02-19-2006, 03:15 PM
Never have differing tire &/or rims sizes on an AWD vehicle. Same thing for 4WD vehicles, unless you leave it in 2WD until you fix it.

Considering I put 6k miles in 3 months, I rotate tires and change oil every 3k miles.

Oh I can't wait for the day when I kill my commute by 3/4! :roll:

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