Forester Different Sized Tires

Where is the fuse on a 2003 Forester that converts the car from AWD to FWD. I am getting 4 new tires, and I want to make sure I know how to turn off the AWD if I get a flat.

What do you do if one of tires goes bad and needs to be replaced, say after they have 30,000 miles on them? I am concerned about breaking the AWD system.

How do I know if the difference in the size (due to wear) of the tires is a problem or not?

Thanks a lot.

Mel

Reply to
Mel
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The fuse location is usually under the hood, there should be a covered fuse panel. This is only on automatic transmission cars, however. Manual trans and you have to stay below 50mph or something like that.

Subaru says the tires have to be within 1/4 inch in circumference to prevent damage to the AWD system.

There are 3 options when you have tires with some wear and you need to replace one:

1) replace all of 'em 2) Buy a new tire and have it 'shaved' to match (usually must be done before any driving is done on the tire) 3) Find a used tire the right size. Same brand and model, or odd handling may occur.

Dave

Reply to
spamTHISbrp

Oh, option 4, only an option if you don't have a limited-slip differential: get 2 new tires, put one in the front, and one in the back on the opposite side.

Odd handling is a (remote, IMHO) possibility.

Dave

Reply to
spamTHISbrp

Hi, No owner's manual?

Reply to
Tony Hwang

I know where the fuse is that converts to FWD, but it seems to me it would be better if Subaru had just put a toggle switch on the dash to do the job. I seldom need 4WD and I am smart enough to know when I do need it. I would prefer to drive most of the time in FWD and the switch would allow easy change to FWD when it is needed.

Is there some technical reason why this is not possible?

Reply to
Rodney Lake

Why did you buy a Subaru if you don't need the 4WD? Anyways, Subarus usually have 3 or 4 different AWD systems that they use. One version goes on low-end manual transmission versions, which is all fluid-mechanical -- it can't ever be turned off.

Then there is one that goes on low-end automatic transmissions, which is basically an on-off system. It acts in FWD mode most of the time, and then switches to AWD when it detects some slippage in the wheels. This is likely the system that you have, and this is what the fuse is for, it prevents the wheels from ever going into AWD mode. For the most part, when you are not driving in anything slippery then you are already driving only in FWD mode. So why would you want to disable the fuse on a full-time basis? That fuse is there for specific situations like when you're being towed. Otherwise, the car is already deciding to keep you in FWD mode anyways.

Then there are two more sophisticated high-end AWD systems. One they use on the high-performance STI car. The other one they use in the high end cars with VDC (vehicle dynamics control). I don't think they apply to you.

Yousuf Khan

Reply to
Yousuf Khan

No, a marketing reason. Subaru trumpets the benefits of full-time AWD (versus the 'on demand' systems that many other manufacturers use). So why would they then allow you to switch between 2WD and AWD?

Dan D '99 Impreza 2.5 RS (son's) Central NJ USA

Reply to
Dano58

There was a long discussion over at

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on methods to create just such a switch. You might try a search there.

Carl

Reply to
Carl 1 Lucky Texan

What other cars (not trucks!) can turn off AWD?

Reply to
Valued Corporate #120,345 Empl

A switch is perfectly possible, but the MPG gain will be quite small (if at all) since all the drivetrain will be spinning anyway.

Also, the solenoid that dumps the pump pressure (allowing the front/ rear clutchpack to spin free) is not made for a 100% duty cycle. It will likely eventually fail if always energized.

Dave

Reply to
spamTHISbrp

The possible solenoid failure makes sense and rules out a switch.

I bought this forester in 07 because I had owned several subarus prior to

1990 before they had full time AWD. These were sturdy cars with good gas mileage. the salesman who went with me for a test drive seemed like a nice sort and I made a lowball cash offer to keep his boss happy. They accepted it so now I have one. It seems like a nice car but the problems associated with different tire sizes and the timing belt mean that I will probably trade for a toyota in a couple years. I don't see any advantage to AWD since most of my driving is on dry pavement.
Reply to
Rodney Lake

Could someone tell me where this "1/4" circumference" rule comes from? I see no such thing in my US-market 2002 Legacy owner's manual. I'll check the factory service manuals when I get home.

Reply to
mylesv

The low-end automatic system is a bit better than you describe, in the later generation subarus (like my '03)

The duty-c solenoid (100% energized=rear wheels disconnected, 0% energized, rear locked to front) is strobed with a varying pulse-width signal to achieve different degrees of coupling between the front and rear wheels.

Typically the front-rear ratio is 90/10, when slip is detected, or when full-throttle is applied, or when the shifter is in 1,2, or R the duty C soenoid is minimally strobed and egffectively a 50/50 front/ rear torque split is achieved.

(note- 50/50 meaning rear driveshaft 'locked' to the 'front' driveshaft, the notional front driveshaft never actually leaving the trans case)

Dave

Reply to
spamTHISbrp

My '01 OBW did in fact have a specific measurement listed in the manual. I no longer have the car, so I can't point you to a section.

Reply to
Valued Corporate #120,345 Empl

Plenty. In fact, MOST cars that advertise 'AWD' are really part-time systems, where they are FWD (i.e., Audi TT*) or RWD (i.e., Infiniti G37) until the system detects slippage, then routes power to the other set of wheels. This results in a momentary delay in getting the 'AWD' engaged, which could prove to be the difference between control and not.

As far as I know, Subaru is really the only company that equips all of their US cars with full-time AWD as a standard feature.

*Audi calls their AWD 'quattro' on all of their cars, but actually uses 2 different systems - one for cars with transverse engines like the TT and A3, another - with REAL fulltime AWD - for the longitudinally-equipped cars like the A4, A5, A6 and A8.

Dan D '99 Impreza 2.5 RS (son's) Central NJ USA

Reply to
Dano58

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