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Old 6th November 2008, 11:48   #1
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Default Forester users- Tyre questions

Hi, this is to all the forester users and fans out here:
I read somewhere that in the event of uneven wearout of one or two tyres, ALL the four tyres need to be changed. This is due to the AWD system.
Now, I recently bought a forester which has Michelin 215/70 R15 A/T and has run 46k km. However, one of them has worn out visibly more than the other 3 which look easily good for another 15-20k km more. This was due to wrong alignment and has been corrected since then. My doubts are:

1) Do I need to change all four tyres? Can I make do with two new tyres only at the rear?

2) If so, will it affect the AWD system/ differentials and handling of the car?

3) The stock size is 205/70 R15. What would be the best option for an upsize? I do not want to compromise on the ride and handling though.

Thanks.
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Old 8th November 2008, 13:55   #2
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My understanding is that you need to replace all 4 at a time since there will be uneven wear and matters become worse when you do a tyre rotation. 'Reji22' or 'Mura' may be able to throw more light

Regarding upsizing- again I am not an expert but I think it is better to stick to the existing fatter rubber if you do a bit of offroading - Bigger wheel-low profile tyres are not ideal.
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Old 9th November 2008, 12:38   #3
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Take your car to a good wheel alingment place, Preferably one with 3D alignment machine and sort out your geomentry first and then if you are ok with the extra expense of changing 4 tires, get them changed or change 2 tires and use the new ones on the front.

I would stick to the OE size for the OE wheels. If you go for a set of alloys upsize to 16 inch and 225-60-16. PCD is 5X100 offset is 55.
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Old 10th November 2008, 18:36   #4
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Quote:
Originally Posted by mura View Post
Take your car to a good wheel alingment place, Preferably one with 3D alignment machine and sort out your geomentry first and then if you are ok with the extra expense of changing 4 tires, get them changed or change 2 tires and use the new ones on the front.

I would stick to the OE size for the OE wheels. If you go for a set of alloys upsize to 16 inch and 225-60-16. PCD is 5X100 offset is 55.
Thanks mura and Guna for the input. I think I will change all of them and stick with the OE size as recommended.
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Old 10th November 2008, 19:00   #5
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The AWD system is a big factor regarding tire selection and condition. All 4 tires need to be in very similar shape in terms of wear. If one tire is heavily worn, and the other 3 at 50%+, you should probably put in a new set of tires. The AWD sytem requires all 4 tires to be identical shape to work properly. Otherwise you may stress the differentials and cause unecessary stress on the AWD system.

Alignment is very important, and getting it done correctly will be a challenge. I recently found a very large Bridgestone dealer in Gurgaon who has a Hunter 3D machine. Guess what, he could not find a Chevrolet Forester on his computer. After a bit of hesitation, I convinced him to look under Subaru, and he found the alignment specs.! I'll be getting my next alignment there.

Another precaution is to regularly do tire rotation. For the Forester, just rotate the front to back.

The stock size is 205/70-15. This is also the size of the spare. Keep in mind that if you run 215/70-15, you do not have a very usable spare. Which is not a good idea. If you really want to run a different diameter tire, just make sure that your spare tire is the same diameter.
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Old 10th November 2008, 19:13   #6
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You must replace all 4 tyres on the Forester. Unless the remaining three tyres are relatively new (not the case in yours), there will be a noticeable difference in the tread depth; not ideal for the AWD mechanicals.

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Black Forester
When did that happen, RedMM? You really got a thing for AWD eh?
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Old 10th November 2008, 19:54   #7
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DON'T CHANGE tyre diameter on any car with ABS and TCS. Larger dia tyres will cause the ABS to cut in too soon, compromising braking. You may increase the tyre width, but stick to the OEM tyre diameter.
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Old 11th November 2008, 13:04   #8
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Originally Posted by GTO View Post

When did that happen, RedMM? You really got a thing for AWD eh?
GTO,
Well yes, I guess I am a bit biased toward 4 wheel drive. Got the Forester a few weeks back, and just love it. An absolute blast in the hills, and great high speed highway cruiser. Can't beat a Forester for long trips.

I just might get some WRX STi mechanicals and make it rally car.

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DON'T CHANGE tyre diameter on any car with ABS and TCS. Larger dia tyres will cause the ABS to cut in too soon, compromising braking. You may increase the tyre width, but stick to the OEM tyre diameter.
Alfa,
Don't believe that diameter change on all 4 wheels will affect ABS/TCS. Since these systems compare relative wheels speeds from all 4 wheels to detect wheelspin.
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Old 11th November 2008, 17:40   #9
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That's good info, thanks RedMM340. There is a Dealer with the Hunter 3D here in Cochin, but his machine is so busy that you got to wait for 2-3 hours. Anyway, I'll get it done there. But a small clarification here: How do we know that the Forester alignment specs stored in his system matches my car- 2004 model ? Or are the specs same across all foresters ( which in unlikely)?

Also, which are the best options for the OE size, ie 205/70-15? The stock ones are Bridgestone. How about Michelin or others?
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Old 11th November 2008, 21:51   #10
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Quote:
Originally Posted by thejuk View Post
That's good info, thanks RedMM340. There is a Dealer with the Hunter 3D here in Cochin, but his machine is so busy that you got to wait for 2-3 hours. Anyway, I'll get it done there. But a small clarification here: How do we know that the Forester alignment specs stored in his system matches my car- 2004 model ? Or are the specs same across all foresters ( which in unlikely)?

Also, which are the best options for the OE size, ie 205/70-15? The stock ones are Bridgestone. How about Michelin or others?
The Forester owner's manual lists wheel alignment specs:

Toe, Front 0 +/- 3mm
Toe, Rear 2 +/- 3mm

Camber Front -0deg25' +/-45'
Camber Rear -0deg50' +/-45'

All non-turbo Foresters from '03 to '07 have the same spec. The Turbo models just have and addition -5' camber for the rear wheels.

All major tire manufacturers are good, so just get a tire that meets your needs better. My current tires are Yokohama ATs that are noisy on the highway, but good for rough, potholed, damaged roads.

The Michelins are comfortable and quiet, or you can get more sporty rubber compounds for cornering. I prefer to get a tire with at least 2 ply sidewalls for puncture resistance.
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Old 12th November 2008, 02:02   #11
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Man, where the hell did you manage to find a used forester in cochin? what year is the vehicle and how much did you pay for it?
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Old 12th November 2008, 23:44   #12
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FYI - All Subaru 2004-2006 WRX/STi suspension bits fit the Forester.

By fitting the WRX struts and springs you can improve ride and lower the car by 1.5 inches.

See : How to turn better than an STI for cheap! - Subaru Forester Owners Forum
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Old 13th November 2008, 21:39   #13
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Quote:
Originally Posted by RedMM340 View Post
Alfa,
Don't believe that diameter change on all 4 wheels will affect ABS/TCS. Since these systems compare relative wheels speeds from all 4 wheels to detect wheelspin.
ABS and TCS systems compare wheel rotation with linear acceleration to determine wheel slip/lockup. The tyre dia is very important for this to work properly. If the tyres are too small, then the system will allow too much slip, and oversize tyres will fool the system too cut in too early.

If ABS was only dependent on wheel sensors, it would fail to detect cases where all four wheels lock up.
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Old 13th November 2008, 22:00   #14
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Quote:
Originally Posted by RedMM340 View Post
GTO,
Well yes, I guess I am a bit biased toward 4 wheel drive. Got the Forester a few weeks back, and just love it. An absolute blast in the hills, and great high speed highway cruiser. Can't beat a Forester for long trips.

I just might get some WRX STi mechanicals and make it rally car.
Wow, Gaurav, thats really neat. Now what Mods are you planning on the Forester

Quote:
Originally Posted by Alfa_Kilo View Post
ABS and TCS systems compare wheel rotation with linear acceleration to determine wheel slip/lockup. The tyre dia is very important for this to work properly.

If ABS was only dependent on wheel sensors, it would fail to detect cases where all four wheels lock up.
I didnt get you, can you elaborate, maybe on a different thread? If all 4 tyres are a slightly different OD, then there are no issues with TCS and ABS!
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Old 14th November 2008, 12:29   #15
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govigov, I have been keeping my eye on the foresters in Cochin for about 2 years now, and got this one at the right time. The model is 2004, price Rs.6.10 lakhs. It has done barely 46k only.
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