Jump to content
LegacyGT.com

Do you need to replace all of your tires?? Read first before making a thread.


blackfang
 Share

Recommended Posts

I'm a little confused.. reason being my 05 lgt.. it is a 5eat and the split ratio front/rear is different..

 

So my question is.. lets say the back two tires are the same diameter.. and the front two are the same diameter.. but compared from front to back they are different.

 

So how would running lets say a new set on the front and a used set on the back affect anything? I could see if you ran 1 new and 1 used on each side of the rear and wear the rear diff over time..

 

The same applies and makes no difference, and here is why.

 

Your AWD system does have a VTD set up. It will split up the ratio 45/55. However, it still operates the same manner as a continuous AWD, maybe a little better though. So if a set of tires are larger in circumference than another say the rear, the system sees they are spinning faster than the other set. It will do it's job and transfer the torque to the wheels that are not spinning as fast. This will cause damage to the clutches because the vehicle is not really stuck at all and burns the clutches/solenoids out. The AWD system just thinks it is.

 

There is a thread on here that describes all the types of AWD that comes with our cars.

 

Edit- Found it

http://www.legacygt.com/forums/showthread.php?t=48112

Edited by blackfang
[SIZE=1][URL="http://public.fotki.com/blackfang/"]Pics[/URL] [B]08 KawasakiZZR 600- exhaust and other mods 98 Camaro Z/28 HT- some mods......street/strip car 07 Legacy 2.5i- SPT exhaust...daily driver[/B][/SIZE]
Link to comment
Share on other sites

  • 1 month later...
  • Replies 58
  • Created
  • Last Reply

Top Posters In This Topic

So I had a tire blow out on the 401 last weekend (front passanger) in the middle of nowhere. Luckely I pulled of the highway right behind a service pick-up. While I was putting my spare on, he called his garage to see if they had my tire size. They did, so I followed him.

 

I get there and they say that they only have a used one, same size...ok...

I needed to get to Toronto fast for a wedding so I accepted. They installed it and put it rear passanger side (to not screw up my handling).

 

So I get back from my weekend in Toronto and after reading messages on this board I'm not too sure about it anymore. Since then, I have travelled a total of 1500 km.

 

I have approximatlely 8000 km on my tires.

 

I have 3 x Yokohama Advan A83 88V with 8000 km

and 1 x Michelin HX MXM4 93V with ??? km + 1500 km

all are 205/50R17

I checked Tirerack.com and when new, both of these tires have the same diameter.

 

So should get a new tire (same as other three and shave it if needed) or keep this one?

Link to comment
Share on other sites

  • 1 month later...
Bump being I see some new threads about this, but it is not stickied here(in the 2.5i FAQ)
[SIZE=1][URL="http://public.fotki.com/blackfang/"]Pics[/URL] [B]08 KawasakiZZR 600- exhaust and other mods 98 Camaro Z/28 HT- some mods......street/strip car 07 Legacy 2.5i- SPT exhaust...daily driver[/B][/SIZE]
Link to comment
Share on other sites

  • 2 months later...
Folks, do NOT let the 1/32nds or 3/32nds rule fool you. That is not the correct method and it will cost you transfer clutches.

 

[...]

 

If you do not do this, you are increasing the chances of damaging the transfer clutches/center diff or prematurely wearing them out on your awd.

 

I'm pretty sure you meant "transfer cases."

Link to comment
Share on other sites

I'm pretty sure you meant "transfer cases."

I am pretty sure I meant transfer clutches;). Subaru's are not 4x4's and do not have a transfer case. They do have transfer clutch's/center differential that are in the transmission that control the transfer of power to the f/r wheels.:)

[SIZE=1][URL="http://public.fotki.com/blackfang/"]Pics[/URL] [B]08 KawasakiZZR 600- exhaust and other mods 98 Camaro Z/28 HT- some mods......street/strip car 07 Legacy 2.5i- SPT exhaust...daily driver[/B][/SIZE]
Link to comment
Share on other sites

COMPONENTS THAT MAKE UP SYMMETRICAL AWD

 

Here is what comprises Subaru Symmetrical AWD, using Outback as an example. The main system components are the engine, transmission, transfer case, propeller shaft (driveshaft), and rear differential – all parts of the drivetrain.

 

http://www.drive.subaru.com/Win09/Win09_ItsWhatMakes.htm

 

That said, thanks for introducing the term "transfer clutch" to my vocabulary.

Link to comment
Share on other sites

http://www.drive.subaru.com/Win09/Win09_ItsWhatMakes.htm

 

That said, thanks for introducing the term "transfer clutch" to my vocabulary.

I am pretty sure I know what is part of a Subaru's all wheel drive.;) Sometimes literature that is being published for the public that describes things tend to use basic terms so that the average person "gets it". They do not go that far in depth using the correct technical terminology. The "transfer case" also called the extension case and is what is in the back of the transmission. Infact the Service manual doesn't call it a transfer case.

 

Inside that transfer case(we will call it that for your sake of argument) is where the transfer duty solenoid, transfer clutches and transfer driven bearings are. The transfer clutches are responsible for controlling the correct ratio with the help of the duty solenoid, the valve and fluid.

 

The AWD transfer system( we will use the 4EAT as an example) uses a hydraulic multi plate clutch system(IIRC there are 5 of them) that is controlled by the TCM through a control valve. Hope this clears things up for you :) Now do we still want to debate what is inside the transmission or keep this on topic so it helps other enthusiasts so they correctly address replacing tires and how it relates to the AWD

Edited by blackfang
[SIZE=1][URL="http://public.fotki.com/blackfang/"]Pics[/URL] [B]08 KawasakiZZR 600- exhaust and other mods 98 Camaro Z/28 HT- some mods......street/strip car 07 Legacy 2.5i- SPT exhaust...daily driver[/B][/SIZE]
Link to comment
Share on other sites

  • 11 months later...

Subaru has recently come out with this statement, in their Dec 2010 Tech Tips Newsletter. All tire circumferences need to be within 0.25 inch of each other.

 

"The Techline continues to receive calls from Technicians who have performed all types of unsuccessful repairs to transmissions with a “binding on turns” concern from the Customer. One of the first questions we will ask is whether or not the tire circumferences have been measured. All too often the answer is no. It is extremely important when diagnosing a transfer clutch-related concern, the tires must be one of the first variables you rule out. Remember, all 4 tires should be within approximately ¼" of each other in circumference when measured at the center of the tread. Otherwise, binding issues can result (or re-occur) due to the ratio imbalance caused by mis-matched tires. A quick keyword search on STIS of “Binding on Turns” will return a list of other bulletins and TIPS articles on this subject"

 

http://www.subaruoutback.org/forums/66-problems-maintenance/30110-tire-circumference-spec-confirmed-subaru-techtips.html

Edited by outahere
Link to comment
Share on other sites

The "transfer case" also called the extension case and is what is in the back of the transmission. Infact the Service manual doesn't call it a transfer case.

 

The parts catalog calls it a transfer case - 33101AA520.

Link to comment
Share on other sites

  • 4 weeks later...
So I had a tire blow out on the 401 last weekend (front passanger) in the middle of nowhere. Luckely I pulled of the highway right behind a service pick-up. While I was putting my spare on, he called his garage to see if they had my tire size. They did, so I followed him.

 

I get there and they say that they only have a used one, same size...ok...

I needed to get to Toronto fast for a wedding so I accepted. They installed it and put it rear passanger side (to not screw up my handling).

 

So I get back from my weekend in Toronto and after reading messages on this board I'm not too sure about it anymore. Since then, I have travelled a total of 1500 km.

 

I have approximatlely 8000 km on my tires.

 

I have 3 x Yokohama Advan A83 88V with 8000 km

and 1 x Michelin HX MXM4 93V with ??? km + 1500 km

all are 205/50R17

I checked Tirerack.com and when new, both of these tires have the same diameter.

 

So should get a new tire (same as other three and shave it if needed) or keep this one?

 

Keep it, you will be fine.

 

I blew a tyre on the 40, and drove for over 200 km on the temporary spare before fitting a replacement.

 

I got a partially used Eagle F1 from a guy on the Montreal forum, hardly any wear. The other 3 tyres had 30,000 kms on them and were over 50% worn.

 

No issues at all.

Link to comment
Share on other sites

Thanks for the thread. Tire has a flat that can't be fixed - was just going to replace the 1 tire now I know I gotta replace all 4. Ohh well, $$$ - but I guess I'd rather not have AWD transmission issues.

 

Re-read the thread. Especially the part about shaving down a (one) new tire to match the remaining three in circumference. Much, much less expensive than buying four new tires (four times less expensive:)). If they are already significantly worn, then just get four new, you would be soon enough anyways.

Link to comment
Share on other sites

Subaru has recently come out with this statement, in their Dec 2010 Tech Tips Newsletter. All tire circumferences need to be within 0.25 inch of each other.

 

"The Techline continues to receive calls from Technicians who have performed all types of unsuccessful repairs to transmissions with a “binding on turns” concern from the Customer. One of the first questions we will ask is whether or not the tire circumferences have been measured. All too often the answer is no. It is extremely important when diagnosing a transfer clutch-related concern, the tires must be one of the first variables you rule out. Remember, all 4 tires should be within approximately ¼" of each other in circumference when measured at the center of the tread. Otherwise, binding issues can result (or re-occur) due to the ratio imbalance caused by mis-matched tires. A quick keyword search on STIS of “Binding on Turns” will return a list of other bulletins and TIPS articles on this subject"

 

http://www.subaruoutback.org/forums/66-problems-maintenance/30110-tire-circumference-spec-confirmed-subaru-techtips.html

 

What are the symptoms of "binding on turns"? I recently had a tire develop a bulge, and my spare (I traded 2 used RE92s for 1 used MPS A/S, same as the 4 I had). I went to get the spare shaved to match, and the guy said it was within 1/4". However, hypocariac me (always think something's wrong with my car :lol:) is now wondering if I'm having issues due to this..

Link to comment
Share on other sites

  • 2 weeks later...
ok i'm drunk, but i'm thinking of my car LOL. no i'm not driving but anyway i have 18's and i don't have a full sized spare and that worries me on how useless it would be if i had a flat. i have a 2.5i 5mt so no rear LSD. ok so our awd system is very sensitive to the tire's circumference, but that got me thinking; don't the inside wheels spin slower when we are turning? isn't this similar or worse than to having different a tire that slightly different? if i took my car to a nascar race my diff will eventually blow up?
Link to comment
Share on other sites

ok i'm drunk, but i'm thinking of my car LOL. no i'm not driving but anyway i have 18's and i don't have a full sized spare and that worries me on how useless it would be if i had a flat. i have a 2.5i 5mt so no rear LSD. ok so our awd system is very sensitive to the tire's circumference, but that got me thinking; don't the inside wheels spin slower when we are turning? isn't this similar or worse than to having different a tire that slightly different? if i took my car to a nascar race my diff will eventually blow up?

 

I believe you're allowed 1/4 inch difference in circumference between tires. I was VERY lucky that my (full-size) spare was exactly the right size when one of my tires developed a bulge..

Link to comment
Share on other sites

  • 6 months later...
The same applies and makes no difference, and here is why.

 

Your AWD system does have a VTD set up. It will split up the ratio 45/55. However, it still operates the same manner as a continuous AWD, maybe a little better though. So if a set of tires are larger in circumference than another say the rear, the system sees they are spinning faster than the other set. It will do it's job and transfer the torque to the wheels that are not spinning as fast. This will cause damage to the clutches because the vehicle is not really stuck at all and burns the clutches/solenoids out. The AWD system just thinks it is.

 

There is a thread on here that describes all the types of AWD that comes with our cars.

 

Edit- Found it

http://www.legacygt.com/forums/showthread.php?t=48112

 

From that other thread:

----------------------

In normal operation, power is distributed equally to the front and rear wheels. Plates are alternately attached to the front and rear output shafts inside the viscous coupling. When a rotational difference occurs between the front and back wheels, the plates inside the viscous housing shear inside the contained fluid (a type of silicone) heating it and causing the fluid to thicken. The thickened fluid causes the plates to transfer torque from those that rotate faster (the slipping wheels) to the plates that rotate slower (the wheels with the best traction).

 

This no-maintenance system is simple, compact and virtually invisible in its operation. The system can distribute torque from a 50:50 torque split for maximum traction to mostly front or rear wheel drive.

 

-----------------------------------------

 

Two questions:

 

1. is this silicon fluid contained inside the housing in a secondary chamber with no access externally? I know my tranny is filled with 75-90 gear oil and when you remove the drive shaft it runs right out the back, so it seems to all be one chamber inside.

 

2. is there a way to tap into the control system and set up an indicator light that could tell you when clutches are engaging? That way if you see it going on all the time when you are not on a slippery surface you would know something was going on.

 

I just replace a tranny on a 95 Legay L wagon that had been run with different wear level tires on the front and rear. Seems there is a lot of iffiness to measuring the circumference to within 1/4" (tire pressure, vehicle weight, on or off the car...) and a positive feedback that the clutches aren't over active would be comforting.

 

Thanks.

Link to comment
Share on other sites

  • 2 weeks later...

So I just replaced all 4 tires after blowing two and having the other two out of the tread depth parameters. My new issue is a couple small bends on the two rims that the tires that hit the pothole. The tires balance, the car is aligned, but I have some shimmy (now in the ass-end(save the jokes)) when I get up to speed.

 

My question is like the tread depths, will the shimmy have any effect on my drivetrain or AWD system? I log about 300 m/week, mostly back roads. The tire shop offers wheel straightening for $100/ tire but its 50/50 success rate and the could still crack the rim. I found some reconditioned rims for $200/wheel. Can I live with the shimmy or will that cause just as much damage?

Link to comment
Share on other sites

  • 3 months later...

I was hoping to hear an answer to a previous question: Which tires wear out faster? I "thought" that my front tires wore out faster, and the only little things I can find say that they do via a google search, but I know all AWD cars aren't made equal.

 

I'm replacing two tires that are within tolerance of all wheels, and I'm thinking to put the meatier ones on the front. Can anyone confirm for me that the front tires wear out (probably mostly due to steering and more weight from the engine) So that the thicker ones will wear down faster to eventually match the rears before I even worry about rotating them?

Link to comment
Share on other sites

  • 1 year later...
I had an unrepairable blow out this weekend. The tires i bought last year, and 10k miles ago are discontinued. I've found the same make and size, but the tread is a little different. will this mess up my Diff? or do i need 4 new tires?
Link to comment
Share on other sites

I'd say measure the rolling circumference like the first post of the thread says. Matching to within the spec is what is important. The transfer clutch cannot tell what tread pattern your tires have, only if they travel unmatched distances for each revolution.
Link to comment
Share on other sites

I had an unrepairable blow out this weekend. The tires i bought last year, and 10k miles ago are discontinued. I've found the same make and size, but the tread is a little different. will this mess up my Diff? or do i need 4 new tires?

 

I'd look around to see if you can't find the same ones.

 

What matters to the differential is the ROLLING circumference of tires, when fully weighted on the car. Between different makes of tires, you have no guarantee that the tires will flex the same.

 

You might be ok, if you can find the newer variant of the same tire, but even that is potentially pushing your luck. Unfortunately, there's no good indicator of how much is too much variation?

 

Also, what year/model Subaru? Newer Subaru's (2010+) will be a little more tolerant since they have open differentials in the front and rear.

Link to comment
Share on other sites

  • 4 weeks later...

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
 Share




×
×
  • Create New...

Important Information

Terms of Use