The Subaru SVX World Network   SVX Network Forums
Live Chat!
SVX or Subaru Links
Old Lockers
Photo Post
How-To Documents
Message Archive
SVX Shop Search
IRC users:

Go Back   The Subaru SVX World Network > SVX Main Forums > Technical Q & A

Reply
 
Thread Tools Display Modes
  #1  
Old 05-12-2008, 08:57 AM
svxistentialist's Avatar
svxistentialist svxistentialist is offline
Jersey Girl
Alcyone Gold Contributor
 
Join Date: Mar 2001
Location: Ireland
Posts: 8,270
Send a message via Skype™ to svxistentialist
Registered SVX
Rolling radius mismatch; your opinions on possible harm

My Jersey Girl came with very poor tyres, perished rubber and generally in very poor condition.

These I have replaced with the tyres from Black Betty, which are Dunlop Sport 2000E standard fitment 225/50 ZR 16. Betty had recently passed an MOT and two new tyres were mandatory, so effectively I have four tyres the exact same fitment, two are brand new, two are part worn, possibly half worn I would say.

The way they are fitted is with both new tyres on the right side, and both worn tyres on the left side. I did not want the front and rear axles having different rolling radii.

This is my question; does anybody think this difference in rolling radius left to right will cause detrimental effects at the gearbox?

The actual measured radii in cms is 31.6 on the left side and 31.8 on the right side. [The rolling radius figures will be lower than these once weight is applied, but there should be the same ratio proportions]

My own opinion is it should be OK, as it will be the same to the gearbox as if the car is turning right all the time [the left hand wheels make more revolutions that the right side do, just as when turning, and the diff should be able to cope with the difference]

I would like your opinions. Am I being naive? There are two solutions;shave off half the rubber on the new tyres; or buy two new ones and throw away the half worn ones. Either solution involves throwing out about €160 worth of rubber [$240 in your money] and I would rather not waste if there are no ill effects.

Joe
__________________
Black Betty [Bam a Lam!] '93 UK spec, still languishing Betty
Jersey Girl Silver '92 UK [Channel Isles] 40K Jersey Girl @ Mersea
Candy Purple Honda Blackbird Plum Dangerous
White X2 RVR Mitsubishi 1800GDI. Vantastic

40,000 miles Jersey Girl
Reply With Quote
  #2  
Old 05-12-2008, 09:12 AM
Hocrest's Avatar
Hocrest Hocrest is offline
Freezepop's are Awesome!!!!
Subaru Silver Contributor
 
Join Date: Oct 2003
Location: Pittston, PA
Posts: 5,334
Send a message via AIM to Hocrest
Will the side/side mismatch cause an issue with the rear LSD???
__________________
Dave
- 03 Baja - 92 SVX - 86 Brat - 08 OB 3.0
Reply With Quote
  #3  
Old 05-12-2008, 09:18 AM
svxistentialist's Avatar
svxistentialist svxistentialist is offline
Jersey Girl
Alcyone Gold Contributor
 
Join Date: Mar 2001
Location: Ireland
Posts: 8,270
Send a message via Skype™ to svxistentialist
Registered SVX
I don't know Dave. That's one of the reasons I asked the question and quoted the actual radii. I thought perhaps one of the engineers on board here that understood rotational forces would venture an opinion.

Joe
__________________
Black Betty [Bam a Lam!] '93 UK spec, still languishing Betty
Jersey Girl Silver '92 UK [Channel Isles] 40K Jersey Girl @ Mersea
Candy Purple Honda Blackbird Plum Dangerous
White X2 RVR Mitsubishi 1800GDI. Vantastic

40,000 miles Jersey Girl
Reply With Quote
  #4  
Old 05-12-2008, 04:16 PM
oab_au oab_au is offline
Registered User
Subaru Gold Contributor
 
Join Date: Mar 2001
Location: Coffs Harb, Australia.
Posts: 5,032
Significant Technical Input Registered SVX
Quote:
Originally Posted by svxistentialist View Post
I don't know Dave. That's one of the reasons I asked the question and quoted the actual radii. I thought perhaps one of the engineers on board here that understood rotational forces would venture an opinion.

Joe
I think it would be better to fit the two new to the front, the worn to the rear. The VTD won't be as worried about the difference as the rear diff that will heat up due to the difference. We have had a few rear end fires.

Harvey.
__________________
One Arm Bloke.
Tell it like it is!

95 Lsi. Bordeaux Pearl, Aust. RHD.149,000Kls Subaru BBS wheels.
97 Liberty GX Auto sedan. 320,000Kls.
04 Liberty 30R Auto Premium. 92.000kls.
Reply With Quote
  #5  
Old 05-12-2008, 05:11 PM
svxistentialist's Avatar
svxistentialist svxistentialist is offline
Jersey Girl
Alcyone Gold Contributor
 
Join Date: Mar 2001
Location: Ireland
Posts: 8,270
Send a message via Skype™ to svxistentialist
Registered SVX
Would you think so Harvey?

It's doing very little miles at present, so I have not managed to check temperatures at the LSD.

It would mean swapping the tyres around on the wheels, but that would not be too difficult, I suppose.

Thanks

Joe
__________________
Black Betty [Bam a Lam!] '93 UK spec, still languishing Betty
Jersey Girl Silver '92 UK [Channel Isles] 40K Jersey Girl @ Mersea
Candy Purple Honda Blackbird Plum Dangerous
White X2 RVR Mitsubishi 1800GDI. Vantastic

40,000 miles Jersey Girl
Reply With Quote
  #6  
Old 05-12-2008, 05:27 PM
TomsSVX's Avatar
TomsSVX TomsSVX is offline
Maniac modifier
 
Join Date: Dec 2003
Location: Branchburg, New Jersey
Posts: 15,489
Registered SVX Classic SVX
Harvey is right. I have heard fire stories from the rear diff but it is really only possible to get the rear that hot by overworking the LSD w/ mismatched tires... So no diff fires please Always keep equal diameter tires on the axles

Tom
Reply With Quote
  #7  
Old 05-19-2008, 08:05 AM
b3lha's Avatar
b3lha b3lha is offline
Phil & Belha
 
Join Date: Aug 2001
Location: Alcyone Limited, Buckinghamshire UK
Posts: 2,671
I'm no gearbox expert, but I reckon mismatched tyres on the same axle is asking for trouble.

I recently had two punctures on my green SVX. I swapped on two wheels from another SVX. But when driving it I could hear an unusual whirring noise from either the trans or the front diff. So I put the undamaged originals on the back and bought two new ones for the front and the noise went away.

As Harvey said, you should swap them around and put the new ones on the front. Then we can tease you about two of your wheels being on backwards.
__________________
Subaru ECU and TCU Website
1992 Alcyone SVX Version L
1992 Alcyone SVX Version L
1994 Alcyone SVX S40-II
2004 Subaru Legacy 2.5 SE Sports Tourer
1996 Subaru Legacy 2.2 GX Wagon
1988 Subaru Justy J12 SL-II
Reply With Quote
  #8  
Old 05-19-2008, 01:10 PM
svxistentialist's Avatar
svxistentialist svxistentialist is offline
Jersey Girl
Alcyone Gold Contributor
 
Join Date: Mar 2001
Location: Ireland
Posts: 8,270
Send a message via Skype™ to svxistentialist
Registered SVX
Thanks for the advice guys.

Based on Harvey's reply I took an urgent view on the move. I swapped around two of the tyres. I now have the two new tyres on front, plus the two possibly half worn ones on the back. Each axle even.

In addition I have had the 4 wheel alignment done by laser. Car drives very well now.

Phil, no chance of teasing me for now, I have all wheels rotating backwards as they are supposed to do.

However, I am thinking of changing them all around so they all appear to be rotating forwards, as this seems to drive the pedants and the nerds into apoplectic fits, for some reason. That'll give you a chance to tease me and see if I give a flying f.. er emmm, ehhh see if I care.

__________________
Black Betty [Bam a Lam!] '93 UK spec, still languishing Betty
Jersey Girl Silver '92 UK [Channel Isles] 40K Jersey Girl @ Mersea
Candy Purple Honda Blackbird Plum Dangerous
White X2 RVR Mitsubishi 1800GDI. Vantastic

40,000 miles Jersey Girl
Reply With Quote
  #9  
Old 05-19-2008, 01:31 PM
ensteele's Avatar
ensteele ensteele is offline
Betcha can't buy just one!
Alcyone Gold Contributor
 
Join Date: Jan 2002
Location: Burlington, WA
Posts: 19,552
Send a message via ICQ to ensteele Send a message via Yahoo to ensteele Send a message via Skype™ to ensteele
Registered SVX Classic SVX
Joe - your wheels are on backwards!!!!!
__________________
.
Earl .... ... .... ><SVX(*>

Subaru Ambassador

[COLOR=”silver”]1992 Tri Color L[/COLOR] ~45K (06/91) #2430
1992 Dark Teal LS-L ~184K (05/91) #0739
1992 Claret LS-L ~196K (05/91) #0831
1992 Pearl LS-L ~103K (06/91) #1680
1992 Pearl LS-L ~151K (06/91) #2229
1992 Dark Teal LS ~150K (07/91) #3098 (parts car)
1992 White LS-L ~139K (08/92) #6913
1993 25th AE ~98K (02/93) #164
1993 25th AE ~58K (02/93) #176
1993 25th AE ~107K (02/93) #215
1993 25th AE ~162K (02/93) #223
1994 Laguna Blue Pearl LSi ~124K (1/94) #2408
1994 Laguna Blue Pearl LSi ~144K (10/93) #1484
1994 Laguna Blue Pearl LSi ~68K (10/93) #1525
1994 Barcelona Red LSi ~46K (02/94) #2624
1994 Pearl LSi ~41K (12/93) #1961
1995 Bordeaux Pearl LSi ~70K (02/95) #855
1996 Polo Green LSi ~95K (03/96) #872
1997 Bordeaux Pearl LSi ~55K (08/96) #097
2003 Brilliant Red LS1 Convertible ~29K (04/03) #8951
1999 Magnetic Red LS1 Coupe ~33K (04/99) #6420

My Email | Old Locker | New Locker | Picture of 15 of the 19
Reply With Quote
  #10  
Old 05-19-2008, 02:15 PM
svxistentialist's Avatar
svxistentialist svxistentialist is offline
Jersey Girl
Alcyone Gold Contributor
 
Join Date: Mar 2001
Location: Ireland
Posts: 8,270
Send a message via Skype™ to svxistentialist
Registered SVX
Quote:
Originally Posted by ensteele View Post
Joe - your wheels are on backwards!!!!!
Not just yet Earl, I'm thinking about it!

__________________
Black Betty [Bam a Lam!] '93 UK spec, still languishing Betty
Jersey Girl Silver '92 UK [Channel Isles] 40K Jersey Girl @ Mersea
Candy Purple Honda Blackbird Plum Dangerous
White X2 RVR Mitsubishi 1800GDI. Vantastic

40,000 miles Jersey Girl
Reply With Quote
  #11  
Old 05-19-2008, 09:05 PM
odepaj's Avatar
odepaj odepaj is offline
Killer of threads
 
Join Date: Aug 2004
Location: San Antonio, Texas
Posts: 1,926
Registered SVX
.2cm difference in rolling radius is minimal, and if you put the tires that measured 31.8cm on the front, the extra weight will bring them down some (more so then the 31.6cm tires on the back due to more weight in front).

So I would say running mismatched front to back will be better than left to right, in your case.




Dustin
__________________
-Dustin

1992 Ebony LS-L w/191k miles Mods: a few and acouple more

1995 Brilliant Red L/AWD w/154k miles Mods: Stebro catback exhaust, K&N drop in filter, ECUtune ST1v5, 4.44, lots of JDM goodies

1992 Pearly LS-L w/154k miles Sold Mods: 4.11, rust

2008 DGM Legacy spec.B w/245k miles Mods: Cryotune Stage3, VF52, bushings galore, STi pink springs, Bilstein HDs


My Locker

The only man alive who drives three "Subu SVS's".......according to my insurance company
Reply With Quote
  #12  
Old 05-20-2008, 02:17 AM
svxistentialist's Avatar
svxistentialist svxistentialist is offline
Jersey Girl
Alcyone Gold Contributor
 
Join Date: Mar 2001
Location: Ireland
Posts: 8,270
Send a message via Skype™ to svxistentialist
Registered SVX
That's actually the way they are now fitted Dustin.

I'll keep you posted on how they go.

Thanks for the advice, much appreciated.

Joe
__________________
Black Betty [Bam a Lam!] '93 UK spec, still languishing Betty
Jersey Girl Silver '92 UK [Channel Isles] 40K Jersey Girl @ Mersea
Candy Purple Honda Blackbird Plum Dangerous
White X2 RVR Mitsubishi 1800GDI. Vantastic

40,000 miles Jersey Girl
Reply With Quote
  #13  
Old 05-20-2008, 02:30 AM
SSSVX's Avatar
SSSVX SSSVX is offline
One teal and One yellow
 
Join Date: Aug 2001
Location: WV
Posts: 2,687
The front tires are going to wear out faster than the rear tires...

After few, few thousands of miles, they'd be getting closer...
__________________
-SSSVX

92 LS-L TEAL since Aug '01
92 LS-L YELLOW since Mar '05
Reply With Quote
  #14  
Old 05-20-2008, 05:41 AM
CorSVXette's Avatar
CorSVXette CorSVXette is offline
SVX- My daily driving Corvette
 
Join Date: Sep 2007
Location: Howard Beach, NY
Posts: 598
Send a message via AIM to CorSVXette
Classic SVX
Quote:
Originally Posted by TomsSVX View Post
Harvey is right. I have heard fire stories from the rear diff but it is really only possible to get the rear that hot by overworking the LSD w/ mismatched tires... So no diff fires please Always keep equal diameter tires on the axles

Tom
So if mismatched tires cause diff fires, why did Subaru give us a donut as a spare. That being said, if I get a flat, where would be the best place to put the donut? ( and don't say in my mouth)
__________________
Paul
1969 Corvette
1995 SVX L Safety Option Package, HID's & Awsome Braking (Svxfilies/TomsSVX), JDM Clear Corners, JDM Boxer Engine cover, Transmission Cooler, AND NOW JDM FOLDING MIRRORS!
1995 Corolla
2003 Highlander
Reply With Quote
  #15  
Old 05-20-2008, 06:24 AM
TomsSVX's Avatar
TomsSVX TomsSVX is offline
Maniac modifier
 
Join Date: Dec 2003
Location: Branchburg, New Jersey
Posts: 15,489
Registered SVX Classic SVX
always put the donut on the front axle

Tom
Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT -6. The time now is 05:13 AM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2024, vBulletin Solutions, Inc.
© 2001-2015 SVX World Network
(208)-906-1122