VAUXHALL ASTRA GTE MK1 CAR PERFORMANCE SPORTS TURBO
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ET/ Offset help.

 
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Ash
Space Kadett
<font color=#FF8000>Space Kadett</font>


Joined: 29 Jul 2005
Posts: 4717
Location: Germany/Morecambe

PostPosted: Sat Nov 19, 2005 6:51 pm    Post subject: ET/ Offset help. Reply with quote

Hi all, Can someone explain how ET or Offset works please?
I have a general idea but i'd like it in writing.

I want to know because i'm looking for some new wheels but everything second hand is ET 20 - 35 but the original ET is 49, how do some of the Euro people manage to fit ET20's on there rides!? I'm in Germany you see so these offsets are easy to get hold of. Is it Deep dish but still a small width or something or have they had the lump hammer out?

What can i get away with, but i hate rubbing (to a point).

PS never go to Poland as it's Pooooooooo

FAO tricky - Been very busy but the Grill is on its way!!!
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Astra Legend
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Joined: 30 May 2005
Posts: 4790

PostPosted: Sat Nov 19, 2005 7:24 pm    Post subject: Reply with quote

Offset is how far away from the centre line of the wheel the mounting face is, eg ET49 means 49mm difference.

You can fit whatever offset you like but it will affect the handling but I think if you have spacers fitted it should help the wheel cleer anything necessary if not make it handle better than if they weren't there.
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Crafty
Astra Craftsman
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Joined: 18 Oct 2005
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PostPosted: Sun Nov 20, 2005 10:38 am    Post subject: Reply with quote

What stevewrote above is correct but be warned that vauxhalls use a NEGATIVE offset..
I'll try and explain it like this.. lets say we have a 8" wide rim, if you measured 4" in from the back edge (i.e. middle of the wheel) the mounting face would be another 49mm in again.. so lets say we have a 49mm offset wheel and you added a 2mm spacer your effective offset is now 29mm (negative). got it ?

The euros get ET20 wheels on their cars by using very small rims and have them protrude out of the arch (stictly speaking MOT failure here).

I think offset is a dumb way to measure it. The yanks use backspacing ( simply the measurement from the back egde of the wheel to the mounting face). The wheels I bought from my project where made to the backspacing and PCD I wanted. Mind you they are a tad more expensive that the average set of 17" here!


Last edited by Crafty on Sun Nov 20, 2005 5:17 pm; edited 1 time in total
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hot-hatch
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Joined: 29 May 2005
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PostPosted: Sun Nov 20, 2005 10:49 am    Post subject: Reply with quote

its not mark its steve laughing laughing
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Mark1GTE
wee mark
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Joined: 28 May 2005
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PostPosted: Sun Nov 20, 2005 2:42 pm    Post subject: Reply with quote

yeah i`m not that ugly laughing
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Astra Legend
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PostPosted: Sun Nov 20, 2005 2:44 pm    Post subject: Reply with quote

I'm not that old either
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Crafty
Astra Craftsman
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Joined: 18 Oct 2005
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PostPosted: Sun Nov 20, 2005 5:21 pm    Post subject: Reply with quote

sorry chaps I thought it was mark who had replied..

just to add the weird ET on vauxhalls of this age was due to some geometry setup they devised, it was meant to handle better and give the car stability during a puncture/run flat situation. If it ever worked who knows.

The subject of vauxhalls with "wrong" offsets is always a bone of contention.. some say its fine, others say it does affect handling.

I had ET35 rims on my old cav turbo, which were then changed to (I think) ET47, I felt it handled better and dealt with sunked roads better. A friend who drove the car sometimes also thought the same..
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PostPosted: Mon Nov 21, 2005 1:44 am    Post subject: Reply with quote

It's a common thought that they handle better... and they do, but then it depends how bad the roads are and how much 'character' in the handling you're willing to put up with.

Btw, Subarus run even an even wider offset than the older Vauxhalls
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