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Author Topic: 18" Tyre size  (Read 3879 times)

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MV6Matt

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18" Tyre size
« on: 27 February 2015, 20:33:08 »
Evening.

Am I right in recalling that the correct tyre size for the 18 x 8J wheels is 235/40/18?

If not let me know

Ta'n'stuff

Matthew
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05omegav6

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Re: 18" Tyre size
« Reply #1 on: 27 February 2015, 20:39:40 »
235/40/18 and 245/40/18 both officially authorised* tyre sizes for Omega 18"rims :y

Incidentally, 245/40/18s have the same rolling radius as 225/55/16...

*By Irmscher and GM rather then anyone here ;)
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Re: 18" Tyre size
« Reply #2 on: 27 February 2015, 23:14:56 »
Thanks Al

I was thinking OE rather than OOF

That's very helpful

Matthew
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Doctor Gollum

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Re: 18" Tyre size
« Reply #3 on: 28 February 2015, 00:29:08 »
There are a few minor rubbing issues with et30 8j 18 with 245 fitted. Go for the smaller size of the two I guess. It's a bit tight in the wheel house.

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05omegav6

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Re: 18" Tyre size
« Reply #4 on: 28 February 2015, 00:34:43 »
Quote from: MV6Matt on 27 February 2015, 23:14:56
Thanks Al

I was thinking OE rather than OOF

That's very helpful

Matthew
If you're ever fortunate enough to buy new Irmscher wheels, they come with a very comprehensive certificate of conformity/type approval with the correct offset, tyre size and pressures for any given application for that design... 8)
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05omegav6

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Re: 18" Tyre size
« Reply #5 on: 28 February 2015, 00:39:57 »
Quote from: Doctor Gollum on 28 February 2015, 00:29:08
There are a few minor rubbing issues with et30 8j 18 with 245 fitted. Go for the smaller size of the two I guess. It's a bit tight in the wheel house.
You're confusing the offsets...

Rubbing occurs with 245/40/18s when fitted to the Vectra Sportstars with an offset of ET38... The correct Omega offset being ET30 :y

My Stilas are an offset of ET33 with 245/40/18s and no rubbing :y
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05omegav6

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Re: 18" Tyre size
« Reply #6 on: 28 February 2015, 00:40:59 »
Quote from: Doctor Gollum on 28 February 2015, 00:29:08
There are a few minor rubbing issues with et30 8j 18 with 245 fitted. Go for the smaller size of the two I guess. It's a bit tight in the wheel house.
You're confusing the offsets...

Rubbing occurs with 245/40/18s when fitted to the Vectra Sportstars with an offset of ET38... The correct Omega offset being ET30 :y

My Stilas are an offset of ET33 with 245/40/18s and no rubbing :y
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Doctor Gollum

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Re: 18" Tyre size
« Reply #7 on: 28 February 2015, 00:51:03 »
Quote from: Taxi Al on 28 February 2015, 00:40:59
Quote from: Doctor Gollum on 28 February 2015, 00:29:08
There are a few minor rubbing issues with et30 8j 18 with 245 fitted. Go for the smaller size of the two I guess. It's a bit tight in the wheel house.
You're confusing the offsets...

Rubbing occurs with 245/40/18s when fitted to the Vectra Sportstars with an offset of ET38... The correct Omega offset being ET30 :y

My Stilas are an offset of ET33 with 245/40/18s and no rubbing :y

No master. Not confusiones, Smeagol has an omega remember. First hand experience here, and no mistakeses. Et30 rub the outside edge. Et38 rub the inside sidewall on the shock body. Unless master adjusts the camber away from the desired -1.10/1.15 to stop it of course. Et30 sport stars cone with a sticker for the top shock mount saying "warning. Camber must be set to -1.40 with these wheels. " I shitses you not.  Obviously -1.40 is opposing ridiculous so that ain't happening.

Et34 being between the two is the obvious answer :y
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05omegav6

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Re: 18" Tyre size
« Reply #8 on: 28 February 2015, 00:53:49 »
Ah, let you offses then...

Incidentally, new one has ET30s on it...
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Doctor Gollum

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Re: 18" Tyre size
« Reply #9 on: 28 February 2015, 00:55:48 »
Quote from: Taxi Al on 28 February 2015, 00:53:49
Ah, let you offses then...

Incidentally, new one has ET30s on it...

Haven't set it up yet though. So bet the camber is in excess of -1.20! Betses!
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Re: 18" Tyre size
« Reply #10 on: 28 February 2015, 00:58:02 »
Also needs the subframe set a bit more forward to keep the wheel Central for and aft.


This is all with a 245 tyreses mind.


It's not bad, just a scuff on full bump.
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05omegav6

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Re: 18" Tyre size
« Reply #11 on: 28 February 2015, 01:37:06 »
Irmscher suggest a tweak of the arch liner to give clearance... Only a matter of a couple of mm extra height required at the top of the wheel arch... Will have a play when I get to that...
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Re: 18" Tyre size
« Reply #12 on: 28 February 2015, 01:44:10 »
In what way?



....ses! :)
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05omegav6

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Re: 18" Tyre size
« Reply #13 on: 28 February 2015, 02:19:34 »
At  a guess by removing a 6"x2" strip from the outer edge of the arch liner where the wheel otherwise rubs... es...
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TheBoy

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Re: 18" Tyre size
« Reply #14 on: 01 March 2015, 22:13:40 »
235/40/18 GY F1 A2 rub on wheel arch shortly after any minor launch, proper braking and bum clenching cornering.
1'15 camber.
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