Omega Owners Forum

Chat Area => General Car Chat => Topic started by: Doctor Gollum on 04 July 2017, 11:28:15

Title: 18" wheel/tyre size question...
Post by: Doctor Gollum on 04 July 2017, 11:28:15
What widths are the staggered Irmscher Sportstars?

And what size tyres are you using?

Considering 245/45/18 on 8.5J fronts and 275/40/18 on 9.5J rears... Which look to give identical rolling radii, albeit -1.6% off the original size... But tyres seem a touch narrow for the wheel widths :-\

Incidentally not an Omega, so not interested in whether they rub or not, as they won't.
Title: Re: 18" wheel/tyre size question...
Post by: Field Marshal Dr. Opti on 04 July 2017, 12:04:10
What widths are the staggered Irmscher Sportstars?

And what size tyres are you using?

Considering 245/45/18 on 8.5J fronts and 275/40/18 on 9.5J rears... Which look to give identical rolling radii, albeit -1.6% off the original size... But tyres seem a touch narrow for the wheel widths :-\

Incidentally not an Omega, so not interested in whether they rub or not, as they won't.

Pretty big....what car is it for?
Title: Re: 18" wheel/tyre size question...
Post by: aaronjb on 04 July 2017, 12:30:16
Somewhat tyre dependent but, as an example - Toyo list T1-R 255/45R18 with an ideal width of 8.5J (8-9.5) and 275/40R18 with an ideal width of 9.5J (9-11), so those sizes sound fine to me.
Title: Re: 18" wheel/tyre size question...
Post by: Doctor Gollum on 04 July 2017, 13:09:17
Somewhat tyre dependent but, as an example - Toyo list T1-R 255/45R18 with an ideal width of 8.5J (8-9.5) and 275/40R18 with an ideal width of 9.5J (9-11), so those sizes sound fine to me.
:y

My 8J Stilas had 245/45/18s, which fitted nicely,  so on an 8.5J wheel, they will fit right but offer a touch less rim protection.

Similarly, at the back, the extra 30mm of tread width will offer decent rim protection on an inch wider wheel :-\

The key thing is that they MUST have the same rolling radius front/rear in order to prevent Abs/TC issues, which these two sizes do ;)

The tricky thing will be finding them in a suitable load rating ::)

A tyre thread sorted in less than a page :D
Title: Re: 18" wheel/tyre size question...
Post by: aaronjb on 04 July 2017, 15:55:48
The amount of rim protection is probably very dependent on tyre choice, too - I remember (many years back, not an Omega etc) swapping from Bridgestone to Goodyear (or maybe vice versa) and finding that they now rubbed on the spring.. same size on paper, different width in reality.
Title: Re: 18" wheel/tyre size question...
Post by: Mr Gav on 04 July 2017, 22:49:41
Bearing in mind that 9 inches is near enough 225mm then 245mm should be fine on 8.5J

Some tyres offer better rim protection than others anyway, the Dunlop sportmax rt`s had far better rim protection than the Goodyear Eagle F1`s.
Title: Re: 18" wheel/tyre size question...
Post by: cam.in.head on 04 July 2017, 22:54:05
according to various tyre and wheel charts by googling  245 is ideal for 8.5j and 275 is max for 9.5j wheels
Title: Re: 18" wheel/tyre size question...
Post by: Doctor Gollum on 04 July 2017, 22:58:53
Understood  :y

Ultimately the final choice of brand will boil down to availability of the appropriate load rating rather than rim protection...

according to various tyre and wheel charts by googling  245 is ideal for 8.5j and 275 is max for 9.5j wheels
I tend to use... https://www.miata.net/garage/tirecalc.html as my goto reference tool ;)
Title: Re: 18" wheel/tyre size question...
Post by: TheBoy on 05 July 2017, 17:09:50
Some tyres offer better rim protection than others anyway, the Dunlop sportmax rt`s had far better rim protection than the Goodyear Eagle F1`s.
That doesn't match my experience, with the F1s having huge rim protection...
Title: Re: 18" wheel/tyre size question...
Post by: Mr Gav on 05 July 2017, 21:45:39
Some tyres offer better rim protection than others anyway, the Dunlop sportmax rt`s had far better rim protection than the Goodyear Eagle F1`s.
That doesn't match my experience, with the F1s having huge rim protection...

Difficult to tell much from these photos but they do show the Dunlops to have a bit more rim protection, the close up of the Dunlop lower down gives you an idea on how much rim protection you get with them.

http://www.omegaowners.com/forum/index.php?topic=139530.0 (http://www.omegaowners.com/forum/index.php?topic=139530.0)
Title: Re: 18" wheel/tyre size question...
Post by: aaronjb on 06 July 2017, 10:55:03
Maybe TB is considering "bulging sides" as rim protection, rather than the little rim-protection rib on the Dunlops?

Y'know, the same way I confuse my bulging sides with manly curves..  ;D ;D