Omega Owners Forum

Chat Area => General Discussion Area => Topic started by: waspy on 06 May 2008, 22:22:32

Title: Tyre size
Post by: waspy on 06 May 2008, 22:22:32
I'm not sure if this post should go in General Help, so Admins please move if you see fit.
I currently run "16 wheels with the correct tyre size & i would like to go up to "18. So what tyre size should i go for to maintain the correct circumference so as not to nock the speedo out.
Help appreciated
Title: Re: Tyre size
Post by: Debs. on 06 May 2008, 22:36:33
Try using this tyre-size cross-calculator it`s quite good and will formulate a percentile rotational change factor!  :y

http://www.miata.net/garage/tirecalc.html

Title: Re: Tyre size
Post by: Albatross on 06 May 2008, 22:39:31
Or this one...

http://www.club80-90syncro.co.uk/Syncro_website/TechnicalPages/TRC%20calculator.htm
Title: Re: Tyre size
Post by: Mr Skrunts on 06 May 2008, 22:41:02
According to the calc then I can run 225/55 on the front and 275/45 on the rear of my Elite


Yummy But will they fit the arches?
Title: Re: Tyre size
Post by: markey mark on 06 May 2008, 22:46:59
Quote
According to the calc then I can run 225/55 on the front and 275/45 on the rear of my Elite


Yummy But will they fit the arches?

yes mate no worries i have 265/30r19 on front and 285/35r19 on rear  :y
Title: Re: Tyre size
Post by: Albatross on 06 May 2008, 22:47:23
Quote
According to the calc then I can run 225/55 on the front and 275/45 on the rear of my Elite


Yummy But will they fit the arches?

What J are your rims? Is it OK to run 275 tyres on those rims?

I know that my facelift car is running 265x30x19 with an effective additional offset added of 15mm wider track on each rear corner. On the front is 235x35x19 with an additional 6mm per corner, so I'm pretty sure that the tyres will fit under the arches fine..




Title: Re: Tyre size
Post by: Mr Skrunts on 06 May 2008, 22:49:51
Rims are bog standard at the mo
Title: Re: Tyre size
Post by: Mr Skrunts on 06 May 2008, 22:51:52
Was gonna change the rims, but then again, what are the maximum size rubbers the standard rims will accomodate and what are the rims actual dimentions?
Title: Re: Tyre size
Post by: Albatross on 06 May 2008, 22:54:24
Quote
Quote
According to the calc then I can run 225/55 on the front and 275/45 on the rear of my Elite


Yummy But will they fit the arches?

yes mate no worries i have 265/30r19 on front and 285/35r19 on rear  :y

Are you sure Markey? That's a bit out of whack; front and rear tryes are different in rolling radius by quite a chunk there.

I must admit I thought you were running 265x30x19 on the rear. If you were running 285 tryes, in truth you should be running on a profile% of 25.

That is if they made 285x25x19 tyres. I haven't seen any. :-/

Title: Re: Tyre size
Post by: Albatross on 06 May 2008, 22:56:52
Quote
Was gonna change the rims, but then again, what are the maximum size rubbers the standard rims will accomodate and what are the rims actual dimentions?

If you don't get an answer, find the sixe stampted onto the inside of your rims. You may need a wire brish to clean it up to see.

You're looking for a J rating which is the rim-width in inches. Then the ET number is the offset. i.e. how far out the wheel is on the car when bolted on. The lower the ET number the wider the track. The Omega is ideally ET 35-38, I think. :-/
Title: Re: Tyre size
Post by: Debs. on 06 May 2008, 22:59:16
Quote

Are you sure Markey? That's a bit out of whack; front and rear tryes are different in rolling radius by quite a chunk there.

I must admit I thought you were running 265x30x19 on the rear. If you were running 285 tryes, in truth you should be running on a profile% of 25.

That is if they made 285x25x19 tyres. I haven't seen any. :-/

I wonder what percentile (front/rear) rotational difference would become 'visible' to the T.C/ABS system?
Title: Re: Tyre size
Post by: Kenny on 07 May 2008, 00:15:56
??
Title: Re: Tyre size
Post by: waspy on 07 May 2008, 06:46:29
Thank you all for your help. I shall some calculations later  :)
Title: Re: Tyre size
Post by: bob.dent on 07 May 2008, 13:29:19
Quote
Quote
According to the calc then I can run 225/55 on the front and 275/45 on the rear of my Elite


Yummy But will they fit the arches?

yes mate no worries i have 265/30r19 on front and 285/35r19 on rear  :y

Jeez, they must be bl00dy huge!! :o I have 265/40/17 on the rear of mine and I thought they were wide. ::)
Title: Re: Tyre size
Post by: Mr Skrunts on 07 May 2008, 14:30:15
Quote
Quote
Quote
According to the calc then I can run 225/55 on the front and 275/45 on the rear of my Elite


Yummy But will they fit the arches?

yes mate no worries i have 265/30r19 on front and 285/35r19 on rear  :y

Jeez, they must be bl00dy huge!! :o I have 265/40/17 on the rear of mine and I thought they were wide. ::)


According to the 1st calculator then you are actually reading 1.5% too fast on your speedo.  Speedo = 60 mph / Actual = 59.1 mph.

At least its on the right side of the law
Title: Re: Tyre size
Post by: Mr Skrunts on 07 May 2008, 14:34:34
Marky marks tires are actually propelling him along at 62.6 mph @ an indicated 60 mph based on both tyre sizes being compared to 225/55/16 on the calc.

http://www.miata.net/garage/tirecalc.html
Title: Re: Tyre size
Post by: Mr Skrunts on 07 May 2008, 14:37:02
225/55/16 equates to 285/30/19 = 0.0% Actual Speed Difference.


Clever stuff this calc.
Title: Re: Tyre size
Post by: Martin_1962 on 07 May 2008, 15:09:37
Quote
Marky marks tires are actually propelling him along at 62.6 mph @ an indicated 60 mph based on both tyre sizes being compared to 225/55/16 on the calc.

http://www.miata.net/garage/tirecalc.html


That cancels out the deliberate inacuracies of the speedo
Title: Re: Tyre size
Post by: Mr Skrunts on 07 May 2008, 15:10:45
Thats a good way to look at it.   :y