Omega Owners Forum

Chat Area => General Car Chat => Topic started by: geoffr70 on 31 May 2011, 23:10:57

Title: How to find out wheel offset/stud pattern etc
Post by: geoffr70 on 31 May 2011, 23:10:57

Hi peeps. I'm after gettig a spare wheel for my caravan. It's got 4 studs.

How do I find out what the offset is etc (don't even know what that means tbh).
Also, stuff like et39 or something, what does that mean? Basically I just need to know these figures so I can get a wheel that will fit the the bolt holes. Could i measure the centres? Thanks

Title: Re: How to find out wheel offset/stud pattern etc
Post by: aaronjb on 31 May 2011, 23:22:41

"ET<something>" is the offset: http://en.wikipedia.org/wiki/Offset_(wheel)

Measuring the centres of the bolt holes will get you the PCD (Pitch Circle Diameter)

Offset isn't easy to measure accurately, but might well be stamped on the wheel somewhere. Though there are instructions on the link for measuring & calculating it (accuracy just depends on how good you are with a ruler then)

Title: Re: How to find out wheel offset/stud pattern etc
Post by: geoffr70 on 31 May 2011, 23:28:16

One of those 'ahhhhh!' moments!

Thanks for that!  :y

Title: Re: How to find out wheel offset/stud pattern etc
Post by: Kevin Wood on 31 May 2011, 23:29:42

You will need to know a couple of parameters.

PCD - The diameter of the circle described by the wheel mounting studs. Easy to measure on a 4 stud wheel. Just measure the dimension between two opposite studs centre-to-centre. Normally combined with the number of studs - i.e. an Omega has a PCD of 5x110 (5 studs, 110mm PCD).

Centre diameter - the diameter of the central section of the hub which fits into the bore in the centre of the wheel.

Offset - this is your ET35 or whatever. Offset laterally between the centre of the tyre tread and the mounting face of the wheel hub. A positive offset moves the wheel further away from the hub.

Kevin

Title: Re: How to find out wheel offset/stud pattern etc
Post by: geoffr70 on 31 May 2011, 23:36:51

I understand now! Thanks

Title: Re: How to find out wheel offset/stud pattern etc
Post by: RobG on 31 May 2011, 23:47:45

http://www.nice-wheels.co.uk/pcdandoffset.html

Title: Re: How to find out wheel offset/stud pattern etc
Post by: Andy B on 31 May 2011, 23:59:58

Quote

....
Centre diameter - the diameter of the central section of the hub which fits into the bore in the centre of the wheel. .....

Caravan wheels often don't centre on the hub, it's the taper seat nuts that centralise them.  :y :y

Title: Re: How to find out wheel offset/stud pattern etc
Post by: o-meg-a on 01 June 2011, 02:00:13

and it may be easier to buy two matching steelies and replace both on the caravan

rather than trying to find one that matches the other on on there in terms of offset etc, as there are soo many variations.

Title: Re: How to find out wheel offset/stud pattern etc
Post by: Andy B on 01 June 2011, 08:48:58

Quote

..... as there are soo many variations.

I agree that there are many many different wheels around, but recent caravans use a limited number of them.
My caravan had no spare when I bought it, mine came from a local caravan breakers yard for £20 including an as new tyre.