question about 31's and rims for camper

[MNBS 4x4]

Hi guys, I currently have a set of 30x9.5x15 on 15x7 rims on my camper trailer, as we are going away at christmas i have just noticed that the tyre walls are badly cracked and seriously need replaced, now I dont know what offset these current rims have but when i put a straight edge across the tyre on the inside and measure from the centre of the wheel( the flat part that bolts on) to the outside edge of the tyre i get 140mm which leaves a gap of around 30mm when the wheel is fitted from tyre to the chassis side of the camper

Can someone tell me what this measurement ( the 140mm part) would be with 31x10.5x15 on 15x8 cruiser offset rims. I have plenty of room for the tyres to come further out as they sit very far into the gaurds at the moment or would it be easier to stick a set of the 30's back on, would just like them to sit futher out as it looks a bit gay at the moment so figured i would need new rims anyway. the current 15x7's measure 100mm from centre to inside edge.



I hope my garbled message makes sense to somone.

[DUDELUX]

im not sure exactly what you were asking, but, go get a pair of 31 inch all terrains, you should be able to pick up a pair of second hand tyres in pretty good shape from your local tyre outlet for bugger all.
i have got all my 31s for my lux for next to nothing second hand from the local tyre joint. fitted and balanced for about $40-$50 each.

[Hobie18]

Why don't you just fit 31/10.5/15's to your current rims? I've always run 31/10.5/15's on 15 by 7's.

The 31 is only going to stick out an extra 12mm on either side which still leaves about 18mm between the tyre and chassis, although as tyres seem to vary quite a bit even of the same size this maybe +/- a bit.

Take your camper trailer down to the tyre place and ask them if you're not sure.

[chimpboy]

http://www.usacomp.com/terms.htm

OFFSET

The offset of a wheel is the measurement of the hub surface contact area in offset from the center line of the overall rim width of the wheel. A wheel whose hub surface contact area sits further towards the outside of the wheel than the center line has a positive offset. A wheel whose hub surface contact area sits further towards the inside of the wheel than the centerline has a negative offset


To determine the offset, the wheel must be measured accurately using the following steps:


(1) measure the overall rim width of the wheel.

(2) measure the T dimension (Backspace), which is the measurement from the hub surface contact area to the outside of the inner rim.

(3) divide the overall rim width by 2 which gives you the center line.

(4) subtract the center line (overall rim width/2) from the T dimension (Backspace).

(5) a negative answer means the wheel has a negative offset and a positive answer means the wheel has a positive offset

It might not hurt to get rims with more -ve offset, but on the other hand it sounds like you could put 31x10.5s on the rims you've got anyway.