Outer Limits 4x4 Board

alien wrote:i thought it was the distance the hub face sits from the centre of the rim in millimetres? ie: -30 means the centre of the rim sticks out 30mm from the hub - so a 7" rim is 178mm wide, therefore 118.9mm of it sits outside the hub, with the other 59.1mm is inside the hub - the tyre sidwall then bulges out from that.

if an 8" rim has -30 offset then theres 71.6mm inside the hub face, and a 7" has -15 offset then theres 73.9mm inside the hub face - theyre about the same as far as spring rub is concerned other than how much the tyre sidewall bulges out of the rim.

...thats right isnt it?

Yeah, the offset is. But it was once, and to many people still is, backspace, which is measured from one side of the rim instead of using the middle as the starting point. Normally measured in inches.

So a 7" rim with 7" backspace is basically a cylinder with an end-cap, and the end cap mounts to the hub, correct? (or is it the other way around? which way is "back"?)

alien wrote:So a 7" rim with 7" backspace is basically a cylinder with an end-cap, and the end cap mounts to the hub, correct? (or is it the other way around? which way is "back"?)

Yeah, but I can't remember which way it is measured. Someone will post a link I'm sure. 2in backspace on a 7in rim would be measured from the inside (hub) I think and give 5in outwards from there.

Steve?

Unfortunately, backspacing is actually "theoretical" and almost impossible to measure properly

It is actually the distance from the hub mounting surface of the rim to the bead seat face on the inside of the rim.

A rough way is to put a straightedge across the back of the rim and measure from the hub mounting surface to the straightedge.

Don't measure from the front and work back, it's too confusing as a 7" rim is nearly 7.5 from edge to edge, and the thickness of the centre will screw up the results.

Zookimal, AFAIK your description of offset is correct, but it's lots of messing around with numbers to answer what we need to know - backspace is critical on Sierras, not rim width.

Steve.

There was a great sight that I learnt the ins and out's of PCD, offset etc etc from but buggered if I know what it is now.

hey bud thats a nice car what tires u got on that???

hey alien if i wanted 2 run them coopers discoverer stt armotek on 15x7 wat rim would i ask 4 is it 15x7 15 p???

i dunno i just went down the road to my local tyre place and said "i want 15x7's for my zuk".... check the bible for more info i spose...

Sierra 15' x 5.5" 10P

(from the bible)

yea ill have to call around lol with guards bbm want 440 for 2 fkin guards n a fitting kit what can i do to get rego???

clark rubber - buy flexi flare by the metre and tex screw it on =P

I just got some from there, about $13.00 per meter, looks good.

i want the bbm motorsport ones but they are a rip off

ive got goodyear wrangler mtr's and silent armours both on a 15x8 sunraiser running the -23 offset and have no problems with them rubbing on the springs. only rub points was the bar that runs out each side from the chassis rails, yes tires stick out a far bit but the 75 mm flexy flare is just wide enough at the top. let me know how you go with the other flares mine are effective but look shit.

ha ha would help if i told you they where 31x10.5