Lonnie P

Stephen,
I was going to let this thread die, but I see it is taking on a life of its own.

I retrospect, I will actually defend your thoughts in this post.

Years back, wheels were measured using the exact method which you originally stated. Wheels were largely zero or negative offest & brakes were not nearly as large as they are today. This made an actual backside measurement less important than the new models of vehicles today demand. Backspace was advertised as a function of offset.

As aluminum wheels evolved, many manufacturers got involed, many overseas as well. There was a large difference in manufacturing designs, where some backside lips were made for standard wheel weights & some flat faced where weights had to be placed in other areas of the wheel. With this change & the fact that some wheels are forged & therefore thinner, it became evident that this backside measurement now had a different meaning. Wheels also were made for trucks that were much thicker, throwing off this dimension even more.

Quite a few years ago, most of the manufactures standardized on published offsets, giving dimensions of how far the bead surface was offset from the wheel center mounting surface (these are generally metric measurements now as well). To find out where the actual backside dimension of the wheel was, you had to know how thick the rim was. I've seen this vary from just over 1/4" to nearly 3/4". Comparing 2 different brands of wheels, you never knew what you were getting.

Now that most wheel companies show both the offest & backspace, you can get a better idea where the clearance issues might be. Now one can get an apples to apples comparison using both offset (to calculate tire placement) & backspace (to see if the wheel should clear the tie rod, strut or control arm). This is not because people cannot add, but because it does provide a benefit for fitment. Obviously when you cut it really close, only an actual test fit will work.

I hope you can see that this new method is a benefit & the best way to communicate data that anyone can relate to the current catalog offerings, is to describe it the way that I originally did.

There was no original intent to start an argument, only to offer my actual experiences. As an engineer, I take pride in providing accurate info & did not enjoy being called out on what I thought was originally a helpful post. Obviously I felt the need to reinforce my information by providing corresponding data. Differing opinion is not necessarily a bad thing, unless one fails to recognize the other point of view. I think this is the first step here, do you agree?

SDIF

Stephen, I hear you.

The techinical method is not the same as a practical method.

I was using the math provided by the wheel mfg and it did not add up. To what I was seeing on the car.

I called and spoke with some dummies and finally figured we were measuring the wheels differently.

For practical fittment, their method is useless.

I measure the simple way because that it the measurement that I need for clearance. That is what is important.

It the wheel mfg wanted to be really helpful the would mention the clearance distance from the wheel mounting point to the wheel spokes. This si where brake fittment get fun.

Stephen

iTrader: (12)

Yes & yes.....I have been trying to get my point across, that I was measuring OLD SCHOOL, not by todays modern/simple method.

Yes...Mount to edge is simpler, but not the way I grew up with. And I'm only 37, not an "old fart".

The offset crap is what bothers me the most.

Just really bothered me,when ROH themselves, told me they were 0mm offset/4.5" bs, yet people say ROH is wrong???

But this whole thread became null a couple of weeks ago...I'm staying with my 275/285 17" (going 315 on the back) & selling the 16" crosslaces. Anybody want them?

The only relevance this thread has now, for me, is that I need to describe to Weldcraft, what I want the 2 wheels widened to. 1" edge to edge, or add 2", bead seat to bead seat, to acheive a 11" tire seat.

Guest

If that is so, post proof from a book. Otherwise your opinion is worthless.

Stephen

iTrader: (12)

It is not my OPINION, and I was just backed up, by the "old world" standard of measuring method.

I don't have any books to quote, although I did provide a link earlier supporting me. Nor am I going to waste any more of my time with this thread....

Guest

Old like when? What do you want, 1950? And your link does NOT SUPPORT YOU.

BMR Sales

I just cant see taking an offset (backspace) measurement from inside the lip of the wheel. That would be a false reading because if you only have X-mm to clear coilovers and you dont measure from the innermost point of the wheel then things are going to hit. Maybe thats how they did it a long time ago but it makes no sense nowadays.

As this picture shows measurments for offset are outer most and inner most measurements.

Stephen

iTrader: (12)

All this has nothing to do with Width vs Weight anyways.....

I'm done with ya'll.

BMR Sales

Why are you taking this so seriously? There is no reason to get all bent because someone does something different than you. Geez man just keep measuring them your way. No big deal.

Lonnie P

Stephen,
I hope you are not an old fart, because you are 5yrs younger than me.
I know the old school way very well & have come up against the same situation trying to get the proper fitment.

The 15x8 rally wheels on my old Camaro have a 3.5" backspace, from years back, & suddenly I can buy 4" backspace ones, which got my attention, only to realize they are the same wheel .

Things change, sometimes you just have to go with it...