View Single Post
Old 07-29-2003, 12:39 PM   #69
subysouth
Scooby Guru
 
Member#: 5039
Join Date: Mar 2001
Chapter/Region: South East
Location: Ocean Springs, MS
Vehicle:
2007 Outback XT
Grey 5-speed (sold)

Default

Quote:
Originally posted by BriDrive
SubySouth...I'm quoting myself down there...Do you disagree that a wider wheel displaces the same weight over more area. If not, then the only point I was trying to make was that I have proved that the ONLY offset where the weight would still be equally displaced with different wheel widths is at zero offset (hub is centered directly over center of wheel) Tell me where my example went wrong down there...BriDrive

"I beg to differ: your point on offset/load displacement only holds true IF AND ONLY IF your offset is always ZERO. 53mm offset on a 6.5” wheel will certainly and definitely have a different load displacement than a 7” wheel with 53mm offset. To validate this, I’ll use a random load number for the right front wheel. Lets say that 960 lbs needs to be displaced over a 6.5” wide wheel (165.1 mm). That equates to 5.815 lbs/mm. On the 6.5” wheel with 53mm offset, there are 135.55 mm to the inside to displace weight and 29.55 mm to the outside to displace weight. That’s 788.22 lbs to the inside and 171.78 lbs to the outside. (This incidentally is the 82.1% ratio I talked about because I used the stock wheel) The important point here is that there are 5.815 lbs/mm displaced. On a 7” wide wheel (177.8mm) the wheel only needs to support 5.399 lbs/mm. If you maintain a 53mm offset on this wheel, there are 141.9 mm to the inside and 35.9 mm to the outside. That’s 766.1 lbs to the inside and 193.9 lbs to the outside. That’s equivalent to a 79.8% ratio."
Bri at zero offset is the only place at which the ratio you are using for offset determination will be maintained. My position is the ratio approach negates the principle upon which offset is based. Offset is based on the fixed distance from the mounting face to the sweet spot over the bearings. Thats what I was saying earlier, offset introduces a discontinuity into your ratio theory, but the ratio theory doesnt follow(or have anything to do with) the reason for offset. As you go to a wider and wider wheel the fixed 53-55mm correct offset is mathematically diminished using your ratio theory. The correct offset is a fixed physical dimension built into the design of the hub/knuckle bearing assembly and doesnt change. It by nature divides all additional width equally based on the bearing load sweet spot.

ss
* Registered users of the site do not see these ads.
subysouth is offline   Reply With Quote