hanomon Posted July 7, 2004 Share Posted July 7, 2004 With a 7" wheel front and a 4"backspace, what would this translate into in terms of metric off-set in mm? Same question for a 9" wheel with a 5 1/2" backspace. Quote Link to comment Share on other sites More sharing options...
DaleMX Posted July 8, 2004 Share Posted July 8, 2004 Well, if a 7†wheel had a 3.5 backspace then it would have 0mm offset. A 4†backspace equals .5†positive offset or 12.7mm. Looks like the 9†would have 1†of positive offset or 25.4mm. Just remember that offset is from the center of the wheel and backspace is from the back of the wheel. Dale Quote Link to comment Share on other sites More sharing options...
Savage42 Posted July 8, 2004 Share Posted July 8, 2004 Not that I'm a wheel guru or anything, but I think you're just slightly off, but have the right idea. A "7 inch" wide wheel is actually 8" wide on the outside, only 7" from bead to bead. A 4" backspace on what is called a 7" wide wheel is actually "0" offset, as it's right in the middle of the 8" width. Call your local wheel & tire guys to confirm, but I believe thats how it works. Quote Link to comment Share on other sites More sharing options...
DaleMX Posted July 8, 2004 Share Posted July 8, 2004 A little research shows that Savage is correct. Thanks for setting me straight! Dale Quote Link to comment Share on other sites More sharing options...
Drftn280zxt Posted July 8, 2004 Share Posted July 8, 2004 how can you determine what size (width) tires you need for a wheel? Quote Link to comment Share on other sites More sharing options...
Savage42 Posted July 8, 2004 Share Posted July 8, 2004 The tire rack website will usually tell you the recommended tire size for a specific wheel. Quote Link to comment Share on other sites More sharing options...
Tim240z Posted July 8, 2004 Share Posted July 8, 2004 1" = 25.4mm Quote Link to comment Share on other sites More sharing options...
DaleMX Posted July 8, 2004 Share Posted July 8, 2004 Corrected data: So the way this looks a 7" wheel that is 8" wide and has a 4" backspace has 0 offset. A 9" wheel that is 10" wide and has a 5.5" backspace has .5" positive offset or 12.7mm. Sorry all, Dale Quote Link to comment Share on other sites More sharing options...
hanomon Posted July 14, 2004 Author Share Posted July 14, 2004 Here is what I came up with; from the hub mounting surface under load (or in the normal ride position) measuring stright-up and then out to the inner fenderwell, then into what would be the lower spring pearch (or the area where the tire/wheel would make contact) 3.5"-outer 7.5" inner. Combine these two values, minus approx 1" or 25.4mm which leaves approx 1/2" in and 1/2" out clearance. then minus another 1" for the tire from the wheel bulge. Again approx 1/2" for both in and out. So what we now have is a 9"wheel, down from an 11"clearance with an approx 10" tire. With a wheel center of 4.5" Outer clearance is 2.5" and inner in 6.5" this gives it a 2" positive offset. Please correct me if I'm missing something. Thanks for the feedback. Quote Link to comment Share on other sites More sharing options...
Drftn280zxt Posted July 16, 2004 Share Posted July 16, 2004 I think I know what your saying hanomon. But i'll do a drawing and we'll see if were on the right page and if everything works out right as you think. Quote Link to comment Share on other sites More sharing options...
Clifton Posted July 17, 2004 Share Posted July 17, 2004 This might help. http://toy4two.home.mindspring.com/offset.html Quote Link to comment Share on other sites More sharing options...
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