Re: [Chevelle-list] Tires

[Clint Hooper]

Title: Message

I saved this from a post that Dale used to explain this in more detail. To quote American Racing's terminology: Backside setting/Back spacing - The measurement from the mounting pad to the inner edge of the wheel. Offset - The offset of the wheel is the distance from the mounting pad to the centerline of the wheel. Negative offset - When the mounting surface is closer to the disk/drum (Inside) of the wheel. Or the mounting pad is behind the centerline of the wheel. This type of wheel is commonly referred to as a deep-dish wheel. This offset is common in older vehicles and many of today's trucks and will bring the wheel/tire combination out away from the vehicle. Positive offset - The mounting pad is forward of the centerline of the wheel, towards the street side of the wheel. This is common in most front wheel drive cars and some newer trucks. Generally speaking a positive offset wheel brings the wheels closer to the center of the vehicle. Hope this will explain things a little more simply. FWIW,I rarely use offset numbers. Backspacing is much simpler to understand. Clint Hooper H&H Custom,owner 1969 El Camino ProTourer 2001 H-D FLHR custom bagger http://dalesplace.com/misc/friends/clint/clint_hooper.htm ----- Original Message ----- From: John Nasta The first sentence on that web page says "The offset (sometimes called the backspace)" sort of implying that they are the same. That's why I didn’t understand what one measurement had to do with the other.     -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]On Behalf Of Clint Hooper   Backspace and offset are two different animals,John. However,if you need air shocks to keep the rear tires from rubbing the outer fenders,it's a sure bet your wheels don't have enough backspacing. It's a critical measurement on all wheels,not just 15". The bigger the tire,the more important it becomes. Clint Hooper H&H Custom,owner 1969 El Camino ProTourer 2001 H-D FLHR custom bagger http://dalesplace.com/misc/friends/clint/clint_hooper.htm ----- Original Message ----- From: John Nasta   It seems like it's only people with 15" wheels who talk about backspacing. I guess I will be dealing with this soon myself.   There is good info and a diagram here:   http://www.high-impact.net/wheels/howtomeasurebackspacing.htm   I'm still not clear on how maximum offset has anything to do with the height of the caliper from the center of the axle, while minimum offset has to do with the depth behind the rim. I also don’t know why If (I) x2 (times 2) is greater than 12.125" (G), obviously your maximum offset must be just under 4" or why G is measured on the outside of the wheel while the caliper is on the inside, but I have time to figure this out.   My '70 Malibu has 15s on the back now and when the air shocks are not pumped up they rub. Offhand I don’t know the tire size, which could be the cause of the problem. I suppose I'm going to have to see how she sits with new shocks and then decide what to do about tires and wheels.