How to measure OFFSET and FLUSHNESS

EL PAALO · 09-06-2005, 08:32 PM

measuring FLUSHNESS -

First get a big level (one that's actually level is best).
Second, get an accurate tape measurer (mm is good), preferably one that hasn't been used for real work since they get bent an inaccurate for precision measuring quickly.
If you have calipers instead of a tape measurer, even better.
A second "bullet" level is good to make sure your measuring device (tape or caliper) is level as well.

I didn't use a bullet. only 2 hands and taking pics is a pita without help. :'(

Step 1:
Park on level ground.
Step 2:
get the level against the fender and level. be sure to check the top and bottom levels if you want accuracy.
Step 3:
measure the distance from the outermost edge of the wheel to the level.

Here's some pics if you still don't get it:

The measurement from the stock wheels on my truck is 38mm from flush on the front fenders. It's more in back, but I don't recall the number and it doesn't matter for this example. Why did I just type that then ....... because I'm rambling? My factory wheels are 8 +30 (diameter doesn't matter here). so, to get this width wheel flush, just subtract 38mm from the current offset which would result in 8" wide with a -8 offset. plug your wheel numbers into the offset calculator to get other widths flush. a 9" width would be flush for me up front with a +12 offset.
These numbers aren't relevant for the mr2, but the concept is exactly the same for any vehicle.

EL PAALO · 09-06-2005, 09:11 PM

measuring OFFSET -

LOOK AT THE FRIGGIN' WHEEL before you bother measuring

many wheels have all the pertinent info stamped on the back somewhere, generally between the mounting points or on the back of the spokes. oddly, some of the pricier makers like volk use stickers that often get taken off for whatever reason. if your sticker is gone or there's no info on the back, start measuring (take the wheel off first).

you need:
1. something to lay across the back of the wheel. flat, not bent, doesn't bend. something with definite edges is good. I used a large ruler sideways so I wouldn't have to worry about it flexing.
2. some change if the tires are still on the tires (to put between the flat thing and the wheel edge since many tires overhang the wheel and will screw up the measuring). I used a quarter and a penny which equal 3mm in width (measure your own change just in case - especially folks not from the U.S.

)
3. a measuring implement ....... I used a tape measurer, but you could use just about anything and just mark it and measure the marks with a ruler later if that seems easier to you.
4. paper and pen if you're like me and forget numbers all the time.

Alright, time to measure.
1. Measure the width of the wheel from outermost edge to outermost edge. The wheels I measured came out to 10" on the tape measurer. The actual width of the wheels is 1" thinner than measured due to the flanges being 13mm wide on either side. So, the number I write down is 9".

2. lay the flat thing across the outermost portion of the wheel. if there's tire in the way, use the change (quarter and penny in my case) to find the error (3mm in my case).

3. measure from the mounting face of the wheel (the part that actually touches the hub on the car) to the flat thing. the number I got here was 151mm.

now for simple math.
1. take the width and divide by 2. 9 divided by 2 = 4.5" for me.
2. convert half the width to mm. 4.5" = 114.3mm
3. subtract that from the total measurement (151mm in my case). 151 - 114.3 = 36.7
4. subtract the error (if any) from 36.7 - 3 (the quarter and penny) = 33.7mm
5. subtract 13mm for the backside flange that was included when you measured. 33.7 - 13 = 20.7mm

offset = 20.7 according to my measurements. actual offset (stamped on the back of the wheel) is 20 so good enough considering my crude implements. Use quality tools and measure multiple times to ensure accuracy. I was only .7mm off with a camera in one hand so if you have somebody there to help you and are careful it should be no problem.

13mm is the width of J or JJ flanges. There are some exceptions like JK maybe ..... haven't seen a width measurement for that flange and HRE uses a different size (unknown to me) also. CCW and some other custom wheel makers may also use something slightly different. Almost any wheel you run across will be J or JJ though.

lovely09 · 11-18-2009, 08:36 PM

Wheel Offset is simply the distance between the wheel's hub-mounting surface and its center plane.Positive offset means the hub-mounting surface is closer to the wheel's outboard side.Conversely,negative offset means it's closer to the inboard side. f the mounting surface coincides with the wheel's center plane then offset measures in at zero.In other words,offset determines the lateral or side to side position of the wheel.

09-06-2005, 08:32 PM	#1 (permalink)
EL PAALO Wheels make the car. Join Date: Feb 2005 Location: San Marcos, TX Posts: 2,549 Thanks: 4 Thanked 75 Times in 71 Posts My Google Map iTrader Rating: (3/100% )	How to measure OFFSET and FLUSHNESS measuring FLUSHNESS - First get a big level (one that's actually level is best). Second, get an accurate tape measurer (mm is good), preferably one that hasn't been used for real work since they get bent an inaccurate for precision measuring quickly. If you have calipers instead of a tape measurer, even better. A second "bullet" level is good to make sure your measuring device (tape or caliper) is level as well. I didn't use a bullet. only 2 hands and taking pics is a pita without help. :'( Step 1: Park on level ground. Step 2: get the level against the fender and level. be sure to check the top and bottom levels if you want accuracy. Step 3: measure the distance from the outermost edge of the wheel to the level. Here's some pics if you still don't get it: The measurement from the stock wheels on my truck is 38mm from flush on the front fenders. It's more in back, but I don't recall the number and it doesn't matter for this example. Why did I just type that then ....... because I'm rambling? My factory wheels are 8 +30 (diameter doesn't matter here). so, to get this width wheel flush, just subtract 38mm from the current offset which would result in 8" wide with a -8 offset. plug your wheel numbers into the offset calculator to get other widths flush. a 9" width would be flush for me up front with a +12 offset. These numbers aren't relevant for the mr2, but the concept is exactly the same for any vehicle. __________________ WHEELSPECS.COM - a ridiculous number of wheel pics & links

Thread Tools
Show Printable Version Email this Page
Display Modes
Linear Mode Switch to Hybrid Mode Switch to Threaded Mode

LinkBacks (?) LinkBack to this Thread: http://www.mr2.com/forums/wheels-tires-suspension-brakes/Toyota-MR2-1478-how-measure-offset-flushness.html
Posted By	For	Type	Date
Offset Formula - VW GTI Forum / VW Rabbit Forum / VW R32 Forum / VW Golf Forum - Golfmkv.com	This thread	Refback	11-17-2007 07:38 AM
Offset Formula - VW GTI Forum / VW Rabbit Forum / VW R32 Forum / VW Golf Forum - Golfmkv.com	This thread	Refback	11-15-2007 10:02 AM

09-06-2005, 09:11 PM	#2 (permalink)
EL PAALO Wheels make the car. Join Date: Feb 2005 Location: San Marcos, TX Posts: 2,549 Thanks: 4 Thanked 75 Times in 71 Posts My Google Map iTrader Rating: (3/100% )	measuring OFFSET - LOOK AT THE FRIGGIN' WHEEL before you bother measuring many wheels have all the pertinent info stamped on the back somewhere, generally between the mounting points or on the back of the spokes. oddly, some of the pricier makers like volk use stickers that often get taken off for whatever reason. if your sticker is gone or there's no info on the back, start measuring (take the wheel off first). you need: 1. something to lay across the back of the wheel. flat, not bent, doesn't bend. something with definite edges is good. I used a large ruler sideways so I wouldn't have to worry about it flexing. 2. some change if the tires are still on the tires (to put between the flat thing and the wheel edge since many tires overhang the wheel and will screw up the measuring). I used a quarter and a penny which equal 3mm in width (measure your own change just in case - especially folks not from the U.S. ) 3. a measuring implement ....... I used a tape measurer, but you could use just about anything and just mark it and measure the marks with a ruler later if that seems easier to you. 4. paper and pen if you're like me and forget numbers all the time. Alright, time to measure. 1. Measure the width of the wheel from outermost edge to outermost edge. The wheels I measured came out to 10" on the tape measurer. The actual width of the wheels is 1" thinner than measured due to the flanges being 13mm wide on either side. So, the number I write down is 9". 2. lay the flat thing across the outermost portion of the wheel. if there's tire in the way, use the change (quarter and penny in my case) to find the error (3mm in my case). 3. measure from the mounting face of the wheel (the part that actually touches the hub on the car) to the flat thing. the number I got here was 151mm. now for simple math. 1. take the width and divide by 2. 9 divided by 2 = 4.5" for me. 2. convert half the width to mm. 4.5" = 114.3mm 3. subtract that from the total measurement (151mm in my case). 151 - 114.3 = 36.7 4. subtract the error (if any) from 36.7 - 3 (the quarter and penny) = 33.7mm 5. subtract 13mm for the backside flange that was included when you measured. 33.7 - 13 = 20.7mm offset = 20.7 according to my measurements. actual offset (stamped on the back of the wheel) is 20 so good enough considering my crude implements. Use quality tools and measure multiple times to ensure accuracy. I was only .7mm off with a camera in one hand so if you have somebody there to help you and are careful it should be no problem. 13mm is the width of J or JJ flanges. There are some exceptions like JK maybe ..... haven't seen a width measurement for that flange and HRE uses a different size (unknown to me) also. CCW and some other custom wheel makers may also use something slightly different. Almost any wheel you run across will be J or JJ though.

11-18-2009, 08:36 PM	#3 (permalink)
lovely09 No Skills Join Date: Nov 2009 Posts: 10 Thanks: 0 Thanked 0 Times in 0 Posts iTrader Rating: (0/0% )	Wheel Offset is simply the distance between the wheel's hub-mounting surface and its center plane.Positive offset means the hub-mounting surface is closer to the wheel's outboard side.Conversely,negative offset means it's closer to the inboard side. f the mounting surface coincides with the wheel's center plane then offset measures in at zero.In other words,offset determines the lateral or side to side position of the wheel.