This information is given with the hope that it will not prevent you from building a model.  The modeler is encouraged to look at the parts and use the ones that suit.  The human eye detects errors in proportion rather than dimension.  Differences in dimension less than .01 aren't noticed by MOST people.  For those of us cursed (or blessed) with calibrated eyeballs...  well...



 
Actual
1/35 Scale
Italaeri (M4A1)
DML/Dragon (M4A4)
DML/Dragon (M4A1)
AFV Club (kit)
Tamiya (M4A3)
Tamiya (M4)
Academy (M12)
A^ 
19 
0.543
0.557
0.563 
0.559
0.509
0.563
0.563
0.556
B^
17.5
  0.500
0.514
0.500
0.505
0.503
0.495
0.495
0.518
C* 
11.75
  0.336
0.353
0.353
0.346
0.361
0.352
0.352
0.365
D*
8.375
  0.239
0.240
0.241
0.236
0.262
0.254
0.254
0.250
E*
20
  0.571
0.573
0.570
0.572
0.601
0.572
.572/.561
0.562

^Actual dimensions from Kurt Laughlin's measurements
*Actual dimensions from drawing in Hunnicutt, Pg 135, US Ordnance drawings and actual measurements


You can see none of the VVSS units are exactly to scale.  The most glaring error is the oversized bogey wheel dimension of the AFV Club kit.  That is unfortunate in that the wheel stamping is probably the best looking one.  Of course, if you have access to a lathe the point is moot. 

Below: Tamiya M4A3/M4 Early bogeys with some upgrades.The wheel centers are modified castings of the AFV Club wheels inserted into the original Tamiya wheels.This makes the wheels double sided.
The skid is formed from brass shim stock.  The bolt heads are sliced from plastic hexstock.
 


The modified Tamiya bogey unit
The unmodified Tamiya bogey unit

Some detailing was added to the rear 

An actual unit as found on an M4A3
 

Unpainted assembly
The return roller bracket bolt holes were drilled with a .019 inch drill

The tank in these photos had dished wheels.
None were concave/convex.  I have not come across any concave or convex wheels what were configured concave/convex.

The wheel conversion process
The necessary cuts made on the existing wheel back.
The back becomes the wheel front, once the new hub is installed.

The master center. 
Seven were made and two molds produce a whole set in one pour
The modified wheel

Mike Canaday
mmcalc@crosslink.net
modified 12-12-02