
I emailed Sanwa, R-Design and Traxxas as these are currently the only companies making wheel foams. The Futaba specs came from an NIP foam grip.
Sanwa was the only company to provide information, Traxxas refused to offer assistance, and R-Design never replied.
I also messaged Amain and asked about the I.D. the O.D. and the width of the steering wheel foams they offer and received the following information:
R-Design 4901...................OD:50 - ID:40 - W:30mm
R-Design 4900.......................OD:50 - ID:40 - W:26mm
Sanwa 107A90131A.................OD:44 - ID:32 - W:19mm
Sanwa 107A90134A.................OD:44 - ID:35 - W:23mm
Traxxas 2224........................OD:50 - ID:35 - W:25mm
Measured a Futaba 4PK replacement foam grip and got:
FTA-30............................OD:47 - ID:39 - W:17
The information I received from Sanwa regarding their wheel foams is a little different than the info provided by Amain, but is as follows:
107A90131A: Models prior to M11X (Machine-1, Machine-A, M11, BLAZER, MX-3,MX-3S, MX-A, etc. (wheel width 17mm)
107A90134A: M11X, M12, M12S, M17, MT-4, MT-4S, MT-44, MT-S, MT-5, MT-R (20mm wheel width)
The outside diameter of the steering wheel is 41mm unless the model is very old.
Should give folks a ballpark on replacing their old, dry, icky foam grips.
Though... other options are available...

Image used with ZERO permission from the copyright holder

...but he's cool so I'm sure it's ok
