I bought some TRC-01 wheels, as used on the new A4WD1 rover, to replace the overly squishy wheels on Regis. Regis was built on a 4WD-3 base. However, the TRC-01 hubs are different, and don’t seem to fit the axle properly.
The 4WD-3 axle has two tiny tabs that fit into slots in the wheel hub. The new TRC-01 hub doesn’t have these slots. I can still attach the wheels using the bolt in the center, but it just doesn’t seem secure.
Unfortunately I can’t use the old hubs with the new tires because the diameter isn’t quite the same. Do I have to buy new axles to fit the new hubs? If so, how do I order them?
Ah, I see now that there are new hubs for sale, and a HUB-12 is what I need. I didn’t realize that this is different than the hub used on the 4WD-3.
You may have missed the link in the product information.
Description -
Traxxas Stampede Tera (Firm)
Diameter = 4.75"
Width = 2.375"
Hubs = 6mm (HUB-12) <----- This line 
Motor = Any 6mm output shaft
They are much less squishy eh? 
You will really like the strength this new hub / rim provides.
If these are RC style wheels, you can go to your local Hobby shop and get adapters I believe. From what I remember from my RC days they are only about $5. They should have adapeters that go both ways From slot to hex, and Hex to slot.
Yes, there is a noticeable improvement in ■■■■■■■■■■■■■■■■ It didn’t seem so at first, because you can still press on the treads and they give, but the sidewalls are much stronger, and that makes a big difference. I will order some HUB-12s.
Lokoing forward to your 12th year anniversary celebration. Will the bots be serving cake?
You will really like the strength this new hub / rim provides.