I had a few more minutes to look through the AFT rulebook and another change caught my eye in the SuperTwins section:
4.6 c. Frames must be constructed of steel or aluminum.
As far as I'm aware, this is the first time in AFT history, at least it recent history, that Twins have been allowed to race with aluminium frames.
This is intriguing for a number of reasons.
Why change it now after, what, 100 years of steel only?
Who has requested the change, because it doesn't seem like something that would just be changed on the off-chance, not after all this time?
At first I thought KTM, but as a company they're committed to steel frames. They do have an 890cc twin that will hopefully show up at some races towards the end of the season, though. That cc limit is just inside the recent 900cc rule.
Royal Enfield? They're a company that exclusively makes steel chassis, but they bought Harris Performance who are experts at both steel and alloy (having made 500cc GP frames back in the 1990s). Seems unlikely they'd request the change?
Howerton alloy framed Harley?
The minimum weight remains unchanged, so there isn't a weight advantage to be had (in 2020 at least), so I can't think of many advantages over a chro-mo frame beyond weight except to tie the design to an existing road bike for marketing purposes.
The change is only for the SuperTwins class. Production Twins, which are also all in custom-made flat track frames, must still use steel frames.
Pboto: Scott Hunter/ AFT