I think these are solid rubber tyres that have had great lumps carved out by wear (the spacing of gaps is uneven).
My source says that these things were often retyred with railway wheels and used on the railway.
Going back to the Bronniford (or Bronjeford), I have found scale plans of the 3-wheeled version on
www.theblueprints.com, and also in a WWII tank recognition book I have. Scaling up from that suggests that the 2-axle BA20 had 31.5" wheels- 5.25" to 1/6th scale- and that the 3 axle BA10 had 40" wheels- 6.7" at 1/6th. Good-looking machines in my view- I'll scan and post them up here if anyone's interested.
Phil
-----Original Message-----
From: OdysseySlipways-at-aol.com
To: tanks-at-rctankcombat.com
Sent: Thu, 2 Aug 2007 1.47pm
Subject: Re: Scale tires [TANKS [TANKS]