[autoavia]

BAR Racer wrote
Thinking about it, there have been at least three different formulations of Ortmann tyres over the years so it is possible that one of them could have caused some problems. The original version was the best but the EU banned certain components of it. The second version was not very good and produced blue dust when trued. I am unsure about the latest version. Any idea how old the ones you are using are?

 You are right in saying that the original formula was the best but old Ortmanns are hard to find now.
We are all using the latest mix which produces a grey dust when trued. The same grey dust is picked up by modern rubber tyres on the Tuesday club night following a vintage meeting but it cleans off with tape and eventually we get a grippy track again.