Two going round on their Bromptons? (8)

I haven't cracked this one yet — but the brilliant team at Fifteensquared have:

some sort of cryptic definition perhaps? Bromptons are folding bicycles, so perhaps to do with wheels (things that spin, cycle)? But surely Bromptons (more then one Brompton) have to have at the very least least four wheels. Perhaps it just means two cyclists who may be making a tour (going round)?