F1 Racing (35,000 for the UK edition. 65,000 worldwide)
Fast Car (60,000)
RaceCar Engineering (22,000 worldwide)
Autosport (18,000)
Motorsport News (8,000)
Also the 'Technology series, for which I can't find any circulation figures (Rally Race Technology, Alternative Race Technology and Historic Racing Technology) and Fast Ford magazine.
If you want to include motorcycling . . .
Ride
Motorcycle Sport & Leisure
Bike
100% Biker
MCN
Fast Bikes
Performance Bikes
Practical Sportsbikes
(I'm unsure as to which of those concentrate on motorsport, rather than on bike design and technology. Google the name, together with 'circulation' to find their sales figures)