First my thanks to Rob for providing tech info. Cheap place for transponder?.Does anyone use 509's under any circomtances I have a set of new 175's that came with the car

I got my transponder from Sports Timing Services 08700110686 they were the cheapest at the time at £147.
A couple of people at the back of the field use 509s. 175s are generally used in the wet where the differences between 509s and 539s are probably less. Try and get another set of wheels and put new 539s at 185 on them and then keep the 509s 175 as wets!
Dickie

I got my transponder from the same place and they're around £200 now! I tried to get a second hand one for ages, but couldn't find one anywhere. Had to bite the bullet in the end!

I'm not sure on the prices now but if anyone is buying one make sure that you tell them its for 750mc racing, as I think this entitles you to a bit of a discount. (or I'm sure it did when I got mine)

Gavin