Have been looking for a set of rims for my carbon trek bike
have been looking at fulcrum 5 , mavic askium and shimano RS20 can any body help have read differing reviews on all these manufacturers What rims should i go for PLEASE HELP!!!!! budget would be around 200 pounds
It might sound overly negatve but I wouldn't buy any of these wheels. Having been there and done that with cheap factory wheels, I now steer well clear.
In nearly all cases a wheel built with simple but reliable hubs (eg Shimano 105), a reliable rim (Mavic Open Pro or similar), and double butted spokes and brass nipples will likely be more reliable, easier to service, and probably lighter than the wheels you've mentioned. They may well be cheaper in the first instance, but they will definitely be cheaper in the long run, thanks to reliability and the easy to find and cheaper parts.