For high end bycycles go to Carbon Wheels close to Jarir at the Raddison Signals. They are very helpful and knowlegeable. For people like myself with more down to earth bikes there is a very good repair shop which also sells more budget bikes at the TV roundabout. It is called Al Markhiya Stores phone 44860355 mobile 55433970. Thet put a new crank and bearing assembly into my Hummer bike for a very reasonable price and gave the bike a complete service as well. They also managed to mend the gear selector when it was damaged, whilst I waited.