My bike originally came with an LX RDM-570 from 2001. It looked like it was an SGS so I purchased an XT RDM-751 SGS to replace it. The weird thing is that they are different sizes. Measuring directly betweeen the centre point of the jockey wheels, the LX is 85mm whilst the XT is 100mm. Does this mean that the LX is actually a GS? There doesn't seem to be any markings on it to indentify it as GS or SGS. Has the design changed over the past few years and SGS is now a little bit longer? Are there any resources on the web such as an "exploded view" with dimensions for shimano products? Thanks.