I have a 1988 GT Outpost All Terra mtb. I am converting it for use as a hybrid bike for groomed trails and lite road use. Have switched out original tires for Michelin Country Rock 16 x 1.75 tires. Love em! Component set is Exage Country all around. Bike is all original and in pristine condition. My plan is to add trekking bars and use the entry level Exage components until they need to be replaced. They work so well at this point that they may never have to be changed. The triple crank is Biopace (48-38-28) Shimano shifters are indexed. Mynfrench road bike has a double crank (52-42) I believe. I avg 13 mph on the majority of my rides. I've lost a little avg speed when riding the GT. I don't know why other than possibly tire change, french bike is 27" GT is 26".......I'm trying to decide whether to change the Bio pace triple to a Biopace 52-42 double. There are things I don't know here: 1. Can I switch from a triple to a double with no adverse issues? OR 2. Can I just switch the 48 38 chainrings out and add the 52 42 rings with no adversity? OR 3. Are there issues regarding the chain I must be aware of? I really like the Biopace and want to keep it in some iteration. I've even thought of changing to a better quality Shimano Exage double crank 52/42, but don't know the ramifications of that change with respect to font/rear derailleurs. At this point changes aren't that expensive because I'm dealing with an entry level bike to begin with, so, I'd like to make pe manner changes now while it is still cost effective.

Any and all suggestions/help are greatly appreciated!

Thanks folks!