When my chain is on the biggest gear in front and biggest gear or second biggest gear in back, my chain slipped out of the front gear each time I pedal back. Could someone please advise why does this happen?and How can I fix this Thanks
First off all you shouldn't be shifting to the extremes. If your in the largest ring in the front I usually go 4 or higher in the back with a 7 speed cog. Thats probably normal, when I'm in 2 in the front and 1 in the back my chain will jump down a cog on the back when I pedal backwards. Likewise if your in the smallest ring up front and the smallest out back you might have problems. Hope that helps
'''96 Litespeed Catalyst, '05 Litespeed Firenze, '06 Litespeed Tuscany, '12 Surly Pacer, All are 3x8,9 or 10. It is hilly around here!
It means your chainline is off and a shorter bottom bracket spindle will improve the situation if one can be fitted. However, as dr. raleigh is right and you should avoid the big-big combinations.
Also, backpedaling isn't a problem as there is no reason to do so when riding unless the chain spilling is so severe it occurs when you back pedal the fraction of a turn need to bring the pedals into position for a standing start.