Originally Posted by
baj32161
Actually I was considering changing from a 48/36, 12-30 to a 48/34 11-34 if that would not take too much work
I thought the chain rings are already 48T and 34T!?
How much work is needed is determined by your existing crankset and rear derailleur ("RD"). You have two non-mutually exclusive options, i.e., it should be possible to do both:
1. Like
Canker said above, your best bet might to be install a 9-speed MTB RD (which has the same pull ratio as a 10-speed road STI shifter) and a 10-speed MTB cassette.
2. Post a picture of your Gossamer crank; does it have 4 bolts or 5? Older Gossamer 2x cranks have a 5-bolt 110 BCD. Current Gossamer Pro 2x cranks have a 4-bolt 120/90 BCD.
2. Just saw a picture of your bike here:
Bike Forums - View Single Post - Post your gravel bike. Looks like the crank has 5 bolts. If it has a 110 BCD spider, then a 34T is the smallest chain ring that would fit, and you may have to switch cranks to install a smaller chain ring, which may entail installing a new bottom bracket, depending on what the existing bottom bracket is.
Pros and Cons:
Option #1 (larger cassette) increases the gaps between adjacent gear ratios.
Option #2 (smaller chain rings) may lower your highest gear ratio.