Compact vs semi, what cassette

Sb4rly
Sb4rly Posts: 122
edited March 2018 in Workshop
Hi. Last year prior to a trip to the alps I fitted a compact chainset with an 11-28 cassette to my bike. I have now bought a semi compact for all year round riding and wanted to leave it on for the alps. Would a 11-30 on the back give me similar to the compact or would I have to go to a 32 and get a new rear mech etc to have the same ratios?

Thanks

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