Will 7-speed MicroSHIFT work with 9-speed shimano cassette?

Question

I am building out a marketplace bike. It came with a MicroSHIFT derailleur and had a 7-speed cassette on it. I want to put a 9-speed shimano cassette on and still use the MicroSHIFT derailleur. Are they compatible?

Answer 1

The Microshift RD it has is likely Shimano-compatible in terms of its actuation ratio, i.e. it likely uses the actuation ration sometimes known as "2:1" or "1.7," among other names. They've made many different models and you don't say which, so the first step there is getting the model number off it if present or visually matching it up with images if not. If Microshift describes it as something along the lines of "Shimano-compatible 7/8-speed," that means it uses the actuation ratio that all Shimano RDs use beginning with the first indexing groups after first-generation indexing DA and ending with mountain 10, so yes it would be an actuation match with a 9-speed shifter and a cassette.

The subjective or hard to predict part is that even if the actuation ratio is a match, which it probably is, pairing a low-end RD with a higher speed count than it's made for can run into issues with lack of precision in the pivots, as well as possibly other construction factors, causing poor performance. This is especially true if it's heavily used and has any acquired pivot slop. This consideration doesn't necessarily arise from being nominally 7-speed, but from being low-end.

While it's been uncommon in the entire timeframe that Microshift parts have been around, it is still possible that the freehub body is 7-speed-only. Some bikes do still come with them. If so there is no way of putting a 9-speed cassette on the wheel (although you're changing parts so maybe that includes the wheel).