looking to replace 21 speed Shimano on a Rockhopper

[sg5y]

I have a Rockhopper mountain style bicycle ,not an E bike. 20 years old.Generic but good. The 21 speed was always overdone and un needed. But I like the bike and want to keep it. I prefer to travel with that bike rather than the heavy cumbersome XP4.
The 21 speed has 3 discs. I was wondering if Shimano or others have a modern 10-12 speed now that will swap in and provide as good or better smooth service.A 2 disc unit. Anyone know of anything that might fit the bill..?

 

[EMGX]

I might not be entirely clear on what you're asking, are you wanting to replace a 7 speed cassette with 10 speed and pair it with a 2x crankset? 2x crankset swap is simple, either square tape or hollow with external bearings and set your 3x front derailleur low stop to prevent chain drop. A 7 speed freehub won't work with 10 speed cassette (unless you remove one of the cogs and go with 9 speed). If you have a spin on freewheel then a 10 speed isn't compatible although there are some 8 speed spin on freewheels. Although any of these changes might be more bother and expense than it's worth just to drop the 3x chainring.

 

[sg5y]

too complicated

 

[Marcela]

Right now I am attempting kind of the reverse.

I have a Sequoia that has the two front chainrings on an 11 spd rear 11-36 gears. The chainrings are 48/32. I find the 32 works fine. the 48 is too much of a jump, I checked the other day and level ground moving along pretty good I don't use the 11,12,13 gears, and downhill I'll be coasting above that speed, pretty fast. So in my attempt to reduce the 48, I have a 3x fsa 30/39/52 I am getting ready to mount as soon as the bb tool gets here. Plan on using the 30/39 gear and ignoring the 52, if everything goes according to plan, and think the 30/39 will work fantabulous, the 39 letting me use the smaller gears to effect. This puts the chain line on the inner 30 on the left side of the cassette, on the 39 moves it to the right, with good amount of overlap.

From what I was looking at, all the 2x chainring sets have that similar big jump. So you might just consider using the two inner chainrings on your 3x and see if that works. Maybe go to a bigger spread on the cassette, mine is 11-36, bet the mtb is more compact.

Utah trikes is where I found the front crank assy, pretty good deals on take offs, might have what you are looking for.

 

[JustSomeGuy]

There are quite a few 1x10, 1x11 and 1x12 setups from Shimano and SRAM that might work for this kind of conversion. I’d take a look at Shimano Deore or CUES, depending on what your bike can accept. Just make sure the cassette/freehub, derailleur, shifter and chain are compatible with your existing wheels before ordering anything.