42t 7 speed cassette
 

On Grant's Rivendell blog a couple weeks ago there was a teaser for a 13-42t 7 speed cassette, with normal 7 speed spacing. It could be an interesting setup on an old touring bike. But what kind of an rear derailleur would one use to reach the 42t cog? I know there are 10 speed mountain units that could handle the job. But with all the differing pull ratios on these then what 7 speed shifter would work? I suppose a friction shifter on the downtube could cover the cassette range with one of these modern RD's. One solution that comes to mind could be to use a 9 speed mountain RD that's rated to 36t and then add a Wolf Tooth or similar link. With a 9 speed Shimano RD most any 7 speed shifter should work. Any other ideas?

I'm pretty sure there are 9 speed RDER's that will fit the bill.
I'm curious what the other 5 cogs are??

I would imagine that there are HUGE jumps between each gear. Do you want such big jumps between your gears?

Cheers

Actually, it's kinda genius... If my quick-n'-dirty math is correct, and if they pick the right 2-6 cogs, it should half-step with a 52/42 or 48/39 double crank and give a 1:1 or better low gear. Still pretty big steps, but not as ridiculous as it looks at first sight.

--Shannon

7 speed? that doesn't make sense even if if just from a marketing perspective. it'd be so niche, how on earth could sales even justify production? reminds me of the idea of his making a wheelsize between 650b and 700c.

Wide range and gaps can work on a mtb. I have 13-40 8 speed, but toyed with 15-40 7 speed. I couldn’t live with no top end so swapped out the freehub for an 8-10 speed and went 13-40.

But a 13-16-20-24-30-36-42 is not bad on a mtb or a touring type bike.

Shimano used to have a 7 speed “K” cassette that went …20-24-29-34.

I’ve run a …20-23-26-32 in a 7.

Much of it depends on foregoing some performance for range.

John

I think the idea here is for a simpler and maybe trouble proof drivetrain. And as some people don't get much use of the 11 and 12t cogs there might not be a big utility loss from a 9 or 10 speed cassette. It all depends on the cog setup and riding environment. Thinking further, instead of putting a 4mm spacer on the inside of the cassette how about just mounting a 7-speed freehub body and redishing the wheel? And further with off-centered rim drilling it would be a nearly dishless wheel on 135mm spacing.

Grant addressed this in the blog.:foo:https://www.rivbike.com/blogs/grant-...-blog/mid-septhttps://cimg0.ibsrv.net/gimg/bikefor...f9d108ca6a.png

Shimano's 9-speed Shadow derailleurs are close to being able to handle a 42t sprocket (despite their official ratings of 36t if I recall correctly). I have an RD-M3000 that was used with an 11-40 9-speed cassette without issue, and it could have pretty easily done a 42t. I think the shifting on the smaller sprockets would be slow and/or messy, however. Those 9-speed Shadows (talking M2000, M3000, M4000, M592, etc.) feature a lower cage pivot coincident with the upper pulley axis -- so the upper pulley does NOT rotate upward as the cage rotates rearward. This means the upper pulley is pretty far away from the smaller sprockets when adjusted correctly for the largest sprocket, and index shifting becomes less graceful. I ended up switching my bike (with the M3000) back over to a 3x setup in the front and a cassette with less range so that I could set the upper pulley tighter to most of the cassette for better shifting. I think one of these derailleurs would work better when friction shifted vs. index shifted (on a cassette with such range).