Anyone tried adding a larger sprocket to a 7-speed cassette?

[Tom Harrop]

Hope everyone had a nice holiday.

I'm due for a new chain and I'm thinking of switching to a 7-speed cassette. I'm sorry about the long post, but I could use some of the group's wisdom.

I currently have the 12–36 9 speed HG61 cassette with the Sugino 46-36-24 that Riv sells, with Silver (friction) shifters. There's nothing really wrong with the gearing at the moment, except that I get the occasional ghost shift and the chain skips under load sometimes, and I can't actually use the 36t sprocket because my chain isn't long enough. Well, it's not long enough for the 46×36 combo, which obviously I wouldn't use, but I don't trust myself not to shift into it accidentally so I've got the limit screws on the rear derailer set so that I can't get into the 36t sprocket. The chainstays on the Bombadil are so long that I think I need 118 links for a 36t sprocket!

This brings me to my first question: Is there anything wrong with getting two chains and connecting the required length with Power Links, so I'd have two Power Links in the one chain?

In terms of the cassette I'd like to go 7- or 8-speed for chain life and hopefully to fix the ghost shifts. Since all the 8-speed cassettes I can get locally seem to start with an 11t sprocket, which I don't want, my hare-brained plan at the moment is to get the 7-speed 13–28 that Shimano makes, and since I'd need a 4.5 mm spacer to put that cassette on my 9-speed freehub, just use the 36t sprocket from my old 9-speed cassette with a 3 mm spacer instead. So I'd have a 13–28 plus a 36t 'bailout'.

I guess that's a large jump so the shift wouldn't be very pretty, but it's not a sprocket I'd use terribly often... or I could always use the 32t from my old cassette instead, or take a 34t sprocket from another 7-speed cassette. I just thought I'd check with the group to see if anyone's done this, before I go ahead and try?

Thanks,

Tom, in rainy Germany.

[Steve Palincsar]

On Thu, 2012-12-27 at 09:55 -0800, Tom Harrop wrote:

>
> This brings me to my first question: Is there anything wrong with
> getting two chains and connecting the required length with Power
> Links, so I'd have two Power Links in the one chain?

Not that I can see. With a 7/8 speed chain, you can also join two
chains by pushing out and reinserting one of the pins.

>
>
> In terms of the cassette I'd like to go 7- or 8-speed for chain life
> and hopefully to fix the ghost shifts. Since all the 8-speed cassettes
> I can get locally seem to start with an 11t sprocket, which I don't
> want, my hare-brained plan at the moment is to get the 7-speed 13–28
> that Shimano makes, and since I'd need a 4.5 mm spacer to put that
> cassette on my 9-speed freehub, just use the 36t sprocket from my old
> 9-speed cassette with a 3 mm spacer instead. So I'd have a 13–28 plus
> a 36t 'bailout'.
>
>
> I guess that's a large jump so the shift wouldn't be very pretty, but
> it's not a sprocket I'd use terribly often... or I could always use
> the 32t from my old cassette instead, or take a 34t sprocket from
> another 7-speed cassette. I just thought I'd check with the group to
> see if anyone's done this, before I go ahead and try?

Have you considered the 13-34 "K" cassette? It's an off the shelf
solution that I think will satisfy your range needs.

[PATRICK MOORE]

The rule witth Shimano cassettes and cogs, at least to my admittedly vast experience on the matter, is that you can pretty much swap anything for anything else, **as long as it fits all the way onto the freehub body and as long as you can screw on the lockring without leaving any play in the cassette.**

I've run 10 tooth jumps (eg, 24-34) and many 8 t jumps with all sorts of derailleurs, old and new, Shimano and otherwise, high end and low, with no problems.

Lastly, Miche makes all sorts of weird outer cogs, up to 16 t, for Shimano hubs.

Patrick "variously 13-15-16-17-19-21-26-32, 16-18-20-24-28-34, 13-15-17-19-21-24-34, not to mention my 16-22 Regina six speed fw" Moore

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[dougP]

Tom:

I think you could add some more links.  Many recumbents need about 1-1/2 chains. 

Regarding your cassette idea, I have a similar set-up on my Atlantis.  I use the standard Shimano 7 speed with 13-28 cogs plus a 34 tooth cog from a 9 speed cassette.  The whole thing is spaced using 8 speed spacers.  The crankset is Riv's standard issue Sugino, same as yours.  Shifters are 8 speed indexed Ultegra bar ends, and shifting is flawless.  I think I just got lucky with the ramp locations on the 34 tooth as the shift from the 28 to the 34 often under load & still dependable & quiet.  I use the entire cassette with the middle ring & only avoid the 34 when on the big ring.  Not sure how the Atlantis chainstays compare to yours but I just install a new chain "as is" out of the box.  It's just long enough to handle that unintentional 46 x 34 if it ever happens. 

One thing to look at on your old cassette is whether or not the cogs are solid or are a lot of them mounted on a carrier?  A lot of cassettes save weight by mounting a bunch of the larger cogs onto a carrier. 

If you can live with a bit more spacing between gears, Shimano also makes a 13-34 7 speed.  With the 4.5 mm spacer you could get a useable range & only give up 2 teeth on the bottom end. 

dougP

[Tom Harrop]

Thanks everyone, I appreciate the answers.

Steve—I did consider the 13–34 and it's still a possibility, but it seems that I'd be swapping a useful gear in the middle of the cassette for the a spacer. If I add a large sprocket to a 13–28 then the large sprocket goes where the spacer would be. Plus I already have a never-used 36t sprocket on my current cassette.

I also didn't know you could re-use the pins on an 8-speed chain, that's useful info because it means I'll have a complete chain with master link left over for my other bike.

Patrick—good to know that it should shift. I guess the 36t from the 12–36 9-speed is designed for shifting from a 32t, so it will have two ramps... but I don't mind how nicely it shifts, just so long as it does! I did have a look for Miche sprockets but I can't seem to find them here.

Doug—the new chain I bought with the bike (SRAM 9-speed) was about 2 inches too short out of the box, and I've since checked and those chains come with 114 links (57 inches), so I think I'll need an extra 4. I measured my 68 cm Bombadil's chainstays as 47 cm, and Riv's geometry chart says Atlantis's are 44 cm on the smaller ones so I guess that's the difference.

According to Sheldon's website the 36t sprocket on the 12–36 is unattached, so I should be OK. Just need to get a 3 mm spacer in there, although I may get away with the 9-speed spacer because Sheldon also says that 9-speed cassettes are spaced at 4.34 mm...

I have to say I've never thought about gearing in-depth before so this may be fairly stupid. I usually just get a cassette that has the range I want and forget about spacing. But I'll give it a try, and if it doesn't work the 13–28 can go on my 1×7 commuter and I'll buy a 13–34 7-speed instead.

Thanks again for the help.

Tom

[Ron Mc]

I have two power links in my chain and it works just fine.  

I think if you sat down with a gear calculator and went through your gear inches, you would be surprised how many overlaps you have and how few effective gears you actually have.  A recommended exercise, and look at look at changing your front chainrings to eliminate the overlaps.  

[Tom Harrop]

You're right, I would be perfectly content with the 13–34. I'm no gear-ratio perfectionist, and I don't even know what the steps on my current cassette are, but it seems easy enough to slip the extra sprocket on the freehub so I may as well try it. Because I'm a lazy shifter, and I don't often shift at the front, I tend to use the three chainrings as 'sets' of ratios—stay in the big ring for cruising, middle if I'm off pavement, carrying stuff or it's windy etc., small for really steep hills—so I don't really mind having gears that are duplicated between the 'sets'. I would never make a front shift just to fill a gap between cassette sprockets! Far too lazy...

Thanks again for the input.

Tom

[Ron Mc]

For me, it's a case of necessity - not so much perfectionism.  I ride the Texas hill country on a '76 Nottingham Raleigh.  Not comparing myself, but this is where Lance developed his cooling system.  My old bike has 122mm dropout spacing, and the only way to get more than 5 gears in there would be a major wheel revision.  With 42/52 chainrings, and 13 to 28  in the rear, and I discovered I only had 5 effective gears, and nothing between 70 and 88 gear-inches.  I replaced my front chainrings with 41/46 (144bcd - I know, I could have replaced the crank, but I like it).  I ended up with 9 effective gears, all evenly spaced, and 3 of them between 70 and 88.  

[Tom Harrop]

Yep, for some people it's definitely necessary to optimize gearing.

What model Raleigh is it? My commuter is a '74 Nottingham Raleigh, but it's a lead-pipe Grand Prix

[Ron Mc]

Lead pipe Grand Prix.  Nottingham May '76.  Bought it at the West End bike shop in Nashville that fall when I attended Vandy.  But it's still not that bad - rigged out it's a 25-lb.bike, and it's carried my 200+ lbs for 37 years.  Of course always stored indoors.  It's had steady rebuilds over the years.  Climbing TX hills, the original splined crank stripped out early.  At the UT Co-op bike shop, all the employers were racers, they won parts and sold them in the shop for cheap.  So I bought the Sugino Mighty Comp.  Then had a set of wheels built on Zeus Grand Sport hubs with Rigida 1320s.  It's these wheels that make the bike.  The builder reversed the spokes to make them stronger for my large size, and I'm still riding them - in fact, whatever he did make a granite set of lightweight wheels (I rub the carbon steel spokes with Boeshield) .  (Recently bought a NOS set of 1320s and some decent used Campy wide flange GS hubs and have a second set of wheels with cross tires for when ride ranch roads.)  Shimano 600 Arabesque derailleurs, and most recently my upright rebuild with Tecnomic, Moustache and bar-end - still with my Zeus levers.  In fact the only original parts on the bike are the headset (still great) and Weinmann center pulls.  Found my TA Grand Sport chainrings in Germany for $60 total, and love my 9 useful gears (the overlap is the 28 rear on either chainring), but the 9 evenly-spaced gears are great.  

Sorry, the photo doesn't show my new 46 front.  It has plenty of marks in the paint, but what's left still takes a wax and looks striking even with its mars.  

If I ever get around to repainting it, I stole a set of Zeus dropouts on ebay and will also have lugs added.  I used the long stays on my Nitto front, and Acorn leather washers to fill the gap between the dropout lugs and forks.  In fact, I've become an Acorn leather washer junkie - I''ve found a thousand M5 uses for them.  The shorty fenders are the alloy Blumels, which also look pretty cool - and they keeps the brakes clean. 

My real bike money goes into my daughter's bike, though I will eventually have an AHH.  

But my lead pipe Grand Prix is still a cozy ride.  

[Tom Harrop]

Wow! That has to be the nicest looking GP from that era that I've seen. I'm really fond of mine too, but it was in pretty awful condition when I got hold of it a few years ago, so most of the original parts were rusted and had to go, except the headset. It's also too small for me, so it does duty as an around-town bike with a rack and albatross bars.

I like how you've done the front rack, I could use a basket on mine. Is that a Mark's rack?

[Ron Mc]

hi Tom, 

Nitto M 18.  I ordered the long Nitto stays from Rivendell.  In fact they were out of stock when I inquired with Spenser.  He gave me an estimate of when they would restock, and contacted me when they arrived.  Spenser has always done extremely well by me, his kind of service will keep me buying there.  I did have to cut about an inch from the long stays for my set-up.  

I could have spent less and used the Grand Compe ENE mini rack on my Weinmann brakes, but I like my Nitto rack.  

http://velo-orange.blogspot.com/2010/08/grand-compe-ene-mini-rack-details.html

my rear rack is an original Jim Blackburn from 1978 or so, and I like it, too.  

As I said, I bought mine new in 1976, and it was, and still is, all about the fit.  

And thanks for your kind words.  

Ron 

[Ron Mc]

As I said, I've become a junkie for Acorn leather washers.  

Here is the leather washer spacing between the front dropout lug and long rack stay

and a novel use for them - on the Bell 11 from Rivbike, it dampens out 90% of the road shock rings, and makes a nice bridge for your thumb

To adjust fender spacing on my daughter's bike, I used a long M5 and a stack of spacers with a long M5 going into the bottom bracket boss

And attaching stays to frame bosses, it absorbs misalignment, distributes the contact stress, and as it compresses it becomes a lock washer

and of course the obvious spot on a fender stay

apologize for the welded aluminum frame, but my daughter is riding 20 miles and climbing hills on her Nexus 8 - with a slight modification - I reduced her front chainwheel to 42 and increased her rear sprocket to 26, keeping the same chain length and turning her bottom two gears into tree climbers.  She still hasn't been into the top two gears, but she'll eventually want to go faster. 

 

[Tom Harrop]

Just thought I'd update this thread in case someone else googles it up. I made the switch to a 7-speed 13–28 HG cassette plus a 36t sprocket and a SRAM 8-speed chain. To put it scientifically, I would say the drivetrain feels a bazillion times better. No more ghost shifting or chain skipping under load. The shift from the 28 to the 36 is just fine by my standards.

I'm afraid it wasn't a very scientific experiment—aside from the new chain and cassette I also switched the bottom bracket cable guide, which didn't look like it was guiding the cables very smoothly (unless two 20° bends are a good thing), so that could have been partly responsible for the ghost shifting. Anyway, I'm happy and I won't be going back to 9 speed anytime soon. The 'frankencassette' looks bizarre with 7 black sprockets and the silver 36t, but I can't see it when I'm riding, as they say.

Thanks again for the input!

[Ron Mc]

looks like a great solution, Tom.  

here's my gear-inch chart on my 5-gear rear sprocket and two close chainrings.  

the 20-16 is a cliff.  

41 12.2 % 46 28 39.5 44.4 16.7 % 24 46.1 51.8 20.0 % 20 55.4 62.1 25.0 % 16 69.2 77.6 23.1 % 13 85.2 95.5

but resulting 40 to 96 gear-inches, and very even spread - everything is useful with no overlaps.  

and here are my good-looking close-ratio chainrings. 

[Jeremy Till]

I'm a bit late to this thread but just to chime in and say that SRAM makes extra long chains (120 links).  They're often labelled "29er specific" since chain length is a common issue with many 29ers, not just the Bombadil. 

On Thursday, December 27, 2012 9:55:22 AM UTC-8, Tom Harrop wrote: