# 12-42, Seven Speed



## phoenixbikes (Sep 24, 2010)

I filed out a chainring spider I was never going to use so that it fits onto a freehub body. SRAM just introduced an 11 speed casssette with a 42t top cog. Needless to say, it's pricey. Here's a rather inexpensive alternative for a wide range single chainring drivetrain.

The drivetrain is 1x8, using a (3/32) bmx sprocket and some Redline Flight cranks. It's 26x12-15-18-23-28-34-42. The gaps are tolerable. I think I am going to with a 25x11, which will give roughly equal a 32x14. The 25x42 granny is about equal to a 20x34. On the kind of trails where I go on this bike, that gearing is pretty decent for 90% of what I ride.


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## MendonCycleSmith (Feb 10, 2005)

That's awesome. 

Gold star for you


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## mainlyfats (Oct 1, 2005)

The derailleur pulley/chain/42 tooth cog don't jam together and stick? The chain doesn't get caught between cogs? I see what you did there...


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## Fillet-brazed (Jan 13, 2004)

Interesting. Big gaps are not a problem I guess if you're just cruising around. Do you expect the splines you filed on the 42t to hold up to all that torque?


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## phoenixbikes (Sep 24, 2010)

We'll see. I hope so! The gaps are fairly reasonable for the width of the range, in only 7 gears.


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## phoenixbikes (Sep 24, 2010)

mainlyfats said:


> The derailleur pulley/chain/42 tooth cog don't jam together and stick? The chain doesn't get caught between cogs? I see what you did there...


I had a 40t ring bolted to a 34t cog on there 1st. When I took it off and installed the 42t 'cog', I just had to dial out the b-tension screw a bit. The shift from the 34t cog to the 'new' 42t ring is kinda slow, but tolerable.


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## mainlyfats (Oct 1, 2005)

phoenixbikes said:


> I had a 40t ring bolted to a 34t cog on there 1st. When I took it off and installed the 42t 'cog', I just had to dial out the b-tension screw a bit. The shift from the 34t cog to the 'new' 42t ring is kinda slow, but tolerable.


This shift on to the 42 I get (-ish) - it's the shift off the 42 I really wonder about. Anyway... nice work, glad someone still tries.


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## phoenixbikes (Sep 24, 2010)

The shift off the 42 works decently. It does take a bit longer than a typical cog to release the chain but it's not a problem. 

I filed another spider on which I'm using both a 38t ring, and a 42t ring. Both are ramped, so I turned them around to aid shifting under load. That one is an 8 speed setup. The cogs are
11-14-17-21-26-32-38-42.


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## s4gobabygo (Sep 1, 2008)

cool project! any pics of the cassette in profile (showing the gaps)? pics of the chain in the 42t "cog"?


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## jeff (Jan 13, 2004)

How did he spacing between cogs work out?


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## phoenixbikes (Sep 24, 2010)

Here's a pic of the 8 speed setup. The top two 'cogs' are 38t and 42t. I switched them around so that the ramps would aid shifting.

The tabs on the chainring spider are about the same thickness as an 8 speed spacer, so it indexes just fine on the top two gears. I used 9 speed cogs on this one, with 9 speed spacers. 

There is also a spacer behind the spider so that it would work better with 8 speeds. I have run 9 speeds with a thumbie but in friction mode the shifting is a little ponderous. Between the 32t cog and the 38t ring I used two spacers to take up the gap and get the alignment right.

The 2nd pic is of the 7 speed setup, which just needed one spacer between the spider and next cog (34t) to get it right.


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## phoenixbikes (Sep 24, 2010)

Here's a few more pics on a different bike. The 36t 'cog' has oddly shaped teeth but they seem to help shifting under load along with the chainring ramps.

The crankset has some modifications too. The rings are 17/28/44. The granny gear is a 17t 7 speed cog. I cut an old freehub body in half. It has external threads so I used a bottom bracket lockring and a cog drilled with a 5 bolt 58mm bcd to hold the very short section of freehub body on the crank. I then mounted the cog, and cranked it down with a lockring. I've done a number of these cog-to-chainring conversions before, mostly with 18t cogs. 

The middle ring is a 28t 74mm bcd unit. Finding 29t 94mm bcd rings is hard and they can be pricey. 28t 74mm rings are common so I altered one to work with my 94mm cranks. The 28x42t combo really extends my climbing range in the middle ring.

The 17x42 granny gear on my 29er is great. It's probably the lowest gear mechanically possible with a standard derailleur and chain drivetrain. I won't be needing the 17x42 much this winter but next summer having a super low bailout gear at high elevation will be sweet.


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## -Anomie- (Jan 16, 2005)

Glad I saw this thread, just last night I was thinking about doing something similar to make a 10 speed cassette with a 42t big cog so I don't have to buy a new drivetrain, shifters and rear hub to work with a single chainring set-up. Now I have some ideas and photos to work from, thanks.


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## phoenixbikes (Sep 24, 2010)

Here's another idea. This one works pretty well. I found a 3 bolt ring and drilled 3 holes in a 34t cog. I then attached the 40t ring with chainring bolts and washers to act as spacers. 

The stack in this picture runs 11-14-17-20-24-30-34-40


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## goto11 (Jun 12, 2009)

Only goes up to 34T, but here's a cheap alternative: Shimano HG41 8 Speed Cassette > Components > Drivetrain > Cassettes | Jenson USA Online Bike Shop


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## phoenixbikes (Sep 24, 2010)

Don't really see the relevance.... sorry.

The point I was trying to make here is that it is possible to go much bigger than 34 teeth, in seven or eight gears, with a little creativity.

Also, SRAM just made a cassette with 42 teeth. This is a low priced alternative for people with some fabricating/modification skills.


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## goto11 (Jun 12, 2009)

Yeah, my post was pointless. I had thought those MegaRange cassettes went higher when I googled them, but posted the link anyway. 

I've been mixing and matching cogs to build my own gear ratios for ages. It seems like 40 tooth cogs would sell. As much as I like to fabricate things, I'm not inclined to spend hours filing to make my own, though. But I respect the ingenuity. Interesting thread.


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## shiggy (Dec 19, 1998)

goto11 said:


> Yeah, my post was pointless. I had thought those MegaRange cassettes went higher when I googled them, but posted the link anyway.
> 
> I've been mixing and matching cogs to build my own gear ratios for ages. It seems like 40 tooth cogs would sell. As much as I like to fabricate things, I'm not inclined to spend hours filing to make my own, though. But I respect the ingenuity. Interesting thread.


There used to be 5-speed freewheels with a 36 or 38t large cog. I had one but never used it. A 14 or 15t small cog.

Action-Tec stills offers ti cogs up to 39t
http://www.actiontec.us/prices.htm


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## patineto (Oct 28, 2005)

phoenixbikes said:


> The crankset has some modifications too. The rings are 17/28/44. The granny gear is a 17t 7 speed cog. I cut an old freehub body in half. It has external threads so I used a bottom bracket lockring and a cog drilled with a 5 bolt 58mm bcd to hold the very short section of freehub body on the crank. I then mounted the cog, and cranked it down with a lockring. I've done a number of these cog-to-chainring conversions before, mostly with 18t cogs.


I know you like to make your own stuff (great job by the way), but just FYI they use to make a small chainring set up call "Mountain tamer quad kit" like the name emplys it was a 4th chainring that you install with a wider axle..

I have one with a 17t but I think they make them even smaller..


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## shiggy (Dec 19, 1998)

patineto said:


> I know you like to make your own stuff (great job by the way), but just FYI they use to make a small chainring set up call "Mountain tamer quad kit" like the name emplys it was a 4th chainring that you install with a wider axle..
> 
> I have one with a 17t but I think they make them even smaller..


The Mt Tamer used freewheel cogs. IIRC 16-19t (maybe 20t) Mallard cogs.


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## smilinsteve (Jul 21, 2009)

phoenixbikes said:


> I filed out a chainring spider I was never going to use so that it fits onto a freehub body.


By hand? It looks like a pretty clean job!


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## patineto (Oct 28, 2005)

shiggy said:


> The Mt Tamer used freewheel cogs. IIRC 16-19t (maybe 20t) Mallard cogs.


Sorry I forgot to mention the threaded cogs..

Actually I remember a "updated" version (or maybe from a different company) that used cassette cogs and a cir-clip to hold them tight, or maybe I was just dreaming of how to make it better, in any case I don't remember..


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## shiggy (Dec 19, 1998)

patineto said:


> Sorry I forgot to mention the threaded cogs..
> 
> Actually I remember a "updated" version (or maybe from a different company) that used cassette cogs and a cir-clip to hold them tight, or maybe I was just dreaming of how to make it better, in any case I don't remember..


There were two versions of the Mt Tamer, threaded and unthreaded.


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## phoenixbikes (Sep 24, 2010)

patineto said:


> I know you like to make your own stuff (great job by the way), but just FYI they use to make a small chainring set up call "Mountain tamer quad kit" like the name emplys it was a 4th chainring that you install with a wider axle..
> 
> I have one with a 17t but I think they make them even smaller..


I have one on another set of cranks. I also have a couple White Industries Limbo Spider, which also uses Suntour A-type freewheel cogs. Finding a splined 17t cog is very hard, so I am in the process of turning a 17t cassette cog into a splined freewheel, with a bench grinder and some hand files.

smilinsteve, thanks, I did do it by hand.


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## phoenixbikes (Sep 24, 2010)

patineto said:


> Sorry I forgot to mention the threaded cogs..
> 
> Actually I remember a "updated" version (or maybe from a different company) that used cassette cogs and a cir-clip to hold them tight, or maybe I was just dreaming of how to make it better, in any case I don't remember..


If you can remember the name of the company please let us know! It seems like a no-brainer for someone to come out with a small bolt-on spider like the Mtn Tamer that uses cassette cogs instead of hard to find freewheel cogs with the right spline pattern.

The Mtn Tamer Triple and the White Industries Limbo Spider both use circlips. Never seen a threaded version of either Mtn Tamer adapter. Anyone got a picture ?


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## shiggy (Dec 19, 1998)

phoenixbikes said:


> If you can remember the name of the company please let us know! It seems like a no-brainer for someone to come out with a small bolt-on spider like the Mtn Tamer that uses cassette cogs instead of hard to find freewheel cogs with the right spline pattern.
> 
> The Mtn Tamer Triple and the White Industries Limbo Spider both use circlips. Never seen a threaded version of either Mtn Tamer adapter. Anyone got a picture ?


The small cogs will not clear current BB/frame designs. The BB cups/shells are too large diameter and too far outboard.


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## phoenixbikes (Sep 24, 2010)

I can imagine there are some clearance issues.

I'm running a Mtn Tamer Triple with 18/26/38 rings on my 2012 Santa Cruz SL 29. 

A splined 17t cog would work just fine if I could find one.


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## goto11 (Jun 12, 2009)

*It was bound to happen sooner or later*

OneUp Components Offers Granny Gear for SIngle-Ring Fans







It seems like it would work with 7 or 8-speed n-36 cassettes, with the correct spacers.


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## Fillet-brazed (Jan 13, 2004)

goto11 said:


> OneUp Components Offers Granny Gear for SIngle-Ring Fans
> View attachment 851403
> 
> It seems like it would work with 7 or 8-speed n-36 cassettes, with the correct spacers.


Now you'd just need the 10t cog...

My prediction is the 1x cassette will eventually have a range of 10-46 or so to at least get close to the range of a 2x system.


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## phoenixbikes (Sep 24, 2010)

Sweet. Might have to get one! Hope they are not boat anchors. I have a mtbtools 41t cog currently but it weighs over 200 grams and it's flimsy.


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## -Anomie- (Jan 16, 2005)

Fillet-brazed said:


> Now you'd just need the 10t cog...


Time to dig around and try to scrounge up a 10t "Steve Hegg" cassette cog (by SRP, I think). Haven't seen one in years, but there has to be a few out there somewhere (famous last words ).


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## phoenixbikes (Sep 24, 2010)

Interesting. Did it fit on a standard freehub body ?


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## Like2Hike (Jan 12, 2016)

phoenixbikes said:


> I filed out a chainring spider I was never going to use so that it fits onto a freehub body. SRAM just introduced an 11 speed casssette with a 42t top cog. Needless to say, it's pricey. Here's a rather inexpensive alternative for a wide range single chainring drivetrain.


Do you remember the crankset that the 42T cog came from? How would I find one or similar?

Love this thread and I admire your handiwork.


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## phoenixbikes (Sep 24, 2010)

The chainring on there was never attached to a crankset. If you try it, you might use a Dimension chain ring, as the teeth are shorter than on other rings. Pork Chop BMX also makes some great rings that function well as cogs. 

Funny, these 'homemade' rings have never bent. One up's cogs are a bit fragile in comparison.


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## Like2Hike (Jan 12, 2016)

Pork Chop BMX had a ton of similar rings, mostly used which is fine. I have two 5-bolt crank ghetto bikes, perhaps a suitable spider?

Thanks for the lead.


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## phoenixbikes (Sep 24, 2010)

Mostly used? I believe there are probably lots of brand new ones on ebay. Here's a 40t for example:

Porkchop BMX Single Speed Bicycle Chop Saw I Chainring 40T 110 130mm BCD Gold | eBay

The spider I used was a cooks model. I have used a number of others however. Redline for instance, Gt, etc. The Gt spider if I remember right was a little thinner. Getting the hole centered just right, and the hand file work is the hard part.


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