Triple to double conversion

[maxcr]

I have a couple of fun cranksets and I'm contemplating a few ideas for which I'd love your input.

Crankset 1. Ritchey Logic Compact crankset with 42/32/22 chainrings 94/58 bcd.

Crankset 2. Suntour XC Pro crankset with 46/36/24 chainrings power ring 110/74 bcd (I actually bought a few things with this, mtn thumb shifters (7 spd), rear derailleur, rear hub, freewheel - all XC Pro)

I'm perfectly content with the Sugino triple 46/36/24 on my Bombadil and I actually have nothing against triples, but I'm contemplating converting one of the cranksets above to a double just because who doesn't need a project to tinker with your Riv?

The bike is a do-it-all All Rounder, so I want to have wide gearing range, something like a 42/32 double with a 12-36 cassette would accomplish that for me. A 46/36 might not quite cut it, but I could go low low 36-24 too.

Anyway back to converting a triple into a double. As I understand it, there are a few ways to do that:

1) Remove the big chainring (potentially swap it for a chainguard) and call it a day (or change some chainrings)

2) Remove the little chainring and call it a day (or change some chainrings after)

But... not so fast. If I go with option 1 without the chain guard do I need new / shorter chainring bolts? If so, which ones do I get? Are these universal?

Are the pros/cons of either option? Will I run into Q-factor issues, chainline and chainstay / derailer problems? I had read this on an old post: "my Bomba and I suppose a Hunqa frame you are limited to a 36t middle unless you get a wider BB."

So, what about the bottom bracket? Do I need to go narrower to get the right chainline? Or wider to fit the 32?

I tracked down a few conversations from way back, here and in other forums. It seems like the original suggested bottom bracket for these cranks are:

1) Ritchey Logic Double - 110-113mm (this is probably close to what's in there now)

2) Suntour XC Pro - Suntour Greaseguard 122.5mm (I managed to get my hands on one of these)

For the Ritchey as a double (when removing the inner ring) I heard people suggesting a Phil 98mm BB which I cannot find. Another alternative is using a 103mm with some hacks

For the Suntour, I have no idea what is required in terms of BB. Maybe you just have to try a few.

What does the collective knowledge here recommend? Ritchey or Suntour? Remove the outer or the inner?

Thanks

Max

 

[Jim M.]

I used the Ritchey as a double with a 44/32, and a 32 low in the rear. Worked great. I don't remember the bb but it was probably 110. I have no experience with the Suntour, but I found 94 bcd to be more flexible for my needs than 110.

jim m

walnut creek

[Jim M.]

And if you went with removing the inner ring, you'd need single speed chain ring bolts for the middle ring. Not difficult to find.

[Patrick Moore]

I converted my original edition Sam Hillborne from a 46/36/24 triple 7 speed to a 38/24 9 speed very easily. Besides replacing the 14-?? 7 with a 12-?? (much the same range; slightly lower -- 88" versus 92"? -- high, same low, same gaps) I did the following:

1. Removed big ring, replaced with BBBashguard protector.

2. Replaced the 36 with a 38

3. Adjusted the rear derailleur throw (LX --??-- reverse pull, later replaced with a Miche right-way-pull, but my first few hundreds of miles were with the LX RP -- lovely shifting, just backward. The Miche short cage was as-nice shifting and forward).

4. Adjusted the front derailleur throw.

Went off for a ride.

Note that I did not:

1. Replace the crank axle;

2. Adjust the height of the FD. Yes, the outer cage sat cm's high over the 38 but, so what, it was even higher over the 36 and still shifted from 36 to 24 and back just fine; likewise between 38 and 24. Sure, I could have moved it lower except:

1. It had to clear the bashguard.

2. You'd have to be careful about the bottom of the cage hitting the chainstay.

I could have dispensed with the bashguard; the FD didn't care if it was there or not.

I did 'xactly the same thing with the Matt 1:1: transmogrified from 46/36/24 Bontrager triple* to Ritchey Logic 110/74 double, only this time I kept the same Dura Ace 740? fd -- in the same place; it is still there today and it still shifts just fine.

Hah! You try shifting a pipe-spindle MTB triple with a 6? or 7? or 8? (7400?7401?7402? -- would have to check) speed road fd! I cut off the FD's stop to get about a cm more throw. When I went to the Ritchey double the FD had more than ample throw and if I'm not careful it will shove the chain rightward, right over the bashguard. Not really a problem as I am a careful and relatively infrequent shifter and, moreover, the drivetrain is set up as a 1X10 with granny that only rarely gets used. With the current 10 in back the rd is a 7402, tho' it gas also been a 7401 and a 7400.

On Fri, Jul 14, 2023 at 3:01 PM maxcr <max.fai...@gmail.com> wrote:

.... Anyway back to converting a triple into a double. As I understand it, there are a few ways to do that:

[Patrick Moore]

I forgot to paste the photo of the Matt 1:1. I've ordered a 44 to replace the 42 because I recently switched from tires 29 6/10" tall to tires 28 1/2" tall, 622X60 Big Ones to 622 X 48 Soma Supple Vitesse SLs. 42/44 X 13-25 10 speed.

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Patrick Moore

Alburquerque, Nuevo Mexico, Etats Unis d'Amerique, Orbis Terrarum

[Patrick Moore]

46/36/24 to 42/28, 9 speed to 10 speed. 

[Kim H.]

I have a Clem Smith Jr. "L" bicycle. It has a SILVER crankset 110/74 bcd with rings of 34T and 24T. in the rear I have a SunRace 14-42T 9-speed cassette. There is a chain guard on the outer part of the chain rings on the 110 bcd position. I do have for the rear 9-speed drive train a Shimano M591 long caged derailleur with a Wolf Tooth road link. This works for me very well.

However, after reading the business owner of Anolog Cycles, James Johnson's article "Turkey Vulture Gearing 101"( https://analogcycles.com/blogs/news/alternative-gearing-turkey-vulture-turkey-vulture-supreme-turkey-vulture-loco-supreme), I got to thinking about what I had in my parts drawers and what was available online for purchase of a front derailluer. I came up with following:

I have a 172.5mm T. A. Zephyr triple crank set - 110/74/58bcd. I also have a Shimano CX 70 front derailleur. I do have for the rear 9-speed drive train a Shimano M591 long caged derailleur with a Wolf Tooth road link. I have a SunRace 11-40T 9-speed cassette in the rear.

I bought a SILVER chain guard for the 110bcd from Rivendell Bicycle Works. I placed a T. A. 36T ring on the 74bcd and a 20T ring on the 58bcd.

Unfortunately, I, too, have not tried in on my Clem Smith Jr. "L" bicycle at this time, due to the fact that I am not planning to scale any large hills here in the near future. I have been riding on pavement most of the time.

This link might help you, Max:

https://groups.google.com/g/internet-bob/c/mFf6IERVQ_k/m/TEuNok2TAAAJ

Kim Hetzel

Yelm, WA.

[Will Boericke]

Tinkering is maybe the most fun part of bike ownership!  I recently doublized a triple LX crankset (110/74),  Removed big and middle rings, re-installed the big ring on the inside of the outer spider with singlespeed chainring bolts.  So now I have 46/26.  Shifting is fine with a 7700 DA front derailleur, though I did install a chain catcher in anticipation of that 20t chain drop.  Honestly though, I think the catcher has only "caught" the chain once.  With 11-28 out back, it's a great double 1x - nice close gears in both ranges.

Will

[exliontamer]

Speaking from experience, that Ritchey with the 94bcd is not going to give you a good chainline as a double unless you get something very small. People always throw out numbers for the Road & the 110bcd Triple & I promise that it's different. I'm running one with a 46/30 combo on my old Atlantis & a 103 puts in in a barely useable range that I probably still shouldn't be running. The best advice I found, searching through a lot of old messageboards, was to try to find an old Phil Wood or cup & cone in the upper 90s. I'm actually going to change mine back into a triple for all of the above reasons. 

[Garth]

Along the lines of what exliontamer expressed, the bowed out stays of frames like the Bomba and Atlantis don't lend themselves to fufu trendy gearing configurations. Since your current crank isn't broke don't go out to fix it. There is certain efficiency and effectiveness in a 110/74 crank with 24-6/36/46 cranks. They just work and cover any terrain, given a suitable cogset. They shift beautifully.

[Junes]

Exactly, Garth. 

I continue to run triples, so I have viewed the trend toward purportedly simpler drivetrains with curiosity and from a long distance. I have never felt a need to simplify with a double or especially a 1x configuration. It’s basically a one-time setup for the triple, and with friction shifting there’s rarely a need to fuss with any of it again. Set it and forget it. I love the super wide gear range, and I enjoy the mechanics of shifting front and rear.  

I totally understand the urge to tinker and play with different setups for fun and variation, though. But with cranks and front ders I’m either too set in my ways or too lazy to futz around. 

On Jul 15, 2023, at 14:27, Garth <gart...@gmail.com> wrote:

Along the lines of what exliontamer expressed, the bowed out stays of frames like the Bomba and Atlantis don't lend themselves to fufu trendy gearing configurations. Since your current crank isn't broke don't go out to fix it. There is certain efficiency and effectiveness in a 110/74 crank with 24-6/36/46 cranks. They just work and cover any terrain, given a suitable cogset. They shift beautifully.

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[John Hawrylak, Woodstown NJ]

To address the Chain Line Question.  Assuming if you have a PERFECT Front Chain Line (FCL) with the triple (middle ring lines up with middle cog), then If you with:

Option 1, remove Outer ring,     the  FCL needs to shift INWARDS, 1/2 of the spacing between the middle and inner ring.  This is typically 6mm, so you need to shift the crank INWARDS by 3mm.  You need a BB with a drive side distance 3mm less than you have currently.   This will also give you a lower Q.

Option 2, remove Inner ring,     the  FCL needs to shift OUTWARDS, 1/2 of the spacing between the middle and outer ring.  This is typically 6mm, so you need to shift the crank OUTWARDS by 3mm.  You need a BB with a drive side distance 3mm greater than you have currently.   This will also give you a higher Q.

Hopes this helps.  Suggest sighting down the chain to determine if the CURRENT FCL and RCL match or if the FCL is outwards or inwards of the RCL.  If CURRENT is NOT perfect, then Option1 or 2 may result in a better FCL WITHOUT changing the BB

John Hawrylak

Woodstown NJ

[Nick Payne]

I recently setup a bike using some Deore XT 94/58 BCD cranks with a chainguard in the outer position and 38 / 22 chainrings. I made the chainguard from an old 42t Vuelta chainring with the teeth removed. Combined with a Leonardi 9-36 CX cassette, the 38 / 22 chainrings give gears from 115" down to 17". I haven't got anywhere near bottom gear yet - the steepest climb I've taken it up so far was only 12% or so - but I have used the 38 x 9 down a mountain - it's useful for accelerating out of the bends, as it can be comfortably pedalled up to about 65kph or so. The 9 tooth cog feels rough when turning the cranks on the workstand, but the roughness is not noticeable at all when flogging down a hill at high speed. With the Deore XT M739 cranks, I found a 107mm BB gave a good chainline with this setup.

Nick Payne

[Nick Payne]

On Sunday, 16 July 2023 at 10:02:54 am UTC+10 John Hawrylak, Woodstown NJ wrote:

To address the Chain Line Question.  Assuming if you have a PERFECT Front Chain Line (FCL) with the triple (middle ring lines up with middle cog), then If you with:

Option 1, remove Outer ring,     the  FCL needs to shift INWARDS, 1/2 of the spacing between the middle and inner ring.  This is typically 6mm, so you need to shift the crank INWARDS by 3mm.  You need a BB with a drive side distance 3mm less than you have currently.   This will also give you a lower Q.

Option 2, remove Inner ring,     the  FCL needs to shift OUTWARDS, 1/2 of the spacing between the middle and outer ring.  This is typically 6mm, so you need to shift the crank OUTWARDS by 3mm.  You need a BB with a drive side distance 3mm greater than you have currently.   This will also give you a higher Q.

You've got this the wrong way around. If you remove the outer ring, then the crank needs to be moved outwards, because the chainline is now between the two remaining chainrings rather than being on what was the middle ring when there were three. And vice versa if you get rid of the granny.

Nick Payne

[John Hawrylak, Woodstown NJ]

Nick

You are correct.  My explanation is reversed.   Thnaks

John Hawrylak

Woodstown NJ