Multi Gear Singlespeed Question

Phil B. said:

Before I even start...yes I do own derailleurs, including the four I
took off two of my bikes. And no I don't have any personal issues
with shifting while riding. I've got afew bikes that do. It's just
the simplicity that seems so attractive. That is until it got
complicated. Now the question:

I've got a flip flop White Industries hub on an older mountain frame
with 135 spacing that I'm using with one of their double freewheels
17/19. (they make nice stuff) On the other side a fixed 15 tooth
sprocket.

For cranks I have an old set with 103/74 BCD and a 40T mounted on the
inside as you would a middle chainring. I've also got a set of
compact XT's with a 32 mounted in the same fashion. The idea, not at
all original, was to utilize two chainrings on this rig.

My intention was to run free 32X17/19 and fixed 40x15. I think the
chain lengths will work but don't know for sure yet.

32+17=49
40+15=55 so both of those combinations will use the same chain length.

55 - 49 = 6 teeth difference

Each tooth needs to move the axle 1/8", so you'd need 3/4" of adjustment
for that.

If your fork ends have horizontal-ish slots that long or a bit longer,
it should work.

If you're talking about one of the ENO eccentric hubs with vertical
dropouts, it won't work, those only give 15 mm of adjustment.

Quoted message said:

My question is
would it be better to use the 103/74 cranks with the 32T in the granny
position or the XT's with a 40T in the outer position. In either case
I'll have to buy one chainring.

The XTs would be a neater setup, only one set of stack bolts, no
unsightly unused outer "ledges" on the crank spider.

However, the more important issue is chainline.

White Industries singlespeed hubs are intended for about a 47.5 mm
chainline with a singlespeed freewheel or typical fixed sprocket.

The double sprocket pretty much splits the difference, giving chainlines
of about 45 & 50.

It might actually work out better to run the chainrings backwards, 32
outside and 40 inside, and flip the fixed sprocket over backwards to
line it up with the 40. Careful choice of bottom bracket length (or,
better yet, an adjustable BB like a Phil Wood) could dial the chainline
in. The fixed chainline is more critical than the freewheel chainline.

You might find some of the reference material in my Chainline article
useful:

http://sheldonbrown.com/chainline

I'm planning a similar setup on my Quickbeam as soon as we receive 16-18
freewheels from White Industries (we've got 17-19, but that doesn't
float my boat.)

I run 40/14 fixed, and have a 33 tooth inner chainring. Currently the
bike has a 18 singlespeed freewheel. The 33/18 is fine for off-road
use, but 40/18 is a maddeningly low gear for road use, for me at least.

Sheldon "http://sheldonbrown.org/quickbeam" Brown
+------------------------------------------+
| The lower your gear, the more of your |
| riding time will be spent going uphill. |
+------------------------------------------+
Harris Cyclery, West Newton, Massachusetts
Phone 617-244-9772 FAX 617-244-1041
http://harriscyclery.com
Hard-to-find parts shipped Worldwide
http://captainbike.com http://sheldonbrown.com

Sheldon Brown said:

Sheldon "http://sheldonbrown.org/quickbeam" Brown
+------------------------------------------+
| The lower your gear, the more of your |
| riding time will be spent going uphill. |
+------------------------------------------+

Is this right? If I run a lower gear, I spend about the same amount of
time going uphill, but more time going down, e.g. I top out at about
30mph on 66" fixed on my hack bike, but about 38mph on 85" on my fixed
wheel TT bike, but I go uphill about the same speed on either bike. So
my experience would be the exact opposite of your quotation. On the
other hand, the lower your gear, the more of your going uphill time
will be spent riding (as opposed to walking) :-)

Kinky Cowboy*

*Batteries not included
May contain traces of nuts
Your milage may vary

Sheldon Brown said:

Phil B. said:

The idea, not at
all original, was to utilize two chainrings on this rig.

My intention was to run free 32X17/19 and fixed 40x15. I think the
chain lengths will work but don't know for sure yet.

Quoted message said:

32+17=49
40+15=55 so both of those combinations will use the same chain length.

55 - 49 = 6 teeth difference

Each tooth needs to move the axle 1/8", so you'd need 3/4" of adjustment
for that.

If your fork ends have horizontal-ish slots that long or a bit longer,
it should work.

If you're talking about one of the ENO eccentric hubs with vertical
dropouts, it won't work, those only give 15 mm of adjustment.

Yes, I was referring to the ENO, so I guess I'll have to modify my
tooth count. Perhaps a 40X13 which is a bit larger than I'd like to
push all day, and a 34X17/19.

Quoted message said:

Quoted message said:

My question is
would it be better to use the 103/74 cranks with the 32T in the granny
position or the XT's with a 40T in the outer position.

Opps, I meant a -130-/74 BCD.

Quoted message said:

The XTs would be a neater setup, only one set of stack bolts, no
unsightly unused outer "ledges" on the crank spider.

However, the more important issue is chainline.

White Industries singlespeed hubs are intended for about a 47.5 mm
chainline with a singlespeed freewheel or typical fixed sprocket.

The double sprocket pretty much splits the difference, giving chainlines
of about 45 & 50.

It might actually work out better to run the chainrings backwards, 32
outside and 40 inside, and flip the fixed sprocket over backwards to
line it up with the 40.

That makes a lot more sense than anything I could think up.

<snip>

Quoted message said:

http://sheldonbrown.com/chainline

I'm planning a similar setup on my Quickbeam as soon as we receive 16-18
freewheels from White Industries (we've got 17-19, but that doesn't
float my boat.)

I run 40/14 fixed, and have a 33 tooth inner chainring. Currently the
bike has a 18 singlespeed freewheel. The 33/18 is fine for off-road
use, but 40/18 is a maddeningly low gear for road use, for me at least.

Sheldon "http://sheldonbrown.org/quickbeam" Brown

A very intriguing bike, if only I could get a 700c wheeled frame to
fit me.

Thanks for your input.
Phil

Quoted message said:

+------------------------------------------+
| The lower your gear, the more of your |
| riding time will be spent going uphill. |
+------------------------------------------+
Harris Cyclery, West Newton, Massachusetts
Phone 617-244-9772 FAX 617-244-1041
http://harriscyclery.com
Hard-to-find parts shipped Worldwide
http://captainbike.com http://sheldonbrown.com

Phil B. said:

Quoted message said:

Quoted message said:

My question is
would it be better to use the 103/74 cranks with the 32T in the granny
position or the XT's with a 40T in the outer position.

Opps, I meant a -130-/74 BCD.

No way. 130 is a "road" type crank.

Older XTs would be 110/74, (minimum size 110 ring is 33 teeth.)

Later 5 bolt ones would be 94/58 (minimum 94 is 29 teeth)

Even newer 4- bolt ones would be 104/64 (minimum for 104 is 32)

Sheldon "XT, XT Or, Perhaps, XT?" Brown
+-------------------------------------------+
| Good judgment comes from experience, |
| and experience comes from bad judgment. |
| --Fred Brook |
+-------------------------------------------+
Harris Cyclery, West Newton, Massachusetts
Phone 617-244-9772 FAX 617-244-1041
http://harriscyclery.com
Hard-to-find parts shipped Worldwide
http://captainbike.com http://sheldonbrown.com

Sheldon Brown said:

Phil B. said:

Quoted message said:

>My question is
>would it be better to use the 103/74 cranks with the 32T in the granny
>position or the XT's with a 40T in the outer position.

Opps, I meant a -130-/74 BCD.

No way. 130 is a "road" type crank.

Older XTs would be 110/74, (minimum size 110 ring is 33 teeth.)

Later 5 bolt ones would be 94/58 (minimum 94 is 29 teeth)

Even newer 4- bolt ones would be 104/64 (minimum for 104 is 32)

Sheldon "XT, XT Or, Perhaps, XT?" Brown

Actually, I may not have made myself clear.....

The crank choice was either the XT compact or an older Sakae off my
'92 Bridgestone RB-T(riple). The chord lengths between fixing bolts
are indeed 76.?mm and 43.5mm making it a 130/74.

The XT was the one I chose, as I like the idea you mentioned with the
smaller ring on the outer position, and found a 32T that looks like it
will work. I've got a 36T chainring on there now on the inside
position using a fixed 15T cog and the same chain length as the
32x17/19 so it's looking good provided there is a decent chainline.
The fixed chainline is perfect, I think it's about a 112mm length BB.

Some longer chainring bolts and I can try it out.

Thanks for your help Sheldon.
Phil