John N

I am currently coming up with the specs I want on a custom expedition touring bike. I am strongly considering a Rohloff. However, I also have a high cadence (105-110) so I really like small steps in gearing.

Is there any reason I can not use a front derailleur with a Rohloff?

I understand this somewhat defeats the purpose of the "no derailleur needed" benefit but the 13% jumps are not fun to me. Of course I would need to use a chain tensioner and the chainstay would be quite long at about 49 cm (over 19") so I would have some room to play with the chain line. The rear dropout would be a Rohloff OEM fitted with a standard rear derailleur hanger.

I would probably use a 32/34 on the front with a 16 tooth on the back. Yes, I know these are really low grears but that is what I use/need/want. Should I spin out on the top gear and I would be going about 26mph which is plenty fast for me on a fully loaded bike. I also understand this would be a "not allowed" low low gear.

Thanks in advance!

ShimmerFade

Should be fine. I use a chain tensioner with my Alfine with a 34/48. For me a Rohloff alone would probably be more than enough, but with the 8 speed Alfine, the extra gears are very useful for climbing and the high top end is also nice going down hills. I was actually born in Tulsa, and broke in this set up there last month actually. If you ride on the river ever then I can say that on the west side of the river going up those three hills before 71st I need the 34t with the Alfine. I haven't had to use the 34t since I have come home to Germany, but I plan on taking on the hills here once I get over my cold..they are quite a bit more intense than in Tulsa so I think the 34t will really come in handy.

MichaelW

There some bottom bracket/crankset internal/planetary gearing solutions that maintain chain tension.
Schlumpf
Truvativ HammerSchmidt
Bionicon
Metropolis PT

ShimmerFade

Do you mean even with a front derailleur and 2 or 3 chain rings? That would be an interesting solution...probably way beyond my budget if it actually works. I thought those things were just used on a bike that doesn't have a horizontal dropout.

tatfiend 

So basically you want to use half step gearing on the front to give you about 6.8% steps between gears. No reason it should not work theoretically though with the Rohloff chain line you may want to use a longer than standard bottom bracket axle with the crankset. The Rohloff chainline is 54mm IIRC which is about the same as the outer ring chainline on a triple crankset when normally installed. I would suggest using the Rohloff chain tensioner.

One difficulty you almost certainly will run into is finding a front derailleur that mounts low enough to work with 32 and 34 tooth chainrings. Normally the tail end of the derailleur cage is going to hit the chainstay long before the derailleur is low enough to be at the correct height for use with such small chain rings. Even changing to 17 to 34/36 gearing is not going to help this much.

MichaelW's idea of the two speed planetary geared crankset will not work as you want minimal steps between gears while the two speed geared cranksets all have very large steps between their two ratios.

BTW have you actually tried the Rohloff hub gearing? In the lower gears I find it to be more than close enough so the steps are not objectional at all.

eldenh

Rohloff says not to use less than 38t with 16t rear. It is still possible to get low gearing within Rohloff guidelines by using smaller wheels.

John N

Yep, it would be a rohloff in the rear and a double crank up front. The frame would have an rohloff dropout but with a hanger attachment.

John N

I thought this might be a problem and I am trying to figure a solution to this. I have thought about messing with a derailleur to see if I can make it work. Any suggestions or derailleurs (even old stuff) that might work?

I think I can go with the Thorn 21t cog and 42/45 rings but wanted the smaller chainrings due to clearance.

I was also trying to figure if I need to have the chainline on the main (inner) ring or in between the two rings or ????.

Why oh why is everything I want to do never simple

John N

Are you talking about the bike path or Elwood Ave. (Turkey Mountain)? The path going southbound is a bit a climb with full packs. Going northbound on Elwood between 71st to 61st is not something I would like to do with full packs!

We were in Europe this summer for a month and I really want to go back and tour in Germany and Austria. However, I am not so sure of Italy as the drivers are CRAZY and the roads are pretty narrow.

ShimmerFade

I meant the bike path going to turkey mountain, I wasn't sure if that was actually turkey mountain or not =P. I really like what they have done in that area, I could get in a really nice hour ride starting at the P. bridge at 31st going up to 71st then back down to 21st then again up to the P. bridge. I love being able to just ride, and not have to worry about cars being on the same road as me.

In the post you quoted from me first I was responding to the guy right above me..I didn't express myself very well. I had never heard of a hub in combination with those technologies that he listed, and thought it sounded interesting, but too expensive for me. I run a Alfine IGH with 32/48 rings and a chain tensioner, so the dual ring/chain tensioner system is a cheap way of expanding my gears while maintaining many of the IGH benefits. If I had more bikes I would most certainly leave the hub alone and only have 8 gears on it, but it is my do everything in almost any weather bike.

In the right time of the year the weather and terrain in the not so flat parts of Germany are perfect for riding. I have never been to Italy, but I have heard many sad and crazy stories of people getting messed up over there on/in anything with wheels.

pwdeegan

since you are interested in having a double chainring for issues of cadence—meaning you plan to switch between the two rings frequently—i would run the ideal 54mm chainline between the two chainrings.

as for other odd ideas, White Industries manufactures a unique crankset called the Double/Double (scroll to the bottom of the page). the chainrings are 34/31, and their close proximity to one another would be ideal for ideal-chainline situations (it is made for a SS, after all). the problem in your case is that i doubt there is an OEM derailleur that would work for this (you can always make something yourself, if no one else makes it for you).

Elkhound

Try a Schlumpf.

tatfiend 

Will not do what the OP wants. He wants half step gearing from the front changer to give very small steps between gears. The Schlumpf, and other two speed planetary front cranksets, are all wide range.

fietsbob

With a 16t cog the smallest chainring is spec'd to be a 38.. with a 15t its 36t, 17, a 40t.

there is a double reduction gear for 1-7, a single reduction gear for 8-10, 11 is direct , 12-14 is overdrive.

so cog #2 would be 6.5% larger than the minimum specified external drive ratio..
2.35:1 for a single

2.5:1 for a tandem, because of torque from 2 riders it raises the low ratio limit..

fietsbob

Ill add with a 26" wheel, 16/38 , 1st gear is 17" much lower and it is difficult to maintain the momentum
to stay up on 2 wheels..
as an experiment I got a mountain tamer Quad, and set up a 16t in front and the 28t on the wheel [14.8"]

restarts on a hill were nearly impossible as there was such small movement
up the road , with each crank rotation,
the momentum dropped to zero
before I could get the other foot on the pedal.. and perhaps, clipped in..

3 wheels and you can gear low because you won't fall over twiddling a 10 inch gear, slowly winching up the hill

the chain feels like rubber then too..

I use the two feet gear for hills all the time now , as I live on one..