What Cranks do you like with Hub and 68mm Bottom Bracket

[Recumbent Bicycle Source]

This is kind of a General Question to catch me up to speed on Crank/Bottom Bracket Combos now that my bike is more than a decade old and parts are worn.

I'm currently riding a Shimano 105 Road Triple 175mm (52 46 30 I believe) Octalink 1 with 68mm Bottom Bracket. I have a fairly new XT Cassette on the back so I'm mixing road with mountain... but the rear cassette offers me plenty of gearing with only a single ring up front (Almost always the 46).

I seldom shift off of the 46 Tooth Center Chain ring.

I also just picked up a Townie 7 speed with a Single Chain Ring up front and no derailleur. I like it a lot. Which makes me want to go to a single up front on the recumbent.

My recumbent has a "complicated" chainline and I'm running a front hub motor. I really don't need anything more than a front single, and don't need the front Derailleur. But I do need the chain to stay on, and it sometimes "hops" gears when I hit bumps.

So the question is if I pull the Old Triple Octalink, but I want to keep the 9 speed chain and rear derailleur and Cassette what are good options?

I can spend anywhere up to $350 US... so there should be options in the price range. And I don't really care about the weight for this purpose... just good bearings and quality.

The Raceface Narrow/Wide singles are 32 or 34 teeth... which would mean a higher cadence. A 42 to 46 tooth would be my preference.

I've looked at a Shimano Double Mountain Bike Crank... cheap and seem good, but not single. But maybe still an option.

So bottom line is what is a good bottom bracket/crank combo for 68mm? Octalink seems very dated. I have all the tools to pull it... but what will I need to install a new bottom bracket. Should I be looking at SRAM or Shimano or 3rd party?

Suggestions? Ideas?

PS: I ride 175mm cranks, but have no problem going to 170mm or even 165 if it makes sense. Honestly with the motor I just spin for exercise and keep a steady cadence for the same reason. I don't really need to pedal, I just like to.

 

[majornelson]

I'm not that familiar with recumbents but I had a similar situation with an older 1984 Schwinn Super Sport. I went to a single up front and went from 6 to 7 speeds in the rear.

For my Schwinn, I was able to remove the other chainrings and just kept just the larger one. I had to buy new bolts but it worked perfectly. If you're happy with the 46 tooth ring I believe you could do the same. (Again, I'm hedging a little as I don't have your setup exactly.)

The new bolts I used are these ones:
https://www.amazon.com/gp/product/B0025UM6H8/ref=oh_aui_search_detailpage?ie=UTF8&psc=1

These are for Sugino. I would search for Shimano. Or you could add washers for spacers.

As to the rear gearing, you could drop to a 7 or 8 speed cassette. This sometimes means a change to the shifters and chain. You can also space the single ring with washers to properly align it with your rear cassette.

Bottom line (and I could be wrong on any of the above), I don't think you need to change everything. And a good bike shop should help you determine the best approach for the lowest cost and performance.

Good luck.

Lee

PS See my build here. If you look closely you can see I removed the front shifter and one ring:
https://endless-sphere.com/forums/viewtopic.php?f=3&t=84433

 

[Lurkin]

Agreed. New chainring and bolts should do it. May be possible to use washers to take if the difference in the current bolts if need be.

 

[ScooterMan101]

Examples are ...


http://www.jensonusa.com/Shimano-BBR60-Ultegra-Bottom-Bracket?cs=Black

And

https://www.merlincycles.com/shimano-cx50-cyclocross-chainset-65083.html?utm_campaign=googlebase-US&utm_source=googlebase&utm_medium=shopping&utm_term=Road+Bike+Chainsets&ucpo=12467&gclid=CKyGjI23hdECFQ-4wAodtZ4P1g

And

http://www.jensonusa.com/JensonUSA-Shimano-Style-BB-Tool

However ...
this is the Best for installing the Newer Style Outer Bearing Shimano BB's ... http://www.jensonusa.com/JensonUSA-29BB-Bottom-Bracket-Wrench

 

[Recumbent Bicycle Source]

The reason for dumping the Triple is to clean up the chainline a bit (When I hit bumps the chain skips off to the lower chainring, and with a really long chain it's hard to adjust a Triple to work properly). The innermost 30 tooth I never use with the motor on the bike so there is no reason to have it at all. And with a Single I could eliminate the front Derailleur completely, but that means a chain ring designed to grip the chain or some kind of chain guard to keep the chain from coming completely off. It's mostly an issue of my bicycle design. Any normal diamond frame wouldn't have these issues. The 10 an 11 speed cranks are not compatible with my 9 spd gearing on the rear. So I thank you for your ideas and I think I'm about half way there with some of them. Thank you for the Jenson/Merlin links.

 

[ScooterMan101]

The bike shops, and others say that ... You can use a more modern 2 chainring 10 speed crankset , with a 9 speed chain,
and
Since you are keeping the 9 speed chain, you will also still be using the 9 speed cassette and 9 speed derailleur at the rear.

You are perhaps confusing the fact that you can , not use a 10 speed chain with 9 speed gears.

So from what I have been told,

9 speed chain used with a 10 speed modern crankset/chainrings is ... OK

10 speed chain with older 9 speed gears is ... Not Ok


BTW if you really wanted to , you could use the modern Shimano Hollow Tec II crankset, take off the chainrings and buy 9 speed chainrings ( 2 or even 1 if you like) , and sell the 10 speed chainrings to someone on craigslist.
Since it is the usual 110 or 130 BCD the 9 speed chainrings will bolt right onto the newer crankset.

 

[amberwolf]

The reason for dumping the Triple is to clean up the chainline a bit (When I hit bumps the chain skips off to the lower chainring, and with a really long chain it's hard to adjust a Triple to work properly).

This is one reason I went with a 3-speed IGH, mounted in the frame, when I added gearshifting to SB Cruiser:
https://endless-sphere.com/forums/viewtopic.php?f=2&t=67833&start=350#p1227692

Though I presently have a triple on there as well it's mostly for experimentation purposes, and I am likely to remove it and install just one ring (and remove the derailer-tensioner) that suits the gear taht works best for me (probably the lowest possible, since for me I just need to have an emergency backup that lets me pedal really slowly but easily to not hurt my joints more).

I am also considering leaving it on there but making an offset adapter ring to allow me to rotate the Shimano Biopace rings relative to the cranks so that they are effective from the seat postion I am in, vs the crank angle (whihc they are not, presently, since I am seated quite farther back and down from where I would be on a regular bike, these chainrings/cranks can't do their job).

 

[Recumbent Bicycle Source]

ScooterMan101

I had a little time to dig into this this evening. Bottom line is that it will probably work without problems, especially since I don't drop shift the large cassette without downshifting the rear. So no big hops... not supposed to shift that way anyways, but on my bike it's a sure recipe for bouncing the chain off.

Two good reads on the subject. Looks like new chains work fine on old rings (Same interior dimensions), but problems might occur using old chains on new rings. That makes sense to me. This is good news because the Double Cyclo Cross Gearing should work great for me.

http://www.sheldonbrown.com/speeds.html#chainrings

Old Chainrings, New Chains
In practice this "problem" almost never materializes. Many, many cyclists are using 9- and 10-speed chains with older cranksets and having no problems whatever.

New Chainrings, Old Chains
Going the other direction, using wider chains with chainrings intended for narrower chains is not generally a major problem if there's only a one- or two- generation difference. The only problem you might run into is that the chain will be more liable to rub on the inside of the bigger chainrings in the small/small crossover gears, gears you shouldn't be using in any case.

Sheldon has been gone for awhile, but they are keeping the site up nicely.

http://www.velonews.com/2016/01/bikes-and-tech/technical-faq/tech-faq-chain-width-explained-compatibility-queries-answered_392163

Again thanks to all.

 

[Recumbent Bicycle Source]

Amberwolf... that set up is a bit beyond my DIY Skill set. I'm more of a parts replacer

 

[amberwolf]

Ah, well, it did take some figuring out. But I had never done something like it until I built it, and only went thru a few mistakes and broken-off bits before I got it figured out, so it can't be all *that* hard.


I'm pretty much a successive-approximation guy, eventually getting things close enough to do the job I need.

 

[Chalo]

When you settle on the chainring you like (and forget that gimmicky narrow-wide foolishness), you can use an old front derailleur to retain the chain. Use the adjuster screws to lock the front derailleur in the right position over the ring, and slide it down over the chain as low as you can without the chain rubbing the top of the cage when in the large rear sprocket.

I just did this in remodeling my rain bike (a pedal-only bike with fenders and drum brakes). I replaced the 48-38t double rings with a 36t single ring, and replaced the 14-34t freewheel with an 11-34t freewheel. I kept the existing front derailleur, but disconnected the cable and locked it in position.

Keep in mind that the best chainline in most cases is that which aligns the center of the chainring(s) with the center of the stack of sprockets. If you use one end of the cassette a whole lot more than the other, you might want to bias the chainline to that side.

If you're happy with your old cranks except for the rings (I'm not a big fan of Octalink, but until it fails it's not a problem), keep them and simply get a new chainring and some single chainring bolts.

It's a good idea to use the largest chainring you are satisfied with, so you don't spent too much time in the top gear where wear and tear is accelerated.

 

[Recumbent Bicycle Source]

Chalo

That's an option I considered, but the existing Crankset each ring is tied to the other so I'm not sure I could find the right combination of ring and screws to make it work. By the time I did the cost wouldn't make sense so I might as well just by a new crank and get up to speed, this crank/bottom bracket is 12 years old now anyways so replacing it probably wouldn't hurt.