Custom Rohloff Rando frame - eccentric BB or sliding dropouts?

[Daniel Jackson]

I'm having a dirt road randonneur custom frame designed around a rohloff drivetrain and am debating between specing sliding/rockered dropouts or an eccentric bottom bracket. Any opinions here about the pros and cons or efficacy of either setup for such a use?

Thanks for your help folks.

Daniel

[Bill]

If you plan on going with belt drive sliding dropouts might offer better precision in setting belt tension. That's not as critical with chain drive. Aside from that I don't see any other advantages either way.

[Matthew J]

I did not like the Paragon sliding drop outs on a custom I had made a few years back.  They were wide and oddly proportioned enough that I had to make compromises with rack and fender set up.

Never had an EBB bike, but recall Mike DeSalvo of DeSalvo customs saying that EBBs can collect grime quickly.

Another option which you do not mention - one I use on my Winter custom designed to for either SS or 1x - is to use extra long horizontal drop outs such as Campy 1010s.  

[Jeff Bertolet]

If you are going to use fenders, that would help keep grime off the bottom bracket.

Are you using disc brakes? If so, I would definitely use the eccentric BB. My favorite EBB design is the split shell that uses pinch bolts.

I haven't used sliding dropouts on my own bike, only an EBB. But having worked on other people's bikes, I find the EBB much easier to work on in terms of installing the wheel, adjusting chain/belt tension and adjusting the disc brakes. The worst design I have seen yet (though not technically a sliding dropout) is the Surly Troll (pic), what a f@#$%ing pain to adjust the wheel/brakes.

[Bill M.]

That seems backwards to me (not that I own either one).  With sliders a disc brake moves with the axle, which should be no problem.  An EBB would allow the rear wheel to stay put so that rim brakes wouldn't have to be readjusted if the wheel is moved.  

Bill

Stockton, CA

[Jeff Bertolet]

Sorry, my reply was confusing. There is no reason to use sliding dropouts unless you are using disc brakes.

I prefer the EBB as I find good EBBs easier to adjust than sliding dropouts. The wedge and set screw EBBs are indeed a pain to use compared to the pinch bolt (like a seat collar) design.

As mentioned in the ibob replies, sliding dropouts also can make fender and rack mounting difficult, while EBBs affect saddle height and seat tube angle.

If these are your options I have to assume you will be using a belt drive. It may be easier to make a sliding dropout split for belt installation. If you are using a chain, I would consider just using a chain tensioner instead of sliding dropouts or am EBB. It might not look as elegant but it doesn't have any of the pitfalls of the other solutions and you can run a derailleur if you want to.

[Matthew J]

> As mentioned in the ibob replies, sliding dropouts also can make fender and rack mounting difficult, while EBBs affect saddle height and seat tube angle.

Definitely my experience.  

[Eric Keller]

seems like the general consensus among framebuilders is that ebb's are
a lot of trouble. Maybe sliders mean you have to give up an elegant
fender line, but they are easy to convert to a derailleur if desired.

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[Mark Bulgier]

Eric Keller wrote:

> seems like the general consensus among framebuilders is that ebb's are
> a lot of trouble. 

I am one framebuilder who would not agree with that.  I built hundreds of frames with EBBS and can't recall a single one that had any technical difficulties.  I always used the slotted shell with two pinchbolts design.  The inert turns easily and locks down completely without squirm or creaking.

I love the cleverness of the Bushnell design (and Dennis Bushnell is great guy as well as a mechanical genius), but I think I would stick with the slotted pinchbolts myself, I love the simplicity of it.

Other methods such as grub screws (ugh) or the old Cannondale wedge design are guaranteed to cause problems, avoid them.

Mark Bulgier
Seattle
 

[Po-Wen S.]

Sounds like an great bike! Interesting discussion esp. as I'm considering something similar as well. Some of my still-evolving thoughts:

1. Sliding dropouts should allow the rear wheel to drop out (downwards) vertically... so wheel removal shouldn't affect racks or fenders assuming these are attached to points fixed to the frame, not the moving dropouts.

2. EBB won't impact rear wheel fender line. But I suppose with slider dropouts one could simply add some spacers to the fender attachment at the chainstay (when the dropout slides further rearward / further away); ditto a slotted hanger at the seatstay bridge to enable sliding (horizontal) adjustment so the top of the fender's "arc" can be adjusted to be always above the top of the wheel? You and your builder should decide if the fender line will be optimized for the wheel at the middle of the sliding dropout range (Paragon slider dropouts have 20mm range), or for short/long end of this range.

3. And keep in mind adequate clearance for your desired max tire size (with and without fenders) vis-a-vis the sliding dropouts at the short end of its range (closest to the chainstay).

4. As someone else pointed out the disc brakes travel with the sliding dropouts = perfect alignment with wheel. Rim brakes will need to be adjusted every time the sliding dropouts change position back and forth. I think this won't be a dealbreaker (functionally), there's a Steve Potts rohloff sliding dropouts cx frame with cantilever brakes (on Black Mountain Cycles blog), so I am inclined to think this issues has been vetted...

5. I thought (judging by appearance) that rocker dropouts would be structurally better (since sliders seem to cantilever the whole rear wheel behind the rear triangle)... but here's a thread that says rockers are a PITA to tension chains especially belt drives.

6. I don't think sliding dropouts will support belt drives (nowhere to split for belt insertion), at least the Paragon sliding dropouts anyway. Some other sliding dropouts (like the Tange ones on the v1 Soma Wolverine) do split. 

7. If you are going to put in a belt drive, would be good to discuss with builder where to put the split so that changing the belt doesn't require removing racks and fenders.

8. If you put in disc brakes, the rear brake's position will impact the Rohloff's external gear mech (the black L-shaped piece where the shift cables enter/exit the hub), and your brake location preference will affect your choice of dropouts. Sliding dropouts will attach the brake caliper above the hub. If you want to put the caliper within the rear frame triangle then I don't think you can use sliding dropouts (although possible with rockers?)...

Have fun!

[Po-Wen S.]

Oh and one more thing --- if you go with disc brakes, you potentially have the option to switch btwn 650B and 29er/700c wheels. In this case EBB could give you the option to adjust your BB height/drop depending on your wheel size.

[Evan Baird]

I've never used an EBB, but I've heard there's a tendency for the pinch bolt style to creak. Supposedly not as big an issue with the bushnell style, but maybe that's a non issue If you aren't out of the saddle much. I personally like the sliders because they allow adjustable tire clearance and interchangable axle options.

[Ray Varella]

I've had a EBB on my tandem for thirty years. 

Creaking has never been an issue but it's machined out of a solid piece of stock. Not sure if a cast unit would behave differently. I'm sure tolerances come into play. 

Aside from an EBB affecting saddle and bottom bracket height, they also chance effective seat tube angle. 

The one in my tandem is about 50mm so there is room for a couple centimeters adjustment fore-aft. 

Ray

On Monday, January 25, 2016, Evan Baird <vanst...@gmail.com> wrote:

I've never used an EBB, but I've heard there's a tendency for the  pinch bolt style to creak. Supposedly not as big an issue with the bushnell style, but maybe that's a non issue If you aren't out of the saddle much. I personally like the sliders because they allow adjustable tire clearance and interchangable axle options.

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Ray Varella

IAABC Parrot Division

Supporting Member

[Eric Keller]

Me too, I've had one on my tandem since 1980 and it has never creaked.
Then again, odds are it is stuck at this point. I was really lazy and
in a hurry, so I brazed some nuts on there and used the well-hated
grub screw method. In this case, the "grub screws" are 1/4-20 bolts.

[Alex Wetmore]

Sliding dropouts are usually designed around a pretty acute chainstay/seatstay angle and don't work as nicely on rando bikes. Here is an example from my own bike:
http://photos.alexwetmore.org/Bicycles/Bicycles/IvyCycles-Rohloff-Custom/i-JcCrZ5W/A

Rocker dropouts have angles that work much better for a rando-style bike (this is from a commuter, but the geometry is pretty typical rando just with a little longer top tube):
https://www.flickr.com/photos/88336152@N00/13780301353/in/datetaken-public/

I like EBBs too:
http://photos.alexwetmore.org/Bicycles/Bicycles/Gifford/i-6Tj37jG/A

Since the EBB is TIG'd or fillet brazed instead of lugged it is easier to use manipulated (bent) chainstays that provide for tons of tire clearance. Since you are building a dirt road tourer that would land in their favor (though you can get lots of tire clearance with a fillet standard BB too). These chainstays have a 7 degree bend which allows them to fit 50mm tires:
http://photos.alexwetmore.org/Bicycles/Framebuilding/Wetmorian11/i-n9nXjQt

The green bike with the rocker dropouts has indented but straight chainstays and maxes out at 38mm tires.

EBBs are different to work with and not all builders will have a jig and tooling that is setup for them.

Rocker and Sliding dropouts do result in a wider chainstay angle, which can cause heel strike issues if you have large feet and a narrow crank.

The EBB option is slightly cheaper in material costs, unless you use the Bushnell eccentric in which case it is about the same. I don't really like the Bushnell.

alex

________________________________________
From: 65...@googlegroups.com <65...@googlegroups.com> on behalf of Daniel Jackson <daniel.se...@gmail.com>
Sent: Sunday, January 24, 2016 12:17 PM
To: 650b
Subject: [650B] Custom Rohloff Rando frame - eccentric BB or sliding dropouts?

I'm having a dirt road randonneur custom frame designed around a rohloff drivetrain and am debating between specing sliding/rockered dropouts or an eccentric bottom bracket. Any opinions here about the pros and cons or efficacy of either setup for such a use?

Thanks for your help folks.

Daniel

[Alex Wetmore]

From: 65...@googlegroups.com <65...@googlegroups.com> on behalf of Po-Wen S. <ispy...@gmail.com>

> Oh and one more thing --- if you go with disc brakes, you potentially have the option to switch 

> btwn 650B and 29er/700c wheels. In this case EBB could give you the option to adjust your BB 

> height/drop depending on your wheel size.

Swapping between two rear wheels is not cost effective on a Rohloff bike.  The hubs are $1200-$2000 depending on source and features.

alex

[Alex Wetmore]

I currently own 3 bikes with EBBs. Two are custom built for the Rohloff. The other is a tandem.

One is pinch bolt (that is on a frame that I built), one is a Bushnell, one is with set screws. The set screw and pinch bolt ones both use Easton eccentric inserts, which are solid parts machined from aluminum and cheap.

The set screws are the most annoying to adjust. Since the insert is aluminum it mars easily, and the set screw tends to find old divots from previous settings and want to pinch there. A hollow point set screw works a little bit better. It creaks a bit.

The pinch bolt one is rock solid, I've never had a problem with it. This shows how it works:
http://photos.alexwetmore.org/Bicycles/Framebuilding/Wetmorian11/i-N54FGC2/A

I copied the design from Alistair Spence, who in turn copied it from Rene Herse. It always adjusts smoothly. If I were doing it again I'd have aimed the pinch bolt screws towards the back instead of towards the front because with this positioning the front tire throws grit into the allen key heads.

The Bushnell is the hardest to adjust (the expanding wedges tend to stick) and the most complex and the most expensive. It creaks a bit for me. It's less work for the builder because they just use the shell as is.

I've also owned a Cannondale eccentric. They are worse than the Bushnell.

alex

________________________________________
From: 65...@googlegroups.com <65...@googlegroups.com> on behalf of Evan Baird <vanst...@gmail.com>
Sent: Monday, January 25, 2016 9:16 AM
To: 650b
Subject: [650B] Re: Custom Rohloff Rando frame - eccentric BB or sliding dropouts?

I've never used an EBB, but I've heard there's a tendency for the pinch bolt style to creak. Supposedly not as big an issue with the bushnell style, but maybe that's a non issue If you aren't out of the saddle much. I personally like the sliders because they allow adjustable tire clearance and interchangable axle options.

[Steve Palincsar]

You've obviously given this a great deal of thought, clearly informed by
experience. If this was your future bike we were discussing, knowing
what you now now, which way would you go?

[Alex Wetmore]

I don't think there is a universal right answer. You can draw your own conclusion from my observations in this email and the two others that I sent today.

I wouldn't use sliders on anything except for maybe a mountain bike (and one of my mountain bikes does have them).

alex

________________________________________
From: 65...@googlegroups.com <65...@googlegroups.com> on behalf of Steve Palincsar <pali...@his.com>
Sent: Monday, January 25, 2016 1:47 PM
To: 65...@googlegroups.com
Subject: Re: [650B] Custom Rohloff Rando frame - eccentric BB or sliding dropouts?

[Mark Bulgier]

Alex Wetmore wrote:

> http://photos.alexwetmore.org/Bicycles/Framebuilding/Wetmorian11/i-N54FGC2/A
> I copied the design from Alistair Spence, who in turn copied it from Rene Herse. 

While I like that "Herse" way of slotting, I think it's mostly a show-off move, not necessary.

I slotted a couple hundred tandems this way, starting in 1979.  Before that I worked at Santana where we slotted them all the way across the shell. (Later, Santana went to a grub-screw system, but I was there at the very beginning and helped make the first batches.)  So I have extensive experience with both types.

In theory, the Herse way should tighten up more easily (less bolt tension required for the same clamping force), since less of the outer shell is being deformed  to close the slot.  But in practice, the simple straight slot tightens up plenty easily and doesn't slip or creak, plus it's way easier to do.

Not saying I like the straight slot more -- I still prefer the Herse style, but mostly because it looks cooler!

On my own tandem, I slotted in from both ends like Alex (and Herse), but then I simply removed that whole center section of outer shell, roughly from the downtube fillet to the bottom tube fillet, because I thought it was just dead weight at that point, not doing anything.  That was sort of a weight-weenie tandem, built with rather light tubing: .8/.5 DT, .7/.4 TT, .6/.3 internal bracing tubes, 0.7 mm plain gauge bottom tube, 0.6 mm chainstays. 7.5 lb frame, in steel for a 61cm / 51 cm frame size, not bad even by today's standards.

I didn't know if it would be strong enough, but I think my experiment has proven successful because that tandem is 25 years old now and we ride it a lot.  Everything from loaded touring including dirt and gravel roads, to stage racing (we won the bunch sprint for 3rd in the criterium stage in the Duet Classic, and got some other top-ten finishes).  It did get one fatigue crack, in the right-rear dropout, a regular Suntour touring vertical that I didn't even thin or lighten at all -- go figure.  To fix, I V-notched the crack on both sides and TIG welded it, shot a little primer on it, and we've been riding it that way for maybe 10 years.

I also found out how easy 0.3 mm Prestige is to dent.  I was careful to make sure the handlebar didn't hit the ultralight internal bracing tube when it swung around, but for the time-trial stage in the Duet classic I lowered the bars and didn't notice that it was in the danger zone, so the next time the bars flipped around, "ding", nice sized dent in the frame.  Luckily those internal bracing tubes are so unimportant, not doing much more than holding another pair of waterbottles, so a dent there will never cause a problem.

Mark Bulgier
Seattle

[Po-Wen S.]

Yes you are right of course (and this is the 650B forum after all). I was getting irresponsible spending someone else's money.

On Monday, January 25, 2016 at 1:16:07 PM UTC-8, Alex Wetmore wrote:

From: 65...@googlegroups.com <65...@googlegroups.com> on behalf of Po-Wen S. <ispy...@gmail.com>

[Po-Wen S.]

Hi Alex could you explain why you think sliders would be fine for a MTB? Earlier you had pointed out that sliders require a rather acute seatstay/chainstay angle, how is this less of an issue for MTB? Thanks.

[Alex Wetmore]

Mountain bikes typically have shorter seat tubes than road bikes (with more heavily sloped top tubes), so the chainstay/seatstay angles are naturally more acute.  This is because mountain bikes have higher bottom brackets (for log clearance) and increased standover.

Compare the last slider picture that I posted with this one and you can easily see it.  20" MTB, 58cm road bike:

http://photos.alexwetmore.org/Bicycles/Bicycles/Kona-Explosif-MTB/i-dq9MNjg/A

The sliding dropouts also tend to put the disk caliper above and behind the seatstay, where rocker dropouts usually located it forward of the seatstay.  That latter location is preferred if you'll be using a rear rack or fenders.  Those are less common on mountain bikes, but are common on rando bikes.

alex

---

From: 65...@googlegroups.com <65...@googlegroups.com> on behalf of Po-Wen S. <ispy...@gmail.com>
Sent: Monday, January 25, 2016 2:54 PM
To: 650b
Cc: pali...@his.com

[Nick Payne]

We have two tandems with slotted shell EBBs, both built by the same custom framebuilder in Perth, and one tandem (a Co-Motion) and one Rohloff-hub Thorn Raven which both use set-screws for the eccentric. After a few years of use and adjustment, the slotted shell EBBs are far easier to adjust to take up chain wear. As has already been remarked, on any sort of fine adjustment, the set-screws tend to find the indentations they have previously made in the aluminium BB eccentric, making the adjustment difficult or impossible.

FWIW, there are now several manufacturers now making eccentic BBs for PF30 and BB30 frames. e.g. http://wheelsmfg.com/bottom-brackets/ebb/ebb-bottom-brackets/eccentric-bottom-bracket-for-bb30-24mm-shimano-cranks-red.html. I haven't used them and have no idea how well they work.

Nick

[Daniel Jackson]

Thank you all for your prompt and well considered responses - very helpful indeed. I'll be sure to share the build this summer when it's all finished!