Eccentric bb vs. sliding dropouts
 

I'm trying to decide between two Alfine-11 bikes for my new commuter. One has an eccentric bb and the other uses sliding vertical dropouts to tension the chain.

I've only ridden derailer-equipped bikes before so chain-tensioning is an unknown country to me. I'd appreciate any insight and opinion on the differences between these two approaches and the pros and cons of each.

For example: how tricky is it to adjust the tension with sliding dropouts? What are the downsides to an ebb?

Links to bikes in question:

Brodie Once
MEC Chance

Thanks to all who respond!

i have an alfine 8 hybrid that utilizes an EBB for chain tension. it seems to work well enough, but i have no idea how to make adjustments to it, and the manual that came with the bike didn't offer any hints. it seems to me that sliding rear drops would be an easier system to make adjustments to, but there may be downsides to them that i haven't considered.

I've got sliding dropouts on my IGH bike, and tensioning them is simple. And once they're set, wheel removal works the same as with vertical dropouts: super easy.

Either system works great, though it is worth looking into the specific EBB that Brodie uses (I couldn't tell from a quick glance at their site). EBB's have a reputation for being creaky, but this (from what I've gathered) is a generalization that my apply depending on the style and brand of EBB shell/insert.

I've used sliders and have just ordered a frame with an EBB, so it will be trial by fire for me with EBB.

The primary advantage of the EBB is that the wheel centering will be a given, as will the chain stay length. The downsides (as I understand them) are: slight variability in saddle/crank setback, potential for noise (may be N/A given manufacturer/style).

Sliders strike me as the inverse of EBB, in that the advantages and disadvantages sort of swap - the downsides of the EBB are the advantages of the sliders, etc.

My experience with sliders was good overall - no real issues. The only "dance" was re-centering the wheel while ensuring optimal tension, but no big deal.

My understanding is that both systems have been through the paces enough that modern offerings will be fine either way.
With that in mind, I'd be less inclined to focus on those aspects than on frame geometry and bike features.

My wife has the 8-speed variation of the Chance - The Hold Steady - and it is an impressive bike for the money IMO. I haven't had any one-on-one time with Brodie, but the ones I have seen in shops seem really nice.
Frankly, you can't go wrong either way.

Funny this should come up. I ordered one of the cheap frames that Nashbar had on sale. The one I ordered has an EBB but didn't come with the insert which I will have to find on my own. In doing my research I ran across a lot of opinions regarding EBBs vs sliding dropouts.

Canyoneagle sort of summed it up. Some EBB systems (and there are few) have a reputation for creaks. Some have been known to slip when ridden hard. Others seem to be more or less problem free when installed correctly. Some systems depend on the EBB shell being properly prepared (and perfectly round).

It also sounds like some of the issues with EBBs are aggravated by frequent adjustment, - people who race on single speeds and are constantly changing cogs.

Generally sliding dropouts had less issues overall but you do have to worry about getting the wheel straight and a lot of people just didn't like the way they looked. In that type of system it's possible you may have to adjust your fenders if you change cogs. If you're using Canti or V-brakes, those would need to be readjusted too. On the other hand, the large EBB shell could complicate fender installation too.

One advantage stated for EBBs other than aesthetics was the ability to raise or lower the BB as well as move it fore and aft.

EBBs might use pinch bolts, set screws, or wedges. Pinch bolt systems appeared to be more consistently reliable. The ones using set screws may or may not be but the Phil Wood inserts got favorable reviews. The wedge bolt systems also seemed to depend a lot on the quality of the insert being used.

Note: None of the above is based on personal experience, just based on research on what EBB insert I should get.

I've used a set screw type EBB in the past and would suggest avoiding that method of securing the EBB. One thing I noticed wasn't mentioned in the above posts was fender/wheel alignment. If using sliding dropouts and fenders consider that the relationship between wheel and fender could change slightly.

One thing that has puzzled me for a long time is why there is so much reluctance to use a chain tensioner with an IGH. That seems like the best way to go to me. Is it the look of it, or is there another disadvantage to a chain tensioner?

Paul

On the mtbr.com SS forum, the ebb has a terrible record for squeaking. It seems like no matter what brand, noise is a given, just a matter for time. I run horizontal dropouts and sliders on a variety of IGH bikes, no issues.

I have a Specialized Centrum single speed as my winter bike with sliding drop outs and I cannot keep them from sliding forward no matter how tight I torque down on the 4 allen bolts. I have never heard of others having this problem so it may be an anomaly to my particular bike. It is annoying having to re-tension the chain every two days. I would like to try the EBB on my next bike.

Thanks for all the high-quality replies.

So you only have to set/adjust them when you want to re-tension the chain (or use a different cog or do some other mod)? Not every time you remove the wheel?

Very useful, thanks. I'm considering the Hold Steady, too. Just feel that an extra $250 for the 11 is a decent price since I'm used to close spacing. But with the Chance out of stock until at least November, I might just say f-it and get a Hold Steady this week.

Not sure I understand this bit. Fenders mount on the seatstay and rear triangle, not the BB, don't they?

Why would you want to raise or lower the BB? Just for personal preference re: fit, clearance etc?

Thanks for a great reply.

This is a good point - but it shouldn't change by more than the chain stretches, should it? I.e. not by very much, a few mm at most?

I also wondered about this.

One of the reasons I wanted an IGH is to minimize the affects of winter grime and grit on the drivetrain. The jockey wheels on my derailleurs were grit magnets. I spent a lot of time each spring cleaning those up. If you're using a chain tensioner that is still a chore that will have to be dealt with.

A lot of the single pulley tensioners work by pulling the chain away from the rear sprocket which isn't good. The betters ones like the Surly Singleator I have on my current bike will work in either a push up or pull down mode. However, having it in "Push Up" mode means I have to loosen it to get the rear wheel off. Not a big deal but getting the rear wheel off with an IGH is already more of a chore.

Then there is the aesthetics. I don't think the Singleator looks terrible but the bike would look better IMO without it.

It sounds though like some people have really struggled with their EBBs and I will say that the Surly Singleator does it's job pretty well. I've probably got a few hundred miles on the bike so far and I haven't had to mess with it and I've never had the chain fall off.

The large EBB shells sometimes leave less room for the fender at the chain stay bridge. I don't know how often this is really happens, I just saw it mentioned.

The issue with brake/fender alignment with sliding dropouts isn't so much a problem because of chain stretch. It comes into play if you ever switch cog or chainring sizes. The wheel may end up moving forward or back to get the proper chain tension. With an EBB, it's the bottom bracket that moves.

If you never change cogs or chain rings then it doesn't matter.

Rear facing drop outs or track ends are the best. I love them. So simple and easy to tension the chain. And together with some chain tugs it's a bombproof set up. I never had any problems with mine...Eccentric bottom brackets are just a problem waiting to happen, those bolts will eventually strip or become seized, No thank you !!..I have no experience with sliding drop outs, but I just don't trust them...I just love the simplicity and reliability of track ends or horizontal drop outs.

I don't like the sliding dropouts that came with my IGH bike. I would like to try a pinch-bolt style of EBB just for the sake of comparison.

I would personally prefer sliding dropouts to an eccentric bottom bracket given the sliding dropouts have some sort of provision similar to chain tugs that ease chain tensioning and prevent unwanted slippage. Otherwise, both options are effective and serve their purpose well. Good luck!

Cheers
lverhagen

As others stated, in both camps, the particular design matters, but many more EBBs seem to have problems than sliding dropouts. When researching my last commuter (Kona Dr. Fine), I talked to a few bike designers and a lot of shop mechanics and all, even those who had no choice but to sell EBB bikes because of the brands they carried, advised me to go sliding dropouts. Two added benefits of sliding dropouts are less weight (in my research of different models seemed EBB was a 1 lbs. weight penalty, but it's hard to judge when holding one brand up against another), and in many cases, the possibility of changing the bike over to derailleured by swapping the dropout. I had a bike with track dropouts before, and the sliding dropouts are so much better. The only EBB I would consider would be like the system Niner uses, but that comes at a significant cost.

My Dahon Cadenza uses an EBB with pinch bolts. It is pretty easy to adjust and does not move on its own. There is an occasional creak and I wouldn't recommend them for big powerful rider but for me this one works fine. There is no interference with the rear fender at all. It does add a bit of weight. I'm not sure how easy a BB cartridge change will be with the rotatable block. Does anyone make a rotating EBB block with built-in bearing holder, this seems a much more sensible idea, removing a lot of bits and weight. Also are there any standard sizes for the rotating EBB blocks?
Moving the BB up and down does affect pedal clearance at the ground and centre of gravity. You can use that to your advantage if you want to alter the characteristics of the bike, but it is a very minor tweak.
On my next IHG bike I would probably want a split rear triangle so I have the option of a belt drive. I think these are easier to rig with a sliding dropout.

Some IHG bikes use chain tensioners but they collect dirt and are an unnecessary mechanical bit. Its OK for a retrofit of an existing bike but to design one in a new bike is just lazy or ignorant.

While the Hold Steady is a great bike, I'd say it is worth waiting for the 11. The even spacing is worth the extra $, and the oil bath is much easier to maintain.


On the fender / BB issue, most bikes will have a chainstay bridge where the fender mounts, so the BB will not matter at all.

can track dropouts be used in tandem with an IGH? with disc brakes?




is this really true? has no one on this forum escaped EBB squeaking after several years of riding?

i'm kinda nervous now that i bought an EBB bike. mine is only 3 months old, no squeaking........... YET.

Some rear "track ends" seem to be better designed than others for discs, but generally, yes, they are compatible.

Because the "track ends" allow horizontal adjustment, they should work just fine with IGH's.

The EBB bike I have has a removable derailleur hanger so you can run it as a traditional geared bike if you want. The weight of the EBB insert, cam, or whatever you want to call it is 1/3 to 1/2 lb. depending on model. Bushnell sells a high end model that's about 140 grams.

There are lots of EBB vs. Sliding dropout threads on the interwebs. While squeaking seems to be a common complaint, I would hardly call it universal. There are plenty of EBB owners who claimed to have never had a problem.

thanks for clearing that up. one super annoying aspect of the interwebs is the speed at which opinions become "facts".

disk brakes need some kind of accommodation to work with track dropouts. Any kind of horizontal drops should work with an IGH. As far as the question in the OP, sliding or otherwise adjustable dropouts seem to be winning handily over ebb's, my interpretation is that it's not just a momentary fad.

Yes they can. My Surly has track ends and I am running disc brakes. However I do have to loosen the caliper bolts when removing the rear wheel. It's very easy , not a big deal for me.