Chain Tension and Single-Speed Setups

[Jukka4130]

I am planning two single-speed builds (a dirt jumper and a single-speed MTB) which makes this topic timely. So far, I haven’t seen it discussed thoroughly, so I thought a dedicated thread would be warranted.

I’ve listed the options that I am aware of below with some notes and pros & cons if known. If I am missing something, any input is highly appreciated. Currently, my wish would be to use a thru-axle hub in the builds, 142mm or 148mm Boost, but it’s not set in stone yet.

Horizontal dropouts
This is by far the most common one. It can work rather well but necessitates the use of 135mm bolt-on or threaded axle hub. When it comes to manufacturing, the ISO tab can cause some complications because of the varied axle position. I can see a situation in which the rear portion of the brake caliper would prevent the chain tension adjustment by hitting the rotor. Has anyone run into this issue?

BFS “Fish head” dropouts go around this problem with slotted ISO tabs. However, the CS and SS tube diameters

Slider dropouts
PMW slider dropouts are a tried and trusted product. I’ve had some slipping issues on one set, but I can live with them. A big plus is that the disc brake mount is handled in an exceptionally nice manner with this option. However, on the dirt jumper, I would like to go with something a bit simpler or even minimalistic in style.

Eccentric BB
It seems that eccentric BB’s aren’t used much nowadays. Some early models apparently had their share of issues: slipping, creaking etc. Bushnell bottom bracket seems to be one of the better ones. However, it does come with its own requirements when it comes to the BB shell.

One interesting option is the Trickstuff Exzentriker. A big plus is that it fits the standard BSA bottom bracket but is only compatible with Shimano 24mm HT2 cranks. Not a big downside, though. The reliability of the system is a question mark.

Eccentric dropouts
Related to EBB’s, eccentric fittings can be made on the dropout end of the frame. Starling Cycles has done this with their fantastic-looking Beady Little Eye frame. This solution requires some parts manufactured solely for this purpose. In addition to that, Some concerns do exists if the system can hold the rear axle in place and the chain tension constant if the axle is secured in place with one (or two) pinch bolts only.

Chain tensioner – Meybo-style
It’s simple, but it works. BMX race bike company Meybo has created a simple chain tensioner which consists of an adjustable arm and a simple slider part. One positive side is that it can be accommodated to any dropout somewhat easily with any axle standard, and the overall simplicity.

The downsides are the looks (at least to some) and that it’s prone to external damage. However, I’ve yet to see one damaged on a Meybo bike.

Moonmen – TI Tension System
When learning about this topic, I stumbled onto Ti Tension System used by Moonmen. Overall, I applaud the engineering and manufacturing that has gone into it! I thought it’s worth bringing up, if not done already.

As said previously, all input is highly appreciated.

[Pi_bikes]

I made some similar to the BFS fish head for 135mm. The iso tab is easy with 135mm because it is on the same plane as the dropout face, just get something lasercut with the iso tab built in. Things get more complicated if you wanted to do thru axle hubs as the iso face is offset to the drop out face, Learned that one the hard way and had to cut it off and re-attach!

I do wonder if a steel thru axle with a nut at the other end could work with a slotted dropout. I guess the hub ends may be an issue as they are usually aluminium and may get smooshed.

I had a Stooge mk4 a while back with an eccentric BB, it was trouble free. I think I may have saved myself potential issues with it as I pulled it apart and greased it before assembling the bike. it was an aluminium centre in a steel shell and it could get galvanic corrosion issues with a lot of weather exposure I imagine.

[bushtrucker]

One system you’ve forgotten is Rocker style dropouts. They’re a nice solution for bikes with relatively open CS/SS angle. Maybe not as suitable for a DJ or SSMTB but still a good one to have on the list.

Of the systems listed I’ve ridden a good few thousand kilometres on Horizontal Dropouts (Track Ends) with a 135mm bolt on hub, Paragon Sliders with a boost thru axle hub and Taiwanese Rockers with a thru axle hub. I’ve never used a EBB and to be honest I’m not that interested. I have enough trouble with creaking bottom brakets as it is haha.

I think the Paragon sliders are my favourite for trail use. So simple to setup and take your wheel in/out which i find I do a lot more of on a MTB. The only issue I had was some slipping/creaking but proper bolts and a good clean and degrease of the inserts fixed that. One thing to note is that sliders aren’t ideal for rack mounts but that doesn’t seem to be a priority for you.So yeah I’d put them on the MTB.

On the DJ rig I think you should keep it simple with something like the BFS “Fish head” dropouts or maybe get creative and make something yourself like @Pi_bikes suggested. If you want to go slightly fancier but still use a bolt on but then Bear Frame Supplies (also BFS ) make a nice horizontal dropout with an inbuilt adjuster. Kinda reminiscent of the track ends PAUL used to make.

Oh and one last alternative tensioning hack that might be a bit cleaner than a deraillier mounted tensioner is to use an ISCG mounted chain guide. Could also be pretty neat on a DJ rig if you ask me.

[gschwell]

As a single speed rider for the last 15 years, I’ve tried the standard options (Paragon sliders (and many knockoffs), Salsa Alternators, eccentric, horizontal). My favorite without a doubt is horizontal fork end dropouts. I love the simplicity and reliability, no creaks, no slips, no small bolts to over-tighten. For my frames I designed my own and used send-cut-send to make them with 1/4" stainless. The brake adjustment is simple and easy.

The downside is committing to the 135mm bolt-on hub standard, even thought it makes for a narrower rear end and strong no-dish wheel. I think the only new hub options are Hope and Onyx (I have an Onyx that I love). It’s your classic bike industry story of getting railroaded into a new standard.

I think a retrofit bolt-on axle for a 148mm hub is totally feasible. Possibly making the dropout spacing 150 to allow 1mm knurled steel washers between the hub end caps and frame.

[Brad]

I am building a fixed gear mountain bike currently. I had dropouts cut with 12mm slots to use the Surly Gnot Boost system.

Laser cutting is great because you can make it match CS/SS angles perfectly.

The problem is that Surly offsets the brake tab approximately 3 MM inboard because how the axle caps on thru axle are inboard of the brake tab. I found using a 5MM front boost rotor adapter put the caliper within 1.5 MM of proper location. Caliper bolts give much more adjustment than 1.5 MM so it works.

I really want a 2mm deep X 20 slot machined into the dropout for the caps to sit in but I don’t have a mill. This would eliminate the need for disk adapters.

Surlys QR adapters add 5mm to each side and make the OD 12m for QR applications.

One laser cutting lesson learned is the cut gets wider as it gets deeper. This makes the slot wedge shaped. I made mine 12.1 mm and they are looser than I want due to the wedge shape cut. I would make them 11.9 and file to fit if I was doing it again.

Also, make the SS tab of the brake tab longer than you need because it will need bent inboard. I made my first dropouts with it matching SS perfect and had a pretty big gap to fill after it was bent in.

[mark_pmw]

Of course I’ll suggest PMW Sliding Dropouts!

For a DJ bike, you might look at our Dedicated Sliding Dropouts. Dedicated 12 mm Flat Sliding Dropout, No Eyelets: Choose Material/Belt Drive Option

The tabs may be a bit long, but the hub is captured within the 17/4 frame component. Expensive and bomb-proof. Options for ISO, Post or Flat Mount Brake.

This one is nice in its simplicity, but you’ll still need to figure out the brake mount. I don’t know who did this, so I can’t credit them. If anyone knows, give them a shout out.

[sunshine.fab]

If memory serves that’s a Transition Bank

[mark_pmw]

Your right, I just looked at the name on the photo!

[Spencermon]

My only input is from the hardtail Single Speed I recently built for myself. I used These modular dropouts from Framebuilder Supply. They are simple to build with and if I ever want to use gears, I can buy the thru axle dropouts separately. They are also a little bit less expensive than other options, so that was nice. Also, I hate tab style dropouts (I suck at brazing them) so the attachment style on these was a plus.

I also just designed the IS brake tab and had it laser cut at sendcutsend. If you are building a bike with a lower CS/SS angle, and you optimize the IS brake mount location, you shouldn’t have any issue with the caliper hitting the rotor. I don’t have that issue at all. though that also might be because the 180 post mount adapter does tilt the caliper slightly forward.

[Jukka4130]

Thank you for the inputs!

@bushtrucker
I feel almost like punching myself for not thinking about the ISCG05 / chainguide combination! However, one shortcoming is that it can’t most likely be fitted for small gearing, like 26T sprocket or so – at least without some modification or custom-made chainguide. I am planning to use old-school Profile Racing 3-pc chromoly cranks on the dirt jumper and a small sprocket would be a nice pair. A 32T isn’t out of the question, though.

@mark_pmw
Thanks for chiming in! Those do seem like a splendid option that have gone under the radar thus far.

@Brad
Surly certainly does things their own way. Their dropout system was new to me. Going to dive a bit deeper into what’s going on over there.

@Spencermon
One very highly potential option to add! Thanks.

[Matt]

Is it possible to find a dropout similar to the Surly Ogre?

In terms of SS, I have tried several but the only one that I really loved is the horizontal dropout in my KM and later on my Krampus, easy to setup and forget.

Sliders (of which I still own some variants - never had a PWM one) always slip unless you over-tighten them, I have a pair of PMW rockers waiting in the drawer for the right project, always loved the look of them.

[JMY]

I’ve been liking the PMW sliders for their versatility. I’ve never had any issues with slipping.
Aesthetically not everyone will like them and they may not be the best choice for a dirt jumper.
The PMW Rockers are nice too if the frame design can accommodate them. A downside is that they don’t have a tensioner which means slippage, especially if used on a dirt jumper, may become an issue. And that when used with a derailleur, the fore/aft swing will affect how you need to adjust the B-tension. So again, slippage may throw out your shifting experience. Obviously, that will not be a problem for your builds.

I did have an eccentric BB (split BB shell) on my first SS MTB some years ago (Specialized Crave/Carve) and to my surprise, it actually worked flawlessly despite widespread talk about creaking and slipping using that system.

Some years ago I saw that Sean Handerhan of Handerhan Cycles posted up some really neat hooded sliding dropouts for thru-axle on his IG feed - a design that pretty much nailed what had been floating around in my head for a couple of years before that. I never saw the build they went onto though and I don’t have time to scroll through IG photos. I may still draw up my own version of this concept to try it out on a future build.
This concept still leaves the problem with disc brake attachment unresolved though.

[JoeNation]

What are the chances of getting the PMW 12mm sliders to work with a carbon frame? Option 1, bond/wrap the dropouts to the tubes - is there enough tab length for a solid joint? Option 2, take a mould and make the dropouts in forged carbon - would this hold up to the clamping forces and friction from the hardware? Probably pie in the sky…

[JasonP]

FWIW I’ve had a good experience with the wheels mfg PF30 EBB on my thru axle gravel fixie

Eccentric BB for PF30 & 24mm (Shimano) Cranks - Black

Downsides: you really need to buy the squid bikes oner adjustment tool, and the two halves do not pivot together/stay nicely in alignment. Takes some fiddling when adjusting chain tension.
(squid bikes makes the same or similar, several bearing options for different crank spindles. Niner also makes one for 24mm Shimano and GXP cranks)

Then there’s this. Massive range of adjustment for an EBB and it requires a non-standard? BB shell

BioCentric II

My ROS9+ that’s seen ~8 years of heavy all weather Colorado use and countless thousands of trail miles has been nearly creak free. Pull the aluminum insert, clean and grease yearly. Also adjustment is very easy, takes two wrenches and <1min. Handy running dingle speed.

[stevenshand]

I second the PF30 EBB. I’ve built literally hundreds of frames using this solution for our Rohloff bike we did at Shand Cycles. However, some of the early EBBs that were available weren’t great. We worked with Paul at Rideworks here in the UK and he manufactures the best PF30 EBB there is. The biggest issue we found is that the cups on the other versions would get out of phase, especially when tensioning, leading to premature bearing wear. His cups are kept in phase with beefy sleeves. Bearing and seals are also great.

[JoeNation]

I just wish there was an easy way to make that work with BBright. I’m sure a crank with a longer spindle would do the job, but can I figure out what length or find any road-ish cranks with long spindles?

[JMY]

How about over-moulding with a steel or aluminium core?

[RichardEvans]

So this thread is right up my street as I only ride a single speed these days and seem to have spent most of last year making them. Although most are gravel/all-road bikes I am always thinking of ways of making life simpler and the dropouts have always been easy to make and fit but I know a single piece would be easier.

I’m running a 135mm axle which used 10mm bolts to hold it in place. No matter what I have thrown at it so far I haven’t needed a tensioner and it has never come loose.

Anyway here is my bike and I’ll try and take a better image of the dropout later.

[RichardEvans]

Forgive the state of the bike as it does get abused a lot.

The brake mount starts off as one piece but I chop and file the middle out to allow for the shape of the brake. I’ve tried a few different ones now and so far haven’t had any issues.

Currently I am redesigning the dropout so the whole thing is one piece and will allow me to speed up the process of fabrication.

[Jukka4130]

Thanks for sharing! That’s a nice dropout design. I assume the hub, and more specifically axle assembly used plays a big role in how the wheel stays in place. When using a frame with 135mm spacing, I use the Onyx 135/10mm Bolt-on hubs whenever possible. The 10mm titanium bolts have plenty of thread engagement and allow as stout an interface as possible with that axle/spacing standard.

A hub set with the specs in question as an example: Instagram.com/onyxhubseurope.com