Sep 4, 2008
When your LBS isn’t good enough any more
Is it time to move? Or to build your own parts? That’s what I did!
Frequently any more, the bike shop just doesn’t have what I want. They can always order stuff for me, which is nice, but I want to pick stuff up and play with it and look at it. And I just can’t do that on the Internet. At least not until I unveil the somewhat-illegal form of virtual reality that I’ve been working on for the last 13 years.
So I needed a chain tensioner for my single-speed (converted 10-speed Raleigh). But they really don’t make tensioners designed for front-facing horizontal dropouts… they’re pretty much only for track fork ends or BMX.
I went to the hardware store, and picked up two eye bolts and a pre-drilled bracket with some holes in which the bolts would fit.
I took my wheel off the bike. I took off the 5mm spacer between the wheel and the dropout. I replaced that with the first eye bolt.
I put the wheel back on, and put the other eye bolt on the other side of the dropout. I put the axle nut back on.
I took of the nuts from the eye bolts, and put the bracket in place. I tightened the nuts down, and put the axle nut on snug. Voila!
The finished product was pretty successful on my fast commute this morning (in which I did not use my saddle). I was mashing pretty hard on those pedals, and all I felt was beautiful, strong, unforgiving chain tension. Wahoo!
Cool post! I don’t really understand the need for a tensioner on a single speed though.. why not take a link or two out of the chain?
The chain is the right length, but I jam on those pedals pretty hard when I take off or sprint. So even if I have 65 ft-lbs of torque on those axle nuts, the wheel still slides forward in the dropouts. So my wheel could pop out of the dropouts totally, or my chain could hop off my gears. And I really love, love to have high chain tension – it provides a significantly more responsive ride.
Good solution. My brother burned off the dropouts on a specialized stumpy and brazed on the forward facing dropouts. He gave the bike to a friend, but it had always slipped…
-M
[...] hadn’t realized, but I’m all about the bike hacks: http://www.karlfundenberger.com/blog/?p=82 (built a chain [...]
[...] Hey, thanks for stopping by! If you’re new here, you may want to subscribe to the RSS feed. You can also subscribe to BikeHacks by email. Thanks for visiting!Karl sent along a hack a while back for a plexiglass fender and now he has another one to pass along. This one is targeted at you single-speeders out there. From his site (full post here): [...]
Slipping drop outs are not common. For example, the top professionals of the 1980’s used quick releases on forward facing drop outs and they did not suffer from slipping rear wheels (even on the steepest climbs on the grand tours).
Usually the reason for slipping rear wheel is that the drop outs are not parallel. If drop outs are not parallel, then the track nuts do not get full grip from the drop out and will slip.
So check that the drop outs are parallel with each other and parallel with the rear wheel.
Thanks for the tip! I’ll have to check that they’re straight.
A few comments, though:
On geared bikes, derailleurs do the chain tensioning. If you ever jam on the pedals hard and suddenly, your derailleur might flop a bit, but the chain as it passes from the derailleur around the cassette should be properly tensioned. And never on a geared freehweel do you have forces coming from the top of the chainweel backward to the cassette (as opposed to fixed-gear). The chain is only ever taught on the top (from cassette to chainwheel) when pedaling, and never taught on the bottom (chainweel to derailleur).
On a single speed, your chain tension is constant through the whole chain. Because the chain is a determined length, Any tension or stretch is communicated through the whole chain, without the alleviation of tension that a derailleur provides.
This is why professional BMX bicycles and track racing bicycles come equipped from the factory with chain tensioners or “chain tugs.” Chain tension is significantly higher on a single-speed.
And finally, 80s 10-speed frames tend to ghost-shift when climbing steep hills, due to frame flex. This problem solved by single-speed!
Ok, then this must be a BMX specific thing. On most other single speed bikes having the chain so tight that there is no slack when pedaling is not a good idea because it consumes chains, cogs and chain wheels very fast.
I do argue that even on single speeds chain tension is not constant around the whole chain. Common recommendation is that when one pulls the chain up and down in the middle between cog and chain wheel, there should be about an inch of play. This means that when pedaling the bottom of the chain really is slack.
I do ride single speeds and fixed gears and I have a visible amount of slack on the chain. It is not a problem. Overtightened chain makes the chain stretch fast and a stretched chain eats the gears. The only place where tight chain is needed is where there must be an instant reaction from backpedaling (that would be fixed gear trick riding and fixed gear trial).
I argue that fixed gear commuting is not the kind of riding where instant reaction from backpedaling is an absolutely mandatory feature.
[...] Here was my first attempt. I used two eye-bolts, a bracket, and two nuts on the first one. But that involved a lot of work any time I needed to remove the rear wheel. And the two eye-bolts took up lots of space on the axle. So, why not go with just one? [...]