Converting To Fixed Woes

[Losidan]

Hi,
As I have posted in the fixed forum I have a bike I want to convert from road to fixed...The more I read up though, the more I am getting confused.

If you could give me some advice I would be very appreciative.

1. I believe I can convert to fixed on a vertical dropout bike so long as I use a chain tensioner to make sure the chain is tight?
2. I have a hub which is 6 speed shimano uniglide that i was told is of the threaded variery...Can I use this ok?
3. Using this hub do I still need to get the rear wheel dished for single speed..if so, why?
4. How do I get it so the chainline is correct..Do I put spacers before the sprocket to space it out to align with the chainring, then put the sprocket on and a lockring?

Any help would be greatly appreciated.

Thanks Ahead
Dan

 

[brodie]

1. I believe I can convert to fixed on a vertical dropout bike so long as I use a chain tensioner to make sure the chain is tight?

No, you can't use a tensioner, and you need horizontal dropouts. Vertical might work, but it's either a bodge or a very expensive hub.

2. I have a hub which is 6 speed shimano uniglide that i was told is of the threaded variery...Can I use this ok?
3. Using this hub do I still need to get the rear wheel dished for single speed..if so, why?
4. How do I get it so the chainline is correct..Do I put spacers before the sprocket to space it out to align with the chainring, then put the sprocket on and a lockring?

If you've got a screw on freewheel hub, you can fit a fixed sprocket. You then need to re-dish the wheel to bring the hub and sprocket further to the right to have the correct chainline. And you can't use a proper reverse thread lockring so you should keep the rear brake.

All this info's already out there:
http://www.sheldonbrown.com/fixed-conversion.html
although they insist on using "fixed gear" instead of the correct "fixed wheel", "fixed gear" means one gear ratio!

 

[RedBike]

1. I believe I can convert to fixed on a vertical dropout bike so long as I use a chain tensioner to make sure the chain is tight?

no, the moment you stop pedalling the rear wheel will start to pull the chain taught, ripping the tensioner off or causing major damage to the frame.

Unless by fluke the chain happens to be exactly the right length there's no cheap way to make a vertical dropout bike fixed wheel.

2. I have a hub which is 6 speed shimano uniglide that i was told is of the threaded variery...Can I use this ok?

Not really. A fixed sprocket will fit. However you wont be able to fit a lockring, so the moment you stop pedalling the chain will be unscrewing that sprocket. You can fudge it with locktite etc but it's not really advised.

3. Using this hub do I still need to get the rear wheel dished for single speed..if so, why?

You need to make sure the chainline is correct. (The front and back cogs line up)
If you just screw a sprocket on the hub there's no guarantee it will be in the right place.

4. How do I get it so the chainline is correct..Do I put spacers before the sprocket to space it out to align with the chainring, then put the sprocket on and a lockring?

You can't get a lockring on. These need a left handed thread which your hub hasn;t got. You could fit a lockring from a bottom bracket and hope it stays in place.

You could just make the bike single speed?
You could then use a tensioner which will compensate for a small bit of miss-alignment between the sprockets and save you the trouble of re-dishing the wheel.

 

[RedBike]

I've just seen a pic of the bike you're converting. It looks like you've got forward facing sloping dropouts. With a half link chain there might be enough adjustment there to allow you to do without a chain tensioner.

You can't run a biopace chainset though.

 

[Losidan]

Hmm,

it would seem my plans are scuppered somewhat....

I have read items out there but it wasnt clicking in for some reason...I've bought a round chainring but it seems to be escalating what I need to do...Now it looks the hubs are going to be a prob too!

 

[MacB]

other alternative to chain tensioning is an eccentric BB, expensive but should do the job. Trickstuff do the Excentriker, this allows chain tension to be adjusted at the BB.

 

[brodie]

Re lack of lockring on screw on freewheel hub.

The sprocket's not going to unscrew as soon as you apply reverse pressure on the pedals. It might on the first ride, but after a hill climb or some miles it's going to be very tight. It's fine as long as you don't do heavy leg braking and have a rear brake, ie you don't have to rely on the sprocket not unscrewing.

 

[hubgearfreak]

You can't run a biopace chainset though.

you can. and you needn't take just my word for it.....

http://www.sheldonbrown.com/biopace.html

 

[betty swollocks]

Are you sure you have vertical dropouts?
From the pic it looks v much like the middle of the three here
If it is the middle one, your chain tension problems are solved. I ran a fixie with this type of dropout for years.
If indeed you do have vertical dropouts, you need either and eccentric b/b or an eccentric hub like the eno
As for chainline, you do not need to have the wheel redished (you'll have a stronger wheel if you do though), but you will need to space the fixed sprocket out. You won't be able to use a lockring, as these screw on anticlockwise.

Hubjub and Velosolo do lots of interesting components and spares.

 

[brodie]

Looks like vertical to me.

As for chainline, you do not need to have the wheel redished (you'll have a stronger wheel if you do though), but you will need to space the fixed sprocket out.

There isn't enough threads on the hub to space out the sprocket. You need to remove some of the axle washers/spacers on the right hand side and fit them to the left hand side. This will move the hub and sprocket towards the right and make the chainring and sprocket line up. Of course, the rim is now no longer central between the hub locknuts, and the wheel probably won't even fit into the frame. So the final step is to re-dish the wheel.

 

[Losidan]

thanks for the replies so far guys. It is deffo vertical dropouts I have.
So, Take the axle out and change the spacers/washers until I get the chainline straight? Have the wheel redished.

However, using a chain tensioner is out? So...am I still sunk?

 

[swee'pea99]

I'm in the middle of the same process, so...good luck! The one big difference is that my frame is horizontal dropouts, give or take. From everything I've read, I think starting out with vertical dropouts is a recipe for grief. If I were you, I'd think seriously about looking on ebay for a more appropriate frame. You can get good ones for well under the ton, and then you don't need to spend extra on bodges.

Beyond that, I saved this for myself t'other day...can't quite remember where I got it, but it seemed to make sense:

Respacing the rear wheel requires taking off the cone lock nuts and moving spacers from the right side to the left side until you get the sprocket in direct fore/aft alignment with the chainring.

• 
  [*]You can determine your chainline numbers by measuring the distance between the dropouts.
  [*]With the wheel in the dropous, measure the distance from the inside of the dropout to the center of the sprocket. (The sprocket should be fully spun onto the freewheel threads.)
  [*]Take half of the dropout measurement and subtract the dropout-to-sprocket number and you have the centerline-to-sprocket measurement.
  [*]Up front, it's the centerline of the bike to chainring measurement. Usually, the center of the bottom bracket will be fairly easy to gauge.
  [*]With a small ruler, measure from the center of the bottom bracket tube to the center of the chainring.
  [*]The two numbers will have to be within 1 mm for a good chainline.
  [*]Use chainring bolt spacers to position the chainring in or out on the crank arm spider.
  [*]You will also need some rear axle spacers to get the sprocket where you want it.
  [*]Many old rear hubs have one large right side spacer. You'll need to replace this with a number of smaller ones. The spacers go between the hub's cone nut and the inside lock nut.
  [*]Most any bike shop will have spacers.

Hope that helps. Like I say, good luck - keep us up with progress!

 

[andrew_s]

Vertical dropouts aren't good for fixed, which is why solutions such as the Excentriker BB and ENO hub are made. Chain tensioners should only be used with singlespeed freewheels.

It is sometimes possible to use what's called a Magic Gear - a combination of chainring and sprocket size that just happens to give an acceptably tight chain. You increase your chances if you have a half link available, and file your dropouts to allow a mm or two of axle movement. If you can measure your effective chainstay length accurately enough, there's a calculator that will tell you what chainring/sprocket sizes are suitable for your bike.
The problem with a magic gear is that what's right with a new chain will be too slack with a part worn chain.

If you are feeling particularly brave, there's also the phantom chainring:

Lockrings:
If you don't have a proper LH-threaded lockring, leave the rear brake fitted and don't try to brake hard using the pedals (skid stops and such). The pedals will be OK for speed control once you've ridden up a steep hill or two.
Using an old RH-thread BB lockring isn't much good - if a well screwed on sprocket is coming off, the BB lockring will just unscrew with it.