Fixed conversion questions

Dogtrousers

Kilometre nibbler
Hello there FG & SS forum. I'm toying with the idea of becoming a hipster.

My only experience of fixed was a when I was about 15, I got an old heap with reversible fixed/freewheel rear hub. I tried riding it fixed to and from school for a bit but I didn't like it, so my career as a proto-hipster stalled in the 70s. Now I fancy playing around with it again, just to see what all the fuss is about.

I'm thinking of putting a fixed wheel onto my 80s era Dawes, just to give it a go. I may well return it to its current derailleur setup once I have tried it. Actually, I'm even more likely not to do it at all, it's just a possible project at the moment.

It has 120mm (I think) forward horizontal dropouts and a 50/34 Stronglight double chainset, with a cartridge BB (Stronglight JP400). Current wheels are 622mm rims and that's how the brakes are set up, so I'd want to stay with them. I'd be keeping both brakes.

So assuming I can get a wheel with a 622mm rim and 120mm OLN fixed hub I'd need to figure out what to do about the crankset.

Would it be possible to run the fixed off one of the existing chainrings (probs the 34) without running into chainline problems? Could such problems be addressed by fiddling round with spacers on the axle (or spacers by the sprocket) to shift the wheel relative to the frame or the sprocket relative to the wheel?

Or would I need to fit a new chainset too. And if so, how do I figure out what BB to get in order to get the chainline right?
 

Cycleops

Guru
Location
Accra, Ghana
If you're willing to forgo the fixed option you can convert the bike to single speed by adjusting the derailleur set screws to run on one cog. I've done this on an old CB mtb and works fine.
Doing the conversion to flp flop hub will involve a lot more work including dishing the wheel and wouldn't be easy to change back.
If you want to go ahead with the fixie RJs video might help you out;

View: https://youtu.be/sInijI1vr34
 
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The only reliable way is to do the following:

1. Get the wheel first. I would recommend something that runs a wider chainline than the "track" semi-standard of 42.5mm, as this increases the number of cranksets that will work. Miche single-sided track hubs are cheap, can be respaced for a 46mm chainline and this much improves the dishing of the built wheel - it's a win/win.
2. Get a 2' steel rule or other known straight edge.
3. Without a chain in place, see how either ring lines up with the sprocket. If it's not perfect, measure the existing BB and this should tell you what BB you need to make it just right (I'm assuming the BB is symmetrical, in which case you need one 6mm shorter to bring the chainring in by 3mm). You will need a very short BB to use the outer ring position. I think Stronglight use ISO taper.

Forget calculating chainline from the centreline, or measuring it at the rear and trying to achieve the same measurement at the front. Frames, especially steel ones, are rarely straight enough for this to Just Work.
 

dave r

Dunking Diddy Dave Pedalling Pensioner
No reason why you can't run on the inner ring and then dishing / space wheel to line up the chain line

@Dogtrousers if you were more local i would say come and try one of mine for a few miles
Very many years ago when I converted my 12 speed Pollard to fixed I brought a cheap track wheel with a flip flop hub and a new chainring which I fitted in the inner ring position and used thick washers under the chainring bolts to pack them out to compensate for no outer chainring.
 
OP
Dogtrousers

Dogtrousers

Kilometre nibbler
single speed bike (used) are cheap.
I bought one for £50, needs a bit of TLC but nothing that wont cost more than £20 to sort.
Maybe so, but I don't want another bike. That's why I'm converting one I already have.
 
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fossyant

Ride It Like You Stole It!
Location
South Manchester
Maybe so, but I don't want another bike. That's why I'm converting one I already have.
Darn it, I could sell you a rather nice fixie.
 
OP
Dogtrousers

Dogtrousers

Kilometre nibbler
:laugh: Sorry chaps, but I hardly ever ride the Dawes as it is. So getting in another bike (that I also probably would hardly ever ride) doesn't appeal to me.
 
OP
Dogtrousers

Dogtrousers

Kilometre nibbler
The fact that you guys have spare fixed wheel bikes lying around unused makes building a temporary fixie that can be transformed easily back into a sensible bike once I've realised it's a daft idea seem almost a sensible plan.:wacko:
 

All uphill

Senior Member
I did something similar with an old 531 Raleigh this summer. I bought a cheap flip flop wheel and singlespeed chain and used the existing crank set.

With a bit of fiddling it works a treat and is great fun! Better than I expected.

For me it's great because of the low weight contrasting with my tourer.
 
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