melon

so my mates just got this ratty old road bike he want to convert to fixed on the cheap.

its got a 7 gear cassette on the back and 2 chain rings up the front. he wants to use the bigger of the two rings at the front, which lines up with the 4th biggest gear on the cassette. theres about 2.5mm between the hub and this gear.

im guessing theres good reason why more people dont do this and it all seems a bit shonkey to me. even if he still uses a front brake. ive told him hed be better off with just building a new hub but hes adamant to not spend money on it.


how can a suicide hub be made safe and reliable, if at all?

theres going to be about 2.5mm between the hub and the correct chainline, this seems like a big gap for spacers to fill, is this going to be a problem? redishing isnt really possible due to the state of the spokes/nipples.

we have all the tools neccessary to mod stuff if neccessary.

roadfix

First, by making sure the fixed cog is screwed on tight and secure, then by running at least a front brake and not relying too much on back pedalling when slowing down. Your suicide hub should be fine.

melon

whats the deal with the big gap between the hub and sproket, is it ok to have that much spacer?

roadfix

OK. Are you running a fixed cog or are you using the existing freewheel cassette and running it as a single speed?

zzyzx_xyzzy

With a multispeed cassette all the cogs you aren't using are "spacer" whenever you aren't using them. So it'll be as reliable as the multispeed cassette was.

This is an excellent way to set up single speed on the cheap. I don't know about fixed, though - I've heard of people welding the freehub body to the hub but that seems pretty sketchy.

melon

i want to remove the freewheel cassette and replace is with a fixed cog. so basically putting a fixed cog on a non track hub.

melon

just meausred it, massivly over estimated the gap, its actually 1.5mm.

roadfix

Chain line difference of 1.5mm is no big deal. There's no problem running that.

Seggybop

The reason more people don't do this is that they care more about having "real track bike" components than getting a functional bike for a reasonable cost and use safety as an excuse (if you ride around with no brakes you're unsafe regardless of your hub), or they are misled by the aforementioned people.

benhenley

If its a cassette then you will be making a single speed by putting a cog on there.

If it is actually a freewheel then you will be making it a fixed gear by putting a cog on there.

Your using both words so its hard to tell which type you have. If its a cassette then you will have to get a new hub for a fixed. If its a freewheel then you can use the suicide hub method or buy a new hub.

melon

whoops ive made some mistakes. ive been meaning to say freewheel.

also i meant to write 15mm, not 1.5mm.

so a suicide hub installed well should hold up well to everyday use, including skidding?

roadfix

In most instances, no. Install a front brake and use it.

You also need to respace the axle and dish the wheel to correct the chain line.

melon

well this is what ive been asking about.

i want to do a ghetto conversion. no respacing, no redishing.

here was the plan:
i remove the freeweel, add spacers to get correct chainline, screw the cog on, affix with loctite+lockring- job done.

now what i want to know is if this is going to work. the spacers are going to have the fill a void of 1.5mm. is this going to work?

is a suicide hub capable of being used daily with skidding, i.e. is going to work?

what can i do to improve my chances?

frankenmike 

Some people claim to have used suicide hubs daily for skidding and braking with no problems. I personally wouldn't use suicide hub set-up for anything but forward pedaling.

Steev

Judging by your mention of spacers, 15mm gaps and 7 speeds, I have to think that is a freehub and cassette that you're trying to convert.
Check this link.
https://sheldonbrown.com/fixed-conversion.html#hub
How are you locking the pawls?
I tried a locked up freehub to see if I liked fixed gear and found a problem in that the interface between the freehub body and the hub moves fractionally back and forth between forward pedalling and resisting, the movement was enough to work the retaining bolt out over time. Make sure your friend uses a brake. I doubt it will prove durable, especially if he plans to do lots of skidding.
Most people use "suicide hub to mean a track cog screwed onto a freewheel hub with no lock ring

roadfix

Not quite. There's not enough threading on the hub to add spacers to correct chain line. Remove the freewheel and you'll see what I'm talking about. There's not much threading holding the freewheel.

Are you sure you have a threaded hub???

melon

im pretty sure it is alough i cant really check it now im at home. how can i tell without removing it?

fuzz2050

Suicide hubs work fine, provided you rotafix them (search can be your friend)

It will work fine for forward pedaling, but the second you try to skid, it'll come undone. No kidding, the first instant. You will go down in a blaze of fixxter glory.

Ride it, but don't rely on it for braking. Leave on both the front and back brakes and keep them well adjusted.

Philatio

If you degrease everything first, rotafix the cog on, add a BB lockring, and use lots of red lock tite you won't have any problems.

I've been running mine for about 4 months/500 miles with no sign of trouble. I run only a front brake and do a reasonable amount of skipping/backpressure. From everything I've read, the people that have problems don't put it on right.

DannoXYZ 

Helps if you spin the cog on as tight as you can with a chain-whip. Then use a punch and hammer to really lock down the lockring.

A lot of the problems with cogs coming loose is people don't cinch down the cog tightly first. Even with the lockring tightened on it, chain-torque will still spin the cog away from the lockring and then everything's loose.

Philatio

yeah. I think it's worth it to crank it on as tight as you possibly can. I rotafixed (supposed to be more force than a chainwhip? guess it depends) rode up several hills and then rotafixed again.

Seggybop

Yes.

Anyone who's tried it and had a problem probably did it wrong.

You need to totally degrease all of the threads, and then put threadlocker compound on the threading like you'd normally use on brake bolts. Use rotafix method to tighten the cog with force beyond that what you can impart to it by pedaling. You need to be careful with this, because you can overtighten it and strip the threads. Then, screw on a bottom bracket lockring with a lockring wrench or a hammer and punch.
If after riding you find that there's any play on the lockring, the cog wasn't tightened enough. Tighten cog and lockring more.

If you do this properly, it would be necessary to exert enough force on the hub to destroy the threads before you managed to unscrew the cog.

A standard track hub set up without sufficient attention will certainly be more likely to fail than a carefully set up freewheel hub.

As for chainline, if you are using a road double crank with the chainring on the inside and the chainline is off, flipping the BB axle should align it.

patrick.decker@

It will work. I've tried skidding my cogs loose (before I made a 1/8" chainwhip) - after having put them on with liberal amounts of grease - to no avail. But I'd still never do it without a front brake.... well I wouldn't even ride a regular fixed without a brake.

bluenote157

ok.. so if it is a freewheel and not a cassette body, it can be done. I was running a fixed like this and accidentally skidded a few times... although i dont recommend it. Run a front brake.

So this is what you do...
Look up rotafix.. it is a way to tighten down a cog with more leverage than a chainwhip. Don't over do it or you might strip the hub.
Use red-loctite...then thread on a bb ring.

I've heard of others welding on the cog??

I actually did this rotafix with no loctite and no bb ring and it worked fine. However, again.. use this technique at your own risk.

melon

well, im going to give it a go, just to see how well it works. im not going to loose out on anything. good call on flipping the bb axle, i hadnt thought of doing that.

id like to know how many people have had success with this with skidding.


the bike isnt mine, but i can call the owner (not bike literate) and ask him simple questions.
how can i tell just by observation whever it is freewheel or freehub?



im now more concerned about the chainline.