Suicide hub

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.

I rode even brakeless with a suicide hub for a while, like one year or so...
to have a minimum safety there are some tricks to improve the locking of the sprocket...
the first thing is not to use a chain whip to screw on the cog but the metodo pettenella (or rotafix for the americans : http://en.wikipedia.org/wiki/Rotafix) this helps to screw the sprocket way more than using the chainwhip (I usually do it even on track hubs)
to help the rotafix effect you have to add **lots **of loctite (not the one to stop the screws, the real super glue) on the thred of the hub and on the side of the sprocket that will get in touch with the hub.
another thing that helps a lot, if you chainline allows so, is to add a thin washer (there are some made for freewheels) before screwing the cog. usually are made of softer metal and, when you rotafix the cog, the washer get squeezed and act as a "spring" keeping the cog there...

on top of it, if the hub has enough thread you can screw on a bb lockring...

mind: the metodo pettenella is applying a LOT of power on the thread that, occasionally, might strip... (good excuse for your friend to get a proper track hub...)

warning: I'm NOT suggesting to ride a suicide hub brakeless..

exactly what loctite are you refering to?

ive just mesured it accurately and i seems i have massivly over estimated the gap between the hub. its actually 15mm. im guessing i just need to fill this void with spacers, but seems like a big gap for just spacers to fill, is this going to be ok?

a good person to ask about this would be xsheepx or smallbrownbike, not that I'm trying to volunteer other people without their permission or anything. Not sure sheep's in the country at the moment though.

Maybe i mis read your description but the way you explain it it sounds like your mate is converting to singlespeed?

exactly what loctite are you refering to?

ive just mesured it accurately and i seems i have massivly over estimated the gap between the hub. its actually 15mm. im guessing i just need to fill this void with spacers, but seems like a big gap for just spacers to fill, is this going to be ok?

Have you re-spaced the hub axle ? Will probably also need to re-dish the wheel

heres the plan: flip BB axle to bring chainring closer, remove casette, put spacers on to get the chainline correct, rotafix cog with locktite, add lockring, and pray it works.

i cant redish becuase the spokes/nipples are pretty rusty in places.

im kind of convinced that it will hold up to skidding as long as its on tight enough.
what im concerned about is that the wheel is quick release, and that the chainline is going to be well out. i cant really check/estimate the line becuase the bike is at my mates house and we havnt tried flipping the axle yet.

Ok first of all if he has a cassette you can not covert to fixed without a surley fixed or some more serious hacking.

However it sounds like he has a multi speed freewheel NOT a cassette. In which case he needs to remove the freewheel, buy a track cog, rotafix + loctite (red is prob best) as stated by Pepperoni and redish the wheel and maybe change the bottom bracket to tweak the chainline. Being as this is a hack you may as well just play around with dish and spacers on the axle.

P.S b.b tend to be symmetric to start off with so flipping it (which will only be possible if it is a non cartridge b.b) will not make any difference.

If you can't redish because of the rusty nipples you will have to give up. You can only tweak the chainline with spacers a few mm. 15 mm movement will not be possible. Don't do a ridiculous bodge on this as it will just be dangerous. I am afraid if you can't do the job properly your mate will just have to save up.

If you can't move the spokes/nipples then you're going to have problems when/if the wheel goes out of true.

I know you're trying to do it on the cheap, but you can only go so far. Get a second hand track wheel.

How much thread is there? you may be able to use a flipped cog as a spacer.
But spray all the nipples with WD40, leave overnight, and try and re-dish first..
...well dodgey!

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

The clue is in the name.

2 brakes.

+1 for two brakes. You can still get brown trouser moments even with two brakes, so for the most peace of mind, try and get hold of a track hub.

Whoops, didn't mean to resurrect...

Nursery 'brake'out fail.

I have this hub on one bike, with rear brake only and works. Better not try skidding (maybe only in snowm haha)

i managed to do this to an old road bike. spokes were also rusty but left overnight with penetrating oil and all the nipples loosened up. had to redish wheel a fair bit, tweak axle spacing, After rotafixing, the sprocket never came off, and i've skidded through 3 tyres since. maybe the steel on alloy issue i always have with seatposts has worked in my favour for once. What did eventually go was the chainstays - huge fatigue cracks each side as the frame either wasnt designed for the being ridden fixed or had rusted through.

This is amazing.

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