Might go single-speed...

[MikeD]

Disagree , many trials riders still use a freewheel as the only hubs strong enough are made by Chris King and Hope ( and the Hopes don't like mud ) .

I'm not a trials rider

A freewheel has it's ratchet directly bellow the teeth within itself whereas a cassettes ratchet can be as much as an inch to the left , not the best mechanical principal .

On the other hand, said freehub body is usually very well supported by bearings.

Many bmx cassettes start to skip and get weak after very few miles

The Shimano DX hub is essentially an MTB hub, it's just got a short freehub body on it (which also addresses your offset-forces point).

when it's looking crap and the clacks aren't as loud as they used to be unscrew it , throw it in a bin and screw a new one on ; do that with a cassette hub .

A Shimano freehub body's a tenner two. And you can remove them without the aid of a vice and copious swearing

 

[perry]

I'm not a trials rider

But your still exerting similar forces onto your drivetrain .

On the other hand, said freehub body is usually very well supported by bearings.

Your forks are also supported by bearings but that doesn't stop them twisting at the dropout . Just because there are bearings underneath the sprocket doesn't mean there wont be misalignment with the pawls and ratchet ring along the freehubs length . The freehub is a separate piece that relies on the axle never flexing so will never be as reliable as having the ratchet and pawls directly over the sprockets teeth . bend the axle on a freewheel hub and the mechanism will still work ; a bent cassette axle will make it skip or jam .

The Shimano DX hub is essentially an MTB hub, it's just got a short freehub body on it (which also addresses your offset-forces point).

It also uses cup and cone bearings , leaving the freehub unsupported . Its a narrower freehub but it's still not directly over it so no it doesn't .

A Shimano freehub body's a tenner two. And you can remove them without the aid of a vice and copious swearing

Can you send me some sprockets please ? They must be free and never wear out as you've forgot to add that cost Vice or chain whip , as I've never had a vice snap I know what I'd choose and swearing isn't a good tool to use ; keep some stern words in your tool box ready for the stubborn parts

 

[MikeD]

But your still exerting similar forces onto your drivetrain .

I'm sceptical, but if you've done the sums... Seems like pedal-kicks and big drops are a very different scenario to pedalling up a hill.

Your forks are also supported by bearings but that doesn't stop them twisting at the dropout .

I call straw man - forks are cantilevered beams, it's an entirely different scenario.

The freehub is a separate piece that relies on the axle never flexing so will never be as reliable as having the ratchet and pawls directly over the sprockets teeth . bend the axle on a freewheel hub and the mechanism will still work ; a bent cassette axle will make it skip or jam .

But it's easier to bend the axle on a freewheel hub because one of the bearings is a third of the way along the axle. Swings and roundabouts, innit?

It also uses cup and cone bearings , leaving the freehub unsupported . Its a narrower freehub but it's still not directly over it so no it doesn't .

It's outlasted screw-on freewheels, that's good enough for me. I ditched freewheels on geared bikes a very long time ago, I don't see any compelling reason to use them on singlespeeds ;-)

Can you send me some sprockets please ? They must be free and never wear out as you've forgot to add that cost

They last for ages. What's the logic in replacing the sprocket and the mechanism at the same time (cf freewheel) when the two bits wear at different rates?

Vice or chain whip , as I've never had a vice snap I know what I'd choose

The freewheel tools like to shed prongs, though. On the other hand I've just thought of a good reason for 29in rear wheels ;-)

 

[perry]

Your quoting skills are strong

500lbs of force is still the same no matter how it is being applied .

But it's easier to bend the axle on a freewheel hub because one of the bearings is a third of the way along the axle. Swings and roundabouts, innit?

That point is as worthless as mentioning dish . http://www.dmrbikes.com/?Section=produc ... =HUBRSSD10

Full 135mm width singlespeed freewheel hubs have been easily obtainable for at least 10 years . Quite frankly I'm shocked someone as knowledgeable as yourself has bothered to mention the axles supported width .

They last for ages. What's the logic in replacing the sprocket and the mechanism at the same time (cf freewheel) when the two bits wear at different rates?

Because I can buy a decent new freewheel for £10 that has all the parts that wear ( chains and chainrings have nothing to do with what were talking about , we need to change those regardless of the chosen hub ) Wasn't your point that you can also change a part for £10 ? it's not both parts though . Even if I change a freewheel with amazing teeth that will last a few thousand more miles its still £10 with no extra cost for a 2nd part . The ratchet ring in the hub is a non wearing part , which is a shame because that can be pulled out of the hub shell at home .

 

[MikeD]

Axle support - fair cop, I may have accidentally strayed into a "multi-geared hub" argument for a moment there ;-) You're the one mentioning dish, though...

What sort of unit of force is lb? :-D I haven't looked into this, but intuitively (and yes, intuition is always dangerous) trials seems like sudden peak loads while Just Riding Along is more even. Like the difference between hitting something with a hammer and just putting a hammer on it ;-)

Anyway, my main point is that £10 freewheels are shit in various ways and I don't like to use them. YMM and clearly does V. Vive le difference, and all that.

I think the main problem with singlespeed freehub wheels is the one to which you alluded way up there somewhere - there are a lot of cheap but crappy ones out there, and the non-crappy ones are also non-cheap. I'm happy with my modded DX one, not sure what I'll do when it eventually dies.

(quote-fu somewhat lacking in this one ;-) )

 

[perry]

I think we have both put across both hubs fairly well , it's a shame my spare hub is in Scotland for the foreseeable future otherwise I'd have sent you a dmr revolver hub , acs freewheel and ex721 rim to try , they make a great wheel I'm sure you would like .

 

[MikeD]

You're probably right, I'm generally quite well-disposed towards bicycles ;-) My SS is somewhat of the jey persuasion for an EX721, though, I think:

 

[NakedGav]

I use a Shimano DX BMX freehub that's only got room for one sprocket, with a longer axle and suitable spacers (they're 120mm as standard).

How easy is it to convert BMX hubs to the right spacing ?

 

[MikeD]

Depends on the hub. The Shimano one was easy - the actual hub shell is the same as an LX one of the same vintage, the bearings and cones and stuff are all the same. You need the longer axle out of an MTB hub and some spacers to get the locknuts out to the right width. Mine's done to put the sprocket at 47.5mm from the centreline so it lines up with a chainring on the middle-ring position on a standard crank. Or a standard crank at the time I did it - modern outboard-bearing stuff's all 50mm now.

Other hubs I have no idea, but likely to be more challenging.

 

[perry]

I've considered respacing the frame to take one particular bmx hub I like but have never bothered . What hub is it you want to use , or is it a general idea ?