Gears???

[BikeBuilders]

Just a little curious about something here.... I have done a lot of reading, and a lot of lurking here.... You guys do some amazing stuff. And I love the fact that building bicycles is a WHOLE LOT cheaper than building motorcycles. Perfect hobby for me.....

What I have seen is that some of these custom built bikes can end up being pretty darn heavy. Not so much the bikes here that I have seen, but on another site. Chopper bikes with big back tires to be exact. I like that style.

So, onto my question.... With all of the amazing things I have seen you guys do, why is it that all of the bikes I have seen remain single speed? Seems like it would be easy enough to at least add a rear derailer. This would give you at least a few gears. Even if you left the front a single sprocket only. I am sure there is a logical reason, just wondering what it is before I head down a road doomed for failure.

So what's the reason? Mechanically unadvisable, personal preference, oversight on my part????

Thanks
Rob

[cman]

Most like the simple style of a single speed coaster brake. No cables for brakes or gears.

3 speed internal geared hubs are popular or 2 speed kickback hubs.

[BikeBuilders]

That makes sense.... A cleaner look. But in the event I wanted to use a rear hub from say a 21 speed mountain bike, and the rear derailer (and possibly even front), there is no mechanical or other unforeseen reason it wouldn't work???? Or any experienced builder warnings, tips or tricks I should know about?

[jalopyjimmy13]

cable length

[BikeBuilders]

Understood.... Any other words of wisdom, warnings or tips???

[udallcustombikes]

I built my Monster Trike using an 18 speed gearing to spin the 31" Coopers.


One problem you may encounter with a wider rear tire is your chain line. If it is an issue you can employ a jackshaft compensate.

[Dr. Tankenstein]

Another thing to consider is the chain pitch. You have to switch your front sprocket from 1/2 x 1/8" pitch to 1/2 x 3/32" in order for smooth/proper operation.

Good luck!

Cheers,
Dr. T

[BikeBuilders]

Forgive the newbie question, but what is "chain pitch"??? Please explain....

[kingfish254]

Forgive the newbie question, but what is "chain pitch"??? Please explain....

Chain pitch is the distance between chain rivets. Almost all modern chains are 1/2 pitch.

The 1/8 and 3/32 that Tank refers to is the Chain Width (between two inner plates). Single speed and three speed chains are typically 1/8. Deraileur bikes are typically 3/32.

[wheelymarko]

I like simplicity! Mine is a coaster brake triplespeed.

[wimpy]

I like simplicity! Mine is a coaster brake triplespeed.

Mine too. And I used an 80 mm backrim (not wider),so I didn't have to alter the standard sprockets into off-set sprockets,because of the chain clearance. Any other wide(r) rim brings along the problem of how get the chain from front to back,in a straight line. So I chose the easy way.

[Bane]

Another thing to look at is the spacing of the hub itself. Most coatser hubs have a 118mm to 120mm spacing so the frame is built to match. A 6 spd or greater hubs spacing starts at around 125mm and go up to 135mm so you would have to spread the rear chainstays to make it work. Not a real big deal until but something to look at.

[BikeBuilders]

Forgive the newbie question, but what is "chain pitch"??? Please explain....

Chain pitch is the distance between chain rivets. Almost all modern chains are 1/2 pitch.

The 1/8 and 3/32 that Tank refers to is the Chain Width (between two inner plates). Single speed and three speed chains are typically 1/8. Deraileur bikes are typically 3/32.

Gotcha.... But if I use all the components (rear hub and sprocket, front spocket and chain) from the same donor bike, I won"t have to worry about changing anything, right??

[Dr. Tankenstein]

Gotcha.... But if I use all the components (rear hub and sprocket, front spocket and chain) from the same donor bike, I won"t have to worry about changing anything, right??

Yep, that'll work. Just be aware, most older and newer, single speed bikes use a one piece crankset, like this;


Now, if you can find a donor with a multi-speed rear, one piece crankset front, you're good to go.

However, if the donor has a three piece crankset (which most modern mountain bikes, BMX bikes, etc...use), like this:


You'll need to get a US-euro conversion kit, like this:

http://www.amazon.com/BB-Conversion-Bp-American-To-Euro/dp/B001G8TSPS

Good luck, keep asking questions, there's a LOT of knowledgeable people on here!

Cheers,
Dr. T

[BikeBuilders]

Thanks, but now I am confused.... If all parts come from the same donor bike, why would I need a us/euro conversion? Seems like all I would need to do would be lengthen the chain if necessary.