Converting from double to triple chainring?

[Kins]

Ok, got an old Falcon 6 speed as my commuting bike rather than use my MTB.

I want to change from 2 to 3 chain ring and maybe cassette from 6 to 7 speed as its quite a bit hillier when I change my work route due to moving to work down the road.

The rear dropouts are 132mm but need slightly prising opena couple of mm with hands to drop the wheels in so are probably 135mm. If I read Sheldon right I should be able to go to 10 speed?

Wheels on it are old heavy ones and in average condition so want to swap them out when convenient.

Cranks and set are all very heavy so would rather change these soonish and then do wheels when funds allow or a cheap set is on ebay.

Shifters are on down tube so if reading various articles these should be ok? Just a matter of seeing if the front dérailleur can shift 3 rings and finding bcd? Would I have to change the bottom bracket?

 

[yello]

Anything is do-able given time and money, and I'll be interested to read the thoughts of those more experienced that myself. It'd be a learning experience, that's for sure!

But my gut reaction (and I know it wasn't your question) is that it'd be a whole lot cheaper (not to mention less time consuming) to buy a 2nd hand bike.

 

[Kins]

But my gut reaction (and I know it wasn't your question) is that it'd be a whole lot cheaper (not to mention less time consuming) to buy a 2nd hand bike.

Bike was cheap and I would rather learn to do this sort of thing, and I enjoy tinkering. I probably won't buy anything new except the consumables.

 

[mrandmrspoves]

Down tube shifters should be fine if friction shifters (some have option to index or use as friction) Front mech may be ok - but cheap enough to replace if not. You will probably need a slightly longer spindle to stop the small chain ring catching the chain stay .....but some cranks are convex and others concave where they fit onto the spindle. If you do need to replace - I would suggest replacing with a cartridge BB.

 

[yello]

Bike was cheap and I would rather learn to do this sort of thing, and I enjoy tinkering. I probably won't buy anything new except the consumables.

That's the answer I like! Good on ya

 

[sidevalve]

I assume you mean it's a 12 speed bike [2 rings on the front 6 on the rear]. If so surely the easiest way is to just change the rear cassette to change the overall ratios. If it's standard it's probably a 24 large sprocket, changing to one with 28 will make a surprising difference. If it's not a shimano style spline cassette but a good old screw on type then look out for one for an old MTB these were usually exactly the thing you need and are pretty easy to find on E bay for just a few pounds.
Remamber it aint how many you've got it's how big they are.

 

[mrandmrspoves]

.....as for going to 10 speed. If you have 6 on the rear 2 on the front - you already have a 12 speed.
If you mean to go to a 10 speed cassette on the rear wheel, it would be very expensive and unlikely to achieve a better range of gears than using a triple on the front.
An alternative route if all you want to do is achieve a really low gear is the Shimano Mega Range cluster....this should swap directly with what you already have and avoid expense of the other parts. They do a cassette and freewheel version . http://www.ebay.co.uk/itm/SHIMANO-1...sure_cycling_bikeparts_SR&hash=item416f64f219

 

[Kins]

.....as for going to 10 speed. If you have 6 on the rear 2 on the front - you already have a 12 speed.
If you mean to go to a 10 speed cassette on the rear wheel, it would be very expensive and unlikely to achieve a better range of gears than using a triple on the front.
An alternative route if all you want to do is achieve a really low gear is the Shimano Mega Range cluster....this should swap directly with what you already have and avoid expense of the other parts. They do a cassette and freewheel version . http://www.ebay.co.uk/itm/SHIMANO-1...sure_cycling_bikeparts_SR&hash=item416f64f219

Thanks for the link. I have no intention of going further than 7 speed cassette as below 8 they seem to be relatively cheap. I was just stating that if you read Sheldon it says a possibility to go to 10 speed cassette with that rear dropout dimension.

My aim is to get 21 gears from the two conversions.

 

[simon.r]

My aim is to get 21 gears from the two conversions.

Why?

As @sidevalve says "Remamber it aint how many you've got it's how big they are."

As I understand it the benefit of having lots of gears is to enable you to keep the same cadence for any speed. For most of use mere mortals it doesn't make any real difference if when we change gear our cadence increases or decreases a bit. I still think that 8 or so fairly widely spaced gears would be more than adequate for the vast majority of us.

Take your point about wanting to tinker, but unless you have a triple chainset and BB lying around I'd be very tempted to change the rear cassette only as a starting point and then maybe consider putting a smaller inner ring on the double chainset if you need to go lower.

 

[yello]

In my limited experience, such tinkering can be something that turns around and bites your bum.... and you end up spending more and more buying odd little bits, or tools, and it never being quite right. It's always a learning experience, and worth it for that alone, but it can also be frustrating path as something that should, in theory, be a straight swap turns out not to be - despite assurances to the contrary.

Conversely, I did a triple to compact conversion that turned out to be a doddle despite what I was being told. Reckon I got lucky.

 

[Kins]

Take your point about wanting to tinker, but unless you have a triple chainset and BB lying around I'd be very tempted to change the rear cassette only as a starting point and then maybe consider putting a smaller inner ring on the double chainset if you need to go lower.

Well, I have to change the wheels anyway so it will probably be the way I go, though I will change the whole front, because they are very very heavy and even more importantly, look naff.

Also whats the difference between Shimano MTB and Road rear cassettes and are they interchangeable?

 

[simon.r]

Also whats the difference between Shimano MTB and Road rear cassettes and are they interchangeable?

Nothing but the sprocket sizes.

Things you'll need to check when buying / fitting a MTB cassette to a road bike:

Splined or screw-on?
Number, sizes and range of sprockets
Compatibility with chain / chain-rings
Chain length
Compatibility with rear mech - the 'capacity'. http://en.wikipedia.org/wiki/Derailleur_gears) explains it better than I could!:

Cage length

The distance between the upper and lower pulleys of a rear derailleur is known as the cage length. Cage length, when combined with the pulley size, determines the capacity of a derailleur to take up chain slack. Cage length determines the total capacity of the derailleur, that is the size difference between the largest and smallest chainrings, and the size difference between the largest and smallest sprockets on the cogset added together. A larger sum requires a longer cage length. Typical cross country mountain bikes with three front chainrings will use a long cage rear derailleur. A road bike with only two front chainrings and close ratio sprockets can operate with either a short or long cage derailleur, but will work better with a short cage.
Manufacturer stated derailleur capacities are as follows: Shimano long = 45T; medium = 33T SRAM long = 43T; medium = 37T; short = 30

Example of how to work it out from http://singletrackworld.com/forum/topic/rear-derailleur-total-capacity:

it's basically the difference between the big-big gear and the small-small gear (although there are other ways of phrasing but the answers are exactly the same)
eg. (on a roadie)
big-big could be 53 and 25
small-small 39 and 12
difference is (53+25) - (39+12) = 78 - 51 = 27
obviously longer cage mechs have a bigger capacity

 

[Kins]

http://home.earthlink.net/~mike.sherman/shift.html seems handy to work out what you end up with.

 

[ufkacbln]

Make sue you have sufficient clearance for the frame whilst maintaining a reasonable chain ine.

 

[simon.r]

http://home.earthlink.net/~mike.sherman/shift.html seems handy to work out what you end up with.

I like that, hours of fun to be had if you're anal as I am