stevegor

Hi, long time cyclist here, but new to tandems,

I am looking at an older model with an eccentric front bb?, it's larger than usual bb's, it also has cottered cranks which I'm hoping to replace with more modern ones. Can I buy a cotterless eccentric bb?

Retro Grouch 

Generally the eccentric is a separate piece that an ordinary bottom bracket fits into.

Dr.Deltron

Why bother unless they're ruined? It won't make you go any faster.

I just aquired an old 70's Gitane tandem. Only reason I bought it at all, was the cranksets were both fine.
Albeit, cottered AND French!

Even using those cranks, it'll still be 6 months & $1K to get it on the road again.
But it's SOOOO COOOOL! Diamond frame in front & mixte in the back.
Plus factory cantilever bosses and a rear drum brake to boot!

Couldn't pass it up for $30!

Good luck with yours and have FUN with it. Old tandems are dabomb!

stevegor

This one has a 5 speed cluster incorporated with a rear drum brake AND 2 chainrings, woo hoo !!
a 10 spd, I was wondering if I could add another one and make it a 15 spd , or alternatively put a Shimano trible bb and cranks and leave the captain's cranks as they are.
It has 26" wheels with cantilever brakes, both of which I prefer over 700c and calipers for a tandem, smaller but stronger and canti's stop better.
What is the ideal sizes of chainrings for a double and a triple?

Thanks

mrfish

No such thing as 'ideal' gear ratios - depends what you want to do, and you can bet you'd like a gear you don't have some of the time. Some people on some websites get worked up about whether or not the cassette has a 16t sprocket or not, but IMO standard combinations work fine as long as you have a low enough gear for the hills you climb.

For a double, the modern compact sizes are good I think for general use; 50x34 which you can couple with a 12-25 [not sure if you can get this in 5 spd] or so for a reasonably wide gear spread. This may not be low enough for a combination of off road / less trained legs / steep hills

On a triple I think the key is to get a big enough big gear as you'll always end up with a smaller one than on a double. For example an old MTB 48x38x28 is probably a bit low for fast road, but fine for MTB or touring.

Personally I'd always take the triple on the tandem.

stevegor

The tandem will be used for general road riding and small tours, probably not for off road or fast Saturday morning bunch rides, but I would like some speed in the big gear. I usually ride with a strong group and there's a guy who rides a 700c wheel tandem with a blind stoker, man do they fly!! They have a 54t big ring, which I think would work well with 26" tandem, maybe 54/44/30?
I might even coldspread the rear so I can fit in a 9 speed hub with a xt derailleur and 105/ultegra STI shifters, does anyone know how well STI works with cantilevers and xt?

Cynikal 

The brakes will work with STI.

mrfish

re. whether STIs work with cantis - they do work with short cantis like Avid Shortys. They don't work properly with vee brakes unless you use a travel adaptor or similar. I'm sure there are numerous threads on this, or Sheldon Brown's site has something I think.

re. 54t... I used to do a lot of time trialling, and those pushing 55t rings etc. weren't always the fastest. Chris Boardman did his 25 mile competion record on 52x13, so there is a lot to be said for pedalling fast. IMO 52x11 is plenty fast enough and gets you an extra cog down the block versus a 54 which helps you cruise along without cross chaining too much. Only advantage of the 54 is that the chain wrap angle round the block is less because you're in a bigger cog, so it's swings and roundabouts. My view is that it's best to optimise your gearing for the speed you spend most time at. Round here it's rare that you get to 45mph, and when you do you don't spend much time there, so it's not going to make much difference to average speed.

stevegor

Thanks, that's good advise.....maybe I'm being too ambitious, I thought because the wheels are 26" I might need a slightly bigger ring to match a 700c wheel, but spinning is OK...hated those grinding TT's anyway.

xbz

The 1970s' Gitane Tandems have steel cranks with 5 bolts which can bolt onto old TA French chainrings, so you can fit alloy double or triple cranks to an old Gitane without replacing the crank arms. If you do mess more, you will find that the bottom brackets and pedals are French threaded. I recommend alloy rims, so the brakes have something softer to bite on than chrome rims. These tandems are ok for lightweight riders, though I put on a newer fork which was better aligned and stiffer than the old one - my old Gypsy does not weave down the road like she used to - 30 cycles/minute. New cables, chains, and brakepads help, and a large flange front hub.

stevegor

The resto tandem sold for too much on eBay and it wasn't in working order, and as fate would have it (??) another one came up for sale locally....3 yrs old in perfect working order, ideal for now until I decide what I want to do to it ie: better rims, derailluer etc.....sort of a working work in progress.
It has 26" wheels with a 48/38/28 set up, I was wondering, for more top end speed, if I changed the big ring to a 52t, would that have any effect on the front derailluer changing down to the 2 lower rings?, or if I changed the rear sprockets to 11t or 12t rather than the 13t it now has, would that be a better idea?