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jaytheman

I am getting my 73 Gitane TdF in running shape for occasional rides. I have all original parts except seat and brake pads. I think most all in very good shape. Pics: http://www.gitaneusa.com/forum/viewtopic.php?t=2632

I have bad sciatica and need to keep rides pretty short and not too stressful. The original 52/42T Sugino crank needs to be changed out for something like a 48/32T or similar if it is to get much usage after restore/cleanup. Also recommended to get some sealed BB to minimize future maintenance issues.

What are recommendations keeping the original TdF look? One suggestion was to try to locate Stronglight 86 bcd crank that can handle those chainrings but not at all sure if this is optimal, price etc. and then if I do find would choices be for BB.

My thinking is to replace the Sugino french threaded BB with another French threaded so one can go back to all original if desired at some point.

Ideas are welcome. Any idea what kind of budget I need for parts? I know this is a real WAG.

I am obviously a newbie with little knowledge of all concerned.

scozim

I just went with a Velo Orange French thread cartridge bb on my early 70's PX10 and it's working very well. For some reason when threaded in all the way the fixed cup was not seated/resting up against the bb shell so I had to fill the gap with a 1.8mm spacer.

Personally, if you have back trouble go with the crankset that works for you. I have a friend who swears by the TA Cyclotouriste and runs a 48-36 combo on his bike. The VO bb has a JIS taper so you may have some issues with chainline depending on the crankset you use. I have a Sugino Super Mighty crank that wouldn't seat far enough on the spindle so I switched to a Sakae CR crankset and it worked better even though the symmetrical look of the spiders on the crankset don't exactly match an early 70's bike. It works and that's all I care about. I have a Stronglight crankset - can't remember the model - that is a 110/74 bcd so you could theoretically a compact double like 50-36 on it. If you go that route just make sure to use a long cage rear derailleur to pick up all your chain slack while in the small ring - especially if you're running some bigger gearing in the rear also.

Old cranksets can be had for reasonable prices if you're diligent. The VO bb was around $45 or $50 if I remember correctly.

Scott

verktyg

Sugino Mighty Compe bottom brackets from the early 70s are approximately the same dimensions as the average Campy BBs from the that era. In general, the parts will interchange - YMMV. Confused

The specs for standard Campy BB spindles for 68mm wide French and British BBs were 114.5mm wide. 70mm wide Italian BBs were 115.5mm wide.

Campy BB spindles are marked 68 or 70 respectively. Most of the ones that I've measured the width on ranged from -0.5mm undersize to +1.5mm oversize.

Bear in mind, these were bicycle parts not Swiss watch movements and the variances were ~1/6" or less.

This was not only the case with Campy BBs but with Stronglight, TA, Sugino, Shimano, Suntour (SR), Avocet and some others too.

See my Flickr set for more info:

http://www.flickr.com/photos/28267220@N05/sets/72157627678462359/

Click on the pictures to see the explanations below them.

From the late 1960s through the mid 1980s standard Campy and Campy clone double cranksets used 52-42T chainrings

They had a 144mm BCD (Bolt Circle Diameter) and 42T was the smallest chainrings that fit (there are some rare 41T rings but they only drop the ratio by about 1").

Sugino and others made or make crank arms with a 110mm BCD that can use a 33T small chain ring that may work with your current BB (Sugino Mighty BBs generally had good quality bearing surfaces so if yours is in good shape try to same some money and reuse it.

If the replacement crankset takes a 113mm wide spindle it will probably work fine with a 114.5 wide BB spindle (~ 1/16" remember?).

If it fits, it works!

I wouldn't go for a triple crankset unless you want to change the front derailleur. Look for something like 48T-34T chainrings.

verktyg

Chainline issues were an obsession with the Brits way back in the day when they used stiff (no side play) 1/8" wide chains on single speed and Sturmey-Archer 3 speed hubs with a single external sprocket.

Part of the obsession had to do with imaginary losses in efficiency due FRICTION! That myth has been pretty much debunked!

Modern 3/32" chains with a lot of side flex work perfectly on bikes with 130mm wide hubs, 11 speed cassettes, triple chainrings and short chainstays.

Older bikes with longer chainstays used 120mm wide hubs and 5 speed freewheels.

SRAM brand PC830 or PC850 chains are inexpensive and shift great. Changing to one of these is the bestest , cheapest improvement you can do to the shifting on your bike! Wink

As far as BB spindle length goes, there are 2 1/2 considerations:

1. The inner chainring needs to clear the chainstay by several mm.

2. If the the spindle is too long, the chainrings will be too far away from the front derailleur and you may need to replace it.

2 1/2. Chainline problems can limit the number of useful gears because when the chain is on the smaller freewheel cogs and you have a big size difference in chainrings, the chain can drag on the inside of the large ring when it's on the small ring.

Measure the chainline with the crankarm on the BB spindle but not tightened down. In general before tightening there should be about 2mm or more space between the end of the spindle inside the square of the crankarm. See picture in the link bellow:

http://www.flickr.com/photos/28267220@N05/sets/72157627678462359/