Stronglight crank mystery

[bargainguy]

Today I picked up a project - an early 70's Raleigh Super Course, Nervex lugs, some parts and wheels but no fork, and a Brooks saddle.

The crank is Stronglight, but I haven't seen this configuration before - 49t & 52t rings.

I'm no stranger to half-step plus granny gearing, but I'm wondering why anyone would set up this way, or even if it will work - not much chain clearance between rings.

Any ideas?

[Ralph]

My very first Schwinn Paramount....a painted (not all chrome) P13 race bike (not a P10 or P15 touring model)...around 73 or 74, came with a 14-16-18-21-24 rear freewheel and a 49-52 Campy crank in front. I believe a 42-52 was an option, or maybe that came along a little later in the 70's. The 49-52 was common in the era, and shifted fine with the right FD....one where the inner cage was high enough not to get in the way. My bike had the standard NR FD.

[christian]

Vintage Florida time trial series? :)

[Ralph]

Vintage Florida time trial series? :)

It worked. 3 teeth difference in front allowed one to get between the two teeth difference cogs in rear. But I also remember using a 14-15-16-17-19 freewheel and 42-52 around then. Even today....with 10 in back....still like a 42-52 around here.

[witcombusa]

That is classic half-step gearing. With the proper rear (5sd in this case) freewheel, you get a full "step" shift in the back and half the difference with a front shift. You get the progression of a corn cob freewheel with a greater total range. Also the 3 (or 4) tooth shift up front is usually seamless even with period derailers.

You also saw the 3-4 tooth front chainrings on earlier bikes, late 50's and 60's, when they thought chainline was everything. So you would use the inner front with the 3 larger rear cogs and then the outer with the 3 smallest (middle cog overlap).

Enjoy the period gearing and go for a ride! :banana:

[bargainguy]

Wow, I had no clue 49/52 was commonplace at one time. Thanks to all!

[jemoryl]

Yeah, I remember seeing those and thinking 'why bother?'

[witcombusa]

Yeah, I remember seeing those and thinking 'why bother?'

Because it works quite well. For example (and rounded off), a 49/52 with a 14, 16, 18, 21, 24 freewheel gives you the following gear inch progression;


55, 59, 63, 67, 74, 78, 83, 88, 95, 100

Not bad in 1970. Ten useful gears, no overlaps or duplicates. :banana:

[Mark McM]

Because it works quite well. For example (and rounded off), a 49/52 with a 14, 16, 18, 21, 24 freewheel gives you the following gear inch progression;


55, 59, 63, 67, 74, 78, 83, 88, 95, 100

Not bad in 1970. Ten useful gears, no overlaps or duplicates. :banana:

Otherwise known half-step gearing. The relative size difference between chainrings was only half the relative difference between sprockets. Thus, shifting the front gave you a "half step" difference in gearing, while shifting the rear gave you a "full step" difference in gearing.

This gearing system was more popular when there were far fewer sprockets in the rear cluster, so a wide ranging rear cluster would of necessity have very large gear size steps between sprockets. While it provided more useful gears with small steps between them and without overlaps and duplicates, the downside is that it required far more front shifting, and often that both derailleurs be shifted at the same time to reach the next larger/smaller gear.