If a 650c tribike uses 53/39, why does.....
 

...the 650c Paramount Series 7 use 56/42?

I don't get it.

What does said tribike use in the back? Only goes down to 13 on the Paramount.

53 / 12 = 4.42
56 / 13 = 4.31
53 / 13 = 4.08

FWIW

53 * (622 / 571) = 57.73
39 * (622 / 571) = 42.48

...because peletons are faster?

American legs are stronger than European legs?

The tri-bike I tune uses 650c, 12-23 rear, and 53/39

The Paramount I'm building uses 650c, 13-23 rear, and 56/42, though I'll probably go 9-sp w/12-23 rear.

I'm tempted to offer the tri-girl racer my chainrings for her events. If it would aid her speed, I would.
She trains on a road bike with 53/39 and 11-24, but I've never seen her use the 11t.

I never really got the 650 tri bike thing. I don't know if once the air around the bike is moving if a 650 wheel is more aero than a 700c.

as for the gearing who knows! if I had to spec a 650 wheeled racing bike I would maybe a 44/56 to makeup for the smaller wheels.

Evidently the guy who spec'd out the Paramount Series 7 was thinking about optimal gearing, and the guy who spec'd out the other one was thinking about the relative costs of the chain rings.

Frankly I doubt there's enough difference between the two to make much difference to anyone.

The wheels are smaller in 650c so you need to gear a bike higher to get the same speed. I have a Bike Friday and to get the same gear range as my 1974 Paramount I need to use a 46-60 on the front and a 11-28 in the rear. Roger

Right, but the bikes Robbie mentioned both have the same wheel size, 650c.

650c seems small when you do a side-by-side comparison to 700c, but the difference seems negligible when you add a Bike Friday or a Moulton or Brompton (or any number of others) to the comparison.

Robbie, rhenning is correct.. I used to race a 650c tri bike, and I used a 55-42 with a 12-25 cassette. Because of the smaller wheels, you need larger gears to match the 'speed' of a regular 700c bike. Now that I think about it though, having a 53-39 on a 650c bike is almost like putting a compact crank on a 700c bike. You're in Florida and I recall you saying you rode a lot in the wind and on flat roads, so I'd go for the 56-42... If going somewhere hilly, just swap it out for a standard 53-39.

53-11 is still a mighty strong gear with a 650c wheel. Probably comparable to 52-14 on a 700c
Its to early to get out my calculator though.