GordoTrek

ok so i have an 82 trek 412, it fits me perfect... its currently set up as a 12spd, 6 spd freewheel in the back , i love riding it, but it doesn't have the gear range that im going to need for this ride (tour de cure 100k), i tried doing my normal training ride hills, and i stalled out...i did the same ride last year on my trek 930 converted to a hybrid and did just fine with a triple and megarange 8spd
im starting to get worried about not having enough, the thing is, i have a complete shimano arabesque group, the freewheel is 13-24, i want to keep it complete , but damn that may be too much of a sacrifice...i can get a 13-34 shimano 600 .. im thinkin that might work.. any thoughts are appreciated..

JAG410

When doing a century, no one will be criticizing your bike's lack of period correctness or gear ratio. Get a new freewheel and chain and ride it. Swap the old freewheel and chain on when you don't need the lower gear.

wintermute

Is your RD long cage or short cage? If it's long cage, 13-34 should be no problem. If it's short cage you can go up to 28 teeth in the rear, which should still be alot better than your current "go fast" setup. Those are probably the cheapest/easiest remedies.

ThermionicScott 

What are the chainrings? If they're 52/42, you can get some relief by swapping to a 38T inner ring (Sugino and others make one.) Arabesque short-cage RD can handle a 28T cog, so I'd swap to a 14-28T freewheel. That'll get your low gear into the mid-30's, instead of the mid-40's where I imagine you are now.

Barrettscv 

I suggest you upgrade your equipment to a seven speed freewheel with a wide range. You will need to convert to a long cage rear derailleur and a wide range freewheel and you will need a new chain. Shimano makes a seven speed 14 - 16 - 18 - 20 - 22 - 24 - 34 "Megarange" freewheel FW723 with close spacing in the 14 to 24 range and a 34t cog for the very steep climbs.

The Shimano Deore RD-M735 is a great derailleur with plenty of range and cog capacity;

bradtx

GordoTrek, Switching to a 39T inner chainring, if you currently have a 42T, won't gain much, but maybe enough. The 13-34 will lower gearing very noticeably, but I'd change chains and the RD for this FW, just to be on the safe side. There are no style points on a century and the knowledgeable cyclists will understand without comment.

Brad

GordoTrek

forgot to mention i have a 39/52 in the front, im thinking 12/28 for the rear,

i think i found a nice long cage rear..

old's'cool

My favorite period correct gearing upgrade for 5 & 6 speed bikes is a triple front, set up as half-step plus granny. I use 48 or 49T middle chainrings, a 52T outer, and 36T inner. I'm just not that fond of so-called alpine gearing, as switching between low and high range can be a nuisance. With a half-step setup, worst case is you're a half-step from where you'd want to be ideally, not counting the granny (which in my case at least, is used very rarely).
I've been able to score vintage triple cranks at reasonable prices when needed, by watching Ebay diligently. xxcycle.com is an excellent source for chainrings of any desired tooth count in all the popular BCD sizes, at very reasonable prices, shipping included.

GordoTrek

thanks for all the input,

i bought a cheapy 6spd 13-34 freewheel, i have a brand new chain on this bike so the switch won't hurt, i also have a long cage suntour cyclone on loan from the coop, ill use that one for the ride,.. at least it still period correct!

old's'cool

That's a pretty nice RD to be loaned out! You should find out what they want in exchange so you can keep it outright...

GordoTrek

funny story with that, they got in a Trek 7xx at the coop not sure of the year, but full cyclone group, its missing the front brake, but everything is there, the frame was trashed and they were just going to take the wheels and bail on it,
i almost knocked people over to grab it, i told them i would clean up the components and bring em back...