Bicycle Mechanics - Changing gearing on old bike

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View Full Version : Changing gearing on old bike


milnerpt
08-03-08, 07:45 PM
So I promised a older friend I would try to help him out in order to get him back on his bike. He is complaining his gearing isnt wimpy enough for him. Its a trek from the 70's, so is got friction shifters and mostly some sort of suntour components, and is a 12 speed.

His current cassette is a 12-23, and 52/42 chainrings (I didnt double count... it may be 53/41 or something... and didnt see anything stamped)

There is a used bike parts store nearby. I was considering getting him a new cassette/freewheel group with a bigger cog, as well as some different chainrings (Id rather not try to swap cranksets/BBs)

I have no clue what that rear derailleur is, but as long as I keep the difference at 10 teeth (like a 49/39) would I be in the clear? Also, as long as I keep the cassette/freewheel difference from small to large, will that work out as well?

Obviously I may have to shorten the chain depending on all this...


Bill Kapaun
08-03-08, 11:02 PM
I would only swap one "end" at first and see how he likes it.
I'd probably look for a 14-28 FW. Let him try it out before deciding to take it a step further.

due ruote
08-04-08, 10:21 AM
I would only swap one "end" at first and see how he likes it.
I'd probably look for a 14-28 FW. Let him try it out before deciding to take it a step further.

Totally agree with this, with the caveat that you didn't mention what sort of terrain your friend is riding. Chainrings are expensive; a 14-28 freewheel is pretty cheap. Like this (http://www.nashbar.com/profile.cfm?category=600087&subcategory=60001109&brand=&sku=11695&storetype=&estoreid=&pagename=Shop%20by%20Subcat%3A%20Freewheels) one, for instance, which will likely shift much smoother than the old FW.

This link might also help you out: http://www.sheldonbrown.com/gears/


tellyho
08-04-08, 11:30 AM
52/42 is pretty standard for older doubles. I guess people had beefier quads back then. I agree with changing up the freewheel first. You can also add a cog - a 7 cog freewheel will fit on there just fine.

dit
08-04-08, 11:48 AM
I don't know how old your friend is or how hilly the rides will be but your friend sounds a lot like me and I know that the 28 rear cog was not enough for my old legs in these hills here in middle TN. I believe that shimano sells a 34 tooth 6 and 7 speed freewheel and I would recommed one of these. If he has the 126mm rear spacing go with the 7 speed 14-34 and I think he will be happy. The only problem might be the stock rd probably will not handle the amount of tooth difference so the rd may have to be replaced also.

too hot to ride here today.....almost 100 again today

ditz

milnerpt
08-04-08, 06:00 PM
Freewheels and chainrings are only 5 bucks a pop, so cost isnt a big deal. I wasnt sure if a 7 speed would fit on a 6, but Ill see what they have for 7 speeds.... its just a matter of time before I come across something useful. Id rather not have to fiddle with the RD. Maybe take a peek see if they have a 39 chainring in stock.

As for beefier quads, 52/42.... and this bike aint the lightest. Holy heck.

Bikewer
08-04-08, 08:26 PM
I concur. I've rebuilt a lot of these old roadsters, and either men were manlier back then or a lot smaller. They all seem overgeared to me....
A different cogset with a 28T low gear should help a lot.

due ruote
08-05-08, 08:42 AM
I concur. I've rebuilt a lot of these old roadsters, and either men were manlier back then or a lot smaller. They all seem overgeared to me....
A different cogset with a 28T low gear should help a lot.

It really depends on where you are riding. I'm a 50+ midwesterner and almost never ride anything lower than a 42 x 17. And I'm not that strong, believe me. On the other hand, a few months back I took a bike with me on a brief trip to TN. The bike had a 39 x 24 low and it was a humbling experience.

Bill Kapaun
08-05-08, 02:57 PM
52/42 is pretty standard for older doubles. I guess people had beefier quads back then. I agree with changing up the freewheel first. You can also add a cog - a 7 cog freewheel will fit on there just fine.

One must keep in mind that people were transitioning from single speed coaster brake bikes to a large extent. A 42-24 in a somewhat lighter bike was a relatively, major low gear! Instead of having to walk up every hill with your 50 lb. gas pipe bike, you could actually pedal up some of them.
I grew up in rather hilly country and pretty much quit riding when I was 13. IF I had a basic 15-21 speed bike, life would have been much easier.

dit
08-05-08, 05:19 PM
jbonamici (http://www.bikeforums.net/member.php?u=73948) vbmenu_register("postmenu_7208756", true); ......I moved from the slightly rolling mid-west to southern middle TN. I hadn't ridden in many years and dug out my 34/24 low gear road bike and found that I couldn't get up many of the hills on secondary roads which is where I prefer to ride. I just went to a triple with a 24 chain ring and still find some of the hills unrideable. When I get back into shape I should be able to ride them all but these old legs still say uncle on some hills. They sure are fun to go down though. I really liked my 14-24 5 speed freewheel on the flats but it sure doesn't cut it down here except for maybe Godzilla. hehehe