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60 Tooth Grin!
I successfully added a 60-tooth chainring to my 1989 Dahon Getaway V. (Pics below) With the previous upgrades (https://www.bikeforums.net/folding-b...ect-s-end.html) to a 13-28 in the back I now have gear inches from 36 to 77...just high enough to commute practically. I still may try to add an 11-28 again to raise my high-end, but for now this seems sufficient...and the less than inspiring bike dynamics don't inspire high-speed confidence, although adding a front-brake to complement the original rear band brake sure helped.
I had unsuccessfully tried to install a bottom bracket adapter in order to use a more modern crank to fit a larger cog, but the Dahon "classic" 16-inch frame has the seat-tube pass through the bottom bracket. There's plenty of clearance for an old-style one-piece crank/arm spindle (think classic Schwinn) but the thinnest sealed-tube bearing didn't fit and I didn't have experience with external-bearing cranks, and didn't know if they would work. What did work was an old-style single-chain ring to 110/130 BCD adapter, $30 from Origin8 primarily used for upgrading old BMX bikes. I didn't know these existed at the start of my project, or I would have started with one. On the other hand tremoving the original bearings, braces and cups allowed be to clean and re-grease them. In fact, had I purchased a 110 BCD ring I could have got a spider-style adapter. I was worried about losing low-gearing, which is needed here in Colorado Springs...especially since the lowest gear, 28T was unusable due to the extreme chain angles owing to the short chainstays which cause the chain to slip off the original 52-tooth cog on whichever gear I adjusted to be furthest from center. I had to pick low or high, and I picked high. HOWEVER, with the new 60-tooth cog and a new chain all 6 gears are usable, so I still have a low-enough gear for the steeper hills. I know part of the problem was the flexibility of the original 52-tooth steel cog...I could see it bend. The new set-up is much stiffer and does not bend. Next I will see if I can get rid of the rear-wheel offset I needed to allow the chain to work with the old, flexible, 52-tooth chainring. I will note that with the 60-tooth ring in front, and the low-end 28-tooth gear in the rear, there is very minimal clearance between the chain and the frame's chain-stay...but it clears! I almost abandoned this project and thought about going with a used Citizen Tokyo, or an inexpensive Brompton-style tri-fold. But since I already have a wonderful modified 20-inch Dahon Boardwalk this project was to be a low-budget attempt at a folder that is significantly smaller when folded, and this thing is tiny...heavy, but small. There will be more upgrades in the future, but the bike is now a practical commuter. I see fenders and possibly a rack in the future, as well as folding pedals, lighter wheels, and a caliper brake in the rear. I would love bull-bars like my Boardwalk, but I'm not sure of how the Getaway would fold with them. I know it's a kludge, but at 62, I realized that for me, the satisfaction of rescuing an old bike and not only making it ride-able again, but upgrading its performance is sometimes more satisfying than buying something off the shelf I mainly wanted to share the info that single-chain ring to BCD ring adapters exist and allow for the original bottom bracket and crank to be used, since on the smaller Dahon classic frames the seat-tubes pass through the bottom bracket which won't allow for most internal crank adapters without grinding which might compromise an old frame, and also prohibit a seat tube from extending down below the crank. Here are some pics: https://cimg1.ibsrv.net/gimg/bikefor...fcbd9d379d.jpg https://cimg0.ibsrv.net/gimg/bikefor...e5cda0b067.jpg https://cimg2.ibsrv.net/gimg/bikefor...7fb4972b9c.jpg https://cimg7.ibsrv.net/gimg/bikefor...5fd13dda37.jpg https://cimg8.ibsrv.net/gimg/bikefor...cab0a8a702.jpg https://cimg9.ibsrv.net/gimg/bikefor...a50c4a8f7d.jpg |
Originally Posted by BobbyG
(Post 23173787)
I successfully added a 60-tooth chainring to my 1989 Dahon Getaway V. (Pics below) With the previous upgrades (https://www.bikeforums.net/folding-b...ect-s-end.html) to a 13-28 in the back I now have gear inches from 36 to 77...just high enough to commute practically. I still may try to add an 11-28 again to raise my high-end, but for now this seems sufficient...and the less than inspiring bike dynamics don't inspire high-speed confidence, although adding a front-brake to complement the original rear band brake sure helped.
I had unsuccessfully tried to install a bottom bracket adapter in order to use a more modern crank to fit a larger cog, but the Dahon "classic" 16-inch frame has the seat-tube pass through the bottom bracket. There's plenty of clearance for an old-style one-piece crank/arm spindle (think classic Schwinn) but the thinnest sealed-tube bearing didn't fit and I didn't have experience with external-bearing cranks, and didn't know if they would work. What did work was an old-style single-chain ring to 110/130 BCD adapter, $30 from Origin8 primarily used for upgrading old BMX bikes. I didn't know these existed at the start of my project, or I would have started with one. On the other hand tremoving the original bearings, braces and cups allowed be to clean and re-grease them. In fact, had I purchased a 110 BCD ring I could have got a spider-style adapter. I was worried about losing low-gearing, which is needed here in Colorado Springs...especially since the lowest gear, 28T was unusable due to the extreme chain angles owing to the short chainstays which cause the chain to slip off the original 52-tooth cog on whichever gear I adjusted to be furthest from center. I had to pick low or high, and I picked high. HOWEVER, with the new 60-tooth cog and a new chain all 6 gears are usable, so I still have a low-enough gear for the steeper hills. I know part of the problem was the flexibility of the original 52-tooth steel cog...I could see it bend. The new set-up is much stiffer and does not bend. Next I will see if I can get rid of the rear-wheel offset I needed to allow the chain to work with the old, flexible, 52-tooth chainring. I will note that with the 60-tooth ring in front, and the low-end 28-tooth gear in the rear, there is very minimal clearance between the chain and the frame's chain-stay...but it clears! I almost abandoned this project and thought about going with a used Citizen Tokyo, or an inexpensive Brompton-style tri-fold. But since I already have a wonderful modified 20-inch Dahon Boardwalk this project was to be a low-budget attempt at a folder that is significantly smaller when folded, and this thing is tiny...heavy, but small. There will be more upgrades in the future, but the bike is now a practical commuter. I see fenders and possibly a rack in the future, as well as folding pedals, lighter wheels, and a caliper brake in the rear. I would love bull-bars like my Boardwalk, but I'm not sure of how the Getaway would fold with them. I know it's a kludge, but at 62, I realized that for me, the satisfaction of rescuing an old bike and not only making it ride-able again, but upgrading its performance is sometimes more satisfying than buying something off the shelf I mainly wanted to share the info that single-chain ring to BCD ring adapters exist and allow for the original bottom bracket and crank to be used, since on the smaller Dahon classic frames the seat-tubes pass through the bottom bracket which won't allow for most internal crank adapters without grinding which might compromise an old frame, and also prohibit a seat tube from extending down below the crank. Here are some pics: https://cimg0.ibsrv.net/gimg/bikefor...e5cda0b067.jpg https://cimg7.ibsrv.net/gimg/bikefor...5fd13dda37.jpg Your tire seems... tired! FYI, the Ti Parts Workshop JIS squqre taper bottom bracket for Brompton has no tube, it might fit for your bike. |
Originally Posted by Jipe
(Post 23173916)
Your tire seems... tired!
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