jalopanista!

I live in an area where having a lower gear option on my Panasonic DX-5000 would be nice. Currently, it has a 53t and 42t pair of BioPace chainrings on it and I'm thinking a drop to 48/38/28 or 48/36/26 would make rides on the Blue Ridge Pkwy (near my house) much more pleasant. I'm assuming I'll need to swap out the current Shimano 600 front (FD-6207) and rear derailleurs as well as the bottom bracket. Any suggestions for those?

I was originally going to replace the BioPace rings and add a triplizer, but it doesn't make sense pricewise, when I can get a Sugino triple ring set for ~ $100. Of course, I was hoping to just replace the rings/crank/bottom bracket and not have to fiddle with the derailleurs, but I have since been disabused of that notion by others who've pointed out that the 600 derailleur probably won't have the range I'll need with a triple and the rear derailleur won't pick up enough slack. Thoughts?

Thanks for ANY input,

js

T-Mar

To be sure, we would need to know the part numbers of your derailleurs (stamped on the back) and the cog range on the freewheel/cassette. I suspect they are 6207 or 6208 derailleurs. Most 600 rear derailleurs had an optional long cage version (GS suffix) that handled about 34T maximum cog and wrap. The spec'd capacity for most of the 600 front derailleurs was around 18T. These are usually conservatively rated, so you could probably push it to 20T but maybe not 22T.

jalopanista!

Thanks for the reply T-Mar. You're correct; the front derailleur is a 6207 and the rear is a 6208. No GX suffix with the latter, unfortunately.

What would would work and be appropriate for a bike of this age?

thanks,

js

T-Mar

Well, we still need to know the number and size of cogs you're running the rear. I presume it's 6 speed? The 6307 front derailleur had a spec capacity of 18T. A standard 6208 rear derailleur had a 28T capacity.

As previously stated, the derailleur capacities are usually conservatively rated (to ensure proper operation uner all conditions), so can can proabably push it to 20T for the 48/38/28T combination. However, the rear will have to be switched unless you are very careful with your gear selection to avoid combinations where the chain will be too short or long.

Another thing to keep in my, is that the rear derailleur needs to be 6 speed, SIS compatible, unless you are willing change the shifters and cogs.

John E

How about something like 46-38-30 in front? This wouldn't be much harder on your rear derailleur than today's ubiquitous 53-39 combination.

jalopanista!

I just checked the rear cogs and they're 13T through 21T, and yes, it's a six-speed. I'd much prefer keeping the shifters and cogs for cost considerations. Actually, I'm going to move the downtube shifters to the bar ends.

If I'm going to replace the derailleurs, what would work and be somewhat "correct" for a mid-to-late '80s Japanese bike? I'm not completely hung up on that, but it would be nice.

js

jalopanista!

I'll definitely keep that option in mind. I'd also thought about going with a compact double arrangement, but I really want something smaller than a 39T...so triple it is.

thanks,

js

pastorbobnlnh 

Here's another option: I believe your RD can handle up to a 28 tooth rear cog. Go to a different freewheel and try a couple of smaller rings, say 48-36. The trick is to shorten the chain enough to make the jump to the small front, big back. I triplized my '79 Schwinn (made by Bridgestone) and went with different vintage Shimano 600 derailleurs. The fancy original long cage RD and a later generation FD (with the mountain goat head). By pure dumb luck I didn't need to change the BB. I have a 6 speed 15-34 Uniglide hub, and 50-40-32 triple chainrings. Getting the chain length right took a few tries. Sorry I don't have better pictures.

jalopanista!

Bob,

Thanks for the suggestion - I'm still torn over various options and this is definitely one I'll keep in the mix.

Your pictures are great, btw. How can you not like a bike with themed panniers!

js

T-Mar

That's only an 8T spread on the back, so if you use the 48/36/28T combo with a 20T spread, your present rear derailleur should handle it, as it has a spec'd 28T chain warap capacity. Again, these specs are often conservative, You may even be able to run the 48/38/26T with the rear derailleur.