86 SR500 Project is Moving into the Strip and Repaint Stage

[wild]

QUOTE="black lightning 1987, post: 3279, member: 971"]I think the old Shimano RDs were rated for a 24 T cog, but they were rated conservatively to allow for differences in dropout and hanger dimensions. 28 large cog may work fine. Be sure to check your chain length. You don't want to find out that the 28 has stretched the chain too far when you are grabbing for lower gears on a hill.[/QUOTE]
I was wondering about chain length with the new freewheel. The existing one is a 11-22T. I do have some extra chain and links if needed. My MTB is all Shimano, and I looked at swapping components yesterday. The freewheel is 12-26, but that derailleur is just plain ugly. I'm hoping the 6400 will work. It will be next week before I find out so I'll get back with info.
Here is that old beater MTB that got me started. The seat is worth more than the bike! LOL

 

[black lightning 1987]

My guess is that you will need a longer chain. You can get an idea based on what the current chain length is. Put it in the big ring and carefully shift to the larger cogs. If you haven't ridden big ring/big cog combination yet, be cautious when shifting to it as your chain could be too short now. If it goes into that combination, check to see how much RD cage travel is left. If it's close to full extension you're going to have to add an equal amount of chain to the number of teeth you are adding to the freewheel.

 

[wild]

I appreciate that info. I'll go ahead and add 6 links since the derailleur is pretty tight now. Apparently, based on the amount of surface rust on the large cog (22T), this wasn't shifting well before I got the bike. The front derailleur doesn't move all the way into the small cog(42) either, even without the cable attached and the stop screw backed all of the way out. I have to agree that the brazed on system is not as friendly as a clamp would be in my case. I finally gave up today and removed the front derailleur so I could relieve the contact area that was stopping the movement. That fixed it so that it shifts, but I think a new one will be in order soon.

 

[black lightning 1987]

I can't imagine why a front derailleur wouldn't shift between two rings without issues if set up properly. What model is it? Only issue that comes to mind is a bottom bracket spindle that's too long for the crank. Picture of chainring clearance to chain stay should answer that question.

 

[wild]

I can't imagine why a front derailleur wouldn't shift between two rings without issues if set up properly. What model is it? Only issue that comes to mind is a bottom bracket spindle that's too long for the crank. Picture of chainring clearance to chain stay should answer that question.

The spindle is the same as the one that I removed, 108 mm Shimano. The derailleur (Shimano 600 tricolor) showed a wear pattern where the cage had been hitting the mechanism in low for some time. I used a high speed grinder to remove about a 1/16" from the top of the cage, and gained enough movement to get the chain to shift over. There is a small adjustment up and down on the mount to raise the height of the derailleur, and the inboard screw is not touching the stop in that position.

I'm thinking that the rear derailleur might be the main problem as it seems to be sensitive to the chain position on the front ring. If the front is on the small ring, it won't shift to the small cog, and if on the high ring, it won't shift to the large cog. This isn't necessarily bad since it won't cross chain easily, but if that rear is not on the large cog, the front will not shift to the small ring, and vice versa. As of last night it was working, so I'm on my way out for another ride to see if it works properly.

 

[wild]

The old girl performed flawlessly on the ride this morning. Full range shifting both front and rear. Tomorrow, I am going to install the new freewheel, and see if the rear derailleur has the reach to get into the 28T cog. BTW, I know this isn't much of a milestone, but I hit 19 mph on the flat today, a personal best so far. Some young fellows might snicker at that, but they aren't 72 y.o. yet. LOL

 

[black lightning 1987]

Glad to hear it's working well.

 

[wild]

Glad to hear it's working well.

I installed the 14-28 freewheel and added six links of chain as you suggested. It is a totally different ride now! I start and stay on the big ring, and don't use the large cogs on the freewheel. This has made my morning ride a lot smoother and more enjoyable. I wish there were hills close by where I could ride and not get run over. Traffic is a mess here. Thanks for the help.

 

[black lightning 1987]

Too many neighbors definitely makes the bike riding less enjoyable. I can ride 10% grades here and never meet or get passed by a car. Glad to hear that the gear change helped.

 

[wild]

Well, today was another milestone reached. Around our neighborhood there is a circle that is exactly 1 mile around. It is mildly up hill broken by stretches of flat, then downhill, and back uphill to the house. The best that I could get speed wise before I changed to the 14-28 freewheel was 19mph on a short flat run. Today I hit 21 mph while trying for 20. Around here, I don't use the 42T ring with the new freewheel, just the 52T and sprockets 3 through 7. Here is a picture of the shifters, but I have found some better ones that I'm using on my MTB in its refurbish.

 

[black lightning 1987]

Sounds like the changes are working out. Glad to hear that you are happy with it.