slebo3213

I've got a set of 7700 hubs with an 8 speed (11-23) cassette that I'm using with a 7400 8 speed rear dérailleur and 7400 levers. The problem is getting into the lowest gear. If I tighten the barrel adjuster enough to get onto the largest cog than the chain doesn't sit right on the two adjacent gears. If I loosen the cable so that it moves through the lower gears properly, I can't get the chain over the largest cog. Seems like a spacing issue, right? I just spent an hour making adjustments but can't get it to work. Any suggestions?

bradtx

slebo3213, The 7400 RD has a unique pull ratio. It requires a 9S shifter to work. You can try using the RD's B position at the cable clamping screw (clamp onto the wrong side) to see if that will work.

Brad

Kimmo 

Try routing the cable like this:



If it was the other way round and you had old Dura Ace shifters with a new derailer, you'd do this:

slebo3213

Thanks. I should mention that I had this setup before, with the same cassette, on the 7400 hubs that came with the bike. It worked fine and with the cable in position A. Which is odd because the description makes it sound like it should be in position B. I tried both last night and in position BI couldn't get it passed the 3rd smallest gear. Besides, wouldn't a pull ratio issue cause problems across all of the gears? The 7 smallest shift fine in my current setup.

slebo3213

Thanks. I did try this and didn't have much luck. See prior post.

shoota 

Generally I would say the barrel adjuster is not for making large changes in shifting. If the standard installation and adjustment prodecure doesn't work (i.e. set limit screws, affix cable with appropriate tension) then something isn't quite right.

FastJake

Alternate cable routing should not be the solution. OP is using 7400 shifters with 7400 RD and an 8-speed cassette. Everything should be 100% compatible.

I've had this issue before, and I've been able to cure it with very careful adjustment of the low limit screw. The way the chain shifts into the lowest (and highest) gears depends on those screws. If you still can't get it right, take the cassette off and sand down the plastic spacer between the lowest gear and the next one to change the spacing just a bit. But this shouldn't be necessary.

slebo3213

Ok. Do you suggest I tighten the barrell adjuster so that I can get the chain onto the largest cog and adjust from there? Or, loosen the adjuster so that I get through the 7 higher gears and start from there? As I type I guess the first approach would be best.

bradtx

slebo3213, I misread the OP. For some reason I registered 6400, rather than 7400, levers. Sorry.

I'm using 7700 hubs with 8S 6400 everything else and I have zero problems, so the issue isn't which hub the RD is shifting across. This is a very good tutorial: Park Tool Co. ť ParkTool Blog ť Rear Derailler Adjustments (derailleur) .

Brad

70sSanO

I didn't see anyone ask, but are the 7400 shifters 8 speed? I have 7401 shifters that are 7 speed. Do you have a definite click when shifting to the largest cog? If you have 7 speed shifters you will have a tough time getting everything to work. Technically you can take the cassette apart and re-space a couple difficult cogs but that is another discussion. (Edit Added: Although I haven't done this, I think you can re-space with 3.15mm spacers (7 speed) and still fit on the hub. Sheldon Brown's crib sheet shows 8 speed cassette as 35.4mm overall width and 9 speed at 36.5mm overall width so you have 1.1mm to work.)

I think, and don't want to research it, that 7400 were 6 speed, 7401 were 7 speed, and 7402 were 8 speed.

You hubs will not have any impact on the shifting. My current 7 speed setup consists of Superbe Pro hubs, Sachs freewheel, DA 7 Speed shifters, and an XTR 910 RD. If I can get that to work there is no way you can't get DA RD and shifters to work.

John

slebo3213

Thanks. They're 7402 shifters and they worked fine on the setup when the same 8 speed cassette was on the 7400 hubs that came with the bike. The problem started when I swapped the cassette onto some 7700 hubs that I picked up recently.

Slash5

Did you try loosening your limit screws to make sure they are not the problem? Is the problem that it won't shift onto the large cog or it doesn't run properly on it?

slebo3213

Yes. When I engage the shifter the chain will seat on the largest cog. When I release the shifter it will jump back down to the next smaller cog.

FastJake

I get the cable tension set so that it shifts the middle cogs the best. Then work on the low limit screw to get into the lowest gear. Adjust cable tension a little if necessary, but you really shouldn't have to do much at that point.