|Help revive Frankenstein drivetrain||simstress|
Jan 30, 2002 12:13 PM
|I need some help on behalf of my brother's bike-- an entry-level Bianchi circa 1993. The drivetrain currently consists of the following:
- Suntour friction downtube shifters
- Suntour front derailleur
- Sake double crankset (52/40 I think)
- Campy 7-speed rear derailleur
- Campy rear hub
- Campy 8-speed cassette (I haven't counted teeth)
- Sachs chain
The Campy components are not original, and I'm not sure what gruppo they're from, probably Veloce or Mirage. All cables were replaced last year.
My brother says he can't shift onto the 3 largest cogs. This is a big issue since he moved from flat coastland to the hill country. What could be the problem? He's not too bad with a wrench, but he's just not sure if it's a matter of outright incompatibility or merely poor adjustment. I think we can spend up to $150 to resolve this issue; any more than that would probably not be worthwhile.
I also have a wheelset I can give him, but it has a 105 9-speed cassette. (I suppose I could swap the cassette, but the hub would remain Shimano. These wheels are not rebuild-worthy.) He would be willing to change the drivetrain to Shimano if it could be done within budget.
If you've gotten this far, thanks for reading! Though we will probably take it to LBS this weekend for their assessment, I'd like to hear how you might handle this problem because this is a chance for me to learn too. Please help; I don't want him to have to walk all the hills around here!
|Things to check...||Andy M-S|
Jan 30, 2002 2:56 PM
|Do the limit screws allow the derailer to move far enough inward? Is the cable tension high enough (when the shifter is set for the smallest cog, the cable shouldn't be slack--there should still be a little tension there)? Is the chain long enough--that is, if these are huge cogs, it may not be possible to shift onto them if the chain is too short. Is the chainline reasonable? If not, you may need to shim the bottom bracket to get the correct lineup. And--finally--are the cables in decent shape? If not, swap in some new stainless cables (a $5 investment) and see if that improves matters.
$150 is a lot of money. First see if you can fix the bike so it works--if you're successful, then go spend $80 on a used set of 8-speed Ergo levers and an 8-speed Campy rear derailer. This will make your brother happy.
|Andy nailed it. If it worked before...||cory|
Jan 30, 2002 4:07 PM
|...it should work now. If somebody just threw on some odd parts out of the parts bin to make a complete bike to sell, then you might have trouble.
At a guess, the cable tension is a likely candidate. The cable might have slipped from the anchor bolt (it shouldn't stretch that far). One possible first step is to disconnect the shift cable and chain from the rear derailleur and swing it by hand to see if it covers the whole cassette. Set the limit screws so it does, then reattach the cable as Andy described. I'd be semi-surprised if that doesn't solve your major problem.
|re: Help revive Frankenstein drivetrain||scottfree|
Jan 31, 2002 5:53 AM
|My first thought was chain length. Has it ever been broken and put back together minus a link or two or three?|
|Two possibilities||nee Spoke Wrench|
Jan 31, 2002 7:03 AM
|First, I'd look at the bike from the back. The derailleur cage should hang straight down. If it's canted toward the inside, as normally happens when it gets bent, the cage will hit the spokes before it will shift onto the biggest rear cogs. With friction shifters you can probably align it adequately by eyeball. If it's an aluminum frame, ask yourself this: "Can I ride it the way it is?" If your answer is "no" try to bend it back and see what happens. Most often you can fix it and if it breaks off, it was an unrideable bike anyway.
Second, I've worked on more than one bike that some guy found a loose limit screw in the rear derailleur and tightened it. I even had a mom ask me if her son't bike was a lemon because, after the neighbor boy fixed it, it wouldn't shift at all!