Hammering on the classic.

Reply Subscribe

Thread Tools

Search this Thread

01-14-08 | 05:14 PM

#26

melville

Senior Member

Joined: Jul 2007

Posts: 529

Likes: 31

Quote:

Originally Posted by garysol1

The Bike:
1985ish Benotto/Columbus SL tubing
Campy SR deraileurs, 6 speed regina freewheel
Friction shifters.

Problem: When I put the hammer down the bike consistently down shifts, sometimes putting the chain between the cogs which makes for a very eye opening moment. What is going on here?
I have checked all the mechanicals. Dérailleurs have no play in them and shift perfectly. The levers are nice and tight. The freewheel has no play. Am I running into frame flex? Any other idea's on things I can check?
Assuming it is frame flex I guess there is not really much I can do or is there?

Do a search for "ghost shift" or "phantom shift". 90% of the time it's related to lubrication in the derailleur cable at the BB guide and in the rear turnaround casing. 8% of the time it's a problem with the keyed friction washer in the shifter not being keyed so much anymore. 1% of the time it's a cracked frame. 1% of the time you're just too big a gorilla to be riding that flexy thing without index or retrofriction levers. These are scientific numbers.

01-14-08 | 05:18 PM

#27

garysol1

Thread Starter

Senior Member

Joined: Apr 2005

Posts: 10,244

Likes: 17

From: Traverse City Michigan

Quote:

Originally Posted by melville

90% of the time it's related to lubrication in the derailleur cable at the BB guide and in the rear turnaround casing.

did that today. have yet to try it out

Quote:

Originally Posted by melville

8% of the time it's a problem with the keyed friction washer in the shifter not being keyed so much anymore.

Still feels nice and tight......

Quote:

Originally Posted by melville

1% of the time it's a cracked frame.

First thing I inspected

Quote:

Originally Posted by melville

1% of the time you're just too big a gorilla to be riding that flexy thing without index or retrofriction levers.

Hmmmmmmm

__________________
BMC Roadmachine
Kona Jake the Snake

01-14-08 | 05:30 PM

#28

repechage

Senior Member

Joined: Jun 2006

Posts: 21,825

Likes: 3,724

Quote:

Originally Posted by caloso

In my experience, a bent DR hanger causes poor ****ing in some gears, not all. So you can get it to sit perfectly on the top gears, but it won't shift correctly all the way across the range.

[edit] Apparently, if you misspell "shifting" the censorbot will get you!

"eyeballing" the hanger is not enough, beyond that, "crosschain" it, small ring/smallest cog, if it jumps, then chain/freewheel non compatible as said and or one is worn too much. If it does stay engaged in the sm/sm, then look at the other stuff memtioned. to test the middle cogs, a method is to lock in the gear, using the adjuster screws, no not ask the cable to do anything, if the problem comes back, your freewheel is now a fishing weight, spare cogs? wrong decade to look, unless you are especially lucky.

01-14-08 | 05:52 PM

#29

garysol1

Thread Starter

Senior Member

Joined: Apr 2005

Posts: 10,244

Likes: 17

From: Traverse City Michigan

Quote:

Originally Posted by repechage

Awesome trouble shooting guide ....Thank you Thank you. I have your post saved and will use it as soon as the roads clear again

__________________
BMC Roadmachine
Kona Jake the Snake

01-14-08 | 07:19 PM

#30

onetwentyeight

blah

Joined: Oct 2005

Posts: 5,573

Likes: 6

From: Oakland, CA

how worn are the pulleys?

01-14-08 | 07:48 PM

#31

garysol1

Thread Starter

Senior Member

Joined: Apr 2005

Posts: 10,244

Likes: 17

From: Traverse City Michigan

Quote:

Originally Posted by onetwentyeight

how worn are the pulleys?

like new. maybe 800 miles since new

__________________
BMC Roadmachine
Kona Jake the Snake

01-15-08 | 08:02 AM

#32

RK1963

Senior Member

Joined: Mar 2005

Posts: 580

Likes: 1

Quote:

Originally Posted by garysol1

Make that cable housing 2 1/2 inches longer.

01-15-08 | 08:04 AM

#33

RK1963

Senior Member

Joined: Mar 2005

Posts: 580

Likes: 1

Quote:

Originally Posted by RK1963

Make that cable housing 2 1/2 inches longer.

Also, I went from an SR RD just like yours to a late 90s campy chorus RD and noticed a huge improvement in shifting.

01-15-08 | 08:05 AM

#34

garysol1

Thread Starter

Senior Member

Joined: Apr 2005

Posts: 10,244

Likes: 17

From: Traverse City Michigan

Quote:

Originally Posted by RK1963

Make that cable housing 2 1/2 inches longer.

Are those metal housings still available? I really like the look of it.

__________________
BMC Roadmachine
Kona Jake the Snake

01-15-08 | 03:02 PM

#35

RK1963

Senior Member

Joined: Mar 2005

Posts: 580

Likes: 1

Quote:

Originally Posted by garysol1

Are those metal housings still available? I really like the look of it.

I'm speculating that if your RD cable were longer, from chain stay stop to entry into the RD, your shifting problems may resolve.

01-15-08 | 03:21 PM

#36

garysol1

Thread Starter

Senior Member

Joined: Apr 2005

Posts: 10,244

Likes: 17

From: Traverse City Michigan

Quote:

Originally Posted by RK1963

I'm speculating that if your RD cable were longer, from chain stay stop to entry into the RD, your shifting problems may resolve.

I am going to lengthen the cable and use a longer housing at the deraileur. Hopefully that will help along with all the lubing I have done.

__________________
BMC Roadmachine
Kona Jake the Snake

01-16-08 | 08:45 AM

#37

RK1963

Senior Member

Joined: Mar 2005

Posts: 580

Likes: 1

Quote:

Originally Posted by garysol1

I am going to lengthen the cable and use a longer housing at the deraileur. Hopefully that will help along with all the lubing I have done.

Let me know if that helps----once again, I believe it will

01-16-08 | 09:17 AM

#38

garysol1

Thread Starter

Senior Member

Joined: Apr 2005

Posts: 10,244

Likes: 17

From: Traverse City Michigan

Quote:

Originally Posted by RK1963

Let me know if that helps----once again, I believe it will

will do! Maybe a few weeks though before I can try it outside.

__________________
BMC Roadmachine
Kona Jake the Snake

01-16-08 | 03:33 PM

#39

bibliobob

Senior Member

Joined: Apr 2006

Posts: 3,231

Likes: 735

From: Sacramento, CA

Bikes: '64 Bianchi CDM, '62ish Altenburger Cinelli Mod B, '63-64 Cinelli SC, 69 Rene Herse Competition, '71 Gitane SC, '73 Cinelli SC, '73-74 Colnago Super,, '73-74 Cinelli SC, '78ish counterfeit Confente, '82 Medici Gran Turismo, '67ish Mondia Speciale

Disassemble, clean, and re-assemble your dt shifters. I thought that mine were tight as can be but, as it turns out, the pieces were somehow not perfectly flush and were allowing some slippage. It's easy to do, free, and will help rule out that problem.

01-16-08 | 03:49 PM

#40

tcpasley

Junior Member

Joined: Aug 2007

Posts: 166

Likes: 10

My old Uniglide 6spd freewheel is real sensitive to rear wheel/axle alignment. Sometimes she'll skip (in the 2 lower cogs) when I horse down on'er with all my 210+ lbs, and I can almost guarantee that the axle has slipped forward on the drive side. Not much, maybe 1 mm if that, but enough to fool those wonderful Uniglide twisted teeth.

tcpasley

02-04-08 | 04:41 PM

#41

garysol1

Thread Starter

Senior Member

Joined: Apr 2005

Posts: 10,244

Likes: 17

From: Traverse City Michigan

Took the old girl out for a 40 mile ride yesterday and did not have a single issue....YOOHOO!!!!
I took the advice to make sure the cable was clean and lubed especially below the bottom bracket. I did that as well as clean the chain and freewheel and lube it up real good. Thanks for the help guys.

__________________
BMC Roadmachine
Kona Jake the Snake