Branimir

The bike is linked in my signature.

I have changed the wheels, that is, I had Shimano 600 - 6 speed rearwheel, and put an Ultegra 8 speed wheel, downtube shifter is in friction mode, and the rear derailer is set up to work with all 8 cogs, no problem.

I haven't changed the chain! There is space between the chain and the next cog and I cannot hear any buzz or crackling when pedalling, so it seems the previous chain works with the 8 speed cassette.

Here's the problem:

I usually use two gears for flat terrain, 42-17 and 52-17 when the cadence gets too high on 42T front. I like to "dig in" at some times, that is - to put all my weight on the pedals and use maximum power that I have in my legs to accelerate - something like sprinting. Usually when I put that kind of stress on the drive, the sort of chips and skips to the smaller rear cog next to the one I was before. It seems like I'm flexing the frame and the derailer wire in that process gets looser a bit and because of that the derailer shifts to the smaller cog. I think my frame is Columbus Aelle or Gara. I did fell, and the top and downtube were straightened, could that compromise the stiffness? I love my bike, but it's frustrating, sometimes I feel I'm riding a chewing gum, and I'm no pro by all means!

Are Columbus SL or SLX stiffer? I don't want to go for an another CV road bike frame and to sense the same flexing when pushing really hard.

Any ideas? Maybe to use a proper 8 speed chain would help?

Chombi

I don't think your problem is coming from too much frame flex as Aelle tubing should be quite stiff as I think it comes in thicker guages than most higher line tubing and maybe even unbutted/straight gauge(?). I don't think you can eliminate flex on any frame 100%. they will all flex to some extent when as you say, "dig in" or mash on the pedals. I would check the shifters on your bike if they are not maintaining friction/tension and getting bumped down a gear by any little bit of flexing on the frame. Also, check all your derailleur cable guides and casings to see if there are any areas that might need some lubrication if there is any excessive binding or friction. All those things can cause wht's called "ghost shifting" as you are experiencing.

Branimir

Yes, I had downtube shifter problems, put some loctite and tightened and now it doesn't unscrew, but I can see the lever changing position after the "hard" pedal power is used. So maybe my downtube shifter horror is continuing... Old bike, old problems... Heh.

I'm thinking of putting back the 6 speed rear wheel to check if the problem occurs with it.

Road Fan

The usual fix is to crank down on the bolt that goes through the center of the right friction shift lever, combined with considering learning to pedal smoother. The friction at that point holds the bike in gear. It's not designed for loctite. The trade-off is concern about stripping the bolt or the hole in the frame. At least the ones with the little handles on the screw are intended to be tightened with hand strength without the leverage of a wrench. I don't know how your loctite has affected that. Some of the early Campy ones (Valentino or Gran Sport) have heads for flat screwdriver, so you have to be more cautious with them.

The number of rear sprockets should not matter, to my mind. You need to stop the cable from slipping as the bike flexes. Another possible issue is making sure the cable path is clean and cable friction is minimized. Under or near the BB shell I would be concerned about this.

Branimir

I used Loctite because:
https://www.bikeforums.net/showthread...ror?highlight=

I cannot remember if I experienced the "ghost" shifting with the 6 speed cassette (more space between cogs, so could be less noticable).

Smooth pedaling is of course how I drive most of the time, but sometimes I need a quick start/acceleration, or just smash the hell out of the cranks to go faster uphill, so the bicycle kinda loses it's purpose if it's driven - mildly. I mean, if those guys in the 70s and 80s would ride this bikes with power, why can't I use it in that way from time to time?

T-Mar

The alloy of a steel has neglible effect on it's rigidity. Conseqently, for standard tubing, the primary affecting it's rigidity is the wall thickness. Aelle and Gara have the same wall thickness, to their rigidity should be the same. They're 0.1mm thinner than the butted end of SL in the down tube but 0.2mm thicker in the chainstays, so it overall they should be slightly more rigid, than SL. The ribbing in SLX had extra stiffness but I'm not sure if it would bring it up to Aelle/Gara standards.

There could be several issues at play. The levers, the old chain, cable issues or a bad cog. First thing I'd do is try it in different cogs. If it only happens in one then it's the cog itself. The switch back to the old wheel. if it disappears, it's the chain. It is probably too wide and the hard exertions cause just enough movement for it to catch on the next cog.

repechage

I agree on this and on one bike I bought from a CR member no less, the chain and freewheel were gone. New components did not fully fix it, so the balance of the problem was worn out jockey wheels.
I have out of this really unique chain whips made from Regina Record Oro chain though.
On my freewheels the one to watch wear wise is the 17 t 42 x 17 is such a nice happy gear to spin in.

Branimir

Update:

Took my bike inside to inspect it, and the first thing I saw was that the rear wheel was not in the center. I use dropout screws to fixate the rear wheel and seems I pushed them too far towards the edge of the dropout, and the left one was not same length as the right one, it was screwed more than the right one so it seems that when I first applied alot of pressure, the rear wheel "aligned" next to the screws - that is - left the center and therefor made possible for chain to skip the rear cogs when using a lot of power, since the rear cassette in this way - was not parallel with the front cogs. I did remove the chain and cleaned it, just for the sake of doing something to dirty my hands. Aligned the rear wheel a bit deeper in the dropout and made sure the dropout screws are now the same length. Also I tightened the right down tube shifter a bit, just to be sure.

Tried sprinting on my way back from work a minute ago, and did not experience "ghost shifting", and I did not notice the derailer move at all, so it seems I fixed the problem, and blamed the bike for my error!

Though I will definitely get a new chain in a couple of months, I'm using the old one from the 6 speed cassette, it works and doesn't scratches the adjacent bigger cog, but just to be on the safe side of having the right stuff on the bike.

Hope to do a local mountain climb on sunday, there I will use more power than usually commuting, so I'll know if the ghost shifting problem is definitely fixed.

Road Fan

Ok, fine, somebody here suggested Loctite, but the screw should really hold itself and remain adjustable for a long time. I see now you're also using a shifter set that (if I read right) has a broken bit in it. If you are dedicated to friction for this bike just get a replacement set of shifters.

Good catch on the wheel alignment issue!

But keep in mind, we're not generally master mechanics. I have a lot of experience and some good general knowledge, but I'm not a trained bike mechanic. Using Loctite or any other specific solution isn't correct or best just because somebody here typed it.

Branimir

I think the threads in the downtube are a bit busted, so the downtube shifter screw got loose when using the lever. Yep, I'm using a busted SIS 6/7speed Shimano 600 downtube shifter in friction mode, since the cassette is 8 speed.

I would like to put a different downtube shifter, but since this one works, I don't see a point. Are there any indexed alternatives for 8 speed for downtube? Or 8speed means STI. Btw Ultegra 8 speed STI is too expensive, if I could find one... Of course if I stumble upon a friction only set of 600's I might put them on

Road Fan

I like those older 600s, even though I'm a strong Campy fan.

Branimir

BTW imageshack is down so all the images in my threads are now not showing.