Front Mech Adjustment

Bobbinogs

Yes, probably a perennial but I can't find an exact match and the Park Tool guide doesn't seem to cover my problem.

I cannot seem to get the trim right when adjusting the front mech (on a double, btw).

I have set the low and high stops perfectly right. Then, set tension so that the shift up is crisp. When in the big ring and dropping to the last but one larger cogs at the back all is fine (just about, with a very slight rub but no more)...but when I shift up to the smallest cog at the back, the chain rubs badly on the front mech. So, the solution might be to adjust the trim of the mech so that the chain doesn't rub...but that means that I will get more rub when in the smallest but one cog.

Previously (as in before I had to change the LHS shifter) all was fine but only just, took a lot of frigging.

Any ideas? I figure I should be able to use 8 cogs out of 9 as I always have done and can do on my other bikes.

Thanks in advance.

Bobbinogs

Actually, been thinking about it and think I may have the solution:

The problem is a trim issue so I need to adjust the trim so it toes-in a little more. Then I will need to readjust the low and high stops. Then it should be ok in big/big and the extra toe-in should give me the range across the cogs...

Probably

sungod

which levers? many have a trim position

aside from that, while it's nice to have no scraping on the fd across the whole range of the cassette, in practice it's better to avoid the extremes, so the scraping becomes a handy reminder to shift rings

Bobbinogs

Br 4501, Tiagra 9 speed. Cheers Sungod.

philkeeble

I have exactly this problem on my 4-week old Roubaix Ultegra 6800. I can back off the limit screws completely (so that it's not them that's restricting movement of the FD) and adjust the cable adjuster to dial out all the rub when in small ring/big sprockets, but then it rubs like hell when in big ring/small sprockets. If I cable-adjust to get rid of the rub in the top gears, I get rub in the bottom gears (NOT talking about cross-gears). Yes I am using the trim click on the shifter. If adjusted for no rub in the bottom gears, then I can eliminate rub in the top gears by holding the big brifter against its stop, but there's not another click to keepit there! It's driving me nuts and clearly it'll be going back to the shop but any ideas are welcome. It's as if the shifter doesn't move the FD far enough (or that the ring spacing of the FSA chainset is too wide and therefore incompatible with the Shimano set-up).

Help!

wishitwasallflat

I like the rub the noise reminds me not to cross chain :!:

philkeeble

As I pointed out, the rub issue I'm experiencing is in the inner/inner, and outer/outer positions, NOT in the cross-gears.

Bobbinogs

I sorted my problem out by adjusting things again until they were all sweet and then discovering...the trim function on the 4501 shifter! Brilliant, slightly rubbing?...trim.

I don't think my old 4500 LHS shifter had that, may be it did. Point is, I don't have to worry about getting the whole range I can go from 1-7 (x34) or 2-9 (x50) with no rub and crisp shifting.

Now, just need to put my winter wheels back on for the predicted light snow at the w/e

NE Cycleworks

The issue is usually solved with more cable tension. Assuming the high and low limit screws are set as they should be then wind out the barrel adjuster 8 turns before anchoring the cable so that you can get some proper tension on the cable using the barrel adjuster after you've tightened the cable clamp. You should not be able to move the FD with the lever beyond your set limit when set up correctly.