Front Derailleur

lafors

I was out for a spin today (after I got my boards gear off Scott....Thanks again Scott!) from Clontarf and over Howth head both ways.
I went up the "less" steep side without any problems, but after starting my ascent up the steep side I went to change my front chainring down?(to the smaller cog) but the derailleur didn't move enough to make it drop.
I decided to stop to have a look. Did a 0kph fall because I unclipped the wrong foot, just as there was a good looking girl walk past laughing She said I was doing well until the fall
Anyway I didn't have any tools so I just had to suffer it.

I got home and went about adjusting it myself, I was using the tips on jimlangley.net. I've got Shimano 440 Rapidfire Plus 18 speed shifters, Shimano 105 on the back and Shimano 440 on the front.
After a small adjustment I now have it back changing between the 2 rings without any problems, but when I have it at its furthest travel on both the big & small chainrings, the chain clips the derailleur. Its a minimal amount of touching but no matter how much I adjust it it clips one side or the other of the derailleur.

Anyone else have this problem before & how did you fix it?

bcmf

sounds like it needs a fraction more adjustment each way
OR
you made need to move the front mech by slightly undoing the mounting bolt and moving it side to side on the braze or downtube.
A good tip I got many years go is if you cant get it go right back to re-setting it from zero

blorg

You would expect derailleur rub in the big-big and small-small combos, maybe even 1 gear at the back either side of these. Is the rub present outside these combinations?

lafors

blorg wrote: »

You would expect derailleur rub in the big-big and small-small combos, maybe even 1 gear at the back either side of these. Is the rub present outside these combinations?

No rub in any other combos, its clipping on the big-big / small-small combos like you say. If I adjust, even tweak, say 1/8th turn of the screw, it stops the clipping but when the gears are changed to the opposite side then the big-small / small-big is rubbing.

bcmf

Expect rub on the extremes
ie BIG Front Big Rear/Big Front smallest rear
Small Front Big Rear/Small front Small rear
Just make sur that when you adjust it it's not too far out that when you drop to smallest front ring that it drops off and vice versa with the Big Front that it doesnt force the chain over the big ring.

TinyExplosions

bcmf wrote: »

Expect rub on the extremes
ie BIG Front Big Rear/Big Front smallest rear
Small Front Big Rear/Small front Small rear
Just make sur that when you adjust it it's not too far out that when you drop to smallest front ring that it drops off and vice versa with the Big Front that it doesnt force the chain over the big ring.

I disagrees here, you should be fine on Big Front/ Small Rear and Small Front/Big Rear -these are your highest and lowest gears, and should be fine as the chain is running fairly straight for these combinations, the problems occur in a cross chain situation, ie Big/Big, Small/Small

bcmf

TinyExplosions wrote: »

I disagrees here, you should be fine on Big Front/ Small Rear and Small Front/Big Rear -these are your highest and lowest gears, and should be fine as the chain is running fairly straight for these combinations, the problems occur in a cross chain situation, ie Big/Big, Small/Small

I was under the illusion that on an 18 speed there would be rub as I mentioned.

blorg

You should never use the big/big or small/small combos on a triple due to this issue and the extreme chain angle it produces. You shouldn't need to use them as these gears are duplicated with the middle chainring and a less extreme angle. This is called "cross chaining."

If you can get it set up so that the chain only rubs in those two combinations and not in any other you have your bike set up very well. You would often have rubbing in 1 or two sprockets off these two combos also, indeed it is prudent to avoid these also.

It should not rub in big/small or small/big, they are gears you should be using (highest and lowest.)

Harpz

Tiny is right (in this instance*).


*The pink bike he bought is an abomination unto mankind

Chips Lovell

lafors wrote: »

No rub in any other combos, its clipping on the big-big / small-small combos.

That's meant to happen as you aren't supposed to use these combos.

lafors

My Name is Mario wrote: »

That's meant to happen as you aren't supposed to use these combos.

Then surely they should call it
18 speed*
*Oh we forgot to say you shouldn't use 2 of these, so it's really only a 16 speed

Its set up with it only rubbing on big-big & small-small now.
Your explanation of "Cross-Chaining" makes sense blorg, I suppose you don't want the chain running at 'extreme' angles.

I guess I'm just going to have to invent a new method & then take on Shimano
I did have a project in college where I tried to create an automatic gearing system for a bike, super idea, just very hard to implement.......hmmm

Tau

lafors wrote: »

...an automatic gearing system for a bike, super idea, just very hard to implement.......hmmm

With the new electronic derailleurs, there's no reason why you couldn't link them to a cadence sensor and get them to shift to keep the cadence in a defined range (say 85-95) (depending on your gearing)

Not sure you'd want it though, especially when racing. Might be an interesting training tool however.

blorg

Shimano already have an automatic transmission for city bikes. Skwirl will fill you in... No, it's not for racing

lafors

blorg wrote: »

Shimano already have an automatic transmission for city bikes. Skwirl will fill you in... No, it's not for racing

Dammit
I bloody should have patented it when I thought of it in 2000.....maybe they had done it already.
I want a gun to shoot that "Skwirl"