Struggling to fine tune old front derailleur

benws1

I'm doing up an old 7 speed mtb as my brother wants to ride it a bit (CBR Slice). Its about 20 years old and is a full suspension frame.

I'm really struggling to setup the old front derailleur, a Shimano FD M330 triple.

I have to cabled it and set everything up as per the Shimano instructions. However, a few niggles are still appearing:

1. When in the stand, it rubs the when on the smallest two cogs on the rear with the largest front chain ring selected. But when I ride it, it doesn't really rub. If I try to increase the cable tension to remove this rub, it introduces rub on the derailleur when I'm in the two largest rear cogs and the intermediate chain ring.

2. When in the intermediate chain ring, it rubs when on the smallest and largest rear cogs.

I have got it so it's working fine on most gears, but the extremities rub. In terms of cross chaining, I'd rather it rubs when on the largest chain ring and largest rear cog, but I cant add more tension to achieve this.

I will say that when I got the bike to look over, the front derailleur looked like it had had an impact as it was twisted around a bit and nowhere near the correct height and angle setting.

Could my issues be the result of a bent derailleur, or is it that I'm trying to make it too perfect and you will always get some rub on these old triple setups.

I'm using a bog standard Clarks 7 speed chain with a snazzy suntour rear cog if this helps.

Finally, I have been looking at new front derailleur. I have found one that has a max teeth limit of 18. The cranks on the bike (some old Cyclone things) are 42 on the big chain ring and 22 on the smallest, meaning 20 teeth. Would this be ok with an 18 teeth derailleur?

Thanks.

mully79

Check if there's play in the pivots on the derraileur. If there is then your fighting a losing battle.
On saying that I find front derraileurs infuriating and generally always seem to get some rub somewhere.

benws1

mully79 said:

Check if there's play in the pivots on the derraileur. If there is then your fighting a losing battle.
On saying that I find front derraileurs infuriating and generally always seem to get some rub somewhere.

Thanks. Will check for play.

I'm guessing it's been bent. As I said above, it was on a funny angle on the post when I got hold of the bike. Looked like it had been dropped. There is no way anything light caused the thing to be moved because it was bolted on tight. Must have been some force.

I would like the rub to happen on the bigger rear cog and bigger front cog. At the moment though, I can't get it to rub there because I can't increase the tension on the derailleur without messing up the intermediate chain ring setup.

reaperactual

Even on the best setup and new condition front mech I've never been able to tune out rub in the extreme gears.

Exactly the same as you describe, tune out one issue and the opposite issue starts with no 'sweet spot'.

Irritating because you do everything right and can't avoid the rubbing issue somewhere.

Using the half shift/click helps on large chainring/smaller cog combo so getting the opposite small ring/big cog to not rub would probably be the least compromise and the best you can expect.

I eventually had enough, stopped trying and went 1x.

benws1

Thanks.

I think that rather than throwing more money at it and investing in a new front derailleur, I will just leave it as is.

It's the first time I have setup a derailleur like this and to be fair, the equipment is 20 years old. I have managed to get most gears working fine. I'm just a perfectionist and it annoys me.

There is no trim option on the shifters on the bike. That would help.

I will live with the rub on the smallest rear cogs when on the big chain ring. I will also live with the rub on the biggest and smallest cogs when on the intermediate chain ring. There are other gear options I can use to cover this off.

reaperactual

Don't beat yourself up about it. Being a perfectionist with this issue makes it even more frustrating,😤 add that to the extra difficulty without the trim function to help. 🤬

Reckon it's just the way it is, not that it helps but it seems the same on relatively new front mechs too ime.

benws1

Thanks. I will try not to.

I have followed the shimano instructions carefully. Can't do much more.

It could be old chain ring, old bent derailleur, anything I guess.

veronese68

Sounds like it's all a bit old and tired, bits of play here and there stopping it running perfectly. Your brother will soon learn to ride around its foibles and then it won't be an issue.

benws1

Yep. Thanks.

I could go for it and buy a new derailleur, but I'd want to upgrade the chain ring etc if doing that. I'm already 100 quid down and its useable now.

Anyone know if you can use an 18 tooth max derailleur with a 20 tooth difference chain ring?

benws1

mully79 said:

Check if there's play in the pivots on the derraileur. If there is then your fighting a losing battle.
On saying that I find front derraileurs infuriating and generally always seem to get some rub somewhere.

I gave the derailleur a wobble. It wobbles very well. There must be quite a bit of play in there.

Its usable for about 70% of gears and is only going to be gingerly ridden around the village. I dont see the point in spending more time and money on it.

Part of me wants to go full bore as I've really enjoyed learning with this bike. Will save that enthusiasm for the next bike I'm working on which will be my commuter bike. It needs a full overhaul.

steve_sordy

If it is only going to be ridden around the village then convert the front mech to a 2x. All you have to do is to wind in one of the limit screws! Yes it's as simple as that! The shifter will still be a 3x shifter, but the rider won't be able to shift into the third gear.

All you have to do is to decide which front ring you will isolate. Unless your village is built on the side of a steep hill, I'd isolate the granny.

benws1

Thanks. Good idea. Will see what my brother says. The village is in Lincolnshire and is completely flat.

david37

steve_sordy said:

If it is only going to be ridden around the village then convert the front mech to a 2x. All you have to do is to wind in one of the limit screws! Yes it's as simple as that! The shifter will still be a 3x shifter, but the rider won't be able to shift into the third gear.

All you have to do is to decide which front ring you will isolate. Unless your village is built on the side of a steep hill, I'd isolate the granny.

Grannys are isolated enough in lockdown