Chain rub?

[Stephenjames]

Hiya,
Can anyone please help me? I have just put a new Dura Ace 10sp Mechanical groupset on my Litespeed Tuscany frame. The problem is, eliminating chain rub. I know it must be just a case of the balance right over the chainset and maybe it comes with practise and experience but, does anyone have any advice or tips on how to best go about it??

Thanks.

 

[accountantpete]

If you mean that the chain is rubbing the front mech when running at an angle (ie small front and small back) then you MAY find that there is a sweet spot.

I'd suggest (you have probably tried this though) putting it on the small front and say 3rd smallest sprocket at the back. Then undo and moving the front mech until the outside of the chain is just missing the inside of the front mech and then tighten up.

(you don't want to be running small front and the 2 small sprockets at the back as it will wear badly).

As I say - this MAY do the job but it depends on the chainline and the length of the chainstays etc etc. This is why Shimano introduced the trim feature which moves the front mech very slightly.

 

[Stephenjames]

Hiya accountantpete,
Thanks for taking the time to reply to my post. The chain has been rubbing the front mech in large chain ring and small sprocket and if I eliminate that it rubs in small chain ring large sprocket. I guess its just a case of trail and error and finding the 'sweet spot' as you say. I just wondered if there is a method to eradicating chain rub all together as I don't want to wear the chain out on the front mech. I guess I just need to play around until I have the mech set up so it is clearing throughout the gears. On my old 9 speed Dura Ace groupset, the front shifter has a 'trim' feature as you say, but the 10 speed doesn't seem to have this feature, just wondered why. I know the Di2 does it automatically, which must be awesome.

Guess I just need to brush up on my mechanic skills, practise makes perfect as they say.

Thank you once again.

Steve.

 

[RecordAceFromNew]

Hiya accountantpete,
The chain has been rubbing the front mech in large chain ring and small sprocket and if I eliminate that it rubs in small chain ring large sprocket. I guess its just a case of trail and error...

No, the chain should not rub on either large front small back or small front large back - front mech adjustment is not really a trial and error thing either in that it should be possible to get it just right systematically.

Chance is either i) too little cable tension and wrong L screw setting or ii) cable tension too high and wrong H limit screw setting.

If the chain rubs on small front large back, that means either a) too much cable tension - you can feel if the cable is taut taut - it shouldn't be, if yes adjust adjuster if not then b) wrong L screw setting - it should be turned anti-clockwise, in either or both cases until the chain clears the front mech by 1mm.

If the chain rubs on large front small back, that means either a) insufficient cable tension - you can try pulling the cable to see if it improves, if yes then adjust cable tension adjuster if not then b) wrong H limit screw setting - it needs to be turned anti-clockwise, in either or both cases until chain clears front mech by 1mm.

Following this step by step works.

 

[Sweeney]

Following this step by step works.

I have developed the same problem, cheers for the link. Will try to sort it out over the weekend.

 

[Stephenjames]

Thank you RecordAceFromNew,
What you said makes a lot of sense, You are right I guess it IS an exact science, so thank you, have read thought it and now have a got idea how to correct the problem. Thanks also for the link. awesome.

 

[boydj]

If it's a band-on front mech, then it may need to be rotated very slightly to get it just right.

 

[ayceejay]

I had this problem and spent three lifetimes fiddling with the front mech only to discover that it was adjustment at the rear that was needed.

 

[Stephenjames]

Thanks boydj, it is a band-on front mech. I will check the alignment.
Thnaks for the advice ayceejay, may I ask in what way the rear derailleur needed adjusting??

 

[Stephenjames]

Does anyone know why the Dura-Ace 10 speed groupset doesn't have the trim feature like the 9 speed did??