chain grating on front xt mech

lock1981

hi felllas,

i got a problem with my chain grating on my front mech when in granny and middle ring and the rear in the upper 1 to 3.

its only started since i rebuilt my frame so its obviously something ive done but i cant sort it out for the life of me. it doesnt happen when its on the work stand ony when it under weight.

GOD DAMB IT!!! :twisted: what is it??

chedabob

Cable tension is wrong. Use the adjuster on the shifter to move it 1/4 turn at a time. The direction you need to turn depends on the type of mech and which side it's rubbing on.

Anonymous

The chain WILL rub if you're in the granny ring and the smallest sprockets at the back.
It might just rub a tiny bit in the middle ring as well.

Chunkers1980

yeehaamcgee wrote:

The chain WILL rub if you're in the granny ring and the smallest sprockets at the back.
It might just rub a tiny bit in the middle ring as well.

Mine doesn't. I've also altered the chainline inwards.

Mine does however slightly rub in middle and granny on my 32t rear - this is the better way round for me as you know by feel and sound that you don't have any more gears left (no display on my shifter)

lock1981

sorry it rubs in the bigger rear cogs not the small and ive gave it 1/4 turn 1/2 a 3/4 on the barrel adjuster


nightmare!!! :twisted: :twisted:

it never used to rub at all but it sounds like its rubbing in the the front mech, well it is!

ive also tried twisting the mech just incase i hadnt lined it up properly.

i took it to the lbs and he played about with a screw or too but you cant hear it on the bike stand need pressure on the pedals.

very annoying when climbing

Chunkers1980

Sounds like you've not got it at the correct height. Should be able to fit a penny between the outer cage and the teeth of the biggest ring.

The mech has different spacing for each of the rings (so it height dependent) to eleviate this.

lock1981

i did thing that, cheers chunkers.

i used a 2mm allen key as a guide but the teeth on my front rings could be worn seen as there over a year now

ill give it a go

stumpyjon

Full suss bike? Compressing the suspension can alter the position of the chain relative to the mech, I could get mine fine on the stand but it would rub when riding in certain gear combinations, it was worse when the suspension was moving. I couldn't cure it completely but made it better by playing with the mech position taking the sag effect into account.

lock1981

not the height difference either.

yeah stumpyjon its a full sus meta 5.5 2010

it does it slightly on the stand. well i can here it slightly....its just loads louder when pedaling

driving me mad!!!

bellys

is your mech back in the same place ? mine was very slightly out and it did it check the hight and make sure its in line i used a steel ruler to line it up with chain rings......drop it on to the small chain ring and slide the ruler up to the front mech and use the teeth on the large ring for your measurement....might not be the right way but worked for me.

lock1981

good skills !

ill give it a go but im pretty sure its lined up


cheers mate

lock1981

took it too my lbs near work .......and the bloke said straight away that it was a fault on the frame cos the front mech isnt 2mm all the way round the top ring!!! sound right?

anyway he did it and...................it was worse :twisted:

so i left it with him and.................it was the same!!!! :twisted: :evil:

he asked where i would like it to rub :oops: as it wasnt possible to set up without rubbing (this is a really LOUD rubbing noise) so i said where ever.

ill have to set it back to where is it was before because its loads worse now.

so i asked if the new sram chain was a different width to my old xt and he said u cant run sram chain with shimano cos its a foreign body!! lol

he said he couldnt sort it but it might be be cos i have jagwire teflon coated cables and not shimano lol wtf

so any more ideas?

nicklouse

got any pics yet?

lock1981

dont have photobucket

but theres not alot to see

birchy

If I were you I would just re set it by,
1 take the chain off
2 unclamp the cable
3 pull the mech out by hand to make sure it's in line with the big ring and can just clear it adjust if needed
4 wind the adjuster barrel back in then out 3 turns
5 put the chain back on shift into the big ring at the back
6 adjust the screw on the mech until you have a gap that a penny would slot in between the chain and mech
7 re clamp the cable
8 go through all the combinations and tweak
9 ride up the road and do some final tweaking
If these does not work then something must be bent

lock1981

bent it is then

dunno how though

birchy

One last thing has jumped in my mind as the chain should not rub as you preset the gap for the chain and mech, what cranks are they as I was thinking when you put them back on are they up flush against the bb on both sides as if not that would cause some lateral movement for chain rings causing them to rub.
Just another thought

ftwizard

Which side of the mech is it rubbing on?

lock1981

there xt cranks with a mrp triple chain guard.

it rubs on the inside ( bb side)

so yeah that might be right. maybe some muck grit what have you, inbetween spacers and that

ill \strip them down and clean

good thinking 8)

ftwizard

I don't understand this. The first adjustment you do is setting the stop to allow 0.5mm clearance when the chain is on the small chainring and large sprocket, so how can it be rubbing?

lock1981

it only happens under load, but i know what your saying...... but the lbs couldnt sort it either

just dont get it !!!