Rear derailleur adjustment screws problem ...help plz.

Page may contain affiliate links. Please see terms for details.
I have just rebuilt my hardtail mountain bike after having frame powder coated, its an 2005 bike so all the components were getting worse for wear, so I replaced many parts for new ones its now like a new bike again:thumbsup:

Anyway the old crankset was worn and stuffed as an old fixed chain wheel version so needed replacing so I bought a Alivio replacement 42-32-22 x 170 which has replacement rings if required at a later date, I'm also running an new 8 speed KMC z chain, all was well but the rear derailleur was a shimano Altus mega pulley type with oversized 15 t jockey wheels but since 05 its slowly been wearing to the point that the whole thing moves about and shows wear at all pivot points.

So I got today a new shimano Alivio 8 speed rear mech with oversized 13t jockeys and all is well it works great and is very smooth shifting now its all set up and chain is fine did'nt need to add or remove any links, but after setting the H and L screws I them went on to set the 3rd screw for the tension which screws in or out against the rear mech hanger which is also new.

The problem is that when chain on smallest front ring and largest rear sprocket to allow the chain to run freely you need to turn the 3rd adjust tension screw to lift the 1st jockey wheel away from the largest and other sprockets or the chain rides bumpily along the top of each sprocket, the old Altus screw was about half way in adjustment wise and was perfect but with this new alivio one I bought today the screw has to be turned all the way in to give clearance required, although its working fine now will the spring tension wear very quickly and cause the chain to bump against rear sprockets once again as there is no more adjustment available ?

Any help with this question much appreciated,

Deano

2013-09-25-916.jpg
2013-09-25-919.jpg
 

RecordAceFromNew

Swinging Member
Location
West London
It is surprising that the B screw of an Alivio rear mech needs to be fully engaged to clear the sprockets, I suspect the reason is because your previous chainring is larger than 44T, making the existing chain too long for the current setup. If so you can work out the correct length with this.
 
OP
OP
deano69

deano69

Veteran
It is surprising that the B screw of an Alivio rear mech needs to be fully engaged to clear the sprockets, I suspect the reason is because your previous chainring is larger than 44T, making the existing chain too long for the current setup. If so you can work out the correct length with this.

My old crank / chainset was same 42-32-22 170mm arms so new one is same and chain was worked out exactly on the convertor and is running fine through all gears and misses the derailleur cage just right when in the highest gear as I quickly just added a link and it rubbed on itself so took one out and replaced its fine even the local shop checked it and said chain is right length gears are perfectly set up but when i mentioned this screw fully all the way home they just said some do some dont they're all different ?

Deano
 

RecordAceFromNew

Swinging Member
Location
West London
My old crank / chainset was same 42-32-22 170mm arms so new one is same and chain was worked out exactly on the convertor and is running fine through all gears and misses the derailleur cage just right when in the highest gear as I quickly just added a link and it rubbed on itself so took one out and replaced its fine even the local shop checked it and said chain is right length gears are perfectly set up but when i mentioned this screw fully all the way home they just said some do some dont they're all different ?

Deano

Ime you only need to engage the B screw fully if you are using a cassette that is pushing the boundary of the mech's spec., or the frame/hanger is unusual - but you said the old Altus worked fine. The other thing I don't accept is that otherwise you have problem with not just the largest but all the sprockets. I presume you don't have an unusual cassette of course.

There are other possibilities. Re your new hanger is the distance between the centre of the rear wheel axle and the rear mech fixing bolt significantly less than 30mm?
 
OP
OP
deano69

deano69

Veteran
Nothing to add but am I the only one (a little) disturbed by your avatar?
Lol :laugh::laugh: I changed it now just for you, No what it was the laptop had a problem and completely froze up I had the whole thing wiped and new version of windows added but all my pics got deleted and that one was one of a few that I had of me but should of found a more suitable one agreed :laugh:

Deano
 

uclown2002

Guru
Location
Harrogate
Lol :laugh::laugh: I changed it now just for you, No what it was the laptop had a problem and completely froze up I had the whole thing wiped and new version of windows added but all my pics got deleted and that one was one of a few that I had of me but should of found a more suitable one agreed :laugh:

Deano
Top man :becool:
 
Top Bottom