Hi guys,
I’m in the process of building a bike for the mrs, using various used bits sourced online. I’m almost there but having a problem with the rear mech top jockey wheel touching the biggest cassette ring when on the smallest front chainring… I’m trying to work out if I’ve bought some incompatible bits, here is what I have:

15″ specialized rockhopper frame (used)
Cheap new shimano crankset (I just noticed this says up to 21 speed do you think this is the issue?) http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=330554018197&ssPageName=STRK:MEWNX:IT#ht_2013wt_1195
Deore Rear Mech RD-M510 (used) – http://velospec.com/components/shimano/rdm510
SRAM PG950 Cassette 9sp 11-34 (new) -http://www.chainreactioncycles.com/Models.aspx?ModelID=5045
9 Speed SRAM chain (can’t remember model, but thats also new and purchased from same local shop same time as cassette).

I’ve tightened the Higher-Adjuster screw as per (as tight as it will go) will a longer screw help? :

but the rear mech jockey wheels still touches the casette but only when the chain is on the smallest front chainring…. is it the chainrings/crankset to blame?

thanks for your assistance 🙂

is the chain the right length? big chainring to big sprocket NOT thru the mech and add two links

Chain length by the sound of it

<Edit> Too slow, TJ got there first </Edit>

That would be my first thought too.

Rear mechs have a maximum top sprocket size. For those giant mega-range ones you have to have a certain mech with a really big jockey wheel for instance.

I’ve tightened the Higher-Adjuster screw

That’s the b-tension adjuster but yes it is what needs tightening. A longer screw won’t work as the angles get messed up (trust me).

34 is massive though. This could be it.

Chain length I’d say.

I have 11-34 on both bikes, one with SLX 22/3?/44 tripple and longer cage, the other with SLX 22/36 double and short cage. Neither are a problem, so I doubt that this is what the OP is experiencing.

Deore rear mechs are rated upto a 34T sprocket so in theory it shouldn’t be a mech / cassette compatibility issue.

thanks for quick responses.

is the chain the right length? big chainring to big sprocket NOT thru the mech and add two links

I will check this tonight when I get in, but can you buy chain extension links? for these poplock style SRAM chains? (sorry this is the first one I’ve used)

brungle – its more likely too long not too short.

wot tj said-you probably need to take few links out!

ahhh I see!
thanks for that.

Do you think it’s too long?

Thanks

yep

yep, take 3 outer links off. Doh ! that should have been an edit

Thanks, for rapid response

I wouldn’t lose 3, you should have an overlap, do one at a time and try it…. Easy to take away…

Too late 3 removed 🙂

Seems to have resolved the issue so thank you all very much, the help is most appreciated!

Really helpful guide to chain sizing over at Park Tools

Park Tool Co. » ParkTool Blog » Chain Length Sizing