another front mech question?

baccaman21

I'm changing my chain set from 2 to 3 ring on the front.

The front mech is Deore FD-M510 - it reckons on the specs on the shimano site that it's top gear teeth range is 44 - 48...

So, I've aquired a shimano 44t chainring and fitted it with no trouble having removed the old bashring from the cranks.

Now, when it comes to the mech...

- I've loosened the clamp and positioned a few mill higher up the seat tube
- I've made sure it's in line with the chain
- I've pulled the slack through on the inner cable and tightened the pinch bolt

now here's the crux...

1. The chain will no longer shift down to the granny ring
- even with the lo limit screw completely loose?
2. When I pull on the inner cable to tension the mech to shift it, there's no way on earth the chain will reach the outer ring
- again, even with the high limit screw completely loose?

It's really weird, it's like as if there's not enought range in the action of the cage...?

anyone any ideas?

(it's a 9 speed system - 9 speed chain - 9 speed compatible mechs [front and rear] - Deore throughout)

P.S. i've read all the Park Tools guides and the Shimano PDF installation guides...

stu8975

was you crank originally a 2 ring job? or did it come as a 3 and you removed a ring?, if it was a 2 ring and you have fitted a 3rd ring, you will need 1) a longer chain 2) probably a different bottom bracket axle length (shorter)

baccaman21

I know about the chain length...

as for the crank... it had a bash ring in place of the 3rd chainring... if that answers your question...

thanks.

stu8975

what chainset have you got? my xt mech has the same range as your m510...if it was originally a 2ring with bashguard when you got it, chances are you will have to change your bb for a shorter one. what size bb shell do you have?

stu8975

the correct size axle should be around 113mm for your gearing (assuming you have a square taper chainset/bb). But id recommend you take it to a decent bike shop to have it checked. Also check the chainline measurement (centre of seatube to middle ring) your looking for approx 47.5 - 50mm depending on what size your seatube is.

baccaman21

it's a raceface evolve crank. Isis BB... not sure of length ATM as I've packed it all away... Ill check it out when I next get the chance...

I did take it to a bike shop not so long ago to ask them if it were possible to switch the bash guard for a chainring... they had a shufties and seemed to think it would be a fairly easy swap....

thisis the bike... or should I say was... as I've changed every component on it now bar the cranks, derailieurs and rear shock... (and the handlebar grips)

stu8975

Ah, if its the evolve dh isis, then you will have to buy a new bb as its designed to be used on single/double chainsets only (axle length is 118mm) and is offset. you may be better with the evolve fr bb (113mm axle length).

baccaman21

balls... more expense...!

baccaman21

it's a "Race Face DH Evolve Double X Type"

but I can't find any references or specs for a 'double x' type on the raceface (horribly slow) website...

(I'm trying to track down whether the axle length is too long... ?!

Oh... I've just spotted too on the installation instructions on the PDF download that (what I think is) my BB IS compatible with 3 ring set ups...?

"COMPATIBILITY: the X-type DH & XC/AM bottom brackets are compatible with both 68 and 73mm BB shells using fixed or E-Type derailleurs. They are also compatible with double or triple ring set ups. Race Face X-Type bottom brackets can also be used with shimano external BB cranksets."

Which begs the questions... how do I find out if I've got a 68mm or 73mm shell? and what are E-Type deraileurs?

Any ideas?

clanton

You can measure the actual shell (part of the frame that the bb fits inside)
An Etype derailleur mounts via the bb itself rather than around the seat tube
ie this
http://bike.shimano.com/catalog/cycle/products/component.jsp?PRODUCT%3C%3Eprd_id=845524441762913&FOLDER%3C%3Efolder_id=2534374302053248&ASSORTMENT%3C%3East_id=1408474395181785&bmUID=1194289148505

NOT http://bike.shimano.com/catalog/cycle/products/component.jsp?PRODUCT%3C%3Eprd_id=845524441762914&FOLDER%3C%3Efolder_id=2534374302053248&ASSORTMENT%3C%3East_id=1408474395181785&bmUID=1194289182943

baccaman21

cheers clanton... I think it's starting to make sense now?

I make the shell length 73mm... and it's not an E-Type...

So I think the issue I've got may comes down to the spacers between the crank arm and the BB outer Cup??

Is that right?

There's 1 x 2.5mm spacer on the drive side... if I got rid of that would that give me the clearance for the outer ring / front mech combo?

clanton

Um not sure that will solve your problem. Normally with a 73mm shell you use either one spacer or an E-type mech with a triple ring. I suspect getting rid of that spacer will bring your bottom bracket cups closer together but will not affect where your chain rings end up as the axle length will stil be unaltered. Not 100% on that, hopefully someone can confirm this?

stu8975

Remove the spacer and check the chainline when its fitted back together.

baccaman21

right ho... I'll give that a whirl when I next get an opportunity...

thnx fellas.

baccaman21

here's a few things I'd discovered whilst attempting to change from a 2 ring to a 3ring set up.

Facts:
1. The Raceface evolve DH BB IS COMPATIBLE with a 3 ring set up.
2. There's NO NEED to remove 1xSpacer, as suggested above (in fact doing this will damage the internal plastic sheath)
3. Check, double check and check again that everything in the first place is correctly assembled...

Remember I said in my original post it's like there's not enough range in the action of the cage?

Well - it turns out the PINCH BOLT... YES THE FRIGGIN PINCH BOLT was installed incorrectly... (and I blame the original setup engineer for this as I've always been aware of positions of everything and re-assembled according to my observations) - the u[pshot of this meant that the piece of metal that the pinch bolt presses down onto the inner cable wire was fouling on the body of the derailleur - thus limiting it's range.?!?!?

So, now it works... fine... simple... as it should have always been and I thought it was going to be....

I've gone round in circles with this... and I think the biggest lesson I've learned is to not take advice on these forums as gospel...

For the sake of turning a tiny (apparently incinsequental) piece of metal!?!?
[/rant]

PS - No offense meant to anyone who's helped me out here...

supersonic

Lol, seen this a few times - and done it myself!

BB compatibilty and length depends on your required chainline and clearance.

baccaman21

yup... well lesson learned anyway... at least it forced me into reading up on the whole thing so I now at least I know what to do when it comes to messing proper with ma' BB... (prior to this it's kinda frightened me a bit as it's been the last frontier in terms of my fettling know-how)

I'm still reeling at the simplicity of how easy it was to solve... I've been putting it off for a week too... :roll: :roll: :roll:

hey ho - ya live an learn!