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I'm try to adjust an Ultegra triple front mech fitted to my Roberts Audax frame. It worked perfectly before I swapped the crankset. I fitted a Middleburn crank onto an SKS Isis BB. The rings are Middleburn 50-34-28. Chain and cassette are used but unworn, cable and outer are new. Shifters are Ultegra Sti
The shift from the small ring to the middle requires pushing the lever past its first click and well over onto the second click to get the chain to move wen on the largest sprocket. The upshift onto the big from middle ring is hopeless. I have other triples on other bikes which work faultlessly.
I've tried adjusting the position of the mech clamp on the seat tube and rotating the mech relative to the chain rings. The improvements are only marginal.
Am I missing something obvious?
not sure about roadie stuff, but have you the right spaces on the 'right' side of the chainset?
is the axle on the bb the right width, is it the same as the old cranks/bb, sounds like you have a wider axle than before
When swapping the bb I had to install two 2.5mm spacers, one on each cup.
I tried putting two on the non drive side, which didnt help, would putting two on the drive side make a difference?
not sure about isis, the only ones i'v had used no spacers, you had to get the right width axle when buying them, sounds like they are too far outboard, try taking the driveside spacer off, and also is the big ring the same size as the older one, if its bigger it may need moving up a bit
if they are outboard cups on a 68mm shell its 2spacers non drice side 1 driveside, 73mm shell one on driveside only
[i]if they are outboard cups on a 68mm shell its 2spacers non drice side 1 driveside, 73mm shell one on driveside only [/i]
I did this and had problems, on a Hope BB its 2 spaces drive side, and 1 non-driveside.
When I've had this, I've put the orange plastic spacer thing (that's on the mech when you buy it) back in and then set cable tension. Then it worked??
As boxelder...hold the mech about 10mm out towards the outer ring and then take the slack out of the inner cable. Then try to fine tune using the barrel adjusters.
There are two variables here. The crankset I replaced was an X type BB with a Bontrager triple 53 39 30.It was probably spaced out to 73mm. When I installed the SKS Isis BB I measured the BB shell. It was a 68 mm shell. There is a sticker on the BB which says you have to fit spacers to make up the difference to 73mm. I got two 2.5mm spacers. Are there other combinations of spacers adding up to 5mm that I could fit to space the axle in or out in either direction? Which side should I put them on?
It might sound daft but have you set the limit screws correctly?
If I'm teaching you to suck eggs I don't mean to offend.
Make sure the limit screw for the inner most chain-ring is set so as when in small/big the chain just misses the mech, clamp the cable, then set the other limit screw when in big/small.
Adjust the cable tension to suit so the middle ring doesn't rub in the majority of gears after that.
Again, sorry if you've already tried this.
steve_b77 - Member
It might sound daft but have you set the limit screws correctly?If I'm teaching you to suck eggs I don't mean to offend.
I think the problem lies with the bb spacing.
can you contact roberts for the correct axle width for a isis bb, last isis i had you had to get the correct axle width, ie 108-110-113-118mm as well as the shell size, if the axle is too wide or too short you have problems
Cheers Khani
I'll call them in the morning. I do have a Race Face Isis BB which is adjustable. I might try fitting that.
No worries 😀
68mm shell - 113mm axle
Roberts are closed on Mondays so I'll ask here one last time.
Pete, IME front shifting is heavily dependant on ramped chainrings of the right size for the front mech - chopping and changing chainring types and sizes can often cause problems, as the mechs work really well within their design parameters and rubbish outside of them. Even going from a 13T to 16T jump may be enough.
I know this is not helpful, but I doubt moving the chainline is going to have much of an effect, and it's nowt to do with the frame.
I had loads of trouble trying to set up a freinds ultegra the other day, and it was my unfamiliarity with roadie stuff that was my downfall. I didnt relise the front derailure, well actually the shifter, has four positions not three! At the risk of offending, youve not made the same mistake have you? 😳
from the manual: -
There are 2 derailleur positions for the intermediate chainring. When
making the cable adjustment, make sure that the derailleur is in the
inner side (toward small chainring) of the two positions. Locate the
derailleur to this position by shifting from the largest to the
intermediate chainring (recommended) or by shifting from the small to
the intermediate chainring, then gently press lever (b) until a small
click is felt (to position the derailleur to the inner side of the
intermediate chainring).
Al, the 'rings arent ramped, so I expected a poorer shift. I hear what you are saying re standard triples and their mechs. I was just trying to make a 'compact' triple for heavier hilly touring. I suppose if I cant improve the change with this ring combo, I could fit an mtb front mech and alter the rings.
I'd try a compact front mech or an old mtb one for sure, but unramped rings really are gash at shifting IME.
I suppose if I cant improve the change with this ring combo, I could fit an mtb front mech and alter the rings.
Roadie shifters pull a different amount of cable, or the mechs have a stronger spring or something - either way, they don't work with mtb mechs AFAIK.
so you now have middleburn rings? which rings were on it before?
you deffo have the cable fitted around the pinch bolt exactly where it should be and not wrapped UNDER any "knuckles" that are on the arm of the mech by any chance? had a bike on friday with the cable fitted around the pinch bolt correctly but not over the knuckle (from the factory) and there was no way it would set up correctly if left like that. worth a check.
Oh aye boxelder is right - you'll need a compact triple mech (if that exists?)
Meant to say - did your Burma Rd route on Sunday, NICE!
martinxyz - Member
so you now have middleburn rings? what rings were on it before?
I changed the complete crankset from Bontrager to Middleburn. Different rings sizes too.
if you had the time, and if it were possible.. could you fit the old rings onto the new setup to see if it rules out the new chainline etc?
cynic-al - Member
Oh aye boxelder is right - you'll need a compact triple mech (if that exists?)Meant to say - did your Burma Rd route on Sunday, NICE!
Suttles off to google compact triple front mechs.
Burmah Road downhill good, did you do the second climb up to the mast?
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We did - to the first cairn after the mast. Best to ride down/left at the fence once you cross the second burn (on the way up, at the bottom) as you then hit the LRT and can pedal up instead of bush-whack.
Enjoyed that wee swoopy descent then found a buch of tracks on the rocky bit near the burn at the bottom. Hoofed it back to Avie as I had no map.
You have moved from a 53 chairing to a 50 t chairing correct?
If so I presume you have moved the front mech down a little?
Are the new middleburn cranks the slick shift ones or normal without ramps and pins?
I'll assume limit screws are ok now. 113 isis b.b sounds the correct length for a tripple (well it's what I used on a bike last week).
It works!
Big thanks to Mike Varley at Balck Mountain Cycles in Point Reyes Station, Marin.
The distance from the centre of the seat tube to the middle ring needs to be 45mm for the front mech to work. I now have a perfect chainline, Shifting isnt as smooth as with ramped and pinned rings, but I now have a great range of laden touring gears. 8)