Bicycle Mechanics - Is there a FD height problem w/installing a 48/34 on a roadie?

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Autobus
09-20-06, 01:42 PM
Just wondering if a 48/34 cyclocross crankset would be a problem on a standard roadbike. My friend has a 50/36 on his Scott and the front derailleur is all the way down the groove on his braze-on.

Help? Thanks

HillRider
09-20-06, 01:48 PM
If you have a braze-on fd mounting tab and it won't let the derailleur go low enough for proper (1-2 mm) clearance with the 48T ring, the shifting will be less than ideal but it will still work. Now you know why clamp-on fd mounts have become nearly universal if the seat tube shape will allow it.
Autobus
09-20-06, 02:02 PM
If you have a braze-on fd mounting tab and it won't let the derailleur go low enough for proper (1-2 mm) clearance with the 48T ring, the shifting will be less than ideal but it will still work. Now you know why clamp-on fd mounts have become nearly universal if the seat tube shape will allow it.
Dang. Can you remove a braze -on mount easily from a carbon bike and install a clamp - on?

Al1943
09-20-06, 03:10 PM
Dang. Can you remove a braze -on mount easily from a carbon bike and install a clamp - on?

No, clamp-ons are not recommended for CF.
On my wife's CF bike I was able to grind te slot deep enough for a 49t chainring. I used a dremel tool and a round file. The metal is soft and grinds really quickly so be careful if you try it.
If your hanger is held on with screws you might be able to remove it and have a custom hanger made at a machine shop. That has been done by others.

Al
Sincitycycler
09-20-06, 05:59 PM
No, clamp-ons are not recommended for CF.
On my wife's CF bike I was able to grind te slot deep enough for a 49t chainring. I used a dremel tool and a round file. The metal is soft and grinds really quickly so be careful if you try it.
If your hanger is held on with screws you might be able to remove it and have a custom hanger made at a machine shop. That has been done by others.


Al

On my wife's CF bike I was able to grind te slot deep enough for a 49t chainring. I used a dremel tool and a round file
Pretty resourceful there. I like that!
Al1943
09-20-06, 06:47 PM
Pretty resourceful there. I like that!

Thanks.

Necessity is the mother of invention.