Braze-on front mech using clamp/band on adaptor

[Sweep]

Hi folks

I acquired an old mech which I fancy fitting to an 8 speed self build of mine.

It's a braze-on type but I did buy an adaptor to allow me to fit it to my frame.

Before I take the old band-on mech off, I was just wondering if there are any disadvantages or issues with using a braze-on mech with an adaptor rather than just a band-on mech?

Am pretty confident that the braze-on mech itself (an XT) is superior to the cheapo shimano band-on one on the bike at the moment.

[2_i]

Braze-on mechs have been more common on road bikes and band-on on MTBs. Is the new mech made for the same chainring number that you currently have? The cage sizes and shapes should be comparable. Beyond that, you should be generally OK even if some other nominal details were different. In the worst case you can take the new mech off and go back to the original.

[Sweep]

Braze-on mechs have been more common on road bikes and band-on on MTBs. Is the new mech made for the same chainring number that you currently have? The cage sizes and shapes should be comparable. Beyond that, you should be generally OK even if some other nominal details were different. In the worst case you can take the new mech off and go back to the original.

Pretty sure the braze-on fitting mech is suitable for my chainrings - I checked before buying it - thanks for the general OK (unless someone pops along to contradict ) Will of course secure the thing extra well - don't want to be messing with it on the road.

[foxyrider]

been doing it for years - saves looking for odd clamp sizes and i can swap mechs around the fleet willy nilly as all the bikes either have a braze on or an adapter.

[drossall]

I've had no problems with mine. Same thing really - a 531 frame that I upgraded from friction shifters to 8-speed and now 9-speed. With the indexed gears, the front derailleurs I got hold of happened to be braze on. No difference in performance from the original band-on one.

[Valbrona]

Never noticed a problem with them.

Campag FDs have been braze-only for years, so it's common to have to use a band adapter.

But I beg the question: Why hasn't Mr Shimano done likewise? I mean at least in the case of road mechs.

[pwa]

Hi folks

I acquired an old mech which I fancy fitting to an 8 speed self build of mine.

It's a braze-on type but I did buy an adaptor to allow me to fit it to my frame.

Before I take the old band-on mech off, I was just wondering if there are any disadvantages or issues with using a braze-on mech with an adaptor rather than just a band-on mech?

Am pretty confident that the braze-on mech itself (an XT) is superior to the cheapo shimano band-on one on the bike at the moment.

When installing a braze-on front mech with an adaptor I found that the adaptor actually makes fine tuning a bit easier. Firstly, you choose how high / low on the seat tube to put the adaptor, and how to angle the mech to get it in line with the rings. But after that you still have the ability to rotate the mech, or move it up or down a little, on the adaptor, without loosening the clamp around the seat tube.

[TheBomber]

Another fan here for braze on mechs with a band adapter - for the reasons outlined by Foxyrider. Although a braze on with adapter might be slightly heavier, and not be quite as elegant as the correct band on model, a lot of band on mechs come in the largest size with shims for skinny frames. I find these particularly ugly.

[Sweep]

Thanks for the encouragement folks.
I used one of these - 28.6
https://www.planetx.co.uk/i/q/FMPXCLAMP ... -sram-yaw)
all went well and I agree with what I take to be the concensus - easier than fitting a band-on with the shims - they look somewhat ugly, make adjustments tricky (the shims can shift) and the band on a band-on is thicker - I was able to fit the XT mech with the adaptor without having to do my usual bodge with presta screw washers to get the bottle cage mounts to clear the band.
Should have started doing this years ago.

[mikeymo]

Another fan here for braze on mechs with a band adapter - for the reasons outlined by Foxyrider. Although a braze on with adapter might be slightly heavier, and not be quite as elegant as the correct band on model, a lot of band on mechs come in the largest size with shims for skinny frames. I find these particularly ugly.

I agree. Shims offend me. I spent a fair while tracking down a NOS 6503 in a true 28.6 clamp on, as opposed to a larger size with shims. I don't know if any current band-on front derailleurs are available with 28.6 clamps.

[peetee]

I have this arrangement on a couple of steel tubes road bikes with Dura Ace 10 speed shifters and they run perfectly.
The only issue I can see is if a later mech is used that has a bracing grub screw. They thread in towards the frame to help support the mech during shifts. It’s possible that the position of the band may compromise or interfere with the set-up of this screw.

[slowster]

I have this arrangement on a couple of steel tubes road bikes with Dura Ace 10 speed shifters and they run perfectly.
The only issue I can see is if a later mech is used that has a bracing grub screw. They thread in towards the frame to help support the mech during shifts. It’s possible that the position of the band may compromise or interfere with the set-up of this screw.

I have a bike with a FD-R2030 Claris 8 speed braze-on triple front derailleur, which has the bracing screw. Providing the derailleur is positioned at the top of the adaptor's slot, the screw will press against the adaptor's clamp rather than the seat tube. Any lower and the point of the screw would bite into the seat tube's paint.

Shimano usually supplied a couple of very small aluminium plates with front derailleurs that used the bracing screw. The plates have a self-adhesive backing and are for sticking to the seat tube to protect it from damage by the bracing screw. One plate is curved to fit narrow tubes, and the other is flat to better fit large oversize seat tubes.

The main downside of all the above is that a bit of the convenience provided by the adaptors is lost. Instead of being able to fit the adaptor and then using the adjustability provided by the slot to get the derailleur the right height above the outer chainring, it's likely to be necessary to raise/lower the adaptor on the seat tube to get the right height, i.e. in the same way that is necessary for a band-on derailleur.

[peetee]

[
The main downside of all the above is that a bit of the convenience provided by the adaptors is lost. Instead of being able to fit the adaptor and then using the adjustability provided by the slot to get the derailleur the right height above the outer chainring, it's likely to be necessary to raise/lower the adaptor on the seat tube to get the right height, i.e. in the same way that is necessary for a band-on derailleur.

Yep. Add in poor positioning of the water bottle bosses on a short frame and it could prove to be a real headache.
I have also struggled to get the correct rotational angle of clamp-on front mechs. Final tightening of the band often causes one hinged side to grip more than the other and the mech rotates a couple of degrees as it followed the closing bolt gap. Braze-on mechs are a godsend in that respect.