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Clamp-on vs braze-on front derailleurs

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Clamp-on vs braze-on front derailleurs

Old 05-07-19, 06:05 AM
  #1  
morri869 
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Clamp-on vs braze-on front derailleurs

Somehow I find myself with a shortage of front derailleurs for my current build and I have been giving thought to the merits of each fd style.

I currently have a braze-on front derailleur but not a clamp that fits the bike I'm building. So do I buy just a clamp or get a clamp-on front derailleur? I'm thinking just a clamp gives me the most versatility without damaging the frame paint as much, but it doesn't look as clean. What other opinions are out there?
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Old 05-07-19, 08:03 AM
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I'm not a fan of braze-on front derailleurs. They limit the range of chainring sizes you can use and put a heat affected zone on the thinnest part of the seat tube (I've seen can-opener type failures when the chain gets jammed and twists the front derailleur). The only place they make sense is for non-round seat tubes. IMO, that is.

Regarding your specific issue, as I understand it you want to use a clamp to adapt a braze-on design front derailleur to a bike with a round seat tube. In that case, it's your call. The third-party adaptor clamps I've seen tend to be pretty ugly, but I suppose they could be cheaper than a new clamp-on front derailleur.

Last edited by JohnDThompson; 05-07-19 at 08:06 AM.
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Old 05-07-19, 08:10 AM
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I like clamps better for their flexibility. You can add a chain keeper, etc. Next time I pull apart my Lemond I'm going to paint the clamp the downtube color and enhance the braze-on derailleur.
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Old 05-07-19, 12:01 PM
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I like just having the separate clamp.
Versatility.
They even come in colors, too.
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Old 05-07-19, 12:12 PM
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Consider clamp on Adapters to use Braze on Front derailleurs... ?

Less Ugly?
K-edge, CNC made in USA , .. FD may be combined with their chain catchers ..


Last edited by fietsbob; 05-07-19 at 12:21 PM.
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Old 05-07-19, 12:13 PM
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IMO- front derailleurs have clamps- the tabbed frames are the outliers- I haven’t owned a frame with a derailleur tab- but I have used a couple of Origin 8 braze on adapters for braze on derailleurs- I think they’re ugly and ungainly.

I’d rather use a non- matching clamp on derailleur.
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Old 05-08-19, 07:12 AM
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Originally Posted by JohnDThompson View Post
I'm not a fan of braze-on front derailleurs. They limit the range of chainring sizes you can use and put a heat affected zone on the thinnest part of the seat tube (I've seen can-opener type failures when the chain gets jammed and twists the front derailleur). The only place they make sense is for non-round seat tubes. IMO, that is.

Regarding your specific issue, as I understand it you want to use a clamp to adapt a braze-on design front derailleur to a bike with a round seat tube. In that case, it's your call. The third-party adaptor clamps I've seen tend to be pretty ugly, but I suppose they could be cheaper than a new clamp-on front derailleur.

From the back of the church Amen...

I am not a fan and it became evident with my recent exercise in attempting to get one to work on my SOMA. Clamp on derailleur did the trick but the braze on / adapter just would not work no matter what I did . I tried multiple braze on derailleurs from my bin with no success.
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Old 05-08-19, 08:53 AM
  #8  
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Clamp all the way. Next question ... .
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Old 05-08-19, 11:22 AM
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I don't want anything clamped onto my frame if it can be brazed on...

except for my front derailleur for all the reasons already mentioned above.
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Old 05-08-19, 01:28 PM
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All the braze-on front derailleur fitting I can remember working with were designed for use with 52-tooth or 53-tooth big rings and worked poorly, if at all, with smaller big rings.
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Old 05-08-19, 02:04 PM
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Originally Posted by JohnDThompson View Post
I'm not a fan of braze-on front derailleurs. They limit the range of chainring sizes you can use and put a heat affected zone on the thinnest part of the seat tube (I've seen can-opener type failures when the chain gets jammed and twists the front derailleur). The only place they make sense is for non-round seat tubes. IMO, that is.

Regarding your specific issue, as I understand it you want to use a clamp to adapt a braze-on design front derailleur to a bike with a round seat tube. In that case, it's your call. The third-party adaptor clamps I've seen tend to be pretty ugly, but I suppose they could be cheaper than a new clamp-on front derailleur.
When the brazed on front mech' arrived, Campagnolo furnished a stamped mount to braze on with the unit. Bad design, with it or the initial bikes so fitted from the factory, it was alarming how much everything flexed under shifting load to the big ring. SLX tubing and investment cast mounts that captured a longer arc of the tube made everything tolerable.

I agree, the ring range declines with a braze on.
Some overzealous mechanics can dent tubes with too much clamp bolt torque...
Then there were the French... those metric tubes could have a clamp bottom out before fully tight...
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Old 05-08-19, 03:44 PM
  #12  
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Braze-on Derailleur Attachments

I have a number of frames that I bought that take braze on FDs. I've had to modify in some way every one of those braze-ons to get proper FD alignment. For example, I run 50T, 49T or 48T large chainrings on most of my bikes. The braze-ons are positioned for 52T or 53T with room to go larger.

Up through the mid to late 70's very few braze-on "tiddly bits" (Brit term not mine) were used on better quality production frames. One of the reasons for that was lower skilled employees assembling frames could easily overheat thinner walled tubing.

BITD most production frames were made of Reynolds 531 Sprint and Columbus SP tubing with 1mm x 0.7mm wall thickness main tubes. By the mid 70's high end Italian frames and bikes started appearing in the US market in greater numbers.

They had more and more braze-ons which drove the market and the other bike makers joined the fray. By then many better quality frames were being produced with lighter gauge tubing Like Columbus SL and others with 0.9mm x 0.6mm or thinner main tubes.

Braze-on FDs became part of that movement. It was also part of the weight weenie fantasy and later the aero era.

As @JohnDThompson mentioned, the brazed on FD mounts could result in seat tube failure where a clamp would have had little or no effect. One reason why the splined or riffled bottom section of Columbus SLX seat tubes was so long was to give reinforcement in the braze-on area.


Other things that contributed to the problem: someone put the seat tube in upside down with the butt at the top or they trimmed the tube length at the wrong end leaving a short butted section. It HAPPENED!

Reynolds tried to make it simple:


The clamping point for most derailleurs is about 6" to 7" above the BB center line with 52T or 53T chainrings. Reynolds seat tubes had a 3" (75mm) long butted bottom section with a 2" (50mm) long tapered section; so 5" plus about 3/4" for the BB places the clamp or braze-on at the top of the butted section into the thinner area.

When they first came out, Campagnolo was the only derailleur manufacturer that made the braze-on style and they were in short supply for maybe a year. DOH!

I thought that it was a stupid design and looked ugly! But... even the likes of Huret succumbed to the idea!



The ultra rare Jubilee braze-on FD.



There was one worse short lived idea, Simplex (of course). They used a water bottle style braze-on in the seat tube with their own proprietary style FDs.



Not opposed to the idea of braze-on mounted FDs but the concept was poorly executed with little flexibility for changing cranks, chainrings and so on.

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Old 05-08-19, 03:54 PM
  #13  
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I'll be the "Devil's Advocate"...every frame I've ever owned had a braze-on FD tab. I run 50t large chain rings, exclusively. Never had a problem with getting it to shift properly. My Masi once threw a FD shifting fit. I put a new derailleur on and problem gone. I guess my vote in favor of the braze-on is the only one.
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Old 05-08-19, 05:40 PM
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I've had only one bike with braze-on front derailleur, an early '90s Trek 5900 (maybe classic, not vintage). The Shimano 600 Tricolor FD it's wearing has no up/down adjustability. For a month I've been riding that bike with old school Biopace 52/42 chainrings, those sorta squared-end ovals.

No shifting problems, despite the rings changing effective diameter. I've used it with downtube shifters (friction only on the left/FD) and brifters -- MicroShift, with the indexed left/FD shifters with click-stop in-between shifts for trimming out chain rub.

Based on a sample of one, I have no complaints. But I'm more familiar with clamp on FDs, and those can be tweaked slightly to compensate for any odd shifting problems. Can't do that easily or at all with braze ons.
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Old 05-08-19, 06:55 PM
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Nice, used FDs are cheap and plentiful. I can't see the point in spending money on an adapter.
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Old 05-08-19, 07:11 PM
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I cracked my 1987 Bianchi frame, in 1988, where the front derailleur braze-on was attached to the seat tube. Get a clamp-on.

When you decide that 53/48T crank is a little too unforgiving, you can just slide that derailleur down the seat tube, and put a 28/14T crank on like the rest of us.
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Old 05-08-19, 08:53 PM
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Regarding the Simplex brazed on boss FD mounting system, it wasn't bad at all if only it was not snubbed by other bike makers other than Peugeot and Gitane (The Gitane pros had them on their race bikes). I have the suspicion that Simplex did not handle the marketing, or lack of it, when they had it in their groups. A situation made worse when Mavic came out with their own standards (Maybe just to slight the Spidel Group?) for brazed on FD mounts in the mid 80's. If only the two companies worked together to come up with a true standard for a French brazed on FD mount, we would have seen more competition between the Italian standard and what Mavic and Simplex had (I think the French system presented a stronger, more reliable design than the brazed on tang that the Italians had.)...
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Old 05-09-19, 10:30 AM
  #18  
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Problem Solvers makes adapters that look way better than the Origin8 ones, IMO... About the same price (~$15 Shipped).
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Old 05-09-19, 10:41 AM
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I like braze on mounts. Of course, it's a little tricky to decide what gear range I'm going to use on a particular bike, but I don't change that very often. It certainly would be different if I wasn't putting them on myself
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Old 05-09-19, 10:50 AM
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Originally Posted by gearbasher View Post
I'll be the "Devil's Advocate"...every frame I've ever owned had a braze-on FD tab. I run 50t large chain rings, exclusively. Never had a problem with getting it to shift properly. My Masi once threw a FD shifting fit. I put a new derailleur on and problem gone. I guess my vote in favor of the braze-on is the only one.
I'm terrible at setting up/adjusting the FD. A braze on (assuming you're using standard sized chainrings) decreases the number of directions you have to worry about adjustment for, so it makes it a little easier for crappy mechanics like me.
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