ziqpy

Sram 53/39 w/ 11-28 rear.

Mocking up the front derailleur, and there is little up and down movement during the pivot.

This means I can't clear the 53T sprocket, and get enough drop on the 39t, so the chain doesn't rub the bottom of the cage?

As i'm running bar end shifters, is there a front derailleur for 10 speed you can buy with a longer cage?

I might have fitted it wrong, but every time it will chew into my alloy frame, going to coke can and have a play see where i get.

Any suggestions?

ziqpy

As Low as it can go, nice expensive waste of time

Is there any front dérailleurs with longer plates, so the tail will go under and clear the chain?

badrad

Is the FD designed for road cranks? It looks like you are using a mountain FD to try to clear the road crank, which is why you are not getting the clearance.

Check out some of the SRAM road FD, and you can see the difference in the two types.
https://www.sram.com/sram/road/compo...nt-derailleurs
https://www.sram.com/sram/mountain/c...nt-derailleurs

ziqpy

SRAM Rival is all road only.

badrad

Couldn't see from your photo and you didn't provide any other info. Sorry couldn't be of more help.

LWaB

Moultons often have a tapered spacer between the braze-on front mech and the braze-on mount to move the mech rearwards and rotate it anticlockwise. This correctly orientates the mech for the chain angle (the hub is lower than on a 700C bike). You could do something similar.

Hinge

I was just about to say the same thing.

Here's a link to give you an idea:

Angled Wedge Spacer

I agree, this is very strange. Nothing in you setup appears out of the ordinary. It should work flawlessly.

When you installed the FD, what is the clearance between the outer edge of the cage and the top of the large chainring? Is it roughly 1mm?

ziqpy

Do you end up running the front a little higher angle and space the overall height by the rear of the derailleur?

I would still have to buy a new derailleur with spacer and mount.

about $75 to fix, if it works

Hinge

I'm not sure I understand your question, but the shim actually angles the FD counterclockwise slightly. Ideally it would lower the rear of the cage just enough to provide clearance for the chain when you are in you 11T cog. You would still set your FD by lining up the outer edge of the cage parallel with the large chainring and making sure the bottom of the front of the cage is as close as possible to the tops of the teeth without touching.

I don't think you should have to buy a new FD and mount. The spacer goes in between your existing front derailleur and mount. It should be a relatively cheap solution to try. SRAM and Rotor make these spacers.

This link will give you an idea how it works. In the video, there are 3 spacers sizes. I would suggest one of the smaller 2 sizes, not the big one. The video is aimed at users of oval rings, but you'll get the idea.

https://blog.artscyclery.com/ask-a-me...ailleur-setup/

With all this being said, it seems odd that you should have to do this. Your setup seems as standard as can be.

I wonder if this is an inherent issue due to the frame's geometry.

What is the frame?

fietsbob

You have additional tweaks with a braze on adapter band + a braze on FD.

that may let you adapt to what may be an unusually steep seat tube angle..

Via, wedges , rotationally, where the FD bolts to the adapter .. [Do you DIY any?] dropping the tail of the cage will increase the clearance..
fot rghe lower chainring.

ziqpy

well i have a bolt on not braze on atm, why it's a $75 fix

dynaryder

I did a quick Google search;there's plenty of Bomas out there with front ders,so it does work. From the pics I saw,they looked like they were angled up a touch,more in line with the seattube,than yours. Might want to do some Googling and ask other owners what they did. FYI,most of the pics I saw looked like Shimano ders;might be just enough of a difference between them and SRAM to work better for this application.

jur

Due to geometry difference between smallwheelers and road bike the fd has to be angled 13deg bacwards, ideally.

smallwheeler

you rang?

i don't know if 13ş is universally true but, on the boma f-1 below, the fd certainly appears to be set back and differently angled than the OP's nearly-one-year-on-and-still-unfinished bike. incidentally, that's what my friends say about me - "who, him? oh, he's alright. he's just.. "differently angled"."

also, OP, let's wrap this up, bruv. it's not even my bike and i'm getting anxious to see a result. this bike needs to be on the streets by 1 march. there - you've got a deadline now.

Hinge

Maybe you actually need the extra large spacer I referred to previously. It looks like this and would set the FD back and down a fair amount.

jur

AFAIK, there are only derailers in existence designed for large-wheeled bikes. So while front derailers work just fine on limited range gearing setups, once you start pushing the boundaries, the chain starts dragging on the bottom of the cage due to the fact that cage bottoms were designed for slightly sloping-up chains to the rear, while with small wheels the chain slopes down.

jur

I basically made a spacer almost exactly like that, not knowing that these exist. After I found out about them, I thought they were rather expensive.

Eprobungs

I think you need to find an FD offset adapter + a braze-on FD.
OR get Microshft's FD-R42H which has the offset built in.
microSHIFT -The best control system

jur

Not sure you're right there. I haven't seen anything in the specs that suggest the rotational offset needed. On the contrary, this one as well as the other road ones all have the chainstay angle spec'ed at the same value. So I'm fairly sure this would be a waste of money.

ziqpy

BOMA | PRODUCTS | ALUMINIUM BIKE FLAT-1

This is the website link in Japanese for the frame.



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mconlonx

Would a derailleur built for a triple work? Seems like it might have a slightly longer cage, to accommodate the small ring up front. I'd be tempted to go get a cheap one just to find out, like a Shimano Claris FD-2403 or Sora FD-3403/3503.

ziqpy

well i contacted my LBS where i bought my front derailleur and blagged swapping it for a braze on, which are cheaper anyhow, and mine is still unused.

I'll pop round and swap it later today.

30 bucks saved, So I was going to mock up a spacer out of coke can. I can't figure the life of me how you'd mill one.

The spacers ain't cheap for what they are...

fietsbob

File a couple wedge shaped pieces out of aluminum stock You just have to Rotate the FD a Bit , then tighten the Bolt .

It Does not have to be as Fancy as Shown in jur's picture .. a hand file is way less than a Milling Machine , even when you add the cost of a Bench Vise..

jur

Yep I filed it. But if you don't have stock material, files and drill bits then buying it will be cheaper.

fietsbob

I've seen 2 even smaller wedges 1 above and 1 Below doing the Rotation of the FD, CCW, trick

maybe folded up Beer can will do