dirtydozen

Hello,

I bought a second hand bike that got sent to me from a bike shop.
I went to the LBS to index the FD, 3 different mechanics tried to but it's still not working very well.

The last mechanic told me that the FD was made for 53T, so it can't work with my triple 50-39-30 chainring.
He explained that he was trouble to set the height of the derailleur, he would like to make an adjustment but then I believe the FD touches the big ring while in the middle ring.

The groupset (including chainrings) is Shimano 105 5700.

I have never heard of a 53T or a 50T FD, is this a thing ?

Thanks

rhenning

The bend (curve)in the derailleur cage can be different depending on what it is made for. Road bikes have a bigger curve and mountain bikes a tighter curve which would be appropriate for the chain rings they are shifting. So yes there a derailleurs made for different gearing. Roger

70sSanO

I would’ve more inclined to believe you have a double FD than a 53t FD. I could be wrong but I’ve been able to get a FD to index a slightly smaller chainring.

I don’t use the 1mm/2mm above the large chainring when going to a smaller large chainring. On my wife’s 50t to 46t, I set the derailleur closer to the 50t location; which is a larger gap. When you shift from the middle ring there seems to be an optimum place to shift to the large chainring. So that is what I do. It indexes fine.

I could be wrong, but I’ve done wider gaps on smaller large chainring and it seems to work fine.

John

cpach

Yes, Shimano triple front derailleurs are designed around specific chainring combinations, though they can work OKish outside of spec. To use a triple front derailleur designed around a 53/39/30 on a 50/39/30 means your front derailleur will have to be excessively high relative to the large chainring to still clear the middle chainring when shifted into the big chainring.
https://productinfo.shimano.com/#/search/FD-5703 , click on specifications.

Go buy a matching FD-5703, it looks like they're available online for less than $40 shipped.

Things are wild in shops now I know, but under normal (and current?) circumstances the right call would be to call you, explain the situation, and ask permission to put an appropriate derailleur on order if it's not in stock.

dirtydozen

Thank you all of you guys for your interesting inputs.

On the specs it says :

Top gear teeth : 50T
Total capacity : 20T
Applicable Top-Mid tooth difference : 11T

That looks quite good for my 50/39/30 doesn't it ? I found another link with other specs, but they seem to be ok with 50/39/30 on paper. I'll have a look at other FDs than 105 5700.

https://www.bike-components.de/en/Sh...illeur-p25008/

What do you mean by a double FD ? The FD I have is a 105 5703. I guess a good mechanic could make my set up work with more time to work with than LBS. Actually the LBS managed to index it once, but then the shifter got jammed up and with the new shifter they didn't manage to make my FD work properly, even though I don't see any reason why would replacing a shifter (with same exact model) would change anything.

Litespud

an FD designed for a double crankset, traditionally a 39/53 standard- or 34/50 compact crankset

70sSanO

If you have an FD-5703 on the bike, there something else going on and the LBS doesn’t want to take the time to figure it out. What FD did they suggest? Best one would be the one you have.

Did it work with the 53t?

Dud you buy the bike from them?

John

dirtydozen

Yes, but it wouldn't work on my triple right ? My triple isn't working very well but at least I can go on each of the rings, that wouldn't be possible with a double FD right ?

LBS didn't suggest any particular FD, it's not really a road bike orientated bike shop, they don't sell a lot of stuff and rent bikes for people to go to the beach. I guess I can try another LBS but none of the one I know seem to often work on road bike

My bike is an ex-rental roadbike that a bikeshop sold me via internet, I received it with 50/39/30, but It's obvious that it's not the original chainrings. I also have mismatching crankarms. So I have no idea how FD behaves with 53T.

Litespud

Well, you asked what was meant by a "double FD", which I explained. It's unlikely that a double FD could be simultaneously set low enough to engage the granny gear of a triple crankset, and still be high enough to clear the big ring of the same triple. So triple FDs have a deeper inner cage to essentially "reach down" to the granny gear. But your FD, a 105 5703, is for a road triple, so I can't imagine why it won't work. The tech's reference to a "53" is a bit of a red herring. I interpreted that as meaning a double crankset. Any FD that works with a 53t big ring will work with a 50t big ring and vice versa - the difference in curvature is insignificant. The question is whether a double FD will work with a triple crank, and I would say not, although a triple FD would likely work with a double crank. If you have a 105 5703 FD with a triple crank, there should be no problem. Is your front shifter for a triple?

70sSanO

So you have a former rental bike that has a 50-39-30 triple and it doesn’t shift with the correct FD; and the 53t only exists in the mind of the beach cruiser LBS mechanic and was never on the bike?

With no history, my guess is the cable/shifter. Could be a broken cable end is jamming things up.

I have read that there were some issues with the 5700 brifters, but I’m not sure of the details.

John

70sSanO

What you can do is loosen the cable From the FD and see if the shifter cycles though while holding the loose cable with a little bit of tension. If it hangs up or jams, it is the shifter. If it shifts smoothly it opens up more questions. But as a former rental bike the FD may be damaged.

John

CliffordK

How about some pictures of the current derailleur setup, and attempts to shift. A few different angles.

The 5703 derailleur should be a "Triple".

There are very few 53T "Triple" cranksets. Although, the FC-7703 did use a 53/39/30 chainring set. But, I think Ultegra and below stopped at 52T for their triples.

A derailleur designed for too large of a chainring would tend to have the tail of the derailleur kicked up a bit. That really shouldn't impact shifting a lot, and might be able to be adjusted with mounting shims.

A while ago I was working on an old MTB with a Shimano Alivio front derailleur.





What happened with that derailleur is that the shelf on the top of the derailleur cage would ride on top of the chain when it was trying to lift off of the middle sprocket and trap the chain preventing it from shifting.

My solution ended up raising the front derailleur about 1/4" to present a flat spot to the chain, and not trap it on the sprocket.

I gave that bike away years ago, but it was mighty worn, so perhaps a worn chain also impacted the shifting.

CliffordK

Another thing to look at. Are you using OEM Shimano chainrings? Are the shift pins and gates intact? Worn?

dirtydozen

The problem I had before was often when shifting from the big ring to the middle one, it wouldn't shift and I had to go all the way to the small one and then back up. I ride in hilly terrain so I need to change between big and medium rings a lot, that's why it's frustrating.

I took it to another LBS, the guy was confident in the FD indexing working, I explained to him that a LBS couldn't index it for a compatibility problem he said that was ok.

I tested it this morning on a 4 hour ride and it wasn't really better, the big to medium ring change worked a couple times but still failed 90% of the time. For some reason, bike upside down in my room it shifts nicely ! We'll see how it rides tomorrow..
And now I picked up rubbing chain on the 50x11-13. The guy used the trimming position when in big ring to shift in the big ring, so once i'm there I can't trim and get rid of the chain rub. I could try to correct that but i'm gonna mess everything LBS has set up..





Correct. I changed the cables already, inspected well and then when the LBS attempted they also changed the cables. I don't think the cables are at fault here.
Oh yes 105 shifters have issues and I actually had to replace the one controling the FD a month ago.

It was former rental but the BS selling it put a lot of brand new stuff on it. I can't remember if the chainrings or the FD was new though, but I guess you would put new rings when you put new RD chain cassette

I don't know what OEM chainrings are i'm sorry.

Yes they are intact, they look brand new

I will post photos here soon, but what you describe is not happening. Everything is 105 5700 triple, and according to the specs on their website it's all ok.

fietsbob

Sheltered life?
Road race double typical .. 53 42 30 also a thing..

Issues the Shop guys may be thinking of is Indexing of the left 'brifter' .. it may need replacing too ?
[Blind guessing, (done a lot) here]
the triple has a wider inside plate to shove the chain up from your 3rd / 'Granny' gear..




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