Replacement for Shimano Tiagra FD-4503 front derailleur

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torquerulesok
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Joined: 22 Jul 2013, 1:15pm

Replacement for Shimano Tiagra FD-4503 front derailleur

Post by torquerulesok »

I have run into a problem after replacing my braze-on FD-4503 (the spring retaining nub had sheared off after 20,000km) with a Sora FD-R3030: even after I back out the limit screws all the way the FD won't shift onto the smallest or largest chainring.

The specifications of the two FDs supposedly are identical: chain line 45mm, identical cable pull, chain stay length etc. The FD is correctly aligned, the shifter cable is new. FD/large chainwheel gap is 3mm. Moving the FD up or down makes no difference. My LBS had a look at the installation and agrees that the installation is correct and the Sora should work.

Shifters are the original Tiagra 9 speed, the chainset is a Tiagra FC-4503 triple, all on a 2011 Specialized Tricross.

Before I go on an eBay hunt for another FD-4503, does anyone have any tips on how I could get the Sora to work?

Failing that, the Microshift FD-R353F also should work as its specs are identical, but I'd rather not waste another £25 on a FD that doesn't work with my set up. Has anyone used one successfully in place of a FD-4503?

TIA!
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peetee
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Re: Replacement for Shimano Tiagra FD-4503 front derailleur

Post by peetee »

I understand that people have made these mechs work with earlier gear systems but the fact that the pull arms are different lengths tells me that they shouldn't work at all.
Nevertheless, I will still ask, are you running standard tooth-count chainrings and have you checked the cable routing at the pinch bolt is correct? (It may differ to the previous mech - I can't recall).
Also, if the cable pull tension is significantly greater it might be compressing the existing gear cable outer or causing a related issue that wasn't manifest with the old mech.
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cycleruk
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Re: Replacement for Shimano Tiagra FD-4503 front derailleur

Post by cycleruk »

Can you move it by hand? (disconnect the cable if you have to.)
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torquerulesok
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Re: Replacement for Shimano Tiagra FD-4503 front derailleur

Post by torquerulesok »

I tried that. The Sora simply doesn’t have enough “range”/“travel”/“throw” to move the chain across all three chainrings. The BB is a Shimano Deore Hollowtech II (68/73 BSA). I can adjust the FD so it works for two chainrings but not for all three.

Would a MTB derailleur be an option? I googled but couldn’t find any braze-ons. Can’t really use a band-on because the welded braze-on fitting would be difficult to remove and require repainting afterwards.
torquerulesok
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Re: Replacement for Shimano Tiagra FD-4503 front derailleur

Post by torquerulesok »

peetee wrote: 10 Jul 2024, 4:35pm Nevertheless, I will still ask, are you running standard tooth-count chainrings and have you checked the cable routing at the pinch bolt is correct? (It may differ to the previous mech - I can't recall).
Also, if the cable pull tension is significantly greater it might be compressing the existing gear cable outer or causing a related issue that wasn't manifest with the old mech.
The chainrings are the original ones.
I downloaded the manual from Shimano’s website to check the pinch bolt routing - it is correct.
The cable pull tension feels no different to the original Tiagra FD.
fatboy
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Re: Replacement for Shimano Tiagra FD-4503 front derailleur

Post by fatboy »

Have you routed the cable right on the front mech. I've been caught out by not going over the small shoulder on the pull arm.
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Chris Jeggo
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Re: Replacement for Shimano Tiagra FD-4503 front derailleur

Post by Chris Jeggo »

torquerulesok wrote: 10 Jul 2024, 10:23pm I tried that. The Sora simply doesn’t have enough “range”/“travel”/“throw” to move the chain across all three chainrings. The BB is a Shimano Deore Hollowtech II (68/73 BSA). I can adjust the FD so it works for two chainrings but not for all three.
suggests to me that
peetee wrote: 10 Jul 2024, 4:35pm I understand that people have made these mechs work with earlier gear systems but the fact that the pull arms are different lengths tells me that they shouldn't work at all.
might be a clue to what is wrong.
Cyclothesist
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Re: Replacement for Shimano Tiagra FD-4503 front derailleur

Post by Cyclothesist »

I think peetee has it. The FDR 3030 design looks like it's one with a long lever arm, like the Tiagra FD4700. They need a longer cable pull than the short arm front derailleurs. It's the first time I'd considered that while Shimano 9 speed (or less) rear derailleurs are cross compatible, that may not hold true for front derailleurs.
Hopefully someone with more knowledge of FD compatibility will confirm or refute this.
torquerulesok
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Re: Replacement for Shimano Tiagra FD-4503 front derailleur

Post by torquerulesok »

Update: This morning I uninstalled the Sora FD and started the installation again from scratch, including a new cable - just to be on the safe side.

Following the instructions provided in Shimano's dealer manual to the letter I finally got the derailleur to shift to all three chainrings, although there still is a bit of rub when the chain is on the large chainring and on one of the three outermost sprockets, despite the outer limit screw being all the way out.

I think @petee and @cyclothesist are correct when they surmise that the root cause of the problem is the length difference of the lever arms. I probably need only one millimetre of additional outward travel to eliminate the chain rub. However, I'm reluctant to take a Dremel to the chain guide outer plate.

I'm going to ride it for a month or so to check whether things might improve. If not, I'll have a look for a replacement FD-4503.

Thank you to all who chipped in with ideas!
Brucey
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Re: Replacement for Shimano Tiagra FD-4503 front derailleur

Post by Brucey »

FWIW I have repaired several FDs with broken 'nubs' like that. The method I used was to drill a small, angled, blind hole into which I then epoxy resinned a short length of spoke. I think my repair might be a lot stronger than it was originally.
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Cyclothesist
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Re: Replacement for Shimano Tiagra FD-4503 front derailleur

Post by Cyclothesist »

Brucey wrote: 11 Jul 2024, 1:45pm FWIW I have repaired several FDs with broken 'nubs' like that. The method I used was to drill a small, angled, blind hole into which I then epoxy resinned a short length of spoke. I think my repair might be a lot stronger than it was originally.
Ingenious! Now that's got to be worth a go. What's to lose?
Brucey what did you do to get the spring on the correct side of the epoxied nub?
Brucey
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Re: Replacement for Shimano Tiagra FD-4503 front derailleur

Post by Brucey »

Cyclothesist wrote: 11 Jul 2024, 2:42pm.... What's to lose?.....
exactly
Brucey what did you do to get the spring on the correct side of the epoxied nub?
if you are very strong/lucky you may be able to manoeuvre it using needle-nosed pliers. However, it is probably best if a special tool is made.

A suitable tool can be made using a strip of beer can, folded to make a tiny square section tube. The tube can be reinforced at the ends by using what I call 'superwhipping' (thread plus epoxy resin) or even 'ultrawhipping' (epoxy resin again, this time in conjunction with very thin metal wire). If you remove just one strand from a brake or gear cable, this is almost ideal for 'ultrawhipping'.
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Cyclothesist
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Re: Replacement for Shimano Tiagra FD-4503 front derailleur

Post by Cyclothesist »

Thanks Brucey. Now I remember you suggesting fashioning a similar tool for manipulating the spring when I was renovating a seized old Tiagra FD.
torquerulesok
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Re: Replacement for Shimano Tiagra FD-4503 front derailleur

Post by torquerulesok »

Brucey wrote: 11 Jul 2024, 1:45pm FWIW I have repaired several FDs with broken 'nubs' like that. The method I used was to drill a small, angled, blind hole into which I then epoxy resinned a short length of spoke. I think my repair might be a lot stronger than it was originally.
Great tip! I'll try that before I buy another Tiagra.

How did you manage to move the end of the tension spring past the new "nub"? I found it very difficult to move when I had a look at whether I could fashion some sort of repair.
Brucey
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Re: Replacement for Shimano Tiagra FD-4503 front derailleur

Post by Brucey »

torquerulesok wrote: 11 Jul 2024, 5:21pm.......How did you manage to move the end of the tension spring past the new "nub"? I found it very difficult to move....
it is mainly a matter of having the correct tool; since the repair can have good strength even before the epoxy resin has cured, the spring can be manipulated prior to adding the 'nub' if necessary. You can use PTFE tape as a barrier layer eg. between the tool (which can be left in place whilst the glue cures) and the new 'nub' to prevent adhesion.
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