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Front derailleur & large chainring

post #1 of 7
Thread Starter 
Hello all, I am fairly competent on bike mods & repairs but am struggling here.

I have fitted a 53 tooth chainring on my 9 spd Triple chainset on a Trek road bike. My smallest chainring is 30 teeth, so I need 23 teeth capacity on the derailleur. The current derailleur is a Sora triple but this only has 20 teeth capacity and worked fine on the std 50 teeth ring but not the 53T.

After some trials, the Sora will not work so keen to buy a new front derailleur but struggling to find what I need. I have emailed some of the main online cycle stores but no response. I would like to keep the 30T ring for climbing and the 53T for flat riding. The downtube is 35mm dia and a clamp on fixing.

Other people must be running similar set-ups and would appreciate any advice or help so i can get back on the road. Thanks in advance!
post #2 of 7

Re: Front derailleur & large chainring

Quote:
Originally Posted by paulbcycling View Post
Hello all, I am fairly competent on bike mods & repairs but am struggling here.

I have fitted a 53 tooth chainring on my 9 spd Triple chainset on a Trek road bike. My smallest chainring is 30 teeth, so I need 23 teeth capacity on the derailleur. The current derailleur is a Sora triple but this only has 20 teeth capacity and worked fine on the std 50 teeth ring but not the 53T.

After some trials, the Sora will not work so keen to buy a new front derailleur but struggling to find what I need. I have emailed some of the main online cycle stores but no response. I would like to keep the 30T ring for climbing and the 53T for flat riding. The downtube is 35mm dia and a clamp on fixing.

Other people must be running similar set-ups and would appreciate any advice or help so i can get back on the road. Thanks in advance!
Get a 6503 FD, assuming you have a 42t middle ring. That is, Ultegra triple FD, make for 52/42/30, but wll work fine with a 53. 6603 is made for a 52/39/30 and the deep inner cage will hit the middle rimng when on the large ring.

IF the middle ring is a 39t, get a 6603 FD.
post #3 of 7
Thread Starter 

Re: Front derailleur & large chainring

Peter, many thanks for the very prompt advice and part nos. I will check the middle chain ring size tonight and order the necessary tomorrow. Much appreciated. Kind regards Paul
post #4 of 7

Re: Front derailleur & large chainring

Quote:
Originally Posted by paulbcycling View Post
I have fitted a 53 tooth chainring on my 9 spd Triple chainset on a Trek road bike. My smallest chainring is 30 teeth, so I need 23 teeth capacity on the derailleur. The current derailleur is a Sora triple but this only has 20 teeth capacity and worked fine on the std 50 teeth ring but not the 53T.

After some trials, the Sora will not work so keen to buy a new front derailleur but struggling to find what I need. I have emailed some of the main online cycle stores but no response. I would like to keep the 30T ring for climbing and the 53T for flat riding.
I presume your cassette's smallest cog has 12t ...

If that is right then you may want to simply restack your current cassette with an 11t as the smallest cog OR replace your current cassette with one whose smallest cog has 11t.

You may be finding that the chain drags across the trailing edge of the front derailleur's cage when your chain is on the Granny + the smaller cogs ...

BUT, you may have found that the chain probably does not make contact with the trailing edge when you are actually using the Granny + the larger cogs on your cassette ...

SO, you probably shouldn't fret about the front derailleur's theoretical capacity ...

UNLESS you have the very bad habit of running with the chain on the Granny + the smaller cogs.

BTW. You will be inviting more unwanted headaches if you were to put a 6603 front derailleur on your bike -- the 6603 is a 10-speed front derailleur & its cage plates are closer together -- proper indexing with your 9-speed components will be almost impossible to achieve.
post #5 of 7
Thread Starter 

Re: Front derailleur & large chainring

Alfeng

Thanks for the info. I will hold fire on the 6603 at the moment.

I never use the medium - small cogs on the rear cassette when on the 30T front ring. The only use at all for the 30T is for very sleep climbs when I use the largest 2-3 rear cogs.

I still have the problem that the current SORA FD has a 50T max chainring use and I am running a 53T. I can live without using the small rear cogs on the 30T but use the 53T and middle 39T alot across the range.

Is there not a Shimano FD that with work with the 53 or 52T large ring and middle 39T but would also allow the use of the large rear cogs when on the 30T?

Thanks in advance
post #6 of 7

Re: Front derailleur & large chainring

Quote:
Originally Posted by paulbcycling View Post
I never use the medium - small cogs on the rear cassette when on the 30T front ring. The only use at all for the 30T is for very sleep climbs when I use the largest 2-3 rear cogs.

I still have the problem that the current SORA FD has a 50T max chainring use and I am running a 53T. I can live without using the small rear cogs on the 30T but use the 53T and middle 39T alot across the range.

Is there not a Shimano FD that with work with the 53 or 52T large ring and middle 39T but would also allow the use of the large rear cogs when on the 30T?
Despite the conventional misconception, ALL Shimano front derailleurs will work with a 53t outer chainring & a 39t inner-or-middle chainring.

Shimano is very conservative with regard to stating what their components are capable of coping with ...

I guess that

someone (maybe, in Shimano's Tech sheet!?!) once incorrectly stated that a 48t (?) was the largest chainring which a Shimano MTB front derailleur could handle -- it's just not true -- and, that misinformation has been repeatedly echoed ever since.

I have one bike set up with a top pull XT front derailleur + a regular Road Double crankset which currently has 52/39 chainrings at the moment ... sometimes, I change the outer chainring to a 53t and I subsequently need to move the derailleur higher on the seat tube OR lower if I later put the 52t-or-smaller chainring back on.

The misinformation about the capability of Shimano's MTB front derailleurs has apparently been replicated with regard to your SORA front derailleur.
Your Shimano SORA front derailleur can be used with a 53t outer chainring & a 39t inner-or-middle chainring.

BTW. I use Campagnolo shifters with my Shimano derailleurs/cassettes/etc., so idealized ramping on the outer chainring isn't required for efficient shifting (Shimano had/(still has?) 'A' & 'B' ramping which are supposedly idealized for 42t & 39t inner chainrings, respectively).

If you find that the shifting is balky, then consider selling your current Shimano shifters on eBay AND THEN buying a set of Campagnolo 10-speed (non-QS!) shifters -- the 10-speed Campagnolo shifters will mimic Shimano's 9-speed indexing if you use the hubbub.com alternate rear derailleur anchoring (at 3 o'clock vs. 6 o'clock).
post #7 of 7
Thread Starter 

Re: Front derailleur & large chainring

Thanks again for the detailed advice. I have gone for a new cassette with a 11 tooth smallest cog and will fit the original 50T ring back on the triple chainset as I need to get the bike back on the road to keep training.

In due course I will try again with the 53T ring (if needed after trying the new cassette) and will try different FD heights etc. to try to sort. I agree with your comments ref. Shimano tech sheets, it seems to conflict and be inconsistent. Maybe this helps create demand for sales of more bike bits?!

Thanks again.
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