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-   -   Chain/derailleur compatibility (https://www.bikeforums.net/bicycle-mechanics/901802-chain-derailleur-compatibility.html)

biCYCLOTRON 07-16-13 10:25 AM

Chain/derailleur compatibility
 
I've got a trek 2000, and it is a 2x6. The chain is 7.3mm. My previous derailleur broke and I was considering upgrading to an Ultegra 6600 front. Would modern 10 speed derailleurs work with this? Just to be clear, I'm replacing the front derailleur and wondering if I would have any compatability issues. The bike's previous derailleur was a sora and it broke with about 20 minutes of use. Old Front is a shimano 3400 fd, and current rear which works fine is a shimano 1050 rd.

rhenning 07-16-13 11:13 AM

I believe you need to stay with 9 speed and below rear derailleurs for them to index correctly. Front derailleurs shouldn't make any difference. Roger

Airburst 07-16-13 11:18 AM


Originally Posted by biCYCLOTRON (Post 15856656)
The bike's previous derailleur was a sora and it broke with about 20 minutes of use.

Sounds like it was mounted too low and snagged on the chainring teeth, I don't know any other way to break a front derailleur. Properly fitted, you shouldn't have any trouble with Sora stuff, and you're unlikely to notice a difference between a Sora and an Ultegra FD while you're riding.

biCYCLOTRON 07-16-13 11:18 AM

I was concerned with the chain clearance in the cage. I'm worried that the chain is too wide for the modern setup. I wasn't worried about indexing as I have downtube shifters and I can just set them to friction. The old derailleur got stuck and stopped shifting. I was going to upgrade it anyways.

FBinNY 07-16-13 07:30 PM

Front derailleurs (especially indexing front derailleurs) are actually more sensitive to chain width than RDs. The issue is chain clearance within the cage, which is the difference between cage inside width, and chain width.

Put a wide chain into a narrow cage and you'll be trimming like crazy to adjust for the incoming angle change when you change the rear. Or put a narrow chain in a wide cage and you'll have lots of lost travel with every shift, and if the difference is enough the index system simply won't move the cage enough.

The issue with RDs is clearance between the cage plates, and there's some forgiveness since the chain is kept centered by the pulleys. RDs with floating upper pulleys may experience some chain/cage rubbing during a shift, but if the underwidth isn't extreme, this is a rarity.

The other RD cage issue is entry angle at the bottom where a chain coming on an angle may rub on entry. This is easily fixed by filing inside clearance at the front bottom of the cage.

Andrew R Stewart 07-16-13 08:31 PM

The OP says his system is a 2x6 and the levers are friction able. Since the main concern with narrower ft der cages and index shifting (which SO MANY WHO POST seem to only know) is a mix of der stroke, chain width, ring c-c and chain rub; a friction ft der lever will reduce this possible problem. The narrower cage the intended with the 7.3mm chain can, to a degree be simple trimmed. There are many reasons that a ft der cage breaks, replace one today at work. But poor set up and jam shifting are often involved. Andy.

biCYCLOTRON 07-17-13 08:05 PM

Thanks guys! I got the ultegra derailleur.


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