Mountain Biking - Different size front derailers?

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h2on0
04-08-06, 02:40 PM
I shopping for new derailers and the front seems to have 3 sizes. 1 1/8" , 1 1/4 , 1 3/8. Which do I need?
http://www.pricepoint.com/detail/13878-105_SRAXG5-3-Parts-57-Derailleurs/SRAM-X-Gen-Front-Derailleur.htm
This is for a 06 rockhopper comp?
Any help and an explanation of sizes would be greatly appreciated
thanks

MiniBullitRider
04-08-06, 03:12 PM
Front derailleurs usually clamp to the seat-tube and said tubes come in different sizes. According to the specialized website (http://specialized.com/bc/SBCBkModel.jsp?spid=12992&bikeTab=techspec) your rockhopper uses front derailleurs with 34.9mm diameter clamps. 34.9mm*(1inch/25.4mm)=1.375 inches=1 3/8 inches. You might also want to note that you need a top swing, bottom pull derailleur. That SRAM claims to be dual pull, so it's probably alright, but I've never used SRAM stuff, so don't take that for gospel.
h2on0
04-08-06, 03:20 PM
Thankyou for your time I appreciate it.

khuon
04-08-06, 03:25 PM
Another thing you will want to be aware of is that front derailleurs sometimes come in different curvatures to match different chainring size ranges. Additionally, there is the issue of chainstay angle. There was a thread on this subject (http://www.bikeforums.net/showthread.php?t=181159) that was discussed not too long ago.
achc
04-12-06, 10:57 AM
u need a , 34.9mm clamp, top swing, bottom pull

top swing means LOW CLAMP!

Bottom pull means the cable is PULL from the BOTTOM INSTEAD OF TOP