# Bicycle Mechanics: A question about front derailleurs **URL:** \ **Category:** Factual Questions\ **Created:** [June 13, 2007, 5:59pm UTC](https://boards.straightdope.com/t/bicycle-mechanics-a-question-about-front-derailleurs/407881 "2007-06-13T17:59:09Z")\ **Posts on this page:** 6\ **Page:** 1
**Author:** ![Dragwyr](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dragwyr/32/2855_2.png) [@Dragwyr](https://boards.straightdope.com/u/Dragwyr)\ **Post date:** [June 13, 2007, 5:59pm UTC](https://boards.straightdope.com/t/bicycle-mechanics-a-question-about-front-derailleurs/407881/1 "2007-06-13T17:59:09Z")
Bicycle Mechanics, I need your help. I need a new front derailleur for my recumbent (A 2005 CycleGenius CGX Starling). In [This post on the “Ask the Bicycle Mechanic” thread](http://boards.straightdope.com/sdmb/showpost.php?p=8250161&postcount=70) **Chasing Dreams** answers my question about why the replacement derailleur the bike shop put on it wasn’t working quite right. The answer was that the components on my bike are all SRAM 3.0 and the derailleur the bike shop put on was a Shimano, which wasn’t quite compatible. So I basically need to get another SRAM 3.0 front derailleur . My question has to do with the part itself. I don’t find the exact same replacement part anywhere. Most SRAM 3.0 parts that I do find won’t fit because the mounting bracket is larger than 28.6 mm, which is what the tubing on mine is. I’ve found other SRAM front derailleurs that will fit on a 28.6 tube, but they are not 3.0 models. Will that make a difference? My shifters are SRAM 3.0, but if I get a [SRAM X7](http://www.pricepoint.com/detail/15772-105_SRA7H7-3-Parts-720-Sram-MTB/Sram-X.7-Front-High-Derailleur-'07.htm) which will fit on a 28.6 tube, will it work ok with the 3.0 shifters? Thanks in advance for any help on this. ---
**Author:** ![Busy\_Scissors](https://avatars.discourse-cdn.com/v4/letter/b/d78d45/32.png) [@Busy\_Scissors](https://boards.straightdope.com/u/Busy_Scissors)\ **Post date:** [June 13, 2007, 9:23pm UTC](https://boards.straightdope.com/t/bicycle-mechanics-a-question-about-front-derailleurs/407881/2 "2007-06-13T21:23:10Z")
Hi **Dragwyr** , I ride mountain bikes and don’t use sram, so I won’t waste your time with speculating on the compatibility of the front der etc. But you could shim the 3.0 and it would be OK. Say if you could pick it up in 31.8 a shim would work fine. In fact, looking on CRC (where I get all my stuff) it seems like you can get the sram 3.0 front der with an adapter for a 28.6 seattube: [See here](http://www.chainreactioncycles.com/Models.aspx?ModelID=6199) ---
**Author:** ![capybara](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/capybara/32/202_2.png) [@capybara](https://boards.straightdope.com/u/capybara)\ **Post date:** [June 13, 2007, 10:11pm UTC](https://boards.straightdope.com/t/bicycle-mechanics-a-question-about-front-derailleurs/407881/3 "2007-06-13T22:11:08Z")
Bike mechanic SO says for the front the X7 should work (not the back, however,or “maybe”). Something about X series parallel-pull blah blah. ---
**Author:** ![Dragwyr](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dragwyr/32/2855_2.png) [@Dragwyr](https://boards.straightdope.com/u/Dragwyr)\ **Post date:** [June 14, 2007, 1:00pm UTC](https://boards.straightdope.com/t/bicycle-mechanics-a-question-about-front-derailleurs/407881/4 "2007-06-14T13:00:10Z")
**The Cocky Watchmen** : We tried shimming a 3.0 that I had bought, but it kept sliding down the tube when we would shift gears. **capybara** : Thanks for your response. I feel a little better about considering the X7 then, especially if the front der will work fine. My next question is should I try to install it myself, or should I get a bike shop to do it? ---
**Author:** ![50million](https://avatars.discourse-cdn.com/v4/letter/5/9fc348/32.png) [@50million](https://boards.straightdope.com/u/50million)\ **Post date:** [June 14, 2007, 4:04pm UTC](https://boards.straightdope.com/t/bicycle-mechanics-a-question-about-front-derailleurs/407881/5 "2007-06-14T16:04:13Z")
I just went to the webpage for the manufacturer of your bike. They list it as having a 52 tooth front chainring. When I went to the page for the X.7 front der. that you are thinking about purchasing it lists its max capacity as 44 tooth. Having a 52 tooth chainring means you need to look for a road bike front deraileur, not a mountain bike front deraileur. I’m guessing you still have the Grip-Shift system on the bike. That would mean that you have a nearly infinite “trim” capability with the front shifter. That means you can use just about any brand of front deraileur. The three things you need to make sure of are, clamp size (which you already know), max tooth size (which you now know), and whether or not it’s “top pull” or “bottom pull”. Your bike is bottom pull, by the way. I would take it to the local shop and let them diagnose/fix it. It may seem cheaper to do it yourself, but by the time you buy the X.7 and send it back because it won’t work for your 52 tooth chaninring, then buying another front der. but you accidentally bought a top pull and have to send it back, all the while not riding your bike, it’s cheaper just to go to the shop. Plus, adjusting a front deraileur for a recumbant triple is going to be a HUGE pain in the ass. Trust me on that last one. All that being said, I hope you get it fixed quick and get back on the road. ---
**Author:** ![50million](https://avatars.discourse-cdn.com/v4/letter/5/9fc348/32.png) [@50million](https://boards.straightdope.com/u/50million)\ **Post date:** [June 14, 2007, 4:25pm UTC](https://boards.straightdope.com/t/bicycle-mechanics-a-question-about-front-derailleurs/407881/6 "2007-06-14T16:25:15Z")
Sorry about the double post, I missed the edit window by about 3.5 seconds. I read your post again and checked out what \*\*Chasing Dreams \*\* told you. He’s correct about the whole 2:1 / 1:1 thing. But that _might_ not be your particular problem. Go to your local shop, have them adjust it. If they can’t make it work ask them to try with a different front der. If that works then you’re fixed. If they can’t make a new front der. work then find out which shop has the best mechanics, it may not be the one with the fanciest display window. Front deraileurs are deceiving, they seem like they should be the easier of the two, but they are definitely the more finicky to get quite right. That’s why I said in my earlier post that you should just take it to a shop. Hope that helps.