Front derailleur problem for Epi...solved
Its funny, i eventually did pose this question to the 'everything drivetrain' forum as well and got zero responses.
While musing over this for a while, i realized that it did not make sense, if the chain was rubbing on the bottom of the front der, that this would be more prevalent while seated than standing. To prove this i deflated my shock and moved the rear end through its travel while noting the relative position of the chain to the front der. Not surprising, it moves upwards (ie. farther from the bottom of the front der cage).
So, it was not hitting the bottom of the cage but most likely the bottom part of the outer cage, where it juts inwards (towards the back of the der). I just realized while typing that i probably could have fixed the whole problem by moving the front der up the seat tube instead of down....duh
This still wouldnt solve the trim problem though. I did some searching about X-gen front der and found that apparently it was specifically designed for use with twist-shifters (which have trim capability). However, SRAM apparently claims that it will work fine with X7, X9 and XO. Seems that most people who spec SRAM triggers use Shimano front der. So kudos to RockyRider who nailed that one.
I just happened to have a spare LX top swing lying around with the right clamp size. So i popped it on (BTW it feels like its half as heavy as the Xgen). After less than 5 mins of adjusting, I can now get in EVERY gear combination with no rubbing. Parking lot test verified this. I will trail test this weekend.
thanks for all of your input.
thumbies (i think i will keep the handle/ alias for a while longer....just in case
Time is not a road.
It's unfortunate, but SRAM hasn't mastered the front derailleur yet. I'm running an XT front with X.0 twisties. The trim ability is great.
What's really ironic is...
...that i was just in the local bookstore tonight, browsing the bike mags when i came across the new MBAction issue. In it theres a section of tuning your shifting in 5 minutes. So i figure why not take a look, after all of my troubles.
Turns out that the test bike they use for the pics is an Epiphany, (the Blue Marble paint was a dead giveway). Upon further investigation i noticed that the front der was an X-gen. And an even closer look showed a crank with a 44 tooth big ring. What really blew me away was that the der was mounted with somewhere on the order of 7-8 mm of clearance above the big ring....coincidence? I'm guessing that they had the same problemms on this Epi that i was having (grinding in granny) and their compromise was to push the der pretty high up on the seat tube (way beyond SRAM's specs).
heres a pic of the mag cover in case anybody is interested in checking out the article.
FWIW, my local shop mounted my front derailleur (X-Gen) quite high on my Truth. Having just replaced the drivetrain on my road bike, I called and asked why. I was told that because of the rear suspension and its effect on the height of the chain, the have found that shifting works best when the FD is mounted high. I have no idea, but it shifts just fine.
over 50 years of cycling
SRAM XGEN Front + Epi......BAD combo
OK, I am a believer....Apologies for any snide remarks I made!
I took my brand new Epi out for its "First Mud" today, with the bike shop settings.
I requested SRAM front derailleur , to do my small part to break the Shimano Monopoly, and I always toss the big ring in favor of a bash ring. The shop kindly obliged on both requests for the new bike setup.
So I hit the steep technical stuff, dropped it into the small ring and every time I hit a bump I heard a NASTY metallic CLUNK. Couldn't SEE any problems and the sag was all to spec. After a few more scarey clunks on my brand new bike I grabbed a tree and bounced up and down trying to figure out the clunk until I saw shiny aluminum where there should be black anodized. YIKES!!!!!
Turns out that HUGE inner plate on the inside of XGEN was grinding into and hanging up on the frame under load and would snap back when unloaded. I did a trail side tweak and raised the XGEN about an inch to get it to clear and then had to play with it to avoid the scraping as described in the previous posts. I will see how this works out, otherwise I will swap it with an old shimano from one of my other bikes.
So yes indeed, it appears the Epi is not REALLY compatible with a SRAM front derailleur. Bummer.
Photo attached of trailside cage relocation and part of the scrape. Luckily the scrape is in a section of solid aluminum and isn't a notch so it only REAL damage is that "first scratch" effect on my psyche.
Now I am regretful...
...last week i serviced my shock (RS MC 3.3) and after i reinstalled it but before i added air, i thought i would do a little investigation into the actual travel that my Epi gets. Remember Ellsworth touts that the Epi is 5, 1/4" (133mm). I wondered how they actually measure that...the problem is point of reference. Finally i decided on flipping the bike upside down and measuring the relative elevation between the dropout and the top of the seat (ie. the floor) by using a drywall square...you can see this setup in the first picture with a zoom in on the unsprung elevation in the second picture (21, 1/2"). Then i pushed down on the back wheel and compressed the suspension as far as i could....
To my great surprise it bottomed out hard at 26, 3/8" for total travelof 4, 7/8 " (124mm). On further investigation, i noticed what it bottomed out hard on: The bottom of the front derailleur on top of chainstay (der in small ring).
If any of you have been following my front der woes, i recently switched from an X-Gen to a LX. The LX is setup withing specs with about 3 mm clearance between the der and the big chainring (44t). In this configuration there is 2.5, 2.6 and 3.2 mm between the bottom of the der and the top of the chainstay for the small, middle and large chainrings respectively.
Theoretically, if 124mm of dropout travel = 26 mm of chainstay travel at the front derailleur (330 mm back from the dropout), then 133mm = 28 mm....so i have to move the der up 2-3 mm before bottomed-out suspension clears the front der....i wonder how that will affect shifting performance???
I fear that if i had posted this discovery earlier that i could have saved Twisted Trail some heartache.
I would recommend that the rest of you Epi owners take a quick second and measure the distance between the bottom of your front der and the top of your chainstay. By my measurments, the minimum clearance should be 28 or 29 mm.
BTW, the eye to eye measurment of my shock, unsprung but in place on the bike is 198 mm, the stroke is supposed to be 51 mm...i dont know how this compares to the RP3, RP23, or Float R...it will surely make a little difference.
I hope some of you Epi owners can post your measurments and comments as well....
over 50 years of cycling
Ellsworth design Oooops
Hey, thumbies, having read of your problems was part of why I was able to track down the problem before MORE damage was done. So Thank you!
Originally Posted by thumbies
Definitely interesting if both the SRAM and the Shimano derailleurs cannot be set up to spec on the Epi. Bit of a design "Oooops" eh, Mr. Ellsworth? I must say that is a bit upsetting.
My trailside tweak resulted in the der cage being 36mm above the chainstay for me.(I just checked with a set of calipers.) But then I was guessing on the height and still am since I haven't deflated the shock yet to figure minimum clearance. I also noticed that I have 21mm clearance above the bash guard to the cage, which looks a bit funny, but to SRAM's credit, its still shifting fine.
I was just rolling over some tiny bumps when I gouged my frame. I STRONGLY recommend Epi owners to check their front derailleur cage clearance at MAX TRAVEL before they take any Big Hits, which could get REALLY ugly.
dam, the Turner folks will have a field day with this one....
over 50 years of cycling
How to adjust fr. der. height on the Epi
..."I would recommend that the rest of you Epi owners take a quick second and measure the distance between the bottom of your front der and the top of your chainstay. By my measurments, the minimum clearance should be 28 or 29 mm"....
I just had a garage session with my Epi, following Thumbies lead of deflating the shock and seeing how far the derailluer has to be above the chain stay.
With my "Ellsworth tuned" Fox Float R and SRAM XGEN front derailleur, I come up with about the same 29-30mm clearance of cage to chainstay with air, to clear under full compression. ( I like a millimeter or two of breathing space). I also notice the front "nose" of the inside plate comes VERY close to the front pivot and it was also scraping when the derailleur was adjusted to spec, and it just BARELY clears at 30mm when in the small ring.
I can't really blame the shop for the scraping problem, since they did have it set up per spec and it didn't show up until it was in the small chainring and under trail usage. This is just not a problem you expect to find on a frame of this quality.
OTHER than that though, I am indeed thrilled with the Epi and it looks like it will work just fine with a high riding front derailleur.