2014 Trek Fuel EX-8 Fork problem

I picked up a 2014 Trek Fuel EX-8 29-er about a month ago and I'm not too happy with the front fork. It feels really harsh through chop and breaking bumps at speed. Almost jarring. I have the sag set correctly and I've played with the rebound, but still can't tune this out. Anyone else out there with the same bike have this issue? Fox said I could send it back and they would check it out for me under warranty, but I really don't want to be without a bike for a couple of weeks. The fork is the Fox Evolution Series with DRCV, CTD dampner. I know it's a XC bike, and I don't expect it to be all mountain, but it should handle the chop I would think. Any advice would be great. Thanks!

 

Darn... it sucks to be put in the situation that keeps you off two wheels. I've been in similar situations, and I find that I always eventually end up sending the part to the manufacturer and/or vendor. During the downtime, I've ran used, or cheap new parts (think eBay) to keep my bicycle(s) operational. I've come to the point where borrowing close friend's bikes who barely ride is more convenient for everyone. I have a nice bike to ride, and I clean/adjust everything before returning. :lol:

 

If you wanna troubleshoot it, here are a few things to check:

1) Are you in Climb mode? Test the other modes. If there is no difference, get the fork checked by Fox.

2) Is the rebound set too slow? Packing the fork causes harshness. Try speeding up the rebound. When you compress the fork and quickly release the bars, the handlebars should just almost catch up with your hands as you pull them away. That is a base measure. Actual rebound setting should be done on the trail.

3) -Deflate the fork fully and see if you can push the fork the entire 120mm of travel.
-If you can't get full travel even with a good push, I suspect the fork is over filled with oil in the damper section.
-Pour out the oil from the top, and refill with the proper volume.

3) -Check if the compression knob is detached from the compression valve.
-Swing the knob to full open.
-Pump the fork.
-Swing the knob to mid setting.
-Pump the fork.
-Swing to close.
-Pump the fork.

If there is no difference in the settings, you likely need to have the fork check by a service center.

Something to consider. The Evolution series dampers generally have port orifice valves for compression control. Those things get choked up in high frequency chatter and high speed square edge hits. You could replace it with a FIT damper, which is better than what you have.

 

Problem=DRCV

I found it almost impossible to get my Trek with DRCV to work correctly on both the chop and bigger stuff. Fixed the problem by replacing with normal CTD Fork and Shock.

Good Luck!!

 

I have a DRCV rear shock on a Remedy. Ive got no complaints. I have a different fork though.

 

Thanks for the input everyone. I will run through those troubleshooting tips tonight and see what it does. Fox did tell me that they could upgrade to the Fit dampner for $200-$250. I've rebuilt my dirt bike forks before(fluid, seals & bushings). Is the fit dampner upgrade something that can be done easily or is it a service center job?

 

It's easy just drop it in and fill it back up

 

Just to be clear, the DRCV is in the airspring. The Evolution is the damper.

 

DRCV just seems like Trek's way to add more support in the midstroke through the air spring, which aggressive riders want for hitting berms hard and to keep the front end from diving excessively, for less reliance on LSC. The first chamber gets progressively stiffer around the point the fork's travel reaches midstroke, then opens up the second chamber. To someone expecting something predictably smooth, this might come off as spiky and harsh. I'd personally run no more than the recommended sag, perhaps even less (maybe 20%), due to the spring's position sensitive nature.

I also would've suggested speeding up rebound as fast as you could, to avoid packing up, but bing went further. Follow his advice. I wouldn't expect much from 120mm fork to erase bumps, especially one designed for racing/speed, as opposed to a fork made more for comfort. I have 160mm forks that still feel chattery, that are highly regardly like the Pike and BOS Deville. On the other hand, oddly enough, my 100mm Reba RL with Dual Air makes the trail feel like marshmellows, but that's not my style, as I like the hardpack to feel hard and bumps to feel like bumps, rather than soft sand and rock sized marshmellows. Perhaps you would prefer something like the Reba RL, or maybe a Marz 44 RC3 Ti? It certainly offers a more comfortable ride over my Fox stuff, feeling like an extension of my tire's absorption ability, but sometimes it makes my tire feel flat and isn't the most controlled at speed.

 

hello, can you explain the concept behind this test and what i'd look for when doing this test? Thanks!

 

The evolution damper compression knob controls a valve attached via a shaft. It can happen that the knob is not actuating the valve, which can be caused by a few reason, hence no difference in fork action. Ive seen it where valve sheared from the shaft.

If the valve is stuck, the fork may be hydrolocking.

Not in the og posters case, but the knob not locking out the fork can also be due to low oil levels.

 

No spiking here. I'm actually on my second drcv bike. Thats with the rear shock only though.

 

Did the troubleshooting tips and everything is working properly. I'm going to try running the 20% sag and work with the rebound settings some to see if it gets a little better.

 

Where was your sag? I recommend 17-22% to people I help. The steeper the head angle, the more sag. If bottoming becomes a problem, bring up the compression to compensate.

 

The Sag meter that came with the bike has a recommended range of 20%-25%. I've been running it within that range, but closer to the 25%. I geared up last night and set it up at 20% and will try it tonight after work.

 

After determining that the fork is in good working order, let's try to adjust it.

Making the spring stiffer probably will make the ride harsher.

Try changing things one at a time.

Devote an entire ride into setting up your suspension. Go to the section of trail that is giving you problems.

Stick to 25% sag and first try rebound. Not very familiar with the new Evolution dampers, but try setting rebound 20-30% away from the fastest setting. On a 16 click scale, I'm about 5-6 clicks from fastest (absent of a better way of giving advise online, doing it this way).

Try that and see how it goes. I suggest keeping rebound as fast as you can, short of hearing the front wheel dribble on chatter.

Put the fork in descend mode. Turn off all compression. If you have that second flat knob flush below the lockout, that's it. That is a blowoff valve for the lockout. Turn that off. Using the lockout as compression control, being that its a port orifice, has a tendency to cause hydrolocking. Add only as much compression using the lockout that removes the sensation of too much brake dive. There should be some brake dive, but not so much that you feel like your going to go over.

Beyond that, the only thing I can think of that does not require major surgery is to change oil to 5wt.

Good luck!

edit: Jenson is blowing out their Fox 34 FIT 29er forks for 600

 

Set the sag right under the 25% line and started with the rebound six clicks out from the fastest setting. It's like a whole new bike. Felt way better. It was just fully loop, but the couple of down hills were night and day better than before. Thanks for all the help! Beers are on me if we ever meet.

 

Don't forget that you can run lower tire pressure too. I found that my 26x2.4 Ardent can go as low as 15 psi, mounted up front and under my bony 140 lbs arse. Quite a noticeable difference from ~20 psi, which I previously thought was acceptable. Didn't know I was running lower for a couple of rides until I hooked a pump back up to it, pumped it up back to 20, and found that my traction and comfort was lower on that ride--if I didn't know better, I would've thought it was cause the trails got some rain, and had finally dried up.

Actually did a tire pressure test on my ride this afternoon, dropping pressure in my tires for the second lap. I thought I rode smoother and better overall on my 2nd lap, and felt more like my first lap was a warm-up. I become more aggressive, loosening up my legs and feeling my knees spread more naturally to react to the terrain, but apparently I got slower. Since my body and riding felt a lot better, I can only conclude that lower pressure worsens rolling resistance on my loop, which is mostly loose-over-hard, with a few sandy parts and nothing more than ruts and rocks (most avoidable) for major bumps. It was more comfy with more traction, to say the least.

 

Im glad that worked. What was happening was that your fork was packing down. Your fork rebound was slow enough that it kept the fork legs from extending before the next hit. Soon after, you are just too deep in the stroke or just run out of travel which causes the harshness. The interesting thing about this phenomena is that as soon as you stop, your fork extends

Check your rear shock rebound too. The drcv rear shock has about 5-6 clicks. At 165 pounds, I like it at 4 clicks from slowest. Less clicks (slower) for heavier riders, more for lighter. The rear shock should be slightly slower on rebound than the fork.

note: when setting drcv air pressure, be sure to pump the fork and shock to equalize the pressure chambers, and set again.

i like beer.

 

Thanks, I've been doing that as well. I'm 200 lbs geared up, so I can't go as low as you without possible rim damage. I'm tubeless, so I don't have to worry about pinch flats.