Mountain Bike Reviews Forum banner

1 - 11 of 11 Posts

·
Registered
Joined
·
18 Posts
Discussion Starter · #1 ·
I have a 2013 Specialized Stump Jumper FSR Comp/29 with a Fox Float CTD Evolution rear shock/autosag. When I purchased it I was unaware that the shock was setup from the Fox factory with a compression tune setting that is specific to your weight. Currently my shock is set to compression setting L (Low). The sales guy should have considered this.

Problem: I am bottoming out my shock too often and am experiencing too much flex when it’s set to the climb mode. I am 210lbs with all my riding gear.

After talking to my LBS mechanic I now know the shock is set to L and should be ridden by someone who is closer to 150lbs. The correct setting for me considering my weight and the terrain I ride should be Medium (M) or even High (H). The compression setting can be changed but only when it’s sent off to Fox for service and I’m not ready to do that considering it’s fairly new.

Question: What can I do to compensate for the compression setting until it’s time to service the shock?
My thought is to increase the psi in the shock. Autosag sets it at 160psi and I have been experimenting with running it between 160-200psi but I also do not want to damage the shock by over inflating it. Is there a chart or guide which I could look at that considers my weight and recommends a psi? Does anyone else have any suggestions?
 

·
Registered
Joined
·
55 Posts
to the first issue of the compression setting of your rear shock. It is not tuned to rider weight as you say. Specialized would have to stock to many different configurations of each bike it carried. Instead MFG's set the tune of the shock based on the bike configuration. Your bike is set to a low tune because it does not have that much pedal feed back when torqueing down ie you do not get that much bob. Bikes with a Medium or High tune have more issues with that and compensate for it with a higher tune. You will notice also that a locked out (climb mode) on a low tune shock will feel completely different then one with a high tune. Your specific bike was made for a low tune and has nothing to do with your weight. You ultimately need to set your sag better then the auto sag specialized used (which I never did read any review that says it works, all set it differently) Your shock will have a number on it that if you called FOX they could tell you what the max PSi rating is. Each tune will be different. Next play around with the rebound to see if that helps. And if all that fails then I would go with the Volume air spacer as JoFa73 has suggested. Hopefully that helps explain things a little better.
 

·
DFMBA.org
Joined
·
1,874 Posts
I'm about the same weight as the OP and the Fox shock on my Camber is set around 200. My experience with autosag wasn't that great so I just set it manually.


Sent from the trails.
 

·
Registered
Joined
·
18 Posts
Discussion Starter · #5 ·
interesting, so all the comparable Stump Jumpers come with that L set rear shock. I wonder what my LBS was talking about saying the factory could reset it. With what you are saying they wouldn't advise I do that with my model.
I will look into the max psi and just increase the psi and rebound until it works better for me.
Would the volume air space decrease my travel? As of now it's a 130mm shock.

Thanks
 

·
Registered
Joined
·
55 Posts
jofmon your LBS is right to the point that the factory can change the tune for you to whatever you want. It might actually be right for you. It will definetly stiffen up the ride for you. But it could also act bad also on the bike that wasn't designed for a higher tune. Adding a volume air spacer will not change the travel but it will change the small bump feel to the bike. At a low tune your small bump sensitivity is prolly pretty good. My guess is you should play around with your sag try 20% or 25% for your weight, I would think at 30% you might find it too plush but to each rider it feels different. I have a low tune shock on my Pivot mach 5.7C and for a while I felt it was too plush and wanted to stiffen it up doing the same thing by going to a medium tune. In the end all I had to do was go from 30% sag to 25% and it felt way better from the get go. Cheap and easy fix. You just have to try different things until it feels right. I would think that you are not bottoming out with that much psi in the shock. What makes you think you are?
 

·
Registered
Joined
·
18 Posts
Discussion Starter · #7 ·
So "bottoming out" is not the best word for it. I don't feel my shock hitting its limits but my rear tire is rubbing my saddle bag on drops (that arn't crazy) but small ruts when my weight is on the seat and it's set to climb mode. That's a pretty big distance for the suspension to give in that mode when I don't have a brain. The rubber ring moves to the max position just about every ride I do. Also just casually testing the shock in climb mode by bouncing shows alot of movement that I wouldn't expect. The worst though is my crank and pedal strikes going over terrain as I pedal. I have to really be careful with my rotation by looking out for rocks. Often if I leave my outside pedal down on a curve with rocks, I'll clip my crank. I know the 29er has a lower bottom bracket but my thinking was the shock was giving too much, that my weight was exceeding its capability. 160psi/20% just isn't cutting it though so I'll add more air. I have it up to 180psi now and guess I still need to add more to try to compensate.
 

·
Registered
Joined
·
55 Posts
Always go 5-10 psi more when filling shock There is some pressure built up in the line that you think is in the shock that is not. So if you want 180 psi go to 185-190. Also what sag are you running. and are you setting your sag in Descend mode? You have to set sag in descend and with as much weight as you ride in.
 

·
Registered
Joined
·
166 Posts
Jofmon, Did you ever get your shock figured out? Did you try those air spacers? I have a '14 SJ FSR Comp Evo 29 and I don't think that the shock supports those air spacers. Let me know what you did to solve it.
 

·
Registered
Joined
·
4,671 Posts
Call up Fox, tell them your bike model and rider weight (geared up) and they should be able to offer a recommendation. Why compromise and get something that you might not end up liking. Just do it right, you'll enjoy the ride way more.
 

·
Registered
Joined
·
18 Posts
Discussion Starter · #11 ·
I found that my solution was to increase the psi up to 200 and that seemed to resolve my issue so I never got as far as to really looking into the spacers. #1 lesson, don't just go with the autosag.
 
1 - 11 of 11 Posts
Top