Quantcast

Trek Session8/88 Tuning

chillindrdude

chillindrdude

Turbo Monkey
Jan 18, 2002
1,852
23
Northern VA, a peckerwood with too many guns
Is there enough riders here to warrant this thread?

I could use some tuning help for rear suspension setup. I've got a large 09 Session with the DHX 5 shock. I am running about 30% sag with the stock 450# spring (with 2 full turns of the preload collar).

How much compression and rebound are fellow riders running? I feel I am bouncing off the bike in long rock garden sections. And I'm not sure if less compression and/or more rebound is the answer.

Is it worth while to upgrade to the RC4 or CCDB for this frame?
 
davec113

davec113

Monkey
May 24, 2009
419
0
Bouncing might be rebound too fast. I have a L and am running a 500 lb spring with 100 lbs in the air can and the adjuster backed all the way out to full volume. The suspension seems very progressive, so I could see issues if you were running small air volume with a lot of pressure in the can. I had a dhx5 on my last frame and I always ran minimum air pressure, and it seems like nobody likes the dhx with more than minimum amounts of air pressure.

FWIW, Trek did have the dhx custom tuned for this bike. A local pro has a Session 88 and has tried a few shocks. He said he is not a big fan of the dhx in general but thought it felt really good on the Session. I am having no issues at all with mine, the rear sus seems perfectly behaved and very predictable.

Also, a 500 lb spring will give you more control in the mid-stroke, which could help.
 
N

Nozzes

Chimp
Mar 10, 2009
22
0
Upgrade to...spending a little time turning the dials on your shock!!!
I don't really believe you bounce off rocks with the rebound on the slower setting,and if you do,your spring might be the problem.I weight 65kg,and run a 400lb spring,with 55psi of air,don't ask me about how many clicks on the rebound,usually I use 2 clicks in for the Propedal,no clicks for really rough courses.
The DHX5 on the Session 88 is specially tuned for this frame,and really works.You just have to get the right spring for your weight and...experiment.

Good luck
 
IH8Rice

IH8Rice

I'm Mr. Negative! I Fail!
Aug 2, 2008
24,524
494
Im over here now
Nozzes said:
I weight 65kg,and run a 400lb spring,with 55psi of air,don't ask me about how many clicks on the rebound,usually I use 2 clicks in for the Propedal,no clicks for really rough courses.
Click to expand...
how many times have you had to warranty the shock with 55psi in it?
 
J

J

Monkey
Dec 7, 2003
437
0
San Luis Obispo, CA
I'm interested in how others are setting up their RC4's on the Session. I've dinked with mine but I'm still not happy. Does anyone have some advice or perhaps a starting point?
 
W

wiscodh

Monkey
Jun 21, 2007
833
121
303
J said:
I'm interested in how others are setting up their RC4's on the Session. I've dinked with mine but I'm still not happy. Does anyone have some advice or perhaps a starting point?
Click to expand...
Med, 180lbs

350, 150psi, rebound to taste of the trail, almost full low speed, mid range high speed.

Thats what i came to like at the end of the year. Im sure right away i will turn down the low speed, or how fat i get over the winter put on the 400lbs spring.

Hack riding style :P
 
J

J

Monkey
Dec 7, 2003
437
0
San Luis Obispo, CA
wiscodh said:
Med, 180lbs

350, 150psi, rebound to taste of the trail, almost full low speed, mid range high speed.

Thats what i came to like at the end of the year. Im sure right away i will turn down the low speed, or how fat i get over the winter put on the 400lbs spring.

Hack riding style :P
Click to expand...
Oh wow, I need a softer spring then (with the RC4 in case others are reading...) I'm 180 also but I have a 450# on there now and wasn't sure if I should get a 400#. I guess it seems like I should go down to at least a 400. Is it normal to run that much low speed?
 
Last edited:
J

J

Monkey
Dec 7, 2003
437
0
San Luis Obispo, CA
chillindrdude said:
i'm 190-195lbs with full riding gear on. and riding a DHX5 with a 500# spring. is that an appropriate spring weight? how do you adjust compression damping on the DHX?
Click to expand...
Trek used to have a PDF linked from the Session's page with advice on the DHX tuning. I printed it out a while back and could scan it later if more people need it. But, for your weight, 190lbs, it recommends the following:

190 lb rider:
Fox DHX Coil 5.0
450# spring (right below needing a 500# spring, if you were at the 200lb mark for rider weight)
Rebound: 8 clicks out
Propedal: 4 clicks in
Boost Valve: 175psi and Mid volume mark
Fox 40 RC
Blue spring (M)
Low comp: 8 clicks out
High comp: 10 clicks out
Rebound: 8 clicks out

I want the RC4 chart to come out! Since they took down the old DHX 5.0 chart down I'm guessing it'll be up soonish?
 
Last edited:
Downhill.Ben

Downhill.Ben

Chimp
May 18, 2009
22
0
Newcastle, England
Not my settings, but my brother's...

He weighs 86KG, with kit (That's 190lbs)
Using the TFTunes spring calculator, he should be running a 450lbs spring, which we are.

This might be very handy for you guys - http://www.tftunedshox.com/info/spring_calculator.aspx

On a standard track we run about 135 PSI in the Boost Valve, 4clicks of rebound damping (Ie. 4 from fastest) and 4 or 5 clicks of compression damping (again, 4/5 from fastest).
For Bottom out resistance, we run "1 Line" up from the bottom, so 1 third bottom out resistance.

The bike pedals so well, that from the ProPedal side of things, there's not really any need to run ProPedal atall. But, on take-offs (Ie. slow-speed compression) the bike tends to over-compress. Hence, we run 4/5 clicks of Pro-pedal. Admittedly, not what it's meant for specifically BUT it works in the same way.

The other thing I'd have a look at is bottom-out resistance and the pressure in the Boost Valve. We've found that as you increase the Boost Valve pressure, with less than half B-O resistance, the suspension really ramps up in later stages. With more than half B-O resistance, it is a lot less obvious. You're not meant to run the shock with no pressure, but we did one section with next to nothing in the shock and it felt awful. Bashing thrugh the travel until the BO resistance kicks in is not the way to go!

Hope this helps.

Ben
 
W

wiscodh

Monkey
Jun 21, 2007
833
121
303
J said:
Oh wow, I need a softer spring then (with the RC4 in case others are reading...) I'm 180 also but I have a 450# on there now and wasn't sure if I should get a 400#. I guess it seems like I should go down to at least a 400. Is it normal to run that much low speed?
Click to expand...
yeah, with the rc4 you can really go down an incriment of 50 beacuse the boost valve acts like a little air spring. I belive socket had a whole write up about it. I went with the 350 beacuse at the begining of the year i was down around 165.....I got fat ok??? GET AWAY FROM MY PIE!

That is why i have alot of air in the boost valve.

I dont know if its normal to run that much low speed. But i like it, helps me skip over stuff and not get stuck in holes at speed. If i was just freeriding in a bike park, i think i would turn it down. Beats you up.
 
chillindrdude

chillindrdude

Turbo Monkey
Jan 18, 2002
1,852
23
Northern VA, a peckerwood with too many guns
hmm...i'm running a 500# spring right now and i feel like its sitting pretty deep into the travel when i'm riding. the shock stroke is 2.75"...so to calculate 30% sag, basically i'd want to see ~0.83" of eye to eye distance change, right?

i still need to play around with the boost valve and psi. i feel like the DHX is not as tuneable as the RC4. but i think i'll make due with the DHX 5 and the Session until next april. My next frame will be the Turner DHR
 
You must log in or register to reply here.
Top Bottom