Mountain Bike Reviews Forum banner
1 - 20 of 27 Posts

·
Happy when not-last.
Joined
·
221 Posts
Discussion Starter · #1 ·
I have somewhere between 25% and 33% sag and I feel like I bottom out on medium size hits. I'm 205lbs and running at about 190psi.
On one of the trails I ride there's a bridge with 3 steps up and 3 down. I approach with some speed, lift up the front wheel, [CLUNK] and bottom out almost every time. On the way off the other side I'll often hop off instead of ride down and that's bottoming me out too. It's maybe a 2-3 ft drop onto flat. I'm not entirely graceful, but I'm certainly not graceless either. When the rear wheel hits the stairs I try to shift my weight forward and up to the front wheel, I land barely rear first when getting off the other side.

At the same time I'm not using all the travel in the front. -
Could this mean I need to shift my weight forward via a longer stem and moving the saddle up? I've put the pressure in the rear up to 200psi and it still, barely, bottoms out: should I try 205psi (my weight)?

I feel like something must be set up wrong or I'm doing something wrong, the bike should be able to chew up these stairs without flinching... right?
 

·
Registered
Joined
·
752 Posts
or stop lying about your weight...


(sorry, it was right there, couldn't resist - but seriously - weigh yourself with your gear on - if you're a pack rat, your camelbak can easily add 5-10 pounds)
 

·
Registered
Joined
·
8,308 Posts
Ro.nin said:
or stop lying about your weight...

(sorry, it was right there, couldn't resist - but seriously - weigh yourself with your gear on - if you're a pack rat, your camelbak can easily add 5-10 pounds)
I weighed mine with 3L of H20 in it....13lbs!

But realistically, if he is setting sag WITH gear on at 25% and still bottoming, he needs to look at a smaller air can or a coil shock with some end-of-stroke dialability.
 

·
MTB Monkey
Joined
·
339 Posts
You might want to check to see if you have enough Float fluid in the main chamber. Adding half a pillow pack (about 2ccs) will make the shock more progressive. Do you have the regular or large volume chamber? What is the compression damping setting (the little bar chart on the side)?

I'm about 200lbs, and I had to add a little fluid to my RP23, but I have it working pretty well now at about 185psi. This is with the standard chamber, medium compression shock. But I will eventually Push it and have them add a little more high and low speed compression damping.
 

·
Happy when not-last.
Joined
·
221 Posts
Discussion Starter · #6 ·
Thanks everyone for the replies!

crisillo: I'm worried about loosing the small bump compliance if I put the pressure too high... is that a legitimate concern? Am I asking too much that it can handle a few stairs / drops as well as the small rocks and roots of smooth xc?

Ro.nin, CharacterZero: ha! I actually weighted myself at 205 on a good day, but I never though of adding my riding stuff. 3L of water and cloths will put the suggest pressure around 193psi... I suppose going up to 200 isn't that much of a stretch.

Jefe74: How do I check for fluid in the chamber? I have the standard chamber (med compression), I've thought that's the best way to go considering they design the bike around it (RP23). Adding fluid will decrease the volume, that's how it makes it more progressive...? I think that's exactly what I want: more progressive compression... but don't air shocks strive to be linear like coils?
I will eventually get it Pushed, once I know exactly what I want and when I'm down to my target weight...
 

·
Super Moderator
Joined
·
20,810 Posts
MinskyBA said:
Thanks everyone for the replies!

crisillo: I'm worried about loosing the small bump compliance if I put the pressure too high... is that a legitimate concern? Am I asking too much that it can handle a few stairs / drops as well as the small rocks and roots of smooth xc?
It's matter of striking a balance..that's why I recommended to go in small increments.... but yeah..you will have to find a compromise between the 2...
 

·
Registered
Joined
·
890 Posts
I assume you have the regular volume can. If not, and you currently have the high volume can, you can switch to the regular can and get a far more progressive feel and action. careful on adding too much float fluid/lube...a bit too much and it can actually pool and the bottom and blow your seal out on a hard landing.....seen it happen in two cases where the guys put a whole pack in.
 

·
half tread will travel
Joined
·
240 Posts
hey MinskyBA, u can manage bottom out with a combination of increased air pressure and adjust the air volume down by adding mass directly into the air chamber with a couple of 50mm x 2mm O rings... u can air up 2 match your weight with gear on and then start adjusting air volume down 2 get proper sag...other options r 2 slow down...or speed up and hop the whole dang thang...that's 1 hard hit your setting up 4....b careful...
 

·
Happy when not-last.
Joined
·
221 Posts
Discussion Starter · #11 ·
Jefe74 said:
You might want to check to see if you have enough Float fluid in the main chamber. Adding half a pillow pack (about 2ccs) will make the shock more progressive. ...
Can anyone tell me what's involved with checking / adding?
Do I just remove the shock, twist off the main cylinder and add some lube? Isn't there some sort of factory-set air charge in there or something?
Anything I need to worry about mucking up?
 

·
MTB Monkey
Joined
·
339 Posts
BlueMountain said:
careful on adding too much float fluid/lube...a bit too much and it can actually pool and the bottom and blow your seal out on a hard landing.....seen it happen in two cases where the guys put a whole pack in.
This is a good warning. It does not take much. But if you are bottoming out as much as you say, it sounds like it might be actually low on fluid. Also, I guess too much fluid could cause some to migrate through the port to the negative chamber. That is why the o ring approach is a nice idea.

You don't even have to take the shock off to open up the main chamber. Just mount the bike so shock is at least at a 45 angle with the air valve toward the top. LET OUT ALL THE PRESSURE, then untwist the chamber. It is only hand tight. Then pull it back. There will be some "spring" due to the IFP, but it is easy to hold back. You should be able to see a puddle of float fluid inside. Add half a pack then tighten it back up, charge it up with your pump, and give it a go.
 

·
Registered
Joined
·
1,265 Posts
Minsky, sounds like you are hitting a G-Out coming into this section of your trail. Is this accurate?

Its virtually impossible to stop a bike from bottoming in a G-Out, without compromising every other performance area.

One thing that can really help you is technique. Attack the G-out with your weigth forward coming in, and pump it just like you would when you are in between dirt jumps, transfer your weigth from front to rear as you go through the G-out. Your bike will be very compressed, front and rear, but you will be perfectly in control.

Hope this helps.

Dave
 

·
Registered
Joined
·
1 Posts
I've had the same issues on my mojo. On the rear shock, I found out that it was "stuck down". Just go to an LBS and they can check this for you. In terms of getting full travel from the fork, I initially ran much lower than recommended air pressure, but that led to excessive "brake dive". I eventually sent the fork to PUSH for a rebuild and a high volume air piston upgrade. Now it rides great.
 

·
Registered
Joined
·
1,059 Posts
Have you tried the Oring thing?
I was wondering if I can use the same trick o a Rp23 HV sleeve... I would like to run less sag "higher off the ground to stop me bashing my peddles." and hope the high volume sleeve still allows me to use full travel ... if I bottom out to much I can add the Rings accordingly.

Your thoughts?
 

·
half tread will travel
Joined
·
240 Posts
DH_WP said:
Have you tried the Oring thing?
I was wondering if I can use the same trick o a Rp23 HV sleeve... I would like to run less sag "higher off the ground to stop me bashing my peddles." and hope the high volume sleeve still allows me to use full travel ... if I bottom out to much I can add the Rings accordingly.

Your thoughts?
4 pedal hits use high volume tires at least 2.3s...and practice timing your back pedaling as u approach an object u may hit...

u may play with the sag height but just maybe compromising the overall balance designed...

yup, this is the inside scoop on how the DH pros shocks (who use air springs) r fine tuned by their suspension team mechanics...adding fluid 2 the air chamber is no no... u r asking 4 trouble and could eventually screw up the negative spring and void warranty...

u will get a lot more info by checking out my response in the rp23 tuning thread...:thumbsup:
 

·
half tread will travel
Joined
·
240 Posts
_dw said:
Minsky, sounds like you are hitting a G-Out coming into this section of your trail. Is this accurate?

Its virtually impossible to stop a bike from bottoming in a G-Out, without compromising every other performance area.

One thing that can really help you is technique. Attack the G-out with your weigth forward coming in, and pump it just like you would when you are in between dirt jumps, transfer your weigth from front to rear as you go through the G-out. Your bike will be very compressed, front and rear, but you will be perfectly in control.

Hope this helps.

Dave
yeah thats how u do it...c it in your mind first before u go 4 it...timing is everything or u could end up OTB...good luck...
 

·
gnuH
Joined
·
1,164 Posts
Tread Mark said:
hey MinskyBA, u can manage bottom out with a combination of increased air pressure and adjust the air volume down by adding mass directly into the air chamber with a couple of 50mm x 2mm O rings... u can air up 2 match your weight with gear on and then start adjusting air volume down 2 get proper sag...other options r 2 slow down...or speed up and hop the whole dang thang...that's 1 hard hit your setting up 4....b careful...
I've just done a few calcs. Adding half a pillow pack of Fox fluid to the main chamber will decrease the air can volume by (approx) 12% at full travel.

Adding a couple of 50mm x 2mm O rings will reduce the volume by just under 5% at full travel. I'm not sure how the o-rings can be installed into the main chamber without floating around and causing grief. Note that the inside diameter of the chamber is 45mm so 50mm would not work.
 

·
half tread will travel
Joined
·
240 Posts
kiwirider said:
I've just done a few calcs. Adding half a pillow pack of Fox fluid to the main chamber will decrease the air can volume by (approx) 12% at full travel.

Adding a couple of 50mm x 2mm O rings will reduce the volume by just under 5% at full travel. I'm not sure how the o-rings can be installed into the main chamber without floating around and causing grief. Note that the inside diameter of the chamber is 45mm so 50mm would not work.
u may add more O rings if u need 2 but adding fluid may "float around and causing grief." because it may mess up the balance of the positive and negative air springs...the O rings maybe reconfigured 2 fit...good luck...
 

·
Unpredictable
Joined
·
2,213 Posts
Before you start disassembling things, I am around 185 (maybe 195-200 with pack) and if I ride with more than 10mm of rear sag I bottom out too easily in G outs. There is no problem with small bump absorbtion on this setting (for me about 195 in the RP23).

It is true there is no way a shock can prevent bottoming in G outs completely without being locked-out and there is good advice on that above. On my first ride on the Mojo our group stopped before a nasty bridge over a deep, sharp, but rounded creekbed. I decided to go down into the creek and up the far bank rather than walk over the bridge. To avoid a tree on the exit required a turn to the left. The amount of rear travel compared to my previous bike had me in the backseat and I actually flipped backwards and up onto the bridge and then off the other side. The bike hung up on the bridge and I failed to unclip, leaving me hanging below it laughing my ... off. Never crashed up onto a bridge before:) !
 
1 - 20 of 27 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top