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Discussion Starter · #1 ·
I figured I would rather post this here than the suspension forum.

I own a 2008 Mojo SL with a 2009 Fox Talas 150mm. I'm having a terrible time with the fork dropping deep into the stroke when standing up. I set the sag to be 1 3/8" when I'm seated and the fork is at 150mm. In order to this I have to put 85 psi into the fork. I weigh 155 without gear and ~ 168 lbs with gear. I have been setting my sag with my gear on.

Now hear is the problem. The moment I stand up and get into a attack position and weight the front bars, the fork dives deep into its stroke. It sinks around to 2 1/2". This leaves less than 3 1/2" of travel for hitting bumps. Is this normal with long travel forks? It gets even worse if I slam on the front brake. I bumped up the low speed compression and sped up the rebound to prevent packing and it helps but hurts small bump complience.I'm coming off a Yeti 575 with a 130mm fork and it did not do this. It stayed much higher in its stroke and did not dive, but was also 20mm less travel.

I'm just curious if it is just the way the geometry is on this bike or is this how all long travel forks respond?

Erik
 

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aka dan51
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I would add air to the fork.
My belief is setting sag on a fork is a complete waste of time. Set it to what feels right when you are riding the bike, not what the manufacturer tells you is right in the parking lot. Add 10 PSI and ride for a bit, then add 5, then 5 more, then remove 3 etc..... until the fork feels how you want it to on the trail.
 

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Reviewer/Tester
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That's what I do, tune it on the trail...always do it that way. The manufacturers settings are just a starting point, imo. Set it up for *your* style, weight and how you want it feel out there on the trails and you can't go wrong.


R.
 

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The MTB Lab
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A couple of things...

1) the short top tube length of the Mojo does make the fork dive a bit more
2) you might not have enough oil in the air chamber? you might think about adding .5-1cc of 7 weight oil
3) what length stem are you using?
4) also you need to ride a bit different with the Mojo, there isn't as much need to stand while attacking
 

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www.derbyrims.com
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That's normal, and there is deeper brake dive with air forks than coil no matter how "linear" the air forks are claimed to be.

For long standing pedaling, firm up compression damping a lot, to max firm compression.

Rockshox has "Motion Control" with "Floodgate Control" on the Pike to be able to flip the compression knob just 1/3 turn on the fly to go from normal soft compression to lockout that blows off on sharp hits, and a handlebar remote is available. I don't know of other longer travel forks with on-the-fly lockouts.
 

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Discussion Starter · #7 ·
Wow, thanks for the replies.

To answer some questions.

The bike is perfect when I'm spinning on climbs. I come from a motocross background and ride over the front on fast rolling terrian. I use a lot of body english and I guess that comes from racing motocross. I rarely ever stand and mash the pedals. The only time I stand is coasting along attack terrian.

I'm 5'11" and use a large frame with 90mm stem. The medium was too cramped when I rode it. I do have my low speed compression turned out to 2 click from full hard. The bike rides real good at 130mm and I will switch it to 150mm if I'm riding rolling terrian or going downhill. I have over 250 miles on the bike and think it is a very solid bike.

Tomorrow i will bring the air pump with me and test for a while. The trails here are a bit covered with snow, but up North they are dried out. I wonder if the 150mm needs a bit more air due to the increased length. Also at 150mm it kicks the fork out and puts more pressure on the rear. I don't notice this as much in the 130mm mode.

The other thing I want to try and never have is using the lockout knob at the bottom of the fork. I never lock out the fork. I wonder if i could keep the fork lock out al the time and use the blue knob to dial in the blowoff. This wouldn't help in smal bump complience though.
 

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aka dan51
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bedell99 said:
The other thing I want to try and never have is using the lockout knob at the bottom of the fork. I never lock out the fork. I wonder if i could keep the fork lock out al the time and use the blue knob to dial in the blowoff. This wouldn't help in smal bump complience though.
Keeping the lockout on full time will probably be short lived.
If it's like the TALAS from 4 years ago, whenever the fork "blows off", you'll hear a high pitch squeak. It's also probably not good for the fork. I think the blow off is there to keep from damaging the fork if lockout is left on, not as a stable platform setup. What you want to do with the lockout is exactly what Motion Control is designed to do on Rock Shox forks.
 

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holding back the darkness
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Personally, I'm with Derby in his thoughts on the PIKE.
However... I like the abovementioned idea to add oil to the air spring chamber. I have no experience in this particular bit of tuning fox forks, but adding oil will effectively decrease the air spring volume and make the spring more progressive (an effective tuning tool in Maverick forks).. This may help limit the depth of your break dive problem.
 

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Discussion Starter · #10 ·
I went on nice technical ride today at trail on the Front Range of Colorado called Dakota Ridge. Here are my final settings after constantly playing around. I noticed the biggest difference when I lowered the sag in the rear from ~13mm to ~18mm. I upped the fork pressure to 90 psi and then backed off on the low speed compression. Left the rebound the same. I never even checked the sag on the fork. I just rode what felt good. I stil think 90 psi is alot of pressure for a front fork. The zip tie on the fron fork was about 1/2" from full travel but my fork never bottoms. I left the fork in the 130mm mode on most of the ride. It really rides great at 130mm. The frame was actually designed for a 130mm fork according to Hans.

Erik
 

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You should set your sag in attack position. Then slowly dial in some compression

sounds like you got some settings that work though.

Another factor is that you are probably unbalanced front to rear. Too little sag at the back and too much at the front. I always maintain that you try to set up as best as possible with all damping at minimum. Get the spring rate as close a possible. In the end you won't be able to get a tune for all types of terrain but you will achieve a best compromise
 
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