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Discussion Starter · #1 ·
Hi,

I own a 2006 Giant Trance fitted with Rockshox Reba World Cup w/Motion Control, 1 pce carbon crown/steerer & PopLoc , 100mm/4”.

Riding my bike home yesterday I had the PopLoc pushed in seeing I was on the road and wanted as little suspension travel as possible. I then went to ride over a grass section that is a bit bump for 100 metres so I pushed the release button to allow the suspension to have normal travel. However what happened is the fork dropped so only about 2cm of the fork insides arev isible rather than the usual 4 inches worth.

I have tried setting the air pressure with the shock pump but the forks stay stuck right down.

Any idea how to fix it and what might have gone wrong? There is no oil to be seen so it hasn't dropped a big mess everywhere.

Thanks
Chris
 

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Discussion Starter · #2 ·
OK it seems to be fine now but it still has me worried. Before the bike had 130psi in both top and bottom and was like that for two years since buying the bike.

Today I let all the air out the top and bottom valves. I then put 130psi in the bottom (on the side of the shock it says 130psi for 80kg rider), then put the same in the top and fork still stayed down. However as soon as I let all the air out of the bottom again the fork went up, I then put enough in to just get the forks to start to compress. The fork felt nice however checking the top one it only had 70psi in it, I pumped it up to 120psi to try get close to the figure on the side of fork. The fork still felt fine and close to how it felt before but a bit harder that I would really like.

Does anyone understand these forks? Am I supposed to take any notice of the psi on the side?

It seems everyone talks about have a 20% sag is best for XC racing. So would the best way to set the bike?

Does the following method seem right?

1, Start with virtually no air in the bottom and put a reasonable amount in the top.
2, Then using a piece of string around the shock (like the rubber band the rear shock has) sit on the bike and find where the fork sits with my weight on it.
3, Then lift the bike up and see if about 20% of the fork is below the string if not then add or remove air until that is about 20%.
4, Then regardless of what pressure is in the top add enough air in the bottom until the fork first starts to compress so you have the maximum air without losing hardly any travel.

Thanks.
 

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The top air valve is positive air and that sets the fork for rider weight and for sag. The negative air chamber is to adjust the small bump compliance and how much bob there might be.

Set the positive air pressure first using the top valve. If you were at 130psi you must be in the 180-200 pound range. Then set the negative air chamber at the same pressure as the positive to start, then add or subtract air to adjust compliance. More negative air pressure means a plusher more compliant fork. Less air in the negative chamber means a stiffer more XC race suited fork.
 

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More carbon fiber please!
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There's a great thread in this section regarding tuning a Reba... take a peek, it's worth the time.

https://forums.mtbr.com/showthread.php?t=183213

I weigh 172 and run 105 + and 100 - in mine but have run far less to gain more travel and it worked well. They're a great fork with a ton of tunability if you have the patience to test things. :)

 

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Discussion Starter · #5 ·
Thanks guys, both replies are really useful. I remember reading that post in July 2006 before buying the bike but spent ages searchign for it last night and couldn't find it.

I think I should try 100+ and 105- as I weight 178 in pounds (80kg).

On the shock it says 115-130 for 160 to180 pounds which is why I tried going for 130. Looks like the figures in the owners manual are a bit lower and probably more correct.

Thanks
Chris
 
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