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Discussion Starter · #1 ·
Can anyone explain to me how rebound works. I just got the 2010 recon 351 u-turn and Im clueless to how rebound works. Which riding style should I have the rebound set to slow and which riding style should I have it set to fast? The forks are awesome so far just curious how the rebound works. Thanks for any info and Merry Christmas!! :thumbsup:
 

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Short answer: whatever feels the best on your trails.

The rebound slows down the return of the fork to the riding position. Too fast and you will feel like the front end of your bike is like a pogo stick. The front end will spring up when you don't want it to.

Too slow, and you'll start to 'pack' the fork in. The fork isn't returning to the normal position fast enough and with each subsequent bump, you'll be using less and less of your travel.

The goal, is to find a happy medium. Too many factors involved for me to say "15 clicks to the right will do the trick" So just try it and see until you get it dialed in just right. I like to make a small mark on the knob when it's perfect.
 

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On the technical side of how rebound works, it's basically the same principle as what makes the shock work (fluid flow restriction through valves from one chamber to another) only rather than operate to absorb initial shock, it resists the suspension's tendency to pop right back up to full travel.

Originally when all shocks contained metal springs, the rebound circuit was designed to resist the coil spring's natural tendency to return quickly (which was felt as bouncing). These days many suspension systems have done away with an internal metal spring and instead rely upon air pressure to mimic the spring's ability to compress and rebound. As such the rebound adjustment could very well be simply a pressurized chamber setting. Again though, regardless of how it's accomplished, the goal of the rebound circuit is to control the rate of speed at which your suspension returns to full travel after being compressed.

Hope this helps!
 

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gunslinger
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Compression: takes/deals w/ the initial hit. In a perfect world, you want enough play (aka action on the compression stroke) to bottom once in the most extreme case per lap/outing. Bottoming consistently says somethings not set up right - period. Better yet, you don't want to bottom... you want to use all the travel except .5mm over the biggest hit. Like I said, perfect world and completely impossible to prep for.

Rebound: simply modulates the air/oil flow as the spring returns to its unloaded state. Say you're on a dead-flat 100M surface riding @ 30kMh. The one and only depression on that stretch is straight ahead. Your bike hits it and the fork goes into compression. Once you begin to unload, the rebound valve "clicker" (damper setting) will tell the air/oil how quickly to pass thru the valve. It may happen slowly or quickly depending on what you've done. Why does that matter? In theory, you want to be set up the same for the next bump as you were for the first. You want all of your compression stroke to deal with the following like-sized bump. If that bump is very close, you want very quick rebound. You don't want 100% of your compression stroke for the first hit then only say 40% of the compression stroke for the next hit of the same size. That's called packing and it diminishes control. When you loose control, it's over.

A spring is a spring; a stupid piece of engineered metal, and it does nothing more suspend a given rider's weight relative to their ability/skill. It's the air/oil on the compression and rebound strokes, and the movement thereof, that really mean something.

Air/oil is used top and bottom (compression/rebound valving) to modulate fork/shock action. The principle is the same front & rear (fork & shock), only the results differ and their subsequent impact on control.

The ONLY WAY to truly understand it is to go out and run to the extremes of all your settings over the same piece of terrain and note the differences. You can read about it all day long and everyone and their cousin has their take, but until you know what the extremes feel like, you won't know much. It's very easy to do and I'd suggest going to the extremes first off rather than stepping thru progressively softer/harder settings. That's fine for later on, but initially, run the extremes over the EXACT same piece of terrain @ the exact same speed, etc. and the difference will be as clear as day.

I need to add that not everything that you (a rider in general) might think is a suspension problem is. Rider position plays an equally important role too.
 

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Discussion Starter · #6 ·
Thanks for all the info guys! So I guess I will make my next day of riding a day of testing and learning my suspension. The spring that came with the fork is very soft. When I sit on the bike the fork sags to 115mm (Im 6' 200lbs). So should I wait till I get a more firm spring till I test the rebound?
 

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gunslinger
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Bear in mind that my perspective is from the motocross world; you can get spring rates to suit your skill & weight; a heavy goon rider might/will run a spring rate similar to a lighter faster/better rider. I would hope that all the mtb fork mfgs offer several rates. Personally, I wouldn't test pud'n until I had the right springs. Springs that are too soft allow deeper compression and that then impacts rebound.

Many components, one system.
 

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Old man on a bike
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JTreehorn said:
Thanks for all the info guys! So I guess I will make my next day of riding a day of testing and learning my suspension. The spring that came with the fork is very soft. When I sit on the bike the fork sags to 115mm (Im 6' 200lbs). So should I wait till I get a more firm spring till I test the rebound?
That's sag of 19% (assuming 130mm travel, 18% if it's 140mm) which is possibly not even enough; I wouldn't call it too soft to start at least. You can't really tell until you use it. Depends how you did the sag test a bit, too. How I interpret your sag figure, too.
 

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According to the RockShox spring chart I have, the Recon U-Turns come standard with the Red spring for riders 140-160 lbs. :rolleyes: You're going to want the Black springs for riders over 180 lbs. Part number 11.4310.139.000 for 80-130mm Recons.
 

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GiddyHitch said:
According to the RockShox spring chart I have, the Recon U-Turns come standard with the Red spring for riders 140-160 lbs. :rolleyes: You're going to want the Black springs for riders over 180 lbs. Part number 11.4310.139.000 for 80-130mm Recons.
You can't always go by the charts...not all springs are created equally, either. I ride the spring below Fox recommendation for my weight on both a Van 36 and Van 32. Supposedly can be a 10-15% variance in steel spring rating accuracy with Fox from what some have said, though not sure if that translates over to Rockshox product as well. Sag seems reasonable (I think) and the real test is on the trail. That is one nice thing about the Fox aftermarket fork, that you get a few springs with the fork to test out without buying another (maybe).

OP, you might want to take a look at the color coding on the spring installed in your fork at least before you start ordering...and while you're in there you could make sure it was shipped with a reasonable amount of shock fluid.
 

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Ok.. some basic suspension stuff.

Springs in the form of gas or metal coils hold the bike up. The shock body contains fluid based dampers to control how fast the springs work in each direction. When compressing the spring the compression damping offers this control. When rebounding from being compressed the......yep, you guessed it.. the rebound damping controls this action.

Some shocks and forks have multiple damping circuits which are high and low speed. Low is for stutter bumps and the initial portion of the stroke and high is for bigger hits.

Sag sets the static position of the spring. This is your load with gear on, on a stationary bike. Rule of thumb seems to be 20 to 30 percent of available travel in the rear and 15% to 20% in the front.

When trying to figure out what does what with damping settings remember this simple rule: Compression is for comfort… Rebound is for control. Example… you're hauling a$$ down the trail and you hit a square edged bump and BAM!! Your seat smacks you in the butt and your wrists get jarred. That is uncomfortable and is controlled with compression damping. Less compression allows the spring to compress quicker…more slows it down a bit. Next.. you hit a g-out or a drop and the fork and shock compress almost 100% and then bounce back like a pogo stick causing you to not be able to hold a line or even crash.. (not enough rebound damping) or you hit consecutive smaller trail bumps and the suspension packs down and does not return to full or near to full-travel, eventually leaving you no available travel (too much rebound damping). These are control issues and rebound damping offers the solution.

Lastly, when you make adjustments WRITE THEM DOWN!! Also don't just start spinning dials, twist everything full clockwise and then back it out 50%.. Start from there. Righty tighty, lefty loosey. Tightening the dial adds more damping effect, loosening it lesions it. Lastly, asking someone what they use for settings is tempting but what I like in a bike and what suits my skill level may be unridable and even downright frightening for you.

Reminder... work on your settings after riding the bike agressively for a bit to warm up the oil in the shock and fork.
 

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STT GUY said:
Rule of thumb seems to be 20 to 30 percent of available travel in the rear and 15% to 20% in the front.
Roughly the same sag front and rear, generally not less than 20%.

STT GUY said:
Compression is for comfort… Rebound is for control.
No, compression for control and...rebound for control. It's all about keeping the fork taught and under control, providing the most traction all the time.
 

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bad mechanic said:
No, compression for control and...rebound for control. It's all about keeping the fork taught and under control, providing the most traction all the time.
This is a beginners forum,right? Hell most of these folks still think it is dampening... you know like babies dampen diapers, and that's ok we ll start somewhere... So let's make it easy to understand. I challenge you to find an easier way to explain which damping circuit invloves what than the "Compression for comfort, Rebound for control" bit. Many manufacturers make dampers that have factory pre-set compression and are only rebound adjustable.

Sure you can get all complex...as I can too, with mumbo-jumbo about shim stacks, progessive or straight wound springs, multi-speed damping circuts, the effect of linkage ratios on suspension action, etc.., etc...etc... But in reality all Joe Novice, hell or Joe Intermediate needs and more than often wants to know is "I hit X and my bike does XX, what can I do to make this better".

1) What is your tire pressure, 2) Have you set your sag.. and if these are in the ball park we work on rebound and/or compression settings as appropriate and where available. some suespension

The KISS principle is very effective when it comes to suspension
 

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Sure, it's the beginner's forum, but if someone who doesn't really know what they're doing looks at that, they're going to go "The faster I set my compression, the more comfortable it feels", and they're going to end up with a compression setting which is too soft. There is a very big difference between getting into technical workings of a fork and telling them "compression is for comfort".

Obviously this doesn't matter if their fork, as most entry level forks, doesn't have compression adjustment.
 

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bad mechanic said:
Sure, it's the beginner's forum, but if someone who doesn't really know what they're doing looks at that, they're going to go "The faster I set my compression, the more comfortable it feels", and they're going to end up with a compression setting which is too soft. .
Well IYO would a fork/shock with no compression feel "comfortable" as it blew through it's travel and bottomed out? My experience says "no" but I guss I just get lucky.
 

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That's exactly why the old Marzocchi forks were considered so good and so plush, because they had very little compression damping.

It's usually ultimately the spring's job to prevent bottoming, although some forks will add some sort of hydraulic bottoming control, and some older forks allowed some control over progression via oil volume.
 

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Discussion Starter · #18 ·
So whats the best way to find my sag setting? I was going to get the most firm spring, for my weight, but now Im not so sure. Also is it normal for the fork to make an odd suction like sound when rebounding?
 

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trail addict
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STT GUY said:
I challenge you to find an easier way to explain which damping circuit invloves what than the "Compression for comfort, Rebound for control" bit.

The KISS principle is very effective when it comes to suspension
Spring rate or air pressure-supports your weight-should be set first, 25% sag (or manufacturer rec.) is usually a safe place to start

Compression-keeps the fork from compressing uncontrollably (brake dive and landing from drops are good examples of what compression can control)

Rebound-keeps the fork from rebounding uncontrollably-keeps the susp from "pogo-ing"

Once spring rate is set, start with comp and reb nearly full-fast. Add more damping (slow it down) to either setting as the need arises.... spring rate can also be adjusted, but within reason... don't try to run too little spring rate and compensate with too much compression damping and vice versa...

Pedalling platforms, lockouts, and such will all have an impact on the ride as well, but start with them wide-open... then start using them on smooth climbs to see if you feel an advantage-different suspension designs and riding styles will have different needs for these settings

Can't really get any more simple than that. Just because the guy may be a beginner is no reason to intentionally leave out basic info.
 

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Good information in this thread...

One other thing...the fork will take a few rides to "break in"...ie the settings you like on the first ride will differ 3-4 rides later as the bushings and stantions get to know one another. I like to find an acceptable setting on the first ride...then leave it alone for a while otherwise you will be constantly playing with them as the fork/shock loosens up. Then go to a favorite spot on the trail and get them dialed to your liking. Temp, trail conditions, different trails can all warrent changes, don't be afraid to change them, but WRITE THEM DOWN...I am constantly fighting with the wife as she likes to fiddle...then complain that it's not riding like it was but has no idea where the settings were that she liked...she finnally went back to a hard tail!
 
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