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  1. #1
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    What is the difference between a spring and air fork?

    Like the entry level Rock Shox XC30 fork on my bike and say the Reba RL air fork?

    I know the air fork is lighter but can someone explain how the more expensive fork will feel compared to what I have now? I'm riding a hardtail Giant FWIW and I'm 215lbs.

    I do notice that I get a lot of shock transmitted to the handlebars over fast rough terrain and my fork does seem to compress quite a bit (judging by how high the dirt gets pushed up after a ride) although when I stand over it and put my weight on the bar it only compresses a little bit.

  2. #2
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    The biggest difference beside the weight savings, is the tuneablility of the air fork via air pressures(+/-chambers) and an extremely adjustable rebound. Your current coil spring rebound is more pogo sticky, whereas the air spring is whatever you desire in speed and firmness. Do not underestimate the 2+ pound weight savings, it is priceless. Also the stanchions on the reba are 32mm and the xc30 is well 30 = not near as rigid/strong.

  3. #3
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    Quote Originally Posted by BlackMoBomber View Post
    The biggest difference beside the weight savings, is the tuneablility of the air fork via air pressures(+/-chambers) and an extremely adjustable rebound. Your current coil spring rebound is more pogo sticky, whereas the air spring is whatever you desire in speed and firmness. Do not underestimate the 2+ pound weight savings, it is priceless. Also the stanchions on the reba are 32mm and the xc30 is well 30 = not near as rigid/strong.
    Is this a pretty easy DIY swap? I've watched some videos on the procedure and it seems pretty straight forward and simple. I'm assuming I'll use some blue loctite on the brake caliper bolts but it should just be plug and play with some minor setup for my weight. I'll need a high pressure pump for adjusting the air pressure too.

  4. #4
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    It's not really "plug and play" because you have to press fit a crown race (either new or remove the old one from your original fork) and you have to cut the steerer tube of the new fork and install a star nut. None of these things is all that hard, but it helps to know what you are doing and to have the proper tools. (Go to the Park tool website and look crown race setting tool, star nut tool, and fork cutting guide). If you are not planning on doing lots of bike builds in the future, it probably makes more sense to have your LBS install the fork rather than investing in tools you won't use later.

  5. #5
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    Quote Originally Posted by BlackMoBomber View Post
    The biggest difference beside the weight savings, is the tuneablility of the air fork via air pressures(+/-chambers) and an extremely adjustable rebound. Your current coil spring rebound is more pogo sticky, whereas the air spring is whatever you desire in speed and firmness. Do not underestimate the 2+ pound weight savings, it is priceless. Also the stanchions on the reba are 32mm and the xc30 is well 30 = not near as rigid/strong.
    You are imparting some misinformation.

    Firstly it has been almost universally accepted that a coil spring is more responsive and linear. In other words if the spring is compressed and hits another bump it will continue to compress in a linear fashion. Compression of an air spring is non-linear. The more it compresses the more resistance there is as the air pressure increases with compression. If anything the air spring is more likely to be more of a pogo stick than a coil. There is a reason that most forks that really need precision control, like freeride and downhill forks, are coil sprung.

    The advantages of an air spring (and it is a compromise) is less weight and the ability to set the pressure for the rider weight. A coil spring requires a spring change to a stiffer or lighter spring for different rider weights.

    The fork's rebound is not controlled by the spring, air or coil. It is controlled by a separate rebound system, usually in the other leg. The quality of the rebound and compression dampers varies substantially and can account for a substantial price difference.

    There are some manufacturers like Manitou's MARS system which is a hybrid. A small coil spring in line with an air spring which work together and has advantages of both while remaining very light. You set the air pressure to adapt to the riders weight but even then within a certain range. Beyond those limits the coil needs to be changed.
    The trouble with having an open mind is that people will insist on trying to put things in it.

  6. #6
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    I don't want to discredit Thor29, because it is always nice to have a tool for a specific application, but I was able to swap out a fork with some standard mechanicin' tools and a home-made jig i made years ago for star nuts insertion/removal in 15 minutes...including time to crack two beers. Honestly, though, a wooden dowel and a dead-blow hammer work just as well assuming ends are cut square and it is the proper diameter. Steerer tubes are easy to cut by hand, as well, provided it is also cut square and the cut edge dressed to eliminated burrs and such. Pressing or removing a race is also quite easy with a large C-clamp and sockets or small sections of pipe to use as receiver or press cups...with proper diameters of course.

  7. #7
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    Quote Originally Posted by Ronnie View Post
    You are imparting some misinformation.

    Firstly it has been almost universally accepted that a coil spring is more responsive and linear. In other words if the spring is compressed and hits another bump it will continue to compress in a linear fashion. Compression of an air spring is non-linear. The more it compresses the more resistance there is as the air pressure increases with compression. If anything the air spring is more likely to be more of a pogo stick than a coil. There is a reason that most forks that really need precision control, like freeride and downhill forks, are coil sprung.

    The advantages of an air spring (and it is a compromise) is less weight and the ability to set the pressure for the rider weight. A coil spring requires a spring change to a stiffer or lighter spring for different rider weights.

    The fork's rebound is not controlled by the spring, air or coil. It is controlled by a separate rebound system, usually in the other leg. The quality of the rebound and compression dampers varies substantially and can account for a substantial price difference.

    There are some manufacturers like Manitou's MARS system which is a hybrid. A small coil spring in line with an air spring which work together and has advantages of both while remaining very light. You set the air pressure to adapt to the riders weight but even then within a certain range. Beyond those limits the coil needs to be changed.
    He specifically asked about an xc30 to reba rl...no disinformation there. the oil(hydraulic) damper is almost useless in that fork same as suntour xcm. he didn't ask about a $1500 DH/AM fork

  8. #8
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    Good info. Thanks for the responses!

    I'm going to ride my friend's bike next time we get together for a ride and see if I like the way his fork feels. He is riding a Specialized with the Reba RL fork, same size frame as mine, hardtail, he even has Shimano SPD pedals and we're roughly the same weight so it should be a good way to compare and see if this is something I want to spend the money on.

  9. #9
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    It truly was the difference between me looking to buy a new 650b rig and actually loving my 29er and completely forgetting a 650b

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