Tuning a 2007 RS Reba Team
I have been running Fox forks on my bikes for the past several years. At first the performance difference to what was otherwise available was huge. Each year though, it seemed as if the performance 'bang' was really as great as the increase in cost. After riding the Fox 36 Talas, I was really disapointed in it's ability to perform trail riding and the difficulty to tune.
The difficuly was that other fork companies were really dropping the ball as far as performance went. Rock Shox forks for the last years before being purchased by SRAM were some of the worst peices of junk known to man. Most would suffer from the most extreme hydrolock on fast hits. garbage.
But things seemed to change with models designed after the SRAM takeover. It seemed they actually have pride in what they do now. A Semi-pro racer friend of mine, Olivier Bock, had been using a RS Reba for Pro Cross Country racing, and after getting on a Fox fork, said that the Fox didn't work as well. Around the same time, I borrowed a bike with a RS Pike on it. I was amazingly plush. I was in awe.
In setting up a new hardtail singlespeed, I needed a fork in the 4" travel range that was dirt cheap and worked awsome. I scored a 2007 Reba Team on Ebay for $370 delivered. Half the price of a Fox.
2007 RockShox Reba Team w/ Poploc Adj. Remote.
Mounted on a 17" 2006 Zion 660EBB Singlespeed frame.
200 lbs (about 15 lbs overweight, bla)
Aggressive singletrack rider. Some stunt and hucking, but mostly just fast riding.
Air Spring Presures
For me, a 200 lb rider:
Positive - 100 psi
Negative - 100 psi
Initial Riding Impressions
The fork works very well initially, but rides slightly low at 100mm and is not as plush as desired for fast singletrack riding. It needs less compression damping and more travel. It is also almost impossible to bottom, a real problem. This shows that it is riding like garbage at it's limits. Th rebound adjustment works fine.
The Poplock Adj. is killer. I really never figured that I would end up using it that much, just trying it as a lark. The thing is, it works. Run the fork at the desired compression, and pop it to threshold. The threshold adjustment works much better than the compression adjustment, but we will see if we can fix that.
The fork is plenty stiff enough for hardcore single track riding. I have hucked it off a few 4 foot drops into small rocks with little problem. Quite the stiff fork for a light cross country model.
Increasing the Travel
As supplied. This fork is configured for 100mm of travel. By removing a spacer, I can increase that to 115mm. Just enough for honest trail riding.
Riding the bike after raising the fork to 115mm is much more in balance. Fast travel is not really as hecktic as before. A little more would be nice, but then the front end would probably flop a lot more. It's good now.
Changing the Damping
To provide basic lubrication for this fork, Rock Shox, 15W Extra Heavy shock fluid is in the fork (same thing as Torco 20W). The ISO viscosity of this oil is 42.8. This may no longer be true, since SRAM is probably looking to streamline their entire range for vendor efficencies. A good strong fluid that doesn't gum up the fork and slow it down is good for this.
For damping, OE fluid is Maxima 85-150 Fork Fluid. The ISO viscosity of this oil is 15.90. Experience tells me that I need to use something much lighter when working on RockShox forks, but this is for the older stuff using Torco. I will use something close to this to start.
I used 100% Red Line (Medium, Red), ISO 30.40, for all but the top of the damper. For the damper, I used 100ml of 100% Red Line (Light, Yellow). Red Line Suspension Fluid is like magic. It smooths forks out really nice.
After a nice little rain ride, the fork really works nicer. The oil may not be perfect yet, but it is better. A little more tuning time will get it in line.
The fork has a lot of resistance to bottoming, which I'm really not into. I like to use all of my travel on most rides and use the compression adjustment to suit the terrain. Next time I have the fork apart, I will look into relaxing this resistance a little bit.
Most of the bottoming resistance looks to be coming from the spring side of the fork. I'm thinking that it is generated by air trapped between the negative spring chamber and the fork slider. I've got to pull the fork apart to see how to deal with that.
I may also try reducing the amount of oil on the damper side of the fork. Others have suggested 100ml instead of 110ml.
some could also be generatated within the damping side as shown here: