I have gone back and forth between the stock WP suspension and the WP XACT Pro Components a time or two on the 2020.5 KTM 450 SX-F. Even though the AER fork is a better version of itself on the new factory edition, I still needed a little more performance and hold up without the harshness that I get from the AER fork. I have seen a lot of riders with the AEO/REP stickers on their suspension and wanted see what this company was all about. Mark Johnson was the WP factory Red Bull KTM suspension tuner for over ten years and he recently thought it was time to expand and create his own suspension company. He recently started Research Engineering Performance in order to use what he learned at the factory and incorporate that to help us normal everyday Joe’s that want their suspension re-valved. I had a set of WP XACT Pro 7548 spring forks and a XACT Pro 8950 shock laying around, so I decided to send my stuff off to Mark and the guys at REP.
Before REP took delivery of my suspension they asked me a few questions. They asked what type of riding I was doing, what type of rider I am and of course what I didn’t like about my previous WP Pro Component fork/shock setting. I told them I was concerned abut rigidity on this bike and always notice that the KTM gets more rigid with the Pro Component fork installed. I also wanted some added comfort on acceleration chop from the shock, but needed both ends to have comfort for longer motos. He took some notes and I had my suspension back within a week!
The first thing I noticed when I go out onto any type of track with the XACT Pro fork is that the KTM turns slightly slower than the AER fork on initial lean (into corners), which is exactly what I got out of the KTM. The KTM does have a slightly rigid feel to it once you install the XACT Pro fork and can be a handful when riding fast, choppy tracks if not set up correctly. You can actually feel the extra weight right away (in the front end) compared to the stock AER fork, but it wasn’t a bad feeling. I was just surprised I could feel it as much as I did when entering corners, but adding a little weight to the KTM isn’t a bad thing. Usually I run the fork flush on previous Cone Valve forks, but with the slower turn in feel and a the longer length of the new style XACT fork I went with a 7mm height recommended by REP. Along with the extra weight feeling in the front end I gained more front end traction through every corner (especially flat corners). With the REP valving I get more front tire contact patch feeling on lean angle and you can start your lean earlier when setting up for corners without getting the high front end, vague feeling like you do with the AER fork. With the AER fork I get some pushing in the front end through the middle to end of corners, which can make me roll off the throttle to try and compensate. With the REP/XACT fork I can lean in the corner and the fork stays planted, which lets my front end settle and bite. The REP/WP XACT fork also feels less active on braking bumps and allows me to leave the throttle on longer once the de-cel bumps start. I am able to jump in and out of bigger bumps with the REP valving without having the fork rebound too quick and be too active. If I wanted to pound through the bumps, the fork had better damping control than any other WP fork I have tried to date, through the middle to end part of the stroke.
The most notable change was to my wrists when over jumping/flat landing with the REP/XACT fork setting. I could get more aggressive with obstacles and have the bike settle into corners better in areas of the track I wasn’t able to with the stock suspension or any previous XACT Pro fork valving setting . The downside to the XACT fork is that it can make the KTM feel like it has less flex up near the head tube area. This feeling is not as rigid as a Honda CRF450R, but it does give you a firmer feel through your hands on small bumps, compared to the AER fork. The key to the WP XACT fork is getting it set up for you and REP did manage to nail the fork setting in only two attempts. WP does a great job of getting you the XACT fork with a “ballpark” setting, but going through an authorized dealer like REP is the best way to ensure your investment works the best. I like that Mark and the guys made the more rigid feeling XACT Pro fork less harsh to my hands. Note: The first setting they made up for me was too stiff, so I asked to back the damping feel down some. I wanted the fork to move a little more in the stroke. Once I got the second setting back and on the bike, I could immediately tell a big difference in comfort. The fork moved more freely yet still had enough damping where it didn’t dive on me too much.
The REP/XACT Pro shock holds up better than the stock shock for me on high speed compression and you are able to get more aggressive around the track. I can hit the faces of jumps harder and the KTM did not give me an empty/low feeling sensation that the stock shock sometimes can give me. In order to combat that feeling with the stock shock I would have to crank in the high speed compression so much that I would lose the comfort coming out of corners (and rear wheel traction). The REP/XACT Pro shock provides you with more high-speed damping and you still get a decent amount of acceleration comfort on choppy corner exits. I also noticed a little more connectivity to the the rear wheel (when hard on the gas) on flat corners with the REP/XACT Pro shock compared to the stock shock. The REP/XACT Pro setting is firmer so there is less wallow in the rear end when accelerating, so the rear of the KTM 450 SX-F tracks straighter and doesn’t upset the KTM’s chassis as much at speed. “Balanced” is a great word to describe both ends of the KTM now with the REP setting, but I did notice the harder I pushed the more it rewarded me. If I tried to ride smoother/slower, the action of the shock wasn’t quite as comfortable as the stock setting. This REP/XACT Pro shock setting likes to be pushed and will reward the rider that is aggressive because of its much more consistent nature (compared to the stock shock). The dead feeling nature of the shock provides less movement on de-cel, so driving through braking bumps is made a little easier. Again, going to a WP authorized dealer like REP and having it set up for you is key. Thinking that you’re just going to go purchase A-Kit level suspension, slap it on, and then magically be in heaven on the track is completely foolish!
When you’re dealing with A-Kit style suspension, you’re only going to be as good as your suspension tuner. A good rule of thumb is to always try to look for tuners that have experience with the suspension you’re riding with. I was happy with the settings Mark and the gang at REP came up with and I am looking forward to trying their knuckle and pull rods on a separate test that you’ll see over on keeferinctesting.com.
If you have any questions about this test you can reach out to me via email at email@example.com.
You can contact REP at 951 566 7426 if you have any questions regarding your suspension. .