Suspension Performance
We’d be lying if we told you that we haven’t been fans of air forks, and you’ve probably heard us say we aren’t in the past. However, while the WP AER 48mm fork on the KTM 450 SX-F and the Husqvarna FC 450 is pretty damn good, the best suspension in our 2018 450cc motocross shootout is found on one of the machines that is equipped with a coil spring fork. Oh yeah, and it’s also found on the bike that has been equipped with a coil spring fork the longest time of any machine here: The Yamaha YZ450F.
As part of its 2018 redesign, the YZ450F got a new version of the KYB SSS fork. The 48mm legs feature revised specs and settings to work with the Yamaha’s new bilateral beam chassis. The cylinder and piston size have been increased from 24mm to 25mm, and Yamaha replaced the coil spring mid-speed valve spring design with a leaf spring. The pressure piston shape has also been changed, and it sports additional holes to help pass oil more efficiently. Out back, 018 YZ450F’s KYB piggyback shock body sub-tank capacity has been increased 30cc, and oil flow has been increased in an effort to offer more even and controlled damping. The shock spring is made of thinner material, which also helps reduce the spring weight. The spring rate is also 58 Newton/mm compared to the 56 Newton/mm spring found on the 2017.
Although not unanimously selected by our test crew, the Yamaha handily topped the suspension performance category. Most appreciated the Yamaha’s suspenders right out of the box.
“Definitely the best suspension out of any bike here,” Abbatoye said. “I automatically felt like I could race it right out of the truck. There pretty much isn’t anything that it can’t handle. Initial feel is great, and it has really good bottoming resistance. It was the only bike here that I felt like I could race with the stock suspension.” Smith agreed. “By far the best in the class,” he said. “To me it felt like you could feel the tires rolling across the ground, just hooked up the whole time. No harshness at all. Just perfectly smooth, connected action.”
Still, the KTM 450 SX-F with its WP AER48 fork and WP shock performed almost as well as the Yamaha, soaking up small bumps and big hits with equal competence. The new piston and air seals seem to eliminate any initial harshness that might have plagued the 2017 model. KTM’s relatively simple change yielded improved overall suspension performance in this 2018 450cc motocross shootout.
“In fact, this was the only bike I didn’t make changes to,” Stover said of the 450 SX-F.” It feels really planted, and it handles all the rough stuff the same. It doesn’t want to deflect on the big stuff, and it doesn’t feel harsh in the chop. I really like it. The KTM’s suspension feels better than the Husqvarna to me.”
Abbatoye, however, found the KTM suspension to be a little on the soft side at first.
“We stiffened it up, and it really worked well,” Abbatoye said. “I felt confident everywhere on the track.”
Smith, however, wasn’t as impressed.
“Through the beginning of the stroke, the KTM is plush and supple,” he said. “But into the mid-valve and the bottom of the stroke it felt a little harsh to me.”
Of course, since they are basically identical to the KTM’s the Husqvarna FC 450’s fork and shock also finish close to the KTM on the track.
“When I first got on it, it was way too stiff for me, and it wasn’t riding balanced,” Abbatoye said. “Once we stiffened things up, it was night-and-day different. It soaks up super-choppy stuff really well.” Smith agreed, saying, “The rear suspension is really good. It tracks well and holds up in all the braking bumps and hard hits. The forks initially felt a little jarring, but slowing down the rebound tended to help out. Other than that they have nice action. They don’t get twitchy or do anything funny.”
Once again a pleasant surprise in our 2018 450cc motocross shootout, the 2018 Suzuki RM-Z450’s new 49mm coil spring fork and BFRC shock are a huge improvement over the 2017 model.
“They have the new shock where the compression is one adjuster rather than the high-speed and the low-speed,” Smith said. “It really works well. One compression adjuster and one rebound adjuster, and it works. It doesn’t have any clickers. I went out ¼-turn, and it gave me exactly what I wanted. It’s supple yet soaks up big hits well. You won’t feel small chatter bumps, and it also doesn’t give you that clanking feeling.
But Abbatoye felt that the BFRC shock, which features separate external damping circuits intended to improve shock sensitivity and response, still needs more work to match the performance of the Yamaha and the European bikes.
“The new forks are 100 times better than the old ones, but the shock could use some work,” Abbatoye said. “I got a little bit of kicking here or there. When you have a bike that is really dialed-in, you can relax more, but I always felt like I had to pay more attention on the Suzuki than on other bikes.”
Another surprise was that, although most of our test riders claimed to like the CRF450R suspension, it didn’t finish as high in the 2018 450cc motocross shootout suspension performance standings as we thought it would. Honda’s decision to alter the CRF’s valving and go with stiffer valve springs in an effort to get the suspension to stand up a little more in choppy terrain drew mixed reviews from our test crew.
“When I first got on it, it was way too stiff for me, and it wasn’t riding balanced,” Abbatoye said. “Once we stiffened things up, it was night-and-day different. It soaks up super-choppy stuff well, but I’m a lighter guy, and I feel like the 2017 springs and valving worked better for me.” Smith agreed, stating “I don’t know why they added heavier fork springs, but for me it didn’t seem to help.”
Even the 175-lb. Stover had to go softer up front to find suitable settings for the Honda.
“The rear was fine, but for my riding style I want it to squat a little more, so I softened up the high speed a quarter turn. Up front, I still got a little more feedback into the bars than I wanted on the Honda.”
The Kawasaki KX450F also drew a mix of comments from our crew. Abbatoye said that the KX’s Showa TAC air fork danced all over the place on the Cahuilla Creek track.
“We made some adjustments, which helped, but I feel like they need a lot of work to get right,” he said. “The rear end is okay, but I was so worried about the forks that I couldn’t concentrate on what the rear end was doing. I really had to concentrate to maintain a fast pace.”
Stover also had issues with the Kawasaki’s front suspension action.
“As soon as you start hitting the rough stuff, it feels like the fork is packing,” he said. “We softened up the front and took a little bit of air out. That helps, but it’s still not as good as some of the others. You really notice it in braking bumps. The rear feels pretty good, though. It has good bottoming resistance, but it stays nice and plush.”
Smith, however, complimented the Kawasaki’s suspension.
“It ate up the small stuff on the track like the high-speed chop—it was probably the best of the group at that—and it still sucked up the big hits well,” Smith said. “I think I was the only one who got it working well.”
2018 450cc Motocross Shootout Suspension Performance Results
1. Yamaha YZ450F
2. KTM 450 SX-F
3. Husqvarna FC 450
4. Suzuki RM-Z450
5. Honda CRF450R
6. Kawasaki KX450F
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