If there’s anything you want to know about dirt bikes, there’s a good chance you can learn it from Paul Thede. With decades of experience working on and riding motorcycles, Thede has witnessed the evolution of the dirt bike and understands the technology that has led to big and small developments along the way. As if starting his company, Race Tech, and being an avid rider wasn’t enough, Paul wrote Race Tech’s Motorcycle Suspension Bible, and teaches seminars based on the information in his book. We happened to be making a visit to his shop in Corona, California, and decided to stop in and have a chat with Thede about suspension, motors, and Race Tech’s popular air-to-spring conversion kits.
What things should people be doing to their suspension?
That’s a good one, because a motorcycle is so light compared to body weight. Another way to put that would be that body weight is such a big deal compared to bike weight. It’s not like a car. With a car, it doesn’t matter whether you weigh 250 lbs or 150. The number one thing you need to do is set it up for your weight. That really has to do with setting up your springs, selecting the correct spring rate, and how much preload you’d need to set the sag. That would be the first thing. The other thing is that because these same motorcycles are used for motocross and Supercross – which are as different as night and day – trail riding, enduros, desert riding, flat tracking, and so-on, the next thing to set up the valving. All of this stuff is what we’ve been doing since the beginning of Race Tech in 1984. What we’ve done is create kits that either we can install or other people can install themselves. That’s the distinction I’ve made with my company. I really changed it from having people send it into me and I do all of the work to helping someone do the work if they want to do it. We have everything in kits, we’ll also sell tools, I teach the seminars, and I wrote a book, and all of that is designed so that if you want to do it yourself, you can do it yourself. Really, it’s a matter of setting up valving. What’s really unique about our company is that I have what’s called DVS, or Digital Valving Search, which is done on our website, so that when you get a kit you have enough valving to go from Supercross to flat track. What you do is take that kit, go onto the internet, and there’s an access code in there, and the internet actually calculates the valving stacks in there. What we’re constantly working on is the valving stacks and the settings so that they have the latest settings. That way whether you’ve brought it in here or done the install yourself, you have the exact same setup. From that point, it’s a matter of doing it correctly. The biggest issue we’ve had in the thirty-plus years of doing this is that people will take the valving stacks and install them upside-down. Then they call us up and they’re angry, they’ll be writing on the internet, “That stuff doesn’t work.” I always tell them to let me take a look at it and tell them to put in on the right way. After that they say the stuff works good, but they’ve already written something bad. The trick is once you get the kit and settings, it’s a matter of putting it in right and knowing what you’re doing. Use the correct torque wrench and put Loctite in the right places in the right amounts. One of the critical things is doing a setup that’s consistent, so that it’s the same over and over again. I’ve certainly seen setups where it’s supposed to be the same valving, but the bikes work completely different. Being able to install things correctly is critical as far as suspension is concerned. If I were to look at things as far as what you do during the install process, I’m sure you’ve heard the phrase cleanliness is next to Godliness, and as far as suspension is concerned, that is absolutely true. You get a little bit of shavings in there and it doesn’t work the way you want. It can actually destroy things. The next thing is as far as the assembly is concerned, it’s as simple as setting your clickers correctly. I’d say it’s probably one of the other things we’ve found is an issue over the years. People will call us up and say, “Hey it seems like it’s kicking,” after we’ve sent them a set up. We’ll ask them where their external settings are at and invariably what people will do is get nerves some day or they’re not riding as fast as they’d like to and they’re grabbing the handlebars too tight, so they say the bike is kicking and slow their rebound down. In general, that’s the exact opposite direction you want to go. They slow the rebound down over and over, and it’s counterintuitive to most people. They think that when suspension hits a bump and kicks, it’s going through the travel and then recoiling uncontrollably and slapping them in the butt. That’s not what happens though. What actually happens is it absorbs the bump and becomes too harsh so it deflects, or it goes all of the way through the travel, bottoms out, and then deflects. Too much rebound damping, which means too slow rebound damping, actually causes kicking, but too little rebound damping won’t. It’ll make the bike feel loose, and I’m not saying don’t have any rebound damping, but understanding the connection between rebound damping and how a bike should work is a really big deal. Then, I always say, make sure that you install the stickers correctly! That’s my joke of course [laughs]. Those are the things as far as suspension is concerned, and then certainly maintenance, linkage and all. It all ties together, meaning the entire bike. If you’ve got a throttle tube that’s sticky, you’ll think your suspension isn’t working as well as it should. If you’ve got an engine that’s built with really high peak horsepower numbers, but it’s lost all of its bottom end and it’s pipey like a two-stroke, it ruins the bike and it makes it much harder to ride. All of that will translate into how friendly that bike is and how easy it is to ride. I very rarely get a 450 motocross bike wide open and get to that peak number, but to have that nice broad powerband that comes on smoothly is a really key part of making your suspension work.
On that same note, with you guys doing motors too, let’s say someone comes to Race Tech and asks for as much power as possible out of their 450, do you build that for them or do you try to balance what the customer wants with making sure that the motor isn’t unreasonable?
It’s kind of interesting, people obsess over peak horsepower numbers. The number of people that can actually use that is small, and the people who actually can use it only spend a short amount of time at that peak number. It’s so rare it’s crazy. What we focus on is powerband, and Rob and Andrew are phenomenal at building engines. I used to build two-strokes and I was pretty good, but those guys are phenomenal. Rob was actually taught by some of the best engine builders in the world. The real trick is to be able to build powerband. If you build a good powerband, you will pick up peak numbers at the same time. One of the things that I never thought about, and I thought it was odd when I first heard of it, was to take a brand-new engine and do a valve job on it. I’d look at it as a brand-new engine and wonder why it needs a valve job. In my head it’s a valve job, you do it when it gets worn out and you’re refurbishing it. The valve opens up and the more the valve seat is a nice, smooth curve at the edges where the valve opens, the smoother things flow, and at lower valve lifts you get a better flow rate. If you have better low valve lift flow rates, you can get some really good powerband as well as power. We generally are building it the way that we want to build it, and the numbers come anyway. We don’t focus too much on peak horsepower. We take our engine dyno and we calibrate it as accurately as we can, and we know what other dynos from other companies are like, and if you put our stuff on another dyno it’ll give you a different number. The peak horsepower numbers get lost in that. The way that we build engines, we’re not doing a complete motor. We help engine builders build great engines. When we’re doing a head and valve job, we also do cylinder porting, and we’re doing that to a head on a flow bench, we can predict exactly how much horsepower it will make within a small window, assuming that everything else is done correctly. Our goal is really to help people build engines, as opposed to people bringing a complete engine down here and we rip it apart. As a customer or an engine builder, you can bring your head down, your cylinder down, or your crank down, and it’s matter of doing things precisely and correctly to really build that powerband as well as the peak numbers. Again, the peak numbers come, but what we want to do is we want to see a gradual powercurve and bring everything up. We don’t want to see that we lost anything on the bottom but got a really great top end. That doesn’t mean anything to us at all, and you’d actually be surprised at how many engines get ruined when people start to get their grinding tools out. By having the numbers, particularly with four-strokes, it’s a very scientific process and we can very accurately predict what a motor is going to make.
Race Tech is very popular for its spring conversion kits for air forks, and that seems to be a fairly common modification. What are your thoughts on the air forks, as well as production bikes moving back towards spring forks again?
Well I’m pretty vocal, I’ve been teaching my seminar since 1994 to anyone who wants to learn about suspension, and I always tell people that what you’re going to get is my opinion for the next six or seven days as far as what I think works and doesn’t work. Air forks have the potential, and there are some advantages to them. Number one is lighter weight, that is probably one of the most attractive things to air forks as far as the manufacturers are concerned. If they can take a couple pounds off of a motorcycle just by converting it to an air spring, they’re happy to do that. The problem is when you run more pressure. The pressure inside a shock or fork actually pushes perpendicular to the surface of the seal, and it actually pushes the seal into the wall. What it has a tendency to do is make the fork stickier. Every time the suspension changes direction at both ends of the stroke, it tries to stick. What will happen is you give away compliance. On a sand track where you’ve got tons of traction, you may not notice that much of a difference, but when you get into something where traction is poor you will. My perspective is that how fast you can go around a track is, to a great extent, determined by how much traction you have. I mean certainly you have to be able to control that bike as well, especially as things get harder packed. Southern California is classic for that. Traction is a really key factor, so allowing that suspension to move and change directions quickly can have a huge effect on grip. Also, just the initial movement can be felt in the bars and when you ride the bike with spring you’ll notice it’s plusher. I ride mountain bikes quite a bit and mountain bikes are fully air everywhere unless you get into a downhill bike. You get more compliance with the springs and more grip. I’ve talked to some of the factories and they’ve asked if I think they should continue the development of the air, and I’ve said as long as everybody else is continuing to then you should, but at the same time don’t get hung up on the air and the two pounds of difference. Also, continuing the development of sealing designs, which have come a long way with air. Even our oil isn’t a common oil. It’s not cheap by any means, but the amount of compliance it has when it changes direction is extremely good. Things have developed a lot as a result of air forks, but they also benefit a spring fork too. Obviously, air is also very sensitive to temperature, so as the suspension heats up, especially with a rear shock, those air changes translate to spring rate changes. Those are things that need to be addressed and they’re the Achilles heel of the air spring, but like I said it’s two pounds versus the feeling. I tell people to try to the difference, and quite frankly there are kids who haven’t ridden a full-sized bike that hasn’t had air springs on them. So like I said, try the difference.