STFU Chain! – Kovarik's Silent Solution
Remember when you had to wrap the driveside chainstay of your prized new bike in a piece of inner tube? After buying a brand new bike, this was a bit of an insult. Thankfully recent developments have mostly eliminated the need for this chain damping technique but some people want their bikes quieter still. Today, extra strips of velcro or rubber mastic tape are sometimes added to quieten things more but Chris Kovarik went a different route.
A few years back Kovarik’s bike was spotted in the Whistler Bike Park with a strange looking formation of zip ties between his chainstay and seat stay. Following that he was seen rolling around with a Fox 40 bumper strapped to his chainstay and the chain running through it. These are two of the earlier options Kovarik worked on to silence his chain. He also rode chainless heaps just to get rid of the noise. There are other benefits to riding chainless but Kovarik’s primary focus at that point was silence.
Riding to the sound of your tires slapping and sliding over the ground is pure bliss. But riding with the sound of a chain flapping about can be torture! Another Aussie, and an acquaintance of Kovarik’s from Brisbane, Jaan Hurditch, saw what Kovarik was up to and thought it was great. With his engineering background, the two were able to clean up the design, make it more adjustable, work on trail bikes, and create options.
Now the two are launching their STFU Bike (Shut The F*ck Up) Chain Dampers for the world to run quieter bikes. I got together with them in Whistler earlier this spring to learn more about the product, its evolution, and how STFU Bike came about.
AJ: Chris, how long have you been doing this on your bikes?
Kovarik: It didn't really occur to me at the time, but when I first started riding Intense Cycles—the M1—Jeff (Steber) used to make this little alloy device—an L-shaped device—and put it right here (Kovarik points to the front of the rear triangle at the chainstay). It was attached to your chainstay there and it went up beside the tire, probably like an inch and a half. And he put rubber—some sort of rubber backing tape on there to stop the chain slapping and going into the tire. And then you usually had cut bike tube over the chainstays too. But that was the start of it, I think. He (Jeff Steber) was trying to reduce the noise and chain slap.
Was it like an extra bit he would just weld on to the team bike chainstays?
Kovarik: Oh, it was just this little bit of alloy that he'd drill and screw with two screws in there. But yeah, I mean, that was my earliest days of seeing something to, you know, quieten down chain slap.
Did you ride for a period without anything like that? And you know, then sort of thought back to it and…
Kovarik: Well pretty much we all used to wrap our chainstays in bike tubes.
Kovarik: That was the solution really. It was heavy but it worked, it was guaranteed. But yeah, it wasn't until probably six years ago I started playing with the idea here in the bike park… Just something to silence chain slap. And I think I started from… I cut a PVC pipe, like an inch and a half in diameter and strapped that to my chainstay with a zip tie just like the fork bumper but plastic. That worked but it was still a little bit noisy. From there I think I just started using zip ties.
Jaan: That's what I remember…
Kovarik: Yeah. I zip tied… I think It was five or six zip ties in a configuration of circles from your chainstay to your seat stay—with a little loop in the middle. And that worked but the zip ties kept snapping and catching the chain. Then from there I went to a fork bumper and that worked well for a year or two and then…
Then got serious?
Kovarik: Yeah, then got serious.
What made you think, hey, let's put something that the chain goes through rather than strap more and more shit to the chainstay, like most of us plebs out there.
Kovarik: Hahaha. Yeah. Good question. I just think with the zip tie idea, the PVC pipe idea… it was a little circle that controlled your chain from slapping side to side and up and down, but made a noise. But it was controlling (the chain) and there wasn't any friction, unless it was bouncing. So we wanted something that was going to quieten your bike down, and be frictionless. Not like a roller, you know?
Yeah, which creates drag.
Kovarik: But then, yeah, from the fork bumper… Yeah, Jaan kinda came into play with his design making shape more refined. So as you change gears, you have your chain run through the same angle as the STFU.
Jaan: Just to limit the amount that it (the chain) can actually move. I mean, they are sort of bigger than they really need to be, but it's just so it fits a range of bikes. Because the swingarms are all in different places. So you kind of tilt the top by rotating it where you want but the bottom is sort of fixed in a way. It will move out if the swing arm is wider. Depending on your chain line we found we had to have it shaped slightly larger at the bottom, so it accommodates as many bikes as it can. Working down at Vorsprung and Evolution and stuff just, you know, got the boys there to try them out and tried them out ourselves. So we tested it out like that and obviously drew it up in C.A.D. as well—to a couple of different bikes that we had access to—to be able to make sure that it was spot on.
Kovarik: On that note too, um, my idea was to… 'Cause I come from racing my idea was to always try to quiet my chain down while I'm racing, so I can focus on my line choice and like, just getting down the hill fast, right. Instead of all this excess noise.
Jaan: Clanging and clattering and distracting ya.
Kovarik: Yeah. But then, I only realized not long after that, um, having the STFU or a chain device for your trail bike was awesome because it cut down the noise of just riding and enjoying time outside. Not all of us are going to race our trail bikes like enduro these days, but just cutting down the noise on the trial… The STFU really helped that so you can enjoy the great outdoors, you know what I mean? Instead of getting out there and f*cking listening to your chain slap around all over the trail.
So the inspiration came from downhill, but at the time you hadn't really considered it for a trail bike?
Kovarik: Yeah. Nah. So now it works both ways.
That's pretty much how I had it. (Finishes replicating his old zip tie technique on his M29.)
That's awesome. I do remember seeing it now, hey…
As soon as you started putting ties together I thought; "Oh yeah, I've seen those." But you found the chain kept binding in it and snapping it and stuff?
Kovarik: Yeah. It would flex and catch edges, pull it and snap it (the zip ties).
Kovarik: But a lot of guys copied that in the bike park and back home (in Australia) even. It's pretty funny aye. A couple of guys on the coast and Boomers (Boomerang Bike Park in Queensland, Australia) and couple of guys back home on the national circuit.
Do you think that a chain guide is still needed running an STFU?
Jaan: I don't know, It depends hey. It helps. It helps keep it on track cause it's less likely to bounce and then as you pedal, get rolled off. Especially with a narrow wide ring, you know. To be honest, I haven't actually tried without a top guide. I always just run one because even with a narrow wide, just every now and then it comes off. And I hate that.
Kovarik: I guess it depends on what type of riding you do. There are no rules, right?
So once you started working with an actual final product in mind, how many iterations do you guys think you went through to, to get this shape and stuff? Or was it kind of like, you planned it out really well to start with and measure twice, cut once sort of thing?
Jaan: No, we printed up a fair few, hey. I think we probably printed up and tested well over a hundred
Kovarik: You'd know, yeah. In your garage there, printing them out.
I think we probably printed up and tested well over a hundred. – Jaan Hurditch
Okay. So how long ago was that?
Kovarik: End of last year, hey?
Jaan: Oh, like probably… it was halfway through last summer.
Yeah? So you got on it hard.
Kovarik & Jaan: Yeah, yeah. Pretty much.
Tested one-hundred of them in like, six months…
Jaan: Yeah, well, I mean we handed them out to the guys at the shop and friends and stuff like that. And just, yeah, our own iterations as well, just trying to refine it. Like, we started just with one in the middle and then, I think it was Chris, like you were kind of… You sent me a message about it and I was like, yeah, f*ck, I've got the same setup on my bike, I just did it yesterday. We'd done the same thing… We were using a trail with the DH seven on the front as a combo just to try and, you know, stop the chain moving even more. And so that was kind of weird that we both kind of came to that conclusion within the same couple of days. And then we had to sort of change out a little bit just to, just to refine it to that new position.
And then there was all the, like I was saying before, all the measurements of the different bikes and you know, even with boost and stuff, all the swing arms and everything change a little bit, you know. They're not all in the same position. So like the width, you know, relative to where the chain sits, changes depending on what frame. So yeah, we just had to try and come up with the best compromise that was going to work with as many frames as we could get our hands on.
So what has it been on? Obviously Intenses…
Jaan: Yeah. Intense, Specialized…
Kovarik: Giant, Santa Cruz…
Kovarik: YT, Norco…
Are these mostly downhill bikes?
Kovarik: Trail bikes…
Jaan: Yeah. Trail and downhill.
Jaan: There are a couple of others that it doesn't work great with. A buddy of mine rides a Maiden with 26-inch wheels and with the 26 the chain's like, that far away from the chainstay (shows a gap of millimeters between his fingers). So it just doesn't fit.
Kovarik: Yeah, the Maidens are close. Forbes, (Dylan) has a Maiden, and his chick, and they work fine…
Jaan: I think with 27.5 wheels, they work.
Jaan: 'Cause they move the axle up to a different hole.
Jaan: So the chain moves up. But yeah, there are definitely a few bikes that it won't work with. And also with bikes that have the swing arm above the chain, like your Orange's and stuff like that. You've got to have a minimum, and it's about 10mm minimum clearance that you need between the swing arm and the chain, when it's in the hardest gear. And then if you measured that and there's at least 10 mill… I mean, you'd probably get away with it with maybe 8 but then it'd be very, very close.
Chris, when you were running the zip ties, was it just one in the middle like that? I thought I saw two at one point?
Kovarik: Yeah, I started off with one and then went to two. It did look shitty but for the amount of time I spent in the bike park. I just was like, all right, I don't care about looks, I just want my bike quiet.
Yeah. You said before too, that you rode chainless a lot because you wanted the bike just to be quiet.
Kovarik: Yeah, that's it. It's like riding chainless, with the STFU set up, man. Yeah.
Actually, before I forget. It's funny 'cause the last NW Cup we raced, in the afternoon after practice a guy came down and he was like; 'I just wanted to come down and see how come you guys looked so smooth and quiet.' We had a couple guys say it.
Kovarik: It's funny because looking smooth and being quiet, it's kind of the same thing.
Yeah. So how did you guys come together on this project?
Kovarik: I knew Jaan was an engineer and, well, you were working at Evolution at the time.
Jaan: Yeah, I was doing some part time work at Evolution at the time…
Kovarik: And I'd always be in there 'cause Evolution supports me and I work on my bike there too, and they've helped me out.
Jaan: Yeah. Well I guess I just… I mean I've known Chris since 2002 or something…
It's like riding chainless, with the STFU set up… – Chris Kovarik
Oh, back from Brisbane days…
Jaan: Yeah, back from Brissy days and ah, just saw the evolution of, you know, zip ties and then Fox 40 bumper and I was kind of like, f*ck dude, that… And then I started running a Fox 40 bumper and I was like, this thing's rad, like, it works, you know, it's not perfect but it works. And so I was like, Chris, let's make these things, let's engineer this, you know, let's dial it in and yeah, so…
I know you kinda well. You always seem to be tinkering or looking for something to have a tinker with, with your engineering background. So it was just natural for you to be like, you know, thinking about it and try to make it better and stuff?
Jaan: Yeah, for sure. Mountain biking's a big passion of mine and who doesn't like a quiet bike.
Kovarik: Thing is too, I didn't even know you had a 3D printer so I didn't even think of like, asking anybody to print something up to test. Like that was one of the things… I didn't know what direction to go or who to ask about getting a sample made up.
Jaan: Yeah, so I can't really remember the exactly moment. It was kind of more… I don't know, having a beer or something at the GLC maybe or whatever.
Jaan: Yeah, or doing some runs or something, yeah.
How did you sort out the tooling stuff? As Chris said there, you have ideas but then you need someone who actually knows how to go about sourcing manufacturers and stuff like that.
Jaan: Yeah, I've done that in the past. Um, I've got another little product that I've had injection molded and yeah, just jumped on Alibaba to be honest. Yeah.
Yeah? They've got manufacturers on there?
Jaan: Yeah, it's a little bit difficult to sort through but they've got ratings and guarantees on there, you know, if someone rips you off or whatever. So, yeah, I found them that way and it seems to be pretty good. You know, the first lot has got a couple of little errors, but the company is fixing them up and they've been fairly good to work with so far. So, yeah.
Is it cost prohibitive to like, a regular Joe, Are you guys having to put a good chunk into this?
Jaan: It's a decent amount of money, for sure. Yeah. You need to be pretty set on it. I think all the design side of stuff… It's definitely a big component. Probably the biggest component if you were to go to an agency or something.
Jaan: We're kind of lucky because I'm able to do that.
Kovarik: I think too, we're confident that it works and know that it's going to sell, and as long as bikes have chains they're going to need… If you want a quiet bike it's going to need something like this to shut it up. So yeah, we have thrown a chunk of money into it. But like I said, we're confident it's going to be successful.
Jaan: Quietly confident anyway.
When seeing the earlier versions online, it looked like the loops were adjustable. Are they?
Jaan: The loop isn't, nah. That's why we've got the three different combos. There's one for 7-speed downhill, one for 10-speed.
Jaan: Yeah, and one for a trail bike, which suits anything up to an Eagle drivetrain. It's kinda like… that's the one thing that is fairly standard. You've got the chainring, then you get your cassette and that's the sweep angle that the chain goes through. It's kind of constant. Like the chainstay might change in length slightly, but it doesn't really affect the positioning of the chain that much at all. It's only a few mill of different sweep then. So we've kind of tailored them to suit those three drivetrains.
Does the chainring size affect it much?
Jaan: It just affects how you cut the STFU to size.
Jaan: So where your chainring is, its got a fixed point and it just moves on your cassette, so its always swinging out through that arc. Right? That's one of the things we've got in the instructions too. If it's rubbing, move them forward because moving them forward you've got less swing, like, less arc length.
Okay. Yeah, the closer you are to the rear, the more that changes.
Jaan: Yeah, so if you move them forward, you've got less change in position and so, the clearance increases.
What are they made with? You said you're going through sort of final process on that.
Jaan: Yeah, it's silicon. It's pretty much inert (chemically inactive). Um, so you can use it to bake with and stuff. People use it for high temperatures, it's fairly resistant to chemicals and the sun. Um, obviously this is for outdoor use, so we don't want it like, degrading with temperature or U.V.
My experience with like, the cupcake things that are made out of it… They can go in a 400-degree oven and it's fine.
Jaan: Yeah, exactly. So that's why we went with that.
Kovarik: We could probably touch on compounds too, that we're testing…
Jaan: Yeah. That's what we're doing at the moment, hey. We've got samples and the original samples were just too soft. So we've got like, 35 and 50 at the moment. This is a 50. It's way too, way too soft. So we're going a little bit harder.
And 35 would be even softer…
Jaan: Just way too soft, yeah. We basically… The thought process with that is we wanted them to be as soft as possible, but they still held their shape. With the softer, obviously they have better damping qualities. So it's going to quiet it down even more.
Jaan: But we just took a bit of a stab in the dark and didn't really realize how soft it would be, haha.
So yeah, we've got sixties and seventies coming and I think we'll probably settle around 60, I think. But we wanted to go a little harder as well just to make sure. Cause every time we get samples it takes several weeks, so, we just want to get them done. Plus there are a few tooling changes that we're doing with, uh… Like I was saying before with the trail, we're stiffening it up by making that section a little bit thicker so that it's more rigid and we can still run a softer compound.
Finding that balance is where you're at, hey?
Jaan: Yeah. I mean, we don't want them to be heavy, you know, we want to try and make them as light as possible. But, you know, we need it to be stiff enough so it's not going to go into your spokes or whatever. You still want it soft so that it's going to dampen the chain noise.
So, it's probably not as big of a concern on the downhill side of things, but the trail bike side might be interested in the weight. Are you guys aiming for a weight there or is it… I mean, that feels light as, but…
Jaan: Yeah. I mean, the idea is for it just the weigh nothing.
Kovarik: Yeah, pretty much.
Weigh as much as a zip tie wrapped around your chainstay.
Do you have a final weight for each of the sets?
Jaan: Overall, the uncut weight for the Trail set is 75 grams, although most people will cut them down to a weight of around 40 grams. Both DH sets weigh approximately the same at 60 grams uncut and about 30 grams once cut to size.
How have you tackled the issue of chain drag and resistance? I guess the idea is it doesn't even hit ideally, right?
Kovarik: Yeah. That's the idea. When you're powering or pedalling, you've got no friction or resistance from the STFU. It's only when you're going across bumps, rough terrain and stuff like that, it's going to obviously rub but the STFU is gonna stop it bouncing into your tire, chainstay and seat stay.
Jaan: Yeah. When the chain's under tension it won't move. You know what I mean? So whenever it's under tension, it's not touching. And that's testament to Chris running a Fox 40 bumper in the park for, you know, a season or whatever. He didn't have to replace it. So, as long as it's adjusted properly, that's key. You know, you can't be rubbing in any gear.
Jaan: We also tested… So when your bike's sagged into the suspension, the position of the swingarm can change. So, you need to account for that as well in setup. So whether you just sit on your bike afterwards or take the pressure out of your shock or whatever and you cycle it through that travel, just a little bit. Obviously you're not going to be bottomed out when pedaling, but you might be a third or more into the travel when you're grinding up something. So you need to make sure that it's not rubbing otherwise it will wear out quick, because they're only soft. They're not meant to resist the chain grinding over it. It's just meant to resist impacts from the chain.
Kovarik: Yeah, that's a good point. We've allowed for an extra little bit of diameter in each model for that reason.
Jaan: Yeah and like I was saying before, you can also shift them forward a little if it is rubbing and it gives you more clearance.
Kovarik: Well that's the beauty of aye. You don't have to fix it in one spot, it's adjustable. Up and down, forward and back, you can twist it on your chainstay.
Who do you feel will benefit most from an STFU chained damper…? The obvious answer is everyone, coming from you guys, but…
Do you think the downhillers will appreciate it more than trail riders or is it the other way around because trail riders have such long chains?
Kovarik: Yeah, good point. I think obviously a downhill bike with the correct length chain set up, it's going to be quieter. But then like you were saying, on a trail bike you've got so much more chain length and growth.
Jaan: We did look into putting one on the bottom as well. Um, but in the slow-mo footage and stuff we did, the bottom chain doesn't often hit the stay.
Kovarik: Exactly, yeah.
Jaan: It's so far away essentially. Like it just, yeah, especially if you're running a guide. But even without, it's just a lot further away and it's out of the way of the swingarm, so we didn't really see a need for that.
Have you found when you do hear something now, it's because that lower section is actually… cause it does make contact every once in a while, right? Just nowhere near the same amount.
Jaan: Yeah, true.
Now that everything's so quiet when you hear the chain now, are you like, that was the f*cking bottom hitting.
Kovarik: Nah, you know what I've found. Because on my trail bike now, it's so quiet, what I hear now is my derailleur actually coming back and making that sound (Kovarik demonstrates with a derailleur).
Oh yeah, the clutch smacking back.
Kovarik: Yeah, I've never heard that before. Now because it's quite, I hear the derailleur. You find new noises. On the DH bike, I don't hear it but on the trail bike, I do.
How will the sets be sold?
Jaan: We have a set for Trail bikes that suits 1x drivetrains with up to a 50T rear cassette (Eagle), a set for 10-speed DH drivetrains and a set for 7-speed DH drivetrains.
Are you going to provide a guide for which bikes it will and wont work with? How do you mitigate someone getting one and not being able to use it?
Jaan: We're working on a list of bikes we have tried and tested, and have a compatibility and fitment guide on the website already. Anyone looking to buy a set should check this out first. We will accept returns on uncut product but can't take them back otherwise, so check out the guide. Measure twice, cut once.
Do you guys have a retail price you're going to sell these for yet?
Kovarik: We're selling them as a package of two, as a combo.
Jaan: Yeah, it's 39.95 Canadian and 29.95 US. They'll be for sale on STFUbike.com