How to Properly Set Chain Tension - Tech Talk

Frank Galusha demonstrates how to install a chain on your micro sprint car after completing the Blocking Procedure. First, get the axle up on to four-inch blocks, or whatever your model needs to make both torsion arms level (this may require two people). After that, you can install the chain by putting the front sprocket on the chain, feeding it between the chain tensioner wheels, and up onto the countershaft into the engine. Frank suggests putting the engine in gear so that the sprocket can't move and then proceeds to put the nut on the countershaft. Be careful not to put it on too tightly.

Once the nut is tightened, put the engine in neutral, and make sure your motor plate bolts are loosened, allowing the engine to slide. The next step is to feed the chain onto the sprocket and then put the sprocket onto the sprocket carrier. After putting the chain guide back on, the final step is to set the tension on the chain. Frank uses a two-finger test to assess the desirable amount of tension and simply adjusts the turnbuckle and slides the engine to achieve proper tension.

Frank: "There are obviously a few things that are critical about setting your chain tension that you want to make sure you are able to duplicate consistency every time you go race so we don't have any drivetrain issues i.e. torn up sprockets, broken chains right those type of things.

So, the first thing to note is that on a Z-link suspension rear end, as the axle travels up and down, the chain tension constantly changes. I get a common question of “Do I need this chain tensioner, do I need this chain guide?”

The answer is 'absolutely.' You need it because when we show you how to set the tension, we're actually going to run the chain pretty loose. The reason being is as the axle drops, the chain tightens, as the axle comes up the chain gets looser. When we go through the setup blocking procedure, we don't have the chain on when we do that and there's a good reason for that. The reason being is, if you have your chain set to the proper tension for race conditions, it'll be too tight to allow the axle to drop far enough to get on to your setup block.

So, we go through our set up blocking procedure first, then we're going to put our chain on last. That's typically the last thing I do before I push the car on the trailer. So, this is going to be the fun part. What we have to do at this point is, we have to get the axle up to four-inch blocks."

Charles: "And that's after you've already blocked it?"

Frank: "Right, so it's going to be fun. I'm going to need your help because the torsion arms are under tension right now. We might have to be a little forceful. I'm going to force the axle up, I need you to wedge that four-inch block under the axle between the frame rail there. I'm going to sit on this nerf bar, so we don't flip the car off the stands. That's step one. Get the axle up to four inches."

Frank: "On this car, four inches is about when the torsion arms are level. If your car is different, if it's not like one of ours, find a block height that gets both torsion arms level. The reason you want to do that is because as the rear-end travels through its range of motion, at any given point in time, the arm may be at a negative angle, a positive angle, and anywhere in between. We just kind of want to go somewhere in the middle so we can set the chain tension right there, and then it's got plenty of slack to go one way or the other."

Charles: "So, put the front sprocket on first and then the rear?"

Frank: "So, I put my front sprocket on the chain, feed it between the chain tensioner wheels, and up onto the countershaft onto the engine. I'll put the engine in gear here, just so the sprocket can't move, and we're going to put our nut on the countershaft.

Now I run a Suzuki, and other people might have different engines. Particularly on the Suzuki, I just like to get this nut snug. Sometimes if you get this nut too tight, when you go to take it off, if it's too tight it'll actually roll the crank around and it won't loosen the nut.

When I grab my ratchet here, I just literally run it up until it stops. So, at that point, it stopped. It's run all the way into the thread and I just snug it a little bit, that's it. Suzuki's typically come with this retainer and then an Allen bolt to hold the retainer on there. So, this is basically what's going to prevent our nut from coming off ever and this we can actually get tight, we don't have to worry about it. A retainer goes on it, just fits inside the I.D. of that countershaft, and then the countershaft is threaded for this bolt."

Frank: "Once we get that tight, we want to put it back in neutral. At that point we want the chain to roll free because we're going to get that rear sprocket on. Obviously, you're going to have to loosen your motor plate bolts, so the engine can slide. So, I've already gotten that done and then your turnbuckle here is what's going to move the engine back and forth. That's ultimately going to help us get the chain on and off and help us set the tension of the chain.

So, I got the engine pulled back a little bit to make it easier to get this rear sprocket on. We'll feed the chain onto the sprocket first, and then we're going to put the sprocket on the sprocket carrier."

Charles: "Awesome, and you're just lining up the bolts and just sliding it right on?"

Frank: "Slide it on, there you go. Then I encourage people to use one hub, obviously bolts and nuts outwards, so you can take the nuts off and pull the sprocket off and put it back on easy."

Charles: "Then that way you know you're checking your bolts and your hub every time I'm assuming?"

Frank: "Correct."

Charles: "So, as you're putting this together, I'm noticing that the guide block there is a little weird looking, what's going on with that?"

Frank: "Yeah that's something I actually I've kind of come up with on my own. Typically, the block is obviously the full span of this bracket and to get the chain on and off, you have to take the whole block off. Well, what I've done is I've literally cut my chain guide block in half. That way when I take my chain off, I can literally just loosen two bolts and pull the bottom half out; rather than the entire block, and that helps just speed up the process and make it easier to change gears if you need to do it in a hurry."

Frank: "I just want to reiterate the fact that it's important that you do this every time on 4-inch blocks because it's consistency. What I see in the pit area a lot of times is when someone's setting their chain tension, the car will be on the ground, wheels and tires on it; and people will just step on the nerf bar and fold the left side of the car over, so it loosens the chain.

Then they check the tension when the nerf bar touches the ground. I find that there are lots of inconsistencies with that and the reason being is, you might run different stagger so a taller or shorter lever. You might put different pre-loads in your rear suspension to change the ride height, so the distance the nerf bar travels before it touches the ground can vary depending on the situation. We can eliminate all that by putting the axle on four-inch blocks every time. So regardless of what sprockets we're running, what stagger we're running, what preloads we put in our suspension; the axle is always at the same height when you set the tension."

Charles: "You're just looking for repeat-ability."

Frank: "That's it, yeah. Okay, so all we have left is to tighten up the turnbuckle and tighten up the engine plate and we're done."

Charles: "Awesome. Alright, well the chains are on the car, the tension's set. Looks like everything's ready to go. So, thank you so much for the demonstration Frank, and thank you guys for watching."