Setting up a Trek full suspension system

In this comprehensive video Paul demonstrates how to correctly set up front and rear suspension systems on a Trek Full suspension bike to get you set up perfectly for the trail.

Video Transcript

Setting up a Trek full suspension system

Hello, and welcome to this “how to set up your Trek suspension system” video. And weirdly, you can see I’m in front of my computer, not the bike. Why? Well, the reason being is that Trek have got an absolutely fantastic system online, which is the Trek suspension calculator. And you can use this to get your base set up instantly.


So, what I’m going to do in this tutorial, is I’m going to show you how to use the suspension calculator online so you can get your own measurements. Then what we’re going to do is talk through what you need to do to get an accurate weight to get your setting. I’ll probably do that the other way around.


And then finally, we’re going to go out to a brand new customer’s Trek Fuel EX8 and we’re actually going to do the suspension setup as per those settings for the customer. So, hope you enjoy this one, and we’ll see you after the jingle.


Okay, so I don’t know how well this is going to film because obviously it’s a camera at a screen. But the first thing that you want to do is go on to Google or whoever your search engine preference is, and type in Trek. And just as you start typing “sus” for suspension, it comes up with the options and you can just click down to the Trek suspension calculator, click enter. So it will then come up with your whole option menus and we’re looking for the top one which in this particular computer, but it is the, which is the Trek bikes suspension setup, and we’re going to click on that.


So what that does is it takes you into the main menu for the track suspension calculator. And the first thing that you need to know is your weight. Now, this is really, really important to ensure that the weight that you’re putting in is the weight as you’re going out riding. So you need to be in your full cycling kit, preferably with your if you wear a rucksack, put your rucksack on and have the amount of water that you would normally go out riding with also in your pack. So it is shoes, it’s helmet, it’s absolutely everything as if you were going out the carpark and going and riding your bike.


Okay, so once you’ve got your specific riding weight, we then go on to this red button here, which is get started, and then it will open up this next menu, which will allow you to put your bike model year, the actual bike model and your weight in kilos or pounds. So we’re going to click on the model year. First of all, we’re going to click for this bike 2020. The bike model, in this instance is a Shimano XT Fuel EX8 2020. So we’re going click on that. And as you can see that it gives us a nice picture of the bike, which we can go “Yep, that’s the one I’ve got.”


So the final thing that we need to do is put the weight in. Now this particular rider was 76 kilos fully dressed and ready to go and ride but minus his bag. Then emailed gentlemen back and he said, Yeah, normally carry a little bit of water on there. So I’m going to set this up for him at 79 kilos, I’ve just typed in 79. I’m going to click on the kilogramme button. And you now see that the calculate sign has gone from being greyed out to “I can now click on it”. So we’re going to do that.


And it then comes up with all the relevant information you need. So first things first, you’ve got your front suspension. And then you’ll notice rear suspension underneath it. So if we clicked on rear suspension, it will now give us all of our rear suspension setup. And if we go back to front suspension, we can see here what our air pressure needs to be, where our rebound needs to be, and the fork sag that we’ll been looking for. Go on to the rear suspension. We’ve got our rear suspension air pressure, we’ve got our Rebound, it gives you what the shock stroke is, but don’t worry about that too much. And then our shock sag.


So what we’re going to do now is we’re going to take all of those numbers, you’ve got the option here where you can click Print, and it will then come up with a really nice document where you can, you can print that off.


Right, so we’ve got this stunning looking Trek Fuel EX8, Shimano XT version, and we’re going to set up the front and rear suspension system. So the front fork and the rear shock to the correct air pressure as per the Trek suspension calculator. So what are you going to need Well, number one, and I’ve got written on the pre delivery inspection sheet that I’m completing at the moment, the front fork needs to have 80 psi of pressure and eight clicks of rebound. The rear needs 175 psi pressure and seven clicks of rebound. But how do we get there?


Well, you’re going to need just one thing, and that is a proper shock pump. Now, do not under any circumstances be tempted to use a track pump or a hand pump or any other type of pump, ensure that you do use a proper shock pump – doesn’t matter the brand, but as long as it is a specified shock pump, we work in with very, very high pressures, very high tolerances. And also we need an accurate bleed nipple on the other side, because one thing that you never do when you’re adjusting suspension is just with the valve open like it’s like a car type valve but it’s ultra high pressure valve. You never just push the valve into release air pressure because you’ll lose fluids, and you’ll never be able to get an accurate guide. So whenever you’re inflating or deflating your suspension system, it must be done via a proper shock pump. So, that’s a, that’s a real key bit of information.


Okay, so what we’re going to do now we’ve got our numbers, we’ve got our shock pump, most importantly, we’ve got our bike. And what we’re going to do is we’re going to translate all those numbers and show you how to do your pressures.


Right, so we’ve got our shock pump, we know what values we need to put into the actual rear shock itself. So first thing, this is the valve where we’re putting the air in, and the first thing that we need to do is unscrew the dust cover. So that’s the dust cover removed. And then what we need to do is we need to put our valve from our shock pump on to the actual valve itself. Now this is really important that you are very careful when screwing the pump head on to the valve that you don’t cross thread it. If you do cross thread it and it doesn’t feel as though it’s easily going on, immediately take it off and try and put it back on again. If you do cross thread a valve, it then needs to go back to the suspension manufacturer to get replaced. That is not a warranty. So, so do be careful when putting your pump head on to the valve. So we’re going to do that just now. And that screen on nicely, absolutely perfect.


And what we’re going to see as soon as the pump reaches its point there we go and the valve needle has gone all the way around to 150 60 70 80. So it’s actually 180 psi and that and we’re looking for 175.

So because this shock hasn’t been cycled yet now, what does that mean? What cycling shock means is inside the shop canister here, there is a positive or negative air chamber, you don’t have to understand what that all means. I don’t really understand it, so don’t worry. But the top and bottom of it is that those two chambers need to be balanced. So what we have to do is the pump at the moment is showing 180 psi, what we need to do is take the valve back off, so we’re going to remove – so what you have to remember is that hiss that you hear is you’re losing the air from the pump. So what air was in that, that pump section there, you’re not losing any air from the actual shock. So it’s really important you don’t then overinflate your shock thinking you’re going to lose some air when you take your pump off, so a little bit of a tip there.


Now what we need to do is balance the positive and negative air chambers. And what we need to do for that is push down on the saddle so that the suspension goes more than 50% of the entire stroke. And what that does is it basically distributes the air around the positive and negative air chambers, and will give us a true reading as to what air pressure is inside that shock. If you don’t do this cycling of the shock, what will happen is the first time you do go through 50% of the travel thinking you’ve got the correct air pressure, the two will balance and you’ll effectively lose some air pressure and you’ve got then a risk of bottoming out and bottoming out is where the shock goes beyond its natural travel.


You can now see from the O ring that I’ve pushed it beyond 50% of its travel. So that should now have sorted out the balance between the two chambers that sit inside. So we’re going to re-put our Pump on, see what the result is, boom, you can see, hopefully, the pump has gone from what 80 psi to 170 psi. So if we’d have just gone out riding, what would have basically happened would be would have would have bottomed out so we’re at 170. At the moment, we need a little bit more air pressure in there, I’m gonna inflate and then that will be fine. When it cycles through we’re going to get at the right air pressure we’re done.


So, that is the rear shock, air pressure – that’s setup you know the theory how to do it now so you can recycle it, double check your figure and then adjust accordingly. Then also, don’t forget to screw your valve cap back on, you do not want dust and debris and mud and all that sort of stuff going into the valve.


Right. So the next thing after we’ve done the air pressure, we need to adjust the rebound. And all the rebound controls are done by the red knob here that sits behind the compression tune lever, which is just here. I’m going to explain that in a moment. But all of your rebound controls are in red. Same on the fork. You’ll see it in a moment.


Now there’s a little diagram on the front of the sticker of the shock. And that will tell you in which way you’re turning the red dial, it’s going to tell you whether it’s going to slow the rebound down or whether it’s going to speed the rebound up. What does this all mean? So the air pressure that’s inside the shock controls compression, what’s compression? compression is the shock travelling through its travel. Rebound is the speed of which it then extends back open again and recovers. If your rebound is too slow, and you’re going over a section of bumps, it’s going to keep compressing, compressing, compressing, it’s not going to recover back up to its total travel, and you’re going to bottom out.

If your rebound is too fast, then what’s going to happen is, is that it’s going to feel like a pogo stick. It’s just gonna be Bounce, bounce, bounce, bounce, bounce, and we have no, control on the bike. So it’s important to adjust the rebound and the rebound is adjusted as a ratio of what air pressure is in so you’d have more rebound, the more air pressure you’ve got in there, you’ll have less rebound for less air pressure in there, so that’s why the Trek suspension calculator is so good.


What is important is that your rebound – so where it says clicks out – is when the shock or the fork is in its slowest position. So I’m going to turn this dial – hear it clicking – all the way until it’s gone to its slowest. Then according to the numbers, the rear suspension 175 psi, we’ve got that and we need seven clicks of rebound. So, on the dial, we’ve got 1, 2, 3, 4, 5, 6, seven. Perfect. That is that suspension system setup, we’ve got the right pressure, we’ve got the right rebound, perfect.


The fork air pressure is done off the left hand side of the suspension fork as you’re looking from the back of the bike. And the first thing that we need to do is we just need to remove the cap cover and it says air on it and again, doesn’t matter whether it’s a rock shocks or suspension, it’s it’s done the same. We then take our shock pump again.


And what want to do is again, being very careful with the threads what we want to do is just screw back on. And again you just seen the needle off the valve and we are showing here 80 psi, and we are looking for 80 psi. Now, unlike the shock, you do have a negative and a positive air chamber in a fork, but it’s not as sensitive. So if that’s saying 80 psi, I’m happy that that’s 80 psi on the fork, so we’re going to leave it there. If it was showing 90 psi, then we’d just use the bleed valve to reduce. If it was less than 80 psi then would obviously just use the pump to inflate.


That’s our air pressure. We’re just going to put our cap back on the top. don’t over tighten this. Just nip it up. That is it. So that’s the air pressure sorted out. We’re now going to move on to the rebound on the fork.


Okay, so we’re on the right side of the fork now. And on the right is where all of the damper part of the fork is working. So the left hand side is where the compression happens and then the right hand side is where the damper happens. So on the underside of the fork, you will see a red knob. Now sometimes that rebound knob on certain forks is covered by another cap. You just need to unscrew that cap and then it will reveal your red adjuster know but it’s always on the underside of the right hand side of the fork.


Just like the rear shock. You will have a sticker on there that will on a rock shock system it’s got a hare for obviously faster and a tortoise for slower. On Fox they use a plus and a minus. On all of them we’re wanting to again like the shock wanting to turn the adjustment knob so that it’s in its slowest. So on a rock shock system, we’re going towards the tortoise on a fox system, we’re going towards the plus which is increasing the amount of rebound that there is.



So we’re going to turn that all the way towards the plus – that’s it – and we are on the slowest rebound. Then again back to our sheet which has got all the numbers on there. On the front we need 80 psi. We’ve already done that. And then we need eight clicks of rebound towards the faster. So from the slowest we need 1, 2, 3, 4, 5, 6, 7, 8 so that is now dialled in 8 clicks of rebound. Perfect.


Right, so the final thing that we want to do now that we’ve set our air pressure up and we’ve set our rebound settings up is we just want to test those settings. And we can do that just by feel. So what we want to do first of all, is let’s check the fork, we want to pull the brakes on because we don’t want the bike moving away from us. So with the brakes on, push down on the fork, and I can feel that the suspension is just returning with my hands nicely. Again, if it felt as though it was springing back against my hands, it’d be slightly too fast. But if as I was pushing down, so pushing down and then as I released it then took an age to return back to the top. The rebound will be a little bit too slow.


Moving on to the back of the bike. Again, if you’ve got a dropper post drop the saddle down, which makes it easier to push over the top of the bike. And again, we push down through the suspension, it’s just returning back perfectly with my hands. So that is our suspension system set up ready to go on the trail.


And then you can just dial one or two clicks of rebound front or rear to then just tailor the way that the bike handles. And again, you can contact us if you want slightly more nerdy information on that but that’s the Trek suspension system and just following what we’ve done there, it’s just a really great way of getting those base settings that will feel really nice out on the trail.


So thanks for watching this