The rear derailleur on your mountain bike has two limit screws that prevent it from moving in or out. If you take a closer look at a moving derailleur, you will notice the limit screws in action to stop it at both ends right at the end of the travel. How to adjust the rear derailleur on a mountain bike will be the topic covered.
The primary objective here for the limit screw is to stop the chain from entering into the frame or the spokes of your mountain bike. If you tighten the H-limit screw, it will also restrict its limit. And we will discuss this in the following text. By tightening it, our objective here is to get it to dial as close as it can to your bike’s inward cog.
Several people want to adjust this setting according to their riding style and preferences. In this article, we are going to get into all the details associated with a rear derailleur adjustment. To Adjust the rear derailleur is not that difficult if you have the proper tools and understand the basic derailleur functions.
How do you Adjust a Mountain Bike Derailleur?
Thinking about how to adjust the rear derailleur on a mountain bike but don’t know where to start…! Don’t worry, because you are not alone. We are going to talk about this matter in detail and you will be able to get the job done with minimal effort.
What Tools Do I Need to Adjust my Rear Derailleur?
- Bike Stand – Park Tool PCS-9.2
- Hex Wrenches – PRO BIKE TOOL Torque Wrench
- Chain Lubricant – Finish Line Dry Bicycle Chain Lube with Teflon
- Cable Cutter – Park Tool CN-10
- Screwdriver – PRO BIKE TOOL 6 in 1
- Cable Extender – Park Tool BT-2 Fourth Hand
It’s About The Cable Pull Not The Limit Screw
Several people think the H-limit screw needs to be in the right spot. But the derailleur is being stopped by cable pull. So, you need to turn your attention towards the spring that is constantly pulling your Mountain bikes derailleur outwards.
Whereas, the cable pull is always in the opposite direction. With your shifter, you can change the cable by pulling in small increments. These increments in the shift are linked with the cogs. When you shift to the smallest cog, you will see everything becomes ideally streamlined.
At this point, the derailleur is in the place due to the cable pull and not the limit screw. Now, your H-limit screw might not be placed correctly but you can determine until you get the cable pulled out of this equation here. You can do this with the help of the barrel adjuster for your derailleur.
Begin Your Inspection
Before you adjust the rear derailleur start with a visual check of the hanger on your derailleur. If you notice it’s bent, any of your adjustments won’t work. Therefore, you need to go for the hanger alignment first before anything else.
If your mountain bike has more than two chainrings, the front shift to the largest one and rear shift to the smallest cog. Make sure none of the clicks are left for you to read the smallest cog on the rear. It will ensure your rear shifter is actuated fully outwards. If your chain doesn’t shift to the smallest cog on your bike, either the cable settings are stopping it from doing so or the limit screw.
You need to turn the H-limit screw anticlockwise a few times. Now, pedal and check if the shifter moves outwards or not. If you are still unable to move it, then turn the barrel adjuster clockwise just a few times and run another check.
This time around your chain will shift to the cog that is the smallest. You will also see the rear shifter has run out of any clicks too. Turn the barrel adjuster a couple of times again until you can screw it.
We are doing so because it will move all the shifting positions beyond your bike’s limit screw settings. Consequently, you can get the precise assessment of your current settings of that limit screw. It’s time to dial into the H-limit screw adjustment.
Adjustment for The H-limit Screw
If there are no markings on the limit screws, you have the option of just picking one and start turning it in and out. But, keep your eye on the derailleur. If you see no movement in your derailleur you may pick the other limit screw. The correct one will make your derailleur move and it will be the H-limit screw.
You need to find the right setting by tightening the adjustment for this limit screw. Try to back it out until you see it sitting right under the smallest cog. With the help of a screwdriver, tighten the screw by half a turn.
Now, start pedaling and check if there is any excessive noise you hear from your bike’s drivetrain. If you don’t hear much noise tighten the limit screw more until you start hearing the chain hitting and rubbing on the derailleur’s next cog.
When you start hearing the noise start backing out the limit screw a quarter at a time and keep doing so until this noise stops. Once the noise stops, you have successfully adjusted your H-limit screw.
It’s time to turn the barrel adjuster anticlockwise twice with an idea to bring it back where it was in the first place before you adjusted the limit screw. You don’t have to be too careful to be precise in your turns. We need to adjust the indexing before we start working on the L-limit screw.
Adjustment of Indexing
The process of adjusting the indexing involves lining up the guide pulley with those cogs in a way that each of the shift increments properly lines up with the cogs. You can do this with the help of the barrel adjuster.
There are different adjustments for indexing that are acceptable for various preferences and requirements. There might be more than one position for your barrel adjuster that assists in optimal gear shifting performance.
Keep The Shifter Farthest Out And On The Smallest Cog
If your mountain bike has two chainrings on the front, you need to stay focussed on the larger chainring. And if your mountain bike has three chainrings, you need to focus on the middle one. Begin with the smallest cog on the rear and pedal with normal cadence.
Now, shift one click and it must shift a gear. If you notice your chain doesn’t shift to the next gear, shift back to the most outward click. Turn your barrel adjuster to a single full turn anticlockwise.
Try another shift and continue doing it until the shifter completes its shift. If during this process your barrel adjuster has come out or is close to coming out, thread it back in and pull out one of two turns carefully. You need to make sure that you are on the farthest out and are on the smallest cog. At the pinch bolt, it’s time to remove the slack from your cable.
What If The Derailleur Shifts Two Sprockets With One Click?
In such a scenario, you need to shift to the first cog and turn the barrel adjuster clockwise to shift again. Your chain will now be on the second sprocket with one shifter click. You can fine-tune your shifting in a precise manner.
Turn your barrel adjuster to the limit where you see it’s outer side. Upon pedaling, you will hear some noise. You have to be sure its source is the chain hitting the next cog. Turn the barrel adjuster slowly clockwise and keep turning until the sound goes away.
For this cog, you are at the most adequate setting. It’s time to check each cog in the cassette like the Shimano 10 speed cassette. You need to shift and listen for each position one at a time. If you hear a noise in any cog just make a quarter turn clockwise with the barrel adjuster and run the test for cog again.
Carry on with this process for each cog and make adequate adjustments. Just exclude the largest cog for now because you will work on that later. Shift outward in each cog and check for any excessive noise to ensure good shifting performance. By doing so you have adjusted your indexing properly and it’s time to turn towards the L-limit screw.
Adjustment of L-limit Screw
Just like the H-limit screw, you will start tightening the L-limit screw. Back it out slightly up to an extent. You are doing this to keep your derailleur shifting safe and prevent it from shifting beyond the largest cog and going into the spokes.
Shift your chain to second to the largest cog for determining where your L-limit screw is set at the moment. If your chain is not making the shift, your L-limit screw is a bit too tight. In case the chain is shifting slowly to the largest of the cogs, it is again due to the L-limit screw being too tight.
If you are hearing some noise while the chain is on the largest of the cogs the L-limit screw is again a bit too tight. If the shift is acceptable and there is not much noise the L-limit screw is not tight. You need to shift your derailleur by one click out and tighten the screw a single clockwise turn and run a check.
Keep doing so with similar increments until you start noticing the L-screw is getting too tight. After seeing the symptoms you need to turn the L-limit screw out a single quarter and run the check again to see the shift towards the largest cogs.
You are doing this to get rid of the symptoms of excessive noise and slow shifting. Once they go away, you have adequately found the right setting for your L-limit screw. You can put some additional pressure on your shifter and check the rear derailleur. The cage shouldn’t move inwards.
Body-Angle Screw Spacing
In most cases, derailleurs come with some kind of adjustment for the spacing between the cogs and the guide pulley. You can control this caping with the help of a body-angle screw which is also known as a B-screw. You can check this adjustment when your chain is right on the smallest of the sprockets in the front and on the largest cogs at the back.
Most mountain bikes like the Mongoose Tyax Comp need to have a gap of at least five millimeters to six millimeters. With the help of a hex wrench, you can easily measure the distance. If your mountain bike is shifting well your body-angle screw might be within its acceptable range.
To increase the gap you have to tighten this screw and vice versa. If you have noticed that you have made a significant change to the body-angle screw, double-check your indexing adjustment. If everything is on track, you are done with your rear derailleur adjustment process.
6 Tips to Adjust the Rear Derailleur on Your Mountain Bike
There are some important tips you need to keep in mind to go through and adjust the rear derailleur. These tips are as follows:
1. Properly Aligned Derailleur
Before you start working on the derailleur adjustment, you have to run a check and see where it is in proper alignment itself or not. If the alignment is not proper, making any adjustment to it will go in vain. Have a look at the derailleur from behind. Those two jockey wheels need to be lined up with each other and the cogs.
2. Set The Limit Screws With The Gear Cable Disconnected
Before you set the limit screws you need to disconnect the gear cable. And gently start pedaling forward. You are doing this to drop the chain on the smallest sprocket. Now, find the crosshead screw marked with H towards the derailers back.
3. Tighten The Cable Adequately And Attach It To The Body
When tightening the cable after turning the barrel adjuster, you can use a cable anchor to attach it to the body. Don’t allow it to lie down without any support. It is important because you need to adjust its tension as well.
Make sure you don’t hear any noise when you are pedaling one you are done. Cable tension is critical and you need to go through your gears to find out whether it is too tight or too low. In most cases, it will be too low and it will result in a hesitant derailleur in shifting up towards a larger cog.
To solve this issue you have to unthread the barrel adjuster by a click at a time. Each of these clicks will make a significant amount of difference. If you unthread it too far you will create a higher tension in the cable and in such a case you will have to thread the barrel in and vice versa.
4. Moving Up The Cogset Is Okay But Moving It Down Is Not
In such a situation the housing or cable might be corroded and it is resulting in drag. The drag won’t cause any issue in moving up but moving back would be a problem. You should clean and properly lube the housing and the cables or you can go for a replacement as well.
5. A Grinding Sound On The Largest Cog
You might also experience a bang or grinding sound in the largest of the cogs. It results from the upper jockey wheel running in the largest of the cogs. You need to tighten the B-screw and keep tightening until the noise dies down.
6. Skipping While Riding Under Load
One of the most common problems you might face in the process of adjusting rear derailleur is that you experience skipping when you are riding under load or climbing a steep slope. Well, this happens when your drivetrain has worn out and it’s time to replace it.
With each gear shift, it stretches a bit and with each stretch, the gear and the front face wear down. When the chain stretches beyond a point where it tends to mesh with your MTB’s gears, you will start experiencing skipping when riding under pressure.
Just a quick recap of the points on how to adjust the rear derailleur on a mountain bike as discussed above are:
- Locate your H screw and shift into the smallest cog and turn the screw out a few turns. It will make the chain want to cog off. Thread the screw in till the noise diminishes.
- Find the L screw and shift into the largest cog and back the screw a few turns. The chain will want to shift off into the spokes. Thread the screw in again until the noise fades away.
- Keep the pulley close to your cassette cogs. If too close it will create noise and if it’s too far off then shifting will be poor. Find the B-screw and thread it in/out to adjust the pulley.
Working on your bike can be a lot of fun. But it will be a good time only if you know how to handle this equipment and understand how they work. If you have no idea about any DIY projects associated with your mountain bike, we will advise you to visit your nearest bike shop to get the adjustments done for optimal performance.
There are problems that even the most successful DIYers can’t resolve on their own and in such a case, you need to visit your local bike shop as well. The point we are trying to emphasize here is if you haven’t been able to resolve the issue on your own for a long time and you think your bike is still underperforming even after all your efforts it’s time to get some professional assistance.