No matter where you’re riding your mountain bike, you want the gears to shift smoothly every time you engage the shifter. There are few things worse than having the front derailleur toss the chain off the ring since this makes it impossible to continue your ride until the issue is fixed. It is also quite unsafe when you lose that pedal control.
Luckily, learning how to adjust the front derailleur on a mountain bike is easier than you may think. Even those who have never attempted to maintain their bike before can learn the process of a mountain bike derailleur adjustment in no time. Doing it yourself also saves you the hassle of taking it to a specialist, getting you back on your bike quicker without costing you a cent. The following sections can help you with your MTB derailleur adjustment.
Front Derailleur Overview
The front derailleur of a mountain bike is made up of a few simple parts. When Trusted SourceBicycle Requirements Business Guidance This regulation increases the safety of bicycles by establishing, among other things, requirements for assembly, braking, protrusions, structural integrity and reflectors. Bicycles that fail any of the requirements are banned under the Federal Hazardous Substances Act. www.cpsc.gov , the cage of the front derailleur pushes the bike chain to the side when you shift gears, forcing it off of one chainring and onto the next one down. When you need the chain to go back onto a larger ring, the derailleur pushes the chain against the side of the larger ring until the teeth snag it and yank it on.
No matter what type of mountain bike you have, there could be a front derailleur on it to help you shift gears. This includes full suspension mountain bikes for tackling those difficult technical trails or cheap mountain bikes for beginners or those on a budget. Even smaller 24-inch mountain bikes for kids can include a front derailleur.
There are a few different derailleur types, though only a couple of them are used on mountain bikes. There are also derailleurs designed for double and triple chain wheels. Front derailleurs also often have designated speed options, like the Shimano Front Mech Sora model, which is a 9-speed compatible triple braze-on mount model.
Regardless of the derailleur you’re bike uses, the basic parts are the same. These include the derailleur cage, anchor bolt, pivot points, positioning clamp, and both low gear and high gear limit screws. These work together to ensure the mechanism is doing its job.
MTB Front Derailleur Adjustment
Though it may seem like a complicated task, learning how to adjust a derailleur on a mountain bike is rather easy, even for those who are new to mountain biking. The following steps can help you with this process.
Step 1. Prepare tools
The first step to an MTB derailleur adjustment is preparing the tools. You’ll need a few of them, so if you don’t already have these on hand, you can purchase them from a bike shop. They will be useful later on when you do further bike repairs or parts replacements, so don’t worry about the extra cost. It will save you money in the long run since doing adjustments like these yourself means you won’t be paying someone else to do it.
First, you’ll need a repair stand, which will hold the bike in place while you work. You’ll also need hex wrenches, a #2 Phillips head or straight blade screwdriver, a derailleur cable inner wire and housing, a caliper or metric ruler, cable end caps, housing end caps, rags, and a light lubricant. The RocRide Epix all-purpose bike chain lubricant is a good option since it is Trusted SourceRiding to Sustainability: Bike Sharing Takes Off Thousands of Americans are switching to pedal power for their transportation needs as large-scale bicycle sharing programs sprout up throughout the country, making cities greener and residents healthier. www.energy.gov , lightweight, and easy to apply.
Once you’ve gathered your tools and supplies, you can get started on your front derailleur adjustment.
Step 2. Adjust height
The first thing to check is the position of the derailleur cage. It won’t shift well if it is too high above the largest chainring. If it is positioned too low, it could scrape against the rings or lock up the chain during shifting.
To adjust the front derailleur height, you’ll need to use the positioning clamp that attaches it to the frame of your bike. When the clamp is tight, it adjusts the height and angle at once, so it’s best to tighten it only enough to hold the derailleur in place while still allowing it to be moved by hand.
When adjusting the derailleur, getting the proper height includes positioning the bottom of the cage close to the teeth of the largest sprocket without them actually touching to be sure it still clears. A distance of about 2 mm is recommended by manufacturers, so a good way to ensure you have the right distance is to stick a penny between the cage and the teeth. If the penny just fits, then you have the right height.
Of course, if the cage is somewhat low, this isn’t necessarily a bad thing. The lower the height of the cage, the easier is it to shift. Be sure to look at the outer derailleur plate to be sure it isn’t rubbing on the large chainring. If it all looks good, you can tighten the positioning clamp to secure the derailleur in place.
Step 3. Correct angle
The angle of the front derailleur cage should be as close to parallel to the chain as possible. Too far to one side and you won’t be able to shift properly. Clamp type derailleurs can have their rotation altered to fix this issue. There are a few easy steps to this process.
First, use the shifter to get the chain onto the outermost chainring and rear sprocket. Look down at the chain from above the ring. This is the best way to see how the chain is running through the derailleur and which way it needs to be moved to get it centered properly, preventing the chain from jumping to the outermost ring when you’re riding. If there is a large gap near the front or back of the cage, overshifting is possible.
If the cage needs to be rotated, note which way it needs to go. Then shift the chain to the inside chainring to release the tension of the inner wire. Some derailleur clamps leave markings on the bike frame that you can use to help get the proper height. You can also add pencil marks to note the necessary height of the cage. These will prevent altering the cage height as you adjust the angle.
Loosen the clamp bolt and then rotate the cage in the direction needed to ensure it is parallel to the chain. Once you have it positioned where you want it, tighten the bolt again. Then shift the chain to the outer chainring and look down at it again. If the angle isn’t correct, you can loosen the bolt and rotate it as needed. Otherwise, your bike is ready to go.
Step 4. Limit screws
The limit screws on a front derailleur prevent the cage from moving inward or outward on the bike frame. These are often marked with an L to stop it from moving towards the smallest chainring and an H to keep from moving toward the largest chainring.
If there are no markings on the limit screws of the front derailleur on your bike, you can test this to determine which is which. To do so, shift until the chain is on the smallest cog. Use the cable barrel adjuster to relax the tension of the cable.
Once this is done, put your hand on the body of the derailleur, which will allow you to feel any lateral movement as you continue the test. Using your screwdriver, turn one of the screws a full turn clockwise and then back to its initial position. If the derailleur moved during this test, this is the L screw, so you can mark it as such. If not, this is the H screw, though you can repeat this test on the other screw to be sure.
Step 5. Limiting low gear
Once you’ve determined which one is the L screw, you can adjust it as needed to ensure that the chain can shift to the smallest ring without going any further and falling off completely. To start, shift until the chain is on the innermost front chainring and rear sprocket. The inner wire tensions should be quite loose, though if not, find the barrel adjuster and turn it clockwise into the housing. If it can’t be turned any further, you can adjust the inner wire pinch bolt, loosen the inner wire, and then tighten the bolt again.
Check the gap between the inner cage plate and inner chain to be sure there is only a small gap of about 1 mm between them. Slowly pedal, monitoring the gap to see the tightest point during the rotation of the chainring, which is where you’ll set the clearance. Then adjust the L screw so there is a small gap between the cage and plate. Pedal the bike again, watching for any rubbing on the cage as the chainring rotates.
Test the shift by pulling on the inner wire to shift the chain to the next chainring rather than using the shifter. If the chain shifts quickly, the screw setting is good. If not, turn the L screw counter-clockwise only 1/8 of a turn and repeat your shifting test. Repeat this process until the shifting works quickly and smoothly. If the chain is shifting too far and falling off the ring, the gap is too large, so tighten the screw 1/8 of a turn and do the shift test again.
Step 6. Limiting high gear
Limiting high gear requires an H screw adjustment. To start, there needs to be enough tension to ensure proper shifting. There are two ways to test this. You can put some extra pressure on the lever or you can wrap your hand in a rag and use it to pull the exposed wire tight. Once the wire is taut, you can continue with the H screw adjustment.
To start, shift the chain onto the outermost front chainring and rear sprocket. Then find the H screw. Use your covered hand to pull the inner wire, adding tension to show that the derailleur is against the screw.
While maintaining the pressure on the inner wire, look for the gap between the chain and the cage’s outer plate. This gap should be quite small at about 1/16mm to 1mm. Continue to monitor this gap as you slowly pedal the bike. When you’ve found the tightest point in the rotation of the chainring, set the clearance at this point.
If the chain isn’t rubbing against the side of the cage, you will need to tighten the H screw until the gap reaches 1mm. If it is rubbing, the H screw will need to be loosened, though you should only move it 1/8 of a turn at a time while pulling on the inner wire and watching the gap for the proper clearance.
Once you think it is set right, test it by shifting from the second-largest chainring to the largest. Don’t use the shifter for this. Instead, use hand pressure on the inner wire. If the shift is slow, the H limit screw needs loosening. If the chain falls off the outside of the largest ring, the screw needs to be tightened. Once you’ve made the necessary adjustments, test the shift again.
Step 7. Index settings
Index shifters may also need adjustments, though you should only tackle this after you’ve completed all of the alterations we’ve discussed above. How to alter them depends on whether you have a three-chainring bike or a two-chainring bike. We’ll cover both here, starting with the three-chainring option.
First, shift so that the chain is on the middle front chainring and inner rear sprocket. Look at the gap between the inside of the cage plate and the chain. This gap should be as thin as you can get it without the cage rubbing on the chain. If it’s too wide, turn the barrel adjuster counter-clockwise to increase the tension on the inner wire, then check the gap again. If you’ve gone too far and the cage is touching the chain, turn the barrel adjuster the opposite way.
Test how the derailleur shifts onto all of the front chainrings, watching to see if it rubs on any of them. If it touches the largest ring, you may need to tighten the H limit screw and inner wire tension. If it is too slow when moving to the smallest ring, the L limit screw and inner tension wire may need to be loosened.
For a two-chainring bike, start with the chain on the front outer ring and rear cog. Look at the gap between the cage and the chain. If they aren’t touching, you don’t have to make any alterations but if the plate rubs the chain, you’ll need to adjust it. Turn the adjusting barrel counter-clockwise to increase the tension of the inner wire and check the gap again. Test the shift from one chainring to the other.
Step 8. Testing performance
When you’ve made all of the adjustments necessary on the front derailleur of your mountain bike, test it to make sure the chain shifts from one ring to another without falling off. There may be some rubbing, even in properly adjusted derailleurs, but as long as the chain moves smoothly and stays on, your bike is ready to ride.
The front derailleur on your mountain bike is rather important, whether you’re a kid riding their first one or a more experienced rider tackling those technical trails. If your bike doesn’t shift properly, it makes riding much more difficult in all types of situations.
Though you can take your bike to a bike shop to get this adjusted, with a few tools and a bit of your time, it is possible to learn how to adjust the front derailleur on a mountain bike yourself. This is much more convenient, getting you back on your bike in much less time with more of your hard-earned money in your pocket.