Have you heard of Murphy’s Law of the Skipping Mountain Bike Chain? To paraphrase, it states that – even when your shifting is nice and smooth at home or at the trailhead – it doesn’t mean your chain won’t start skipping on your ride. And additionally, if your mountain bike does develop a skipping chain, it is guaranteed to be at the apex of the steepest ascent on your ride.
While a skipping mountain bike chain can be source of frustration, it’s not a mechanical disaster. Plus, there are multiple adjustments you can do, even on the side of the trail, that can alleviate or stop the skipping entirely.
Tools Needed to Fix a Skipping Mountain Bike Chain
Now, these are tools for doing leisurely repairs and maintenance in your driveway. Should you find yourself facing a skipping mountain bike chain on the trail, you will need to improvise. Fortunately, most mountain bike multi-tools include the things that are essential.
- Screwdriver to adjust derailleur
- Rag and brush to wipe away grease and grime
- Degreaser and chain lubricant
- Gloves to protect your hands
- Chain measurement tool like calipers or ruler to determine chain wear and stretch
- Potentially: Chain Breaker
DIY MTB Tip: For many years now I’ve been recommending the same bike tool kit. A PRO grade kit will cost you 3X more. Check out the Bikehand 37 pcs set, it’s got all the essentials. Shortcut link to Amazon for prices and reviews – Bikehand 37 pcs Bike Repair Tool Kit
What Causes a Mountain Bike Chain to Skip?
This is not a theoretical or “enlighten me for the fun of it” question. Because understanding the cause of the skipping is necessary for solving the problem, this will determine what repairs and adjustments you try. Here are some common causes of a skipping mountain bike chain.
- Worn Out Chain. Over time and miles bike chains stretch and get worn out. This means the teeth of the cogs won’t fit neatly inside the chain the way they did when everything was fresh and new. As you pedal, particularly under stress, the teeth will slip in and out of the chain, causing skipping.
- Dirt and Grime and/or Stiff chain. A chain is meant to bend and flex and be fairly pliable, in order to go through derailleur pulleys and around the gear rings. If it’s too dirty or stiff, it will stay rigid instead of following those curves. A thorough cleaning and lubricating, combined with manually manipulation of the chain to make it more flexible, should solve the problem.
- Cable Adjustment. When you shift between gears, you use some type of lever or shifter to move the front or rear derailleur in line with the chain ring you want. The shifters do this by tightening or loosening the derailleur cable, depending which direction you’re shifting. Over time, the cables stretch. This is so common, there are barrel adjusters on both shifter cables to allow you to easily tighten or loosen the cable without any tools.
- Bent Derailleur. Both front and rear derailleurs can get bent, However, it’s much more common for the rear derailleur to be bent – in a crash or even in minor mishap like falling over in a parking lot – because it’s thin, lightweight metal that extends out from the frame with no protection. If the derailleur is bent, it can’t guide (or hold) the chain in the correct place, causing the chain to skip.
- Derailleur Adjustment. The derailleur – when pulled or released into a new position by the shifter cable – lines up with the selected chain ring and guides the chain into the new gear. Though they look different, both front and rear derailleur serve the same purpose. However, if the derailleurs are not adjusted correctly, they won’t keep the chain lined up. Hence the mountain bike chain will skip as the chain slips in and out of position.
DIY MTB Tip: I know it might seem expensive, but a Bike Repair Stand is a lifesaver when working on a bike. I love mine, Heck I know two of them. Sold on Amazon, check prices and reviews with shortcut link -> Bikehand Bike Repair Stand I even made a video on YouTube – Bikehand Bike Repair Stand Review
Steps to Fix a Skipping Mountain Bike Chain
- Move the bike to a place that you can work on the drivetrain. Ideally, you should be able to turn the pedals as this will make your work faster and more accurate. If you have a bike repair stand, mount the bike in it. Or just flip the mountain bike over and balance it between the seat and handlebars upside down.
- Start by cleaning the chain, the cogs and the derailleurs. Use degreaser to wipe off accumulated gunk and a small brush to scrape off big pieces of rust and caked dirt. A toothbrush works fine if you don’t have a bike-repair specific brush. (Just remember not to put it back in the bathroom!)
- Check all parts of the drive train to try to determine the cause of the skipping chain.
Examine the chain to determine if it is worn or stretched. If the chain is stretched, you’ll want to replace it. But, be warned. If you’ve been riding a long time with a stretched chain, it may have caused wearing of the chain ring teeth. Thus, a new chain with a worn cassette or gear stack won’t solve the problem, and may even cause new problems.
- Use the barrel adjusters on your shifters to adjust the cable tension. If your shifting is slow and sluggish (takes several pedal revolutions to complete the shift), you probably need to tighten the cable. If your shifting is over-eager (spontaneously shifts without activating the shifter or shifts multiple gears at a time), try loosening the cable.
- Check to see if your derailleur is bent. Sometimes this can be difficult to judge. When checking the front derailleur, I like to shift to the largest ring. The ring should appear to be centered between the left and right side of the derailleur and the space on each side should be uniform at the front of the derailleur and at the rear. A front derailleur is more likely to get knocked out of alignment from the frame than to actually be “bent.” To adjust this, loosen the bolt that holds the front derailleur to the frame and adjust the angle of the derailleur until the chain and both sides of the derailleur are parallel. Don’t forget to tighten it back up!
For a rear derailleur, the derailleur, derailleur pulleys and selected chain ring should always “line up.” Imagine you could remove all the space and distance between these parts and make a straight line. If it’s not a straight line, something is probably wrong. The most common thing you’ll see is a bent derailleur hanger which looks like the derailleur pulleys are angled out from that straight line you want. Fortunately, derailleur hangers are cheap and easy to replace. If the derailleur itself is bent, we don’t recommend bending it back – it will never be as strong after multiple bends, and it is very challenging to bend it to the exact specifications you need. Though it’s more expensive, we do suggest that you replace a bent rear derailleur.
- A derailleur adjustment is challenging, but not complex. While anyone can learn to do it, I would suggest you have a moderate level of mechanical confidence and competence before trying it. The reason for my reluctance to encourage new would-be DIY bike mechanics to dive into derailleur adjustments is that it’s rarely the case that “even a substandard repair is better than no repair at all.”
- Unlike many elements of bike maintenance, derailleur problems can be made worse by unskilled adjustment attempts. So, build your experience doing simpler repairs and watching how-to videos, like this one, until you feel ready to give it a shot. And then proceed with caution.
DIY MTB Tip: Correct shifting technique is important. Have you wondered if you should pedal when shifting? Check out Should You Pedal When Shifting?
How to Prevent Your Mountain Bike Chain from Skipping
- Take care of your drivetrain. The best way to prevent your mountain bike chain from skipping is to perform regular cleaning and maintenance of your drivetrain. The drivetrain includes: chain, derailleurs, derailleur pulleys and shifter cables. Clean all elements of the drivetrain regularly, inspect them for wear and damage and keep them lubricated. This will go a long way in preventing bigger repairs. Additionally, keep the cable tension adequately tight. If you have to yank and force your shifters to get your gears to shift, there’s a good chance you’ll break your shifters, cables or even derailleur.
- Use proper shifting techniques. The chain is already under pressure when you’re climbing, and shifting gears adds to that pressure, stressing – and potentially breaking – elements of the drivetrain. So, shift before you begin climbing whenever possible. And, to lessen the strain while shifting, use soft pressure. Lessen the force you put in the pedals right as you shift, but don’t stop pedaling entirely.
- Replace your chain promptly when it’s stretched or damaged. While you may be tempted to continue riding as long as possible before replacing the chain, you aren’t saving yourself money or difficulty in the long run. In addition to having a skipping mountain bike chain, you’ll have a costlier repair later, potentially including new chain rings and derailleur pulleys.
When to Replace Your Mountain Bike Chain
Usually, you want to replace a chain once it gets to one percent (or more) elongation between links. You can measure stretch with a bike tool like calipers, or even a ruler. If measuring with a ruler, pick a rivet on the chain and line it up at the zero mark on the ruler. Then, count 24 more rivets. On a spanking-new, unstretched chain, this would put you at the 12-inch mark of your ruler. If it’s off by more than 1/16 of an inch, your chain should be replaced.
Inspecting the Rear Cassette and Chain Rings for Damage
Examine the chain rings for chips, damage and wear. The teeth should all look the same and each should be relatively symmetrical on the left and right side. Often, the middle rings wear out faster than the largest and smallest rings. After all, these are the gears you probably use most. So, compare the rings to each other. If the chain rings are worn – or if you replace the chain and the skipping continues – you will need to replace the chain rings or cassette as well.
Recommended Lubricants for Mountain Bike Chains
Because weather and trail conditions vary extensively, depending on where you ride, there’s no chain lubricant that’s perfect for all mountain bikes. Here are some of our favorites
- Finish Line 1-Step Cleaner and Lubricant. Kill two birds with one stone: degrease and clean your chain and lube it – with the same product!
- Finish Line Dry Bike Lubricant with Teflon. For dry, dusty, sandy riding a wax-like lubricant is better because it’s “self-cleaning.” So, when it accumulates dust and dirt it just falls off, instead of forming a tar-like gunk in your drivetrain.
- Finish Line WET Lubricant. For wet, rainy climates and extreme riding, choose a lube that’s water-resistant and will keep your chain running smoothly no matter how many creek crossings you do.
Bike Lube Tip: Keep all chemicals away from brake parts, most especially lubricants. Chemicals can degrade the rubber and other materials brake pads are made of. And, more urgently, you want grab, not lubrication, when it comes to stopping! Read this article -> Greases and Lubes for Bikes
Tips for Maintaining Your Mountain Bike
You may have noticed that the top tip for keeping your mountain bike chain from skipping is good, regular maintenance. What’s that saying…’an ounce of prevention is worth a pound of a cure’? It’s certainly true for your mountain bike!
Ultimately, you’ll save money on major repairs, enjoy your riding more and possibly even prevent dangerous accidents by staying on top of your mountain bike maintenance. Still, we all know how challenging it is to remember things like that, so use our helpful mountain bike maintenance schedule.
Get Out and Roll
When you get out on your mountain bike, you want to hear the tweets of the birds, the burbling of the creek, maybe your music or a conversation with a friend. But what you most decidedly don’t want to hear is the skipping of your mountain bike chain. While there may be no avoiding Murphy’s Law of the Skipping Mountain Bike Chain, we hope you’ve got enough helpful info and tips, you’ve got everything you need to deal with a skipping mountain bike chain, should it arise!
Looking for Some More Ways to Help Your Bike Last
- Regular maintenance will keep you pedaling for years. Read – DIY Mountain Bike Maintenance Schedule
- Everyone wants a new bike, find out when it’s time to buy with this article: Repair Old Bike or Buy New – Options
- DIY Mountain Bike Tune Up – A Complete guide to what to repair and how.
Professional writer Kat Jahnigen was 2 miles from the nearest village – and roughly 2,310 miles – from the nearest English-speaking town – when her bike tire burst. At that time, she was a college student on a bike trip across the desolate, rocky island of Crete. It suddenly occurred to her that it would’ve been good to learn some basic bike repairs before setting off on a solo bike trip.
Check out Kat’s website WriteHire at writehire.net.