If you find you have to pull hard on the brake lever to slow down, or it squeezes right into the handlebar, it's likely your brake cable needs adjusting.
There are two main points of adjustment for your cable-based disc brakes. One is at the caliper and the other is the barrel adjuster.
The caliper is the claw-looking device at the disk in the centre of your wheel. The barrel adjuster is the metal cuff on the brake cable at your brake lever.
Pull the brake lever to check the tightness of your brakes
The clearest giveaway that something is wrong with your brakes is if the brake lever is too tight or too loose.
If the lever touches the handlebars, the brake cable is too loose. If you can barely squeeze it at all, the cable is too tight. Ideally, the brake lever should squeeze 1 to 1.5 inches before becoming difficult.
Tighten or loosen the barrel adjuster accordingly
After diagnosing whether your brake cable is too tight or too loose, you can make minor adjustments using the barrel adjuster. Tighten or loosen the barrel adjuster by turning it clockwise or anti-clockwise. This will increase or decrease tension in the cable.
Once you've tightened or loosened the barrel adjuster accordingly, give the brake lever another squeeze to see if it's fixed the issue.
Top tip: Tightening or loosening the barrel adjuster is a quick and easy way to address braking issues if you're out on a ride. Even if it doesn't solve the problem, it might improve the situation long enough for you to get home safely and fix it properly.
Loosen the bolt on the brake caliper to readjust
If the brake lever is still too tight or loose after correcting the barrel adjuster, the cable may be too tight or loose on the brake caliper.
Take your Allen key and loosen the cable from the caliper by turning it anticlockwise, taking care not to entirely unbolt it as you'll find yourself having to reassemble the brake.
Pull or release the brake cable through the caliper
Once the caliper bolt is loose enough, it should spring back away from the wheel and cable. From here, you should pull the cable outward to tighten the brake, or allow the cable to retract inwards to loosen it.
The cable threads through a lever on the caliper that moves when you apply the brakes. When you tighten the cable, make sure the lever still has enough room to move and can't reach back so far as to hit the caliper. If it does, your braking will be obstructed and the pads won't reach the rotor. Skip to 1:11 in the below video for a demonstration of this.
Tighten the caliper bolt back up
When you've found the spot your brake pads sit comfortably over the rim and the cable is tight, screw the caliper bolt back up and give your brakes a squeeze. If they're still not quite right, it's worth revisiting the barrel adjuster to make final tweaks to loosen or tighten the brakes.
Stay safe while cycling
Knowing how to adjust your bike brakes will help you safeguard your bike in the long run. Please always make sure your brakes are working properly before riding, and always wear a helmet.
A warped rotor on disc brakes can cause loud noises while braking and squeaking while riding. Warping can happen from normal use, abuse, or simply by it getting too hot. A bent rotor is often the result of a direct impact when parking or storing the bike. If a rotor is badly bent, it's best to replace it.
It can be hard to determine if your rotor is repairable. If your rotor doesn't show any signs of improving after several minutes of working, then it's probably time to get a new rotor. When a rotor gets too worn it will not be possible to make it straight again. Use caution when working on rotors as their edges can be sharp.
Noise from the brake is often a sign that the rotor needs to be straightened
Before you start, check wheel alignment and play in the bearings. If the wheel isn't seating properly or the bearing allows the wheel to rock, then this is probably your issue, not the rotor.
Brake mounts on the frame may need to be adjusted / refaced. You will need a special tool for this, or high end bike shops will have it.
Loose rotor mounting bolts or a loose lockring.
Straightening Your Brake Rotor (Truing)
Straightening the rotor can often be done while keeping the wheel on the bike by watching the rotor move through the brake caliper.
Set the bike upside down on the ground in order to get the wheel spinning freely.
Watch for wobble at the caliper between pads. Look for the opening and closing of the gap. Find a section of the rotor that needs truing, and note which way it needs to be bent to correct the runout. Use a flashlight if you need more light.
Rotate this section of the rotor out of the caliper.
Use a rotor truing fork tool to flex the rotor in the appropriate direction in order to improve the bend. Always begin with a small amount of effort on the tool, and then apply more effort if no improvement is seen.
Spin the wheel and sight the rotor again. Repeat as necessary. When the rotor is not rubbing the pads as it spins, it is adequately straight.
You've read the instructions, pressed & held the power button, but your Jupiter Bike will not turn on. 3 quick things to check for this are:
1. Is the bike frame closed and latched. 2. Is the battery in the frame. 3. Does the battery have a charge.
If this doesn't solve the issue, please read on and try the follow more advanced troubleshooting.
1. Check if the LCD Cable Became Unplugged
Some Jupiter Bikes have an inline cable plug a few inches south of the LCD display. This 'quick connect' cable was designed to allow the user to easily replace the LCD display if it got damaged, unfortunately it's also the #1 reason that the bike will not start. To troubleshoot: Unwrap the cable coil holding the LCD cable, on the left side of the hanlebar. Look for a plug that is part of the cable that has become unplugged - and re-connect it.
2. Check the Battery Prongs
Your bike uses 4 or 5 metal prongs to pull power out of the battery. If one of those prongs get bent, the bike can not get power. To troubleshoot: Unlatch the bike frame, fold the frame in half and check the battery prongs. If one (or more) of them are not straight then take a pair of pliers and straighten the prong. Slowly close the frame, making sure the prong properly aligns with the battery terminal. The bike should easily close and latch with no excessive force. Re-fold the bike to make sure the prong is still straight. Close the bike again, and hold down the power for a few seconds to turn it on.
Derailleurs are fitted with limit screws that stop the derailleur from moving too far inward or too far outward. If you look closely as the derailleur moves, you can see the limit screws stopping the derailleur at each end of it's travel. Tightening the H-limit screw restricts the limit. The goal is to dial it in as close as possible to the inward cog.
Begin with a visual check of the derailleur hanger. If it's noticeably bent, your adjustments won't work. Shift the rear derailleur to the smallest cog. Even if you are already in the smallest cog, keep clicking your rear shifter to make sure there are no clicks left in the mechanism. This makes sure that the rear shifter is fully actuated outward.
H-Limit (High Limit) Screw Adjustment
The H-limit screw causes the derailleur to move. To find the correct setting, first make the H-limit screw adjustment too tight, then back it out until it sits directly below the smallest cog. Take your screwdriver and tighten the H-limit screw one half turn. Listen for excessive noise while pedaling. If there isn't excessive noise coming from the drivetrain, tighten the screw until you hear the chain rubbing on the next cog. Once you hear the excessive noise, begin to back out the H-limit screw one quarter turn at a time until the noise stops. If there are two settings that seem equally quiet, go with the tighter of the two settings. The H-limit is now set.
Now turn the barrel adjuster counter-clockwise a couple of turns. The idea is to bring it back to roughly where it was before. Don't worry if it isn't completely precise just yet. Do not adjust the L-limit screw yet, we'll adjust it after we have adjusted the derailleur indexing and cable tension.
The process of indexing is to line up the guide pulley with the cogs so that each incremental shift lines up with each cog. The barrel adjuster allows us to make these adjustments. A quick note is that there is a range of acceptable adjustment, meaning that there may be more than one barrel adjuster position that results in good shifting performance.
Start on the smallest cog. Pedaling at a normal riding speed, shift the shifter only one indexed click. We want one click to shift one, and only one gear. If the chain did not make it to the next gear, return the shift lever to the outermost click, and turn the barrel adjuster one full turn counter-clockwise. Try the shift again and repeat the process until it makes the shift. If you have un-threaded the barrel adjuster and it has come out, or has nearly come out, thread the barrel back in fully and then out one or two turns. Make sure that you are on the furthest outward shift position and the smallest cog, then remove the slack from the cable at the pinch bolt.
If you shift the shifter one click and the derailleur moves two sprockets, shift back to the first cog, turn the barrel adjuster clockwise one turn and try the shift again. Now that our chain is on the second sprocket after one click of the shifter, the shifting can be fine-tuned.
Turn the barrel adjuster until it is clearly out of the acceptable range of the first shift. You will hear noise when pedaling. Make sure that the source of the noise is coming from the chain beginning to strike the next inboard cog, then slowly turn the barrel adjuster clockwise until the noise goes away. While this is an adequate setting for this cog, you must now check each subsequent cog in the cassette one at a time. Shift and listen at each position for any excessive noise in the drivetrain. If you hear noise in any cog, turn the barrel adjuster clockwise one quarter turn. Test the shift to that cog again, and listen for any excessive noise. Repeat and continue to check until you find the barrel adjustment that allows good shifting in every rear cog, with the exception of the largest cog. The shift to the largest cog will be done later.
Now, shift outward in every cog, checking for excessive noise and good shifting performance. If any of these shifts are slow coming outward, that can be improved by another quarter turn clockwise at the barrel adjuster. Our indexing is now properly set and it's time to move the L-limit screw adjustment.
L-Limit (Low Limit) Screw Adjustment
Similar to the H screw setting, make the L screw too tight and back it out slightly until it is just right. This will provide the most protection from the derailleur shifting the chain beyond the largest cog and into the spokes. Shift the chain to the next to largest chainring in front. Shift to the second largest cog in the rear. Now, try shifting to the largest cog in order to determine where the L-limit screw is currently set. If the chain does not make the shift, than the L screw is already too tight, and that’s where we want it for now. If the chain shifts slowly to the largest cog, that is also a symptom of a too tight L screw. If there is excessive noise when the chain is on the largest cog, again, the L screw is too tight. If it makes an acceptable shift with no excessive noise, the L screw is not too tight. Shift the derailleur one click outward and tighten the L screw one turn clockwise and check the shift again. Repeat this process until there are symptoms of a too tight L screw. Once the too tight L screw is causing symptoms, turn the L screw out one quarter turn until and check the shift to the largest cog until the symptoms of excessive noise and slow shifting go away. The L-limit is now set.
As a check, put extra pressure on the shifter and watch at the rear derailleur. The cage should not move inward.
B-Screw (Body Angle Screw)
The spacing of the guide pulley to the cogs is controlled by the B screw, or body-angle screw.
This adjustment is check when the chain is on the smallest sprocket up front, and the largest cog in back. Your Jupiter bike should have a gap between 5 and 6 millimeters. Don’t get too hung up on this particular adjustment. If the bike is shifting well, the B screw is probably within acceptable adjustment range. To increase the gap, tighten the B screw. To decrease the gap, loosen the B screw. If you do make significant changes to the B screw, double check the indexing adjustment. Otherwise you are done, and your derailleur is properly adjusted.