How to adjust the front bottom bracket on a bicycle

Chain line

“Chainline” is the distance from the symmetry plane of the frame to the chain / sprockets.

Front derailleur problems are often caused by an incorrect chain line, that is, the chain is too close or more often too far from the bike’s centerline. This is usually caused by the wrong carriage selection for the system.

Switch / Big Star Mismatch

To keep the front derailleur as low as possible, the curvature of the bezel must match the curvature of the large star.

If your largest sprocket is larger than the derailleur is rated for, the rear of the frame will brush against the teeth of the sprocket before the front of the frame is low enough to allow crisp shifting without the need for adjustment.

If the largest sprocket is smaller than the derailleur’s design, the shift will be fine, but fit will be necessary as the back of the frame is higher than it should be; so the chain crosses it far behind.

Sheldon recently started fitting the bezel to the big star. On a bike with a 50/38/28 system and a 46/36/26 derailleur. The curvature of the frame does not match the curvature of the star. Having removed in a couple of minutes a little metal from the switch frame (from the outer, inner planes and the bridge between them), he achieved the coincidence of the curvature of the asterisk and the frame. The derailleur could now be positioned very close to the sprocket for excellent chain control.

Wire ropes

Often shifting problems are not caused by improper operation / setting of the derailleur, but by too much friction in the cable that controls it. High friction usually causes the frame to return slowly to the smaller sprocket under the force of the derailleur spring.

How To Fix Chainring Wobble

Typically, these problems occur in the short length of the shirt leading from the pen to the switch. The front end of the shirt is exposed to dirt flying off the wheel and therefore rusts quickly, which seriously impairs shifting performance. This loop should be quite long so that there are no sharp bends. On most bikes, this loop is too short.

Another problem area is where the cable runs under the carriage. In addition to slow shifting, friction can cause spontaneous shifting under load.

When you cut the shirt, the plastic flattens a little. It is useful after that to clean and round off the end, for example, with an awl. The shirt forms a strong loop just in front of the rear derailleur. I recommend that you first bend a piece of shirt to an approximate shape and only then cut it off completely.

If you cut a straight shirt, all the longitudinal wires are the same length, so when you bend it, the end of the shirt becomes oblique, since the wires going inside the bend and outside it travel a different path. I (of course, Sheldon) believe that cutting off already folded shirts makes the joining of the end of the shirt smoother. Also, at the end of the shirts, there should be special tips that maintain the correct shape of the end of the shirt, and also prevent the shirt from delaminating into parts.

With modern jackets, cable lubrication is no longer required. Indeed, it often only makes things worse because of the stickiness of the lubricant itself. However, a little light oil on the part of the shirt going to the switch won’t hurt. it will prevent rust.

Cables and shirts vary greatly in quality. I would recommend buying only the best cables and shirts. However, it is still possible that the switch spring cannot exceed the friction in this loop.

“Fitting” the front derailleur

As the rear gear shifts, the direction from which the chain comes to the derailleur changes slightly. As a result, sometimes it becomes necessary to “adjust” the position of the derailleur when changing the reverse gear, even while remaining on the same front sprocket. “Fit” involves a slight movement of the frame by the shifter, but not enough to change gear, but only to eliminate friction against the sprocket.

On older shifters designed for frictional shifters, “fit” was simply implied, but modern discrete shifters can almost always be set so that this fit is not necessary. For perfect shifting, you need to use a derailleur designed for the specific sprocket size, and the sprockets must be completely flat. The lower the derailleur frame is set to the sprocket, the less adjustment is required.

If the system requires a “fit”, you have to do it. If the chain rubs against the switch frame, you will erase the frame so that you simply cannot expect any decent switching from it.

High gear limiter

Setting it up is extremely simple. you need to achieve a position in which the chain almost rubs against the outer part of the frame in top gear (large in front, small in back). This will reduce the need for adjustment when shifting reverse gears.

To adjust the high gear limiter, set the chain to the largest front chainring and the smallest rear chainring.

By turning the stop screw, the position of the switch frame is set so that the chain is as close as possible to the outer edge of the frame, but when the pedals are rotated, the chain does not touch it.

After that, while rotating the pedals, you need to try to shift gears in both directions step by step. If the chain does not come off badly from large stars to small ones, it is necessary to loosen the cable by rotating the cable tension adjusting drum clockwise. Otherwise, vice versa.

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If shifting is slow, make sure not to apply too much force to the pedals. When shifting, it is necessary to slightly reduce the pedal effort. If shifting is unreliable even with low effort, releasing the limiter a little can help. If you did, make sure that the frame cannot go too far and hit the connecting rod.

Sometimes a slight bending of the front edge of the frame outward can help. This can be done with an adjustable wrench, but fortunately is rarely required for modern switches, but has been used quite widely on older switches.

Tensioning the cables

Traditional front derailleurs have a “bottom link”. controlled by a cable going up from the carriage to the derailleur
Top-pull switches are cable-operated from above. This design is commonly used on mountain bikes to avoid running the cables under the bottom bracket, where they are instantly contaminated with dirt flying from the front wheel.
Some older designs use a jacket loop from a holder at the very bottom of the downtube. This design has not been used since the mid-70s. Fortunately, this is not difficult to get around. if you want to fit a modern derailleur to a frame where such a mount is intended. just ignore the holder by running the “bare” cable under the carriage. If you want to protect your paint, there are two easy ways to do it:
The easiest one is to use a piece of the “floating” shirt. a piece of 50-75 mm long under the carriage. In this case, none of its ends should rest against the holder. The friction of the cable will keep it in place.
A more elegant way is to install a modern plastic guide under the carriage. Usually these rails are fixed with a 5mm bolt, so you need to pull out the BB, drill the frame and cut 5mm threads. It is quite simple to do it.

Front derailleur (rocker)

After pokatushki, when the mud was kneaded, I began to touch the chain for the overthrow after the car wash. And wipe that switch. Looked

I think everything is cool! I’ll go and fix this fucking shit! He began to twist the bolts and pull the cable. Nix! It hurts anyway. After an hour of fussing, I realized that just the clamp holding the switch slightly shifted the crossover relative to the axis of the chain and it became not parallel! su
! I corrected the clamp, but I already knocked off the parameters! And that’s all! And he began to twist and twirl and set the chain with a swing! It took 2 hours, but the hike is all right.

Then I decided to paint everything as it is about the switch itself and how to set up the transfer. I started looking for information and found some interesting material. Reading 🙂
Many bikers consider the rear derailleur to be the most important and responsible element of the bike. But the front derailleur turns out to be quite an important component. Although they usually have to be used less often than the rear.

So the front derailleur is designed to move the chain from one front sprocket to the other. It is controlled by a device. a shifter, which is mounted on the handlebars or on the frame.

Cable holder (front)

In the case of front derailleurs, some newer models are designed so that there are two ways to attach the cable. If the cable approaches the outside of the bolt (farther from the parallelogram pivot), the frame moves less for a given cable movement. This provides easier operation and easier fine adjustment. If the cable fits from the side of the parallelogram hinges to the bolt, the frame moves further for this cable movement. This is often required for discrete gear shifting.

Eliminate bike squeaks

Bicycles tend to squeak. this is still not the easiest mechanism, and besides, it is subject to considerable stress. It’s not for me to tell you how clicking and squeaking can be made out of nowhere.

As practice shows, the most difficult thing is to localize the sound source. In fact, a squeak is just parts rubbing against each other that need to be reassembled and lubricated.

But the bike frame is such a thing that it can transmit sound in a completely different direction: it is not surprising when the rear hub is disassembled due to the clicking steering wheel.

I do not pretend to illuminate all the sore spots of the bike in terms of squeaks and other extraneous sounds, but I will try to give some guidance. Also, I do not consider the sounds made by the double suspension rear suspension due to the complexity of the design. So what squeaks in the bike?

How to clean the bottom bracket on a bicycle

Also looking for: cleaning the front end of the bike

This entry from the cycle “Prepare the bike for the season” and it will talk about how to remove the front wheel of a bicycle, disassemble the front carriage, clean, relubricate and reassemble.

This is not a tricky matter, but I think I can make a couple of useful remarks. We need:

  • Wrench 17
  • Round nose pliers or special thin wrench 14 (for holding the cone)
  • Cleaning rags
  • Solid oil, Litol, other grease (by grease I mean a thick grease)
  • For convenience, you can take a magnet, it will come in handy so as not to lose the balls
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We disengage the rim brake and, having wedged the axle, remove the wheel.

We twist the nut from the wheel axle (on my bike it is plastic, it rotates by hand). Remove the spring from the axle (if you have one) and take out the axle. In order not to lose anything, you can put the spring back on the axle and tighten the nut.

Next, with our hands or with a 17 wrench, we loosen the nut on one side of the carriage, put the wheel horizontally and twist the nut, and then the cone tightening the carriage. Horizontally, so as not to lose the balls.

Dismantling the front carriage. unwinding the axle

Further, I advise you to put a large piece of rags under the carriage so that the balls that accidentally fall out do not jump out and get lost. We partially pull out the axle to release the balls, the axle must remain inside the carriage, otherwise you risk dropping the balls inside and getting stuck for a long time, picking them out.

The inner part of the carriage on my wheel turned out to be not straight, but expanding inside under the edges, the balls that got inside stuck to the grease and I spent 20 minutes trying to get them out.

The main thing in this business is not to rush and not to lose the balls. You can use a magnet to pull the balls out of the carriage. When you collect the balls on one side, turn the wheel with the twisted side of the axle down and gently pull the axle down (you need to twist and gently pull it out again so as not to overwhelm the balls inside the carriage). I counted 9 balls on each side.

Outer axle of front carriage, nut and cone

We clean the old grease from the carriage with a rag

Cleaning the inside of the front carriage with a rag

We clean the balls themselves. This can be done easily and simply: wrap the balls in rags and roll them with your hand inside

We clean the rest of the details: axle, nuts, cones.

Cleaned inside of the front carriage

The assembly has begun. New grease needs to be applied. I had a grease for SHRUSS at hand, I do not attach much importance to the choice of greases, the main idea is that the grease should be viscous (Litol, Autol, Solidol), so that, firstly, it does not go down, and secondly it will help us charge the balls back to the carriage. We apply grease to the inside of the carriage in a circle. We carefully insert the balls into place, they get stuck in the grease and do not fall anywhere. Balls 9 pieces on each side.

adjust, front, bottom, bracket

Front Carriage Lubrication and Ball Placement

When we charged the balls on one side, we take a thick axle and, without fanaticism, apply lubricant to it (I think there is still a point in lubricating the axle body itself, this is a certain supply of lubricant that will be inside the carriage all the time and prevent moisture from entering the metal parts).
We insert the axle into the carriage from the side charged with balls (it is assumed that the cone and nut on one side of the axle are already present. we did not twist them). Holding the axle so that the cone squeezes the balls and they do not fall out, we turn the wheel over. On the reverse side, everything is simpler, the axis is inserted, which means the balls will not fall anywhere, we carefully insert the balls into the lubricated cavity.

We screw the cone and the lock nut onto the axle. We tighten by hand so that nothing spills out. Wipe off excess grease with a rag and proceed to adjust the tightening. If you untwisted both cones, then you need to adjust the position of the axle so that it sticks out equally on both sides of the wheel.

Next, you need to adjust the tightening. The main idea: you need to twist the cone so that the thick axis of the carriage rotates freely and at the same time does not dangle, and then lock the cones. This is how it is done. First, we tightly tighten (if the axle was untwisted on both sides) the locknut on one side of the axle (so that adjustment and tightening can be done only on one side), then we twist the cone from the back side by hand, grab the end of the axle and try to move it. The minimum axle backlash should be present if the axle is tightened so that there will be no backlash. then the balls while driving can jam and crumble (this often happened with the rear carriage of the Urals). When you turn the axle with your hand, it should spin effortlessly and smoothly, if you feel the axle rubbing against the balls and when twisting it vibrates, then the cone will be tightened. When the cone is adjusted, we try to lock it. Here we will be helped by a special flat key for 14, with which we will hold the cone, if there is no key, round-nose pliers will do. We hold the cone and tighten the lock nut. After that, we again check the tightness of the carriage axis. something could have moved.

Insert the wheel axle, put on the spring back and wrap the nut.

How To Fix A Creaking Bottom Bracket Or Cranks

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We put the wheel on the bike. You can twist and wiggle the wheel with your hand already on the bike itself, to once again make sure that there is no big play in the carriage and that the balls are not jammed.

Remember to connect the rim brake. Thanks for attention.

This entry was posted on 03/13/2015 at 11:15 am and is filed under Science and technology. You can follow the discussion of this post using the RSS 2.0 feed. Comments and notifications are now closed.

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Carriage creak

Probably most of the extraneous sounds are brought by the carriage, which is logical. it has the main load of transferring energy from the pedals to the wheels. First you need to make sure it’s not about the pedals. At a minimum, remove them, inspect for backlash, grease the threads with grease and screw them back.

The latter, by the way, should be done every six months, for obvious reasons. If it is possible to put other pedals for testing, put it on. The sound remains. we dig further. We take the tool for removing the carriage (depending on the type) and unscrew everything.

We wipe thoroughly (including the inside of the carriage assembly), inspect, lubricate and assemble back. We tighten not with all the foolishness, but rather strongly. The sound should be gone. If you have a cartridge carriage (for example, a “square” system), then the sound can be emitted by the carton itself with bearings. then this bulkhead of the unit will not help. change, since it costs a penny.

Also check if the stars of the system are screwed on well. Remove all bolts, lubricate with thread lock and screw back.

My bike

When you wash your mountain bike, don’t rub it right away. First, you need to pour water over the main parts of the bike (frame with rims) and let the mud soak in water. This will make it much easier to clean up a dirty bike. When washing a bike, you should try to rub as little as possible, and pour more water, not allowing dirt particles to scratch the paint. Use a brush and sponge to wash. The best brush choice is a toothbrush. It is advised to use two: the first to clean the dirt from the switches, brakes, bushings, carriages, and the second to clean the stars and chains. It is also convenient to use cotton swabs for the ears to clean the star.

To wash the ruble, some take it off and do not know how to put on the grips after washing back. You do not need to remove them to wash the steering wheel. Rubber grips can be washed with the same shampoo as the rest of the frame.

After shampooing and rinsing off the dirt with water, streaks remain on the bike, which spoil the appearance of the mountain bike. Now you need to wipe it thoroughly. If you apply car polish, you can give a special look to the bike.

How to wash your bike

Liquid detergents containing weak solvents. Such products wash well oily dirt. You can also use car shampoos, it washes away natural dirt perfectly. It is better to first wipe especially dirty places with a degreaser and then rinse with shampoo. At least WD-40 liquid or gasoline can be used. Not because these are very strong remedies, just for each stain it is sometimes necessary to use a specific liquid.

Pedals, bottom bracket, connecting rods

These are the most common sources of squeak. To hear it well, you need to drive off to a quiet place and stand up, press the pedals with force, while holding the brakes to stay in place. This eliminates squeaks in the seatpost and saddle. When driving at a leisurely pace, it is also possible to locate the squeak by listening to the rapid downshifting during each pedal rotation. In such a situation, noise appears most often.

If you have determined that the sound is heard precisely from the area of ​​the pedals, carriage and connecting rods, then you need to act like this. Start with the simplest thing. the pedals. Unscrew, clean the threads on both sides, lubricate each of them before installing. Drive again and check. If the creak persists, remove the connecting rods and carriage from the frame. It is better to clean them in some kind of solvent. Lubricate the crank shafts, cup threads and bottom bracket assembly. Before installing the parts in place, it is better to read the manufacturer’s instructions on how to do this (if it is, of course).

Nipples and Spokes

The phrase “wheel tension loss” implies a loosening of the spokes, which causes the wheel to bend under load. Nipples and knitting needles can move, and you can not feel it to the touch, there is a creak. The wheel should be broached by a specialist.

Switch rollers

The switch rollers make a sound when the pedal is depressed. The intervals between the sound are short and rhythmic. The casters must be removed one at a time and cleaned well before installation. Most rollers have a dry bushing, but will still perform better with a small amount of Teflon-based grease. If you have rollers with rolling bearings, then remove the seal and lubricate the bearing.