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BRAKES

Caliper brake adjustment

Correct adjustment of the caliper brakes on your old school BMX is one of the easiest fine tuning procedures that is required (Unless you've got a handful of thumbs). Do it once do it right. All the components in the braking system should receive the proper maintenance from the lever to the rim.

Dry nylon pivot bushing Shimano DX. Black washers between lever & housing.

Dry nylon pivot bushing Dia Compe. White washers between lever & housing.

The Lever

The lever as the name suggests is just that a lever there is there is an arm that acts on the fulcrum this simple mechanism is used to multiply the force applied to the cable by the rider. The pivot is usually a steel pin with nylon bushes, this mechanism should not be oiled with regular type lubricants as it's exposed position means it is constantly exposed to dirt & crud. A dry lube should be used as this won't attract any dirt.

The Cable

The cable is made up of a outer housing (in your favorite colour) & an inner wire cable. There is a aluminium ferrule that holds the end of the cable against the lever body friction between the cable & ferrule will reduce the efficiency of the braking system. Inspect the cable for split ends or fraying also inspect the housing for areas that may be pinched or kinked if any of these conditions exist the cable should be replaced. To clean the cable remove the inner cable and wipe with solvent such as kerosene the housing can be flushed with solvent then blow dry with compressed air. Make sure there are no split ends & that the ferrule is installed correctly before inserting the cable into the housing. The cable can be run dry however this will reduce the life of the cable. If the cable is a bare wire type run a thin film of grease the length of the wire, if the inner cable has a friction reducing sheath a dry lubricant such as graphite powder can blown into the outer housing before assembly. This can be bought at any good bike store, Bunnings or order it from Amazon with the Shopping link at the top of the page the ones that come in the squeeze bottle are the easiest to use. Once the cable has been reassembled check there are no tight spots or binding.

The Caliper

There are two basic types of calipers side pull & center pull. When your side pull calipers are adjusted correctly they will give the best performance of any caliper brake. The side pull system consists of two actuating arms, adjustment barrel, cable anchor bolt/pivot bolt, return spring & brake pads. Like the lever the caliper uses nylon bushes, keep them clean & dry lube no oil. Adjust the cable/anchor bolt so the brakes do not move forward or chatter.

Rear of Shimano Tourney caliper showing proper cable instalation & return spring.

The rubber deposits on the rim should be cleaned off with steel wool.

The Rim

The rim is a critical part of the braking system if you have crome rims keep them true & your'e done. If you have anodised rims you have some extra maintenance to carry out. Alloy rims are all anodised coloured rims are anodised dipped in a dying solution then sealed, silver rims are anodised then sealed so you can see the natural colour of the the alloy. This anodisining layer is applied for aesthetic reasons on coloured rims, however most importantly the anodising layer provides a inert protective coating to the alloy which prevents corrosion. When this layer is worn off by the brake pads some of the original braking performance will be lost. To remedy this clean off the ingrained rubber deposits with some steel wool then wipe of with methylated spirits or wax & grease remover. The difference in braking effectiveness will be noticed immediately

Centering side pull caliper.

Three adjustments are required to allow the brakes to work correctly caliper centering,cable play & of course rim trueness. If the rims are true great if not this must be done first if you don't feel confident handling this take them to a shop. The first thing to be done is to center the caliper. You will need a hammer & punch. With the anchor bolt tightened tap the spring just off the anchor block on the opposite side of the pad you want to move away from the rim. After this is done squeeze the lever a few times to check that the adjustment is correct. It will take a few attempts to get it correct.

Adjusting cable play.

The cable play should now be adjusted, you want the pads just clear of the rim. To do this squeeze the pads against the rim & turn the adjusting barrel on the caliper to get more or less play when you are happy with the adjustment tighten the lock nut on the barrel. Once the caliper & wheel have been adjusted you can add a little toe in to the caliper. Tape up the brake pad mount to avoid scratching the caliper below the pad then grab the mount with a 6" shifter & bend slightly you will only need 1/2 -1mm toe in. Depending on how high up the brake pad is mounted you may need to remove the pad to carry out this procedure. This will reduce the chance of chatter & give the brakes a more progressive feel. Other modifications are adding Kool stop or Mathausers brake pads. I found the original Dia Compe pads that came with MX 1000 & MX 900 calipers to work extremely well. I think those pads where available on Dia Compe Bulldog caliper as well. I have a preference for Shimano DX levers however you should use what you feel most comfortable with.



BEARINGS A FRACTION TO MUCH FRICTION



If you where to look at the bikes at your next race meet & check out the bearings on all the bikes I suspect that more than half would need adjusting or replacement. I know you would not hesitate to search out and buy the trickest lightest parts for your ride yet most people overlook bearings. Reducing friction on your BMX bike is the easiest way to get a performance gain. The bearings are designed to reduce friction on the rotating parts of your bike. Ultimately we would like to reduce friction completely however it can never be entirely eliminated, you can reduce it to a relatively insignificant amount with proper adjustment and maintenance of your bearings. Reduce friction and you will go faster for longer... that's good yeah.

The bearings on your bike headset, axle & bottom bracket consist of three basic parts the cup the balls which can be free or caged & the cone, the cups are usually pressed in then the balls and finally the cone this is the adjustable part.

Typical bottom bracket & axle cups, bearings & cones

Your bearings should be checked on a regular basis depending on the amount of riding you do, the more dirt or mud riding you do the more regularly the bearings should be checked for adjustment and smoothness. The bearings on your BMX bike take a tremendous amount of abuse they are used in a low RPM and subjected to high shock loads so the best grease should be used when packing the bearings such as Castrol LM multipurpose lithium based or Castrol LMM with molybdenum disulphide base both are high pressure greases with excellent water resistance . Low quality grease will allow increased friction this can cause a condition where metal to metal contact known as friction welding causing heat build up will actually make the metal parts weld to together the result are tiny black pin holes in the cups, balls & races.

This is the result of inadequate lubrication an extreme case of friction welding.

The heat buildup occurs because the grease film cannot keep the surfaces of the metal parts from touching the temperature resulting from this contact can be as much as 520 degrees Celsius. A high quality grease will provide a film a few millionths of a millimeter thick between the moving parts and prevent friction welding. A word of warning do not mix greases if you change brand make sure you clean away all the old grease as a chemical reaction may occur that reduces their friction reducing attributes.

This cone nut has been damaged as a result of improper adjustment in this case being to loose.

If you inspect a new set of bearings they are shiny clean & perfectly smooth this allows them to rotate with a minimum amount of force. This is why it is so important to keep them clean and properly adjusted. If they are to loose the bearings will end up being pounded to pieces if they are to tight this will result in an increase of pressure & heat....Friction and this will annihilate them. When they are properly adjusted there should be no side play. Proper adjustment is something that comes from experience if the adjustment doesn't "feel" right readjust as required. You may have to loosen or tighten the cone an 1/8 of a turn to compensate for the inward movement of the cone when the lock nut is tightened.

A few things to remember are not to adjust the wheel bearings with the wheel on the bike take it off & do it properly (yeah I know the cone wrench fits between the frame & wheel). Take the chain off when adjusting the bottom bracket or you won't get the right "feel". You have probably heard of modding your wheel hubs by drilling a small hole in the center of the hub & installing a cover clip so that oil can be used instead of grease so as to reduce friction. In theory this will reduce friction however if the bearings run dry you run the risk of ruining your trick hubs, so if you are not fastidious & prepared to oil your hubs before every moto grease is the safest choice.

So keep them clean, adjusted & lubed for a fraction less friction with more satisfaction for your action.



SPROCKETS FREEWHEELS & GEAR RATIOS



Your gear ratios will have a big effect on how your bike accelerates & it's top speed, so what do you choose? A good baseline to begin with for BMX would be 2.75. To get this simply divide the front tooth count by the rear tooth count this will give you the ratio you have on your bike. Here are a few combos with a 2.75 ratio.

33 Front 12 Rear


36 Front 13 Rear


39 Front 14 Rear


43 Front 16 Rear


44 Front 16 Rear


45 Front 17 Rear


49 Front 18 Rear


The ratios above will give you a good baseline to work from. These ratios can be changed to give harder or softer gearing depending on personal preferences. One important variable to take into account will be crank length, with longer cranks a lower ratio (harder)can be used shorter cranks a higher ratio (softer).Longer cranks are usually used by taller riders they will give a higher leverage ratio and allow slightly harder gearing to be used. Shorter cranks are easier to spin however they require softer gearing & shorter legs. Wheel & tire size will have a minimal effect on gearing so they can be ignored.

You want to be spinning the gear out about three quarters along the main straight with the most important aspect being a good start... a bad start = a bad finish, if your starts are slow and you're not spinning out by three quarters on the first straight your gearing is to hard. If it's only a small change that is needed go one tooth smaller on the front cog, if you need a bigger change you can go up 1 tooth on the rear cog or 2 to 3 teeth down on the front cog. Changing 1 tooth on the rear is equivalent to changing 2 1/2 teeth on the front. If you start well and are spinning out at the first jump then you need to make the gearing lower with a larger front cog or a smaller rear. Check out BMX gearing calculator in the link on the right don't forget to bookmark this page.

The smaller the sprocket the higher the load on the sprockets & chain so larger sprockets will help minimize wear on your sprockets & chain, if ground clearance is not an issue go for the larger cogs. Nothing is written in stone in the world of BMX so be an innovator not an imitator and find out what suits you best.



CHAINS



The most important thing to know about chains is to keep your fingers away when they are spinning. Treat it with respect clean it, oil it, adjust it' and replace it if it's worn out. It ain't rocket science however it is a precision bit of kit.

A BMX chain consist of plates, pins 'bushes, & rollers with over 470 parts in total. With proper maintenance it will provide an excellent service life and fantastic efficiency requiring only one & a half percent of the power it transmits to overcome it's own friction. It will lose this ability instantly when it is full of crud or runs dry of lubricant.

Most OS BMX chains are 1/2x1/8. The 1/2 is the distance between the pins & the 1/8 is the width of the sprocket. As with all things mechanical the chain will eventually wear out, but it's life could be extended by 2 or 3 times through proper maintenance.

There are many ways to clean a chain. You can wipe it, soak it or brush it, with kerosene' wd-40 or some other solvent however this will not remove the crud trapped in the chain. The best way I have found is with a high pressure cleaner(when I was younger we used to ride down to the local servo and the owner would let us use his cleaner, then we would use the empty oil containers to oil our chains) remove the chain and give it a good blast with the pressure cleaner. You can do it on the bike but it's messy although you can clean the sprockets at the same time. Resist the temptation to spin the cranks at a billion RPM's it'll trash your freewheel.

When you have finished dry it off make sure all the crud is removed. If you are worried about water in the chain it can be soaked in some kerosene this will remove any residual moisture. The chain can then be wiped off with a rag & hung to dry. After drying oil both sides of the chain & let it hang so the oil can soak in. While the oil is soaking in clean the front and rear sprockets with a short bristled brush & solvent(you can cut down an old paint brush or use a toothbrush). When it's all clean reinstall the chain & go for a 5 k ride not in the dirt to allow the oil to work it's way into the chain. When you get home wipe off any excess oil. Now it's time to get RAD.

Bicycle chain lubricants although there are many fall into two main types petroleum based & synthetic. Once you choose a lubricant stick to it as the two types should not be mixed, if they are a chemical reaction will nullify the lubrication properties of both. Most sprays use some type of thinning agent that causes the oil to foam allowing the oil to work it's way into the chain, when they are sprayed on the thinner evaporates & the lubricant thickens causing it to cling to the chain.

The maintenance schedule you do on your chain will depend on where you ride. If you ride in a quagmire nightmare every day then this procedure should be done after every ride. It really depends on the type of riding you do. Oiling your chain before every ride can actually do more harm than good, dirt loves oil so moderation is in order. Also you do not want to oil a dirty chain it will just dissolve all the crud allowing it to work it's way into the chain.

Even with the best maintenance the chain will eventually "stretch" as the bushings, pins, & rollers wear. The chain should be replaced when it is 12mm longer than a new one. What type of chain to buy, as with most things the sky's the limit here however the most expensive chain wont work much better than a good quality item costing 20 25 dollars after a few rides in the dirt.

When installing a new chain the sprockets should be checked as worn sprockets will wear out a new chain in no time at all. Even a new chain will have a tight spot & this is where it should be adjusted leaving approx 1 centimeter of up & down play with the wheel tightened. When it has been adjusted spin the cranks if the chain binds on the tight spot readjust until the cranks spin freely. Use a screw driver or some other tool(not your fingers!)& lightly push against the side of the chain as you spin the cranks to check the chain will not derail.

Click the KMC Gold chain link in the column on the right & check out the trick KMC Lightweight chain.

I hope this info is helpfull, I will add more as the muse strikes me.