Lubrication

In this extract from his book, Bicycle Design, MIKE BURROWS looks at how we lubricate our bikes

Keeping the main bearing elements of the pedal cycle lubricated should not be much of a problem.They are, of course, all rolling element bearings and usually of more than adequate size. For example, the most popular ball race for top end hubs is the 12mm bore x 28mm overall diameter 6001 bearing. This has a dynamic load carrying capacity of 500 kg at a maximum of 28,000 rpm - figures that the average cyclist is unlikely to exceed!

Too much 'Environment'

So if you were to ask a bearing manufacturer about lubricating a bearing operating at one tenth of its load capacity and one sixtieth of its speed limit, he would tell you merely to put a small dab of grease on once in a while. If however you told him the bearings were on a bicycle, he would probably deny all responsibility for his products, due to the special circumstances.

This is because the problems that cycle bearings face are not so much a lack of lubrication as an excess of ‘environment'. Water causes the polished surfaces to corrode. And dirt causes abrasive wear and fatigue of the hardened steel surface, as it creates small points of ultra high pressure.

Possible Solutions

Seals are available to solve these problems, but fitting them would add to the cost and weight, and would increase the bearing drag. So the people who would benefit from them won't pay for them - or are not given the choice. And the racing cyclists who have the money don't want the extra weight or drag.

There are some excellent replacement hubs and bottom brackets available that allow you to pump new grease in at the centre which pushes out the old grease and dirt through the seal, where it can be wiped off. There is an element of overkill in this approach, but it will guarantee a long bearing life. Bearing drag will of course be higher with all that grease being churned around. In fact, for normal bearing use it would be very bad practice. But that is because of the much higher speeds - you are unlikely to overheat the grease at 400 rpm.

For those worried about the excess drag of grease you could use the same idea but use a small amount of thickish (engine) oil instead. This will soon find its way to the bearings, unlike grease that does not flow at room temperature. It will, of course, also flow out through the seal eventually, taking some dirt with it and making your bike look a bit messy. Worse, if the oil gets on wheel rims it will adversely affect braking, and if it gets on tyres it will do the rubber no favours. So you will need to keep a cloth handy to wipe the bike down occasionally.

The Chain Problem

But all these problems are as nothing in comparison to the cyclist's greatest tribological challenge, the chain - famous for being ‘rusty-dirty', ‘rusty and dirty', ‘oily and dirty', etc. And these problems of lubrication of an otherwise excellent device have caused more ‘designers' to ‘improve' the cycle by giving it a toothed belt, shaft drive or whatever. The real solution to the problem is of course an oil-bath chaincase. But Sunbeams have been out of production for 30 years and my updated version will not be available until 1999. In the meantime you have two choices.

The Proper Method

To do it properly you need to:

  • remove the chain,
  • clean it in soluble degreaser,
  • heat it with a hot air gun till too hot to touch,
  • drop it into a container of thick oil (I use SAE 150) and leave for a few minutes,
  • hang it for an hour or so to drain off surplus oil,
  • lay it on a soft tissue to remove any remaining surface oil
  • and finally, refit it.

Then repeat as necessary!

The Quick Spray Approach

The above method works very well but is obviously a lot of effort. The popular alternative of using an aerosol of either wet or ‘dry' lubricant is a poor substitute. This is because any oil added from the outside to a dirty chain will take some of the dirt with it into the bearings, increasing chain wear and in turn chain ring and sprocket wear.

The Clip-on Chain Cleaner

Between the ‘proper' method and the quick spray approach is what may at first sight seems to be a sensible compromise. It is possible only for derailleur-geared cycles and involves using a proprietary chain cleaner device. This clips around the chain in situ and feeds it through various brushes and a small bath of degreaser. Rotating the cranks backwards about 30 times ensures that the chain is fairly well cleaned. And much of the muck and old lubricant is caught in the cleaner for safe disposal. However, almost inevitably some of the dirty degreaser drips off the chain or is sprayed about by the sprockets. This makes the process fairly messy.

But here's the real rub. Having worked degreaser into the inner recesses of the chain you then have to relubricate it, either with an oil can or an aerosol. Hence deep within the links you are mixing lubricant with degreaser - unless you dry the chain as in the ‘proper' method! Use of a chain cleaner can therefore merely be a compromise solution - a not particularly quick but nonetheless fairly dirty way of achieving a second-rate result. Not surprisingly, many chain cleaners end up being used only a few times before enthusiasm wanes.

Cables

That other bane of the cyclist's life, the brake and gear cables, have thankfully become much less of a problem thanks to nylon linings and PTFE coatings. However, many cables will still rust if left unattended for long periods. The only real problem though is the last bend of the rear mech cable. The bends cause the friction and as this one is close to the muck, a lot of it gets sprayed onto the open cable above and works its way inside the cable sheath.

One solution is to run full outer cable up to the top tube. Or you could try the new caterpillar-like gizmo that SRAM have put on the market. This could be pre-packed with grease, which hopefully will work its way into the outer cable faster than the dirt from the lower end.

Velodrome Minimalism

If the bike is only to be used on the rather less environmentally-challenging velodrome, you could strip down all the bearings, clean out the grease and even leave the seals off. Then apart from an annual strip-down, just apply a drop of regular cycle oil once in a while. But don't expect it to actually feel any faster.

[ Read more on lube in Mick Allan's Blog post 'The Method' ]