Monday, June 12, 2006

Assembling a Bike

Assembling a new bike out of the box involves more than just slapping on the parts that aren't already in place.

To do it right, you have to take it apart some more before you put it all the way together.

At this point, shop owners all over the world are giving thanks that I don't work for them. Or maybe not. It depends on their long-term view.

A fast mechanic can slap a bike together for the floor in less than an hour, maybe much less. It will probably work for a test ride and make it to the free tuneup a week or a month later.

If you figure the free tuneup only needs to be worth as much as the customer is paying for it, you can breeze through that in short order as well. Make sure the crank arms aren't going to fall off, the brakes don't squeak and the gears shift smoothly.

The mountain bike boom made me take a more critical look at assembly and tuneup procedures. In our area, people were really beating up their bikes. Anything less than battle-ready equipment would come back in embarrassing pieces. It was like a laboratory experiment in rapid aging of a bike.

A thorough assembly will help make the free tuneup a breeze, because properly assembled bikes won't come apart as fast as quickly assembled bikes. A carefully assembled bike is less likely to embarrass the shop. This is just self defense, people.

Most of our customers are regulars. Over time we collect a lot of history on their bikes. If we do good work from the outset, our job tends to get easier and the customers trust our opinion more, because their bike works better after it has been in our hands. Sure, we make mistakes, being mere humans. But overall a meticulous workshop costs less than a shoddy one.

When I assemble a bike I start by pulling the rear wheel off, removing the cassette or freewheel and adjusting the rear axle cones. Most factory-assembled bikes come with over-tightened hubs. Often the locknuts aren't properly locked, so this tight hub could very well turn rapidly into a loose one after hard riding. Then the bearings will get pounded into the cones, fracturing them. Or the hub might stay tight, grinding the bearings uniformly into the cones, digging a trench.

Grease and reinstall the cassette lockring. With a freewheel, grease the freewheel threads on the hub before reinstalling the freewheel itself.

Repeat the adjustment process with the front hub.

On both wheels, grip and squeeze sets of spokes to produce a crackling noise as the spokes de-stress. We nicknamed this procedure "cringling" because of the noise it makes. Do this until the spokes are quiet. Then true the wheels.

Inflate the tires before adjusting the brakes. Rims will flare very slightly when tires are holding full pressure. It's not too critical. I often forget to inflate the tires and seldom have to readjust brakes on a new wheel. Older rims, sidewalls eroded by brake pad wear, may bulge considerably, but new rims usually don't react too much. It's just a nice touch.

Set cantilever or linear-pull brake pads near the outer edge of the rim. As the pads wear, they will strike the rim lower and lower. If they're too low to start, they'll drop below the inner edge and develop a lip.

Road-type caliper brakes actually pinch inward and upward. The narrower the rim, the more noticeable the upward movement will be. You don't have to set the pads radically low, but avoid setting them too high.

Grease the threads on the top cap bolt of a threadless headset. I've seen these rust into the star nut threads. I've also seen alloy headset spacers corrode onto steel steerer tubes on mountain bikes that have been taken on many jungle cruises. If you are taking your bike apart frequently, this corrosion has little chance to develop. If you happen to leave an assembly together undisturbed for too long, you may get a rude surprise.

Remove water bottle bolts and other accessory bolts and grease the threads on them. Retighten them securely.

Grease crank bolts. You'd be surprised how often they come through dry. They will not tighten smootly or torque properly without lube.

A touch of grease makes a big difference over the lifetime of the bike. I will grease threaded adjusters on brake levers and derailleurs, cable anchor bolts, brake shoe posts, pretty much anything with threads, if I have the time. Many of these have a token amount of grease from the factory, but it's often that brown, semi-dry earwax, if anything.

If you decide you are going to be this thorough, you can develop your own streamlined procedures to knock off each step, rather than waste time trying to talk yourself out of it.

On high-end bikes, especially special orders, I will grease chainring bolts. Those are always dry.

All this extra care is in addition to the normal assembly activities, greasing pedal threads, seatposts and quill-type handlebar stems.

Time spent on assembly is time you won't have to spend getting a bike ready for a test ride or to be handed to a happy customer so they can take it right home. Thorough assemblies mean you don't have to tie up shop time on free tuneups when you could be doing paying repairs. Thorough assemblies mean you can slap on accessories like bottle cages or racks faster. Sales go more smoothly. Profits go up while customer service improves.

We all get tired and overworked. We fall short. But high standards at least give us something to shoot for.


Brian said...

Why do you gease instead of anti-seize?

Nathan said...

"Or the hub might stay tight, grinding the bearings uniformly into the cones, digging a trench."

Hey! I've got a trench forming in one (or both, I only checked one side) of my rear cones! It's not all the way around, though, just about 1/3 of the cone has this trench. Is that still a too-tight symptom?