Sweat can destroy your bike.

The flow of air past your body tends to dry most of your sweat before it can drip onto your bike, but some of the sweat (and the salts suspended in it) will inevitably come into contact with the bicycle and its components. This is of particular importance when the bike is on a stationary trainer, as the wind is no longer there to evaporate the sweat.

Here we see the clamping area of an aluminum handlebar that has been eaten completely through by salt deposits and moisture from sweat. See the two dark spots? Those are where the entire wall of the handlebar has been consumed by corrosion. There is also a great deal of visible salt left over after the moisture has evaporated. This is a particularly dangerous example, as there was very little material preventing the handlebar from simply snapping off below this spot. The forces generated by a rider sprinting in the drop position of the handlebar could quite possibly have broken this handlebar off, likely resulting in a serious crash.

Solutions to this problem include regular wiping down of the bike, and the use of a sweat cover when it's on the trainer. Regular replacement of the handlebar tape can help cut down the contact of salt with the handlebar as well. Some people just have naturally more corrosive sweat than others, so be sure to stay on top of it if you are one of the people who sweat battery acid.

Headset Shenanigans

I didn't think of taking a picture of this at the time, but an experience I had in the shop today was certainly blogworthy.

A fellow came in with some major stickiness in the Campagnolo "Hiddenset" headset on his Bianchi road bike, which he bought used. After removing the fork to take a look, I found that the top bearings were completely non functioning. Removing the parts from the headset cup, I discovered that there was a grand total of ZERO ball bearings inside. The bearing race was just sitting in the headset cup, as well as an unrelated fork crown race thrown in to take up enough space to fit the top bearing cover back on and make the bike look normal. This was an extremely dangerous condition. Installing the appropriate ball bearings and steerer tube compression ring, as well as removing the extraneous crown race got him back on the road. He will still need to get to a Bianchi dealer to have the headset replaced, as it has been subjected to some pitting.

Did you get your bike used? Have it checked out by a professional mechanic!

Galvanic Corrosion

Aluminum is generally considered a "corrosion-proof" material for building bicycle frames, and it certainly resists corrosion in the sense that it does not rust like steel does. What is common with aluminum frames, however, is the process of galvanic corrosion. The problem with aluminum frames is that the frame is often in contact with a dissimilar metal, such as steel or even different aluminum alloys. The two metals have two different electric potentials, with the possibility of a tiny electrical current flowing between them. The presence of water and an electrolyte (both of which are found in the rider's sweat) facilitates this current flow, and ions begin to flow between the metals. The problem lies in the fact that the metal which loses ions begins to corrode much more quickly that it otherwise would.

Below are two examples of galvanic corrosion occuring on the same frame. The first photo shows a steel ferrule that has been in contact with the aluminum frame for a very long period of time, and has also been exposed to a lot of sweat. The steel ferrule has corroded and gotten stuck in the frame. Luckily, this is an example where the frame has not been affected, only the ferrule.















The second photo shows an area of the frame that has been in contact with another aluminum part, and also has been exposed to the rider's sweat for some time. In this example, the frame is the part that has been corroded by the process. You can see that the edge of the cable exit hole in the frame has begun to be eaten away. The other part involved is not pictured, but has not been affected.

















The solution to the problem of galvanic corrosion lies partly in proper preparation of the parts before assembly, and partly in rider maintenance. A layer of grease between to dissimilar metals will act as an insulator, and is very effective at preventing the problem. However, it is not a substitute for regular cleaning of the bike. This is especially true in the off season when the bike is on a trainer. Because the rider does not have wind current to aid in evaporation of sweat, more of it ends up in contact with the bike. This makes it especially important to try to keep the bike covered when riding on a trainer (we can get you the Safe-T-Net from Minoura or other similar models) and one must remember to clean the bike after workouts. Replacement of cables and housing once a year will also ensure that the insulating layer of grease between parts is there to insulate the two parts.

Rim Wear

The friction forces involved in slowing your bike down are enormous. The effect this can have on your rim’s braking surface is quite impressive, as the wear can be accelerated by grit picked up on the road and small aluminum shards that are shed from the rim and embedded into your brake pads. This can make your pads quite abrasive, resulting in serious weakening of your rims. The example above is of a front rim that has been worn down by braking, which has caused a concave shape in the braking surface. The rim wall is much thinner at the center and can eventually be worn completely through and make dangerous rim failure possible. In addition, this rim has some dents from various impacts over its lifespan, making it an ideal candidate for a wheel rebuild.

The wheel’s hub can typically be reused, although it may need an overhaul (like this one does). Parts replaced are the rim, spokes and nipples. A typical wheel rebuild will cost about $170 total, and hub overhauls will vary in cost with different models. Unless otherwise specified, we use stainless steel double butted spokes from Wheelsmith, DT Swiss brass nipples and a quality rim from a manufacturer like Velocity.

If you have any concerns about the condition of your rims, please give us a call or stop by the shop for an inspection.