Guide for buying a second-hand BMX
BMX bikes are used for a variety of disciplines including Street, Park, Vert, Dirt and Flatland riding. What they have in common however, is that in almost all instances they are often subject to some intense abuse. By their nature they are designed to be hard as nails, but they are not unbreakable and there are certainly things to look out for when picking up a second hand BMX.
It is vital to inspect every last inch of the frame for damage or weakness. Some BMX bikes are built from strong heavy metal and these are less likely to succumb to damage than the lighter ones, but you should still be vigilant when looking. Any serious harm to the frame of a BMX spells trouble and if its ability to withstand impact is impeded, then it’s more than likely unsafe to ride. The joint welds, top tube and forks are the most likely locations for flaws.
Most BMX bikes have brakes, so make sure you check the brake levers for responsiveness and stability, check the cables for conditioning and fraying, and the brake sets/pads for general condition and functionality. Get on the bike and test the front and rear brakes independently. If there is any excessive noise, shuddering or limited braking power, investigate further.
When cycling the bike it’s likely that you would notice any problem with the crankset if there were any. Things to look out for would be any movement of the bottom bracket, other than the rotation in the single dimension intended. Likewise, any side-to-side or up and down movement should be investigated thoroughly. Feel for resistance when pedalling and listen out for any unusual sounds like scraping or clicking. If there are odd sounds then it may be that the bearings have gone or that there is movement in the bottom bracket shell. It’s worth have a visual check of the crankset as well to sight any fracturing or bending of the crank arms (they will need replacing if there is) or any other damage to the bottom bracket or indeed pedals.
Depending on quality, the price of a new chain can be quite steep so you’re going to want to inspect the condition of the current one. A good chain shouldn’t have any rust on it, it should be well-fitting and each link should be able to pivot on the ones either side. If two links will not move independently of each other then they can very easily be replaced but beware, one locked link often means there will be others. Tip the bike upside down and give the chain a good few rotations. It should be smooth, quiet and easy to turn.
Turn the bike upside-down and check the condition of the rims. Look out for dents or factures in the metal and spin both wheels to see if they run true. Any problems with the rims will hinder performance and might mean you’ll need to fork out for a new pair straight away. Check each spoke individually for tightness or damage. Spokes can be tightened or replaced easily but loose spokes can be an indication of a misshaped wheel. When spinning the wheels, pay attention to how the bearings function. The wheels should spin almost silently and with very little resistance. Any noise or resistance to the wheel turning could be a problem with the bearings and may mean they need replacing.
The last parts to check on a used BMX bike are the handle bars and saddle/seat post. Like the frame, the handle bars are often subject to high pressures whilst riding, landing, bailing out etc. So push and pull them to make sure they’re stable and check that they haven’t been misshapen by seeing how symmetrical they are. The saddle and seat post are very easy to replace if they are damaged but never the less look out for tears or other damage to the saddle and rust or bends in the seat post.