Guide for buying a second-hand mountain bike
Good mountain bikes these days are by no means cheap. However, a knock-on effect of their expense is that they are being built with much stronger and more durable materials, meaning there are literally thousands of great second-hand bikes out there for a fraction of the cost of a new one. You just need to know what to look for.
There are usually many elements to a second-hand mountain bike and each bike tends to vary in its make-up. Outlined here are the key points to look out for on the more common components.
Turn the bike upside-down and check the condition of the rims. Look out for dents or fractures 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.
There are a number of different types of brake used on modern bikes but they all do the same job, so the best way to test them is to get on the bike and use them to stop. Use both brakes individually in order to highlight any problems and look out for weak braking power, excessive noise, shuddering or having to use a lot of hand force to engage the brakes. Also check the brake cables for any fraying or splitting…any damage to the cables can spell trouble for braking power, especially for hydraulic brake reservoirs, so give them a good inspection. To be honest, most problems can be corrected by making small adjustments but be prepared to pay for new cables, pads, levers and even brake-sets if there is significant wear/damage
Arguably the most important part of the bike to inspect. Almost every frame is different but there are common elements that should be checked. First examine the welds in the frame. Are the any cracks or clear weak spots? How about the top tube and down tube, are they in good condition? Don’t be afraid to apply a reasonable amount of force to each part of the frame, it should be able to hold up to a lot and if you see any weakness or excessive movement then the frame is severely compromised. In some instances the frame can be re-wielded or strengthened but it’s unlikely to be worth your time and there are plenty more bikes in the sea. The general condition of the frame should be good. If there are lots of dents or nicks in the frame it may suggest the bike’s had a lot of use or has been badly treated.
Check the condition of the saddle covering and have a look underneath at the fixings also. Try adjusting the seat up and down. This should be easy to do and the seat post shouldn’t snag at any point. If it does then the saddle post or seat tube of the bike could be misshaped.
As with other elements of a mountain bike, suspension can come in many forms, so again the best way to test it, is to use it. To test the front forks, repeatedly apply pressure downwards on the handle bars and see how much travel there is in the forks. Look out for restricted movement or too much movement – both of which can suggest damage. Remember however than many types of suspension allow for adjustments to the travel in order to give a firmer or softer ride, so test at both extremes that the forks offer.
Some forms of suspension use oil in the forks. If this is the case then clean both forks, apply some downward pressure on the handle bars and see if there is any oil on the forks when the suspensions expands back out again. If there is oil then there’s most likely a problem with the fork seals and they’ll need replacing.
To check the rear suspension, place pressure downwards on the saddle. Like with the front forks, there should not be too little or too much movement. However, advances in rear suspension have allowed adjustment to the travel here as well, so take this into account.
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.
The most common type of gears on modern mountain bikes comprises of a front and rear derailleur, a set of rear sprockets (aka cassette) and a set of front chain rings.
Take a good look at the condition of the sprockets and chain rings first. They can sometimes become damaged and the teeth can bend or pick up nicks, both of which will need repairing. Check if they are secure by trying to move them both away from and towards the bike. Any wobble or sliding of the sprockets or chain rings will need looking at.
The front derailleur should guide the chain onto the chain rings smoothly. Check that it hasn’t been bent out of place or picked up any serious damage. Impact marks on derailleurs are a key giveaway of bike abuse. The rear derailleur should do a similar job, guiding the chain on the rear sprockets with ease and smoothness. Push the bottom of the derailleur forwards to give slack to the chain and let it move back into its resting position. This line of travel should again be smooth and require little effort to achieve it. Check the cables that run to both derailleurs for fraying or other damage and also check the gear-changing apparatus on the handlebars for ease of use and possible damage.
Whilst a visual inspection of the gearing system is important, the best way to actually get an idea of the condition of the gears is to use them. Ride the bike around a bit and go through every gear ratio possibility there is. The changing between gears should happen quickly, smoothly and without too much noise. When cycling in each gear the action should be the same and there should be no clunking or clicking coming from the derailleurs. Tuning can often fix most problems with gearing but the person selling the bike should have sorted this themselves first, and if they haven’t then it can sometimes suggest there might be more terminal damage that couldn’t be fixed without new parts
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.
Handlebars and Stem
There is often a lot of force put through the handlebars and stem of the bike, especially during a heavy landing. For this reason they are usually well reinforced and built from strong materials. However, bending, splitting and even serious fracturing of the metal is not uncommon and should be looked for. Stickers can sometimes hide damage and you should ask for them to be removed before you buy. Also look out for repair work on the bars or stem (as indeed you should for the whole frame) and be cautious of anything that looks like it has been re-welded or amateurishly repaired.
To reiterate what has been said previously, the best way to test a used mountain bike is to give it a good ride. If everything on the bike is in good condition then the seller shouldn’t mind you testing it, and if there are any problems, they will soon become apparent.