Faced with the risks of being targeted and stolen by risks, commuters are inclined to buy a used bicycle for the daily route between their house and the workplace. Frankly speaking, a second-hand bike is not only friendly to your budget but also a guarantee to free your bike from the threat of thieves. Here follows the point: how can you find a suitable second-bike bicycle? My suggestions are as follows.
1. Ask yourself the following questions first when you see the bike.question
Are you comfortable with the amount of rust you see?
Do all the components work as they should?
Are you satisfied with their answer to “Why are you selling it?”
Is the chain clean and oiled? Or gunky and dry?
Are the tires in good shape? Worn? Dry-rotted? (Not a dealbreaker—tires are easy to replace—but again, it gives you insight into the whole story of the bike.)
Can you find tires in that size? (Especially important with vintage bikes.)
Then you can go further to the following tips.
2. Look beyond the aesthetics.
What kind of riding will you be doing? Do you really need that full suspension mountain bike if you're just planning on cruising the beach? Sometimes, more features just make a bike more prone to mechanical failures or at the very least more demanding of upkeep. Keep it simple.
If you are using the bike for practical purposes, you have a good deal of leeway in what types of bikes will work. For a light person, a road racing bike might be strong enough, and will feel fast and fun. For a heavier person who rides hard, a mountain bike might be better. Cyclocross bikes are especially versatile. You can put slick, fast, tough road tires on ANY type of bike and make it reasonably functional.
But having a rack and fenders will increase the functionality a ton--you can install those easily if the frame and fork have eyelets. Even if not, it's still possible, just trickier.
The main differences between these types of bikes will be how they "feel" -- heavy or quick, twitchy or stable, upright or racy. Different handlebar types have a big effect on this. It's all a matter of preference.
The main thing you want to check is that it fits you correctly- everything else can be fixed or replaced (although the additional cost obviously comes into it) but a frame that is too small or too large will cause you untold misery.
There are a few guides online that will be way better at describing how to tell if the bike is a good fit for your size, but my suggestion if possible is take the bike for as long a ride as the seller is comfortable giving you and look out for any potential problems in terms of how spaced out you are on the bike. Take a look before you go of how a rider should sit and be critical of yourself.
Shift through the gears from lowest gear all the way to highest in quick succession. Ride up a hill and shift under pressure. If the chain falls off or the gears don't shift, you are looking at a hefty bill.
One quick and dirty metric for assessing fit: your seat height is approximately the length of your arm. Press your armpit into the saddle, and your middle fingertip should barely reach the center of the cranks (the axis that the pedals and cranks spin around). Besides, make sure you can stand over the bike without bashing your crotch on the top tube.
5. General quality.
The simplest way to judge the quality of a frame is by looking at the rear dropouts. Examine the way the tubes are joined to the dropouts, and the dropouts themselves. How good is the finishing there? Is the derailleur hanger part of the frame (good), or bolt-on (usually bad), or replaceable (usually higher-end aluminum)? How thick is the metal it's made out of? Does the frame have rack eyelets (very important if you're buying the bike as a vehicle, not a toy). When the frame tubes have just been crimped around really thin stamped dropouts, that's a sign of really poor frame quality.
Scratched or flaking paint isn't necessarily a bad sign. Even surface rust isn't a big deal. You might look at the top and down tubes right next to the head tube for slight buckling to see if the frame has been bent in a head-on crash. But the better way to tell if the frame has been structurally damaged in a crash is: a test ride with no hands. Make sure you're on smooth level pavement. See if the bike pulls to one side.
6. Online platform.
There are lots of sales platform on the internet, you can type the “second-hand bicycle trade” into the search bar and click your mouse. Then hundreds of results appear in front of you. The online trades usually get rid of the price difference of the middleman, which offers you a more reasonable price.
7. Mechanical condition.
Things like braking and shifting are unimportant when buying a used bike. They're cheap and easy to fix, so they're great signs for you the buyer: a good way to negotiate the price down. The major bearings are more important. If they're loose it's usually OK, they just need to be tightened. But if they feel inconsistent and "grinding" then they'll likely need to be replaced, which will cost some.
Headset: the bearing that the fork and handlebars turn on.
Bottom Bracket: the bearing that the cranks spin on.
Hubs: the bearings the wheels spin on.
Take a simple chain checker and check the chain. If the checker is over 0.75, you know you will have to change the whole transmission and that the bike was not well maintained and then don't buy, except if it's a bargain and you are more interested by the frame-set than the whole bike. Between 0.5 and 0.75: you will have to replace the chain. Not a big deal but it means that the whole transmission might not be in great shape too, and then it depends. Beneath 0.5: at this point, you know that the chain is either new or that the bike has not many been ridden far. Now, take the bike for a small test ride and shift gears quickly: if the shifting is grinding or not really smooth, it is possible that only the chain was changed but that the transmission isn't good, and then don’t buy.
If the shifting is smooth, it means that the bike was either properly serviced or have not seen many kilometers. In either case, it means that it might be a good opportunity: start to check everything else (see other comments).
Line them up and look for deviations in the spin (this is called 'trueness' of the wheel) Kneel down and look at the front of the bike from the side.bike, wheel
The blades of the front fork must be on the same line as the tube the fork goes through. It is useful to use a straight edge of some kind. Don't buy the bike if it isn't on the same line. The bike was in an accident. You can replace the front fork - plan for a $150 repair.
Grab the bike by the top tube and lift the front of the bike off the ground. The front should move freely without sticking in a specific spot, and should settle straight forward. When you test ride it, you should be able to remove your hands completely and the bike should go straight. If it doesn't, plan on replacing parts or repacking bearings. You can still buy the bike, but plan another $100 in repairs.
Lift the front of the bike and spin the wheel with your hand. Do the same with the back wheel. If either wheel bumps against the brakes or is stopped by the brakes you will need wheel work. Not an expensive repair, but indicates it has not been well maintained, was ridden over tough terrain, and essentially thrashed.
The rear derailleur.
It should be straight up and down, parallel to the seat tube, as viewed from behind. If it leans in towards the bottom, the bike has been laid down hard enough to bend the frame. Some mountain bikes have replaceable rear derailleur hangers so that this can be corrected easily. Otherwise you’re looking at a lot of bad shifting or an expensive frame repair.
The seat post.
Remove the seat post, turn the bike upside-down and shake. Any rust come out? Don't buy the bike.
Can't remove the post? Don't buy the bike. The seat post must go up and down and stay where you put it. What is the big deal about seat posts? Seized seat posts mean big trouble, and show the bike has been left in the rain and snow for years, dumped in a lake, or never touched by a legit mechanic. Don't buy the bike.
I've ordered these from least to most expensive fix: new brake pads or a wheel re-truing might be worth it, but if the cassette needs replacing or the frame is damaged you should probably walk away.
The break pads and the 'teeth' of the rear gears.
Very shallow 'V' indents is an indicator of the wear of the break pads for it represents the lifetime of the pad. Besides, you need to watch the wear on the teeth of the aka cassette.
The cracks in the frame.
The subtle crack can be potentially very dangerous. Listen for funny noises. If there is a noise when you crank it is almost certainly the bottom bracket that is worn out. It is replaceable though.
8. Assess the seller.
The seller should be open and upfront about the bike's condition and history. They don't necessarily need to be mechanically knowledgeable, Ask the seller how often was the bike used, how often it was serviced and what was done exactly. but it's a good sign if they can remember what maintenance has been done recently. Expect to leave some cash or something important to you (like a purse or backpack) as collateral while taking a test ride--especially with more expensive bikes.
Take the six tips as a reference when you are buying a second-hand bicycle, and I hope your many happy miles with a bike you choose.