Buying used bike - what to check?

dubcat

Hi

I am going to see a used bike tomorrow. This will be my first road bike and I have minimal bike experience in general. The first thing I wanted to be convinced of is that the bike is not stolen. I am happy it is not. Can you tell me what to check for on the bike? The more detail the better - remember I am a newbie.

It is a giant defy 1 2010. Alu frame, carbon forks, I think 105 gears. Very excited but keen not to make a mistake.

Hope someone can help
Dub

pilot_pete

Firstly, make sure it is the correct size for you. Take a look at the geometry and sizing recommendations on the Giant website as an initial guide. It doesn't matter what condition it's in if it is the wrong size and you will always regret buying it once the rose tinted spectacles are off...

Once you have ascertained that it will fit you, start with a general look over at the whole thing. Bit like a car really, does it look like it has had a hard life, or is it still very tidy and clean? Is there any corrosion on the frame or components? Start looking closer at the frame, looking for scratches, dings, worn paint, frame welds for tiny cracks etc. get the owner to hold the bike upright and get down on the floor behind it to check that the wheels are dead in line(obviously with him holding the bars straight). If they are not both vertical and you can see the front wheel sticking out one way or t'other then the frame is probably bent from a crash. Ask him if the bike has ever been crashed (sounds stupid, but some people are overly honest and will tell you about their big 'off'!)

I would then start at the top/ front and work down and back. Check the handlebars and stem for cosmetic damage such as torn bar tape, scraped levers and hoods (again a sign of it being dropped/ or crashed). Most bikes will have some grazing to the brake levers and that in itself is not a reason to dismiss it, but may lead to further questioning or negotiation on price if other items are found).

Check the headset for feel and play ( lift the wheel off the ground and turn bars left and right. Is it smooth or notchy, or grinding etc?) Put the wheel back down, pull the front brake and push the bars forward and back, is there any play in the headset bearings? These are all signs of looseness/ lack of maintenance or wear.

Check the brake cables, outers for signs of wear (fraying, corrosion, damage) and feel if the action is smooth when the brakes are applied. Are the inners adjusted correctly? Is there an end cap stopping the end from fraying, is there corrosion around the brake adjusters etc etc. all these things point to good or bad maintenance history. Is the brake clean and free moving ,look at the underside for stone damage/ cleanliness. Do the same with the rear.

Working down the frame, check bottle mounts/ cages for security and corrosion. Check the front derailleur for cleanliness and signs of damage/ wear. When you take the bike for a ride you can check both derailleurs for correct operation. If this is not correct you really need a bit more knowledge to decide if it's just incorrect adjustment or something more sinister.

Check the crank for security and wear. Kneeling beside the bike, grab the seat tube firmly with one hand and the crank arm with the other. Turn the pedal arm round so that it is inline with the seat tube and pull and push it in and out firmly to see if there is any playing the bottom bracket bearings. Again, if there is you probably need a bit more experience to decide cause/ how to resolve.

Check the chain wheel teeth for excessive wear (look on the Internet for pictures of what this looks like, be warned that the teeth are meant to have differing profiles and are not all identical!) at the 3 o'clock position on the crank pull a link in the chain to see how far off the chainring it comes, the more the chain is stretched the further off it comes. If you can get hold of a chain wear guide tool learn how to use it and check for excessive chain stretch. A steel rule can be used if you look up how to test for stretch.

Whilst on drivetrain, check the rear cassette for wear/ damage. When you ride the bike the rear shifting should be smooth and precise. If it jumps around it can be cassette/ chain wear.

Inspect the rear dérailleur for damage, which is very common - it is very exposed and prone to being hit in crashes. Whilst behind the bike checking wheel alignment, also look at the derailleur and see if the two jockey wheels are in vertical alignment. If not and if shifting is not perfect, it could be that the derailleur hangar is bent (easy fix).

Check the wheels and tyres for damage and wear. They should spin freely and smoothly and have no side to side 'wobble' as they spin. Look at the brake block on one side as the wheel spins to see if the rim gets closer or further away as it rotates. Again, could be an easy fix - a simple truing or something worse. Do a similar check for wheel bearing looseness as wit the crank - stand side on, grab the bike in one hand and the top of a wheel with the other and try to move the wheel away from and towards you. It will flex, but it should not have excessive 'looseness' in the movement, which is play in the bearings. Dependant on the bearing type this could be adjustable or require replacement bearings.

That's about all I can think of at the moment, apart from obviously accepting that a second hand bike is rarely going to be perfect, but the more minor things that you can find wrong with it gives you more negotiating power. If you find bigger stuff then you can just walk away...

PP

dubcat

PP fantastics and comprehensive reply! That's another one that I am going to file away for future reference! Thanks SOOOO much for taking the time to write that.

I did more research overnight and the bike has failed the initial test - that of size Specialized sizing guides put me at a large size. I thought the same would apply to Giant. However, in the land of Giant it seems I am an M/L. I was still keen to go and see the bike (rose tinted speccies) but after reading what you wrote I realised this would be a big mistake so I phoned the seller and told him I would not be coming to inspect the bike.

Shame really - a 21010/11 Giant Defy 1 (they are hard to find second hand it seems) for £400 seemed like a brilliant deal. Oh well - the search goes on.