My guide for buying a cycle is based on 8 years previous experience as a cycle mechanic primarily at halfords but also with independant bike shops too. And no, im not one of these halfords employees that cant service a bike! I have little experience of extreme riding so this guide will be generally for people in the market for a bike valued up to about £300 (retail cost) who are primarily looking to buy on ebay.
First of all work out a budget:
Buy the best you can afford. remember as with most things in life you pay for what you get. and if it looks like its too good to be true it probably is!
Work out what your main style of riding will be:
Initially designed for treenagers-adults to use to do tricks on back in the 80's, the small compact frames are designed for maximum flexibility, whilst still retaining control. this is a fairly complex area to describe, so i wont go into much detail but BMXs run on 20" wheels, are suitable for tall kids from the age of 8 to adulthood, and are single speed only. the brakes arent exactly state of the art, as they were designed to be used on ramps. highly inefficient for any form of distance riding, there sit back knees up riding position is currently the coolest you can get. also a good quality £200 bmx is also an ideal entry level dirt riding bike that wont fall to bits the first time you do a heavy jump.
Road Bikes: (current halfords bike examples = Carrera Gryphon/Valour/Vanquish)
The preferred type of cycle for road use is a bike with lightweight frame, no suspension, smallish rear cogs and large front cogs, large diameter wheels and narrow tyres with shallow or no tread pattern. these types of bikes are traditionally referred to as "racers" with rams horn handle bars, however there are several brands (for instance carrera gryphon) which offer a traditional racing bike setup, but with straigh handle bars. these bikes offer extremely efficient riding with minimal physical effort. However it is not recommended they are used on any surfaces rougher or bumpier than a pavement as you can easily damage the lightweight wheels which can easily buckle under stress, and snap road bike frames & forks make from aluminium, as aluminium "work hardens" which means it becomes hard and brittle and snaps if it gets battered about too much.
Hybrid Bikes: (current halfords bike examples = Carrera Subway/Apollo CX.10/Helium Crosstrack)
These are also referred to as Town and Country Cycles with largish marginally chunkier open "racer" style frames, but with normally with straight handle bars and slightly wider tyres with a fine - medium tread pattern. they also use either 26" mountain bike wheels, or 700c/27"/28" wheels. Frames are often made out of aluminium again for lightness, but may also feature suspension forks and/or a suspension seat post. these suspension parts soften and absorb the hard "knocks" the frame would otherwise experience when shown a towpath or park, however there off road ability is limited to light work.
These bikes are what are typically described as "mountain bikes". frames are of either steel, chromoly, or aluminium. They will either be completely rigid (no suspension), have front suspension, or have full suspension (front and back). 26" wheels are adult sized, and will usually come with standar derailleur type gearing. They can be used on or off road, however remember the wider the tyres, and the heavier the frame, the less efficient and more work it is to ride on the road. Rear suspesion will swallow between 20% and 30% of your energy depending on how soft the shock unit is set. For off road riding, it depends on what style of off road riding you will be doing as to which frame type you go for.
Cross Country (XC) riding should be undertaken with a rigid steel or chromoly frame, or aluminium frame with front suspension only. tyres should not be more than 26x2.1 in width in order to maintain fast progress up hills and across flats.
Full Suspension (FS) bikes were originally designed with the main purpose of down hill racing. the rear suspension unit allowed the rider to place a lot of weight on the back wheel, and the suspension would stop the back end losing contact with the rough ground. this allowed the rider to gain as much control over the bike because the back wheel would also be braking as well as the front (remember you cant slow a bike down if the back wheel is not gripping anything). in the same way Formula 1 racing spawned thousands of (ineffective) rear spoilers on your everyday car as a go-faster fashion accessory, rear suspension filtered down to your everyday bike to make that look a bit more sporty. in reality it actually just makes the bike a lot heavier, more effort to ride, and more unreliable.
Work out what size bike you will need:
All sort sof people are different sizes and shapes, but the basics apply to most people. frame size is worked out as the distance between the middle of the 2 pedals (where the bottom bracket is) to the top of the frame where the seat post goes in. However remember that where the bottom brack is in relation to the ground varies from typ eof bike to type of bike. Premium off road bikes liek GT's and Carrera frames will have a very high bottom bracket to allow for as much clearance as possible off road, wheras on cheaper bikes and road/hybrid bikes it will be a lot lower, as the highest obstacle you typically come across on roads is a curb! so on premium off road bikes, the frame size you require may well be smaller. also remember that the reach of the handle bars (distance between top of frame where seatpost goes in to the front og the frame where the forks go through) increases in scale with the height of the frame.
As a rule:
4'8 -5'3 people have arms that will reach a 16" premium off road bike/17" hybrid comfortably,
5'4-5'10 should go for a 18" premium off road frame/18-19" hybrid/cheap frame
people over 5'10 should go for the 20-22" frames.
Inspect the bike before buying/bidding:
Like buying a 2nd hand car, you should inspect and take a 2nd hand bike for a test ride if at all possible first. Bikes will cost about £20 to courier, and have a 50/50 chance of getting damaged en route, so collection is always recommended anyway, and £20 in petrol equates to approximately a 100 mile radius from your home which gives you plenty of choice.
Consider Possible Repair Costs:
Unless you are an experienced bike mechanic (which if u were you shouldnt need to read this) then you need to remember servicing and repair charges are pretty high for bikes, which is largely the reason why youll find so many bikes on ebay going cheap, as it isnt economical to repair unless you can do the work yourself.
Bikes that originally retailed for up to 150 quid were built to a price. Things to remember are that they were designed to be disposable, i.e werent expected to last more than 2-3 years of day to day use:
Hubs: unbranded or cheap hubs made out of cheap metal that arent machined well will feel lumpy when wheel is spun. after a few years the cones (nuts that hold the spindle onto the hub) slacken. if the bike has been poorly cared for and not regularly maintained (i.e tightening the cones) then the bearings often carve into the soft hub when there is play in the cones, meanign that irrepairable damage has been caused, and a new wheel is required (about £25). remember a new rear wheel will also require your old cogs to be put on (halfords charge £8) and youll have to put your rim tape and inner tube and tyre on (halfords charge £6.49)
Rims: unbranded or cheap rims will often be suceptable to buckling. Buckles can be trued out (depending on how bad halfords charge £15-25), but if there is more than 2.5mm play either way of true centre you will need to replace the wheel (same costs as above)
Bottom Brackets: there are several types. on very cheap bikes they will usually comprise of either a spindle bottom bracket, or a one piece crankset. both bottom brackets work in teh same way as a wheel hub, and the same problems can occur if the bike is not looked after. some higher spec bikes will have what they call a "sealed bottom bracket cartridge" which have all the internals in one unit, and are virtually maintenance free. the unit just screws into the frame. The only problem with sealed bottom brakes is if the bikes been hit by a car, or been dropped and landed pedal/crank first, it can damage internals of the BB, so if on a test ride you feel/hear a knockign sound as your pedal goes round once every revolution (usually under loading, i.e goign up hill) you will need to replace the bb - £17 for the BB and £13 for labour.
Crank Arms: Sealed bottom brackets and spindle bottom brackets will require crank arms to fit on them (these are the bits pedals screw into). unless you buy a £500+ bike with splined bottom brackets, the bottom bracket will have 2 tapered square ends, which your crank arms fit on. all too often on cheap bikes, **Especially Saracens** the screw which stops them sliding off, either loosens or becomes dethreaded. if this isnt checked regularly and kept tight, your crank arms have the abilty to round the square hole that was cut in them, this renders them irrepairable, and will then need to be replaced. and you cannot usually buy just the one crank, you will normally need to buy a "chainset" as the front cogs (chainrings) are normally permantly fixed to the right crank on a budget bike (these cost about £30+ and halfords charge £13 labour to replace them)
Suspension Forks: Any seized forks will require strippign down and lots of TLC. cheap suspension forks are usually made from steel and are highly susceptable to rusting. a fork service is about £30 to get them working again and will never work as well as new ones. regular maintenance such as sprayign a water dispersant onto them after every damp weather ride, or cleanign of a bike will stop this, but many people dont bother. also after a year of use, the rubber seals that resist allowing water into the internals often perishes away.
Rear suspension: After a short while of use, y-frame full suspension bikes suffer play in the pivot points caused by cheap nylon bushes wearing out. this can be fixed by replacign the nylon bushes. however you cant always purchase these as spares! and no amount of tightening will work as the bolts have an internal thread!
Tyres & Tubes: Tyres for cycles cost £10 per tyre at halfords, etc, inner tubes are about a fiver, so bear in mind if both tyres are perished, and the inner tubes are punctured your looking at £30 already in parts. as well as this, labour for replacing the front + rear tubes or/and tyres will be £11 too. so consider £41 on top of your purchase price if you dont knwo how to change them.
Brakes: V-brake sets (front and rear) will set you back abotu £30 if they are missing parts. rarely can you buy the parts separately. (except the handle bar levers) brake pads (pair) are £5-7. Disc brake pads are £14, and a new disc brake caliper and disc is £55.
Beware of sellers claims of how much they paid for a bike
Liek most shops these days, halfords and other places sell bikes with "half price signs" so sellers often quote the original prices, in order to make you bid higher, or even make up there own! before buyign second hand, look in a shop liek halfords and note the quality of the parts fitted to various bikes (without any huge reductions!! on them) familiarise yourself with what are quality components etc, staff are usually quite knowledgable (mine were) and ask for there *personal* opinion. also most aluminium framed bikes have a 2 year warranty to cover them against cracking/poor welds. try and get the seller to produce the original recept by mentioning this if the bikes under 2 years old, as this also allows you to make sure your nto gettign ripped off. you wont need any proof of who u are as logn as you have proof of purchase to claim on the warranty.
If all of this hasnt put you off buying a second hand bike, then go for it, as there are some real bargains to be had on here, ill update this if possible later on, but if you have any problems or need any advice on anythign drop me a message (click my user name bit at the top as ill help out best i can, time permitting)
Oh and one more thing - a skedaddle/promotive ds500 is a terrible bike. we sent 5 back after a week when they came into our store. and i notice there still being sold for (a rip off) 135 on here - AVOID!!!
Take care and happy bidding