Dr Bike – notes for testers

Your aim is to encourage people to ride their bikes, but the immediate job of Dr Bike’s test is to identify what is wrong with the bike. Don’t ever ‘pass’ anything or assure anyone that a bike is perfect, for legal reasons. Don’t write ticks in the form’s boxes: just crosses to mark failure. That said, be as positive as you can. It’s quite rare for a bike to be unrepairable.

Tell the owner that the test takes ten to twenty minutes, and that she’s welcome to help you check over the bike. You’ll need the rider anyway to make sure the bike is adjusted more-or-less correctly. We can’t give quotations or estimates for putting things right, but if you have a rough idea of whether a bike shop will charge £3, £10, £30 or £100 for a repair, by all means say so. Don’t write down prices!

Work through the test sheet in order, unless there’s something needing obvious attention first. Fill in the remarks as you go. It’s quicker to have a helper read out the prompts from the sheet and make notes.

Front tyre

Good tread; no splits, cracks or holes; pumped hard. Look also to make sure the tyre is properly seated on the rim. You don’t need much tread on a cycle tyre used on the road: it’s mainly to show how worn the tyre is. Tyres start to suffer from frequent punctures before they get so worn as to be dangerous, but bulges and splits are urgent matters. Look for the pressure marking on the sidewall, but don’t pump up the tyre until you’ve finished checking the wheel. Check that the valve isn’t twisted to one side by careless work or by riding on a nearly flat tyre.

Front wheel

True; no broken or missing spokes; good rim. You can look at the rim as you check the tyre. Modern rims can wear quite thin (the brake blocks score away the metal), as well as getting dinged and twisted. Check for broken spokes by squeezing pairs of spokes together, reasonably hard. A new wheel can be up to 2 mm away from true; depending on the bike, up to about 6 mm is acceptable, depending on how the brakes work. A smoothly untrue wheel can usually be fixed (by a bike shop); one with sharp wiggles may need replacement. You don’t have to decide – just write down ‘not true’ and leave it to a shop.

Front hub

No wobble; turns smoothly. Listen for a noise, and take hold of the rim and wiggle it from side to side. If you can feel some wobble but not see it, that’s okay. If you can see a few mm of wobble, that’s not okay.

Front mudguard

Firmly fixed. It’s dangerous if it can get caught in the wheel.

Front brake blocks

Correctly fitted and aligned; not worn away. Make sure each brake block meets the rim, and doesn’t touch the tyre or waste itself against the air. Be fussy about brake blocks: they are both vital and cheap.

Front brake

Correctly adjusted; cable and calliper safely fixed. Look for rusted and frayed cable, too. Be fussy about everything to do with brakes. They rarely need replacing, but often need urgent attention.

Front brake lever

Comfortable position; firmly fixed; cable not frayed. Look (usually inside) at the end of the cable to make sure it’s not too rusty or worn. This is where brake cables generally snap, if they’re going to. Try the brake to make sure it works smoothly and without unreasonable hand force. If it needs a new cable, write that down in the Remarks box.


No wobble; correctly adjusted. Badly worn headsets affect steering and braking.


Not distorted; ends protected. End plugs are there to avoid injury in an accident, not just for show. Make sure the bars are symmetrical (it’s very difficult to correct a bent aluminium handlebar) and correctly aligned with the front wheel. You can check handlebar height at the same time as saddle height (later) if you like.

Front forks

Appear true and undamaged. There’s not much you can do except look for dents, kinks and gross rust. They’re quite serious problems, though.


Appears true and undamaged. Look along the length of the bike to see if the wheels are obviously out of line., as well as looking for obvious damage and rust. A bent frame probably means the bike’s been run over by a car.

Rear brake lever

Comfortable position; firmly fixed; cable not frayed. Same checks as for front brake lever.

Rear brake

Correctly adjusted; cable and calliper safely fixed. Open frame (‘ladies’) bicycle brakes often have rusted cables, because rainwater runs into the cable at the calliper end. These usually need new cable. Recommend lined cable and suggest the back brake cable be re-routed so as to join the brake from above, not below. (A squirt of oil may cure the problem, and is worth trying, but usually doesn’t help.)

Rear brake blocks

Correctly fitted and aligned; not worn away. Same checks as for front brake blocks.

Rear mudguard

Safely fixed; no sharp mudguard stays. A jammed rear mudguard isn’t as dangerous as a front one, because it will cause a skid rather than a ‘cropper.’

Rear tyre

Good tread; no splits, cracks or holes; pumped hard. Same checks as for front tyre.

Rear wheel

True; no broken or missing spokes; good rim. Same checks as for the front wheel.

Rear hub

No wobble; turns smoothly. A hub-geared bike usually has a little bit of wobble on the back wheel (easily felt, just slightly visible).

Bottom bracket

No wobble; lock ring tight; sufficiently lubricated. The right-hand bearing cup is not adjustable and should be fully tightened (left-hand thread on most British machines). The left-hand cup is adjustable and should be fixed in place by its lock ring. Sealed bottom brackets are now quite common: these have hollow ends where you expect to see bearing cups, and no adjustment is possible.

Pedal cranks

Straight; fixed securely. Note that a loose left-hand cotterless crank generally needs to be replaced (£10 or so) because even a few hundred yards riding will damage the aluminium socket.


Complete; turning freely; not bent.


Not bent; teeth not worn. Modern chainwheel teeth are often ground down to funny shapes to make gear changing go more smoothly. Don’t fail these!


Not too worn; not slack; greased not rusty. Check for wear with a 12″ ruler. A new chain has exactly 24 half-inch links over this length. It’s a good idea to replace an chain which has worn by 1/16 inch, and usually only the chain needs replacing then. If it’s worn by 1/8 inch, the freewheel or cassette will probably need to be replaced as well (£5 up for a new chain; £15 up for a new freewheel). In between, you may be lucky and get away with just a new chain. Over 1/8 inch wear and it’s definitely time for a new chain and freewheel. (That doesn’t apply so strictly to hub geared or single-speed bikes: just recommend a new chain after 1/16 to 1/8 inches of wear.)


Properly adjusted; lubricated sufficiently. 3-speed gears have a simple adjustment; for derailleur gears, check the rear mechanism limit screws, rear index alignment, front limit screws, and front index adjustment – or whatever subset of these applies. Check the operating cables for rust and fraying. Make sure the freewheel works.


Safely fixed; straight; comfortable height (excluding BMX). This is where you get the rider to balance on the bike and tell her or him that the saddle’s set much too low. Check the reach forward to the handlebars and their height at the same time. While you’re checking the rider as well as the bike, be prepared to advise on wearing a helmet properly – level on the top of the head, strap under the back of the chin, tight enough that it can’t loosen and move out of place before it does its job in a crash.


Firmly secured. Don’t forget the front basket, as well as the back rack.

Front lamp (if carried)

White; firmly fixed; good light to front; correct height.

Rear lamp (if carried)

Red; firmly fixed; visible to rear; correct height.

Rear reflectors

Clean and secure; visible to rear; correct height. Remind the owner that a red rear reflector is a legal requirement after dark on the roads, even if you’re only pushing the bike rather than riding it. The other reflectors aren’t, although they are required ‘at the point of sale’ and are useful additions to lights.


Almost every bike we test has soft tyres. If both wheels haven’t failed on anything else, offer to pump up the tyres. Don’t do this for any tyre or rim which seems suspect, and do check to make sure the valve is straight and the tube not trapped under the tyre bead. If in doubt, deflate the tyre completely and push on the tyre sidewalls to loosen the bead from the rim, then inflate it. I generally don’t pump old tyres up to their full rated pressure if they’ve been used for a long time at a much lower pressure. Split the difference between the pressure you find and the maximum rating. For example, if a tyre’s at about 25 psi and is rated for 65 psi, pump it up to about 45 psi rather than the full 65. This reduces complaints about the harsh ride and lessens the chance of your blowing the tyre off the rim.

Mark Irving 14 June 1998