Repairs

In this section we have included details of the following repairs & adjustments:

PUNCTURES

BRAKE ADJUSTMENT & CABLE REPLACEMENT

SADDLE POSITION

GEAR CABLE REPLACEMENT

CHAIN REPLACEMENT

CRANK REMOVAL

PEDAL REPLACEMENT

BOTTOM BRACKET ADJUSTMENT

FREEWHEEL/CASSETTE REMOVAL

HUB AND WHEELS 

HEADSET ADJUSTMENT 


We would advise that you always ensure that you have the correct tools to do the job before you start any repair so watch the videos first if you are in any doubt. 


PUNCTURES 

          In addition to our detailed instructions you can VIEW a repair by clicking here. 


  1. Remove the tyre & inner tube to locate the puncture. To do this insert the flat end of a tyre lever between the tyre & rim in an area of the tyre well away from the valve. Lever out the tyre & using the hook end of the lever attach it to a spoke. Insert the next lever about 3 inches along from the 1st & hook to a spoke. Then do similar with the 3rd lever & the middle lever will drop out. Continue inserting a lever like this until you can use it to drag around the remainder of the tyre so one side is completely released. Then pull the valve of the inner tube out & the remainder of the tube will drop out. Leave the tyre attached to the wheel on one side.
  2. Re-inflate the inner tube until you either hear or feel the air on your face or lips escaping through the hole by holding the tube close to you. If you cannot locate the hole immerse the reinflated tube in a bowl of water & look for the bubbles of air escaping. Mark the position of the puncture. Try to keep the position of the tyre & inner tube matching the position they were on the bike you can trace the point on the tyre where debris may have entered the tyre to cause the puncture & remove any remaining object. It's also worth checking the rest of the tyre.
  3. Roughen the area around the puncture hole with sandpaper & then clean that area of the tube.
  4. Apply glue to the area around the hole ensuring that you cover an area slightly larger than the patch you will use & allow it to become tacky.
  5. Peel the foil from the back of the patch & press it firmly over the puncture hole - it can help to use the removed foil to press onto the new patch.
  6. Leave the patch to set for a few minutes then peel off all the cellophane backing from it.
  7. Apply chalk or talcum powder to the area around the patch.
  8. Partially inflate the tube & check the patch is sealed.
  9. The tyre should have been left with one side fitted over the wheel rim - if not fit one side over, checking if there is a rotational arrow on the tyre that you fit it in the direction of motion indicated - then insert a slightly inflated tube underneath starting with insertion of the valve through the hole in the wheel rim.
  10. If you are repairing a puncture on the roadside & have a bad tear in the tyre, if you have carried a section of inner tube, then slip this under the tear & over the tube to give it extra support.
  11. Complete the fitting of the tyre fully onto the wheel by gradually working the tyre back over the rim as you rotate the wheel. Be careful at the final point of closure not to trap the tube between the rim & tyre.
  12. Squeeze the sides of the tyre as you fully rotate the wheel to check the tyre sits properly on the wheel & is not trapping the inner tube at any point.
  13. Fit the wheel onto the bike & tighten it in the dropouts. Make sure the wheel runs exactly in line with the frame of the bike & adjust its position in the dropouts as necessary.

  14. Close the quick release on the brakes or attach the cable anchor bolt to its seat in the brake arm depending on your type of bike.
  15. Fully inflate the tyre

BRAKE ADJUSTMENT & CABLE REPLACEMENT   

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Your brake lever should move about 2cm before beginning to grip the wheel. If you find that the brakes levers are moving more than this you should check the brake pads to see if they are badly worn & need replacing. If the pads are OK then you can tighten the brake by rotating the barrel adjuster. This will either be located where the cable enters the brake lever or where the cable enters the brake arm, just above the brake pads. If you rotate the barrel adjuster - usually - anticlockwise this will extend the length the cable has to travel & tighten the brake. If the brakes are too tight reverse the barrel adjuster. It is a matter of feel so pull the lever after you have made each small rotation to make sure it is having the desired affect.

Do NOT rotate the adjuster too far as you will expose the entire bolt within the barrel adjuster. If this happens twist it back into place & a more thorough adjustment of the brake is needed. This may involve seeking professional help.

To VIEW how to replace a brake cable on a straight handlebar - MTB style bike - click here.    

 

SADDLE POSITION                                                                               

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Your saddle should be completely level & at a height where you can just reach the ground with your toes. It is usually held in place by a bolt found directly underneath the saddle & you can adjust the tilt of the saddle by pressing on the front or back of the saddle to get it level then secure tightly. If the saddle sits on rails then it should be centrally placed on them.

The height of the saddle is adjusted by means of the seat post bolt found behind the top tube at the top of the seat tube. The saddle sits on top of a seat post with a maximum height limit line -  DO NOT exceed this. The seat post itself should be well greased before it is positioned in the seat tube or use talcum powder if you have a carbon frame/post.

To set the saddle height rest your heel on the pedal with your knee straight. This means that in normal riding with the ball of you foot on the pedal your knee will be slightly bent. You may find that after riding with the saddle at this height you may prefer it to be fractionally higher or lower so do small adjustments to get your preferred position. After adjustment secure the saddle post bolt firmly & check it doesn't move if you twist the saddle.

If you have a youngster then position the saddle height for them so they can reach the ground with their feet.

You can VIEW this adjustment by clicking here.    

GEAR CABLE REPLACEMENT                    

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It helps to do these repairs on a workstand but if not ask a friend to assist by lifting the rear wheel to check the chain movement after the repair has been made. If you have grip shift levers then this video clip will help show the steps to take. Please note that some grip shifters don't require you to take them apart, just feed the new cable through with the shifter set for the gear on the smallest sprocket or chainring.

FRONT MECH - this unit controls the movement of the chain over the large chainrings attached to the right pedal crank

If the cable has frayed look at the point this has occurred to ascertain the fault e.g. corrosion - insufficient lubricant, damaged outer cable housing (so this will also need replacing).

To fit this cable you should have the chain on the small inner chainring at the front & the largest sprocket of the cassette at the rear.

Remove all the existing cable - this may involve taking the housing of the gear lever apart depending on type of lever you have. Lubricate the sections of the cable that fit inside the outer housing & the nipple at the end of the wire. Fit the wire into the gear lever & pull through until the nipple sits inside the lever. Feed the cable through the ferrules at all outer cable ends & pull the cable through until it reaches the anchor bolt of the mech. Pull the cable tight & attach at the anchor bolt. Leave about 30 - 40mm of cable beyond beyond the anchor bolt & snip off the excess wire. Fit a cap to stop the wire fraying & secure using pliers.

Check your chain now moves smoothly across the chainrings & the range of rear gears.

There are limit screws that affect the chains movement which may need adjustment - refer to the cobr site for further details & other general front mech information. This video clip will also greatly assist you with the repair.

REAR MECH - this unit controls the movement of the chain over the rear gears

If the cable has frayed look at the point this has occurred to ascertain the fault e.g. corrosion - insufficient lubricant, damaged outer cable housing (so this will also need replacing).

To fit this cable you should have the chain on the large outer chainring at the front & the small sprocket of the cassette at the rear.

Remove all the existing cable - this may involve taking the housing of the gear lever apart depending on type of lever you have. Lubricate the sections of the cable that fit inside the outer housing & the nipple at the end of the wire. Fit the wire into the gear lever & pull through until the nipple sits inside the lever. Feed the cable through the ferrules at all outer cable ends & pull the cable through until it reaches the anchor bolt of the mech. Check the adjuster barrel - normally found at the point the cable enters the rear mech - is in mid-position of its range of movement.

Pull the cable tight & attach at the anchor bolt. Leave about 30 - 40mm of cable beyond beyond the anchor bolt & snip off the excess wire. Fit a cap to stop the wire fraying & secure using pliers.

If you have index gears then click the gear lever once for the chain to move onto the 2nd sprocket. Now rotate the pedal as though you are cycling & move the adjuster barrel by quarter turns anti-clockwise until the chain moves smoothly onto the 2nd sprocket & runs quietly. If the chain is on the 2nd sprocket rotate the adjuster barrel clockwise (to move the chain towards the small sprocket) or anti-clockwise (chain moves towards the 3rd sprocket) until you achieve the optimum position.

Check your chain now moves smoothly across the range of rear gears & check this for each chainring position. Further rotate the barrel adjuster as required to ensure smooth movement.

There are limit screws that affect the chains movement which may need adjustment the cobr site for further details & other general rear mech information. You may also want to view this video clip for details.

        

CHAIN REPLACEMENT                                             

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The main reason to break a chain is to replace it completely or, & more unusually, to replace a damaged section of links. If you had chain slip as you were going along then not only does the chain need replacing but the rear gears/cassette.

Depending on the type of chain connection that you have on your bike: View this video if you have a quick release connecting link by clicking here. If the chain has no quick release link then view this video.  The videos explain the differences in these two types of chain and show the types of tools you will need. Once a new chain has been installed then check it moves smoothly through all the gears on the bike & there are no stiff links needing further attention.

CRANK REMOVAL

This adjustment is normally necessary only when you require to work on the bottom bracket so we have included this video as it is the gateway to working on that part of the bike. If you need to replace your chain and rear gears you shouldn't have to replace the chainset - the general name for the cranks & front gears - as they don't tend to wear at the same rate. The cranks are secured to the bottom bracket in the example shown by end bolts which is known as a cotterless crank.

Cottered crank - if you have cranks secured by cotter pins that slot through the crank arm, clamp against a flat section of the axle & are secured by a nut on the other side of the crank, these can be removed by knocking out the pin with a hammer applied to the threaded end of the pin. Do remember to take off the nut first. Grease the pin before replacing taking care to position the pin back correctly as the slotted side needs to face the flat cut out section of the axle. If you are in any doubt refer to this link or consult your local dealer.

PEDAL REPLACEMENT    

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You will only need to do this if the bearings in the existing pedals are worn or damaged or your are upgrading to a better pedal.

This job is made easier if you have a long handled 15mm spanner & you can buy these from cycle shops specifically for this purpose for a few pounds. Old pedals can be very tightly inserted to the crank so try using WD40 or similar at the point where the pedal attaches to the crank if this is the case. You need to place the spanner on the flats of the shaft where the pedal attaches to the crank. The pedal on the left side has a left hand thread so is removed by turning the spanner clockwise. The right hand pedal - which attaches to the crank by the chainrings - has a right hand thread so is removed in the usual anti-clockwise direction.

If the pedals are not too tightly attached to the crank you may be able to undo each pedal by using an allen key on the inside of the crank where each pedal has threaded through to but a pedal spanner is usually required because of the extra leverage it has. 

Clean the threads of the cranks before you attach the new pedals. An old toothbrush & degreaser should be fine for this.

Use a good quality lubricant to the threads of the new pedals & turn the shaft of left pedal anti-clockwise by hand to twist it into the crank. Then in a similar manner turn right pedal clockwise to attach to the crank then tighten both pedals with a spanner. View this repair by clicking here.

BOTTOM BRACKET ADJUSTMENT

There are a number of different styles of bottom brackets from those with bearings that are adjusted manually & require re-greasing as part of an annual service to sealed units that require little attention. This video shows how to service the former an adjustable bottom bracket. There are different types of seal so the tools required for your bike may vary from those shown. If in doubt consult your local dealer. If you have a sealed unit & it needs to be replaced due to excessive wear then click here.

FREEWHEEL/CASSETTE REMOVAL                                                                                                           BACK TO TOP 

This refers to the gears at the rear of your bike and replacement should only be necessary if the part is worn e.g. you have experienced chain slip as you ride along or some of the teeth on the sprockets are bent or damaged. It is not necessary to remove it to clean the sprockets. A freewheel is a set of sprockets that contains a hub that screws onto the flange of the wheel. A cassette slips onto a hub body attached to the wheel. The video clips referred to below explain how to go about removal.

To remove a freewheel view this. For a cassette then click here for details.

HUBS AND WHEELS  

It is important that your wheels run true & that there is no play in the bearings or you will eventually have to replace the complete wheel if you continue to ride with a problem.

HUBS: If you notice any sideways play in your wheels for instance in your own maintenance check then you should check the hub bearings. Its easiest to test for this with the wheel lifted slightly off the ground then try to move it sideways to check that there is no movement against the bearings in the axle. If you do detect movement then this video will help you resolve the problem.

WHEELS: At some point you are likely to find that a spoke breaks or the wheel runs out of true. This can normally be detected by the wheel rim severely contacting the brake as you ride. If a spoke needs replacing you can see how to go about replacing it here. 

Wheel truing is not always straightforward but develops with experience, it can be considered as an art rather than just a repair - this clip shows you what to do. A truing stand is basically essential. You can find more information on wheel truing on the Park Tools site if you click here.

General advice:

  • Check that there is no play in the hub bearings before attempting spoke repairs 
  • The spoke nipple should be turned to make any adjustment, the spoke itself should not move
  • Use the correct size spoke key
  • Mark the section of the rim you need to work on with chalk so you don't get confused with another problem area of the wheel
  • Work by only making small adjustments to each nipple such as quarter turns and no more than half turns
  • The nipple tightens on a right hand thread but if you work below the wheel centre i.e. with the nipple facing the ground it is turned anti-clockwise to increase the tension in the spoke & loosened by turning clockwise
  • When a wheel is viewed side on tightening a spoke nipple on the left side of the rim will pull the rim to the left. If you loosen the same nipple the rim will move to the right
  • Again viewing side on a nipple tightened on the right side of the rim will pull the wheel to the right but if loosened the rim will move to the left
  • Work each problem area by slightly tightening nipples on one side of the rim & loosening the other side until the desired alignment is attained
  • All spokes on a front wheel should have an equal sounding tension if you pluck the centre of the spoke
  • The spokes on each side of a rear wheel should have a similar sounding tension but the derailleur side spokes will sound different to the other side due to different spoke alignments

HEADSET ADJUSTMENT

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There are two basic types of headset, threaded or threadless and you can view how to adjust either on the following videos. You should only attempt such a repair if you detect looseness in the headset or bars.

To check this firmly apply the front brake and push the bike back & forward with the front wheel remaining on the ground causing the rear wheel to rise up. If you notice any looseness as you rock the bike then the likely problem is in the headset.  Noise or stiffness when cornering are also warning signs to look out for. After this check also try the handlebars for looseness by gripping the front wheel between your knees & trying to rotate them within the stem.

Click for threaded or threadless to watch the videos of this topic but if in doubt consult a dealer.