Each week the Used Car Roadshow resident mechanic Pipes shares tips and tricks on basic motoring maintenance.

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Ask Pipes

Series 3 - Episode 1

Tyres

Tyres are the most important component on any car, they are the only thing attaching you and the car to the road, looking after them is crucial and should be checked every week.

Modern tyres are of a radial construction and are tubeless.  There is a lot of information on the sidewall including width; aspect ratio; construction; diameter; speed rating; load rating; date of construction; direction of rotation; maximum inflation pressure; weight markings and run out markings (coloured dots and lines on new tyres).  The correct inflation for the tyres on your car are printed on a data sticker and located either inside the fuel filler flap or in the drivers door shut area.

The legal limit for tyre tread depth is 1.6mm across 75% of the width and frankly this is ludicrous.  The law should be changed to 3mm, as a car so equipped will stop over 40 metres earlier from 70mph in the wet compared to a car whose tyres are just on the legal limit.  If you were to check, you will not find a police pursuit car anywhere in the country with tread below 3mm.

Ideally you should equip your car with the same tyres all round but it is okay to mix front or rear, but never two tyres on the same axle. 

Abnormal wear on a tyre can be caused by a number of aspects.  Firstly, over-inflation will cause the middle of the tyre to wear and under-inflation will cause both edges to wear.  Suspension geometry is also key to tyre wear, if you bash a kerb and knock out the geometry you will get abnormal tyre wear.  On older cars with higher mileages it is common for suspension bushes to wear and cause uneven tyre wear.  In all of these cases it is essential to have the geometry set correctly before fitting new tyres otherwise these will wear twice as quickly.

Tyres generally have a shelf life of 6 years and can show signs of cracking even if the car has not been used.  These should be replaced.  Likewise, if the sidewall has been damaged the tyre should be replaced.

Punctures are repairable as long as they are not too near the edges.  Run flat tyre technology is becoming more common, these tyres have very thick side walls, so much so that when fully deflated will allow the car to travel safely at 50mph without the tyre coming off the rim, as it would on a normal tyre.

When checking tread depth, you will find wear indicators in the tread pattern of your tyres.  These bars indicate 2mm of tread remaining.  You can buy a very simple depth indicator from a motor accessory shop for a more accurate reading.  If your car has wide tyres, turn the steering to full lock and this will help you check the complete face of the tyre quite easily.

Series 3 - Episode 2

Jump starting

Should be avoided if at all possible.  Instead use a long trickle charge overnight to recharge your battery.  It will last longer this way.  When trickle charging, if your charger isn’t microprocessor controlled, put it on a timer for 8 hours. 

If you have to jump start, wear eye protection as the battery may explode in extreme circumstances.  You should also not wear loose clothing when working under the bonnet of a car to avoid it getting caught in moving pulleys and belts etc.  Take care also when working around batteries not to short out the positive and negative terminals with loose jewellery or tools as this will cause sparks.

Ensure the two cars are not touching.  First attach the red lead to the positive terminal on the donor car’s battery.  Second, connect the other end to the positive terminal of the dead battery.  Third, connect the black lead to the donor cars negative terminal.  Fourth, connect the other end to a suitable earthing point on the donor cars engine or chassis, away from battery and fuel system.  It is important to connect the leads in this order to minimise damage to the battery. 

Now wait a few minutes for the voltages to stabilise then start the donor car and run on a fast idle.  After a minute or so attempt to crank the dead car.  Do not remove any of the jump leads with either of the cars running.  Lastly, turn off both cars and wait a few minutes for the leads to cool down before removing them in the reverse order of connection. 

Batteries are designed to be recharged and discharged all of the time.  They can last up to five years, however, this depends on usage.  Cars that do high mileages are constantly charging the battery but cars that are seldom used and moved short distances all of the time (as on a car dealers forecourt) can destroy a battery over a short period of time.

A common misconception is that leaving the car running on tick over for 10 minutes or so will charge the battery.  This does not give the battery a meaningful charge, the engine needs to be running at a good speed for a reasonable time in order for the alternator to supply a worthwhile charge.

Most modern batteries have an indicator light which changes colour when it needs a charge or is dead. 

Over the years as battery technology and charging systems have improved, the average voltage supplied by the alternator for recharging has increased from 13.6 to 14.4 volts.  For this reason it is very important than when replacing a battery you use the manufacturers recommended specification.  It is quite common for owners of older cars to fit more high tech batteries and their cars’ alternator does not supply enough voltage to recharge it and it very quickly dies.

Series 3 - Episode 3

Wiper blades

The best way to maintain your wiper blades is to wash them every time you wash your car – you’ll be amazed how much grime can accumulate on them.  Always use proper screen wash as it is specially formulated to help dislodge road grime but not at the expense of wiper blades and rubber seals and is also resistant to freezing.  Don’t be tempted to use household detergents in your screen wash reservoir.  They can clog the system up and eventually go off and smell bad, let alone long term damage to seals. 

Never operate your wipers on a frosted screen to aid clearing as this permanently damages them, they are only designed to work on an extremely smooth surface i.e. glass.  When replacing wiper blades it is advisable to replace the complete blades and not just the rubbers because the spring mechanism on the blade also wears with time.  Before removing the old blades, purchase the new ones to the correct specification and only remove the old ones when the new ones have been offered up to the wiper arms and their correct attachment identified. 

Don’t try to “supersize” your wiper blade/s in order to gain a greater sweep as this will result in a less efficient wipe and could even damage your paintwork. 

When replacing the front wiper blades remember to replace the rear one if fitted. 

A top tip to those that actually use car polish, do the windows lightly as well when doing the body work and they will stay grime free for longer.

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