Sunday, January 02, 2011

Tyre Tips

TYRE TIPS.

This is a short article designed to give some basic tips on motorcycle tyre maintenance and safety.

The tyres on your motorcycle are an engineered component, for example did you know each tyre is assembled from up to 30 component parts? each part is designed to perform a specific task, and different rubber compounds are used in each part of the tyre 20 to 30 different rubber compounds can be used in a tyre. These rubber compounds are reinforced with materials such as steel, nylon,rayon,polyester,and kevlar. So whilst tyres appear round, black and boring they are in fact the most important components on your machine.

SIZES AND TYPES.

As a general rule most motorcycle tyre manufacturers recommend that you stick with the original sizes of tyre as specified by your machines manufacturer, this is because a great deal of testing takes place before any motorcycle manufacturer decides on tyre sizes for a particular model. Whilst it is often possible to fit alternative sizes, this should only be done after consulting the motorcycle manufacturer.

INFLATION PRESSURE.

Without doubt the most important factor with regards to tyre safety and life is inflation pressure, it is the air inside the tyre that carries the load so always use the inflation pressures as quoted by the motorcycle manufacturer. Check the inflation pressures when the tyres are cold, this is because tyres warm up in use and inflation pressures which are correct when the tyre is cold can increase by 10% when the tyre is hot. So setting the tyre at the correct cold inflation pressure when the tyre is hot will result in an under inflated tyre.

VALVE CAPS.

Always make sure you have valve caps fitted, whilst they may seem small insignificant items, valve caps perform a vital function, they prevent road dirt entering the valve stem and damaging the valve core. A damaged valve core will allow the tyres inflation pressure to leak out.

By far the best type of valve cap to fit is a high pressure one, these are usually of metal construction and have an internal rubber seal. The advantage of a high pressure valve cap is that it will retain inflation pressure, even if the valve core is damaged. This extra margin of safety is well worth having

INSPECTION.

You should inspect your tyres regularly for adequate tread depth and obvious signs of damage, such as cuts and bulges.

MINIMUM TREAD DEPTH.

The minimum legal tyre tread depth for Motorcycles over 49cc is 1 mm, however this should be treated as a bare minimum and many motorcyclists replace their tyres at 2 mm.

Some motorcycle manufacturers recommend that tyres are replaced long before reaching the minimum legal tread depth, for example Kawasaki say that tyres on their GPX600R and GPX750R should be replaced at 1 mm front and 2 mm rear for operation at speeds up to 80 MPH (130KPH) and 1 mm Front and 3 mm Rear for speeds above 80 MPH (130 KPH).

All tyres have a number of tread wear indicators placed in the tread around the circumference of the tyre. The indicators are set at 1.6mm and serve as a guide to the degree of wear in the tread, the idea is whilst you are inspecting the tyre you look to see if the tyre is worn to this level, if so you know that tyre is ready for replacement

You can find the tread wear indicators on your tyres by looking for the letters "TWI" in the shoulder area of your machines tyres, on closer inspection you will see that there is a slightly raised area in the base of the tread groove at this point.

Tread wear indicators serve as a quick and simple aid to checking tyre tread depth if you don't have a tyre tread depth gauge available.

REPAIRS.

Tyres can sometimes be repaired, but care has to be taken, firstly the standard for tyre repair in the U.K is British Standard BS AU 159F. This standard lays down in great detail the way tyres should be repaired, the amount and type of damage that can be repaired. As you can imagine the standard is very detailed and as the purpose of this article is to give you some tips on tyre care, so I will sum up the main points you need to be aware of.

1. Some high speed rated tyres cannot be repaired at all. This generally applies to tyres with a speed rating higher than H (130 MPH). This is because tests have is because tests have shown that repair materials will not work in these highly stressed tyres.

2. All penetrations should be plugged to prevent the ingress of moisture into the tyre structure.

3. Tyres should not be repaired with sealants. On this latter point it is my personal opinion that sealants of both the prior and post puncture type are nothing short of dangerous, and you are much safer pushing your bike home than using them.

RUNNING TYRES IN.

Bridgestone and other tyre manufacturers recommend that you "Run in" new tyres for approx. 100 miles before they are used to their maximum.

CLEANING YOUR MACHINE, OILS AND GREASES.

This may seem a subject that has nothing to do with tyres at first but it is vital that you prevent your tyres coming into contact with any petrochemical such as Oil, Diesel , Gunk or other propriety degreaser for any length of time. This is because oils are used in the manufacture of tyres, infact synthetic rubber is produced from oil and oil based products will attack the rubber compounds used in tyres.

Rubber which is exposed to oil based substances for any prolonged time will change from a hard to a softer "spongy" texture, the result can be a lack of grip or failure of the tyre structure. So if like me you use a degreaser to clean parts of your machine, take care to prevent any coming into contact with your tyres, and if by accident any should find its way onto the tyres wash or wipe it off immediately. For the same reason take care at filling stations around Diesel pumps, there always seems to be a degree of spillage onto the forecourt try to avoid riding over these areas.

There you have it I hope this guide has been interesting and informative, I have tried to cover the main points in tyre care. If you need any further help you can always contact any of the leading tyre companies, they all operate technical help line which provide advice on tyre availability, selection, and application.

Edward (Ted) Foreman.

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