Advice on motorcycle tyres from Manufactuers;
Do new tyres need running in?
Yes, all tyres need a period of running in.
You should be very careful initially, as new tyres may not give full grip, particularly if the road is wet or cold. You should not use harsh acceleration or braking or maintain a sustained high speed for the first 100 miles or so. Then you should visually inspect your tyres and check the cold inflation pressures before using high power, harsh braking or high speed.
Can I make my tyres last longer?
To some extent – Yes.
Riders with a smooth style, who avoid harsh use of the controls, achieve longer tyre life.
Running tyres in properly helps avoid the development of unusual or heavy abrasion patterns, which can increase wear rate, occurring early in the tyre’s life.
Regular tyre maintenance, particularly keeping tyres correctly inflated, also helps extend tyre life.
Suspension settings which are, "too hard" will increase tyre wear (and reduce grip).
Can I change the tyre sizes fitted to my bike?
A great deal of effort from both the tyre and bike manufacturers goes into the selection of the best tyre and rim combination for each model as it is developed. The sizes recommended for your bike are those which work best with the chassis set up to provide you with the best combination of grip, handling and stability. If you choose to run sizes other than those recommended you will lose performance in one or more of these areas, potentially creating problems with handling and/or high speed stability.
Can I mix tyres from different manufacturers?
This is basically not a good idea. All the tyre manufacturers spend a great deal of time and money testing their own products, either to develop new tyres or to try existing tyres on new bikes. There is no way we could test all the possible combinations of different manufacturers tyres, it would just be too big a job. Therefore it really is best to stick with the same manufacturer front and rear, then should you have a problem you will at least have someone you can contact for help.
Can my puncture be repaired?
The answer to this is rather like a politicians speech; Yes and No.
The legal regulations covering tyres are the "Construction and Use Regulations 1986". Under these regulations we are required, as riders, to maintain our tyres in a serviceable condition i.e. Correctly inflated, within the minimum tread depth requirement and free from cuts, splits and other structural damage. Within the regulations there is no mention of puncture repairs.
So far, so good.
BUT – the British Standards Institute have produced BS au159/f covering repairs to motor vehicle tyres. The standard limits the type and amount of damage that should be repaired in tyres for all vehicles.
The limits for puncture repairs are: -
Speed Rating
No of Repairs
Below "J"(up to 100kph)
2 repairs up to 6mm diameter after
preparation; repair patches must not overlap.
Above "J" up to and Including "V".
(100-240kph)
1 repair up to 6 mm diameter after Preparation
Above "V" including "W" & "Z"
(above 240kph)
No Repairs
In simple terms this means that the standard permits one repair in Scooter and most Cross Ply tyres but no repairs in ZR radials.
Whilst this particular British Standard is not a legal requirement, unlike the standards for helmets and visors, it is still likely to be seen as the test of "prudence" or "reasonableness" in a court case. This being the case, it is possible that an insurer could decline a claim where a tyre has been repaired outside these limits. As you would have contravened the clause in all policy documents which requires you to maintain your machine in a "roadworthy" condition.
There is also the issue of the penetrating object causing further damage to the casing construction where the tyre cords have been broken, or contaminated; and the possibility, with tubeless tyres, that the tyre has been run under inflated for some time. Either of these factors could mean that even if the tyre was repaired, the repair could fail in service.
Consequently for road safety and insurance validity reasons it is our recommendation that tyres outside the above limits are not repaired.
In any event: tyres should only be repaired by a competent dealer
What is the minimum tread depth for a motorcycle tyre?
The minimum tread depth regulations are to be found in "Construction and Use Regulations 1986" (revised in 1992 for cars). These state that for a motorcycle over 50cc you must have a minimum pattern depth of 1.0mm around the full circumference of the tyre for the central 3/4 of its width and the remainder of the original pattern must be visible.
As an interesting aside, wet performance deteriorates markedly when the tyre is more than 1/2 worn.
Can I use Racing (or Moto Cross) tyres on the Road?
The answer to this can be found in the "Construction and Use Regulations 1986". The regulations require us to use "tyres fit for the purpose". As Racing and Moto Cross tyres have "Not For Highway Use" (sometimes abbreviated to "NHS") engraved on their sidewalls this clearly indicates that they are NOT to be used on the road.
Why?
Racing tyres are of a very lightweight design with a very thin tread and none of the normal road use features, such as protective sidewall compound, included. This, along with their nominal design life of only 1 hour or so, makes them very vulnerable to damage from road hazards (potholes etc) creating a potentially dangerous situation.
Moto Cross tyres have a very open block type tread pattern with very tall blocks; this tends to make them unstable on the road. Also the compounds used in Moto Cross tyres have a very high tear resistance, meaning that they have poor grip on a hard, wet surface.
What do all the numbers on the sidewall mean?
There are a number of tyre size marking systems in use.
The most common system is the "millimetric" system. I am sure that everyone will have seen sizes which look like this: -
120/70ZR17 (58W) TL Sportmax D207F
120 is the overall width of the tyre measured in Millimetres, when fitted on the correct width rim.
70 is the "aspect ratio" simply the ratio of the tyre’s height to its width, expressed as a percentage.
So this tyre is: 120mm wide x 70% aspect ratio = 84mm high.
Z indicates a tyre with a sustained maximum speed rating of over 240kph(150mph).
R indicates "Radial Ply" construction.
17 indicates the rim diameter.
58 is the "Load Index" this indicates that the tyre can carry a maximum load of 236kgs when inflated to it’s maximum scheduled pressure.
W is the actual continuous sustained maximum rated speed of the tyre, in this case 270kph(168mph). The tyre can actually achieve higher maximum speeds than this figure but in order to do so it cannot carry its full load potential. This is why even lightweight high-speed machines have fairly large tyres.
TL indicates that the tyre has a tubeless construction. (Tyres intended for use with inner tubes are marked "Tube Type")
Sportmax D207F is the commercial product description.
Tyres for older "Classic" bikes use the "Imperial" marking system and look like this: -
3.50-18
In this case the tyre is 3.50" inches wide and has an aspect ratio of 100, so its height is the same as its width.
There is a further set of "Imperial" sizes using lower aspect ratios these look like: -
4.10-19 for 90% aspect ratio tyres
Or
4.25/85-18 for 85% aspect ratio tyres.
The third system in regular use is the "Alpha-Numeric" system originating from the USA. Tyres with these markings are now almost exclusively fitted to Harley Davidson machines.
The markings look like this: -
MT90-16
M indicates a motorcycle tyre
T indicates how wide the tyre is from a table of nominal overall widths.
90 is still the aspect ratio
16 is the rim diameter.
There are a number of other numbers on the sidewalls of motorcycle tyres that show which international standards the tyre conforms to.
The two most common of these are the "E" mark, which is required by UK law, and the American DOT marking. As a rider you don’t really need to think about these as the manufacturers, distributors and retailers have a legal responsability to ensure that only correctly marked tyres are distributed and sold in the UK.
Ensuring safety of purchase
Tyre suppliers commit an offence if they sell tyres that do not comply with current government legislation. All tyres manufactured have markings on their sidewall which indicate if they comply with current legislation.
It is illegal for tyre suppliers to supply passenger car tyres which do not observe the following criteria:
* Does not have an 'E' mark showing that it complies with the load and speed requirements of ECE regulations
* From the 1st January, (with certain exemptions ,i.e. tyres for pre-1949 vehicles and for off-road and competition use) new car and light trailer tyres (including 'VR' and 'ZR' radials) must be ECE OR EU approved and 'E' or 'e' marked respectively. (And from 1st June 1997 for Motorcycle tyres)
* From the 1st January 1995 it has been illegal for any person to supply re-treaded tyres unless they are marked to indicate compliance with BS AU144e
* It is also illegal for anyone to supply a part-worn tyre which does not comply with legal requirements outlined on this site and which does not have tread grooves of at least 2mm deep
N.B. To the best of our knowledge, the information given here is correct at the time of posting (June 2001) but the law is subject to change from time to time. Please consult a solicitor if you need specific legal advice.