Tech Library - Tyre Technical

A useful technical article from Cambrian Tyres the UK's largest importer and distributor of motorcycle tyres to motorcycle dealers.

 

Running tyres in


It is important to understand that running tyres in doesn’t just mean scrubbing-in the tyres surface. Scrubbing a tyres surface is only one of the reasons for running tyres in:

Not all manufacturers use releasing agents during the manufacturing process, but for those that do ,the scrubbing-in process will need to take into account the fluid residue as well as the smooth surface.These agents can also contain anti ageing preservatives and this is why the manufacturers do not remove them before shipping to their customers.

Wet weather can increase the required running-in distance by as much as three times.

Rubbing a new tyres surface with an abrasive material in order to scrub the surface in has little effect. Even very abrasive materialswill not scrub the tyre's surface sufficiently for the bike to be ridden hard right away. And besides, the tyre still needs to be seated on the wheel and the various components still need to be bedded-in against one another. Put simply, there is no short cut to running in a tyre correctly.

Following the fitting procedure, the tyre should be wiped with a dry cloth in order to ensure no residue of tyre fitting lubricant remains.

100 miles is considered a safe distance to run tyres in. When this distance has been covered, the tyre should be checked to ensure correct seating and inflation.

    
Mixing tyres

We are often asked whether tyres from different manufacturers can be mixed on the same bike. The simple answer is we don’t know.It may be that a front tyre from Bridgestone happens to work fine on a GSXR-600 with a rear tyre from Pirelli,but this is no guarantee that the same combination will work on a CBR-600RR. Neither is it a guarantee that a front tyre from Dunlop will work fine on the GSXR-600 with a rear tyre from Michelin. Manufacturers develop their tyres in matching pairs and that is the only way you will achieve optimum performance. No manufacturer tests their tyres in combination with tyres from other manufacturers.

Much of the time it is not even possible to mix tyres from one manufacturer on the same bike ,e.g.a Bridgestone BT-014 front with a Bridgestone BT020NT rear.This is because individual types of tyre have different handling characteristics and fitting mixed pairs may result in high-speed instability or other dangerous handling problems.

 

Not all tyres suit all bikes

It is not safe to assume that all tyres will suit all bikes.Just because a tyre is available in a size to fit a bike, it doesn’t automatically follow that the tyre is suitable for that bike

The most common example of this is the 190/50ZR17 bt-020,which was designed specifically for the GSX1400. In order to obtain reasonable mileage, many people are fitting this sport touring tyre to R1s, GSXR1000s, CBR900RRs etc. What they are failing to take into account is whether a tyre designed specifically for a steady handling naked bike that weighs 230kg will even work on their170kg super fast steering full on sportsbikes.

OE tyres

These days, many bikes are fitted with special original equipment (OE) versions of existing models of tyres. Much of the time it is possible to fit the “standard” version of the tyre to these bikes, but not all the time . To check whether the OE tyre is essential check the current fitment guide from the tyre manufacturer in question.

Tyre clearance

Due to centrifugal forces and in-service temperature changes, a tyres overall diameter will increase during use. It is also possible that there may be some lateral growth for the same reasons. Bias ply(crossply) and bias belted tyres will exhibit greater growth than radial tyres.

For this reason we advise that following fitment you ensure there is 4mm lateral and 14mm radial clearance to any part of the motorcycle, e.g. mudguards, forks, swing-arm, hugger etc. Bear in mind that some clearances can change with suspension movement.

 

Dynamometer testing

Dyno testing places extremely high loads in concentrated areas on motorcycle tyres. It is possible that damage, which may be invisible to the naked eye, can occur to the tyre`s construction during dyno runs. It is also possible that this damage may result in tyre failure later. Tyres that have been used for dyno testing should not then be used on the road or track.

Dyno tests should only be carried out on worn tyres which can then be discarded.

Pre-emptive Puncture Sealants

All motorcycle tyre manufacturers do not condone the use of pre-emptive puncture sealants. It is possible that they can mask secondary damage which may result in further damage being done to the tyre. They add rotational unsprung weight to the bike- this is the worst area that you could possibly add weight to a bike and it results in reduced suspension performance and slower steering response.

Puncture repairs

Avon, Bridgestone, Continental, Dunlop, Metzler and Pirelli all approve repairs to their motorcycle tyres in accordance with British standard BS AU159/f which states:


Up to and including J speed rating (62mph)2 repairs per tyre, not exceeding 6mm in diameter.


Above J speed rating and up to V speed rating (149mph) 1 repair per tyre,not exceeding 3mm diameter.


The above repairs must be restricted to the centre tread area, 25% of the nominal section width either side of the tyres centre line. Repairs must only be made using a mushroom-type plug.
Michelin is the only manufacturer that approves repairs to its W and Z speed rated tyres. All Michelin tyres are permitted to have 2 repairs per tyre with a maximum diameter of 6mm

 

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