Buying used or partworn tyres
Before you buy Part-Worn (used/secondhand) tyres or fit them to your car, please have the tyre checked properly.
Even if you drive like a nun, you don’t know if the person you are buying the used tyres from hasn’t hit every pothole and been speed testing on the highway?
What am I looking for?
Firstly, consider why you are considering buying a used tyre. Good grip is needed, as the braking performance and steering response will be affected.
The more tread, the better. The grooves in the tyre tread are designed to clear water from the wet road surface in order for the tyre to make contact with the road. The deeper the tread, the more water can be dispersed from the road, meaning the less likely you are to find yourself aquaplaning (skidding). The minimum legal tread depth in RSA is 1mm, so make sure the tyre have at least 3mm of tread left for you to get some mileage out of the tyres.
Aquaplaning happens when a layer of water builds up between the tarmac and the tyre and causes your brakes and steering to stop working. If this happens, all the ABS and electronics will be of no help at all – you are simply going to skid in a straight line.
On a part-worn tyre, the tread will not be as deep as on a new tyre, thus - less grip in wet conditions. The legal limit of 1.6 mm is in fact very low, and should be seen as an absolute minimum rather than the point at which a tyre should be changed. All tyres have tread wear indicators that are little raised rubber areas inside the tyre sipes (grooves). If you can see them, then the tyre manufacturer is trying to tell you they are past their sell-by date.
Tyres that have been damaged often shows itself by the tread loosen from the carcass of the tyre.
It is very wise to change your tyres every three years (or 60, 000 kilometers). There are people who try to do a 100 000 kilometers on a set of tyres that might think this a little excessive…but you might be thankful if you manage to stop before you bump into another vehicle or when you have enough grip to swerve around a child running into the road.
The tyre carcass is the composite structure of the tyre in the manufacturing process, with the layers of rubber coated plies made of polyester, nylon, rayon, or steel, that comprises the resistant structure of the tyre upon which the tread, belts, bead, and sidewall are laid.
The carcass is surprisingly easy to damage (punctures, potholes, etc.) but that type of damage is often hard to detect. Obvious signs are bubbles or areas where the tread is uneven or lifted.
Damage can be seen better looking at the inside of the tyre, which is only possible if the tyre taken off the rim of the wheel. The best is to grab the sides of the demounted tyre and pull them apart so that you can see the inside. There should be no rubber powder or granules inside, and the pattern inside should be uniform. While holding the sidewalls apart, press the tread of the tyre down onto the ground or a (not sharp!) corner. By rotating the tyre, look for any changes in pattern or shape, in order to ensure there is no damage.
Besides providing lateral stability, the tyre sidewall prevents air from escaping and keeps the body plies protected. Some tyre sidewalls may contain extra components that serve to increase lateral stability.
The sidewall adds extra ‘cushion’ to the car’s suspension, and the higher the sidewall profile, the more comfortable the ride will be. Thus low-profile tyres give a harder ride. The perception that low profile tyres give better steering response, is definitely true on the racing track or a smooth surface, but the trade off is that low-profile tyres tend to follow the camber of the road and ‘tramline’ (steer off-course) much more than ones with a higher profile. Low-profile tyres give more feedback from the road.
Sidewalls are the part of the tyre that gets pinched against kerbs, or even cut, so that is where you should look for damage. Any deformations in the sidewall (inside or outside) that are noticeable indicate that the tyre is dangerous and worn-out and should not be used. Damage to the sidewall cannot be repaired.
Another thing to look for is whether the writing on the sidewall has been rubbed/ scuffed off the sidewall. This is a sign that the tyre has been chafed against corners either due to extreme cornering speeds or due to under-inflation. If a tyre has been driving under-inflated, then there is a greater chance that the internal structure has been compromised and that tread separation from carcass may occur. Note that it is harder to tell visually whether low-profile tyres are under-inflated.
If there is any cracking or perishing, it shows that the tyre is old and therefore not to be used or bought. This is sometimes only obvious when it is fitted to a wheel, inflated and when the car is standing on it. Don’t be afraid to waste a fiver and ask the garage to take it off again if you see that the tyre is knackered. A tyre should not be older than 5 years.
The tyre bead is the inner circle of the tyre; the part of the tyre that connects the tyre to the rim, and holds the entire wheel together. Specific machinery is necessary to properly mount tyres onto a set of wheels or rims. You should carefully inspect the bead, running your finger around the inside and outside as well as performing a visual check. Any noticeable damage at all, means that the tyre could pop off the rim causing a rapid deflation or separation and thus evolve in an unwanted blow-out. Note that bead damage may not always be visible! A blow-out is most likely to happen when you are cornering or braking, giving you excitement in all the wrong ways.
This is going a bit beyond the remit of this guide, but is worth a quick mention. Tyres are, simply put, made from rubber compounds that can be harder or softer. Hard compound tyres last forever but give you less road grip (especially in cold conditions) and soft ones give more grip, but get very hot at speed and wear faster.
Don’t forget that if you buy part worn tyres you still need somebody to fit them for you and balance the wheels. It is highly recommended that you have this done at a reputable tyre dealer.
All passenger car and commercial vehicle tyres must conform to the SABS compulsory specifications:-
VC 8056 Compulsory specifications for pneumatic tyres for passenger cars and their trailers, and/or
VC 8059 Compulsory specifications for pneumatic tyres for commercial vehicles and their trailers