Time for new tyres

The say­ing goes there are two things you can’t es­cape: death and taxes. But there are a few more things that fall into this cat­e­gory.

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Your car­a­van’s tyre need care too

Sooner or later you’ll in­evitably go out for din­ner with your stingy brother-in-law with the ex­pen­sive taste and at the end of the meal he’ll sug­gest you split the bill 50-50 – even though you had the fish and chips while he en­joyed ex­otic im­ported mush­rooms mar­i­nated in the Pope’s tears. It’s also in­evitable that a school’s spon­sor form will ar­rive at home ask­ing you to do­nate R1 per word for some or other read­ing Olympiad your child has to take part in.

It is as in­evitable that you’ll have to re­place your car­a­van’s tyres at some stage. This is never pleas­ant, and it al­ways feels as if it’s too ex­pen­sive. And while we un­der­stand you’re go­ing to shop around for the best value for money, it isn’t al­ways a good idea to put Hon­est Ernie’s bar­gain-of-theweek tyres on your trailer. There are a lot of things to con­sider.

LOOK AT THE MAN­U­FAC­TURER

’A good start­ing point is to look at how the man­u­fac­tur­ers de­cide on the tyres their car­a­vans are fit­ted with in the fac­tory. Clive Cox, Jur­gens Ci’s de­vel­op­ment man­ager, says the first thing they con­sider is the size of the wheel rim. “This can range be­tween 13, 14 or 15 inch, but this is more of an aes­thetic thing than any­thing else,” Clive says. “In fact, we’re mov­ing away from 13-inch rims be­cause they are so dif­fi­cult to get hold of nowa­days. At the mo­ment most of our car­a­vans are on 14-inch and our bush trail­ers on 15-inch rims.” Once the size of the rim has been es­tab­lished, they look at the tyre it­self, Clive says. “One of the most im­por­tant fac­tors we con­sider is if the tyre can carry the car­a­van’s load. And for this we look at the car­a­van’s gross ve­hi­cle mass (GVM). For this pur­pose we use the weight of the heav­i­est car­a­van in our var­i­ous ranges, for ex­am­ple the Exclusive. We then take its GVM and use the load in­dex for tyres that is in­ter­na­tion­ally recog­nised to find the ap­pro­pri­ate tyre. This then ap­plies to all the car­a­vans in that range. For ex­am­ple, if you have a sin­gle-axle car­a­van with a GVM of 2 000kg, the law states that each of the car­a­van’s tyres must be able to carry a weight of 1 000kg.”

SPEED FREAK

Clive says the sec­ond, and equally im­por­tant, con­sid­er­a­tion is the tyres’ speed limit. “In terms of our leg­is­la­tion, where we’re not al­lowed to go faster than 120km/h, we there­fore need tyres with a speed limit of at least 120km/h.

“The tyres that are avail­able in South Africa can go up to a speed of 180km/h or even faster – not that you must tow that fast. But the rea­son there’s a speed limit on tyres is re­lated to the com­po­si­tion of the rub­ber the tyre is made from.

“When you drive, heat builds up in your tyres, and they are de­vel­oped and man­u­fac­tured to en­sure the rub­ber in your tyre can stay in­tact at that par­tic­u­lar speed and heat. If you there­fore drive at 120km/h and your tyre’s speed limit is only 80km/h, you can be sure your tyre is go­ing to burst sooner rather than later. It is ex­tremely im­por­tant to take note of the tyre’s speed limit, be­cause it can lead to ma­jor prob­lem if you make a mis­take.”

WIDER WIDEST

Once the car­ry­ing ca­pac­ity and speed limit have been sorted out, they de­cide on the width of the tire. “We look at 185mm, 195mm, 205mm or what­ever the case is. But this is less im­por­tant than the load in­dex and speed limit of the tyres,” Clive says.

They then find out which tyres that ad­here to th­ese spec­i­fi­ca­tions are avail­able on the mar­ket. “For our car­a­vans we use com­mer­cial tyres. Th­ese are sim­i­lar to those used on minibus taxis, specif­i­cally be­cause of those tyres’ car­ry­ing ca­pac­ity. We don’t fit or­di­nary sedan mo­tor ve­hi­cle tyres on our car­a­vans.

“We look at what is avail­able on the mar­ket from the var­i­ous sup­pli­ers. For un­der­stand­able rea­sons we do not buy tyres on the re­tail mar­ket, but rather from peo­ple who im­port them or di­rectly from the fac­tory. So we def­i­nitely also con­sider the price of the tyre and try to es­tab­lish sav­ings for our clients.”

THE SPEC­I­FI­CA­TIONS

All the in­for­ma­tion you need about your car­a­van’s tyres, is on the side of the tyre. As an ex­am­ple, let’s use the tyre the Sprite Tourer SW, with a GVM of 1 450 kg, is fit­ted with in the fac­tory – a 215/80 R 15 110 S tyre.

The 215 is the width of the tyre in mil­lime­tre.

The 80 is the tyre’s pro­file, mean­ing the re­la­tion be­tween the height of the tyre’s side op­posed to its width. This is given as a per­cent­age.

The R is for ra­dian, which ba­si­cally means there’s a low en­force­ment that runs across the tread.

The 15 means the tyre was de­vel­oped to fit onto a 15-inch rim.

The 110 is the tyre’s load in­dex.

Ac­cord­ing to the in­dex a tyre with a

110 in­dex can carry a weight of 1 060 kg.

This means the car­ry­ing ca­pac­ity of the

two tyres on the car­a­van is 2 120 kg.

The S is the tyre’s speed limit, mean­ing

it was made to travel up to a speed

of 180 km/h.

NEW TREADS

If it’s time to buy new tyres for your car­a­van, Clive rec­om­mends you stay as close to the spec­i­fi­ca­tions of the tyres the car­a­van orig­i­nally had.

But when is it time to re­place them? Ac­cord­ing to the Road Traf­fic Act your tyres are le­gal if there is at least 1 mm tread left on the tyre. The tread needs to be even across the width and cir­cum­fer­ence of the tyres, and the pat­tern must still be clearly vis­i­ble. But Clive warns that tyres also ex­pire, even if they still have more than enough tread left. “That rub­ber com­po­si­tion of your tire has an ex­piry date and this is usu­ally about five years af­ter the man­u­fac­tur­ing date,” he says. The date your tyre was man­u­fac­tured is also on the side. In the case of the Tourer SW’S tyre we used as an ex­am­ple, it’s the num­ber 4313. This means the tyre was man­u­fac­ture in the 43rd week of 2013, which means it will ex­pire around mid Oc­to­ber 2018.

“You of­ten hear about guys with older car­a­vans they haven’t used for a while, who go camp­ing and then a tire bursts af­ter trav­el­ling a short dis­tance. This is be­cause the tyre has ex­pired, even though the tread was still good,” Clive says. “The thing you need to re­mem­ber about car­a­van tyres is that they never re­ally reach their life ex­pectancy in terms of kilo­me­tres trav­elled. It’s not like with your car where you’ll travel 60 000-80 000 km with your tyres. In the same time frame your car­a­van might just travel 15 000 km.

But you still need to re­place them af­ter five years.”

KEEP A LOW PRO­FILE

But what to do if you want to soup up your car­a­van with brand-new 17-inch rims and a set of low-pro­file tyres?

You can and may, says Clive, if the rim and the tyre have the load in­dex to carry your car­a­van’s GVM. Re­mem­ber, this is di­vided by two – so if you want to put new tyres on your Tourer SW, they must each be able to carry a weight of at least 725 kg. You must also en­sure the di­am­e­ter of the rim and the tyre are the same as the stan­dard tyre the car­a­van was is­sued with.

The rea­son for this is your car­a­van’s brakes. They are set ac­cord­ing to the spec­i­fi­ca­tions of the stan­dard rim and tyre, and if you sur­pass this, you’re ask­ing for trou­ble. So never fit a larger rim while still us­ing the same pro­file tyre as the stan­dard. Al­ways con­sider the over­all di­am­e­ter of the com­bi­na­tion.

Clive sug­gests you chat to your lo­cal dealer and tell him about your plans to find out if they will work.

An­other thing you need to con­sider when you want to fit new rims, is the po­si­tion of

the cen­tre point (where the wheel bolts go through). Clive says it must be the same as the car­a­van’s orig­i­nal rim.

“If the cen­tre point is fur­ther away from the un­der­car­riage than the orig­i­nal, your tyre could be too close to the car­a­van. And if it is too close to the un­der­car­riage your tyre will stick out be­yond the wheel arch. And nei­ther of th­ese sit­u­a­tions are good for your car­a­van or tyres.”

KEEP THE WHEELS TURN­ING

Clive rec­om­mends you ro­tate your car­a­van’s wheels at least once a month if it is sta­tion­ary for long pe­ri­ods at home. Tyres that are sta­tion­ary for long pe­ri­ods get smooth un­der­neath – this is what causes the knock­ing sound when you tow for the first time in a long while. In terms of tyre pres­sure says Clive you must be guided by the rec­om­men­da­tion above your car­a­van’s wheel arch. “For road trail­ers it’s usu­ally around 2,5 bar, de­pend­ing on how heavy the load is. The heav­ier the trailer, the closer to their max­i­mum tyre pres­sure you need to pump them.”

DID YOU KNOW?

Ev­ery­one knows the earth takes 365¼ days to re­volve around the sun. But did you know dur­ing that year the earth moves through space at 108 000km/h on an or­bit of 838 mil­lion kilo­me­tres?

We didn’t think so. Here are some other equa­tions about your wheels to think about.

Round and round The av­er­age car­a­van tyre Jur­gens Ci uses, is a 195/80 R14 tyre. The tyre has a di­am­e­ter of 66,7cm and cir­cum­fer­ence of 2,095m. So if you head to a week­end camp­ing site that’s 100 km away, each tyre has com­pleted about 95 000 rev­o­lu­tions by the time you get back home. If some­one from Pre­to­ria goes camp­ing at Yz­er­fontein on the West Coast and takes the short­est route (about 1 500km), the wheels would each have turned about 1,4 mil­lion times by the time you see the Union Build­ings again!!

Choose the in­side track. A 2014 Toy­ota For­tuner’s wheel track is 1,54m and it uses 265/65 R17 tyres. The tyres have a di­am­e­ter of 77,6cm and a cir­cum­fer­ence of 2,44m. If you drove around the block along four straight roads and 90o turns the left-hand tyres have ac­tu­ally turned much more – and there­fore trav­elled a longer dis­tance – than those on the right-hand side. ( We use the front tyres as the ex­am­ple, be­cause the back tyres fol­low a short­cut be­hind the front tyres around a turn.) If you the­o­ret­i­cally go around the cor­ner with the right-hand tyre a me­tre from the cor­ner, the right-hand tyre has trav­elled 1,57m on that cor­ner and the left­hand one 3,99m. So if you there­fore go around all four cor­ners the left-hand tyres have trav­elled 15,96 m on the cor­ners and the oth­ers 6,28m. if you con­sider the dis­tance of all four cor­ners, the For­tuner’s out­side front tyre has trav­elled just more than dou­ble the dis­tance once you’ve gone around the block.

Keep up, dude. When you tow a Ven­ter Elite 6 trailer, the wheels com­plete many more rev­o­lu­tions over a spe­cific dis­tance than those of a tow­ing ve­hi­cle such as the 2014 Ford Ever­est. The Ven­ter has 155/80 R13 tyres (di­am­e­ter 57,8cm and cir­cum­fer­ence 1,816m) and the Ever­est 245/70 R16 tyres (di­am­e­ter 74,9cm and cir­cum­fer­ence 2,353m). If you’ve trav­elled 100 km, the Ven­ter’s wheels have turned 55 000 times as op­posed to the Ever­est’s 42 000 times. For ev­ery time the Ever­est’s wheel makes one revo­lu­tion the Ven­ter’s wheel had to turn 1,3 times to cover the same dis­tance. There­fore the Ven­ter’s wheels make 30% more rev­o­lu­tions than those of the Ever­est. So if you travel 100km/h and a dis­tance of 1,67km in a minute, the Ever­est’s wheels turn at 708 r.p.m. and the Ven­ter’s at 918 r.p.m. If you want to get even more tech­ni­cal: The to­tal move­ment en­ergy – due to the move­ment at 100km/h and the wheel ro­ta­tion – is about 7 700 Joules. Now imag­ine the tyre gets de­tached from the wheel hub and runs along a stretch of road straight up into the sky. It will only come to a stand­still at a height of 26 m – that is about 7 storeys!

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