카라반 정확한 타이어 공기압 계산법

한국에서는 아직 타이어 점검에 대해서 카라반에 써 있는 압력의 90% 수준으로 넣는게 정석으로 알려져있는데요. 외국에 보니 타이어 압력에 대한 정확한 계산법이 나와 있어서 공유하고자 합니다.

 

실제로 카라반 타이어 압려은 카라반 하중에 따라 결정되어야하고 압력이 이상이 생결경우 편마모 등 일반 자동차에 비해 관리가 꽤 어려운것 같습니다. 아래 내용 참고 하셔서 내 카라반에 맞는 정확한 압력을 계산해 두시면 유용할 것 같습니다.

 

참고로 보통 우리나라 타이어의 경우 MTPLM이 6p 10p 이렇게 나온것도 있는데요. 제가 알기로는 600키로 1000키로 이니 계산에 참고 하십시요.

 

또, Bar를 PSI로 변환하는 방법은   bar * 14.5038을 곱하시면 = PSI가 됩니다.

 

 

 

외국 블로거의 내용을 가져왔습니다.  다 읽어보지는 않았고 속독 하였으니 혹 잘 못된 내용이 있다면 말씀해 주세요.

 

 

요약하면 카라반별로 각각의 정확한 타이어 압력이 필요하다고합니다. 카라반에 적혀있는 타이어 압력은 맞지 않다고 합니다. 그 이유는 카라반의 무게가 고려되지 않았다는 것입니다.

 

그럼 본인의 카라반에 맞는 정확한 타이어 압력 계산 방법을 알려 드리겠습니다.

 

 

1. 카라반의 타이어의 숫자들을 확인하십시요.

205 / 65 R 15 94 H  예를 들어 왼쪽과 같은 타이어 수치하면 맨 오른쪽 94h라는 글자에 주목하십시요.  94h는 타이어 MTPLM (Maximum Technical Permitted Laden Mass) 입니다. -타이어가 견딜수 있는 최대 하중-   각자 카라반의 수치에 대한 MTPLM은 아래 표에 있습니다.

 

2. 그 다음은 타이어 최대 공기압을 체크하십시요. 요건 타이어의 생산년도 근처에 아주 작게 써 있다고 합니다.

 

3. 이제 계산하면 됩니다.

 

싱글액슬의 경우 

타이어가   205 / 65 R 15 94 H – 이고 최대 공기압이 60 PSI라면

그리고 본인의 카라반 무게가 : 1200 Kg’s 이면

 

60 / 670 = 0.08955 (타이어최대공기압 나누기 MTPLM(최대하중)입니다.)

0.08955 x (1200 / 2) = 53.7 PSI (위에사 나온 수치 곱하기 (본인카라반 실제하중/2(싱글액슬)) 요렇게 하시면   54 PSI  가 나옵니다. 이게 본인 카라반에 맞는 수치입니다.

 

 

오창군민님과 같은 트윈액슬의 경우에는  나누기 2가 아니고 4로 하시면 되겠습니다. 아래 참고 하십시요. 그럼 같은 타이어라도 1800키로 나가는 카라반의 경우 41psi가 되겠습니다.

 

Tyre Details:  205 / 65 R 15 94 H – Maximum Inflation Pressure 60 PSI

Weight of caravan: 1800 Kg’s

60 / 670 = 0.08955 (Max Pressure for tyre divided by load rating)

0.08955 x (1800 / 4) = 40.29 PSI (inflation factor times one-quarter of the weight of the caravan)

So the correct tyre pressure is 41 PSI

 

 

 

 

원문

 

One of the most important safety aspects of towing is having the correct tyres fitted on your caravan and just as important having the tyres inflated to the correct pressure. The simple fact is caravan tyres often get overlooked and are not checked regularly. On your tow vehicle, there is usually a sticker conveniently located in the door frame or fuel filler cap reminding you of the correct tyre pressure. Unfortunately this is not always the case with all caravans.

Your Caravan Handbook usually quotes the tyre pressure for the original tyre size fitted and the caravan loaded to the MTPLM (Maximum Technical Permitted Laden Mass). As the load in your caravan can change or on older caravans, the tyre size might have changed it’s worth knowing how to calculate the correct pressure from the markings on the tyres fitted to your caravan.

You first need to be able to decipher the code on the tyre wall… this is a typical code:

205 / 65 R 15 94 H

The first part of the number is the tread width, in this case 205 mm wide. The second number is the Aspect Ratio which means in this case the tyre wall height is 65% of the width of the tread. The next letter “R” is the construction, in this case Radial, the following number “15” is the rim diameter (in inches). The next number “94” is the load rating – more of this in a moment and finally the last letter “H” is the speed rating for the tyre.

Load Rating

The load rating for the tyre can range from 60 to 130 which equates to a maximum load per tyre of between 250 Kgs to 1900 Kgs. The first thing to check is the tyres are rated for the MTPLM of your caravan, so we need to know the load index ratings.

From the table above, you will be able to cross reference the load rating code number to the actual maximum permissible load the tyre is rated for. So in our tyre data example from above, we can see that a load index of “94” means the maximum load for the tyre is 670 Kg’s. Remember that is the load for ONE TYRE… so on a single axle those two tyres could carry a maximum load of 1340 Kg’s. The recommendation from the tyre industry though is you should never exceed 90% of the tyre’s load index, so in this case the maximum axle weight would be 1251 Kg’s

The other bit of information we need to know from the tyre is the Maximum Tyre Inflation Pressure and Load. This is usually located on the side wall below the tyre data in smaller text. It will say something like “MAXIMUM LOAD 720 Kg’s MAXIMUM PRESSURE 52 PSI” it might have the pressure given in Bar.

Once you have the MTPLM of your caravan and the maximum pressure for your tyre we can now work out the correct tyre pressure.

Take the figure for the maximum pressure for the tyre and divide it by the maximum weight from the table above. Now multiply this figure by the actual load you are going to put on the tyre – so half the MTPLM for a single axle caravan or a quarter of the MTPLM for a twin axle caravan. The resulting figure should be the correct inflation pressure for each tyre.

Lets look at an example for a single axle caravan:

Tyre Details:  205 / 65 R 15 94 H – Maximum Inflation Pressure 60 PSI

Weight of caravan: 1200 Kg’s

60 / 670 = 0.08955 (Max Pressure for tyre divided by load rating)

0.08955 x (1200 / 2) = 53.7 PSI (inflation factor times half the weight of the caravan)

So the correct tyre pressure is 54 PSI

Working out for a twin axle caravan:

Tyre Details:  205 / 65 R 15 94 H – Maximum Inflation Pressure 60 PSI

Weight of caravan: 1800 Kg’s

60 / 670 = 0.08955 (Max Pressure for tyre divided by load rating)

0.08955 x (1800 / 4) = 40.29 PSI (inflation factor times one-quarter of the weight of the caravan)

So the correct tyre pressure is 41 PSI

Top Tip: As a rule of thumb, the inflation pressure of a hot tyre is usually about 4 PSI higher than when cold. If you check your tyre pressures when hot and it is more than 4 PSI higher, then the cold inflation pressure was too low. If the hot inflation pressure is less than 4 PSI difference than the cold pressure, then the cold pressure was too high.

This is derived from: “For every 10 Deg F temp change the tyre pressure changes by 1 PSI”

 

This article is meant as guidance only.  If you have any questions, or are unsure what your tyre pressures should be, your caravan manufacturer or local dealership will be able to advise you fully. If you have any doubts about the suitability or the condition of your caravan’s tyres please consult a caravan tyre specialist. Remember any tyre defects that you can be prosecuted for on your towing vehicle, also apply to your caravan tyres when towing your caravan on public roads.

Copyright © 2011 – 2016 Simon P Barlow

 

 

계산식이 입력된 카라반 타이어 공기압 계산기는 여기서 다운로드 가능합니다. 

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