新呔放前定放後好? Should you place the new tire to front or rear?

Scroll to the bottom for English version

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好耐都未出post, 最近忙於趕project, 就黎完成, 不如出下post 又講下車呔既野.

平時大家換新呔都係將新呔放前, 其實我自己都冇好研究呢樣野, 直至有個客同我講, 佢想要新呔放後面. 話我知因為新呔放後, 安全過放前面 (睇左個video 之後). 之後我就開始研究下呢樣野, 到底放前定放後好呢?

先俾大家睇下, 唔同既車呔制做商對於車呔放前定放後好既實驗. (可以睇下面, 綜合所講既野)

1. 米芝蓮做既實驗
http://www.michelinman.com/US/en/safe-driving/tire-safety/mixing-tires.html

2. 錦湖話後呔應該係新呔
http://kumhotyre.co.uk/kumho-news/should-you-fit-new-tyres-to-the-front-or-rear/


3. 台灣其中一個研究 (理論同錦湖一樣)
https://www.youtube.com/watch?v=FYNU2Gtig58

5. 放前定放後都有唔同意見
https://www.youtube.com/watch?v=6AyXpQBfr9c

綜合上面講既野, 新呔放後面既原因

A. 米芝蓮話實驗做出, 放新呔係前面, 如果開得太快令到甩尾, 部車會失控

B. 錦湖話, 因為understeer (轉向不足) 同 oversteer (轉向過度)會出現, 正常控制轉彎其實好少出現, 所以將新呔放係後面, 前呔(即舊的既呔) 咬力不大, 發生轉向不足時, 會易的轉番入黎. 如果前呔咬力大, 轉彎會更貼地, 就比較難轉番入黎 (唔知咁會唔會令大家明白的).

同樣, 發生轉向過度, 後尾會向前沖. 但新呔咬力比較大, 所以當剎車時, 後呔冇咁易失去咬力向前沖

(而大部分既車都係前輪驅動, 制做商都將呢的車整到較易轉向不足)

轉向不足同轉向過度既原因我就唔詳細講啦, 下次再講

新呔放前面既原因

A. 台灣被訪問既個位, 話因為放係前呔先會較易控制車既左右

睇左咁多樣野之後. 自己既感覺係

1. 米芝蓮既實驗唔係好說服到點解後呔要裝新呔. 因為做個實驗兩次, 兩次都係唔同既環境條件做. (車速同控制既條件). 第一次新呔放後就好普通咁渣個圈, 第二次新呔放前, 就叫人係咁加速, 成個條件都唔同晒. 

如果新呔放係後呔, 其實前呔都有機會因咬加不足而失控. 用方向盤想轉去其他方向, 其實都可能救唔到, 因為前呔咬唔到地, 轉唔到你想去既個一邊 

2. 錦湖既講法相信係令人較易明白同合理. 佢提出當發生呢兩者既關係時, 後呔係新呔會冇咁易出事. 講到好多車都會較左會轉向不足, 呢個會較易說服到人

3. 新呔放前呔, 的確係會轉向較易控制, 相信呢個大家都認同, 因為大家都會將新呔放前呔.

總結

因為大家都身處係香港, 香港一般, 唔係高速公路, 通常都只係去到60公里/小時. 高速就100 - 120公里/小時. 趕時間既就去到100(非高速), 180 - 200 公里/小時, 相信都會有的人都會咁做的.

最好換晒4條新呔

其實呢個係廢話. 不過想帶出個點係, 渣到咁上下, 最後將前呔換番去後面, 後呔換番上黎, 咁條呔會耐用左. (因前呔會蝕得快過後呔). 到時4條都可以一齊換

如果換2條既話, 因為另外個2條可能換左冇耐

平時如果你開得慢, 新呔放係後呔可能會較岩你. 

反正都開得唔係好快, 好似我咁. 轉向不足(渣得太快轉彎會出現)既出現會好好好底 . 轉向過度既情況反而都有機會發生, 因為尾車太輕, 轉彎就有可能沖前

但係如果另外個2條呔其實而經好舊, 如用左3年以上, 但又覺得深紋唔想換, 咁我又會建議番新呔放前. 因為舊呔開始有機會老化, 爆呔機會大左.

平時如果你開得好好好快(其他快過我既, 我都覺得好好好快 XD ,  新呔放係前呔可能會較岩你.

因為開車快更加需要前呔既控制. 因為甩尾既情況都好少見到. (當然都有機會) 

所以開得快既, 就最好換晒4條呔. 正所謂, 工欲善其事，必先利其器, 頭文字D - Project D , 每場比賽都會換新呔嫁. :)))))

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It's being some time since I posted something out when I am still busy with project. The project is progressing still okay, maybe it's time to post something out.

Drivers normally put new tyres in front, and I don't really research more on this kind of thing, until when a customer told me that he wants to put the new tyres at the back, and told me that putting the new tyres at the back is safer than putting them in front (after watching a video). Perhaps it's time for me to research more about it.

Let's have a look on those videos (I have concluded the points below)

1. Michelin Tyre Experiment
http://www.michelinman.com/US/en/safe-driving/tire-safety/mixing-tires.html

2. Kumho research on new tyres to put on the rear
http://kumhotyre.co.uk/kumho-news/should-you-fit-new-tyres-to-the-front-or-rear/


3. Taiwan research (same theory as kumho)
https://www.youtube.com/watch?v=FYNU2Gtig58

5. Another taiwan news video
https://www.youtube.com/watch?v=6AyXpQBfr9c

To conclude the above why putting new tyres at the rear

A. Michelin experiment showed that putting new tyre at the front will cause oversterring / spinning when you are driving too fast while turning 

B. Kumho mentions that understeering and oversteering may occur and normal handling to steer (most of the time) will not happen. If you put new tyre at the rear, when understeering happens, you can steer back to the track (when front tyre does not meet maximium grip). If the front tyre is new tyre and meeting the maximium grip, it won't be easy to turn back to the track.

Likewise, in the cause of oversteering, rear tyre have a tendency to push to the front. If you put new tyres at the rear, you will have better trip at the rear. Hence, the rear (new) tyre will not lose grip easily when braking 

Furthermore, most of the cars are FWD, manufacturer setup the car to make understeering easily

To conclude putting new tyre in front 

A. The technicians (in Taiwan) said that driver can have better control of the car

My opinions on the video and research

1. Michelin experiment is not persuasive enough as both experiment were not in the same driving condition (speed and control). Because the driver is asked to keep accelerating in the second round of testing, when new tyre is put in front.

If I assume the same condition, putting new tyre at the rear may cause the car to crash as well as the front tyre does not have enough grip .

2. Kumho research is easier to understand and more persuasive. 

3. It's understatement that putting new tyre in front will have better control, as most of us (drivers like you) normally put new tyres in front.

Conclusion

We are in Hong Kong after all. Driver may speed up until 60km/hr (not in high way), or up to 100 - 120 km/hr (highway). Some may be in a hurry, and speed up to 180 - 200 km/hr

Change all tyres to new one

So you won't have to think much about the old ones. And the main point I want to bring out is, it's better to have your car tyres swap from front to rear, and rear to front after driving sometime, (as your front tyre will rear off faster than your rear). In this case, tyres can be used longer, and you can have all your 4 tyres changed to a new one at the same time

If you still want to change 2 tyres because the other 2 just changed not long ago

Putting new tyre at the rear may suit you if you are driving at normal speed like below 70km/h (not at high way)

Since you are not driving fast like me, the probability of understeering occurs is low. On the flip side, probability of oversteering is higher than understeering due to lighter weight at the rear.

Putting new tyre in front may suit you if you are driving fast.

Driving fast require better grip and control. Though the occur of oversteering is uncommon (in HK). And of course it still have a chance to occur

As a result, it's still better to change all your tires to new one if you are driving fast. 

As the adages goes, if you want to do better things, you will require better equipment. Just like Initial D - Project D, they change all new tyres in every race. :)))))))))))

換呔 要岩番個呔鈴尺寸 Important to change the appropriate tyre size

English Version is at the bottom part of the page

最近有個朋友黎左換呔, 分享左佢係九龍某間呔鋪換呔既經驗.

個位師傅, (應該係冇現貨係到) 就換晒 4條呔都係同一尺寸 (225 40 R18). 其實尾呔係應該換寬身的既呔(因為呔鈴唔同), 可能個位師傅都唔為而, 就換左4條同一尺寸.

換左窄身既呔之後, 後呔變成咁

 換呔前 (圖一)

呔鈴明顯地外露出黎. 呔鈴會因為咁而更易受到撞擊. 個friend 話, 平時隔幾日都要打多次氣, 睇黎唔止係呔鈴會受傷既問題. 包唔住成個呔鈴令到有gap 位係到, 引致每日少部分漏氣. 

 換呔前 (圖二)

再放大的睇睇

如果自己覺得好似唔對路既話, 我係唔介意大家可以whatsapp 張相俾我睇睇, 同大家研究下 :D 

又抽下水, 呢位師傅賣出4條 225/40 R18 Dunlop 既價係 $1500/條.

我賣比個朋友 同一size 都少於 $1000/條.  $1500 呢個價相信同出面其他九龍區既鋪頭差唔多, 九龍區換呔似終都係會貴番的既, 例如食野都會比新界貴.

如果換番岩既尺寸, 心都好的, 但係, 師傅換左2條唔岩既........ (no eye sees, 原諒佢吧, 佢都可能睇錯je)

幫個friend 換番岩既後呔尺寸, 即時靚番晒.

 換呔後 (圖一)

感覺完全唔同晒. fit 番岩呔鈴, 冇咁易整傷

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English Version

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A friend came recently to change  tyres, and shared his experience at a Kowloon tyre retail store.

The technician (probably have no inventory for the size) suggested to change all 4 tyres with the same size. (225 40 R18). The rear tyre should change a longer width but the technician did not realize that, and change all 4 tyres to be the same.

A shorter width rear tyre caused a little gap between the rim and the tyre sidewall as followed 

 Before changing tyre (pic 1)

The side of the rim protruded. Without the tyre sidewall covering, the rim is prone to rock and stone "attack" on the road. My friend said that he needs to pump in air again every few days. That implies, the air is leaking out in between the gap.

 Before changing (pic 2)

Zoom in to have a better look.

If you feel something is wrong with your tyre, do feel free to contact me, whatsapp the picture, and discuss about it :D

(Grabbing a little limelight here) The technicians sells 4 tyres (size 225/40 R18) Dunlop for $1500/piece. And I sold less than $1,000/piece. Perhaps that's the price difference between Kowloon area and New Territories area. Just like having a meal in Kowloon is more expensive than in New Territories.

After changing the appropriate size,

 換呔後 (圖一)

The look is surely different from before. The size fits the rim.

打呔氣 (省兩邊 / 中間無紋) tyre air pressure - part iii (tyre thread wear off)

經過多番既研究, (為左避免好似part ii 咁 學錯左野 >< ),  就係平時有朋友都會問, 點解條呔會 "省一邊" / "省兩邊" 或者係中間無紋 (好少見).

先講後兩者, 車呔 "省兩邊" 同 "中間無紋". 因為對於打呔氣有關聯的.


1. "中間無紋"
即代表你打得太多呔氣入去 (over-inflation). 呔既中間因太多氣, 比兩邊突出. 行走時只有中間既紋貼落地.

2. "省兩邊"
原因係打得太少呔氣 (under-inflation). 行走時兩邊既呔紋比中間突出同貼地.
(睇下圖就了解到啦)

車呔兩邊比較硬身o的, 打少左氣(並有重量係上面壓下時), 中間就會凹左少去少少, 變左呔既兩邊較貼地. 相反, 多左呔氣, 迫左中間凸出, 行車時中間會貼地左.

大家得閒可以留意下自己既車呔有冇以上情況,  可以令車呔行得更長久

如果跟足車廠既標準呔氣, 都發現省兩邊既話, 不妨試下打多少少, 因為車廠始終都係做車唔係做呔, 都可能唔知咁多個牌子(同新型號)既車呔既特性同物料既質地


English version
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After further studying (to avoid the same mistake I made in the previous post), to ascertain the reasons why we have tire wear in the middle or both side.

These two situations are related to the tyre pressure

1. tire wear in the middle
It indicates you have pumped in too much air in the tyre, resulting in the middle tread surface area sticking the ground more than both side.

2. tire wear on both side
It implies under-inflation. Tire tread on both side sticks on the ground more but not the middle tread.

Due to the stronger tyre sidewall, the middle tread will cave in under the situation of under inflation (when there is weight). The inner and outer side of the tyre's surface area touch the ground more than middle, hence, wearing both side easily. The same goes for over inflation.

Check your tire for the above situation will help your tyres to run for longer time.

If you have already followed the car manufacturers recommended tyre pressure, and still discover both side tire wear, try pumping in a little more air. Car manufacturers do not manufacture tyre afterall. Tyres characteristic may have changed over time with it's improvement and ingredient.

打呔氣 tyre air pressure - part ii

除左跟番汽車標示上既呔氣, 另一樣野就係睇下打的咩氣入去.

其實我地呔鋪都係打空氣入去 (先聲明左先) , 同油站個的打呔氣既氣都一樣.

有的呔鋪 / 車行就打氮氣 (Nitrogen) 入去.

兩者分別在於, 打空氣入去, 呔既氣溫上升時, 空氣因氣溫上升而脹左. 令到你既呔氣都會大左(壓力). 

最好打氣既標準, 就係行完車睇下呔氣升左幾多. 如果本身要打32psi, 原先有打左32psi 的話, 已行完車之後升到上35psi 既話, 咁可能你會想放番的氣到29psi / 30 psi. 行車時就會行番32psi 啦.
(再睇番個post 發現原來我打錯, 一定係最近太熱, [幫自己搵緊excuses ><] ) 最好打氣既標準, 應該係條呔唔熱(正常溫度)既時候, 打番個個氣壓. 如果標籤寫32psi 的話, (而條呔係正常溫度下), 打番32psi.


而再詳細的更標準既係, 唔同溫度應該打番唔同既汽壓, 如夏天, 就會打32psi, 冬天打少的咁之類既野, 但係避免咁煩, 都係未開車之前打番個標準氣壓, 或者係開車後隔一陣先再打. (如果趕時間等唔到條呔cool down 番, 直接打32psi 或打多少少)

打32psi 即係最底既呔氣壓, 都係車廠建議的. 但係我又覺得奇怪, 又冇講到係用氮氣做標準, 定係普通既空氣做標準. 係咪因為太複雜, advise 人地打最底既呔氣壓?

(有少少緩衝都冇問題既)

其實冇乜人check 到咁嚴既, 只要行得好就冇乜所謂. 不過氣壓太多既話除左部車會彈下咁之外 都有機會"省"兩邊呔的 (下次再講)

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To be more professional, it's important to check what type of gas is pumped into the tyre.

Actually our store pump normal gas into the tyre  (For your information) , the same as gases used in the petrol station.

For some tyre store / car maintenance company, they pump in Nitrogen

The difference is that Nitrogen is not easily affected by the temperature, but normal gas's kinetic energy increases when temperature increases. When tyre temperature increases, air pressure in the tyre increases as well if you are using normal gas. 

The best way of ensuring the standard of air pressure, is to check how much tyre pressure increases after you started your car and drive for some time. If you are supposed to have 32psi for your tyre, and you have already pumped in 32psi at the beginning, the tyre pressure increases to 35 psi after driving, then you may want to release some of the gas in the tyre to 29 / 30psi. 

(Revising the post and found out that I had written wrongly about the tyre pressure. It must be the heat!! [ Finding excuses for myself >< ]) The label on the car indicates the tyre pressure in cold temperature. If the label states 32psi, then it's recommended to pump in 32psi under normal temperature (which I assume is room temperature and pressure)

There is actually a complex matrix to tell drivers how much tyre pressure should be pumped in under different temperature. E.g. pumping in 32psi during summer, and a little more psi during winter.

To avoid complication, simply pump in the recommended tyre pressure on the label when the tyre is not hot would be good enough for most of the drivers. (If you don't have the time to wait for the tyre to cool down, just pump in 32 psi, or a little more would be fine)

In sum, 32 psi (in this example) is the minimum tyre pressure you should pump in. Car manufacturer did not mention the best tyre pressure when the car tyre has "warmed up", and did not state whether to use Nitrogen as standard, or normal air as standard. Perhaps it's too complicated to involve in tyre?

(a little buffer should be fine for your driving)

Actually we don't really have to check so serious that we have to follow the rules as long as it does not affect our driving. However, if you pump in too much air, not only if you feel your car is "jumping" kind of feel, your tyre tread may worn off easily at two side (which I will talk about in the next part)

打呔氣 Tyre Air Pressure - part I

平時有客問, 打幾多氣落條呔先岩呢? 我發現冇乜人會同大家講, 其實係司機位有個標籤, 個到有寫到要打幾多先係最岩部車既呔氣既.

好似呢部 Honda Civic 1.8 i-vtec 就寫住 前呔係220 (kPa), 或者係 2.2kgf/cm square 或者係 32psi.
通常會用到既單位都係 psi, 係油站應該會見到kPa 或者 psi 的. 所以跟住呢個打呔氣實冇死.
唔係架架車都寫psi 的, 有的只係寫左kPa, 所以如果大家睇慣左psi 既話, 就要自己轉番做psi 啦.

如果自己部車本身有sensor 既, 不妨都可以用到呢個做指標, 如果明明打足佢寫既psi 都話有問題, 咁就一係個sensor 問題, 一係就用個個儀器有問題了. 反正就係可以再用另一個儀器再睇, narrow down 到可能真係個sensor 問題既話, 就會係一係set 錯psi, 一係就有壞左.

另外標籤有寫上原裝呔既尺寸, 如果買車既時候見到條呔同呢個標籤有出入, 就一定係改過size 的了.

English Version
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How much air pressure is considered sufficient for your tyre? Well, I discovered that not much people will tell you about the label at your driver's seat door. Actually, the label will tell you what's the best air pressure for your car.

In the case of Honda Civic 1.8 i-vtec below, it stated 220 (kPa) or 2.2kgf/cm square , or 32psi. Normally we used psi as unit to pump air, and you should find both kPa and psi units when you pump air at the petrol station. Following the label shown, you will definitely know how much air should pump in.

Not all cars label are created equal (of course). Therefore, if your find your the label only show one unit, (and you are not accustomed to that unit), you will have to convert the unit for yourself.

You can also check your car tyre sensor (if you have one) by using the label air pressure as standard. Since it's the air pressure suggested by the manufacturer. If you have pumped the air pressure standard suggested and yet the sensor still shows there is something wrong with your tyre, then it's either there's fault in the sensor, or the equipment that you used to pump air. Either way, you should be able to find out for yourself.

The label also stated the original tyre size for your car. Therefore, if you find the tyre size is different, well, you know what it means.

呔氣指標蓋 Tire Pressure Indicator

之前有睇過有個蓋cap 住係條呔既喉咀到. 好似下面呢個咁

綠色: 代表呔夠氣

紅色: 代表呔唔夠氣, 要打氣

睇落好似簡單又易用, 一開始都而為佢仲勁過而家個的用手機睇呔條既儀器, 但發現其實唔係.

問左個賣家, 佢話, 入面其實set 死個呔氣指標. (不過冇問到set 左幾大指標) e.g. 廠set 左係36 psi 既呔氣, 但係你平時打氣係32psi 既話, 你用左佢既話, 就永遠都係出紅色, 而舊野係自己冇得改. 

如果你打算買既話, 或者己經買左既話,  就要問下佢地係set 左咩指標先好買啦, 或者黎我地到, 我幫你睇個舊野係set 左幾多psi.

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Below tire cap, I believe, is not uncommon to every driver. It's used to track tire pressure.

Green: indicates sufficient tire pressure

Red: indicates insufficient tire pressure, you need to pump more air

It looks simple and easy to use, and sort of better than those other devices that used smartphone to monitor the air pressure. But it turns out it's not really the case. The seller told me that, the pressure indicator is fixed at the cap (though I didn't ask what's the pressure set). Let's say if it's set at 36 psi, and you normally pump air to 32 psi, it will always show red light. You cannot change it, nor the seller.

If you are planning to purchase, or you already had it, you may want to check out the pressure fixed at the cap. (you are welcome to come to my store and I can find it out for you too :D )

粉嶺高速公路既朋友要小心駕駛 Becareful when driving along Fanling Highway

好誇張, 連續有兩位朋友係粉嶺高速公路, 起緊天橋既附近既路段爆呔, 先分享下第一個既爆呔相

第一張睇落去好似冇乜野, 好似只係普通中釘, 但係一折開, 就見到成支叉插入去咁, 救唔番. 諗住以為只係中釘爆呔, 點知搞到咁

第二位朋友, 仲可怕. 佢形容一開始聽到車底 "bon" 一聲, 以為車底撞到野, 點知係條呔爆左. 拖車黎到, 折黎一睇, 呔鈴都穿埋, 都唔知俾的咩搞到咁

所以, 經過粉嶺高速都係小心留意下路面

(English version)

Unbelievable. It's probably the only words that I can think of, when two customers (not on the same day) came with their tyres unable to patch. If you are driving along the Fanling Highway, please be extra careful. 

The first looks like some sharp metal object puncture. 

When we took out the tyre, the object was so sharp that it puncture like a fork towards the rim. Unable to patch.

The other customer described his experience, when he drove along the Fanling highway, he heard a "bomb" sound under the car. He thought something big hit the car but it turns out it's his tyre that went out of air. When he came to our store and took out the tyre, then he saw there is a big hole at the rim. What the? What kind of things could pierce through the rim?

Well, just be extra careful when you are driving at the fanling highway. 

私家車呔 vs 輕型貨車呔

最近掛住寫code, 終於係個月前寫好左一個簡單既online shopping.

因為仲未有太多既資料, 所以你有可能搵唔到你既車呔size. 如果真係搵唔到既話, 打黎搵我地叫我地報下價.

And, 除左私家車, 都有輕型貨車架, 所以你地可以禁入去望一望睇下車呔係咪for 私家車定係 for 輕型貨車. (呢個係我做得唔係咁好, 會遲少少改進番, 等大家易的去睇)

在係呢到講多的有關兩者之分

因為有的車呔既size , e.g. 205/65 R16, 可以係私家車呔, 都可以係輕型貨車呔

(如圖下,  第一個牌子HiFly 係for 輕型貨車, 第二個牌子Falken 係for 私家車呔)

所以有時的呔鋪問番轉頭話, 係輕型貨車定係私家車, 唔想報錯價.

要知個條呔係私家車定輕型貨車, 係我地個網禁個張相, 或 "詳細" 就可以見到車呔規格既左下角係私家車, 定輕型貨車.

其實咁平時上網搵, 仲有另一樣可以好快知, 就係睇條呔既 show 出黎既size.

部分輕型貨車呔size 會有: C (或其他字母, 通常都係C), 係Rim size 後面, 如上圖HiFly 就有

205/65 R16C , 

另外就係睇車呔size 既 loading index. 輕型貨車呔既loading 會有兩個指標 -> 107/105T

107 代表當一條呔放係左, 另一條放係右, 既重量等級, 105代表當兩條呔放係同一左, 或同一右既重量等級. 

如果個網有的咩唔好, 告知小弟等我可以improve 下