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.