@MEHMETALİ
Öncelikle kendiniz de araştırabilirsiniz, ilk başta ben de garipsemiştim. Fakat arazi kullanımı ve yol kullanımı farklı oluyor. Arazide ön tekerin önemi çok daha fazla
Mixing/Matching Tyres
Most bikes come with identical tyres front and rear. This is all right for general use, but if you want to optimize your bike, you should consider using different tyres front and rear. The front and rear tyres have different loadings and different requirements.
Narrower Front, Wider Rear
If lightness is the primary goal, tyre width/weight is limited by the risk of pinch cut flats, a.k.a. "snake bites." Since there is more weight carried on the rear tyre, you can get away with a slightly narrower tyre in front than you can in back.
Wider Front, Narrower Rear
A wider front tyre makes sense in many applications, however, when handling and ride comfort are considered. A wider tyre will generally provide better cornering traction than a narrower one, assuming appropriate inflation pressure.
A wider tyre also provides superior shock absorbency. I personally prefer a slightly wider tyre in front, since I suffer from some wrist discomfort on occasion.
Off-Road Issues
Bikes that are used some of the time on loose surfaces often benefit from a wider front tyre, with a fairly aggressive tread, coupled with a somewhat narrower, smoother rear tyre.
The wide, knobby front tyre will provide the all-important front wheel traction. Front-wheel skidding almost always leads to a crash. For riding on soft surfaces, such as sand or mud, a wide front tyre is essential. If the front tyre sinks in and gets bogged down, you're stuck. If the front tyre rolls through a soft patch OK, you can generally power the rear through to follow it.
The narrower, smoother rear tyre will have lower rolling resistance. Since most of the weight is carried by the rear tyre, rolling resistance is more important on the rear than the front. If the rear tyre slips, in most cases the worst that will happen is that you'll have to get off and walk.
This is a great idea that developed out of BMX racing.
Some mountain-bike tyres come in matched sets, with different tread front/rear. The front tyres tend to have the knobs set up more or less parallel to the direction of travel, for improved lateral grip and better steering control. The rears tend to have transverse knobs for driving/braking traction.
kaynak : (link)
Yani Sheldown Brown abimiz diyor ki; Hafiflik ön plandaysa, ön tekere binen yük az olduğundan ön teker daha ince olabilir. Sürüş konforu ve yol tutuşu önemliyse Arkayı daha kalın kullanmanın avantajlı olduğunu, kalın lastiği daha düşük basınçta kullanabileceğimizden özellikle dönüşlerde yol tutuşunun artacağını belirtmiş. ve öndeki kalın lastiğin titreşimleri daha fazla emdiğini söylüyor. Ben de önceki mesajımda yazmıştım yuvarlanma direncini düşürmek için yapıyolar diye, bu yazıda da belirtilmiş, arka tekere daha fazla yük bindiğinden daha ince, daha düz lastik kullanımı yuvarlanma direncini azaltıyor. Bi de demiş ki ön teker kayarsa işiniz zor

ama arka kaysa en kötü yürürsünüz.
NOT: tamamını çevirmeye üşendim biraz yarım yamalak oldu, affola.