The Aspect Ratio of a tire is the ratio of the height of the tire's cross-section to its width. We could classify the same aspect ratio tires into different series such as the 65”. Tire section width is the width of the tire measured in millimeters from sidewall to sidewall, which the number on the tire is marking as the bead seat width. The range of the rim is not included in the Tire section width. The speed rating on a tire is a designation indicating the tire’s design speed capability. That is, the fastest speed a tire can handle before it does not perform as designed.
*ZR indicates the speed range, speed rating, maxima speed km/hr
Maximum Load is the most weight the tire is designed to carry. The strengthen tire could posses a higher maximum load compared to the same specs regular tire, and the maximum load rate is different on the tire wall as well.
LI: Loading Capacity
62 265 74 375 86 530 98 750 110 1060
63 272 75 387 87 545 99 775 111 1090
64 280 76 400 88 560 100 800 112 1120
65 290 77 412 89 580 101 825 113 1150
66 300 78 425 90 600 102 850 114 1180
67 307 79 437 91 615 103 875 115 1215
68 315 80 450 92 630 104 900 116 1250
69 325 81 462 93 650 105 925 117 1285
70 335 82 475 94 670 106 950 118 1320
71 345 83 487 95 690 107 975 119 1360
72 355 84 500 96 710 108 1000 120 1400
73 365 85 515 97 730 109 1030 121 1450
(The Specs are derived from Bridgestone Offical Website)
Then let’s talk about the specs of the rim.
The front wheel of the M109R is 3.5JX18, 3.5J means 3.5 inch wide times 18 inch in diameter.
The rear wheel of the M109R is 8.5JX18, 8.5 inch wide times 18 inch in diameter.
When you upgrade to the 300 mm tire, you should use 10J, which is ten inches, 254 cm wide rim with 30 cm wide tire.
Please take a look at the specs chart attached, the MT is the J rate, every tire has its compatible width, normally a rim could only resist two inch upgrade, for example, 8.5J is suppose to fit on a 240 to 250, 260 is the maxima. Even if you forcefully put on a 280, it is like fitting in an oversize shoe with tiny feet, and the tire just could not reach it’s supposedly width, and thus you should put a 9J or 9.5J on a 280. When the tire couldn’t stretched properly it will starting to deform, and not only couldn’t it reach 280mm in width, the tire wall would be too tilt to perform adequate support to the bike when turning into a corner. We could discuss it some other time.
After reviewing the description above, let me tell you about my experience regarding speed limit. I could calculate speed difference in advance if only I have the perimeter of the tire. The deal is that the 140/70H 18 is a normal nylon cord tire, instead of the advance steel cord tire. The speed limit for H is approximately 210km/h, and guess what would be like when you exceed that limit..?
When I reached 200km/hr, my front tire started to deform, the huge centrifugal force caused the tire rim to transform from circular to cone sphere. In other words, the tire wall and structure couldn’t withstand the centrifugal force and deform. What’s worse, the bigger tire robbed against the fender and started to burn up. The interior of the fender not only being worn down pretty hard but also the melt down plastic was stuck on the deformed front fender. No wonder, other riders behind me smelled the unbearable burnt and saw the smoke coming out of my bike’s front end. Fortunately, I lowered down my speed in time so that the tire didn’t explode; otherwise I wouldn’t be able to type this experience now. Therefore, make sure you buy the reasonable spec tires including speeding rate and maxima load, and most importantly the manufacture date for fear that the tire expired and oxidized. VH is the speed rating/MT is the J rate/2.5-3.5 is the compatable J rate/5.1 inch is the width/ 638 is the perimeter in cm/ 25.1 is the perimeter in inches The rim width is the J rate, and the diameter is the ordinary tire size we normally refer to. Semi-hot melt tire, comfy, and more durable than the METEZELER tire. The import tires we mainly use is hard on the tire wall and extremely durable, which is suitable during a sporty ride.