Tire Sizes

[imported_n/a]

I'm stuck in the past with 3.50 and 4.00 and 4.50 tire sizes.  That was easy.  

What is the modern equivalent sizing that matches up to our old and trusted American way?

Glenn


 

[rob w]

Hello Glenn, Tire buying 101. The first dimension is the width, the second dimension after the slash is the heighth of the tire. The dimensions given are relative to the manufacturer, so a 110 width Michelin may not be exactly the same as a 110 Dunlop. The metric dimensions can be calculated the same way you would convert any metric to inches. Say it says 100/100 x 18.(the magic number is 25.4, because there are 25.4mm's in one inch) 100 divided by 25.4 = 3.937 or 3 15/16's inches. A 110 = 4.330" or apx. 4 3/8". Because you can not really see a tire for what it is in the showroom. It is best to look at someones tire of the same manufacturer and size mounted on a rim. I have all the manufacturer's web site addresse's, I will give them to you in a hour or so, I've got to go put Henry to bed. See ya in a few. Bob

 

[rob w]

Glenn, back again. I know you know how to search, what I meant to say was there is a web site I was looking at recently that is easy to compare all makes, sizes available, weights, and prices in one place. It is called //www.tiresunlimited.com ,not that I've ever purchased anything there, just that it can help shopping. When your looking for a smaller tire for a Penton 100 or 125, that kind of narrows the search down a little. I don't think Michelin makes a 100mm width. I would like to know if there's a special paint to use, to paint the lettering on the side walls white. Hope I could help. Bob.

 

[imported_n/a]

Thanks, Bob.  But math was never my strong point.  I've got a 110/100 Bridgestone.  Should I use it on a Jackpiner or 250/400?

Glenn

 

[OUCWBOY]

Glenn,
The 110/100 is almost a 4.50. I think it would be better used on a 250/400 bike.

[LINDEMAN]

Glenn,this subject is like 2-stroke oil.Lots of opinions.I would not use a 110 width on anything but open bikes.A 250 penton has about 34 HP.Thats the same as a modern 125.100/100's work great on 175 and 250's.You want the rear to slide before the front for proper handling.The Kenda 4.10x18 works good on the 100/125's and there cheap.A 4.10 is a tiny bit wider than a 350 but more importantly the heigth is right.

 

[imported_n/a]

Thanks, guys, I appreciate the education.  It used to be so easy to go to my Penton dealer and pick up a new Metzeler in good old-fashioned American sizes!

Glenn

 

[Dwight Rudder]

There is some very good info going here. The only problem is that you have to look at tyres on a one to one basis. Michelin seems to be the worst at overrateing their sizing.
a 120/100 X 18 is ( should be ) a huge 4.50/5.00 width tire. Too big for most vintage bikes.
Pirelli MT16 are very good tires and last year still came in inch sizes but this year they changed to metric. They come in a big 4.50X18 ( 120/100 X 18 ) and a 4.00 X 18 ( now called a 110/100 X 18 ,........should be a 100/100 but they thought Americans would buy a 110/100 more. ).
Weaker 100s and 125s need a 350X18 and strong 125s and 175s need a 4.10 X 18 ( 3.75 X 18 ).
Cheng Shin and Kenda make Metzler copies.
C755 and the K257D series tires
Cheng Shin makes a Barum copy also called the C183A series.
Cher'o,
Dwight

7 time ISDT / E medalist
7 time National Enduro Class Champion.

[imported_n/a]

Thanks, Dwight.  But now my head really hurts!
I guess, to narrow things down, how does the sizing run on Michelins and Dunlops (big, small, just right)?  

Glenn


 

[Dwight Rudder]

Glenn, Personally I don't consider modern tire for vintage bikes. I don't think they look nor handle properly in my opinion on these machines.
I would stick with brands we know match the machines. Pirelli would have to be considered the closest to the Metzeler tires we primarily ran in the 70's. I highly recomend them and like them so much I use them on my modern machines even today.
Cher'o,
Dwight

7 time ISDT / E medalist
7 time National Enduro Class Champion.

[rickf22]

I think additional confusion is caused by not only switching from Inch to metric tire sizing, but also the metric tire sizing scheme changed recently. I am told the difference is: It used to be that the overall tire width was measured, including the knobs. Now the tire width is measured to the "base" and the knobs are extra.

Here is a link to a tire size conversion chart. Notice there are two columns for Metric sizes. One is th eold, the other the new. Unfortunately, they are not labeled old and new, but you can tell by the relative sizes. The new ratings should look smaller than the old.
http://www.650motorcycles.com/TireChart.html