I need to get some tires for my 80 Fatbob project. The stock tires (yes original stock Goodyear tires are still on the bike) are MJ90-19. There are not many tire offerings out there in this size. In a catalog it list the front tire size as a 100/90.

I have a service bulletin that states,

"Motorcycles originally equipped with MJ90-19 front tires must use 90/90-19 replacement tires. Installing a 100/90-19 tire may result in tire interference/damage causing tire failure and/or personal injury."

The service bulletin calls for the Dunlop 401.

I have the cast wheels (T19 x 2.15MT).

So what is the story? Does everyone run the stock size or have you moved up to the 100/90?

What brand of tire are you running on your old bike?

I've been eyeing the Bridgestone Spitfire. Seems to be a tried and true replacement tire for a reasonable price.

What is your opinion of the 401s?

Any other options for the value minded rider?

 

I'm not sure about the 100/90. I run a 90/90 in front and I squeezed a 140 in the back. I had to shim one side of the fender, but it works.
It's a 79 FLH. Chech out this link for some great prices! http://www.jirehcycles.com/ I went with the Maxis.

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the first number is the tread width in millimeters, it doesn't seem like 10mm is a lot but can interfere with the roll. The second number is the "aspect ratio" which means in percentage of the width. (90%) of 90mm. the plus-one has been used for years to keep a similar rolling diameter to maintain speedometer calibration. So, in a nutshell, the outer diameter of the tire mounted on the same wheel stays the same if you fit a 90/90 and a 100/80. Again, check your clearance and see if you have the extra room.

 

Here's a pic of a 100/90 tire mounted on my '83 Sportster. No clearance problems at all, but the fender's a little hard to get on and off with the wheel still on the bike. I saw a guy mount a 110/90 on a 35mm narrow glide, and the tire rubbed the fender.

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