86 K75C with 18" rear wheel - anybody tried Radials?

[Gubro30]

I did read the sticky in the lieberry but couldn't find infos about bikes with an 18" rear wheel. If they work what size should I buy?

Currently running stock sized Pilot Activ.

Thanks!

[Motorandy123]

I found this in my archives;

"If you like to ride hard then I recommend trying some "off-size" radials. I run a 110/80-18 BT-023 on the 2.5x18 front wheel of my K75.  I run a 140/80-17 Avon Azaro on a 3.0x17 rear wheel.  The handling is excellent, MUCH better than a K75 on bias ply tires."

[frankenduck]

That's on a 3" wide wheel.  Due to the rear drum brake, he can't just swap in a 3" wheel.

You'd need to find a radial that'll work on a 2.75x18 rear wheel.  I don't know of any but that doesn't mean they don't exist. :dunno

[Gubro30]

Thanks Duck, that was exactly my concern.

At least with the dimensions I can call the tire companies directly and find out by myself.

Front wheel (100/90/18) shouldn't be a problem I guess?

[frankenduck]

Don't know of any front radials with a 90 aspect ratio.  Plenty of good tires out there in a 110/80-18 though:  Michelin PR2 or Bridgestone BT-023 is what I run.

[Motorandy123]

Oops I didn't realize the stock rears are 2.75" not 3.0". I'll have to delete that out of the archives.
So why can't you use a 140 on a 2.75" rim? The chart on this page (at bottom) says it can be used...

https://www.denniskirk.com/help_center/tire-sizes.jsp#width_table

[Scott_]

Oops I didn't realize the stock rears are 2.75" not 3.0". I'll have to delete that out of the archives.
So why can't you use a 140 on a 2.75" rim? The chart on this page (at bottom) says it can be used...

https://www.denniskirk.com/help_center/tire-sizes.jsp#width_table

Randy, not ALL of the K-bikes have rear disk brakes. The early ones had a drum brake and abviously a skinnier rear rim to go with.

[frankenduck]

The early naked K75s and all K75Cs had a drum brake.

Fixt. :yes

[Scott_]

The early naked K75s and all K75Cs had a drum brake.

Fixt. :yes

Thanks. :2thumbup:

[Gubro30]

Thanks all!

So what size should I go with to keep the same OD?

[frankenduck]

I did some poking around and all I could find in a 140-18 was Shinko with an aspect ratio of 60 which, according to a tire size calculator I tried would be 7% smaller - which I think is too much.

I think the "best" thing to do to run radials would be to swap in a FD with a disc brake so you could run a 3x17 rear wheel with a 140/80-17 Avon Azaro.

Or, even easier, sell your bike and buy one that already has a r3ear disc.