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TECHNICAL MOTOBRICK WRENCHING In Remembrance of Inge K. => The Motobrick Workshop => Topic started by: Gubro30 on August 24, 2012, 08:51:00 AM

Title: 86 K75C with 18" rear wheel - anybody tried Radials?
Post by: Gubro30 on August 24, 2012, 08:51:00 AM
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!
Title: Re: 86 K75C with 18" rear wheel - anybody tried Radials?
Post by: Motorandy123 on August 24, 2012, 02:30:42 PM
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."
Title: Re: 86 K75C with 18" rear wheel - anybody tried Radials?
Post by: frankenduck on August 24, 2012, 02:48:21 PM
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
Title: 86 K75C with 18" rear wheel - anybody tried Radials?
Post by: Gubro30 on August 24, 2012, 07:21:22 PM
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?
Title: Re: 86 K75C with 18" rear wheel - anybody tried Radials?
Post by: frankenduck on August 24, 2012, 07:28:43 PM
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.
Title: Re: 86 K75C with 18" rear wheel - anybody tried Radials?
Post by: Motorandy123 on August 25, 2012, 06:57:09 AM
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 (https://www.denniskirk.com/help_center/tire-sizes.jsp#width_table)
Title: Re: 86 K75C with 18" rear wheel - anybody tried Radials?
Post by: Scott_ on August 25, 2012, 08:30:43 AM
Quote from: Motorandy123 on August 25, 2012, 06:57:09 AM
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 (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.
Title: Re: 86 K75C with 18" rear wheel - anybody tried Radials?
Post by: frankenduck on August 25, 2012, 08:49:37 AM
Quote from: Scott_ on August 25, 2012, 08:30:43 AM
The early naked K75s and all K75Cs had a drum brake.

Fixt. :yes
Title: Re: 86 K75C with 18" rear wheel - anybody tried Radials?
Post by: Scott_ on August 25, 2012, 09:49:44 AM
Quote from: frankenduck on August 25, 2012, 08:49:37 AM
Quote from: Scott_ on August 25, 2012, 08:30:43 AM
The early naked K75s and all K75Cs had a drum brake.

Fixt. :yes

Thanks. :2thumbup:
Title: Re: 86 K75C with 18" rear wheel - anybody tried Radials?
Post by: Gubro30 on August 25, 2012, 10:25:17 AM
Thanks all!

So what size should I go with to keep the same OD?
Title: Re: 86 K75C with 18" rear wheel - anybody tried Radials?
Post by: frankenduck on August 25, 2012, 11:58:24 AM
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.