2021 Drake Smith - Please do not use or reproduce this elsewhere.  Feel free to link to it though.

K Bike Tires

Short Version

You can and should run radial tires on all Ks. They ride and handle noticeably better than bias ply tires.

Type

Wheel

Tire Size

"Best" Tire

Y-Spoke

K75, K100

2.5x18 Front

110/80-18

 

Continental

Road

Attack

3

2.75x17 Rear

130/80-17

3-Spoke Narrow

K75, K100, K1100LT

2.5x18 Front

110/80-18

Bridgestone

T31 or T32

 

3x17 Rear

150/70-17

3-Spoke Wide

K100RS4V, K1,

K1100RS

3.5x17 Front

120/70-17

4.5x18 Rear

160/60-18

Tire Pressure

 

Normal Load

Loaded or 2-Up

Front

34 psi

36 psi

Rear

40 psi

42 psi

If you weigh a lot or ride 2-up frequently on a K100RS4V, K1 or K1100 then you should consider getting the GT version of whatever tires you purchase. GT tires are made for heavier loading.

If your wheels don't have them already then it is a good idea to switch from the original rubber valve stems to metal valve stems when installing new tires.

Long Version

K75s, K100s and the K1100LT all came from the factory with bias ply tires. Ugh. You can run all of those bikes on radials now and you'll find a very noticeable improvement in handling. If you like to ride hard then you'll really notice the improvement as the bike will feel much more "planted" and confidence inspiring.

"Off-sized" tires: The term off-sized refers to tires that are not the same size as the original tires that came on the bike and are specified in the owner's manual. Some of the tires listed below are off-sized. Some people don't approve of using off-sized tires but my proof that the tires below work well on K bikes is that I've put a few hundred thousand miles on them and never had a get-off. The only tire issues I've had have been flats caused by punctures, something that would happen with any size tire.

The following are my current tire preferences for the various wheels on K Bikes.

Original K75/K100 Y-Spoke Wheels (2.5x18 front, 2.75x17 rear)

There's only one radial tire that I know of for the Y-spoke wheels.

Continental Road Attack 3

  • Front: 110/80-18

  • Rear: 130/80-17

Comparison of stock tire sizes to off-sized:

Tire

Size

Tire

Radius

Tire

Circumference

%

Change

Front

BMW OEM

100/90-18

12.54"

78.81"

 

Road Attack 3

110/80-18

12.46"

78.32"

-0.63%

Rear

BMW OEM

130/90-17

13.11"

82.35"

 

Road Attack 3

130/80-17

12.59"

79.13"

-3.91%

This lowers the front by about 0.1" and rear about 0.5" so it may be a little more difficult to get the bike up on the center stand.

Narrow 3-Spoke Wheels (2.5x18 front, 3x17 rear) - K75, K100, K1100LT

  • Front: Bridgestone T31 or T32 110/80-18

  • Rear: Bridgestone T31 or T32 150/70-17

Comparison of stock tire size to off-sized:

Tire

Size

Tire

Radius

Tire

Circumference

%

Change

Front (only K75/K100, not K1100LT)

BMW OEM

100/90-18

12.54"

78.81"

 

Off

Sized

110/80-18

12.46"

78.32"

-0.63%

Rear

BMW OEM

140/80-17

12.91"

81.11"

 

Off

Sized

150/70-17

12.63"

79.38"

-2.13%

On K75s and K100s this lowers the front by about 0.1" and the rear by about 0.3". On a K1100LT is lowers the rear by about 0.3". This makes it slightly harder to get the bike on the center stand.

Wide 3-Spoke Wheels (3.5x17 front, 4.5x18 rear) - K100RS4V, K1, K1100RS

  • Front: Bridgestone T31 or T32 120/70-17

  • Rear: Bridgestone T31 or T32 160/60-18

Michelin Pilot Road tires are also very good tires but cost more than the Bridgestones for the same performance and wear. (IMO)

Both Bridgestone and Michelin make GT versions of their tires which you should consider buying if you weigh a lot or ride 2-up frequently.

I had to get some Pirelli Angel GT tires installed when out touring and the front tire seemed to wander when riding on warm tire snakes. I don't think they are an unsafe tire but I found that annoying so I would not recommend them.

Note that it is possible to run the wider RS 3-spoke wheel on a K1100LT (what I do) and it will "bolt right up." The 160/60-18 tire on the RS wheel is only 1% smaller in radius/circumference than a stock 140/80-17 tire. 

Metal Valve Stems

If your wheels still have rubber valves stems then a tire change is a great time to swap in some safer, more reliable metal valve stems. I use BikeMaster 151402 valve stems.

2021 Drake Smith - Please do not use or reproduce this elsewhere.  Feel free to link to it though.