2022 Drake Smith - Please do not use or reproduce this elsewhere.  Feel free to link to it though.

Perforated & Expanded

Stainless Steel Grilles

Perforated Expanded


I like the appearance of perforated or expanded stainless steel so I've added it to several of my K bikes.

There are two types of the expanded stainless steel, regular and flattened. I get the flattened for radiator grilles because it is easier to keep clean.

Regular Flattened



K75 Standard or K75C:

K100 Standard w/ K75S Belly Pan:

K1100LT Side Vent:

K1100RS Side Vent:

K1100RS Radiator & Belly Pan:


GAUGE(Thickness): I use 20 gauge (0.0375") for the perforated stainless and 16 gauge (0.0625") for the expanded stainless. 0.0xxx inches sounds flimsy but they are actually quite sturdy.

PERFORATED: Circular perforated stainless steel has two measurements, hole diameter and center to center spacing.

Each configuration has its own open area percentage. Some examples for the K bikes pictured above:








K75 Std.




K1100RS Sides




K1100LT, K100, K75S





EXPANDED: Expanded stainless steel is measured by SWD (Short Width of Diamond) which is the height of each opening. I use 1/2" SWD.



There are Internet etailers that sell custom sized sheets of stainless like CUT2SIZE METALS Online Metals and others. However, there are many sellers on Ebay that can be a better deal if you find a piece that is the correct size.

For example, in May of 2021 for the K75 Standard/C radiator  grille above I paid $18.85 with free shipping for a 10.75"x14.5" piece of 20 gauge perforated stainless with 3/16" holes on 1/4" centers.

Search links:

Ebay search for perforated stainless

Ebay search for expanded stainless



TABLE SAW: I cut the sheets to size on a table saw with s 10" cut off wheel, like this DW8005 made by DeWALT:

GRINDER: Another option would be to use a grinder with a cut off wheel for metals.


REPLACING: If I'm replacing an existing grille then I just use the factory mounting. Like I did for this K75 grille:


ADDING: For the K1100RS I added perforated stainless to the side vents and expanded stainless to the belly pan where there was no factory mounting. What I did there was use the table saw with a cut off wheel to shape some pieces of 1" thick HDPE. I then drilled and tapped some M6 holes in them and used JB Weld to glue them to the interior of the  fairing piece. Here's a K1100RS belly pan:

(Click on the image below to enlarge it in a new tab.)


Thermal Impact:

RADIATOR COOLING: Although the perforated stainless lets less air pass by the radiator I've had no cooling issues on any of the Ks on which I've installed perforated stainless grilles, even if hot weather. The expanded stainless lets lots of air pass through.

THIGH BURN: The side vents on the K1100LT don't seem to make a difference with respect to K bike thigh burn. The K1100RS might be a little warmer than usual in the thigh burn department but I've never measured it and it doesn't bother me.

Other Options:

If you want to do something fancier than circular perforated or expanded stainless steel then are other types of sheet metal than you can use.

A few examples:



2022 Drake Smith - Please do not use or reproduce this elsewhere.  Feel free to link to it though.