[Neal]

I bought some round 4" LED tail/brake/turn lights for a custom installation. What size hole do I need to drill in the housings for the lights and grommets to fit perfectly? The lights are listed as 4", but they measure more than that outside diameter, and they have to fit in the grommet in the hole in the housing. Have any of you ever measured the mounting hole? Thanks.

[Jake514]

Just get a thin piece of scrap plastic or wood and experiment with your hole saw or jig saw until you find the proper size.

[rj1939]

It has been over 12 years since I cut any holes for them, but it seems like I used a four inch hole saw.

A trailer place will have or be able to get light boxes with holes already cut (which you could measure for sure)

[Neal]

Originally Posted by Jake514

Just get a thin piece of scrap plastic or wood and experiment with your hole saw or jig saw until you find the proper size.

I need to know what size hole saw to order. I want these holes nice and round, so I won't be using my jig saw. I have a drill press and a mill/drill vise so as long as I get the right size hole saw it should be relatively easy.

[Neal]

Originally Posted by rj1939

It has been over 12 years since I cut any holes for them, but it seems like I used a four inch hole saw.

A trailer place will have or be able to get light boxes with holes already cut (which you could measure for sure)

The outside diameter of the lights measures about 1.240" to 1.290", depending where it's measured. The plastic front cover(I'll call it) has a lip on it. So I don't see them going into a 4" hole. 4 1/4" or 4 3/8" maybe. My brother is a truck driver and he going to check a trailer at work tomorrow if he gets called in. If not, I try the local trailer place next time i get to the city. Thanks.

[Neal]

This morning I did some more internet searching and measuring one of my lights in the grommet and it seems the correct hole size is 4 1/2 inches. Thanks for the replies.