Is 10" Measurement for Dexter Electric Trailer Brakes the Inner Diameter of Drum

Updated 01/23/2026 | Published 01/19/2026

Question:

Weird questions: is 10inch the inner diameter of the drums? Im trying to engineer a retrofit to a Volkswagen Vanagon being cut down to a single axle trailer. Id like to use the original VW bearings, hubs, and drums which have an inner diameter of 252 mm 9.921 in. and retrofit an electric backing plate and brake assembly. I have access to a machine shop, so I can make things work together if the starting point meets a certain spec. Are technical drawings of these or other brake assemblies available? Obviously, any such retrofit will void the warranty. Im okay with that.

asked by: Christopher

Expert Reply:

Hi Christopher; for the Dexter Electric Trailer Brakes # K23-472-473-00 the 10" diameter is the inner diameter of the drum the brakes fit. The 1-1/2" measurement is the width of the brake shoes. We don't have technical drawings of the brakes available, you might be able to get them from Dexter but I don't think I've ever asked so I can't say for sure.

What are you building this trailer to do?

expert reply by: Robin H

Dexter Electric Trailer Brakes
(click to enlarge)

Christopher

1/20/2026

The trailer will be dual-purpose: a light camper setup that can also accommodate a single motorcycle or several bicycles. A "guest house" when traveling with friends, as my camper van is set up to only sleep two. Pretty much a fun project to repurpose a very nice rust-free Vanagon that was totaled in a front impact. I think the trailer will weigh somewhere in the 900-1,200 lb. range empty, and my motorcycle is around 400 lbs. My favorite destinations are hilly, so adding electric brakes seems prudent. My other thought was to activate the original hydraulic drum brakes with a surge setup, but that's less appealing.

Robin H.

1/21/2026

@Christopher that sounds like a great project, and your weight estimates are definitely in the range where brakes make sense, especially in hilly areas. Just keep in mind that electric trailer brakes are very sensitive to drum diameter, so being slightly under 10" can cause fit and performance issues.

Dan

1/21/2026

@Christopher I purchased the Dexter 10" X 1.5" brakes as replacements on my TT. They worked perfectly. These should work well for your project but be sure your drums can safely be machined out to 10". Set it up with a good electric trailer brake controller with good connections all the way through the circuit plus a break away switch. Look up specs and install processes directly from Dexter. They were helpful but a little guarded with their information.

Christopher

1/23/2026

VW factory specs look like 20-40 thousands under 10" -Dia 252mm (9.921") -Max after machining: 253mm (9.960") -Wear limit: 253.5mm (9.980")