How to Know What Weight Rating is Needed When Converting from Drum to Disc Brakes

Updated 05/06/2019 | Published 05/03/2019

Products Featured in This Question

Kodiak Disc Brake Kit - 8" Rotor/Hub - 5 on 4-1/2 - Dacromet - 3,500 lbs

(13)

$444.90

Replacement Trailer Hub Bearing - L44649

(2147)

$22.82

Replacement Trailer Hub Bearing - L68149

(2147)

$18.41

Grease Seal - Double Lip - ID 1.719" / OD 2.565" - for 3,500-lb Axles - Qty 2

(2774)

$6.23

Dexter Zinc-Plated Brake Actuator - Disc - 2-5/16" Ball - Bolt On - 8,000 lbs

(30)

$471.21

Question:

drum to disk brake conversion . . .Greetings. Heres one that stumped a local dealership. I have a dual axle camper 28Ft with drum brakes and its rated at 7600 gross, my first camper, and this is all a learning curve. My question is this. If I convert to disk will I need to switch all four or the front~rear? Ive poked around for specs but cant find what Im looking for. Ive been back and forth a few times with the v*/2uv formula and not having all the exact variables doesnt help much. So far I have only seen kits rated for 7k and under and 10k. How is it calculated? 10k total divided by four wheels? It was suggested to me that switching to a new pre-fabd axle may be more cost effective although that doesnt make sense to me If it aint broke dont fix it . . . Thanks in advance . . .

asked by: John F

Expert Reply:

Good questions and there is a lot here so let's start with the simplest thing, the weight rating. Trailer brakes are rated based on their axle; for example, the Kodiak Disc Brake Kit # K2HR35D-8 is designed for a 3,500 lb axle and a tandem axle trailer with a pair of 3,500 lb axles would need two of these, so the first thing to know is the weight rating of your axles.

Then to get the correct fit, since you are replacing a hub and drum, you are going to need a disc brake kit with a hub and rotor. To do that you are going to need to know what bearings your current hub has. You will need to take apart your current hub assembly and look at the bearings themselves; wipe away the grease and you should be able to see the part number stamped directly on them. If you are unable to find them, you need to use a digital caliper and measure your spindle to the thousandths of an inch where the bearings and grease seal ride. You can use the photo I've attached to see exactly where you need to measure.

For example, the Kodiak Disc Brake Kit # K2HR35D-8 I referenced earlier will fit a spindle with inner bearing # L68149, outer bearing # L44649 and grease seal # RG06-050. You will also need to be sure you have the correct brake mounting flange; this disc brake kit uses a 4-bolt mounting flange.

You are also going to need a brake actuator rated for disc brakes - these have a higher psi than drum brakes so you will need, for example, the Titan Zinc-Plated Brake Actuator - Disc - 2-5/16" Ball - Bolt On - 8,000 lbs # T4747200 if you had a 2-5/16" hitch ball.

So, in short, the ratings for the brakes are determined by your axle and you will need to switch to disc brakes on both axles because of the different pressures.

I have added a link to a help article titled Parts Needed to Add Hydraulic Disc Brakes to a Trailer which I highly recommend taking a look at. I have also added a link to our selection of disc brakes and disc brake actuators for you to come back to.