How To Determine If Boat Trailer has 10 Inch or 12 Inch Brake Assemblies

Products Featured in This Question

Hydraulic Brake Kit - Uni-Servo - Free Backing - Dacromet - 10" - Left/Right Hand - 3,500 lbs

(346)

$185.91

etrailer Electric Trailer Brakes - Self-Adjusting - 10" - Left/Right Hand Assemblies - 3.5K

(2762)

$161.07

etrailer Electric Trailer Brakes - Self-Adjusting - 12" - Left/Right Hand - 5.2K to 7K

(2762)

$199.09

Easy Grease Trailer Hub/Drum Assembly for 3.5K Axles - 10" Diameter - 5 on 4-1/2 - Galvanized

(673)

$161.14

Trailer Hub and Drum Assembly - 3,500-lb Axles - 10" Diameter - 5 on 4-1/2 - Galvanized

(93)

$146.64

Question:

I have a boat trailer and need to replace the brakes. I know I have a #84 spindle, 15 inch rims 5 lug at 4.5 inch spacing...Is there a way to tell if I need 10 inch or 12 inch brakes? Thanks.

asked by: Paul

Expert Reply:

When determining if you need 10 inch or 12 inch brake assemblies there are a couple of easy things to check to confirm the fit for your trailer. The first thing is you can measure the diameter of your hub. The second thing is you can look at the brake flange, if it has 4 bolts then it is 10 inch if it has 5 then it is 12 inch.

Because you know you have a #84 spindle we can be confident that you have a 3,500 lb axle and you will need the 10 inch assemblies. I recommend the Hydraulic Brake Kit - Uni-Servo - Free Backing # AKFBBRK-35-D which will fit your current hubs. If you also want to upgrade your hubs while you are at it, I recommend the Galvanized Hub/Drum # AKHD-545-35-G-K for your boat trailer. If you have EZ Lube Spindles then # AKHD-545-35-G-EZ-K will come with the grease cap that allows for that zerk access.

If you have electric brakes on your boat trailer then you can use # AKEBRK-7-SA for 12 inch or # AKEBRK-35-SA for 10 inch assemblies.

expert reply by: Jason S

Randell

12/1/2024

I have a two axle trailer custom built for a cobalt 226 with disc brakes on the front axle only. In 2018 I had a shop replace the brakes. We used the boat very little and only made short moves from storage to the ramp. We made a trip to San Antonio from San Francisco when we moved in May 2022. Upon arrival the pads were almost completely worn away. We replaced the pads and have put less than 500 miles on the trailer. While doing maintenance repacking the bearings we found that the right side pads were already heavily worn unevenly. We decided the mounting brackets may have bent so we replaced the mounts. Calipers and pads with new. They are tie down G5 9.6 disc brakes. After a short trip to the storage yard of less than 10 miles the brakes are locking up. Question Should this trailer have larger brakes? Brakes on both axles? Or have we done something drastically wrong? Thanks

Robin H.

12/1/2024

@Randell assuming you have 3,500 lb axles it is probably safe to assume your brakes match the capacity of the axle so you're putting a lot on a single set of brakes. I would definitely add brakes to that other axle. As an example, say you do have two 3,500 lb axles and your Cobalt 226 is 5,000-6,000 lbs loaded on the trailer. Your single set of brakes designed for 3,500 lbs is going to wear down significantly faster because it has to stop all of that extra weight beyond its capacity. If you share that weight between two sets of brakes, just like you do with the axles, the wear on the brake pads will be normal since the combined rating is 7,000 lbs which is in line with your boat and trailer.

Randell

12/1/2024

@RobinH Thanks for your quick reply. Sort of disappointed with cobalt’s choice af brakes on the trailer.

Robin H.

12/1/2024

@Randell if you can identify the axles I can help you find replacement brakes and an extra set of brakes for the axle without them. Tie-down engineering is no longer around so we wouldn't be able to match the other set but we have good replacement options. While you're at, it you will also need to make sure that other axle has a brake flange. If it doesn't, you'll have to add one or replace the axle with one that has a brake flange to install another set of brakes. I'm sure wherever/whenever that trailer was built it only needed brakes on a single axle by law so that is what they did to save money. Just like a lot of utility trailers for heavier loads can come without brakes because the state they're manufactured in doesn't require them by law, even though they really should come with them.