At a Glance
- SKU: 77M-1210
PRODUCT INFORMATION
Product Details
Heavy Duty Electric Braking Systems
Electric Brake Magnet for 12-1/4" Dexter & Universal 8K-15K Axles
Restore heavy-duty stopping power with this OEM-spec magnet kit, designed for high-stress 12-1/4" electric brake assemblies on 8,000 to 15,000 lb axles.
Part Number: 77M-1210 Size: 12-1/4" x 3-3/8" Capacity: 8K - 15K Axles
Overview
The 77M-1210 (Interchange 71-378) is a heavy-duty replacement magnet designed to provide consistent braking force for trailers equipped with 12-1/4" electric drum brakes. This kit is a high-quality replacement solution designed for major brands including Dexter, Lippert, and Rockwell, making it an essential service part for goosenecks, lowboys, and heavy cargo trailers.
R&P Service Insight
Worn magnets are the #1 cause of weak or surging trailer brakes. Replacing the magnet restores the electromagnetic pull required to actuate the brake shoes.
- Versatile: Fits both Left and Right side assemblies (Non-handed).
- Universal Fit: Cross-compatible with Lippert, Rockwell, and AL-KO.
- Easy Install: Includes a pre-wired blue pigtail for faster splicing.
R&P Knowledge Hub
Compatibility: Dexter 12-1/4" x 3-3/8" electric brakes manufactured after June 1992.
Vehicle / System Fit: Optimized for 8,000 lb, 10,000 lb, 12,000 lb, and 15,000 lb heavy-duty axles.
Installation Notes: Verify your drum diameter (12.25") and axle capacity before ordering. Not compatible with 3.5K or 7K (12" x 2") systems.
Performance Insight: Features a high-tensile spring and secure retainer to ensure the magnet maintains proper face-contact with the armature plate for immediate braking response.
Brand & Fitment Note
Selling Brand: R&P Carriages / Verified Aftermarket Replacement
Application Reference: Any OEM or platform names like Dexter, Lippert, or Rockwell describe compatibility and application style only.
What This Means: This listing is for an OEM-spec replacement magnet kit, designed to match the fit and function of Dexter K71-378-00.
Before Ordering: Please verify your brake diameter is 12-1/4" and your axle is rated between 8,000 lbs and 15,000 lbs.
R&P Repair Insight
When replacing magnets, always inspect your brake drum’s armature surface. Deep scoring or uneven wear on the drum will cause new magnets to fail prematurely.
- Wire Check: This assembly features blue lead wires; ensure proper grounding during installation.
- Brake Type: Fully compatible with both Manual Adjust and Self-Adjusting brake styles.
- Axle Specifics: Fits 4" and 5" (15K) brake configurations specifically.
Features
Heavy-Duty Build
Engineered to withstand the extreme heat and friction of 8K-15K heavy-haul applications.
Complete Kit
Includes magnet assembly, retainer, and spring for a comprehensive service.
Universal Compatibility
Direct replacement for Dexter, Lippert, Rockwell, Carter, and AL-KO 12.25" brakes.
Installation Ready
Pre-wired pigtails and included instruction sheet ensure a seamless setup for DIY or shop use.
Specifications
| Specification | Detail |
|---|---|
| Part Number | 77M-1210 |
| Product Type | Electric Brake Magnet Kit |
| Brake Size | 12-1/4" x 3-3/8" |
| Axle Rating | 8,000 – 15,000 lbs |
| Wire Color | Blue (Pigtail Lead) |
| Side | Universal (Left or Right) |
| Interchange | 71-378, K71-378-00 |
Fitment / Application
| Category | Details |
|---|---|
| Brake System | 12.25" Electric Drum Brakes |
| Primary Fit | Dexter Axles (Post 6/92) |
| Axle Types | 8K, 10K, 12K, 15K Units |
| Notes | Fits 4" and 5" (15K) brake configurations. Not for 12" x 2" brakes. |
Included Components
| Quantity | Item |
|---|---|
| 1 | Electric Brake Magnet Assembly (Blue Wire) |
| 1 | Magnet Retainer |
| 1 | Magnet Spring |
| 1 | Installation Instruction Sheet |
Verification Required: Ensure your trailer uses 12-1/4" diameter brakes. This magnet is specifically for heavy-duty axles (8K-15K) and is not compatible with standard 3,500lb or 7,000lb (12" x 2") systems. Always inspect armature plates for wear before installing new magnets.
71-378 Dexter magnet replacement, 12.25 brake magnet, 8k axle brake magnet, 10k axle brake magnet, 12k axle brake magnet, 15k trailer brake magnet, heavy duty electric brake magnet kit
Related Parts & Kits
Check fitment, measurements, and kit contents before ordering. Related parts may not be required for your repair.
Looking up part numbers in our catalog…
Your repair list1 item selected
Selected products are added together. Review the cart and verify kit contents to prevent duplicates. Prices and discounts are determined at checkout.
BEHIND THIS LISTING
PHOTOGRAPHY & RESEARCH
Ariah Granados
DIGITAL PRESENTATION & DEVELOPMENT
Ken Martin
ONLINE SALES & QUALITY ASSURANCE
Rayn Fisher
WE’RE HERE TO HELP
Not sure it fits?
Have your SKU or manufacturer part number, photos of the original part and mounting, and any critical measurements ready. Capacity, voltage, or bolt pattern can help too.
815-357-3292 · 270 E Jackson St · Seneca, IL 61360
CUSTOMER REVIEWS
Leave a Google review
Good people. Real trailer work.
Customer feedback summarized from Google and Yellow Pages. Dates are shown where available.
TRAILER PARTSGOOGLE
Ordered trailer repair parts repeatedly; praised fast service, careful packing, and accurate orders.
RV KEYSGOOGLE
Found the correct RV keys at a good price with free shipping; the keys worked as expected.
AXLE & LEAF SPRINGSGOOGLE
Needed an unusual axle and leaf-spring size; the team listened and helped him sort out the fit.
PARTS & SHIPPINGGOOGLE
Praised the OEM and aftermarket selection, discounts, quick shipping, and friendly parts staff.
CUSTOM AXLEGOOGLE
Got the axle he needed right away, set up with a custom spring perch.
WELDINGGOOGLE
Praised the polite staff and quality welding on a project.
GAS STRUTGOOGLE
Replacement struts brought a long-used door back to working order.
CUSTOM TRAILERGOOGLE
Had a trailer built to his needs at a fair price, then found parts for two other trailers in stock.
CUSTOMER SERVICEGOOGLE
Praised the customer service after working with R&P over several years.
GAS SHOCKGOOGLE
Found the gas shock he wanted at a good price with shipping included.
CARGO TIE-DOWNGOOGLE
Received swivel D-rings with backing plates and praised the price, correct order, and service.
PARTS DELIVERYGOOGLE
The right parts arrived the first time, with fast delivery and helpful staff.
PROJECT HELPYELLOW PAGES
Said project advice and prompt shipping helped finish a trailer project.
SHIPPINGYELLOW PAGES
Reported helpful service and fast shipment to Germany.
SUSPENSION KITYELLOW PAGES
Praised a suspension kit, fair pricing, and good parts.
TRAILER CORDYELLOW PAGES
Was pleased with a replacement trailer cord.
SERVICE & PARTSYELLOW PAGES
Noted dependable service and products across repeat visits.
AXLE INSTALLATIONYELLOW PAGES
Said the axle installation fit perfectly and thanked Josh and the crew.
HITCH REPLACEMENTYELLOW PAGES
Praised the crew’s professionalism during a difficult hitch replacement.
PRICE & SERVICEYELLOW PAGES
Liked the product, price, communication, and shipping.
LISTING INFORMATIONYELLOW PAGES
Said the product description explained what would work for the trailer.
PRODUCT & SHIPPINGYELLOW PAGES
Received the item as described with very fast shipping and plans to return.
COMMUNICATION & SHIPPINGYELLOW PAGES
Praised accurate description, quick shipping, and clear communication.
PRICE & PRODUCTYELLOW PAGES
Was happy with the product and its price.
SELLER EXPERIENCEYELLOW PAGES
Called it a pleasure doing business with R&P.
INSTALLATIONYELLOW PAGES
Was pleased with product quality, quick delivery, and an easy installation.
PRODUCTSYELLOW PAGES
Was enthusiastic about the products.
DURABILITYYELLOW PAGES
Was ready to install the product on every trailer they own.
REPEAT CUSTOMERYELLOW PAGES
Expected to buy again after a good experience.
INSTALLED PARTYELLOW PAGES
Reported that the newly installed parts were working perfectly.
REPEAT CUSTOMERYELLOW PAGES
Said things went well, as they had on previous visits.
COMMUNICATION & VALUEYELLOW PAGES
Praised clear communication and fair value.
TRANSACTIONYELLOW PAGES
Said the transaction went as expected.
PRICE & PACKAGINGYELLOW PAGES
Noted good value, careful packing, and fast shipping.
PROFESSIONAL SERVICEYELLOW PAGES
Found the team professional and easy to work with.
COMMUNICATION & SHIPPINGYELLOW PAGES
Praised fast shipping and good communication.
TEAMYELLOW PAGES
Shared appreciation for the owners and their company.
SHIPPINGYELLOW PAGES
Reported prompt shipping and said they would buy again.
CUSTOMER SERVICEYELLOW PAGES
Found R&P easy to deal with.
SERVICEYELLOW PAGES
Praised the people and the service.
FIT & SHIPPINGYELLOW PAGES
Reported a good fit, fair price, accurate listing, and quick shipping.
DELIVERYYELLOW PAGES
Received the order a day early and recommended the seller.
CUSTOM TRAILERYELLOW PAGES
Described a no-hassle, professional custom-trailer purchase.
TRAILER PURCHASEYELLOW PAGES
Praised a new trailer, custom additions, helpful staff, and clear pricing.
HUB COVERSYELLOW PAGES
Found the right hub covers quickly and got helpful maintenance advice.
AXLE HELPYELLOW PAGES
Said R&P helped their company get back on the road after an axle problem.
DUMP TRAILERYELLOW PAGES
Was happy with a dump-trailer purchase after comparing options.
BRAKES, DRUMS & SEALSYELLOW PAGES
Received clear help choosing brake assemblies and bearing seals, followed by fast shipping.
DUMP TRAILERYELLOW PAGES
Found a good deal on a 16-foot dump trailer and planned to return.
FRIENDLY SERVICEYELLOW PAGES
Thanked the staff for their patience and recommended the shop.
Showing 3 of 50
Need help with this part? Send photos, part numbers, and measurements. We’ll help you narrow it down.