Assembly Tips for D.I.Y. Kits - Hydraulic Disc Axle Assembly


These instructions assume some basic mechanical knowledge and the ability to weld to an acceptable standard.
If in doubt please refer the job to qualified personnel.

1. Pack bearings with grease & fit large inner bearings to hubs & hubdiscs

2. Fit grease seals to rear of hubs & hubdiscs.

3. Fit hubs to lazy axle. Fit small outer bearings & tighten down castle nut firmly. This ensures bearing cups are pressed firmly into hubs. Back off castle nut until hub is loose, then re-tension until free-play in hub is gone but bearings are under no pre-load (over tightening shortens bearing life).

4. Fit split pin & dust cap. Lazy axle is now assembled.

5. Fit hubdiscs to braked axle with same procedure as steps (3) & (4).

6. Fit disc brake shoes to hydraulic disc brake assemblies

7. Fit disc brake flanges to inner side of disc assemblies using bolts & stainless steel sleeves supplied.

8. Slide disc assembly over hubdisc & locate disc flange to axle with entire assembly facing what will be the front of trailer, with brake bleeder to top of axle.

9. Hold or clamp caliper assembly so outer brake shoe is hard against hubdisc (this ensures axle flange will be welded square to assembly & hubdiscs).

10. Position entire disc assembly on stainless steel sleeve so a gap of approx 3mm exists between disc mounting flange & disc assembly. (As brake pads wear, assembly will slide along stainless steel sleeve).

11. Apply liberal amounts of antispatter to hubdisc & cover grease seal with wet rag or PVC tape to protect.

12. Tack weld flange & unbolt disc assembly. Weld disc flange to axle all around from outside edge & top & bottom end, using mig or low hydrogen electrodes. It is not necessary to weld inner side of flange closest to hubdisc.

13. Clean antispatter from hubdiscs using methylated spirits & then refit hydraulic disc assembly to hubdisc, apply loctite to mounting bolts & rebolt to disc flange.

14. Hydraulic disc brake axle is now assembled.

Final Assembly

1. Fit hydraulic brake coupling to drawbar.

2. Fit flexible brake hoses to hydraulic calipers ensuring the copper washers are fitted before tightening.

3. Weld 5/8" washers to convenient location on trailer chassis for fitment of flexible brake line from calipers to body. Ensure sufficient movement on flexible line is available for suspension travel, fit off with hose clips supplied.

4. Weld head of 1/4" BSW x 1" Bolt to location on trailer chassis for fitting of 3 way block. Location chosen should allow convenient connection of brake line to LH & RH flexible hoses as well as running of main brake line to back of master cylinder.
(typically the 3 way block is fitted to the RH side inner chassis of trailer)

5. Tack weld tabs to locations on chassis for brake line routing. (typically 1/2" flat washer) lines must not be allowed excess movement or vibration or working hardening and fractures will result.

6. Run brake lines from 3 way block to LH & RH flexible hoses. Lines must be fitted off with short tube nut and double flare both ends.

7. Run remaining 3/16" bundy tube from 3 way block using a double flare and short nut tube nut up to master cylinder on coupling. Fit off at master cylinder using long tube nut & compression olive.

8. To bleed brakes, fill master cylinder with brake fluid. Use handbrake assembly on coupling to manually bleed. Bleed long side (LH side) the short side. No air is present in system when handbrake lever actuator does not pump up repeated operation.

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