Hub of Motion: Replacing bearings on a full-floating hub system

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This dust shield should have been the first part installed when building the Daimler’s full-floating hub assembly. This was a late-production item not mentioned in the SP250 factory workshop manual.

This dust shield should have been the first part installed when building the Daimler’s full-floating hub assembly. This was a late-production item not mentioned in the SP250 factory workshop manual.

By John  Gunnell

We had done everything outlined in the shop manual to restore the wire wheel hubs and the disc brakes on the front of the Daimler SP250 roadster. Since the British sports car had originally been taken apart by someone else and we didn’t have photos, drawings or notes about the disassembly, we thought we did a pretty good job putting it back together. Why was there an extra part left over?

To answer this question, we e-mailed Daimler expert Laurence Jones in England. By the next day we had an answer. “The extra part is a dust shield added to late-production cars,” Jones wrote. “It mounts on the inner flange of the stub axle, up against the vertical link (pivot pin to Americans) and between the link and the dust cover on the end of the inner bearing.“ This added dust shield was never pictured or mentioned in the Daimler shop manual. Since so few SP250s were made, the shop manual was never updated. Jones said we should use the dust shield, so that meant disassembling the hub again.

Although SP250s are rare, their underpinnings are a direct lift from the mass-produced Triumph TR3 and TR3A sports cars. They also have many similarities with other cars (even domestic) that used wire wheels with full-floating hubs. With full-floating hubs, the wheels are mounted to the hubs. This contrasts with semi-floating hubs where the wheels are mounted to the axles. With full-floating hubs, the hubs (not the axles) bear the weight of the vehicle.

There’s a small likelihood you’ll ever work on a Daimler SP250, since only 2,500 were built, but some of the following information and parts sources will be helpful whether you’re working on a British sports car or a Model A Ford. Removing and installing bearings, greasing hubs, brake repairs and tips on tools are pretty much universal, no matter what vehicle you’re restoring.

 

 

Bad Dust

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ClampTite

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CUSTOM PLATING SPECIALIST

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On the SP250, the hubs are bolted to the brake discs (rotors) with four bolts. The hubs have a small bearing and bearing race at the outer end and a large bearing and bearing race at the inner end. A donut-type felt oil seal fits into the metal ring that is tapped into the outer end of the hub after installing the bearing and race. The “leftover” dust shield goes against the ring. It has a flat, angled bottom lip that hooks into the vertical link to keep the shield from turning.

After installing the smaller bearing and race at the outer end of the hub, slide the hub/disc onto the stub axle. This may knock the small outer bearing loose. If so, just put it back in the hub by hand. When properly positioned, the large inner end of the hub is against the once-forgotten dust shield.

At the smaller, outer end of the hub, a washer with a D-shaped hole goes over the D-shaped axle. Push the washer against the bearing with the castle nut, adjust the tightness of the castle nut and position it so a cotter pin can be installed to keep the castle nut from coming off. The washer is a finger’s length inward from the hub’s outer edge, so the hub has holes through which to install the cotter pin.

We marked the old races just to be sure which side went in first. Behind the old bearings and races are the new parts. Behind them are the hubs with knock-off spinners (one left- one right-hand) on the smaller outer ends.

We marked the old races just to be sure which side went in first. Behind the old bearings and races are the new parts. Behind them are the hubs with knock-off spinners (one left- one right-hand) on the smaller outer ends.

 

Before installing the hub on the axle, position a shield (brake backing plate) over the front suspension members. This will be held in its final position by the same bolts that are later used to attach the brake caliper, but for now, leave it loose. Next, make certain that the pads in the caliper are pushed back and place the caliper over the disc on the rear upper part of the disc. The bolts that attach the caliper are threaded at the ends only, so they need to be tapped a bit to make things tighten. Then, put the bolts through the “backing plate” mounting brackets and the calipers, as well as the shims mentioned below.

Factory shims were used under the caliper bolts to make slight inward/outward adjustments of the caliper on the rotor. The goal was to match the vertical centerline of the caliper to the center of the brake disc’s edge. The thin shims are shaped like a barbell with holes in each end that the caliper bolts pass through. When disassembling a car, carefully note how many shims are used in each side. Since we did not have that information for this car, we played around until the centers were aligned.

 

 

 

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Northwestern Auto Supply

An old time parts store since 1946 with 4 buildings full of old inventory of antique and classic parts for the quality minded owner who wants to avoid off shore products. Engine, chassis, ignition, and brake parts shipped world wide. Machine shop and babbiting also. www.northwesternautosupply.com

LeBaron Bonney

LeBaron Bonney produces award-winning interiors for antique and custom restorations. Our antique kits fit 800 vehicles 1916-1962 and are the best-fitting interiors in the industry. Our EZ Boy kits fit many vehicles from the early 1920s to the present and include custom seat upholstery, panel covering, complete seats, carpets and headliners.

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The 50-mm collar from the inexpensive bearing and seal driver set was flattened on opposite edges so we could push it down past the old, larger bearing race. Then, we leveled it inside the hub and used it to drive out the race.

The 50-mm collar from the inexpensive bearing and seal driver set was flattened on opposite edges so we could push it down past the old, larger bearing race. Then, we leveled it inside the hub and used it to drive out the race.

The castle nut adjustment mentioned earlier is what actually moves the caliper in or out on the rotor to get it on center. The shop manual states the nut should be tightened until the brake disc just about stops turning. Then, it says to back off the nut from one to two flats (to a spot where the cotter pin will slide though a hole in the axle end). If the correct number of shims were used, the centerlines of the calipers and discs should be close.

Naturally, the hubs have to be greased, and there are no Zerk fittings or provisions for adding grease after the hub and brake assemblies are built. The Daimler’s shop manual says to fill the entire hub between the inner and outer bearings with the proper type of grease. The inner and outer wheel hub bearings themselves (tapered roller bearings on this car) should also be liberally greased.

The proper felt grease seals were difficult to find. Thinking the Daimler and Triumph seals were identical, we ordered Triumph seals from Moss Motors (www.mossmotors.com) and found they were smaller. We found the correct seals from John Carey in Massachusetts (www.daimler-sp250.com), who said that they had been “unobtanium” for a while, but were recently reproduced.

Often, a hammer or mallet pounding against the proper-size aluminum collar from a bearing driver set will do a very good job of installing a bearing or race. “Tap, tap, tap”-type hammer blows will evenly “walk” a race into place.

Often, a hammer or mallet pounding against the proper-size aluminum collar from a bearing driver set will do a very good job of installing a bearing or race. “Tap, tap, tap”-type hammer blows will evenly “walk” a race into place.

Every part on the hub assembly was removed from the car, cleaned or sandblasted and repainted with Satin Black chassis paint from Eastwood (www.eastwood.com). The calipers were completely rebuilt and upgraded with stainless-steel inserts by Brake & Equipment Warehouse in Minneapolis (www.brakeplace.com). We feel this is the only way to go in preventing rusty brakes on a collector car that will be stored.

Since we had the car completely apart during its chassis restoration, we replaced all of the bearings and races in the hubs. The small bearings and races were a common number used on trailers and were available at any auto parts store. The larger bearings were harder to find and came from John Carey. We also sourced new brake discs (rotors) from Carey’s New England Automotive Restorations. The discs were slightly different than the originals, which had slotted edges. We discovered why the new rotors were different — many of the slots on the originals had fractured.

Driving out the smaller races that were in the hub was easy. They sat up against a ridge on the bore of the hub that had notches on either side. We placed a long punch where the slots were located and tapped with a hammer and the small bearing races flew out. It was a different story with the larger inner races.

If using a bottle jack press to install bearings or races, don’t apply so much pressure that the hub casting fractures — a real problem. Instead, apply pressure, then back off and check that the bearing or race is going in straight and even.

If using a bottle jack press to install bearings or races, don’t apply so much pressure that the hub casting fractures — a real problem. Instead, apply pressure, then back off and check that the bearing or race is going in straight and even.

The inner end of the hub passes through the new brake rotor and bolts in place. Grease is added to fill the void between inner and outer bearings. Then, the felt seal is placed in the dust cover, which is tapped into the outer end of the hub.

The inner end of the hub passes through the new brake rotor and bolts in place. Grease is added to fill the void between inner and outer bearings. Then, the felt seal is placed in the dust cover, which is tapped into the outer end of the hub.

To get each of the large inner races out, we took an inexpensive Bearing Race and Seal Driver Set from Harbor Freight (www.harborfreight.com/10-piece-bearing-race-and-seal-driver-set-95853.html) and ground the opposite edges of the purple 50-mm aluminum collar flat. This allowed the collar to slip down into the hub, past the old race. Then, we tapped the collar until it was sitting flat inside the hub, against the old race, and installed the drive handle. Next, we put pressure on the driver handle with our 20-ton bottle jack press.

Since we knew it is hard to press anything in or out that isn’t perfectly flat or level, we avoided generating hub-breaking forces with the press. Instead, we repeatedly applied a little pressure and sprayed lubricant into the hub to make parts slide easier. Each time we stopped to check on our progress, we adjusted things so that we were pressing straight and level. Eventually, the large bearing race, which had sat in the hub for 50 years, dropped out with a telltale “pop.”

Flattening the edges of the 50-mm collar didn’t ruin it and it still came in handy when we were pressing in the new smaller bearing race. Other collars were used to press in the larger race. Sometimes, it seems like the new bearings go in easier with the 20-ton press and sometimes they seem easier to install using repetitive hammer blows. Again, when using a press, things have to be perfectly straight, while using a hammer tends to make “automatic” adjustments with each blow. The important thing to check is that the bearing races seat properly. When things are right, that telltale “pop” or “snap” can be heard again.

One other thing worth mentioning is that experts in a particular type of car often used shortened descriptions for parts. For instance, Daimler expert John Carey referred to the smaller hub bearing races as “1910s,” although the full part number was LM11910. When we asked the Bumper to Bumper counterman for a 1910 bearing, his computer almost crashed. When we then checked the old bearing number and told him we needed an 11910, he found it on the shelf.

On this second try, we made sure we put the dust shield on the inner flange against the pivot pin. The flat bottom has a lip that fits into an opening on the pivot pin so the dust shield doesn’t turn when the hub assembly is in place.

On this second try, we made sure we put the dust shield on the inner flange against the pivot pin. The flat bottom has a lip that fits into an opening on the pivot pin so the dust shield doesn’t turn when the hub assembly is in place.

 

With all bearings, felt seals, dust covers and shields in place, the hub and rotor assembly can be slid onto the stub axle. This may push the small bearing out, but it can be pushed back in. The arrow points to the cotter pin install hole.

With all bearings, felt seals, dust covers and shields in place, the hub and rotor assembly can be slid onto the stub axle. This may push the small bearing out, but it can be pushed back in. The arrow points to the cotter pin install hole.

 

A large washer with a D-shaped hole fits over the stub axle. Use a piece of pipe and small hammer to tap the washer in against the small bearing’s outer retainer. You must have the stub axle thread showing to install the castle nut.

A large washer with a D-shaped hole fits over the stub axle. Use a piece of pipe and small hammer to tap the washer in against the small bearing’s outer retainer. You must have the stub axle thread showing to install the castle nut.

 

Using your finger or a magnet tool, twist the castle nut onto the end of the stub axle. Note how the hub is splined to match up with the wire wheels. When your install is all done, the knock-off spinner will thread onto the end of the hub.

Using your finger or a magnet tool, twist the castle nut onto the end of the stub axle. Note how the hub is splined to match up with the wire wheels. When your install is all done, the knock-off spinner will thread onto the end of the hub.

With the chassis supported (here on a Backyard Buddy Easy-Access unit), you can tighten the castle nut until the brake rotor just stops turning. Then, you back off one to two flats until you can drop the cotter pin into the hole in the axle.

With the chassis supported (here on a Backyard Buddy Easy-Access unit), you can tighten the castle nut until the brake rotor just stops turning. Then, you back off one to two flats until you can drop the cotter pin into the hole in the axle.

 

A stainless sleeved caliper rebuilt by Brake & Equipment Warehouse mounts to two holes in front suspension member. The caliper mounting bolts are also used to hold the “backing plate” the arrow is pointing to, plus required shims.

A stainless sleeved caliper rebuilt by Brake & Equipment Warehouse mounts to two holes in front suspension member. The caliper mounting bolts are also used to hold the “backing plate” the arrow is pointing to, plus required shims.

 

 

If you liked this article on replacing bearings on hub systems, you might be interested in our other restoration products:

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