Some Assembly Required – Four Splined Hubs

Another month, another milestone! I now have four splined hubs mounted on the car. Theoretically, I could throw wire wheels/tires on the car. And what? Since the engine is inoperable, all I could do is roll it out of the shop door and push it back in! It is a nice picture to contemplate but I’m going to settle right now for just knowing the work is done.

There is a good chance you are asking “What is a splined hub?” Don’t be embarrassed, it is likely that many club members have never owned a car with splined hubs. So let me explain.

When the E-Type was presented, it came with wire wheels. Why? Well I suspect the main answer was that it placed the E-Type into a market segment that included Ferrari and Maserati, which came with wire wheels. Maybe not so practical but very cool! They are undoubtably more expensive to produce than a solid steel wheel and they are certainly more work to keep clean. But they are very sexy.

The wire wheels on an E-Type had a racing heritage in that they were attached to the front axle with a single large “knockoff”. This is the roundish appendage with ears that one beats with a hammer to loosen and tighten. A main advantage of a knockoff is that during a racing situation, when time is of the essence, they can be removed and installed quicker than a bunch of lug nuts. Fun fact. In the Jaguar Spare Parts Catalogue (SPC), the “knockoffs” are called “hub caps”. Another fun fact. Only recently, NASCAR has changed from 5 lug nuts to a single center wheel nut. Formula One and other high end racing series have been using single center wheel nuts for quite some time. They are rarely used on road cars.

The single center wheel nut squeezes the wire wheel onto the axle. But the rotational power is delivered by a set of meshed splines. A picture is attached of the splines, which are basically a series of little V’s arranged around the central opening. This is a high end restoration and I am replacing many mechanical wear items but as with any car with splined hubs, the splines can become worn down over time. In the worst case scenario, the splines will be worn down to the point where the wire wheel is free to spin and the car does not go or stop at that wheel. More common is the splines are worn somewhat and you get a little clunk as you get on and off the power. In my case, another reason for new hubs is that I could drive the bearing races for the new axle bearings into them as fresh parts.

To mention a few more technical details of the front suspension, it consists of unequal length A-arms. These make up a parallelogram with unequal sides. This design, which has been used on cars long before the E-Type, allows the suspension to move up and down vertically in response to cornering and road deviations, yet the verticality of the tire/wheel is maintained fairly precisely. Keeping the tire vertical keeps the most rubber in contact with the road. Most modern cars use a McPherson strut suspension design, which gives the same dynamics but with a simpler parts list (and thus lower cost).

The front suspension uses a straight torsion bar to “hold up” the weight of the car. In simple terms, a torsion bar is a coil spring that has been “unwound”. In the case of the E-Type, it is compact but it also moves some of the large suspension forces back to the stronger monocoque structure, allowing the engine compartment frames to be of lighter construction.

The remainder of the front suspension is fairly standard, by today’s standards, with disc brakes and rack and pinion steering, though these components were a little more exotic in the early 60’s.

Turning to the rear of the car, an Independent Rear Suspension (IRS) unit is used. I had restored my IRS unit last year but had not installed it in the car until recently. The IRS was also a design that was fairly exotic by the standards of English sports cars in the 60’s, although the basic concept had been around for decades. As the name implies, each rear wheel can move independently up and down, while remaining roughly vertical. Again, a superior way to keep the most tire in contact with the ground during cornering. Each tire/wheel is fed power from the IRS driveshaft components using a splined hub.

Installation of the IRS went fairly smoothly, in the great scheme of car restoration things. That said, like many others, I had to use some coercion to get all the holes lined up for the various brackets and links that attach the IRS to the body shell. After it is installed in the car, all that remained was to attach the driveshaft, brake lines, and parking brake cable. Another exotic feature of the E-Type IRS is that the disc brake calipers are mounted “in-board” of the rear wheels. This is a racing thing to reduce “unsprung” weight. It may be racy but the end result is that if you have to do much of anything maintenance wise to the rear brakes (beyond bleeding and changing pads) you might have to consider dropping the IRS out of the car to gain access. Like many things, if you do it few times, you probably get better at it!

So that is the story of Four Splined Hubs. A pretty good milestone for my restoration. But there are still many things left to be done.