August 06, 2020

Hub up! Why changing your classic Subaru's wheels is worth it

Classic cars have the style, modern cars have the engineering... or so the traditional logic goes. Of course there is no reason you can't do what Marty has done with his WRX STi coupe and put all the best later model saucy upgrades into his classic coupe, in the hope of trouncing MOOG's good-handling BRZ - and you can now see the showdown HERE.

Marty has been having a blast taking his classic WRX STi to track days since he picked it up, but driving a 20-year-old turbocharged performance car hard regularly can unearth some underlying issues. Even when they were just a few years old, Subarus had a bit of a reputation for torching wheel bearings and brake components in their front-ends when driven hard on the track regularly.

Part of the problem is the amount of heat which builds up when you're driving on the track, particularly with sticky track rubber. The front wheel bearings have a tough job in an all-wheel-drive car, as they have to withstand all the mega-forces with every turn and brake application for each corner.

The heat build-up can literally cook the grease the wheel bearings rely on to spin. The wheel bearing is a key part of your car's suspension as it lets your wheel spin freely and carries its load. They are lubricated by high-temperature bearing grease which is packed in and around the rollers to keep it all spinning nicely, but if that grease gets overheated too many times it leads to wear on the bearings, which creates slop in the hubs leading to dangerous handling faults with the car!

The issue of hot hubs cooking mad track day plans was rectified in when the 2005 model year STi Imprezas hit the market. Subaru's factory high-performance division, STi, had installed new, larger wheel bearings to cope with on-track punishment. However, this led to a raft of other knock-on changes.

While most Subarus run a 5x100 PCD wheel, the MY05-on STis used a 5x114.3 PCD wheel as STi had changed the whole front and rear knuckle assemblies, which is what the brakes, driveshafts and suspension (and steering on the front-end) bolt-to. This means the shock-absorbers and springs are different, as Marty found out when he swapped to the later-model drivetrain for his V5 coupe (check the videos HERE and HERE).

As part of the process of swapping in a gearbox and diff which wouldn't explode required the stronger later model GD-generation STi Impreza driveshafts, this meant Our Fearless Hero Martin was going to need to also change to the better, heavier-duty hubs and knuckles. This is because the Subaru driveshafts have a splined male end which bolts into the knuckle and the force from the gearbox is transferred into motion through the splined teeth on the end of the shaft.

Thankfully, Subaru saw fit to keep the same bolt pattern spacing on the front hubs the same, so you don't have to change all this hardware if you just want to add Brembo brakes to the front-end of your classic Subaru.

Here you can see the difference in size between where the MacPherson strut attaches to the knuckle on the old (classic) and new (GD STi) set-ups. There are coilover conversions which can make this job simpler, but Marty wanted to stay with a conventional spring/shock strut assembly for the time being.

Having swapped all the heavier duty, more high-performance-oriented parts over Marty's WRX coupe is now in a much more track-ready state and the good news is almost all these parts are a bolt-on solution (with the exception of how the lads chose to modify the front struts).