Ahhhh the stock Ghia brakes. Truth be told, if I was going to run the Porsche D90 wheels I have, this is all I would put on the car. I know it goes against the German Look ethos, but bear with me for a second. The Rally Bug has run the 'stock discs' on all four corners for a decade (Ghia fronts, Empi solid rotor rears), and there is only one mountain pass in all my years where I can boil the brakes to the point that the final switchback becomes a prayer as to whether I'll make it or not. The car has all the braking that it needs. Contrast that to the '69 German Looker which has Porsche Boxster calipers on all four corners (the "proper" setup). Take that car to the track, and five laps in you've got your braking points dialled, and you're having fun. Lap six, you enter corner one, and just about smash your face off the windshield because all of a sudden you
finally have enough heat into the brakes for them to be doing something. I don't really track my cars, I use them for 3-5 day rallies and tours. So, I'm driving on the street all the time (though, sometimes 'spiritedly' in remote areas). While the Porsche brake setup is effective, you're certainly carrying a tonne of weight around that never actually gets utilized because you can't actually get heat into them on the street. And so, if this new build was going to wear wheels that would hide the brakes, I'd just toss the solid-rotor setup on all four corners and be done with it. It won't get any magazine covers, it won't get much respect from VW people at car shows, but I suspect anyone who actually really understand performance tuning would tilt their head and go "actually, yeah, that makes sense." Besides, with all the weight added by this suspension setup, a little weight savings would be nice!
But then, after purchasing two full sets of Porsche D90 wheels (so I could have four 6" wide ones)...I came upon a set of the wheels I
actually wanted for this build. To say they are rare, at least rare in excellent condition, would be an understatement. Also, since they are no longer made new...almost impossible to get in good condition. Alas, the brakes are fully visible through this particular set of wheels, so we need to do something that won't embarrass me.
One of the biggest things I miss about the German Look forum becoming so quiet, is the manner in which it seems everyone on here is trying to improve the build. Whether it's constantly upgrading the same car, like Wally, or building better with the next car...the standards were always improving. For myself, I like to do minor upgrades to the cars I've built, but I keep major changes for "the next build". I could sell all the Porsche bits off the German Looker and try and improve it, or I could simply just make this car an evolution of what I've learned. Well, that and I've had a particular set of brake calipers in storage for years I've always wanted to use.
This particular set has been waiting for a GL style build for quite some time, the original spec is actually for NASCAR if you can believe it. Now, the fronts are insanely massive…and won’t fit under my 16” wheels. But the rears…seems to me they would make excellent front calipers.
Total piston area of the stock front callipers - 2.46” (I think, going by memory here). Total piston area of the smaller AP Racing callipers? 3.18” (again, from memory). When I plug them into a brake master sizing tool, the master sizing for the front brakes changes by just 2.54mm. Basically it’s
almost doable with the “big brake” standard Beetle master. Hmmmm.
One thing about this project is that it has to use factory steel fenders, and I really want to do it without tire rubbing (like every other beetle I own). You Europeans have no idea how lucky you have it with CSP and Kerscher fenders being available to you…trying to get them here in North America is almost impossible. I couldn’t even get CSP to sell them to me. I kid you not, I emailed in requesting an order for four fenders, and a time to call as I was ready with my Visa number. They refused the order because it was “too expensive to ship them”. Even after I explained that a) I never asked how much the fenders were, and b) I also didn’t ask how much the shipping was, they still weren’t interested in selling a set. I have contemplated flying over and bringing them home…but now the whole thing annoys me so much I’m like “damnit, I’ll build the car without them!” So, to avoid the rubbing, and to make the brakes fit, we’re going to need to do some maths. Lots of maths. And modelling. Thank god for the age of computers and 3d models…
Started with a factory rotor:
Then modelled a wheel and spacer setup that is known to me, and known to fit the way I want it. This is also how I’m going to buy myself 10mm worth of mistakes later on. Add the dimensions of the wheel I’d like to use, and we can see how we’re getting on. At this stage, you can see the white wheel (that I want to use) is going to probably require a flight to Germany to bring home some fenders.
And now, delete everything you aren’t going to use.
It was before this stage that I was talking with Todd at Subarugears. Through their brake program, they offer a front brake conversion kit that can use virtually any Subaru brake kit. Since the AP calipers came from my rally-world friends, and I know lots of Subaru tuners, I realized I could probably find a rotor and mount that would work. Todd was gracious enough to offer to sell me
just his front hubs (not the caliber mounts, etc) and went one step further to give me the critical measurement I needed off his hubs to see if I could use them in my brake setup. Since my wheels are 5x114.3 (STi / WRX bolt pattern) this could be the path of least resistance. So I modelled up Todd’s front hub, and used brembo.com to search any possible rotor combination that might work.
Unfortunately, the calipers I want to use have pretty specific rotor requirements, that are more common to the rear end of performance vehicles than the front. 0.81” wide rotors, or 20mm. Any of the
Subaru front rotors start at 23mm, so that was pretty much a dead end. All my rally buddies use those nifty floating rotors on hats, so I figured there must be some Subaru fitment units out there I could play with.
COUGH Apparently my rally buddies have
much deeper pockets than I was aware of. Fortunately Willwood components are somewhat affordable, so off I went to find a rotor that would fit the caliper, and then a hat that would fit the rotor. After finding a few that would work, I modelled up what i thought would be the best option. And then combined it with my spindle setup. I’m now using four wheel segments, which allows me to compare the current brake setup to the stock setup, so I can keep an eye on how I’m doing for placement. The last image below is both the new rotor/setup and the stock rotor all overlapping so I can fully appreciate how this is going to sit on the spindle.
Once I think I’ve got it all correct, it’s off to the 3D printer! In my case I’m using an enclosed Prusa MK3S and I generally prototype in PLA. While I prefer to prototype in white, or light grey, apparently I’m running low so it’s into the strange mix of colours for this one! I had two potential rotors and hats I wanted to try, the goal is to get the caliper placed “perfectly” in the wheel. The smaller silver hub is printed with adjustable rings so I can play with the rotor offset, and the larger hub is printed with both Subaru and Porsche bolt pattern so I can play with the fit of two wheel types.
The 3D printed parts are so accurate, I actually had to use the shop press to put the bearing races into the hub.
IMG_5375 by
Dave Hord, on Flickr
Just a few millimetres of clearance between the caliper and the spokes. The wheel actually sits 4.5mm closer to the chassis than a factory sport wheel, so I’m basically dead-nuts perfect. And these are the wheels I will use for the car. They are a 16” Speedline Corsa, in 5.5” wide. These wheels were used in WRC for winter rally, and haven’t been produced since they switched to the 15” wheel rule. I can still get this wheel in 16” x 6.5 and 7, which is my likely path for the rear in the long term…but I have four of the 5.5’s which will do just perfectly for now. I thought I was pretty darned lucky when I managed to buy a set of Gold ones off of Travis’ car. The fact that I found the
white ones I also wanted (from a different rally team) in almost perfect condition was just outstanding.
-Dave