MINI Cooper S R53 – Ultimate Commuter Go-Kart
We all know how great a street car the MINI Cooper S is, but we had a customer who wanted to take it to the next level, even though this would only be used as a street / commuter car. So, all the main areas would be enhanced – wheels, tires, suspension, engine performance upgrades, exterior upgrades, interior upgrades…yep, that pretty much covers it. This was not a project to make it the fastest, or lowest, wildest or widest…this was a project to enhance all the main areas, make them all better, but ensure that the car would still be enjoyable on the harsh freeways and bumpy streets we have here in Northern California. That also meant some areas would not be touched, like the downpipe, exhaust. We wanted nirvana, better performance, but still maintain the great fuel economy as much as possible. Another item of particular concern was the suspension. The basic MINI Cooper S already has a relatively harsh suspension, and limited suspension travel, yet the stock street car sits too high, so that would need special care and attention.
Here are some pics of the completed project before we go into the details…..
Here are some pics of the car before the project started –
Stock engine, ignition, pulley, coil, plugs –
Stock front suspension, springs, sway bar, brakes….
So, on to the upgrades / enhancements.
As mentioned earlier, modifying the suspension on the MINI Cooper is tough, because the original stock ride is very rough, and there is not much suspension travel designed into the suspension geometry. If you just lower the car using sport springs, you end up with a MINI that just bounces down the road. If you alter the shocks only, you still have a car that sits too high, and you haven’t improved the handling of the car. We also know that the stock MINI, when pushed hard, has some slight understeer, so we needed to dial that out as part of this program. So, what’s to do, what’s to do?
We believe there are three elements that needed to be enhanced, (1) shocks / springs, (2) bushings, and (3) rear sway bar. You can’t just throw sport springs on…you can’t just throw any coil-over set on. The best value and solution we have found for the MINI Cooper is the Bilstein PSS9/10 system. It is only set in its price range that offers all the key elements needed, upgraded monotube shocks, inverted front struts, full compression and rebound shock valving adjustment, and adjustable height spring perches. We needed the adjustable spring perches to deal w the ride height and suspension geometry issues. For the same reason, we needed the full shock adjustment. If you just pick an economical set of coil-overs, the shocks are traditionally valved too stiff, and offer no adjustment, so the ride is even worse than the stiff ride the MINI already has. The Bilstein set also offers the nicest and quickest valve adjustment, all on one adjustment knob, so, if you need to dial in the suspension, you can, or if you want to make a change, anyone can do it on their own.
Next…sway bars. As mentioned, the MINI has just a hint of delay in the initial turn-in when cornering, otherwise referred to as understeer. The MINI doesn’t need much, but a slight upgrade to the rear sway bar is just the answer. There are many rear sway bars out there…and too often people think bigger is better, but that usually is not the case (in fact, on our race car programs, we try to run as soft of a sway bar as possible, as stiffer sway bars take away from mechanical grip, not add to it). So, there are 19mm, 20mm, 21mm, 23mm, even a 25mm rear sway bar. The stock MINI Cooper S has a 15mm rear sway bar, so we just need a slight upgrade, so we use the 19mm rear sway bar. If you put any of the stiffer bars, the car becomes “twitchy” when driving, and not confidence inspring.
Next….front sway bar bushings. Again, we want crisp, GO-KART like handling, so getting the car to rotate (sway bar), and respond to steering inputs (bushings) are key. The normal, stock front MINI Cooper lower control arm bushings are poor, and will crack and tear after normal street use, so there is a win-win element here. Install new front poly lower control arm bushings, and the steering is very crisp, tight, adding to that GO-KART like feel, and they will last, and induce no noise, vibration, or harshness (NVH) to the suspension or car.
The last step is setting the ride height to the proper value to gain as much suspension travel as possible, or to retain as much as possible, yet making the adjustment to lower the car to get both the look we want and to lower the center of gravity for better handling and transition response.
ENGINE / PERFORMANCE
The stock MINI Cooper S R53 probably has the easiest upgrade path option of any car out there. It is truly plug and play. Too many performance options cost too much, and deliver too little. But, that’s not the case w a SuperCharger Pulley upgrade. Again, here, descertion needs to be exercised. There are many SC pulley upgrades out there (13%, 15%, 17%, 19%, and I’m sure someone has made one even larger). We have found issues, long term reliability issues, w any of the larger pulley sizes if you go above 15%. They are great in the short term, but the rest of the engine has not been designed as an integrated whole to support boost levels that come from a 17% pulley or larger….and we have seen too many blown pistons from the larger pulley sizes. So, we have stayed w the 15% pulley, and have had great success. This still produces a large increase in overall HP, and can’t be beat for the “bang for the buck” scale.
Here is the stock pulley –
And here is the new 15% upgraded SC pulley (smaller diameter) –
The other area we have found needing to be addressed when you do the SC pulley upgrade is the plugs / coils. We upgraded the plugs (BRISK), which has a stronger tip, and is one grade colder to support the upgraded boost levels of the new SC pulley. The plug wires and coil pack are also available in RED to match the rest of the car…..how convenient.
WHEELS / TIRES
We really default to one wheel almost every time w the MINI Cooper S. We have tried several, but we love the look of the OZ Ultraleggera. Its light, but strong. Its not expensive. It comes in several color options. It provides clearance should the customer want to run JCW big brakes later.
For tires, for a commuter car, our “go to” tire of choice is the Continental DW (now called Extreme Contact Sport) or DWS06+ tire. This tire mimics the best tire on the market, which in our opinion, is the Michelin SuperSport. The Conti has the same time of tread pattern, and the DW is more the equivalent of the SuperSport, and if you want good grip but long life as a commuter tire, then you pick the DWS (it will last about 50% longer than the DW).
EXTERIOR / INTERIOR
Not a lot needed to be done to this car….just little refinements on the exterior to make the car complete. Windows tinted. We changed out the front grill set to the JCW honeycomb grill set. The mirror caps were painted to go w the whole car paint scheme.
To make the car truly like a GO-KART, and since this was not a family car, we had the option to delete the rear seats (get rid of weight), and add a complete street harness set. We finished off the rear seat delete panel in black carpet to make it match the interior, and added the Schroth “click-in” harness set in RED to match the rest of the car.
Now the car has the personality to match the GO-KART handling and performance.
BRracing – building nothing but the best for our customers.