By Roger Sitterly
In my first article, I explained why it’s important to think through any modifications you plan and to make sure they are integrated in such a way that you will end up with the results you desire. Here’s an example, using my MINI, to illustrate how I believe it makes sense to proceed if you decide to modify your car’s handling.
I bought my MINI new in March 2004, and before I made any changes at all, I put in almost 20,000 miles of windshield time. I wanted to become thoroughly familiar with the way the car handled before I made any changes. Once I had enough experience behind the wheel, I decided I wanted to accomplish the following goals in order to improve the car’s handling responsiveness and to increase my enjoyment of driving the car (caveat – your goals may or may not coincide with mine, which is perfectly OK):
1. Dial out most of the car’s understeer at speeds above about 30 mph, leaving only a little low-speed understeer. I wanted handling as close to neutral as possible between about 30 mph and about 80 mph with some trailing-throttle oversteer as part of the mix;
2. If doing #1 resulted in creation of some power-on oversteer at speeds above about 80 mph, I would accept it;
3. Improve the crispness of turn-in when cornering;
4. Slightly reduce the amount of body lean in hard corners;
5. Provide a more comfortable ride;
6. Maintain the original ride height;
7. Eliminate as much as possible the horrible black dust all stock MINI brakes emit while keeping as much initial bite and fade resistance as the stock brakes have and while also improving brake component life; and,
8. Improve, if possible, the linearity of braking response.
I addressed items #1, 2, 4, 5, 6, 7 and 8 all at the same time after researching the various options available for each. The steps I took were:
1. Installation of a three-position rear anti-roll bar;
2. Replacement of the run-flat tires with high-performance summer tires;
3. Replacement of the stock brake rotors;
4. Replacement of the stock brake pads; and,
5. Installation of braided stainless steel flexible brake lines.
I subsequently addressed Item #3 and did additional work on Item #5 when the original strut cartridges needed to be replaced by making the following modifications:
1. Installation of fixed front camber plates to add 1.25 degrees of negative camber; and,
2. Installation of performance struts to replace the stock struts.
At the same time, after several thousand miles of experience with the rear sway bar set at the softest position, I re-set it to the middle position.
The sum total of the above modifications was what I both expected and wanted. I specified what I wanted to accomplish, why I wanted to accomplish it, did the “due diligence” and research work to understand what combination of modifications would yield the result I sought, and made sure all the work was done to specification concerning installation, mounting torque values, etc. I now have a MINI that drives and rides the way I want, and for me, the effort was well worth the time, effort, and money involved. Many thousands of miles after those changes, I have not made any additional changes because I’m perfectly happy with the way the car handles.
Here’s what each of those modifications accomplished, and the trade-offs that were involved:
1. Three-position rear sway bar: The relationship between front and rear sway bars, along with other factors, influences the amount of understeer or oversteer present in a car. For reasons I’ll explain in a future article, stiffening up a front sway bar increases understeer and stiffening up a rear sway bar increases oversteer. The first position (softest) on the bar I bought was about 35% stiffer than the rear sway bar that came with the factory-optional “Sport” suspension”, which I ordered with the car. Stiffening the rear sway bar, first at the softest setting and then at the middle setting, added oversteer to (or, perhaps more accurately, removed understeer from) the car’s handling characteristics. I selected an H-sport bar because it is one of the few bars on the market for which relative stiffness numbers are available and because it is one of the few bars on the market with Zerk fittings so the bushings can be greased if desired/necessary. My MINI now exhibits just the barest trace of understeer at speeds between about 30 mph and about 90 mph, though under the right circumstances it is possible for me to get power-on oversteer if I wish. I have a modest amount of trailing-throttle oversteer at all speeds. The trade-offs are cost and that some people may not feel comfortable driving a car that does not exhibit the degree of understeer designed into the stock MINI suspension.
2. Change from runflat to non-runflat tires and go one oversize: With softer and slightly taller sidewalls, the tire itself absorbs more minor road irregularities and thereby reduces the amount of road “buzz” felt by occupants of the car. It was an excellent choice of tires for me –ride quality improved noticeably, as did both wet and dry traction. I selected Goodyear Eagle F-1 DS-G3 tires after reading numerous ratings and road tests, and after talking to several drivers who were using them on their cars. The tires had remarkably high levels of grip in both wet and dry conditions, loss of traction was progressive and clearly signaled to the driver long before it reached a critical stage, and they wore well – I got about 24,000 miles out of a set of four.
Regrettably, Goodyear stopped making the F-1 DS-G3s in size 215/45X17, so I changed to Falken Ziex 912 tires. The Falkens were slightly noisier and lacked a bit of wet and dry traction compared to the Goodyears, but in general I wasn’t unhappy with them. However, in search of better summer wet and dry traction, I followed the Falkens with a set of Michelin Pilot Super Sport tires. They were the equal of the Goodyears with one notable exception – they came with a 30,000 mile tread-wear warranty and I had worn them down to 2/23” of tread in only a tad over 15,000 miles.
Michelin rebated me a pro-rated dollar amount based on the tread life I had from the Pilot Sports, and I’m now using Michelin Premier A/S tires. I’ve only got about 7,000 miles on them, but so far they seem to have excellent wet and dry traction, turn-in response seems excellent, and the difference between wet and dry traction speeds in any given corner is not particularly great. I don’t think I’ll get the full tread life that Michelin guarantees, but I don’t have enough miles on them yet to be able to accurately predict how many miles of use I’ll get from them.
The major trade off with all of these tires is that they’re NOT runflats, so I need to carry a “mobility kit” because there is no room for a spare tire in the “S” model. Some people may not feel comfortable with that. On the other hand, non-runflat tires are much less expensive and remain far more available to the tire-buying public than runflats. I explained “over-sizing”, explored the pros and cons of runflat versus non-runflat tires, and discussed the various types of tires in a previous article.
3. New brake pads and rotors: The stock MINI pads contain a very high amount of carbon, which is the source of much of the black dust you’ve probably noticed on your car’s wheels. Mercedes, Audi, BMW, Porsche, and Volkswagen drivers all have the same problem, which seems endemic to German brake pads. In addition, the stock MINI rotors are relatively soft, wearing away at almost the same rate as do the brake pads. It is extremely rare for a set of original MINI rotors to last through two sets of pads without wearing to the minimum thickness for safe braking. As they wear, the rotors emit metallic particles that combine with the pad dust to coat your wheels.
EBC Greenstuff pads are well known for their very low dust (which is grey in color rather than black) and have very high initial bite from cold. In addition, they are not quite as abrasive as the stock pads, so they won’t wear the rotors as much. Finally, they have a high enough thermal range that you can use them for the occasional autocross without worrying they will overheat and fade, so they’ve got a substantial reserve to handle emergency braking demands. The Powerslot rotors I got are harder than stock rotors, have a plated finish on the hat so it won’t rust, and the slots are machined in so they do double duty as minimum-thickness indicators – when you can’t see the slots, you need to replace the rotors. There’s no more pulling a wheel and messing around with a micrometer to see if the rotors are getting too thin.
Other brands I would consider using based on having friends in the MINI community who in fact use these brands, are Hawk HPS pads (very low dust, excellent bite from cold, less abrasive than OEM MINI pads) and Brembo rotors. When I replaced the OEM rotors and pads (with about 30,000 miles on the car) both front and rear pads and rotors had been worn to about half of their useful life. That is, I probably could have safely used them for a total of between 55,000 and 60,000 miles.
I proactively replaced the OEM rotors and pads with Powerslot rotors and EBC Green Stuff pads prior to doing MINIs On The Dragon in 2006 because the original equipment rotors and pads seemed to be getting thin and I didn’t want to be driving on the Dragon with worn-out brakes. In addition, I was absolutely fed up with the copious amount of black brake dust the OEM pads and rotors generated. Eight years later, I replaced the first set of Powerslot rotors and EBC Green Stuff pads with new Powerslot rotors and EBC Green Stuff pads because the first set of pads and rotors were getting thin and I didn’t want to be be driving all of MINI Takes The States 2014 with well-worn brakes. I stayed with the same brands as I installed in 2006 because I was so happy with them. I got more than 90,000 miles out of the pads and rotors and, based on micrometer measurements of the remaining thickness of the thinnest rotor and thinnest set of pads, I probably could have safely used the old ones for another 10,000 miles (which, coincidentally, is about what I drove in 2014 just driving to, doing, and driving home from MTTS).
The trade off in all of this is that aftermarket pads and rotors are more expensive than OEM. Also, the EBC pads took far more time and effort to bed in properly. There are arguments on both sides of the issue concerning the use of slotted or drilled rotors on a car – I hope to explore those in a future article.
4. Braided stainless steel brake lines: Stock MINI flexible brake lines are reinforced rubber and typical of what is found on virtually every new car today. Under the hydraulic pressures generated by hard braking, they can expand slightly. This will reduce somewhat the linearity of the braking you experience. In addition, if not replaced for many years, stock flexible brake lines tend to swell inside, reducing the volume of brake fluid that can be moved quickly and reducing the immediacy of braking response. Braided stainless steel lines do not have any of those problems. Because I so rarely am on the brakes anywhere near the maximum, I can’t honestly say I could tell the difference in brake feel, but someone who either tracks or autocrosses his/her MINI might have a different experience. The trade off here is that braided stainless lines are more expensive than reinforced rubber lines. Caveat: If you decide to buy braided stainless steel brake lines for the “bling” factor, be advised it’s a waste of money. You can’t see them behind your wheels unless they’re neon-colored, and then you’ll see them only for as long as it takes road dirt to cover them up.
5. Koni FSD struts: These struts have an internal design unlike any others on the market. They allow small changes in the suspension to happen easily (like relatively “soft” shocks) but firm up substantially when a larger change begins to occur. Because a lot of the minor and annoying discomfort experienced by occupants of a sports car are caused by minor irregularities in the road (pavement joints, coarse or “washboard” pavement surfaces, etc.) the ability of the Konis to absorb those irregularities without transmitting them to occupants provides a more comfortable ride. At the same time, the Konis stiffen appreciably under severe loading, so when you take a hard corner at speed they do their part in holding the car on the road. The trade off is that Konis cost more than stock struts, and Koni recommends you don’t use them with lowering springs.
Knowing when you need to replace the shocks on a car is a judgment call in most cases. If the car has relatively soft springs (like many American luxo-barges), vigorously bouncing each corner of the car in turn and watching how quickly the shocks dampen that bounce provides a relatively easy test. In a MINI, because the stock springs are much firmer, that test is difficult to perform. I arbitrarily decided my OEM shocks were due for replacement when the car had about 50,000 miles on it, but it’s entirely possible that was either earlier than absolutely necessary or later than should have been the case.
I’m now about to replace the first set of Koni FSDs with four new FSDs. Again, it may be premature, or it might have been advisable a year ago. In any case, I got about 90,000 miles of highly satisfactory service from the FSDs and gladly pay the premium price they cost. I don’t have any experience with yellow, orange, or red Konis on a MINI, so can’t comment on them. Based on the Koni website, the orange “STR.T” shocks are intended as replacement for OEM shocks but with slightly firmer valving. Next are the red “Special” shocks, which are firmer than orange, but not adjustable. The yellow “Sport” shocks are both firm and user-adjustable, though when I put a set of the yellow “Sport” shocks on my Datsun 240-Z many years ago, I found the softest setting more than adequate for the improvement I desired, and I got more than 60,000 miles out of that setting before selling the car. Your mileage may vary.
There are many choices of top-quality shocks and struts, and I hope to discuss the choices available in a future article.
6. Negative camber plates: Adding negative camber to the front keeps more of the front tires’ tread surface on the pavement as you turn the wheels. More tread surface means more traction, so turn-in crispness is increased. Trade-offs include slightly increased tread wear on the inside edge of the front tires and a slightly harsher ride because the camber plate bearing is mounted in urethane instead of rubber. I hope to discuss camber plates in a future article.
In addition to those modifications, I’ve subsequently installed four adjustable rear control arms. Having the ability to adjust all four allows the alignment of the rear wheels to be set precisely within MINI’s design parameters (or outside them if that’s what you want). I stay within MINI’s design parameters because I’m happy with the way they work in combination with the rest of the modifications I’ve made. I selected the adjustable control arms because the right rear wheel was slowly drifting out of alignment (perhaps due to a worn bushing) and I wanted the car to be properly aligned. I’ll discuss adjustable control arms at greater length in a future article.