Before you read this article, let me tell you a little bit about my vehicle: It is a 1998 Z3 2.8 with the 17″ tire and wheel package from the factory. Suspension modifications include the HMS strut brace and the RD sway bars.
As I watched the soft tread on my 17″ Michelin MXX3 Pilots quickly fade away practically mile by mile, I knew soon that new tires would be necessary. It was just the rear tires that had lost the tread, as the fronts still had a nice amount left. Because of the staggered sizes used on the Z3 2.8 17″ wheel package, which happen to be the same as the M roadster/M coupe, with the front tires smaller than the rears, tire rotation is not a possibility.
Replace just the rears?
Since the fronts still had tread left, I questioned whether it would be feasible to replace just the rears. The 245/40/17 size is no longer available from Michelin for the MXX3 tire. Thus I would have to either go to 255/40/17 or change all four tires. I decided, based upon reports I’ve read on the message board, that I did not want to increase the size in the rear as it may negatively (or positively) affect handling characteristics, and may detriment the effect of ABS and ASC+T. I finally decided that I would get four brand new tires to replace the worn out rears.
The first thing that I needed to determine before I went shopping for a tire was what kind of tire I wanted to get. A summer tire, a winter tire, all-season tire, a cheapo tire that fits, etc. Only you can decide based upon your driving habits and weather conditions what type fits you best. Living in Miami, and never seeing snow, I decided that I wanted to get an all-out performer, similar to the standard MXX3 that came with my car from the factory. Rain, while frequent in the summer months, never lasts long. The hot sun dries the water up after any rainstorm. Thus wet performance would be appreciated, but would not be at the top of my list. After all why buy a drop-top if you like rain so much? 🙂
The first place that I went to check information regarding tires was the TireRack. They offer online ordering of tires with great prices plus plenty of information on cars, tires, etc. Under their “Maximum Performance” category I looked at several tires, including: Bridgestone S-02 PP, Dunlop SP Sport 8000, Pirelli PZero, among a few other brands. The tire that caught my eye was the BFGoodrich G-Force T/A KD, as they had intense neon colored advertisements of achieving never-felt before “g-forces”, hence the tire’s name.
Research Into the G-Force
I began to do some research on my own to try and verify BFG’s claim on their brand new tires, which were introduced some time in November, 1998. The first place I checked was, naturally, the TireRack. In their preliminary review they tested the tires on two cars on the track, a Porsche 996 and a Corvette. They said that the G-force tires practically eliminated the oversteer problem that the rear-engined Porsche cars are famous for, and provided a significantly higher amount of grip then the Pirelli PZero tires already mounted on the car. This was starting to look good, a tire that provides a significant increase in grip than the already ultra-grippy PZero? Then they tried it on the Corvette, stating that it was easier to drive the car harder and faster. Read the review at the link above for details.
Another ad that caught my eye was one that was in the January 1999 issue of Car and Driver. Showing a yellow M roadster, BFGoodrich proclaimed that their tuned M roadster with stock size G-force tires provided 1.05g of lateral acceleration on the skidpad. That is a lot of lateral acceleration, more than many many supercars out there. As the tread on my Pilots were wearing down, I was getting more excited to see what it could do to my “tuned” Z3 2.8 (swaybars).
A Bit More Research…Found by Surprise
As I was roaming through the January/February 1999 issue of Sports Car Magazine International, I accidentally stumbled upon an article on…you guessed it: the G-force T/A KD tires. It was written up in their “New Technology” section. Basically they stated that it provided more grip and increased the ability of every car they tested it on compared to the other tires that were on the several cars they tested, including the Bridgestone S-02 PP, and the Pirelli’s. I was not surprised. They even went on to say that this was practically an autocross/racing tire and that it should have been standard on the Corvette had the engineers had their way, as it would have made that car much better in stock format.
A Little Bit About This “Technological” Tire
The BFGoodrich G-Force T/A KD tires are pretty impressive in the amount of technology they have imbedded into the tire. Designed for dry traction primarily, the “KD” stands for, or so I have heard, “killer dry”. This is BFG’s first asymmetric street tire. That means that you need to have a different tire for the left side and the right side of the vehicle. A negative aspect in terms that you can’t rotate the tires even left to right, but positive in the aspect that it increases handling significantly. By producing asymmetric tires, BFG increased the “contact patch” of the tire significantly by optimizing one side of the tire for turn opposite to the side it was on. For example, if you are turning right, you want the most traction at the edge of the tires. On the left side of the left tire is the dry traction part, and the right side of the right tire. Using this technology, the contact patch of the G-force tire is 79%! If you don’t know what that number means, it means that this is one of the most connected tires to the road in existence. Even many other max performance tires don’t even come close to that number. The rest of the tire is optimized mainly for wet traction and high speed stability. The speed rating of the tire based upon TireRack and BFGoodrich’s site is “Y” rated, which is 186mph. This differs from the standard and expected “Z” in a performance tire, at least it did to me. However “Z” is defined very nondescript: 149mph and over. So what is better, Y, or Z? More on this later below.
Time To Order
Everything I had read about this tire sounded like it was too good to be true. They last longer than the Michelin Pilots accorded to the UTQG tread wear rating (140 vs 200), cost less, are available in the stock Z3 2.8 17″/M sizes, and perform better. I decided to order from TireRack. Service was superb and the tires arrived at the tire shop via COD order exactly as directed. The two front tires I received were both built the same week, and the two rears matched build weeks as well. Just 3 (or maybe it was 4) business days later the tires came and it was time to go get them mounted and balanced. Note to other Z3 drivers: unfortunately these tires don’t come in any 16″ size. The minimum size would be the 17″ wheel package, making it available only on M roadster / M Coupe cars or the Z3 2.8 with 17″ package, it is unfortunate that they do not offer a 16″ size and maybe on the basis of thisarticlee they will. To my surprise, the tires all had “ZR 91Y” written on the sidewall, as opposed to “YR” as indicated on the TireRack site. Either way though, no roadster driver will ever bring their car this fast and it is nice to know that under every condition you could physically do these tires will handle it.
Enough Talk Already, How Does It Drive?
Well let me just say this… If to you, Happiness is the corner, not around it, then these new BFGoodrich tires ARE happiness! They are that good. I will tell you a bit more about it in the categories below, but, they are superb. The second I took the car out of the tire shop, turning out at even 5mph, I noticed an immediate difference. If you are considering any other tire to replace your worn out Pilots, or are unhappy with the Dunlop 8080E’s, this is the tire to get.
The dry traction of this tire is superb. Far exceeding the abilities of the Michelin Pilot MXX3, this tire knows how to stick. And stick, stick, stick it does. Acceleration had a noticeable increase in speed. But acceleration is not where this tire really shines, but it is the reverse. This tire likes to STOP, and STOP it does now. I performed several braking tests within the same day with both the Michelin Pilot MXX3 and the new full tread G-forces with barely a few miles on them. From 60mph, when flooring the brake pedal with the Pilots, there was considerable bite and the car stopped quickly, with the ABS kicking in and locking up most of the way down. I repeated this test, from 60mph, with the G-forces. I was amazing at the difference the G-force offered. The ABS did not kick in in the 60 to 0 test as the tire did not loose traction. I tried it again to make sure I was pressing hard enough and it did not loose traction, thus the ABS did not need to be activated. Not only did the brake pedal feel firmer, the car felt like it was stopping quicker, and I am assured that these tires have reduced the already short stopping distances of the Z3 to something even shorter. I then did a 70mph to 0 brake test, with both tires. With the Michelin Pilots, there was grip except not so as much as there was at 60. The car stopped formidability, however the ABS was anti-locking the entire way down. On the 70 to 0 test with the G-forces, the tire just seemed like it had more bite. The ABS did not go on immediately however. Once I was almost done with the braking session and stopped I felt the pedal pulsate, but it was only for a very short amount of time, considerably less so than the amount of time I felt the pedal pulsate with the Michelins. I am convinced that I now have a safer car and better active ability to prevent an accident. Also, the car is no longer as sensitive to wind when traveling on the highway as it was with the Pilots. This same effect can be felt when going over a bridge. In every car I’ve been in, over the bridges between Miami and Miami Beach the cars always go a little left and right for the split second when you are over the metal grating. I did not feel this effect for the first time in my life in a car, as the tires just took it and the car exhibited no sideways motion.
If you have ever driven another car besides the Z3 for a few days, and then return to the Z3, the brake pedal always feels somewhat strange at first because it is so much tighter than practically any other car. Well this is the feeling that I felt with only changing the tires from MXX3 to G-force. It is amazing how much the tire affects the feeling and characteristic of the entire car.
Rating for BFGoodrich G-Force T/A KD in Dry Traction: 10/10
Rating for Michelin Pilot MXX3 in Dry Traction: 9/10
After living with the G-Forces for several weeks, and in rainy weather, I can definitely say that these tires are great in the rain. Their resistance to hydroplaning was outstanding and dry traction even in the wet was still superb, and offered very similar feel then what was described in “dry traction”. Even in standing rain, under heavy acceleration or heavy cornering, the tire sticks to the wet ground without any tail wagging, and the traction control light never went on once during any of my tests. These tires perform far greater in the wet than the Michelin MXX3s do, and I was vividly surprised to see that the new tires do so great when I did not expect them to be so perfect based upon their tread pattern.
Rating for BFGoodrich G-Force T/A KD in Wet Traction: 9/10
Rating for Michelin Pilot MXX3 in Wet Traction: 5/10
I thought nothing would come close to the Pilot MXX3 in this category after driving them for 13,000 miles on my Z3. Boy was I wrong. The Pilots are snow tires compared to the G-forces in this category. You may have heard of the problem with the Z3’s rear suspension and its natural tendency to understeer, as it is an older technology derived from the E30 M3. In my opinion, this tire has fixed this flaw with the Z3. I can’t state how it would do on a stock car, as I have the Racing Dynamics Sway Bars, but even with them on and the Pilots I could understeer easily by giving a nice amount of gas coming out of a turn fast. Oversteer came easy on the Pilots too when applying full throttle in the turn. Not so with the G-force. It is very difficult to explain the way the G-force feels as it feels different than any other tire in existence. It just feels like the car is that much more “connected” to the road, and is probably a result of the triple or quadruple contact patch this tire provides. Taking a slalom turn quickly, the G-force was precise and not once did the ASC+T light come on. Nor did the car loose its tail, on repeated aggressive attempts. Remember, these tires still have only about 60 miles on them, so its still full tread depth. I assume they can only get better as the tread wears down a bit. Even applying full throttle around some turns, I heard screeches, yet the car did not oversteer. The tires (and now, the car) have that much more of a handling increase. It is going to take some getting used to and some risky maneuvers that I don’t recommend anybody try out on the street to reach the limit of this tire.
Rating for BFGoodrich G-Force T/A KD in Cornering Traction: 11/10 (it is just that much better than the others)
Rating for Michelin Pilot MXX3 in Cornering Traction: 9/10
The steering response of this tire is absolutely amazing. Not only does it provide more smooth transactions around turns, but it provides much more road feel in the steering wheel, and even in the gas pedal when you are using that to modulate around a turn. However, I think there comes a point where a tire for the street has too much steering response (I can’t believe I can say this). Maybe on the track it is OK, but for the street I think that BFG engineered too much steering response in this “street racing tire”. Wow? Too much steering response? It is so much more precise that the steering of the Z3 with this tire is a bit transformed. Moving it just a little bit gives the tire a bit of a “sway” feel that was not evident with the other tires. Perhaps it will take getting used, but I am not sure how I will appreciate this effect on long highway trips, as it requires more involvement in driving, which is fun of course when you are taking turns fast, but not when you are going down a straightway interstate. I will update this section as I see the long term effect of this to let you know how it is.
Long term update:
Maybe my initial complaint was valid but I think after breaking in the tire and letting the rubber settle down that my original comments are no longer valid. It does take some getting used to (as anything), but now I have learned to appreciate the tire and adjust my driving condition and style. Straight on steering feedback is definitely increased compared to the MXX3s, and straight line stability is awesome. Even after bringing the tires up to the 2.8L’s max of 128mph, the tires were well balanced, poised, and perfect. High speed is where this tire really shines, as at this speed the extra response does actually seem needed. I’d also like to add that the stability of these tires is amazing. I stayed at top speed for several minutes without stopping and the tires just loved it. Everything was smooth as butter and after getting out of the car and feeling the tires, they were just barely warm. I think that they dissipate heat a lot better than any other tire out there as well.
Rating for BFGoodrich G-Force T/A KD in Responsiveness: 10/10
Rating for Michelin Pilot MXX3 in Responsiveness: 8/10
This tire is a bit weird in the way to describe the ride quality compared to the Michelin Pilots. While both harsh, as any 17″ performance tire is, this tire is a bit of an oxymoron. Over bumps, the tire transmits more of the bump to the driver, as you feel it in the steering wheel, and it is harsher then the Pilots. I want to attend this to the road feel this tire gives you over the others. But after staying in my car as a passenger, I haven’t noticed this, as the ride is actually better. What better place to test for bumps then an apartment complex full of speed bumps? That is where I did my comparison test. On the road, however, the BFG’s provide a smoother more buttery ride when you were NOT going over large bumps. I should emphasize large as if you are going on an interstate the slight bumps were absorbed better by the G-forces then the Pilots, but the Pilots took the speed bumps better. This category wasn’t really important to me in my tire buying decision, but hey I like the buttery feel better when highway driving.
Long term update:
The tires have changed a bit again after becoming broken in. The ride quality seems to be exactly the same as the MXX3, maybe slightly slightly better. Highway driving is superb, as is its ability to absorb bumps in heavy turns.
Rating for BFGoodrich G-Force T/A KD In Ride Quality: 7/10
Rating for Michelin Pilot MXX3 In Ride Quality: 6.5/10
This is wear this tire shines. In the dump, that is. This is the likely one of the nosiest tire I’ve ever heard. It’s loud and it’s noisy, and hey the engineers probably didn’t even pay attention, as that was not the design goal of this tire. Just put the top down (or for coupe owners) make the radio louder. The noise goes away.
Long term update:
Again the tires have changed after being broken in for several thousand miles. The noise is worse than the MXX3, but it is a different type of road noise than them. For example, on the highway with the MXX3 you would hear knocking as you kept moving at high speed. With the G-Forces, while being noisier, you don’t hear this knocking, but there is rather a high pitched noise. Such as when you are going over a bridge or such. I have gotten used to it and it is not that bad at all, not nearly asnoticeablee to me now as it was when I first got them. But all the extraadvantagess this tire gives is much more important then noise.
Rating for BFGoodrich G-Force T/A KD in Noise: 3/10
Rating for Michelin MXX3 Pilots: 5/10
Can’t answer this one, as the tires have only about 100 miles on them right now. However, as this tire does in most categories, I believe it will be excel above and beyond other tires, including the Michelin Pilots. I don’t like replacing my tires all so often, so perhaps these will give me 20,000 miles with a wear rating of 200, as the Pilots gave me 14,000 with a wear rating of 140.
Long term update after 3000 miles:
Wear is significantly better than the Michelin Pilot MXX3s were. There is just a hair of a bit ofnoticeablee wear on the rears. The fronts show absolutely no wear at all. I am definitely going to be pleased with this tire.
Rating for BFGoodrich G-Force T/A KD in Wear: 7/10
Rating for Michelin Pilot MXX3 in Wear: 5/10
The G-forces have a rim protector that works very well. It is a big extra piece of rubber that goes around the edge of the rim, literally “hugging it”. This prevents the wheel from getting scuffed. I really hate to say it but I tested it once and it worked, I rubbed against the curb backing out and found no damage to the wheel.
These tires are expensive, yet not significantly more than other tires compared to it, especially given the increased ability that these tires give you. They are cheaper than the Pilots in the same size too, but not by much ($5/tire).
Long term update:
Tire Rack lowered the price a few dollars.
Rating for BFGoodrich G-Force T/A KD in Cost: 2/10
Rating for Michelin Pilot MMX3 in Cost: 2/10
Overall, I am quite pleased with my purchase and hope to have a fun time with my new “incredible” G-forces (as the ads go). After 3000 miles however I have noticed one thing. I am not understeering or oversteering anywhere NEARLY as much as I did. I actually miss sliding around the turns a bit as it is always fun to have the tail go out a little bit. But now I’ll admit I’ve only done it once, and since then (without changing my driving style on the street/highway) I haven’t done it at all because it just has such a high limit. It’s obvious that this tire is much more suited to the track then for the street.