I went to Gingerman last Saturday for an OT event and had some interesting observation/questions on handling of a stock Focus on street V's R tires and some general wheel tire comments as well, I'll be interested in what other people think.
First street wheels and tires. I'm utterly amazed that people are running 17x7's with 205 or 215 section tires on basically stock Foci. I had bought a set of SHM 17x7's that I was going to put on my car for daily use, now I guess I'll e-bay them. As I live in Michigan I've met too many people who end up with square wheels on Foci when running such low profile tires, so I decided to go with 16's instead. I bought a set of Cougar 16 x 6 1/2 six spoke wheels as I've always like the styling and I know Ford ran some Foci with these wheels on durability up at MPG (Michigan proving grounds) As such I thought they were the correct offset, but I guess I was wrong, while I haven't measured it and can't find it yet, it seems that the wheels have more offset than the stock ones do. I don't like the extra torque steer and tugging at the wheels or tendency to try and climb up the camber of the road from the increase in scrub radius. These factors could be made worse by the tall tires that I've got currently which I'll come to next. What are other peoples experience? Also the weight seems to be an issue. These wheels and tires weighed in at 39lb's V's 33lb's for the stock 15's according to my bathroom scales. I can't decide if I can really feel the extra weight, or if it's a combination of the taller gearing and offset. But I 'think' I can feel the extra mass when accelerating and over poor road surfaces. No matter what, when I come to look for some new correct sized tires weight will definitely be a consideration.
Tires, a friend bought some old SVT Contour wheels to use for snow tires on his SVTF, they came with some part worn 205/55 16 Yokohama AVSI's which he didn't need, he gave them to me to burn up at Gingerman as I didn't want to put any more R tires on my Focus until I have some -ve camber (see comments below). So, even though they are too tall I mounted them and have been driving them for the last couple of weeks.
OK, now back to the original point of this note, on track handling. First, I don't claim to be the next Schumacher or anything but I would like to consider myself a competent track driver with a fair amount of OT, autocross and race experience. That said I've only OT'd my Focus once before, at Waterford Hills last year. Then it was totally stock with the exception of 205/50 15 Victorracers on it. At that time the car handled as I'd expected, neutral to understeer but very predictable. It totally destroyed the outside edge of the front tires, to the point where I rotated a different tire onto the front left every session and had corded all four by the end of the day. Because I didn't want to destroy the (used) Hoosiers I've now picked up for it, which are far more camber sensitive than Khumo's, I'll save them until I do something with the suspension. I decided to just use the AVSI's I mentioned above. I had no clue as to what to use for tire pressures so I started at 45f 40r cold, through the day I came down and down until I was at 45f 39r hot. The thing that amazed me was how much different the car handled than with R tires, forget the lack of grip, what got me was how loose the car was. It was very very easy to rotate the car with a trailing throttle or trail braking. In the first session it was almost scary, with lower tire pressures and more confidence it was fun later in the day, but I was glad this was an OT day not a race where mid corner changes may have been needed. I just could not believe how willing the car was to rotate, my ITC Fiesta never rotated so willingly. So, when people are talking about adding a larger rear bar, are you doing this with an other wise stock suspension on the track with street? If so I'm surprised, it might work at autocross speeds, but I'd be amazed for track speeds.
My thinking for this behavior is that with R tires the lateral grip was sufficient that the weight transfer allowed enough roll that the front suspension to get to the point where it was in an unfavorable part of the camber curve. The result being that the front looses grip first hence the predictable understeer. With the street tires the front stays in a more favorable part of the camber curve so can work more efficiently compared to the rear. I assume that the rear has a better range of usable travel than the front so works equally well on street or R tires. Am I on the right track here?
Now, while I have allot of track experience I've only once been to Gingerman before, about six years ago in a rental Contour so I don't even begin to know the track yet, but wow, turn 2 is really difficult. I was trying different lines all day and was never happy. I just couldn't find the right balance between where to turn in and where to apex. Many times I turned in and was still on a trailing throttle about 1/3 of the way through and the back started to come round, but If I got on the gas any sooner I was missing the apex and running wide. If I tried turning in later I'd find myself carrying too much speed and not being able to apex so I had to scrub speed. If I turned in early I'd apex too early and kill my exit. I'm not explaining this very well, but how the heck do you take that corner? On the whole I love the track, there doesn't seem to be one 'right' line, you seem to have a choice of several possibilities as to how to take different sections. I'm really looking forward to going back and learning more next year.
Thanks for reading my ramblings, I'd appreciate any feedback or comments people may have.