Ok, so now that I've had my Tach for 3 days
... figured it was time to put it to some good use and record some measurements before and after tire swap, here's what I came up with:
Here's some more pics and size comparisons
These tires are very big. And you can see in the pictures they barely fit.
With the front suspension still off the ground I did some clearance inspections and the tires
WILL make contact on the sheet metal towards the rear - feet rest area - of wheel well. The is no contact towards the front side of wheel well only the rear side. But the contact only happens when turning the wheels almost to it's max turn radius position.
I figured I would try driving around int them anyways, and be conscious about not fully turning the steering wheel, which I normally don't do.
I was pleasantly surprised to find out that I can drive it as normal without any major rubbing issues. 90degree turns @ stop signs - no problem. But there was some rubbing on extreme turns, but only on the passenger side, and not where I was expecting. It turns out the the outer portion of the tire, and only on the empty side of the car, will rub on certain turns with the plastic inner lining of the wheel well as shown. This was very unexpected. So in fact, in my case, tire rub is almost a non-issue.
I'm more concerned with the angle of attack the car now has due to the miss-matched tires, and feel this will be counter productive. But I don't have another set of tires to put in the back to even it out. I didn't want to lower the car until I had chosen what tire size I was going to stick with... and if I wind up with these, there won't be much lowering
Better under body aero work would definitely be a must if this size works out.
As far as engine performance, well you can compare RMP vs SPEED above, but on the 10 or so miles tested for each tire size 1/2 of the trip was all highway, the other return 1/2 trip was via country roads.
Acceleration & Top Speed were negatively impacted grately. I don't have a scan gauge, so I can't provide actual #s, but I know that my throttle was opened to a greater % and duration during acceleration as compared to the 12's, but I barely had it open to maintain the speed... I couldn't even get to 3,000 rpms on the highway @ WOT for 5-10 secs so I stop trying... No need since I could reach 70mph by 2,600. The highest speed I was able to reach with the 15's was 73.68mph WOT and not really climbing
With the 12's I had done the same (WOT) and reached 86mph (down hill
)
I did all my testing prior to fill-up, and filled up at a gas station about 1/2 mile away from the house... Starting tomorrow I will be testing the 15's and I should have gone through a tank by Thursday. Unless the change is drastically worse, I will probably run this setup for a few tanks and see what I really think about it.
SO... ANY BETS ON WHAT EFFECTS THIS WILL HAVE???