Quote:
Originally Posted by mws
I found that if I were willing to put a non-staggered rim setup of 8.5" 20" forged rim on the front AND back (like the Japanese performance cars of the 1990s), suddenly, one more sticky choice was available. I could do this tire:
https://www.tirerack.com/tires/tires...omCompare1=yes
which is a decently track-day sticky tire, if I wanted. You keep the rim width in back (no one is really losing traction there, anyway), and get a 1" wider rim in front, which is the most embarrassing spot on the "rim width scale", for most. And can get turn-in. |
I am going to look into a square rim setup with 245/20s all around.
but....
this tire suggestion from me turns out to be a monumentally bad idea, now that I am resuming this train of thought and working on a custom-made lightweight set of forged rims and tires. These tires are BHPs. (Big Heavy Pigs). The stock 245 Bridgestones in back weigh 24 lbs, according to Tirerack.com.
https://www.tirerack.com/tires/tires...mpulse%20World
These RE050As I brought up, are indeed, very sticky BUT HEAVY!!! 30 lbs each. On a car with such HP challenges already, it is a horrible idea. (and they are only W rated, up to 168 MPH, more on that later)
I have started to look into tire weights, compared to the UTG (stickiness) rating. Having a hard time coming below 220, which is the Pirelli P Zero, which are also 24 lbs for a 245, and not just any P Zero. There appears to be a special one made for cars such as the i8.
Not this P Zero, it is 25 lbs
https://www.tirerack.com/tires/tires...mTireCompare=Y
you want this P Zero which is 24 lbs.
https://www.tirerack.com/tires/tires...mTireCompare=Y
there are also two different Potenza S001s, one is 28 lbs and Y-rated, for a 245 and the one we use is 24 and W-rated. Unless you feel the need to go 186+ miles per hour, the W-rated one is lighter and quicker.
also, I weighed my actual tires/wheels with a hanging scale, they were 45.5 lbs front, 49 rear. If the tires are indeed the weights tire rack.com says they are, then -21 and -24 respectively and you should have 24.5 front and 25 lbs rear for the wheels. It would be nice to get 20x8.5" forged wheels in the 18-19 lb range. I think that is possible (if you choose a simple spoke design). I had some VS Forged VS01s made in 20x9" front and 20x10.5" in back and they were a mere 20.2 lbs and 21.6 lbs (this was for a Jag). So, rims that are less wide, and similar style, might weigh less. Probably not more.
and talking this Square idea all the way through. Lets say we end up with 24 lb tires all around and 19 lb rims? That's 43lbs.
front was 45.5 and rear was 49. So the only big winner for weight savings, is the rear. The front electric motor is the one challenged in this whole equation. The last thing I want to do is make things worse for the electric motor, which this does not do..... but also, not spend a bunch of money and not really "help" the front, either. Losing 1.5 lbs of moment arm weight on the front to help the electric motor is not much. Maybe I should toss out the Square notion and use the 20/215 lighter tires in front, even on a slighty wider rim, if I can get someone to make a 20x8" forged front.
I am not doing this for looks or stance. I want to lose some weight. Turns out BMW already helped us out by selecting the lightest possible tires, so the only place to lose the weight is the wheels.