I'm sorry if you were offended by my little poke (but not that sorry) -- but I've gotten tired of re-posting my derivation of the actual number every time someone repeats some folklore based number like 4 or 10 or 20. Just as IntegraR0064 stated, if you work out the physics then for acceleration and braking, the absolute maximum multiplier is 2x for weight on the tread of the tire, and about 1.5x for weight at the rim of the wheel -- although I disagree that there's no multiplier in braking; the force may be limited by the friction of the tire, but that force still has to go towards slowing down the rotation of the wheel. I suppose if you lock up all four wheels, the multiplier goes to 1...but you won't stop as fast for other reasons.

I kid because I hope it will make people more likely to evaluate their sources and maybe do a little of their own research to confirm claims before treating them as true.

 

[QUOTE=Orthonormal,Dec 10 2010, 08:36 AM] although I disagree that there's no multiplier in braking; the force may be limited by the friction of the tire, but that force still has to go towards slowing down the rotation of the wheel.

 

Just saying Hi and throwing in my .02...

I bought an AP1 a few weeks backs that I am prepping for STR. I finished reading all 120 pages a few days after picking up the car

I have been racing an IS300 in STX for the past few years that has been a hoot to drive. Driver and car wise it finally became competitive locally last year but I decided to move onto something lighter and with more power so I chose to try out an S2000 in STR.


On to questions/comments.

The IS300 was/is fairly tail happy car on course so I feel alot I learned on that car can be applied to the S. Has anyone had any issues(or comments) running extremely staggered spring rates F/R like 750/500 or 850/500? I had to do a similar setup on my IS along with a weak rear bar, which required me to still turn down the dampening almost all the way down on the Koni's I had installed.


As for wheel weights, on my IS between stock/all-seasons and kosei/dunlops the weight difference was 6-7lbs each wheel and it was noticeable difference. Acceleration and braking were much easier with the race wheels/tires on(duh!), the car felt lighter/livelier. I plan on running TRmotorsports wheels on the S which I know are not the lightest but money is an issue.
I am not worried at all about some guy running wheels that are even 5-6 pounds lighter than mine, it's too small of a factor to really play into the big picture of things. Driver differences will be the bigger issue. Maybe in a few years when an S2000 setup gets ironed out lightweight wheels will be higher up on the list of needs to reach a "full prepped for the class" car. I just think the time and money would be better spent elsewhere.

 

What you view as belittling, I view as correcting misinformation before it gets out of hand, which I think is important on a forum dedicated to exchanging information such as this one.

Take your own situation as an example. Someone online declared that wheel weight savings are ten times more effective than weight savings elsewhere. They weren't called on it, so when you read their post, you believed it. Now you've sold your perfectly good wheels and are stressing over spending lots of money on a specific set of wheels that will provide minimal to no discernable improvement over the 949s. If only someone had challenged the original post before you read it, you'd be both richer and calmer today.

In your case, you happen to post a healthy number of interesting claims. Off of the top of my head, from the past few months:

• Reducing wheel weight by a pound has the same effect as reducing unsprung weight by eight to ten pounds
• Update / backdate is ok in Street Touring as long as you're changing to heavier parts
• Rear toe-out in an S2000 is a good idea
• Your favorite intake requires some cutting to install, so the SCCA should allow cutting to install intakes, because no one will take advantage of that allowance in an unforeseen way

When you post interesting claims, then you should expect to be challenged on them. That's not belittling -- that's just (I'm admittedly stretching the term here) peer review in an attempt to keep the quality of the information exchange here high.

Edit: Reworded to sound less belittling.

 

 

[QUOTE=PedalFaster,Dec 10 2010, 01:47 PM]In your case, you happen to post a healthy number of interesting claims.

 

^ stock bump stops?

 

From what Andy told me - the toe out on your car is really hindering its capabilities.

He was like: "Dave's co-driver is really really good, how he can possibly drive that car fast is beyond me. Put a better setup on it and he'll be kicking everyone's ass."

 

Yeah, at first we agreed about the toe out and dial it back a smidge (likely to 0), but later on my co-driver, Mark, did throw in the other possibility that we might have the rear a tiny bit too low causing us to hit the bump stops (that came with the the used set of TC Kline DA's). So we are not disagreeing with Andy's assessment just that there might be another thing to look at as well. Good news is that both changes are easy and cheap.

Mark is a very good driver and with my car finally getting down to minor tweaking here and there (and going on a diet... lots of pork on this car), he will be up there with you top guys. Also, factors in my personal life is going to allow me to go any f'ing event I want. With that being said, I hope to get more seat time at the bigger venues... (vs. only 3 times or so) before Nats. Unless the car breaks, 2011 is going to be interesting.

-Dave

 

There is a ~2lb difference between Hankooks (lighter) and Dunlops (heavier). 1st at Blytheville was on Hankooks, 2nd was on Dunlops, 3rd was on Hankooks. As is said somewhere, it is within driver noise. If robots were driving, shaving 2lbs per corner might show up. Since we are all human, well, an extra 15 minutes of sleep might prove more useful.

Personally, I like the Buddy Club wheels. I chose to go heavier and get two sets of 6ULRs so I could try different tires. Do what makes you happy, first and foremost.