SCCA Solo C Street Discussion

[travisb]

Originally Posted by vroom4

You want to drive 30,000 miles and 20 autocross events on a 200tw?

Yes, please. I would also like to double the horsepower by changing the air filter.

Seriously though, that is why I asked about the life expectancy of these tires. Now I know, by your statement, that getting two years is probably not going to happen.

[vroom4]

We got 300 runs and 14000 miles out of our Z2.


After 200 runs they were SLOW and after 10,000 miles (and 200 runs) they were bald.

[mla163]

Originally Posted by vroom4

Weight doesn't matter in autocross...it defies all things you read...but I almost gaurentee you that you can just as fast with a 19 pound wheel as you can with a 15 pound wheel. (or tire, or whatever)


I can never spell gaurentee right...guarantee...firefox is mad.

I used to agree with you. But GRM did a test a recently where they compared lightweight wheels against heavier wheels on an autocross course and it did add up. rotating mass does makes a difference. They even ran a test with the same car with lightweight wheels and extra mass mass in the trunk vs the same car with heavier wheels (same car, same weight one with light weight wheels, one without)

It wasn't a huge difference Iirc. 0.1 to 0.2 s or so. But I will take it.

[vroom4]

Huh....can you try to find which month it was in....

[Cueman]

Originally Posted by vroom4

Weight doesn't matter in autocross...it defies all things you read...but I almost gaurentee you that you can just as fast with a 19 pound wheel as you can with a 15 pound wheel. (or tire, or whatever)

And you can go just as fast with 180hp as you can with 185hp?

I don't doubt that the difference is small... but where do you draw the line?

[vroom4]

Originally Posted by Cueman

And you can go just as fast with 180hp as you can with 185hp?

I don't doubt that the difference is small... but where do you draw the line?

In autocross, unless you are a national tour trophy contender....I drAw the line at a few pounds per corner . I see so many people worrying about every little car setup detail, then another person goes out and spanks them in an oem car with traction control half on

[Briankbot]

Originally Posted by mla163

I used to agree with you. But GRM did a test a recently where they compared lightweight wheels against heavier wheels on an autocross course and it did add up. rotating mass does makes a difference. They even ran a test with the same car with lightweight wheels and extra mass mass in the trunk vs the same car with heavier wheels (same car, same weight one with light weight wheels, one without)

It wasn't a huge difference Iirc. 0.1 to 0.2 s or so. But I will take it.

I vaguely remember that article. I got rid of all my back issues during a recent move, but what I took away was that a significant difference in wheel weight had a negligible effect during their test.

I couldn't find the article online, but it is highly referenced on various car forums and may be in the June 2011 issue.

[vroom4]

Originally Posted by Briankbot

I vaguely remember that article. I got rid of all my back issues during a recent move, but what I took away was that a significant difference in wheel weight had a negligible effect during their test.

I couldn't find the article online, but it is highly referenced on various car forums and may be in the June 2011 issue.

Yea that's what I remember too, the article concluded the exact OPPOSITE of what he just claimed haha. They basically were within under 0.1s

[toeout]

Talking in absolutes, yes the lighter wheels are faster. They have to be, laws of physics dictate that. But it's not just your lightweight wheels rolling down the course.

My takeaway from that article was that the biggest variable is the driver. I mean they had couple of runs where they were faster with the heavier wheels. Unless you are so super consistent ( basically a robot ) with your driving, it is very hard to turn the weight advantage into an actual faster time.

[vroom4]

Originally Posted by toeout

Talking in absolutes, yes the lighter wheels are faster. They have to be, laws of physics dictate that. But it's not just your lightweight wheels rolling down the course.

My takeaway from that article was that the biggest variable is the driver. I mean they had couple of runs where they were faster with the heavier wheels. Unless you are so super consistent ( basically a robot ) with your driving, it is very hard to turn the weight advantage into an actual faster time.

FYI: Im buddies with Andy Stach who probably runs in your region. Last year he probably ran an SM Silver STI with big ol hoozers on it.

[7thgear]

Originally Posted by toeout

Talking in absolutes, yes the lighter wheels are faster. They have to be, laws of physics dictate that. But it's not just your lightweight wheels rolling down the course.

My takeaway from that article was that the biggest variable is the driver. I mean they had couple of runs where they were faster with the heavier wheels. Unless you are so super consistent ( basically a robot ) with your driving, it is very hard to turn the weight advantage into an actual faster time.

technically the driver isn't the biggest variable.. it's arguably the only one.


The car is otherwise static, whether your own variance is +/- 0.3s, this will always be on top of the car's net potential.

Having wheels that in theory drop your time by 0.2s will always drop your time by 0.2s.


So the question is really only about finances.

[qoncept]

Originally Posted by 7thgear

So the question is really only about finances.

Disagree. 10 years ago I would have been much better off without adjustable dampers. Today I am (probably, historically speaking) better off without adjustable dampers.

[7thgear]

Originally Posted by qoncept

Disagree. 10 years ago I would have been much better off without adjustable dampers. Today I am (probably, historically speaking) better off without adjustable dampers.

well, to your own admittance you never really knew how to turn the knobies in the first place so that's empirically incorrect

had you taken the car to a rally shop and let them figure it out for you using shock dynos and what not I think you'd be very happy.

[qoncept]

Originally Posted by 7thgear

well, to your own admittance you never really knew how to turn the knobies in the first place so that's empirically incorrect

had you taken the car to a rally shop and let them figure it out for you using shock dynos and what not I think you'd be very happy.

"Rally shop" ? Is that like Midas?

I would guess the majority of people are better off without the adjustability. I see people turning knobs, spraying, adjusting tire pressures etc all the time who I'm sure would be better served just driving. It's a distraction and creates a moving target. But I'm sure none of us would succumb.