sanford traction issues?

Chris Landi · **Joined:** Mon Mar 08, 2004 6:31 pm **Posts:** 579

Wes Eargle wrote:

Chris Landi wrote:

WHAT??!!?? I've been telling you this for 2 years! You can have a lot of fun during that first 30 feet you know. It's become my 'tire cleaning/heating ritual'.

Yeah, starters love being hit with gravel and water being spit out of the exhaust. :roll:

It's hard to tell if this is a valid point because you complain about a lot of things.

Starters: Am I breaking some autoX etiquette by launching aggressively?

Donnie Barnes · **Posted:** Thu May 04, 2006 1:03 pm

I think he must be giving you crap. You can start as aggressively as you like as long as you aren't posing an unnecessary safety hazard. Shooting gravel off your tires doesn't qualify as an "unnecessary safety hazard" that I know of. *shrug*

I spun all four tires on the STi at every launch. And I'd do it again.

--Donnie

Wes Eargle · **Joined:** Mon Oct 27, 2003 9:47 am **Posts:** 3683

Chris Landi wrote:

It's hard to tell if this is a valid point because you complain about a lot of things.

Ouch, baby. Very ouch.

Vincent Keene · **Posted:** Thu May 04, 2006 1:07 pm

Chris Landi wrote:

Starters: Am I breaking some autoX etiquette by launching aggressively?

Experienced starters (like myself) know who lauches how and step back.

As far as launches go, I'll say than in the AWD Turbo Talon it was a big deal. We could launch hard with no wheel spin and be haulin-ass very quickly. If we spun off the line (which was rare with R-comp 255s!) we were slower.

Now in the Miata, a little wheel spin off the line is a good thing, but not *too much*. Obviously if you are spinning, your forward momentum isn't as good as it could be.

Ever see a dragster smoke the tires and they thought it was a good thing?

Chuck Branscomb · **Posted:** Thu May 04, 2006 1:08 pm

MikeWhitney wrote:

I'm not convinced about the 60' times ... since the start lights are 10' away. How much of the time is between 10-60 feet and how much is in the first 10'?

Yeah, I was just thinking about this more at lunch, and I think the best way to look at it is that the criticality of the launch is an exponential function of the distance from the starting line to the start timer. In other words, taken to an extreme, if we put the start timer 500 feet down the course, the launch would be meaningless. If we put the start timer 12 inches from the starting line, the launch becomes extremely important.

So, yeah, you're point is clearly valid. I wouldn't doubt that the first 10' of the 60' time is probably 40% of the time to 60' even though it only represents 1/6 of the distance. The further away the starting beam is from the start line, the less the importance of the launch.

I was only focusing on the 12" at the start since that is about the maximum amount of rollout you can get at the strip (i.e. the difference between deep staging versus shallow staging). I went through all sorts of issues when I got a Gtimer GT2 a couple of years ago in terms of setting rollout versus measuring acceleration times.

I definitely agree thought that the further away the start timer is from starting line, the less critical the launch. No doubt about that.

Sorry if I jumped to conclusions...guess I was reliving an old conversation a bit. :oops:

Chuck

Chris Landi · **Joined:** Mon Mar 08, 2004 6:31 pm **Posts:** 579

Wes Eargle wrote:

Chris Landi wrote:

It's hard to tell if this is a valid point because you complain about a lot of things.

Ouch, baby. Very ouch.

Sorry, not meant to be a dig. Really. You are very 'vocal'..better?

MarcusMcRae · **Posted:** Thu May 04, 2006 1:18 pm

Wes Eargle wrote:

MarcusMcRae wrote:

Wes Eargle wrote:

Chris Landi wrote:

WHAT??!!?? I've been telling you this for 2 years! You can have a lot of fun during that first 30 feet you know. It's become my 'tire cleaning/heating ritual'.

Yeah, starters love being hit with gravel and water being spit out of the exhaust. :roll:

Don't worry muffin, I'll granny launch for you when you're starting. :kisses:

I turn my back to the car after letting AWD cars and Walter start. So what's there to kiss is ... :shock:

Nice.

MikeWhitney · **Joined:** Wed Aug 20, 2003 9:15 pm **Posts:** 4724

[quote="Chuck Branscomb]Yeah, I was just thinking about this more at lunch, [/quote]

Me too. I guess I have never given it much analytical thought, except my "gut feelings". I think I'm going to try to try to throw some numbers at it... If I come up w/ anything interesting I'll share it here.

Matt McGrain · **Posted:** Thu May 04, 2006 3:12 pm

MikeWhitney wrote:

Me too. I guess I have never given it much analytical thought, except my "gut feelings". I think I'm going to try to try to throw some numbers at it... If I come up w/ anything interesting I'll share it here.

I do remember seeing your M3 sliding sideways a little on the launch and remembered thinking how badly I want a rear-drive car. It almost seemed that you had to lift a little to keep if from sliding too much, but maybe the tires were just hooking up.

Launching a front drive car with R comps is sooooo uneventful. Can you say wheel hop?

Anyhow, I think the launch is critical especially for the AWD guys. I'll tell you what, watching the STi's go off is really a cool thing.

daniel bishop · **Posted:** Thu May 04, 2006 3:39 pm

Quote:

I'll say than in the AWD Turbo Talon it was a big deal. We could launch hard with no wheel spin and be haulin-ass very quickly.

I miss my 6200 RPM launches

... only a slight four tire chirp and snap your head back

MikeWhitney · **Joined:** Wed Aug 20, 2003 9:15 pm **Posts:** 4724

Matt McGrain wrote:

I do remember seeing your M3 sliding sideways a little on the launch and remembered thinking how badly I want a rear-drive car. It almost seemed that you had to lift a little to keep if from sliding too much, but maybe the tires were just hooking up.

[/quote]

I had one "good" launch of 4 on Sun. You probably saw one of my 2 "too much wheelspin" launches

But you touched on one interesting thing -- at some courses where there is a tight turn right after the launch, a little too much wheelspin can be a good thing to get the car turning. Or maybe I just enjoy driving like an idiot

Chuck Branscomb · **Posted:** Thu May 04, 2006 6:14 pm

Mike,

I ran some simulations with CarTest2000 which is a surprisingly accurate simulation program. I used the M5 as the example since I've worked with that car the most on launching and have the profile up to date in CarTest2000.

I set it up to do two different launches. The first one was pretty decent, resulting in a 0-60mph time of 4.8 seconds with a 60' time of 2.19 seconds. The second launch slipped the clutch a bunch more resulting in a 5.7 sec to 60mph time with the 60' time of 2.48 seconds. So here we have a situation where the 60' time is 0.29 seconds worse.

I'm not sure where this is heading, but note the speeds at the different distances perhaps. At 60' the car is going 36.37mph with the good launch and only 30.61mph with the poor launch.

I guess another way to look at this is what you mentioned earlier, the 10-60 foot times. In the good launch, the 10-60 foot time is 1.39 seconds while in the poor launch the time is 1.61 seconds. The car traveled that 50' 0.22 seconds faster with the good launch.

I'll try some other sims later tonight with an STi or other high power AWD car. Let me know if you (or anyone else) have any thoughts about the above. I love getting to the bottom of stuff like this -- hopefully I can learn something from this analysis.

Thanks,
Chuck

MikeWhitney · **Joined:** Wed Aug 20, 2003 9:15 pm **Posts:** 4724

Chuck Branscomb wrote:

Mike,

I ran some simulations with CarTest2000 which is a surprisingly accurate simulation program. I used the M5 as the example since I've worked with that car the most on launching and have the profile up to date in CarTest2000.

I set it up to do two different launches. The first one was pretty decent, resulting in a 0-60mph time of 4.8 seconds with a 60' time of 2.19 seconds. The second launch slipped the clutch a bunch more resulting in a 5.7 sec to 60mph time with the 60' time of 2.48 seconds. So here we have a situation where the 60' time is 0.29 seconds worse.

I'm not sure where this is heading, but note the speeds at the different distances perhaps. At 60' the car is going 36.37mph with the good launch and only 30.61mph with the poor launch.

I guess another way to look at this is what you mentioned earlier, the 10-60 foot times. In the good launch, the 10-60 foot time is 1.39 seconds while in the poor launch the time is 1.61 seconds. The car traveled that 50' 0.22 seconds faster with the good launch.

I'll try some other sims later tonight with an STi or other high power AWD car. Let me know if you (or anyone else) have any thoughts about the above. I love getting to the bottom of stuff like this -- hopefully I can learn something from this analysis.

Thanks,
Chuck

That's exactly the kind of analysis that I was thinking of doing! Very interesting, and it looks like a little more "time" is there than I would have guessed.

Anyone have a guess about how far it was from (a) the start line to the start light and (b) the start light to the first slalom cone? I don't judge distance well, but my first guess would be about (a) 10 ft and (b) 50 ft...

Wes Eargle · **Joined:** Mon Oct 27, 2003 9:47 am **Posts:** 3683

It was just under 9' and 53'6" respectively.

MartynWheeler · **Joined:** Mon Jan 02, 2006 9:30 pm **Posts:** 303

(...catching up with the forum...)

Guilty of weaving too. I had no illusions about putting heat in the tyres, just trying to get the crud off for the launch. The A3S05 is real hard to hook up on the launch on the cleanest of courses. As soon as the start worker gave me a "look" I suddenly realized that this was probably what was meant by "tire warming" and stopped doing it immediately. Doh. Won't make that mistake again.

Thanks to all the recommendations to use a pyrometer for pressures, by the way. What it mainly told me was that I wasn't driving hard enough to put heat in the tyres in the first place, and that contributed directly to me knocking oodles of time out over the day as I tried to get the readings up. Still haven't settled the front pressures yet, but the rears seem pretty definite now at 33.

Sanford was a great event for me. Between the hard numbers telling me I was not heating the tyres, and Vincent's "you're not looking ahead" at Laurinburg, I suddenly got respectable times. I know Jim would have been a whole lot faster in the afternoon without brake issues, but to get within (ignoring my cone :twisted:

) 3.3 seconds of even that time is pretty darned satisfying. Compared with 11 seconds behind Jim at Laurinburg, 5-ish seconds (including the penalty) at Sanford is like night and day. Thanks all for the advice!

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sanford traction issues?

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