What's 100lbs worth?

Earl, hope I didn't come across as an a#$, but as I thought through this and tried to answer your question (and I have put weight in and taken it out of my car, and our Miatas), I just hadn't really seen any provable coorelation between 25 and 50 lbs (admittedly not 100) and lap times.

In any event, hope your racing is going well.

See you SARRC/MARRS I hope.

Jeff
 
Earl, hope I didn't come across as an a#$[/b]
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Not at all Jeff, and I apologize if I appeared to be implying so. I was just acknowledging your statement of the obvious.

And I probably shouldn't be posting anything right after a 2 1/2 hour commute into work anyway :D .
 
Earl,

I was never trying to say you where the one needing to loose 100#, but like most of society im sure a 5-10# loss and regularly excersize might do you some good, it did for me!! Then having your car loose some weight at the same time is just a win win.
 
$203.08

:P
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I think I paid about $20 a piece from Walmart for the two 45 lb weights bolted to my passenger floorboard. Another $15 in steel and bolts/nuts.

The whole 100 lbs doesn't mean anything to most drivers argument is BS to me. If that were the case then why add the weight? Obviously it means something. We're talking a driver that is getting the most out of the car and what would 100 lbs mean to them. My guess is .5 to 1 second depending on the track. Even a crappy driver will have their acceleration affected.

David
 
I think I paid about $20 a piece from Walmart for the two 45 lb weights bolted to my passenger floorboard. Another $15 in steel and bolts/nuts.

The whole 100 lbs doesn't mean anything to most drivers argument is BS to me. If that were the case then why add the weight? Obviously it means something. We're talking a driver that is getting the most out of the car and what would 100 lbs mean to them. My guess is .5 to 1 second depending on the track. Even a crappy driver will have their acceleration affected.

David [/b]
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David,

The point is that while it obvioulsy means something, there are so many variables in what we do to put a number on it is impossible. AND, at the level that we run, without the elimination of the pile of vaiables (new tires every session, the exact same amount of gas/weight, same track and atmospheric conditions, etc), it's useless to event guess.
 
Anyone who has ran track days with and without an instructor in the same day should be able to venture a guess on this. I've been lucky enough to have a light instructor (150 lbs) on a few occasions and my lap times were about 1-1.5 seconds slower with the instructor in the car.

This was at SP main in a 135HP MR2. Not an ITA car, but it was same tires, same day, consistent temps., etc. And even with inconsistent lap times, you could still see the trend or take the average lap time, or compare fastest or slowest, it was still always in the 1-1.5 second range.

I doubt that the affect is linear, so I wouldn't say that 100 lbs. would be 2/3 of that, but I would still GUESS that 100 lbs. probably approaches a 1 second add to a lap time at SP.
 
I've had the opportunity at least 3 times to do back-to-back laps in the Golf, before and after pit stops to add substantial amounts of fuel (5-11 gallons, so call it 30-70 pounds), without changing anything else.

In all three, the car was qualitatively better balanced AFTER the stop than BEFORE and for the one where I checked, it recall that it went measurably faster after adding weight.

FWIW

K
 
In all three, the car was qualitatively better balanced AFTER the stop than BEFORE and for the one where I checked, it recall that it went measurably faster after adding weight.[/b]
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(note to self: write to CRB, ask for addition weight on ITB VW Golf III's)
 
I've had the opportunity at least 3 times to do back-to-back laps in the Golf, before and after pit stops to add substantial amounts of fuel (5-11 gallons, so call it 30-70 pounds), without changing anything else.

In all three, the car was qualitatively better balanced AFTER the stop than BEFORE and for the one where I checked, it recall that it went measurably faster after adding weight.

FWIW

K
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Emphasis mine. You are subtle, but good, Dr. K.
 
IMHJ just about this entire topic is nothing more than a waste of time. Ya me, what the muck do I know. :rolleyes:

Let's take a perefectly set up 1800 pound car with a Professional driver who can turn laps xx.xxx within one tenth of each other. Now let's add 25 pounds of weight to each corner of the car. That's 4 corners x 25 pounds = 100 pounds.

Do you believe with the added 100 pounds of weight the lap times will be equal to the first lap times within one tenth each other ????????????

steve b, I'm with you 100%.

If weight don't matter to speed make all cars weigh 2800 pounds. It takes a variable out of the famous forumla. There will be no more bitching :014: about car weights.
 
Guys, we don't disagree that weight makes a difference.

The problem is quantifying it. Yes, it makes a difference. No, given the variables involved, no one can say with certainity what that means in a vacuum for any one car.

That's all we are saying.
 
Emphasis mine. You are subtle, but good, Dr. K.
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Not intending to be sneaky there.

Point being - as Jeff mentions - that there are dozens of variables that interact to produce "speed" or "lap time," and weight is just one. IF (a HUGE if) we could control all of them then the influence of 100# becomes potentially measurable, and perhaps more importantly repeatable.

I experienced at least one situation where they were such that more weight over the rear wheels made that car (with me doing the steering) faster, rather than slower. It changed direction better (on those tires, on that track, in those weather conditions, that late in the race), allowing me to get on the throttle earlier, gain exit speed, and improve lap times. The additional mass actually made the car LESS BAD, overcoming something that wasn't optimal in the set-up prior to the stop - which more likely reflects reality than does some theoretical model that says "100 pounds will increase lap times by .3 seconds."

Pfiffle.

K
 
Earl, I've wondered about the same thing and with an even lesser amount of weight. I always come across the scales ranging from 30 - 50 lbs heavy because I'm too nervous of coming in lite. Et hmm, Jeff Lawton!!
 
Same here Dave. I go for at least 25 over to be safe. Losing a race or a good finish over 25 lbs makes no sense to me.
 
Gentlemen, thanks to all of you for your opinions, which is all I was ever asking for. I didn't intend this to become a long, drawn out discourse on all of the variables involved in determining the effect of extra weight on a car's performance. And I do understand just a little about the physics affecting performance with regard to weight, its affects on handling, braking, and acceleration, and the fact that each car will benefit differently from changes in weight. I was just hoping to glean a little extra insight from those of you who have been doing this for many years. I know opinions are worth exactly what you pay for them, but I have come to value the opinions of a handful of our members, and was only trying to tap into that resource.

I also fully realize that the extra weight is not even close to being the main factor in my struggle to move closer to the front of the field. Engine/suspension development & testing, and mainly driver development are all key factors in cutting my lap times, and I realize I still have a ways to go in those areas. I was merely trying to quantify a few of the pieces of the puzzle that I know are still missing, in an attempt to plan my next steps in the process. And before you say it; yes, I understand that attempting to quantify the areas where there is need for improvement, and then expect the effects to be cumulative, is not realistic so rest assured I'm really not living in a fantasy world :lol: .

Cheers.
 
Earl,

Do what I did and start your program with the driver. As soon as I started racing I changed my workouts from weight training with some cardio to cardio with some weight training and focus on my core. For winter projects if you know of legal ways to drop the cars weight closer to minimum weight then do so as long as its not rediculously expensive. If your consistent with your workout and eating habits you and the car will be in great shape for the 2008 season. :D

Next season work on your line and what the car is telling you (the reson I went through 3 different spring configurations this year.) Now I feel my car has the correct suspensio and alignment now I am working on the driver again and trying to stay consistently in the 34's and hope to break into the 33's and I know that is all me.

--James
 
Earl, get a respected top dog from your area to take your car for a ride. He/she may feel things differently than you do & point them out for you to feel/learn THEN make a change that you know you will feel. Some people need to make their changes bigger than the itty bitty change so that you do FEEL the change. It the change is over done, back er down some. BUT with the itty bitty change sometimes a person never feels the change therefore don't have a clue positive or negative about the change.

Even tho I like a friendly argue with Greg & Andy either of them could get the job done. :023:
 
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