What's 100lbs worth?

[JeffYoung]

With all due respect to Earl, not sure this is a helpful thread. 100 lbs means so many different things to lap times depending on car, track, driver, hp, tq., temp, tires, etc.

That said, I run 50 lbs over to be safe and have not seen any significant difference in lap times vis a vis when I run without the ballast. I think however that 50 lbs probably means a lot less on my car given the torque. On a low torque car it may be more significant.

But the bottom line for me is a lot of lap records are being set by cars that are not even close to min. weight. I think that speaks for itself. Quit worrying bout the 50 to 100lbs and start worrying about the driving.

[Z3_GoCar]

With all due respect to Earl, not sure this is a helpful thread. 100 lbs means so many different things to lap times depending on car, track, driver, hp, tq., temp, tires, etc.

....
[/b]

That's too true Jeff. I bolted on 60lbs and got faster The hard top added 60 lbs to the rear and high up but greatly reduced drag that my top end was just so much better that it more than made up for the weight to accelerate, and with larger sway bars and urethane bushings in the sub-frame and trailing arms and proper toe in on the rear and it was much better, untill I swapped ends and went round. All because I couldn't keep up with a 400+ hp Firebird

[erlrich]

With all due respect to Earl, not sure this is a helpful thread. [/b]

Agreed

Don't know what I was thinking.

[dickita15]

The only real world hearsay I know about on this is from World Challenge with regard to rewards weight. It is often said that the extra weight has little effect of a single qualifying lap but greatly contributes to the tires going off over the course of a race. My limited time with my new lighter car seems to back this up. The heavy car went off a lot more near the end of a race.

[toddgreene]

The old British Car Racers claim that 100 pounds= 10hp of acceleration power.

Todd

[JeffYoung]

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

[erlrich]

Earl, hope I didn't come across as an a#$[/b]

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 .

[JamesB]

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.

[steve b]

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.

[Knestis]

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

[JohnRW]

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]

(note to self: write to CRB, ask for addition weight on ITB VW Golf III's)

[steve b]

(note to self: write to CRB, ask for addition weight on ITB VW Golf III's)
[/b]

[Wreckerboy]

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
[/b]

Emphasis mine. You are subtle, but good, Dr. K.

[Knestis]

Emphasis mine. You are subtle, but good, Dr. K.
[/b]

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

[ddewhurst]

IMHJ just about this entire topic is nothing more than a waste of time. Ya me, what the muck do I know.

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 about car weights.

[JeffYoung]

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.

[gran racing]

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!!

[JeffYoung]

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.

[erlrich]

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 .

Cheers.

[JamesB]

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.

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