Oedwards wrote:I've been thinking about this a lot and I just can not get my head around the fact that if the front is higher you cant transfer as much weight, and that raising the rear actually takes weight off the front.. It just seems against the rules of nature.
it's called gravity. Put a car on the scales and raise the rear and see where the weight goes
R.I.P. Brian Klocke, you will never be forgotten
Oedwards wrote:I've been thinking about this a lot and I just can not get my head around the fact that if the front is higher you cant transfer as much weight, and that raising the rear actually takes weight off the front.. It just seems against the rules of nature.
That's because what you are saying is wrong. Once again correct me if im wrong but...
The reason we stiffen and/or raise the rear suspension is to try to keep as much weight over the front wheels as we can to aid in traction. If you look at the fulcrum diagram earlier in this post wou will see that by raising the rear/stiffening it up you set yourself up for better weight transfer because you are putting more weight on the front wheels.
Along with that is why I find it hard to believe the jacking up the front suspension is a plausible idea. All you are doing there is moving more weight back initially. Sure you're car won't physically lift off the suspension more with it already raised up, but all added together you're still transfering the same amount of weight towards the back.
5 5
------------------------------- Normal car
^
7 3
------------------------------- Car with raised/stiffen rear <-------------- All cars on the starting line
^
4 6
-------------------------------Car with raised nose
^
3 7
------------------------------- All car when power is applied
^
That's obviously a very broad generalized idea but the principle is the same. If anything I would prefer to start with more weight on the front wheels initially because that is when you need the most traction.
Street-Legal 2003 Sunfire 10.58 @ 139 MPH
Ok so didnt preview my post and it completely screwed up my whole diagram. What those numbers represent are the "weight" on the front and rear wheels and are supposed to be on the tips of the dashed line. The little carrot should be underneath the middle of the dashed line acting like a fulcrum.
Street-Legal 2003 Sunfire 10.58 @ 139 MPH
Ok, I saw stiff rear/soft front. Really? In a FWD I suspected you'd want a very stiff rear/firm front. So, the front stays planted and prevents wheelhop.
This thread cracks me up. People trying to deny conservation of energy, others trying to describe moments of inertia using seemingly random qualitative descriptions...
Boosted2point4 wrote:Oedwards wrote:I've been thinking about this a lot and I just can not get my head around the fact that if the front is higher you cant transfer as much weight, and that raising the rear actually takes weight off the front.. It just seems against the rules of nature.
it's called gravity. Put a car on the scales and raise the rear and see where the weight goes
I'm curious as to where you think it goes... And what kind of bizarre wheelbase you have, or ridiculously accurate scales you're using...
Vitamin E (AKA Eddie) wrote:Ok, I saw stiff rear/soft front. Really? In a FWD I suspected you'd want a very stiff rear/firm front. So, the front stays planted and prevents wheelhop.
You want your front spring stiffness and shock 'stiffness' dialed in so as to minimize wheel hop. Period. This will vary with track surface type/profile, tire compound/temperature/profile/pressure, sprung and unsprung masses, torque output, ... It will be trial and error. Getting a theoretical value for this is literally impossible due to the nature of tire traction. You could get fairly close, but you'd have to take a LOT of measurements (and do a lot of calculations...vibrations equations are murder), and the values can change considerably depending on what track you're running at that day, or even the weather.
fortune cookie say: better a delay than a disaster
That's fine i'm just a big dumbie, I use scales from bed bath and beyond they are the best ones.....
R.I.P. Brian Klocke, you will never be forgotten
I'm amazed (like I usually am) that no one has mentioned anything about stabilizing the chassis by making it stiffer.
Get the twist out of the chassis upon launch and you'll have both wheels (that would be front wheels with lsd which is necessary for true racing) grabbing at the pavement on equal terms.
Also, springs along with a good stiff chassis will keep most of the weight transfer down to the point that the car will provide better times from less reaction to the shifts etc.
Having drag raced for years I could really feel a difference in the Cavy with all the chassis bracing I've done to the car. Less motion and smoother takeoffs (it's an auto for now) led me to beat my best 1/8 mile time the last time I tracked the car.
Nothing else was done to the car but to improve the chassis and lo and behold, I stayed on the threshold of my record with every run as opposed to being off my a few tenths previous to the work.
With even more work done to the chassis in the last year (short of installing a cage) the first thing I'm going to do is track the car once the tune is on and see how it fares.
I think it's going to be a win situation if my theory is right on the chassis being stiff.
Just a thought and something that always seems to get unnoticed by most when it comes to the Jbody.
Good luck to the OP and his quest to have a good drag car.
Misnblu.com
Newbie member since 1999
Thank you Dave and JBO! 
i am suprised that no one mentioned that either. i believe that you should have to first focus on making the chassis stiff and rigid but it seems as if you are trying to compensate for that buy dialing your strut/spring setup a particular way. now correct me if i am wrong, but if you were building more of a street/strip vehicle, wouldnt you want to brace the chassis to prevent flex which thus would play a huge part on weight transfer depending if it was done or not. now has anyone attempted in their drag car any sort of sub frame connectors or does this not play a large difference in a fwd drag car as compared to a rear wheel drive drag car?
also i just wanted to let everyone know that i have little experience with a drag car setup but the experience i do have was around a gentleman that wrote an entire book on drag racing suspension setup but all of the little experience i have was with rwd cars. so please if there is something that i am saying not making sense please let me know.
It does and there are some braces that you can add to your subframe that will stiffen up that portion of the car which is critical to great launches and keeping it stiff.
The K-brace which is quite popular is one of the best out there and like the front strut brace ties the strut towers together at the base of the strut towers.
I've also developed what I call a V-brace which ties the subframe to the frame rails along the rocker panel for further bracing of the subframe and rails.
There's the floor bar which again ties the frame rails together from inside the car and if done properly (people take short cuts with the installation) is another brace that solidifies the middle section of our cars.
Then there's the 4 point B-pillar brace which ties in the B-pillars at the upper B-pillar mounts and to the floor with triangulated bracing which would be similar to a basic 4 point roll cage but a cage isn't required.
I've been a hardcore chassis man with my Cavy and I can tell you that it's the best handling car I've ever driven and at the track, there's virtually no weight transfer (I don't exactly have alot of power - yet
) to speak of.
Every day I see people adding turbo's or superchargers to their cars and wonder why they don't do anything with their chassis.
I know not everybody is as hardcore as I am in building a 'race' car but any true tuner will realize that the chassis is the backbone of the car and without a good back, you're not going anywhere for very long or having adverse effects on the frame of the car..
Nice to see another advocate of the chassis work and how it can affect the overall performance of the car.
Misnblu.com
Newbie member since 1999
Thank you Dave and JBO!
agreed james. id love to see what pauls car could do with all you're braces installed.
Trailer Queen corvette wanna-be with 40 coats of wax and powdercoating that soaks in.
Jcavi wrote:I'm trying to get a an idea of the basic front and rear suspension setup for drag racing. so far it seems what Ive been finding is pretty straight forward. stiff rear with firmness all the way up. fronts set to soft. whole car lowered but with the rear slightly higher to shift weight towards the front. also tire pressures high in the rear and low in the front. of course all of these are general ideas with settings that need fine tuning. but do I have the genral jist of it?
If i were to answer this question I could provide great information. Same basic some designed for YOUR car. Simple questions like engine size - hp - manual or automatic - street tires or something else?
Every car has different issues. I always tried little baby steps. FWD cars can get hooked. I ran a few 1.8 60' times on street tires and an automatic. When you race RWD cars the issue becomes raising the front wheels. Then you develop ways to carry the wheels but keep the car straight. When you master that you can run high 6's & 7's in the 1/4 mile on 12" drag radials. In my opinion the best way to get the best answer when a question is asked is to incude DETAILS with the question.
rick king wrote:
I thought you were perma-banned or something?
fortune cookie say: better a delay than a disaster
