Chassis tuning help

[appleby66]

Need opinions on launch please, 68 charger, 3350 with driver, ladder bar set parallel with ground, QA1 singles in rear set on 2 clicks from full soft, dbl in front set on 2 rebound, 10 comp. 440 688hp, 620 Ftlbs. Launch on transbrake 3600rpm and it likes to spin, tried lowering tire pressure and no difference, tried raising and still no difference, tires are 29.5 10.5 m/t et drag at 15 psi. Hooks well on foot brake. Possibly hitting tires too hard on transbrake.http://m.youtube.com/watch?v=WBGRDKZsQsw

 

[Hemirunner]

Is the front end coming up too fast, topping out and unloading the rear tire?

 

[appleby66]

Ya I'm thinking so. When I launch on foot brake it launches fine and hooks. That makes it so the front end doesnt come up so fast. So maybe ill try tightning the front up on transbrake. Racing this weekend so I will see. Probably going to tighten the rear to. Might be basketballing the tire. I have a fresh set of Hoosiers to test out as well. Thanks for the input.

 

[Herr_Poopschitz]

Kinda hard to tell, but it looks like it's spinning from the get-go...not just once the front end tops out. Better video available?

 

[Cranky]

Looks like the front end is coming up a but quickly and topping out but like Herr said, the vid isn't the greatest. You have a lot of power for the size of tire so you might need to soften the hit. Can you lower the rear any? Have you scaled it yet? You might be surprised at how much of a difference just 1" of ride height can make in your front to rear weight bias. I had a similar problem with a car years back and tightening up the front shocks and lowering the rear did the trick.

 

[appleby66]

Here's another video in 500fps. Might be able to see what's going on now. http://m.youtube.com/watch?v=hNgRpwuaOHU

 

[Hemirunner]

It plants the tires hard but doesn't hold them there. The front comes up then stops and that's when it spins more. I would start by tightening up the front shock extension to slow the rise a little, then tighten up the compression to hold the front up once it's there and see how the car responds. It's transferring the weight to get up on the tire but not holding it there.

 

[khryslerkid]

What rear gear do you have?

 

[Mr.SpeedFreak]

Sorry, off topic but how the hell did you get down to 3350?? Very cool and I'm taking notes on the launch convo haha

 

[benno440]

http://www.raceglides.com.au/files/fourlink-ladderbar-tips.pdf

might help a bit

 

[SUPERSTOCKRACER]

how much tire pressure? you need to tighten up the rear shocks a bunch more , so it can plant the tire harder. You can try tightening up the front if that doesn't work a few clicks.
Also it looks like your sidewalls are shot on those slicks. I get 40 passes out of mine and they are junk after that.

 

[appleby66]

Thanks for the replies. Ya I run a dana with 4.56 gear. The tire pressure was at 15lbs on this launch. I have a new set of Hoosiers to try out along with a set of proper size rims. I was running 8 inch rims on a 10.5 tire in the vid and ya it was killing the sidewall. Racing this weekend so ill tighten up the *** end and see what results I get.

- - - Updated - - -

The car is gutted with a 8.50 cage and aluminum dash. All steel body with glass hood. I put it on the scale and I was very surprised at the weight. That was before I installed a set of alum heads as well.

 

[Mr.SpeedFreak]

Damn that's awesome, mine won't be gutted but I'd like to get it down around 3500 if I can. I've read the curb weight stock is supposed to be around 3,800 but I don't know how true that is lol

 

[appleby66]

Ya that shouldn't be a problem with getting down to that weight. I'm not to sure what curb weight was. Wouldn't surprise me if it was 3800.

 

[SUPERSTOCKRACER]

15LBS. if that's a bias slick is a little oo much air pressure. I run 13 lbs. on a good track and 12.5 on a marginal track. you're spinning because of that pressure. hope this helps. don't tighten up the fronts, tighten up the rears some more.

 

[appleby66]

Thanks For the advice. Ill drop the air pressure and tighten the rear shocks and see where that gets me.

 

[Mr.SpeedFreak]

Ya that shouldn't be a problem with getting down to that weight. I'm not to sure what curb weight was. Wouldn't surprise me if it was 3800.

Yeah I'm hoping, the lower the better haha. I've already started a little weight cutting and have a lot more planned out, and at some point I'd like to get a 'glass hood and take a shot at making my own cf decklid. Post an update video next time you run with the lower tire pressure and tightened shocks, looking forward to seeing what you run!

 

[womanator]

I run 7.5-8 lbs of air in my slicks.