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Revolution Is My Name
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Discussion Starter · #1 ·
I'm running a traction limited class. ET Streets 28x12.5 on nitrous. Has anybody else had this problem?

When the power comes in tires smoke and front end falls.

 

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Sounds like the rear is unloading :smt017
 

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I'm running a traction limited class. ET Streets 28x12.5 on nitrous. Has anybody else had this problem?

When the power comes in tires smoke and front end falls.


How tight are the rear shocks?
 

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Revolution Is My Name
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Discussion Starter · #4 ·
How tight are the rear shocks?
Shocks set at 4 or 5.

So how does it unload if all the weight is on the back tires?

As far as I can tell from the pics and vid, when the launch retard starts getting close to 5 degrees the engine over powers the tires even with the front tires off the ground.
 

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make sure shocks arn't toping out seen it happen a bunch on leaf cars and possibly slow front shocks down maybe traveling so fast it jolts truck when hits travel limit even though tires in air couple things to check there
 

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To make it simple, your overpowering the tire. There are several thinks that can add or detract from this.Two things we do know is you are transferring all weight possible. We also know you can not upgrade tire, because of tire rule. Unless you can increase diameter. That leaves power value and optimizing traction. Either too hard or too soft in spring/shock combination can effect compliance of tire to track. Either too much or not enough air pressure can hurt compliance. With these optimized you have the power thing to look at. You have the tune of engine to work with, although we never like to throw anything away we don't have too. You will notice the cars with lower end torque leave at lower RPM to diminish the high torque values some. This leads to discarding extra in the drive train. Along with slipper type clutches we can soften converter some. There is also the gear used in launch mode. Higher numbered gears increase torque on contact patch and lower numbered gears decrease torque.

I guess the first place I would look is rear suspension travel. You would like to have 2 to 3 inches of travel at most. Nothing will disturb your tire compliance more than suspension bottoming or toping out. The second thing would be tire pressure. You can't use what your buddy runs, each car wants it's own, specific to power, I/C, weight and track. Then go to power issues. You can lower launch RPMs to get under torque curve long enough to get wheel speed. You can as you stated take ignition out of it. You can restrict the air/fuel flow. You can give extra up in heat from clutch or converter. You can change value from gear change. Once you have problem resolved, go back to tire pressure and check for best pressure.

Just think how good we have it now. Back in the day you could peddle it and slip the clutch till you made belly button lint of it.
 

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Shocks set at 4 or 5.

So how does it unload if all the weight is on the back tires?

As far as I can tell from the pics and vid, when the launch retard starts getting close to 5 degrees the engine over powers the tires even with the front tires off the ground.
I had the same problem with my Camaro. The front would lift, then the tires would start smoking. Found out that the rear shocks were extending too fast after the hit and shoving the weight forward.
 

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I had the same problem with my Camaro. The front would lift, then the tires would start smoking. Found out that the rear shocks were extending too fast after the hit and shoving the weight forward.

So you tightened the rear shocks and it got better??? What did you do to stop the spinning???
 

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So you tightened the rear shocks and it got better??? What did you do to stop the spinning???
Combination of tightening the rebound and lowering the launch RPM. I ended up getting rid of the car before I could get it dialed in perfectly.
 

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Spinning

To get mine to quit spinning like that, I had to have someone on here to help me with an rpm limiting map for the ignition. But mine is a radial car....if that makes a difference.
 

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Here is what it looks like before the tires spin.
If that is all the higher it gets, then you cannot say that the lever is high enough to put the weight on the tire and hold it there. You dont have enough hit in it to add the kind of power you have in the N20, looks like you have limited the front end and that may be unhooking it. You could go progressive or delay it and get the front up a little higher before turning the hose on full blast.

Any limited tire cars do not want to see a sudden shock at the end of travel like a hard stop travel limiter or shock topping out.
 

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To get mine to quit spinning like that, I had to have someone on here to help me with an rpm limiting map for the ignition. But mine is a radial car....if that makes a difference.
Did the dots help you? Have you tried it yet?
 

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Revolution Is My Name
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Discussion Starter · #17 ·
If that is all the higher it gets, then you cannot say that the lever is high enough to put the weight on the tire and hold it there. You dont have enough hit in it to add the kind of power you have in the N20, looks like you have limited the front end and that may be unhooking it. You could go progressive or delay it and get the front up a little higher before turning the hose on full blast.

Any limited tire cars do not want to see a sudden shock at the end of travel like a hard stop travel limiter or shock topping out.

Talked to Cal-Tracs this morning. Told them what changes I have made. The front end is 235# lighter than it was the last time I checked the front end travel. I know I don't have enough. I'm gonna lower the front to get more travel. Hopefully that will allow the front to get up better.

I'll back down the N20 and hit it straight off the brake.

If that dosn't work I'll take off the QA1 Coil-over conversion and put back 4 banger springs and 90-10's.

Thanks for the tips!
 

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Ahhhh the old coil over conversion they never have the proper spring rates, LOL I prefer the Moroso trick spring and a 90/10 or a good (not comp eng.) adj shock
 

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Did the dots help you? Have you tried it yet?

Yes, made a good bit of difference, went from spinning the tires as soon as the front end came off the ground to carrying the front end about a foot and a half to the tree. I feel I can still bring the dots in a little more. Of course that's kind of a slow and easy trial and error process. It went a best of 1.39 the other night.

We have another race this Friday, going to see if I can get them in a little tighter and maybe put a little more power down earlier to get the front end up further, and keep it in the air longer. I would like to get it down in the 1.36 or lower range.
 
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