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Discussion Starter #1
After studying videos of X275 events, I've noticed that most cars rear ends don't seem to separate like I've seen in the past..

My question is..
Are they running less anti squat percentage ?? OR... Are they running more rebound dampening in their rear shocks ??

When they leave now days the rear seems neutral.. Where in the past the rear would drive the tires down and the rear body up..

Am I missing something..
 

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Old X275 cars and new ones are two totally different things. Even some that are "Stock" suspension have replaced/relocated frame rails, torque box locations much higher than stock, damn near as many instant center combos as a Pro Mod and shock technology that has more dampening capabilities than a Pro Mod runs. Sub 1.00sec 60ft times on good track prep. Top 10 X275 cars are as refined as any new Pro Mod. Just my $0.02
 

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I'm interested to know the how's of them making a 275 tire'd door car go sub 1.00's. That's some impressive shit.
 

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Discussion Starter #5
Some of the "suspension experts" are saying that a good drag radial car needs 4 to 6 inches of rear shock travel.. So that on the hit, the suspension tries to smash the radial into the track.. And lift the rear up, which causes the weight of the car to be transfered into pushing down on the tires.. Instead of using the cars weigh to compress the rear springs and shocks..
 

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Its a literal balancing act that has now been refined in many of the top cars to only use as much travel as required to keep front down and maximum force to move the car forward as efficiently as possible. Its really just the opposite of what we have known for 50yrs, if the car is going up its not going out. Any wasted motion over-rotating the car is taking away from the 60ft time. I think some of the advanced torque management features in certain ECU's has gone a long way to improve this as well as wheelie control. Teams are able to run much closer to the edge of traction limits and wheelstanding while improving not just 60ft but overall ET. I do have a couple buddies that run no TC and routinely go 1.13 - 1.16 60ft on 275 Pros on average TNT track prep. Both have run the same cars for several years and put their time in as well. No big secrets, just hard work and determination.
 

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I think the key to this is a low CG. A higher car will need seperation. A lower car doesnt need as much to keep it from doing a wheelie.

Then it becomes an issue of having a very narrow window between doing a power wheelie and spinning.
 

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Discussion Starter #9
After replacing my upper and lower torque boxes.. This guy convinced me to take my wheelie bars off.. He explains his theories of suspension settings in a plain easy to understand way..

 

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Discussion Starter #12
Thanks alot .. That is a very good article.. That's the kind of stuff I like to read..

Here is what my man (Rod Shop Rob) has to say about stuff that's related to some of what that article was saying..

 

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There has to be some separation to keep the front end down. If you aren't seeing any separation it's because their shit is dialed in! This is how it was explained to me by Ron Santhuff at SGMP one year. As the power is applied to the car, the rear shocks compress, applying weight to the tires, the front end rises shifting the weight to the rear. The rear shocks must extend at that point to keep the front from continuing to rise and gives the rear tires more force to push the car forward. Once the suspension is set up well, there isn't as much travel on a well prepped radial track. The guys who are really quick have their suspensions dialed in so well, it appears to the naked eye like nothing has changed but the shock sensors tell a different story.

You also might be shocked at the SLR some of the fast/quick guys are using.
 

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I think the key to this is a low CG. A higher car will need seperation. A lower car doesnt need as much to keep it from doing a wheelie.

Then it becomes an issue of having a very narrow window between doing a power wheelie and spinning.
This is very true, it's like trying to balance a ball bearing on a razor blade.
 

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Discussion Starter #15
You also might be shocked at the SLR some of the fast/quick guys are using.
Lay it on me.. Let me hear what these guys are running for starting line ratios ..
 

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From what I have seen work and still need to limit power I would be willing to try it in high gear if the clutches and converter could take it. I may have that opportunity when I get the Bruno-Lenco car done. The ratios I have in it are 1.56/1.25/1.00 and it is possible to launch or shift in any order I want or not at all. I have seen a 1.35/3.60 setup still try to wheelie at the top of low gear on a conservative tune-up with 56% front heavy weight bias. This is not a refined setup but not out in left field either. 4.30's with mid teen 60ft times on 275 Pros.
 

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ive tried everything on my car from 4.8 to 6 its only faster with the taller because it does not run out at the other end.. got one car in the 7s and it works fine... been 1.03 on our average tracks...
 

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Where does power management come into play when it comes to slr's? Is there just no way to pull enough power with too high of a slr?
 

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When a combo has enough stroke to make big torque at launch power management in one form or another is going to come into play. Whether it is timing, boost control or a combination of the two I have not seen a car geared for correct finish line RPM that has enough SLR to launch or make the run unimpeded by some form of power management. My customer with the "little" 363 SBF(6.07SLR) can launch with all the boost it can make (~24psi), ramp it up to 40psi in about a second and 90% of the time it will go right down the track with all the power it can make. My buddies with the 532 BBC Mustang (4.86SLR) can't launch with more than 5psi and it still tries to power wheelie on a decent track or chatters the tires on a poor surface. Two completely different setups but the engine's power curve makes all the difference. I think we could launch the BBC car in high gear but we had to add gear to get the SBF to run as good as it had before with a 5.52 when 1st gear(and converter) changed from 1.80 to a 1.48 1st gear. It ultimately went quicker/faster with the new setup but it was more like a MOD motor in that the setup has to be perfect and you have to beat the shit out of the engine from staging to finish line for it to run the numbers its capable of. Changing it to methanol also played a big roll in being able to run the times it has run. Hope this helps everyone understand the balancing act it takes to run these kind of numbers.
 

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Discussion Starter #20
As most of you probably know, we had the nmca / nmra Super Bowl of drag racing this past weekend.. Here at my home track in St Louis..

Most of the racers are real friendly guys, that will answer any question you have about their cars.. They want to talk about their cars..

I was talking with one of the top "Renegade" class racers.. He ran on 275 radials with a small block Ford (8.2 deck) and a class specific 75 mm turbo.. I remember one pass he made that was like a 4.80 @ 148 mph.. If I remember correct..

When we were talking he mentioned that when he ran the quarter mile he used all three gears in his transmission with 3.70 rear gears.. But for the eighth mile he leaves with a 1.48 second gear, and a 4.56 rear gear.. At the time I didn't think much of his starting line ratio.. But it was pretty stout.. But he made it work.. He said with the three speed he would leave at 4000 rpms.. With the two speed he would leave at 4500 rpms..
 
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