Torqin, Your noticing the car “jump” is what I’m onto and pursuing. I tried making bar and shock changes for this reason and got nowhere. As far as tire pressure is concerned, I’m hearing you. I have never ran less than 5.2 in my life, with any tire… but with that said I have also never ran a tire with this type of sidewall construction either. The theory of going lower is to reduce bite, I get that and have seen it work before. It just seems like a compromise you shouldn’t have to make. I would prefer adding pressure to add bite....thats a better problem - lol.
Jenavet, Looking at the flash point, I wouldn’t think so, pretty solid at 54-5500 / purpose built NOS 10”. It sticks for about a quarter of a revolution then the entire sidewall is wound up and problems begin. I haven’t compared FPS and the time line but in quality slo-mo you can see stuff that you cant see on this youtube clip. You might be able to notice the short patch before the chatter marks on the track. The SLR may be an issue, still using 7.74...not great, but I dont think its the core problem....seen many of these work without this significant of a problem .
BJ, I hear you on the WB and trimming it down, but really want to use all it has. I hated the W/B on the last car, just a PITA and also have seen the same chassis as mine go 4.10s without. I started @ .100, then .01 and then .000 trying to get it on the tire (all combined with the other changes), along with increasing the spread (was only shooting 300 and very safe at that, so probably more like 250), like I said, was getting desperate and hoping if nothing else it would go the other way and I could back into a good set up from there.
GPX7903, the tire is a 3191/X8. I don’t know yet, hoping for 4.20s but would settle for 30s, just before this pass they had open time runs and it went 4.66 on motor, 1.06 and smooth as glass. This video was the first NOS pass ever. Prior to this I went out on a test and tune night and made two hits on motor but the track was real loose, too loose for any tuning - good for scrubbing new tires but that was it.
I'm going to try a big swing down in spring rate and hoping Penske will agree that the stack on the compression side needs tweaked....shock is in the mail now. I'm not a human shock dyno, but the compression side didnt seem near as sensitive as I feel it should have been from midway through the lower range....we'll see.
Keep us posted Jerry, your headed in the right direction IMO.
|DRR Top Comp
Absolutely, the same tire that worked great on my 4 link altered does not work as well on my Front Engine hardtail Dragster. I have tried a bunch of things and it is getting better but still not quite there. My car runs same but it is not hooking as good. My next move is to try the stiff sidewall. With the hard tail my tuning options are more limited than a 4 link type rear.
Like Jerry Kathe maybe sometimes we have to try things and see what works and what does not. Since that tire works so well on other similar cars may be something like a loose or binding rod end? Bad shock?
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The 3191 is a fantastic tire, they just take 4-5 runs to break in. So you may have been fighting that a little also.
I think your headed in right direction with shock/spring. 5-6 tire psi is where it should be. What spring rate did you have? What brand car?
I have a 4.5Xs dragster that ive sprayed to go high 4.30s-low 4.40s with 3196 and 3191.
gxp7903, The spring was a 400, the Car is an American 242"
that seems like too much spring too me
honesty is the best policy,insanity is a better deffense
1.036, 6.16@ 224
Is this really Ed?????
Na, can't be, no facts are listed!!!!
First I'm hearing or seeing about an issue.. Now if your changing from one tire to another or it's a brand new car, can it take a few runs to figure out what makes the car happy, sure..
Are you sure you were looking at the right tires?
Mickey Thompson Tires
330-928-9092 X 3142
new 3191's this april. no issues.
Can you post pictures of your current bar setup?
So is the solution here to dead hook the tire or slip it off the line?
Foxtrot Juliet Bravo
Provide more details of your combo...
But I will say this, you have the right idea to video the tire in hi-def slow-mo! You can see much more than what just a data logger shows you. And I would bet you that all the shock and 4 link adjustments aren't going to fix it. In order to give the tire a chance here, you need some controlled wheel speed early enough to keep the tire from running itself over and you will likely never get that without a wheelie bar! Many have no idea what a wheelie bar is really for! You need to use it to unload the tires enough to reduce bite and create wheel speed to keep the tire from running itself over!
BTW it don't matter what name is on the sidewall of the tire!
With no wheelie bar the Only solution is to gently drive it up on the tire. Even with a wheelie bar this power level would be a challenge to put on the tire at the hit
Well, I agree. Except for the faster breed of car today, most should be dead hooking. Recent decades has brought us data logging and a host of adjustments we can make. So we are aware now of traction issues, but not always wise to how to correct them. And of course being drag racers, we all want to go faster, and more is better. And wrinkled tires mean traction. So when we see that it is hooked at the line but unhooked 5 feet out, we don't make the conclusion that it isn't what is happening 5 feet out that is causing our problem. It is what is happening at the hit.
Some tires are way more forgiving for many combinations. But many tires will work where they are not working right now. Over tiring a car is inviting problems IMO. Folks put steam rollers on, and say they just want to be consistent, then murder that tire at the hit because they figure they have all the traction they could ever need.
So if you want it hooked 5 feet out(or so), don't crush the tire at the hit. I am ultra guilty of finding myself hitting the tire harder than I should, and have to remind myself, there is a price to pay for crushing the tire, if you don't have the power to back it up 5 feet later and keep that tire planted.
We can tell a lot from data, wheel speed, shock sensor. But the best way to see if it is unhooking is with video. A shock sensor can show no compression happening, but the rear of a light dragster is simply rising on the rim, not moving the shock. You need all three tools.
The fine tuning tools for not crushing the tire are tire pressure, shock extension dampening, and two step rpm. To keep the tire round, more pressure, more dampening, and less rpm.
The big guns are 4 link adjustment and converter selection. There are some 4 link setups that will never allow you to go more gently off the line and converters that will kill the tire regardless.
And of course, more power. You can hit the tire hard if you can keep it planted. So make more power and torque early, and that can also help fix the unhook problem.
Very high powered bracket cars are a different animal. If you can't dead hook because of the power level you are at, none of the above applies. But there are dead hooking cars going deep into the 7's and having nice 60' times. So high hp to me is 6 second big block cars and low 7 small block cars. (weight difference in the rear)
Foxtrot Juliet Bravo
I had a problem with a new set of 3186's on a brand new super comp car last October. The car went hard left every time i let go of the button. I added 2 flats of pre-load and same thing with 5-6 psi. I bolted my big bubbas on that were on the other car and set the bars back into neutral. The car went 4.40 on a string and made it to the semis.
I called MT about the 3186's and they offered me a new set. The 3186's I had never would come in. They were as slick as my hardwood floors. The 3186 tires had 4 attempted passes and we did about 6 super long 330' burnouts and the 4th run still was no good. I have a brand new set on the car, but waiting on the new engine and should go back out and try them again in 2-3 weeks. Seems several people runs this tire with no issue.
what I'm wondering at Big Steves age why is he touching babies bottoms?
Quick update, made a minor shock change and a huge spring change that I was able to test Saturday, car has never been so smooth or aggressive down low. Picked up 1.5 numbers in the short times on a screeming hot track with horrible air just on motor. Very happy...now to get after it
[QUOTE]Originally posted by Jerry Kathe:
Quick update, made a minor shock change and a huge spring change [QUOTE]
Care to share what those changes were? Always interested in how certain chassis adjustments effect performance...
DOES YOUR IDEOLOGY ALLOW YOU TO EQUITABLY APPLY STANDARDS OF ACCOUNTABILITY OR DOES IT PROMOTE THE PRACTICE OF HYPOCRISY?
No, not at all, keeping in mind circumstances vary....lol.
So I found the spring was really never the correct rate, but it worked when I really was not chasing et and only bracket racing....little disappointed there, builder suggested 50 psi less , so I went 100. Yes...100lbs less, from 400 to 300.
I sent the shock back to Penske (cant say enough good here) and had them take a few stacks out of the bump side for a little more sensitivity, took a random guess at both sweeps and clicks, put the bars back where I felt they should be and let it eat....didn't touch it all day.
I never really get the opportunity to test, so I entered a local Q16 race and ran it on motor only, was quick enough to get in without the bottle (4.63) so used it as a race/test session.
It was good on motor before but MUCH better now, if I can I will upload some before and after video
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