Hope taller tires won't hurt pinion angle too much

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furrystump said:
So, without changing how hard you launch and it spinning instantly. I like more tire. I would just watch for more body separation and or a change in how the front tops out.
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With the shorter tires and leaving off idle it pulls about a 12" wheelie when it hooks good. I expect that to be less now but I don't care if I can get it to hook at tracks with bad prep. Also new tires are softer compound so may get away with shorter burnouts. Most of this will be answered this weekend at Texas Motorplex.
 
Test n Tune went well Friday night. The taller tires did slow things down a little but it hooked every time. No vibrations. Cold front moving through. By the next race the air will be much drier and cooler so hoping for consistent e.t's .
After the last race I had to replace the starter and a head gasket, but it all worked fine Friday night. Fel Pro head gaskets are only making it about a year, so I'm getting a set of Cometic MLX Head gaskets the next time I have it out to freshen it.
 
In your quest for consistant 60 ft, i had excellent results by launching at a low throttle setting using an ACD co2 throttle controller. When i graphed out my throttle position at the hit, i leave at 4000 versus a stall of 6200. That throttle controller takes .05 to open fully, then add a whisker of time for the air to get to the cylinders. Basically is really lessened the "hit" for the first few inches, dramatically reducing the violence of the hit. My dart has a 11.17 SLR, 980 hp and 2900 lbs with short 30 inch ladderbars , Afco big gun rear shocks to deal with all that torque. My 60 foots have been spot on within .002, going 1.224 to 1.226 same day.
The point of this info is to show how much that softer first few inchs of launch helped my dart. It used to smack the 66 inch long wheelie bars hard, then spin, and only go 1.27 or so 60 foots. The one thing it did change was my delay box setting had to be reduced by .05 for decent lights.
There are a lot of ways to skin a cat. If you still have 60 fts varrying more than .002, maybe trying to soften that initial hit will pay big dividends like it did for me
 
gregsdart said:
In your quest for consistant 60 ft, i had excellent results by launching at a low throttle setting using an ACD co2 throttle controller. When i graphed out my throttle position at the hit, i leave at 4000 versus a stall of 6200. That throttle controller takes .05 to open fully, then add a whisker of time for the air to get to the cylinders. Basically is really lessened the "hit" for the first few inches, dramatically reducing the violence of the hit. My dart has a 11.17 SLR, 980 hp and 2900 lbs with short 30 inch ladderbars , Afco big gun rear shocks to deal with all that torque. My 60 foots have been spot on within .002, going 1.224 to 1.226 same day.
The point of this info is to show how much that softer first few inchs of launch helped my dart. It used to smack the 66 inch long wheelie bars hard, then spin, and only go 1.27 or so 60 foots. The one thing it did change was my delay box setting had to be reduced by .05 for decent lights.
There are a lot of ways to skin a cat. If you still have 60 fts varrying more than .002, maybe trying to soften that initial hit will pay big dividends like it did for me
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Thanks, but I footbrake and leave at idle.
 
We probably need to see some videos of your launches, that would go a long way to be able to see the car in action. Gregsdart has the correct idea about a little softer launches too. If you haven't done it already, you might want to get the car up on cribbing so it sits at ride height and do some triangulation measurements. You may have the rear axle not square and true on the chassis, the frame rails may be tweaked a bit, or any of a number of other things. My former partner and I ran a Super Gas car and never understood why the car was so violent. We were told to check triangulation, and sure enough the rear axle was not true and square to the chassis. We corrected the problem and the car was a dream to race afterwards. Mine is just an example, you may want to experiment with rear tire pressures also. We used to go to some sketchy tracks for T&T before National or Divisional races, just to see if we could make the car launch correctly. I had another friend who broke a tie rod end on a launch and claimed that he only "brushed the wall". I went over and we triangulated the car and found out that he had wrinkled to left side subframe. It wasn't obvious until to got under the car. He had a body shop sponsor and took it to them and the wrinkle caused the right side of the car to 1/2" out of square. We don't know the history of your car, so we can only speculate as to what may, or may not be the problem. Good luck sorting the car out, I know it can be a PITA.
 
I haven’t raced in years but maybe bringing rpms up to close to stall will help in loading the tires to get more bite ? My thinking is the stabbing it from idle might be equivalent to dropping the clutch at whatever your stall speed is .

This is me just thinking out loud.
 
mbaird said:
Please explain this to me . Maybe I am not visualizing this correctly?
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100% agree, I was miffed for a second too. Taller tire will change the pitch of the whole car, drive train included. An altered rear suspension would change things.
 
Demonracer said:
We probably need to see some videos of your launches, that would go a long way to be able to see the car in action. Gregsdart has the correct idea about a little softer launches too. If you haven't done it already, you might want to get the car up on cribbing so it sits at ride height and do some triangulation measurements. You may have the rear axle not square and true on the chassis, the frame rails may be tweaked a bit, or any of a number of other things. My former partner and I ran a Super Gas car and never understood why the car was so violent. We were told to check triangulation, and sure enough the rear axle was not true and square to the chassis. We corrected the problem and the car was a dream to race afterwards. Mine is just an example, you may want to experiment with rear tire pressures also. We used to go to some sketchy tracks for T&T before National or Divisional races, just to see if we could make the car launch correctly. I had another friend who broke a tie rod end on a launch and claimed that he only "brushed the wall". I went over and we triangulated the car and found out that he had wrinkled to left side subframe. It wasn't obvious until to got under the car. He had a body shop sponsor and took it to them and the wrinkle caused the right side of the car to 1/2" out of square. We don't know the history of your car, so we can only speculate as to what may, or may not be the problem. Good luck sorting the car out, I know it can be a PITA.
Click to expand...
Test n Tune went well Friday night. The taller tires did slow things down a little but it hooked every time. No vibrations.
 
ajarofclay said:
100% agree, I was miffed for a second too. Taller tire will change the pitch of the whole car, drive train included. An altered rear suspension would change things.
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A taller tire changes nothing about the angle of the drive line.
 
Rockinrobin, looking forward to some positive results, long term under all conditions! Keep us posted!
 
gregsdart said:
Rockinrobin, looking forward to some positive results, long term under all conditions! Keep us posted!
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Car has slowed a bit but more consistent. Had a race 2 weekends ago. 5 passes. Never spun a bit. Last Saturday night at a track with bad prep, never spun, made it to semifinals then broke out as weather was cooling down. He had a .006 tree to my .02 and he ran his number dead on with a 2! I never had a chance. Had to break out by .009 to take the stripe. He won the final as well and told me it was his best package in many years. Next race in 2 weeks at a track that always hooks and about 10 degrees cooler so I'm really looking forward to it!
 
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