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Forum: Sprint Car Tech Talk (go)
Moderators: BigDog

Topic: Sprint car chassis adjustments
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Yeti12
May 13, 2015 at 07:24:10 AM
Joined: 10/09/2014
Posts: 3
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Hello all, I am new to sprint car racing....starting my 2nd season.   My question is regarding adjustments through the night and what would be concidered a big adjustment to the chassis and what would be a small one.....example.....if the we wanted to tighten the car up for the feature and we moved the RR in 1/2".....is that going to have a dramatic effect on handling or is it just a sligh change.  If I wanted to stick the car better at entry, would 2 turns in the RR be a huge change or just slight.  I know these are kind of vague exapmples but we just arent sure what dictates a "big swing" at a change and what would be otherwise minor.  

Thanks all.  Any input is hugely appreciacted

Brad



Digracin58
May 20, 2015 at 03:30:44 PM
Joined: 05/20/2015
Posts: 2
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Reply to:
Posted By: Yeti12 on May 13 2015 at 07:24:10 AM


Hello all, I am new to sprint car racing....starting my 2nd season.   My question is regarding adjustments through the night and what would be concidered a big adjustment to the chassis and what would be a small one.....example.....if the we wanted to tighten the car up for the feature and we moved the RR in 1/2".....is that going to have a dramatic effect on handling or is it just a sligh change.  If I wanted to stick the car better at entry, would 2 turns in the RR be a huge change or just slight.  I know these are kind of vague exapmples but we just arent sure what dictates a "big swing" at a change and what would be otherwise minor.  

Thanks all.  Any input is hugely appreciacted

Brad



depending on car, track size and grip, 1/2" in on the RR is not much of a change, it'll add some side bite. 2 turns in the RR is a little much, it will get the car to turn a lot in my opinion. I would go with 1/2 turn adjustments... At our 1/4 mile bullring, I begin with 1/2 out of the LF and 1 turn in thr RR. The RR out 18 1/4, LR 14. By the A-main we run the car flat all around and the wheel spacing RR17 1/2, LR 14 1/2. We tie down the LR with a 3-8 shock with helps the car turn all the way thru the corner.. not sure on your stagger but we run about 13" for our mains which is most often dusty clay by that point.  Most of the time we block the front at 3" and run 5-3 shocks on both sides of the front. It launches the car good off the corners.. hope this helps..



Yeti12
May 24, 2015 at 08:43:38 AM
Joined: 10/09/2014
Posts: 3
Reply


Thanks Digracin.  Our track (Ohsweken Speedway) is a 3/8 (probably more like 4/10th around the top) mile.  Id say a moderate banking...not high, not flat.  Typically we run 11-12" of stagger.  What we are fighting this year so far is overall grip.  Its not terrible in the heat but once the main comes around we are garbage.  Here is my entire set-up....please feel free to make adjustments where you (or anyone out there reading this) feel we could change.  First about the car....2010, 88.5/40 J&J raised rail.  The car his pretty heavy because this is a GM crate engine class.  The car weighs 1590lbs with me and 12-15 gal of fuel....about 62% rear weight. 

Bars                                Shocks                                  Spacing                         Blocking                    Air

1050rf                             6/2rf                                      16.5"rr                           3"rf                       12rf

l025lf                               5/3lf                                      13.75"lr                         2"lf                        10lf 

1025rr                              4/6 rr                                                                         4"rr                        6rr

1000lr                              3/8lr or 4/7                                                                3"lr                         4-4.5lr

 

This is what we ran friday nite...track was dry and taking rubber....I couldnt find a stitch of grip.  Any info or tips would be great!  Thanks all

Yeti



racrguy
June 05, 2015 at 04:47:25 PM
Joined: 03/26/2009
Posts: 96
Reply

I think your front bars might be too stiff. I run .25's on the right and 00's on the left unless it gets super slick, in which case I soften the RR bar up. I wouldn't run that much shock split on the RR. You may be running too low on the air pressure on the RR causing you to run on the sidewall and not the tread. When tracks are slick you HAVE to be on top of your gear. If you have too tall of a gear you'll just be roasting the tires off because you can't get them spinning slow enough to gain traction. Slow the tires down and you should see a marked improvement depending on what the rest of the setup does. I run a Racesaver car on small Texas tracks, and I end up in the mid 7's on gear at ~7800.

 

If the track was taking rubber, your car should've been so tight you had to throw it in to get it to turn. That's another problem you could be having, running the car so tight you're having to shake the car out of the set to get it to turn. When you're running in the heat race and the car feels somewhat good and you put a taller tire on the car you need to take 1/4-1/2 round out of the left rear bar to keep the attitude of the car the same. Remember, you just want to change the stagger of the car, not the weight distribution so if you put the taller tire on it without changing the bar, you're making both changes which could mess up your whole setup.



Yeti12
June 13, 2015 at 07:11:43 AM
Joined: 10/09/2014
Posts: 3
Reply

The reason we had a 1050 RF and 1025 LF was based on the fact that the engine in this class of sprint cars is so heavy.  We were trying to keep weight off the front, and also to help with weight transfer to the rear.    In terms of the RR shock, would a straight 5 be more inline with what you would run?  Also, how much tiedown would you run in the LR?   I hear alot of different opinions on shocks when the track is dry.....some say run lots of tie down on the LR to get drive off, some say run slight amounts of tie down on both rears (4/6 on both rears) to keep the weight back on both tires.  Thoughts on either?  Thanks for the input....this is so valuable to my learning curve!



racrguy
June 17, 2015 at 10:48:06 AM
Joined: 03/26/2009
Posts: 96
Reply

The series I run with has a steel block with aluminum heads, and I don't run that heavy of a set of front bars. I've noticed that when I run a softer compression LR shock I don't get as much grip out of the LR than when I run a tie down. A flat 5 is a good all around shock for the RR. I don't know that I'd run a tie down on that corner, but you're also running on a much bigger track than I am, so keep that in mind when taking my advice. My car with fuel (I can't remember how much off the top of my head, probably full) weighed in the neighborhood of 1630.



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