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 Post Posted: Mon Nov 24, 2008 11:42 am 
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Last friday night we went racing at Sunshine  1/8 mile track.  The car was working great made 3 passes in the right lane 6.017, 6.016, 6.014. Then I got the bye in the 3round So I thought I would try the right lane, at the 330 they tires went up in smoke had to get out of it.  Well now for rd 4 I did not have lane choice and the dragster stuck me in the left lane ](*,)  I was hoping it was just a one time thing.  About 500 ft the car went side ways and just about hit the wall  O:).  How I saved it is pure luck.  Now It was a cold night 49.8* track temp about 47* But I have run this car in cold weather before.  I have looked the car over for any thing broke or loose.  Any ideas would be great, do I need to play with the 4link?  I want to run Friday night but dont want to wreck it.    Thanks Matt

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 Post Posted: Mon Nov 24, 2008 12:38 pm 
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Did the ass end of the car feel funky at all before this happened?  Reason I ask is b cuz I was having down track problems with mine and it turned out to be that the springs were too weak for the application.  Tie wrap the shock shaft to see how much travel the suspension is using down track.

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 Post Posted: Mon Nov 24, 2008 1:14 pm 
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The car has been feeling differant in the rear. Feels loose like your on ice.  I have 130 lbs spring in there there are 8 yrs old. I should put some new ones in to start with I guess.  Would you stay with 130 springs?  The car is 3050 with me in it . If I remember right it is like 1450 in the rear.

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 Post Posted: Mon Nov 24, 2008 3:46 pm 
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Matt old school said run light weight springs, but now that's not the case.  What you are discribing is exactly what mine was doing, if just felt loose down track all the time.  

Look under the rear of the car at the shocks to see if the shaft is clean all the way to the top.  If it is, then it's likely that you are bottoming out down track and causing this problem.  I went from a 95lb spring to a 125lb spring and it made all the difference in the world in mine.  

What I bought was a pair of Competion Engineering springs and on their site they have a chart to help select spring weights by rear weight of the car.  I'd go look at that and see what they say.  3k lbs is heavy for a drag car and I don't know if a 130 spring is enough for that??

Maybe Scott or one of the others will chime in on this but it's my guess that you'd need about a 150 on there.  

But first, look at the shocks and see if it is indeed bottoming out.

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 Post Posted: Mon Nov 24, 2008 4:05 pm 
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I was looking at the charts, thinking the same thing 150 lb spring.  I looked at the shocks the shaft is really clean all the way to the top, but there is a very light dirt mark about 1 inch down from the top.

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 Post Posted: Mon Nov 24, 2008 7:48 pm 
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Well, you can look at it like this.  I spent about $1500 and a year and a half chasing mine before I found out that a $90 set of springs was all it took to fix it.  So if I were in your shoes, I'd order a pair of springs for under $100 and see if that did the trick before I did anything else.  I might would even try to find a little bit stiffer spring, say in the 160 to 170 range.  At 150 and 1450lbs you're at the upper limit.

If you don't want to buy the springs, then at least put a tie wrap around the shock shaft and slide it down against the shock body to see if it is hitting bottom on a pass.  With the 125lb springs on mine I now have about 3/8" from bottoming out on a run.  

And remember, if you have a wing on the back of the car that will add downforce and make the spring think the car is actually heavier than it really is.  I did some calculations on mine and I got about 580lbs of downforce added to the rear car weight down track.

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 Post Posted: Mon Nov 24, 2008 8:14 pm 
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No you are right Ken  spring are a cheep fix.  I need to do some thing before I will go back down that track :-k . If I went with 170 spring and there to stiff what would be the draw back of too stiff of a spring.

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 Post Posted: Mon Nov 24, 2008 9:20 pm 
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sommersracing wrote:
No you are right Ken  spring are a cheep fix.  I need to do some thing before I will go back down that track :-k . If I went with 170 spring and there to stiff what would be the draw back of too stiff of a spring.


Hummm, dunno Matt.  Did you find a 170 spring?  

I expect that with too much spring it would act kinda like it does with not enough.  Loosening shocks could help that though as my car did better with soft shock settings BEFORE I changed the springs.  If you bought them and it turned out that you couldn't us'em then you could probably sell'em either here or on fleabay.  

Go fer it Bubba!   ;-)

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 Post Posted: Mon Nov 24, 2008 9:37 pm 
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I always look first at tires. Tread dept can change a tire's slip angle so much. When picking a spring rate, you must consider their job and be aware they have three partners for doing this job. They have shocks, thats easy. they have weight transfer, which varies. Then they have anti squat values. This does not include the energy absorption the tire has.

How it works. The weight on the rear at any given time varies. You can tell how much of the total weight is on the rear by looking at compression on the front. Since we know it varies, we know the tractive force varies. We also know that spring rate unless it is a progressive rate does not vary. If we run into traction problems down track, it could be the springs are storing more energy that they transmit to the tire, but it also could be that one of the two remaining partners aren't doing their share. Anti squat or lack of can change the demands on a spring from not using the spring at all to using it up to bottoming out. We can see this in cars by watching the compression or separation in the rear. Then there is the shock. The shocks main purpose is to dampen compression or separation that can lead to oscillation. You only get a couple oscillatory moves before tire spin gets a free pass.

With this said, you can have a 90lb spring that never bottoms out because of positive anti squat value and a 200lb spring that bottoms out because of negative anti squat values. To me it stands to reason that close to a neutral squat/anti squat would tax a spring less, leaving it with just the job of smoothing out the bumps, not storing and transferring weight.

Did that make any sense?

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 Post Posted: Mon Nov 24, 2008 9:42 pm 
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I have to add, the more bumps the softer the spring rate is the rule. This is a matter of tire compliance. Of course a smoother track a stiffer spring will give you best performance.

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 Post Posted: Tue Nov 25, 2008 9:45 am 
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sommersracing wrote:
Last friday night we went racing at Sunshine  1/8 mile track.  The car was working great made 3 passes in the right lane 6.017, 6.016, 6.014. Then I got the bye in the 3round So I thought I would try the right lane, at the 330 they tires went up in smoke had to get out of it.  Well now for rd 4 I did not have lane choice and the dragster stuck me in the left lane ](*,)  I was hoping it was just a one time thing.  About 500 ft the car went side ways and just about hit the wall  O:).  How I saved it is pure luck.  Now It was a cold night 49.8* track temp about 47* But I have run this car in cold weather before.  I have looked the car over for any thing broke or loose.  Any ideas would be great, do I need to play with the 4link?  I want to run Friday night but dont want to wreck it.    Thanks Matt


sommersracing,

Did you change anything from the right lane to the left lane? tire pressure?, was there any downtime from the last car that ran that lane?, is that lane known for being good or bad by comments from other drivers?  Milan Dragway for example here in the Detroit area is known for having a fast, and slow lane, Norwalk, Oh. also has this variable and it can also depend on downed fluids, cleaning, and the biggest one I see here is the track temp vs. the engine temps and the cooler air it has to burn with,(more power being made).
Seems funny how it hooks great in one lane, and bad in another, but like Ken said, this can lead to a bad component soon to fail if it hasn't already.
Not to kick Ken under the bus on his ideas, but could you send the shocks and srings out for testing?, would it be cheaper or cost more to find the bad components vs. changing parts?, again Ken, no toe jamming here but what if he has one bad spring? yes, this would for sure warrant a new set of springs, or even one bad shock!!!  Just my brain after wakeup call talking, should I go back to bed???? =;   Something does seem funny here regardless of what you find, but maybe a verification run again with people watching farther down track for you and a good video cam also?, do you have a temp gun that can read track temps down range on the track?   Just idea's for troubleshooting, and be sure to let us know what your outcome is please, I and others can use this info for future use, and thanks for your run info, very good info. =D>

John

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 Post Posted: Tue Nov 25, 2008 11:22 am 
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Hello John  No I did not change a thing and there was only 15min between rounds.  That was the first time to that track and dont know to many people there, so not sure if the left lane has any problems.  The starting line guy walk down the track both times I spun the tires.  I can not rember if there was any bump in the left lane to affect the car. ](*,)  I just want to make sure all is good, since I all most totaled my car and the dragster in the right lane.

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 Post Posted: Tue Nov 25, 2008 12:46 pm 
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Matt, I got to know the starter at my local track and when I was testing with the newly installed shock sensor I asked him what lane is better  :-k ..He told me the the left lane is better...Now he is also the guy that preps the track and sprays it....

It was funny cause after the 1st set of time runs everybody was in the left lane O:)  O:)

Just a little bit of info that worked for me :-$

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 Post Posted: Wed Nov 26, 2008 11:08 am 
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Hey you guys,

 Since you all run coilover setups in the rear or your cars, what's your thoughts of a shock brand, and I also was wondering what is the BEST way to mount the coilover shock kit?  I have seen them straight up & down to almost a perfect vertical position, some have the bottom mounting point angles out towards the tires, some have that, and lean back.  Upon thinking of how the car launches and basically goes in a straight line, I would think that the shocks don't need to be on an outboard angle(towards the tires at the lower point!, or does the setup like this give the rear suspension a better side to side loading for a better stable ride, and or if getting out of shape for a better control to this?  Just one more thing for me to think on when I have my backhalf done, and it will be a 4 link with 15 x 15 x 33 tires and rims.  Thanks guys and this is such a good thread, and you guys have soo much good info., I thankyou for spreading this around,(priceless) to the average racer =D>  =D>  

John

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 Post Posted: Mon Jul 13, 2009 9:50 am 
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Location: Hudson, FL
Just thought I would give an up-date on what fixed my problem. After changing spring and shocks ](*,) The rear tire were the problem, weak side walls. Back to GoodYears . Thanks for all the input Guys.

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