Traction Shock Question

[hobbyracerbn2]

I got a Afco Traction Gas shock..I have been running Afco Regular 50/50 shocks on my Grt..I got 75's on front with 94's on back...just wondering in order to run my traction shock on the lr in front of axle would i have to change my 94 shock behind shock to a split valve shock to run to traction shock or would it just be fine??? Thanx

[fox1162002]

You need to be split all the way around car in order to get a consistent car. Now if your racing in a tacky hooked up track you can get by with 5s and 4s. But in the slick you need split stuff. On my older grt we ran 5/3 550lb lf, 3/5 375lb rf, 3/5 225lb rr, 5/3 or 8/2 250lb lr, 3/7 300lb lift bar, we hardly ever ran a traction shock and won alot races with that combo. I hardly ever changed shocks or springs from the tacky and slick we justed freed the car up with bars. But that's my opinion and everybody are different

[sj valley dave]

On our older GRT we ran similiar shock splits before we went to double adjustable gas monotubes. We ran a 9/3 split on the LR behind with no traction shock. We run a 500 lb/400 lb split in the front springs though.

[lovinlatemodels]

There is no rule that says you have to run split valves all around the car. U need a base line to start and tune from there. Also shocks are timing devices so to say you need split valves isn't always true it depends on driver, track conditions, and track size i know some people that still run some straight valving along with split. We run a traction shock but the car was getting up on the bars so fast we had to change valving to calm it down if you car works with what you got already just put the traction shock on and try it and go from there.

[Matt49]

I think we often get lost in the idea that getting the car up on the bars is all for getting bar angle to generate forward bite. Don't forget we are also trying to get side bite on entry and through the center. If you can get the left side up to generate lateral weight transfer (because of increase j-bar angle and raised VCG), that weight needs to go somewhere (to the right side). One sure fire way to make sure that weight gets there fast and stays there through the center of the corner is to split valve the right side shocks with softer rebound and stiffer compression.
Not saying that's what you need but just giving you another way of looking at it.

[sj valley dave]

Hey Matt, I think you mean to stiffen compression and easy up on the rebound on the left side to allow weight to roll easier onto the right side...

[drtrkr244]

I dont know who started the idea of more lr bar angle=more drive, but it hasnt worked on any lm ive setup yet. Maybe our tracks are different down here in the south. Also, when the car is up on the bars, dynamically the car is de-wedged. Also, the oversteer that is created seems to outweigh the forward thrust that is induced. This is also confirmed by many engineers in our industry.

[Matt49]

Hey Matt, I think you mean to stiffen compression and easy up on the rebound on the left side to allow weight to roll easier onto the right side...

In conjunction with softer compression and stiffer rebound on the right side to let the weight get there and stay there longer. I'm simply making the argument for split valve shocks on the right side for someone considering running a blow-up shock on the LR.

[Matt49]

I dont know who started the idea of more lr bar angle=more drive, but it hasnt worked on any lm ive setup yet. Maybe our tracks are different down here in the south. Also, when the car is up on the bars, dynamically the car is de-wedged. Also, the oversteer that is created seems to outweigh the forward thrust that is induced. This is also confirmed by many engineers in our industry.

Most people (but not all) are figuring out that once the LR upper bar gets past about 45 degrees, you start to lose the advantage of the thrust angle.
I'm not sure about the idea that the car is "de-wedged" when up on the bars. I think many have found the opposite to be true. The increased thrust angle is providing added load on the LR while under acceleration but refer back to my first sentence...you can go too far.
And excessive oversteer because of roll rear steer is manageable. If you want a great deal of LR thrust angle without the excessive roll rear steer there are many ways to do it that will further compliment a slick track setup.

[drtrkr244]

Most people (but not all) are figuring out that once the LR upper bar gets past about 45 degrees, you start to lose the advantage of the thrust angle.
I'm not sure about the idea that the car is "de-wedged" when up on the bars. I think many have found the opposite to be true. The increased thrust angle is providing added load on the LR while under acceleration but refer back to my first sentence...you can go too far.
And excessive oversteer because of roll rear steer is manageable. If you want a great deal of LR thrust angle without the excessive roll rear steer there are many ways to do it that will further compliment a slick track setup.

As I stated, This was confirmed by several engineers in our industry. I was able to obtain some analysis from a dlm test on one of NASCAR,S seven post pull down rigs. I took this info to my race shop and started playing with the racecar while on the scales. Some people on here claim u cannot simulate racing conditions while on the scales. That is not TRUE! I was able to get very close once I understood about weight transfer. I,ve learned more in the past 3 years doing this than the other 20 years traveling all across the country , racing these type of cars.

[Ghopper]

As I stated, This was confirmed by several engineers in our industry. I was able to obtain some analysis from a dlm test on one of NASCAR,S seven post pull down rigs. I took this info to my race shop and started playing with the racecar while on the scales. Some people on here claim u cannot simulate racing conditions while on the scales.

I believe you learn something that improved your race program, but the seven post is not applicable. The anti-squat in the rear suspension is to large to allow the results to be meaning full. You would need a dynamic kinematic and compliance rig to do this....this would load the suspension in the longitudinal and lateral directions.



Ghopper

[drtrkr244]

I believe you learn something that improved your race program, but the seven post is not applicable. The anti-squat in the rear suspension is to large to allow the results to be meaning full. You would need a dynamic kinematic and compliance rig to do this....this would load the suspension in the longitudinal and lateral directions.



Ghopper

What I found out,basically, was a correlation between the loads on each tire and what the moment center was doing in the dynamic state. When I put the car on the scales at various dynamic ride heights and input that info with what my 3d moment center software showed. Most racers dont have a clue what weight transfers where during one circuit around a track. Thats the missing link you have to find out about your car . Only then, can u make accurate adjustments for the ever changing dirt track conditions!

[fox1162002]

Well y'all can keep all the engineer stuff but I ran basic 5s and 4s for years and was always a decent car but not a front running car. Bought a car with the split stuff on it and found myself racing for the win week after week. It helped me and with shocks these days in my opinion they mean alot. I tell everybody that ask for help with set up is to get hooked up with a good shock guy and work with them. It means alot.

[drtrkr244]

Well y'all can keep all the engineer stuff but I ran basic 5s and 4s for years and was always a decent car but not a front running car. Bought a car with the split stuff on it and found myself racing for the win week after week. It helped me and with shocks these days in my opinion they mean alot. I tell everybody that ask for help with set up is to get hooked up with a good shock guy and work with them. It means alot.

Sorry about that, its easy to get carried awwy with this addiction to dlms.After doing this for over 25 years, ive seen alot of things .The biggest mistake i see is not being totally prepared week after week.If you have to skip a week do it.When u add up the costs for one trip to the track and the expenses at the track this sport gets very expensive. Stay home a week or two, get your stuff right, then you will have good results.Set up your car just like the builder says to inc his preferred components.Then if you have a problem he can help you.Dont fall for the trick part or trick setup of the week.Put your car on scales and jack it around at racing attitudes, you will be amazed at what u learn.

[joedoozer]

Sorry about that, its easy to get carried awwy with this addiction to dlms.After doing this for over 25 years, ive seen alot of things .The biggest mistake i see is not being totally prepared week after week.If you have to skip a week do it.When u add up the costs for one trip to the track and the expenses at the track this sport gets very expensive. Stay home a week or two, get your stuff right, then you will have good results.Set up your car just like the builder says to inc his preferred components.Then if you have a problem he can help you.Dont fall for the trick part or trick setup of the week.Put your car on scales and jack it around at racing attitudes, you will be amazed at what u learn.

I thought about doing this over the off season. How I could simulate my car in dive/roll/up on the bars when its sitting on scales. You can't just simply put a floor jack under it, because it is carrying the load and not the wheel. I thought about using some sort of turnbuckle in place of the coil overs. This way I can tie down and jack up any corner I wanted to. I just haven't gotten around to trying it. It's only my second season and I am still learning the basics. Putting a car into a dynamic state on scales is more "varsity" level stuff. I don't think I would know what to do with the information at this point. But it is something I have been thinking about.

[Ghopper]

drtrkr244 -

I think you should explain your procedure for testing race conditions on scales. fyi - this thread is discussing dampers, which have few near static qualities (stick/slip of seals, rod pressure).


Again, I believe you are learning sometime but there are many holes in not including the lateral and londitudinal forces. For example: the increase in LR load from the j-bar contributions.


Ghopper

[drtrkr244]

drtrkr244 -

I think you should explain your procedure for testing race conditions on scales. fyi - this thread is discussing dampers, which have few near static qualities (stick/slip of seals, rod pressure).


Again, I believe you are learning sometime but there are many holes in not including the lateral and londitudinal forces. For example: the increase in LR load from the j-bar contributions.


Ghopper

Like i said in an earlier post, you cant totally simulate race conditions. You can get an idea of weight transfer by using simple formulas found in varios books.You definitely cant simulate the lr or j-bar load changes.I generally use heavy duty ratchet straps to compress the right side springs and then add the corresponding weight transfer to each corner.I do not take the springs and shocks off.Its not an exact science but it gave me trends to go by when making changes at the track.

[fastford]

What I found out,basically, was a correlation between the loads on each tire and what the moment center was doing in the dynamic state. When I put the car on the scales at various dynamic ride heights and input that info with what my 3d moment center software showed. Most racers dont have a clue what weight transfers where during one circuit around a track. Thats the missing link you have to find out about your car . Only then, can u make accurate adjustments for the ever changing dirt track conditions!

i have to agree with grasshopper on this one, there is no way to simulate the true dynamic conditions that exist on a dlm sitting on the scales or any thing else, way to many variables that exist in its true dynamic state, im not saying you cant learn something but your also making a lot of assumptions, like a car dewedgeing when up on the bars, pure logic tells me this cant happen, jmo

[Ghopper]

fastford - most physical lab tests are missing something from the physical track test.

There are high-end, high-cost simulation programs (30k-150k) that can account for more track phenomena than the lab test, but the parameters needed to be really accurate are not easy for most of us to obtain. There are some programs (5-10k) that clear state to tune lumped parameters to match test data, because the actual information is not available.....but the sensitivity of your study may be lost in that lumping process.



Ghopper

[drtrkr244]

i have to agree with grasshopper on this one, there is no way to simulate the true dynamic conditions that exist on a dlm sitting on the scales or any thing else, way to many variables that exist in its true dynamic state, im not saying you cant learn something but your also making a lot of assumptions, like a car dewedgeing when up on the bars, pure logic tells me this cant happen, jmo

I dont profess to be an engineer, but ive been blessed with an analytical mind and excellent math skills. Maybe Im wrong on the de-wedging part, but my common sense tells me the unloading of the rf,soft spring setups, far outweighs the forward thrust generated by the bar angle of the lr. I wish some of these CUP sponsored teams would do more testing and let our shock gurus adjust accordingly.My theory has been supported by some of these shock guys.I dont do any different adj. at the track than anyone else, i just know what i learned on the scales pertains to the car im working on with their particular setup., and what adj. gives me the most bang for the buck.