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giants17068
06-30-2010, 06:41 PM
I know I have read several places and also talk with a lot of other crew guys at the track. Most all of them run there shock and spring behind the axel with a dummy or traction shock in front. I don't really understand why. My thinking is with the shock in front it is helping keep the birdcage indexed since as the car comes back down the birdcage is rotating clockwise or into the shock. With the shock in the rear of the axel its not helping as much. we run a 6c-2r shock on the front of the axel and a 4c-0r with the spring on the rear of the cage. Could someone explain what I am missing or not understanding? Thanks Dan

MasterSbilt_Racer
06-30-2010, 06:52 PM
I agree with you. The rear shock doesn't do much because of the motion ratios. IMO you should have something soft back there and no need for adjustments. You then use the front shock to tune the car during the course of the night. I can assure you there are others that think that way too and who do win races.

Matt49
06-30-2010, 10:01 PM
We run a shock behind and nothing in front. We normally run a 6 or 7 compression and I wasn't noticing any difference when changing between the two so I questioned whether or not is was really doing anything. I turned the compression down to 3 and learned real quick that it was certainly doing plenty. The car was slamming down so hard on entry that it was almost undriveable. I promptly moved it back to 6.

MasterSbilt_Racer
06-30-2010, 10:40 PM
We run a shock behind and nothing in front. We normally run a 6 or 7 compression and I wasn't noticing any difference when changing between the two so I questioned whether or not is was really doing anything. I turned the compression down to 3 and learned real quick that it was certainly doing plenty. The car was slamming down so hard on entry that it was almost undriveable. I promptly moved it back to 6.

That is my point. You had to go 3 numbers to tell a difference. On the front you can tell one number. You can tell when you add a little gas. IMO, on all vehicles, the damper belongs where the largest motion ratio is.

sobe92
07-01-2010, 01:10 AM
Overall as with all things there are times for a lrf shock and times you can take it off and be better. basically it is an entry shock if you are at a track that you can stay on the throttle on entry and it won't slam down you could take the front shock off and gain some forward drive.

other tracks you simply have to have that shock on the car to keep the car under you on entry. it is a driver/car/track preference and there is no right or wrong the top 3 cars could have 1. a high gas pressure monotube high compression 2. a high compression twin tube 3. none

depending on the driver and setup who is to say they are wrong.

MasterSbilt_Racer
07-01-2010, 06:46 AM
I'm speaking from a design/efficiency standpoint. What I believe best utilizes the shock. Obviously, anything can work if you find a way to get the right amount of damping for the situation.

When you can build a shock with negative rebound resistance at slow speeds, I don't see it hurting drive mounted out on the front.

giants17068
07-01-2010, 09:30 AM
I thought my thinking was correct and if so I am very surprised that so many other well performing cars run there shock and spring behind. So my next question would be the rear spring differences. I have been told and read two different things. One states that a stiffer right rear spring will promote side bite, because of more force being applied to the track when the car rolls over there. the next thing would say a softer rr spring will allow the car to roll to that side more promoting side bite. I tend to think the stiffer spring is the way to go because the j-bar should control body roll not the spring.Any clarification on this?

giants17068
07-01-2010, 09:41 AM
Ego, the car I am talking about is the dirtek you sent me the setup sheets on. They call for the traction shock 4c-0r on the front of the cage and the 5r-3c shock in the back. Can you remember what you guys had better luck with? Thanks Dan

MasterSbilt_Racer
07-01-2010, 01:24 PM
I thought my thinking was correct and if so I am very surprised that so many other well performing cars run there shock and spring behind. So my next question would be the rear spring differences. I have been told and read two different things. One states that a stiffer right rear spring will promote side bite, because of more force being applied to the track when the car rolls over there. the next thing would say a softer rr spring will allow the car to roll to that side more promoting side bite. I tend to think the stiffer spring is the way to go because the j-bar should control body roll not the spring.Any clarification on this?

There is more than one way to skin a cat, I just don't think everyone always goes about it the most logical way. I swear a lot of the "I can't run a front shock" idea comes from the fact someone took one off and went forward better. Almost always, they changed the total drop on the lr and the amount of rebound damping. Those 2 things together are huge.

Weight transfer is determined by cornering speed and cg height. During weight transfer, the stiffer spring gets the weight. A stiffer RR will receive more of that lateral weight transfer. The car will be tighter on entry and get the rr in the track. The only time it won't is if you go too far and the car loses grip because the rr suspension has become too rigid. You corner speed will decrease and the weight transfer will decrease as a result.

JTSjet
07-01-2010, 02:17 PM
I'm speaking from a design/efficiency standpoint. What I believe best utilizes the shock. Obviously, anything can work if you find a way to get the right amount of damping for the situation.

When you can build a shock with negative rebound resistance at slow speeds, I don't see it hurting drive mounted out on the front.

i agree. i use the lr front shock to control almost all of my dampening lr, and use a 0/0 lr behind, 2 different chassis.

giants17068
07-02-2010, 09:26 AM
Well I do not have a double adjustable for back there. So what do you think would happen if I put say the 4/0 on the front and a 0/0 on the back to start the night when the track is heavy, and the 6/2 with a 0/0 when the track slicks off? Right now with the 6/2 and 4/0 on I think we may have to much compression keeping the LR up all the way which may be giving us a little bit of a loose in problem. I am I correct in thinking this way? Thanks Dan

JTSjet
07-02-2010, 11:04 AM
Well I do not have a double adjustable for back there. So what do you think would happen if I put say the 4/0 on the front and a 0/0 on the back to start the night when the track is heavy, and the 6/2 with a 0/0 when the track slicks off? Right now with the 6/2 and 4/0 on I think we may have to much compression keeping the LR up all the way which may be giving us a little bit of a loose in problem. I am I correct in thinking this way? Thanks Dan

if i run 13 series afcos and a 0/0 lr behind i have 3 lr front shocks that seemed to work in any situation for me. (c/r) 5/3, 6/2, 7/1. 95% of the time running these shocks the 6/2 is just right.

stevo
07-04-2010, 11:29 AM
Will that slam down too hard?

JTSjet
07-04-2010, 12:47 PM
c/r: 6 compression; 2 rebound. have run a 90/10 with some more extreme bar angles but not typical and i try to avoid that. it seems to be plenty stable.


Will that slam down too hard?

stevo
07-04-2010, 03:09 PM
I know a guy thar runs 90/10 on rear with spring nothing in front

JTSjet
07-04-2010, 03:25 PM
i do have concern for backlash or wheel hop though. i pay very close attention to the 5th arm shock/spring and travel. hasn't happened yet.