|
|
Post by ssm31 on Aug 5, 2013 9:18:19 GMT -6
Is it possible to have to much forward drive and if so will it make the car slower? I was having problems with forward drive and made adjustments to help forward drive but the car is much slower now. Before I never had any problem pulling in the straights but the car was really loose on exit. I increased my rear ride heights and it pulls good at exit and through the straights but just don't have the ability to gain or out run other cars. Should I find a happy medium between my old settings and new settings?
|
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Aug 5, 2013 10:25:17 GMT -6
I run a 4bar spring behind with a spring pull bar. I add fwd bite for the small bullrings and take some out for the bigger momentum tracks. Not sure what you are running, 3 link with a pull bar? Raising the ride height would take angle out of the top link thus extending your drive down the straight. Putting the angle back in the top link would get your drive back off the corner. Im always looking for the happy medium also, but every track is different. Bottom line, do what makes you fastest.
Dave
|
|
|
|
Post by ssm31 on Aug 5, 2013 11:15:53 GMT -6
I forgot to mention its a southern sportmod with factory four link.
|
|
|
|
Post by leaf4life on Aug 5, 2013 19:38:07 GMT -6
In that case. Upper control arms should be at least stock rubber, they also sell " soft" upper bushings that help absorb tourqe. As far as arm angles, I would ask 96m about that. He has much more experience than I do with metrics. And as far as I have read, there is "two sides of the fence" on the angles
|
|
|
|
Post by ssm31 on Aug 6, 2013 20:36:48 GMT -6
96m any advice? And what side of the fence am I on?
|
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Aug 7, 2013 7:22:49 GMT -6
You said it had good drive before. Then you made adjustments to add more fwd bite. What adjustments did you make? Just raising the rear ride heights would add angle to the lower arms but take it out of the upper. I am on the side of the fence that says you want angle (down at chassis and up at rear)for the upper arms to aide drive. I look at it like this: If the upper arms are level to the ground, as the rear tries to rotate up under acceleration, it would pull straight back on the upper arms which pulls straight back on the chassis, doing nothing for drive. Now put downward angle in them and as the rear tries to rotate, the arms are pulling upward on the chassis and pushing the rear down. That would help drive. The price you pay for that is the rear roll center will raise which hurts side bite, thats why you need the RF spaced out and the RR pulled in as fare as you can get, and your weight mounted up high, to aide chassis roll over and get the side bite back. What angle do you have in the lower left and lower right arms? How much LR bite are you running?
Dave
|
|
|
|
Post by ssm31 on Aug 7, 2013 14:28:05 GMT -6
Well I haven't scaled the car recently and have changed springs and shocks since, but when I did scale I had 73lbs of LR bite. The second adjustment was raising the ride heights another 1/2" to the minimum 5" everyone has recommend but that did move the upper arm angles to a little past level, being chassis higher than rearend. What you have explained makes perfect scents. I will move my ride heights back down to 4 1/2" ( which I measure from the top of the aXle tube to the bottom of the frame) which will put about 1-2 degrees of downward angle.. I guess that leads to another question what adjustment would help the loose out on throttle. When the rear kicks around I let of the throttle and it will straighten itself out, less roll out?
|
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Aug 7, 2013 15:30:25 GMT -6
I'll say this. I won a National Championship with a High School Driver and our metric had 440lbs of LR bite and 17 Deg of angle in the upper bars. Slick tracks were our bread and butter. Nothing came off the corner like that thing did. I would start going up on the LR Bite and see how you like it. If you can rejig the rearend upper mounts to get more angle. I would do that also.
Dave
|
|
|
|
Post by clbaker25x on Aug 11, 2013 9:04:22 GMT -6
Dave, you are giving away too many secrets.  I love a ton of rear bite in a race car. It frees corner entry and helps with forward drive. It also has a huge effect on how preloaded your left rear spring is which helps keep the left rear tire planted. We run a ton of left rear bite in our car and love it. The thing is most people can't get their car to turn then, but I believe that is because they are usually too stiff for springs up front. If your left rear is planted into the ground your car will have forward bite. I believe that when you start to focus on your right rear tire for forward bite it causes a ton of problems!! Your car gets tight on entry and you start to use and abuse your right rear tire because you have to scrub it on entry to turn the car. Huge problems all of this creates. Setup wise put as much bite in your car as your motor can pull and then soften your front springs to allow the car to turn. Once you get to the point where you are excessively bottoming your right front a-arm then you know you may need to back off a little. In our car I love for it to bottom just a little bit right in the middle of the corner. You need to be willing to change your right front spring depending on the track conditions. If the track is really fast stiffen the right front spring 50 or a hundred pounds. The problem is most folks have their baseline setup too stiff up front so they are not getting any travel over there and causing major problems. If you have a stiff spring in the right front and you are bottoming out the car then look at your front roll center and your front end chassis heights. We set ours front end to be level across the lower a-arms. Many of the cars I see are set too low up front which causes excessive travel on the right front uneccesarily. Then they can't go softer on their springs because the car will bottom out. Just my $.02! |
|
|
|
Post by ssm31 on Aug 11, 2013 17:30:10 GMT -6
Ya I have already made the front spring change. I had a 650 in the RF but it would bottom out, so I bumped it up to a 700. Which it does not bottom out. Your post did confirm a thought I had on raising my front ride heights and I will do that this week and try that.
|
|
|
|
Post by clbaker25x on Aug 13, 2013 8:40:29 GMT -6
|
|
|
|
Post by jimmyb3 on Aug 13, 2013 8:43:38 GMT -6
You say a "ton" of LR Bite. What is a "ton"
|
|
|
|
Post by jimmyb3 on Aug 13, 2013 8:47:37 GMT -6
Also, if I have 2.5" of RF shock travel left available, go down from a 600lb RF spring to 550? I have a 500 in the LF.
|
|
|
|
Post by clbaker25x on Aug 13, 2013 10:05:33 GMT -6
On left rear bite I wouldn't be afraid of 300 pounds or more, that is what we run in our car. What track are you running? I like to see at least 3" of shock travel on the right front. Make sure you have the clearance, but I wouldn't be afraid of a a 500 pound spring on your RF. We were running a 300 pound RF spring in the video that is in the other post. That was a little excessive unless the track was really slick. If you get your car going right you should be able to adjust your RF spring to match the track conditions. Softer for slow and slicker. We are at a 550 RF currently for heavy tracks (425LF, 550RF) and will drop our spring rate down to match the track as it gets slick. Just watch your shock and your clearances to make sure you are not going to hit. Good luck, let me know how it goes for you. |
|
|
|
Post by clbaker25x on Aug 13, 2013 11:07:30 GMT -6
This is a video were you can see the car really getting over on the RF and jacking pretty good. This was with a 300 pound RF spring and 300 pounds of bite in the car. The race is at Beatrice Speedway where they have a pretty fast group of Sportmods. |
|
