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Post by racer5056 on Jun 12, 2023 7:39:10 GMT -6
Hello, I am looking for help trying to achieve a stable setup for my drivers car. I have been reading books and forums for a couple of years now and slowly figuring this stuff all out. However, I just need someone with some expertise that I can bounce ideas off of but no one will offer any help.
The car is a metric Monte Carlo. Ford rear end with a four link, left lower trailing arm is in the bottom hole and the right is all the way in the top hole. The front lower control arms are set with the right a half inch lower than the ball joint and the left side is level, so the ride height is higher on the left side than the right side. Spring rates are LF: 900, RF: 1050, LR: 225, RR: 250. Scale numbers are LF: 861, RF: 755, LR: 1016, RR: 853. 53% left side weight, 53% rear weight, 50% crossweight, 163 lbs. of bite and a wedge delta of 57. Tires are 2" offsets all the way around except the RR has a 4" offset. Our tire selection is limited so we have been struggling to try different staggers, currently the front is on 3" and the rear is on three fourths of an inch. The car does want to turn left on the straightaways.
The driver complains that the car is pushing on entry and loose on exit in the dry slick track. The driver has to run up high to get around the corner and as long as he can keep his foot in the gas he can get around the corner but when other cars are in front of him, he has to put on the brakes and the car pushes. On a wet track with the 3" offset on the RR the car is loose all over the place and un-drivable. The driver also says he is very tired after the race.
I've been trying to follow a former member on this site's advice (Dave) because he also ran a metric Monte Carlo. I am thinking of lowering the RR spring to 200 to lower the rear roll center. The RF shock is bottoming out but I don't have the taller camero spindles he recommends to fix that problem. The RR tire is usually hot while the LR is much colder. The car is more stable than it has ever been but it still needs work. It came back in one piece this last time! The car is very front heavy, so we had to add around 300 lbs. of lead in the rear to bring it up to 53% rear weight. Some of it is in front of the fuel cell, a little is behind the LR tire and the rest is behind the fuel cell at various heights. I'm sure it all isn't in the perfect locations but choice is limited.
We're tired of the car being torn up because it is unbalanced. We would really like someone who has been doing this for a while to lend us some advice so we can feel safer taking the car out to the track.
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one8
Fourth Place
Posts: 52
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Post by one8 on Jun 14, 2023 9:27:37 GMT -6
I'm sure the other drivers don't want their cars torn up either. You didn't mention your shocks length or valving. I would run a tie down rf shock(heavy rebound). You also didn't mention the track type and banking. Personally I wouldn't run more than an inch of front stagger and would run between 1-2" of rear stagger. Put the 200# spring in the RR(175 would be better) and move the RR tire to a 2" offset. If the car is loose you can move the RF or LR out with a spacer. Then I would reset the rear bars to the RR level and the LR to one hole down from level as a starting point.
Spring rate only affects the rate of roll not the roll center. Roll center is determined by the suspension mount point heights. Center of gravity is affected by you ballast height. Higher= more roll. Lower= less roll.
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Post by racer5056 on Jun 14, 2023 15:59:18 GMT -6
Shocks - Front (7") LF: 50C/30R, RF: 40C/30R, Rear (9") LR: 60C/30R, RR: 50C/50R. Shock stock is limited, just about all the 7" shocks I have end in 30 rebound. Shock travel after the last race was: LF: 2 3/8", RF: 2 3/4", LR: 2 5/8", RR: 3 3/4".
The track is usually dry slick and horribly rough, not well maintained. Fairly high banking at around 3/8 mile.
Wheel spacers - LF: 1/2", RF: 1 1/4", LR: 1/4", RR: None. The spacers on the front keep the wheels from rubbing on things. The track width as the tires are setup in my original post has 64" in the front and 63" in the back, that is from center tire to center tire.
I've been trying to decrease the stagger in the front and add it to the back. I'll have to remount tires as we only have the 3 and 4 offset bead locks for the RR.
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one8
Fourth Place
Posts: 52
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Post by one8 on Jun 15, 2023 8:24:17 GMT -6
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Post by racer5056 on Jun 16, 2023 8:45:05 GMT -6
Yes we have those guides as well as other books. We've tried the cookie cutter setup examples and they did not work. Our chassis was built by an old timer who has now passed and those examples didn't fit with our chassis. What has worked the most is the advice given by Dave McKinney on this forum. Too bad you can't get a hold of him anymore. We had our weight up too high and the driver could feel it transferring too hard so we moved it down. Our car has been front heavy from the start so it's been a struggle to increase rear weight. We're almost at 3500 lbs. total weight now with only 53% rear weight. Dave was at 57% rear weight which we will never achieve unless we cut a few inches off the front of our chassis.
I replaced the RF shock. Our current inventory of shocks are all 30 rebound. The shock that was on there rebounded in 3 seconds and I replaced it with a sock that rebounded in 6 seconds. Maybe it will help for now. I increased the left side weight to 54% but our rear will stay the same at 53%. Our front stagger is 1" and the rear is 1 1/2" unless I decide to remount a tire. All that is left to do now is replace the RR spring. The car will be at 195 lbs. of bite with 51% crossweight.
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one8
Fourth Place
Posts: 52
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Post by one8 on Jun 16, 2023 10:40:44 GMT -6
I run a Bilstein 1052 in the RF. 112#C/325#R. They're around $90. It's a bit shorter and holds the RF down. You could try pulling the RF in a bit. That will have the affect of a little more perceived spring rate(less lever length on the spring). Maybe drop the rear % to 52ish.
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Post by racer5056 on Jun 17, 2023 10:01:22 GMT -6
I took a closer look at the lower control arm on the RF and noticed a line of missing paint, so I can assume that the RF is bottoming out on the frame. Dave says it needs 3 1/2 inches of clearance and I only measure 3. Too close to race time to figure out how to cut away part of the frame now. If this is why we are experiencing a push on entry then I may have done more harm than good trying to fix a tight in off the throttle condition. |
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Post by racer5056 on Jun 19, 2023 13:01:43 GMT -6
Cut away part of the frame. RF shock traveled 3" this time. Put 200 spring in RR. Raised left side weight to 54%. Driver reports entry is fine but spinning out coming off. "I hit corner it pushed and got in throttle it spun out". No idea what that means as I am working while he is playing so I can't watch the car. Sounds like he is saying it is still tight on entry but what do I know. I think we are wasting our time changing springs and shocks when we need to focus on fixing our front and rear roll centers. Maybe someone can take a look at my front geometry and chime in on what we need to do. Don't want to replace the spindles with Camero spindles right now as we would have to modify too many things. I would like to get the upper ball joints raised up some more and increase the angle on the upper a-arms to fix our roll center.  |
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one8
Fourth Place
Posts: 52
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Post by one8 on Jun 19, 2023 19:12:23 GMT -6
Shouldn't be too hard to find a taller ball joint. I would definitely work on corner entry first. 90% of the time that will fix exit. At least help anyway. If you can, you may want to try a 1200# RF spring. The speed you carry at corner entry and the banking, the stuffer spring should help plant the RF tire. I ran your original stagger numbers on my car Saturday night and the car was pretty good still. Track stayed heavy all night but got rough. I kept bottoming out the RF. Was a little tight in the center. The driver may be able to help too by changing entry sepped or angle. Trail brake in or enter straighter.
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Post by racer5056 on Jun 20, 2023 6:36:52 GMT -6
Driver said the RR tire was hot and the LR and LF were much colder. I've been after him to check tires so I can have some kind of diagnostic tool to work on the car but I'm scratching my head with very limited information. Gotta love family!  I probably can't get any taller ball joints by this weekend. I went with an 85 on the RF to reduce front stagger but that 86 (or larger if I can find it) may help lift that ball joint up. It's simple enough to check. The largest spring we have is an 1100 and I've been debating on if to put it on. I wanted to keep that 150 split but I don't have a 950 for the LF so I'll just have to run it at 200. I'm going to share a table I made from information I have gathered from different sources. The way I see it the car is still tight off throttle either entering the corner or a little ways into the corner and then loose in the middle and exit on throttle. That's what I have been trying to correct.  The driver just wants me to put everything back like it was in the original post so he can get the car around the track without incident. That change from 250 to 200 in the right rear didn't sit well with the car I guess. I was thinking of going with LR 200 and RR 175 but with no way to test anything until your at the track and no way to change anything once there, putting in the stiffer RF and going back to 225 / 250 may be the best shot for a stable setup. You mentioned changing the rear lower trailing arms. We set them up like that so we would have rear steer but maybe a lower roll center would outweigh the need for rear steer? Rear roll center is sitting at 20 inches up right now. The lower right rear trailing arm front is at 10 3/8 and the back is at 8 5/8. That's with it sitting in the top hole. Remounting a larger tire and lowering frame height, I still don't know if I can make it level. |
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Post by racer5056 on Jun 22, 2023 14:20:42 GMT -6
I moved the left rear lower control arm up one hole. I moved some weight from the left rear onto the right rear. I put a 3" offset on the LF so the track width is fairly even front and rear. The LR tire is kicked out 1" and the RR is kicked in 1". I put larger tires on the rear so I have 2" of stagger and with the tire selections I can go from 1 - 3" of stagger if needed. I still have 2" of stagger up front with larger tires which helped put my roll center 2" up and 6" to the left. No spring changes as of yet.
I think I had the LR overloaded with weight which threw it up onto the RF and caused the push on corner entry. I also think the rear control arm being setup for maximum rear steer was causing the car to spin on acceleration.
The only thing left to do is try the setup.
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one8
Fourth Place
Posts: 52
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Post by one8 on Jun 22, 2023 17:06:08 GMT -6
Good luck. Let me know how it goes. Again, the driver is a huge factor in car setup.
I'm put a slightly stiffer compression shock in the RF. Hopefully that'll slow it down enough to keep it from bottoming out too hard. I was pretty sore last Sunday!
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Post by racer5056 on Jun 23, 2023 16:48:00 GMT -6
Have you thought about putting a bump stop between your frame and lower control arm to help with bottoming out? I cut a small piece of thick rubber I had laying around and put it on the front of the control arm. There isn't much left on the shock for travel after I cut a part of the frame away. I'm sure the rubber won't hurt anything.
If the car is still pushing on entry and loose off, I'll move the right side tires out and the left side tires in and see if that helps in the feature.
Yeah the driver doesn't help. He wants to go full bore around the corner instead of braking early and getting back on the throttle in the middle. His engine is more powerful that the little crate motors everyone else is using so he doesn't know how to decelerate and accelerate correctly in the corner without the car wanting to run everyone over.
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Post by racer5056 on Jun 24, 2023 21:08:55 GMT -6
Car is junk. Won't get any better than last place no matter how many different ways it's setup. It's time to stop wasting time on it.
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one8
Fourth Place
Posts: 52
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Post by one8 on Jun 26, 2023 18:12:36 GMT -6
We can't run bumpstops of any kind. I'll get the shock pulled out this week and see what's up. I'll probably get a heavier tie down shock for it anyway. The RF shock is 2" shorter that most. So I'm sure that isn't helping either. Got 2 weeks before we run again.
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