Race car suspension Class

[Ranger Mike]

We found out the top link mounting point on the rear end was same setting as from the Port City factory. We are running 58% left side weight so the distance from right rear tire centerline to tip link mount was off 6". since we can only use solid links , no springer top link or spring trailing arms, the mount location is vital to good tire hook up. As found distance from rt rear CL was 32" on 66" rear track width. So 58% left side weight means the mount point is 66 x .58 = 38.25" and changing it means both rear tires are loading the same.

 

[UFO]

Hi RM I think with the top link or pull bar setup, it acts similar to a torque arm. On a TA rear, if you have live birdcages, the balanced load setup would have the front mount point of the TA on a line starting at a point where a line projected back from the CG, square to the rear, meets the front to back center of the rear. The other point defining the line is a point on a transverse line from the CG, to the right with the distance from that point to the CG being equal to the distance from the CG to center of the rear, times the gear ratio of the rear. Any mount point on that line should load the tires proportionally to the left side percentage. The difference with the pull bar is the upward vector at the front would not be the same and would vary with the angle and the vertical distance between the pull bar mount point on the rear, to the lower trailing arm mount points. I think a drawing would explain this better, but I don't have time right now.

 

[Ranger Mike]

not replying (see previous page).
nuff said!

 

[UFO]

Sorry, there is a mistake in the previous post. The transverse or lateral distance should be the distance from the CG to the axle centerline, times 1 over the gear ratio. lateral distance = CG to rear / gear ratio

 

[drobbie]

Ranger Mike,
I was reading through your posts on rear steer and can say I am with you on it having a positive effect on cornering. We experimented with it late last season and found good results. What I am now curious about is when making the adjustments for rear steer is it better to make the adjustments at the rear end or at the chassis. In other words does raising the front of the trailing arms (chassis mounts) have a different effect than raising or lowering the rear of the trailing arms (rear mounts)
Thanks

 

[Ranger Mike]

i have not studied the benefit/drawback to adjusting on front chassis mount vs rear end mounts. If the rules let you adjust in rear roll steer then go with the easiest accessible adjustment. Now if the rules are more stringent, and not clearly telling you that you can do this, (Smokey Yunick) then you have to be a little bit clandestine in dialing in this advantage. You can buy offset bushings. You can grind in a slot to give this adjustment and the large washer should cover it up. Depends. But having the ability to have a wheelbase change is a definite winner!

 

[cearnold23]

Mike,
I am working with a suspension that has a modified watts link to located the rear axle in the car longitudinally (sprint car) and no one in the business can tell me how to locate the instant center. As i understand it with this style of suspension the IC move drastically as the suspension travels. I have looked for programs to find it but have come up empty. Any insight on have to find the IC would be greatly appreciated
Thanks

 

[Ranger Mike]

Why you worried about the IC ?? Look at the rear roll center!
The part about the IC moving drastically , to me, does not matter. The RC will be more stable than the Panhard bar setup.

The Roll Center of the Watts linkage is the center point mount of the Center Link. This set up eliminates the slight lateral movement that the panhard bar has. The watts is a better deal for straight line control from a design standpoint. James Watt invented this when he made the first practical steam engine.

It is a more complex set up (and heavier) because the main pivot point is the roll center height and is not easily changed.

Pic is from Circle Track Suspension by Forbes Aird , i got a copy at Jegs or go on line Motorbooks International, Powerpro Series

 

[cearnold23]

I need to know the IC bc we are using the watts link in place of a 4 link.

 

[Ranger Mike]

http://performancetrends.com/SuspAnzr.htm

this may be your best tool. call Kevin at performance trends

 

[UFO]

cearnold23,

On a true watts link, with equal length rods, there is no IC because the center pivot is a straight line motion that is perpendicular to the rods when they are positioned parallel to each other.

 

[cearnold23]

Unfortunately this is not equal length rods.

 

[Ranger Mike]

that is NOT a Watts linkage. It is a swing arm suspension. Sometimes called a Z link. As far as this photo shows me. I can not see all the workings of it but appears to be a variation of the swing arm with torsion bar.
I suggest you buy I.M.C.A. Modified Racing Technology from Steve Smith Autosports. he has good intial settings outlined in it.

 

[Ranger Mike]

Without seeing your set up, another guess is the Cantilever design. This is from Short Track Chassis Set-up by Duke Southard

 

[Hiredgun161]

3/8 mile paved track late model BBSS setup
This email was sent to me and driver wants to have it posted to help other racers. I am keeping his name and address private but thank him for permitting the sharing of this project. We will be going thru the set up process changing from a ½ mile track package to a 3/8 mile setup. Driver walked the 3/8 track and majority of cars there are BBSS so the track is not that bumpy to take air off the car. Note - you do not need the latest greatest new chassis to be super competitive.

Note this is a Big Bar Soft Spring setup.

He says -
I have a ~2005 Port City straight rail asphalt
Late Model. It is a BBSS chassis.
Here is how the car was setup to run a ½ mile asphalt track with sweeping flat turns. The car turned its fastest lap ever with this setup and was on rails. The car was scaled after the race (topped off fuel). Here are those numbers;TOTAL WEIGHT = 2702 lbs.
% Left = 57.8
% Rear = 49.8
% Diagonal = 55.2
*Swaybar Unhooked
RIDE HEIGHTS
LF = 4" RF = 4" RR = 4-1/2" LR= Floats
CORNER WEIGHTS, SPRING RATES, ETC.
LF = 713 lbs (26.4%) 180 lb spring. Camber +5½°
Caster +2°
RF = 642 lbs (23.8%) 185 lb spring. Camber -1½°
Caster +4°
LR = 850 lbs (31.5%) 225 lb spring.
RR = 497 lbs (18.4%) 400 lb spring.
SWAY BAR
1⅜" splined w/ 13" arms. Calculated @ ~532 lb.
SHOCKS
LF = S7Z RUSH7 16-2 COB
RF = 33-253015 RUSH DIRT LATE MODEL 12-2
LR = F4-B46-0210-HO RUSH7 6-1.5
RR = F4-B46-0210-HO RUSH7 4-3
************Going forward, I will be racing this car on a ⅜ mile asphalt track. The whole track has 12° banking. The radius of both turns is ~161', which would be a diameter of ~322'.
Would you be able to put together a baseline setup package for this track?
Ie. Spring rates that will work with my 1⅜" sway bar (which I calc'ed at a rate of ~ 532 lbs), camber, caster, etc.

3/8 mile track rules - American Racer tires AR153 10 inch slicks

-Total weight will be Increasing to 2800 lbs. in 2022
- NO bump stops.
- 4" ride height.
- 58% max left side weight.***CURRENT CHASSIS CONFIGURATION***
NOV 27, 2021
Take note these numbers are with INCORRECT TIRE STAGGER. These numbers are with;
Front Stagger = 2¾"
Rear Stagger = 2½"
This was the only combination I had available.
One of the top teams suggested I run;
1½" FRONT STAGGER.
3" REAR STAGGER.
I previously did the math and 3" rear
stagger is about right.
TOTAL WEIGHT "RACE READY" = 2747 lbs.
Left = 57.0% (1567 lbs)
Rear = 49.3% (1357 lbs)
Diagonal = 54.2%* (1491 lbs)
*Swaybar Preloaded one (1) turn
LR BITE +311 lbs
FRAME RIDE HEIGHTS:
LF = 4" RF = 4"
LR= ~4" (floats) RR = 4-1/2"
CORNER WEIGHTS, SPRING RATES, ETC.
LF = 733 lbs (26.7%) 180 lb spring. Camber +5½°
Caster +2°
RF = 657 lbs (23.9%) 185 lb spring. Camber -3°
Caster +4°
LR = 834 lbs (30.4%) 225 spring rate
RR = 523 lbs (19.0%) 400 spring rate
SWAY BAR
1⅜" DIAMETER, SPLINED.
3 PIECE W/13" ARMS.
CALCULATED @ ~532 LBS.
SHOCKS (BILSTEIN)
LF = S7Z RUSH7 16-2 COB
RF = 33-253015 RUSH DIRT LM 12-2
LR = F4-B46-0210-HO RUSH7 6-1.5
RR = F4-B46-0210-HO RUSH7 4-3
TIRE PRESSURES COLD
LF = 12 psi
RF = 18 psi
LR = 10 - 12 psi
RR = 18 psiInitially, my final rear gear ratio will be 6.02.
I do expect that to change.
A 6600 RPM rev limiting chip is currently installed. Could go to 7000 RPM in the future. Any more would be pushing past what the camshaft has to offer. No sense in beating a dead horse!

this is quite similar to the setup i run in my 04 port city, exception by track rules the front springs have to be a minimum of 325 to get a hundred pound weight break.

 

[Ranger Mike]

thanks for the input..always good to get this from other racers! HAppy Easter!

 

[Ranger Mike]

Upside down engine- This ought to cause some interest..
Local track rules state any production engine of any displacement may be used. The only restriction is one 4 barrel carb and no multi coil ignitions. Crank shaft center line is minimum of 10 1/2 inch above the pavement.
Private message to me was -
Is there a benefit if we can mount the V8 engine upside down so the heads are lower than the crankshaft center line.
Wow - have to think about this. Will it work? will center of gravity improve? Transmission is a manual 4 speed and can be changed over pretty easy on shift linkage. Clutch won't care.
Dry sump is legal so have to check all the oil going to pistons unless we really tighten up the clearances. Oil cools the bottom of the pistons and carry away heat when it drips back into the pan. This would not happen. Wonder how the Radial engines handle this?

Anyway its Race day weekend for Indy and Charlotte 600. What do you think?
Novel but very legal!

 

[Ranger Mike]

https://ww2aircraft.net/forum/threads/daimler-benz-db-605-oil-system-i-dont-understand.46596/
Looks like the Germans did this before WW2 with an Inverted V engine. Mercedes again, I copied some post from above discussion.
Oil is pumped under pressure to the crankcase and runs by gravity down a path between the cylinders into the camshaft covers where there are camshaft driven pumps to return out to the header tank. I'm not certain of this but, in regard to the collection of oil in the cylinder bores, I would suggest that it probably does but that, when the engine is running, the oil is constantly being splashed back up into the crank case to eventually run down to the camshaft covers.
The inverted engine did pose problems with oil supply and consumption. The British sent a team to Germany immediately after WW2 to investigate the German engines and speak to German engineers. The British team comprised men from the Ministry of Aircrat Production and all the British aero engine manufacturers (including Armstrong Siddeley Motors, Bristol Aero Co., D. Napier & Son and of course Rolls Royce). They produced a report, 'Comments on Visit to Germany, July 24th 1945 to August 12th 1945'. In it they recorded that Daimler Benz engineers would have preferred an upright 'V', but the inverted layout was a requirement of the RLM (actually it predated the RLM, back to 1928).
They made the point that it was very difficult to get even oil consumption as the rotation of the crankshaft caused one bank to get more oil than the other. It's why the compression ratio is lower on one bank than the other.

The same issue technically applies to many radial cylinders but the speed the pistons move ensures that the vast majority of the oil gets thrown up and finding its way into the sumps while the engine is running.

Once the engine stops naturally relatively large amounts of oil accumulate in the down facing cylinders on radials so it is essential that the engine is pulled through before starting to ensure there are no cylinders with a hydraulic lock.

 

[LogicIndustries]

The first thing that occurs to me, aside from whether it is technically possible at all, is that there is a lot more than 10.5" of engine above the crankshaft centerline when installed "normally" (in an American style V8 anyway), so if you flip the thing over, you'll have to raise the entire assembly up enough to keep the carb off the ground (speaking of, I think the carb might protest mightily about being mounted upside down, floats needing gravity to work, etc).

If you have to raise the whole assembly, that brings the clutch and trans up with the rest of it, which would appear to make the CG situation worse not better, nevermind the drastic change in driveline angles, etc that would entail

I guess you could use some kind of drop-down box to put the transmission input shaft well below the clutch housing, but that's adding weight just to try and shift the CG, and if you're going to do that, it's a lot faster and a hell of a lot cheaper to just hang some lead down near the track surface.

It's an interesting thought experiment, but if you ain't got an F1 tier budget, I doubt it would be possible, and if you had the money, I doubt that the juice would be worth the squeeze.

 

[Ranger Mike]

great feed back. it is assumed the carb would be mounted on custom tubular manifold. Carb on front of engine ( cooler than on top) and mounted normally so needle and seat would work. The typical V8 setup up again 'assumes ' the cam shaft center is the Center of Gravity (COG) about 17 1/2" from pavement. I just have to look at the change in crankshaft height vs traditional 10 1/2" height.

One big thing is frame width but since this is Super Late model chassis and
totally fabricated, no problem. Have not had time too yet. But according to research it should work. If it has handling advantages if would be affordable.
One consideration on drive line is if engine is reverse rotation you have to flip the rear end 180 degrees and this adds height to pinion center ( another mind f*#k drill) but hey, its a race weekend and raining here!

 

[LogicIndustries]

Reverse rotation would lend handling benefits for ovals, but that would be a separate modification, 'cause reorienting the motor 180° along the axis of the crank would not change the direction it spins on its own.

All I can say is that if they do pull it off, you got to take pictures for us to see.

 

[Ranger Mike]

All you need to make engines reverse rotating is a reverse starter and camshaft and gear drive both commonly available in marine engines

 

[LogicIndustries]

All you need to make engines reverse rotating is a reverse starter and camshaft and gear drive both commonly available in marine engines

Indeed. But it's still a modification that would need to be done.

I wish them luck, and I want to see pictures of it when it's finished.

 

[Ranger Mike]

I did some research and here are the required modifications-need to tool up new bell housing with transmission mount holes re-drilled. Shift linkage and clutch should be OK. Invert engine and make new engine mounts on chassis and engine. chances are you have a front motor plate so pretty easy. New to go reverse rotation and get reverse starter and camshaft and gears. Need to rework rear end flip it 180 degrees and weld on new spring perches. Need to fabricate dry sump system. need to make new headers. Need new intake system. Need to rethink ignition with crank sensor not distributor. I would go with electric water pump. Disadvantages - Crankshaft of engine and center line as well as Transmission and drive shaft ( approx. 50 lbs of mass) 6 inch higher than before. Advantages - we have reverse rotation assisting the cornering by planting force on left front wheel turning cornering. We have the 95% of the entire engine mass of 400 lbs. located below the crank center line. Only one half of the crankshaft and the oil pan are over the center line. Previously we had 400 pounds above the crankshaft center line. That is half the crankshaft, half of the connecting rods, all pistons and wrist pins and Cylinder heads were 16 inch above the pavement to 34" above pavement ( cylinder heads) the heads now are only 4" above pavement. this does not include headers and intake. A little later i will work up how this impact s on cornering but intuitively this could be very significant!

 

[Ranger Mike]

Here is the major benefit- From Circle Track Suspension by Forbes Aird
When the COG is under the RC the body rolls to assist in the corner, exactly opposite of what we now have.

 

[Outlaw850]

We found out the top link mounting point on the rear end was same setting as from the Port City factory. We are running 58% left side weight so the distance from right rear tire centerline to tip link mount was off 6". since we can only use solid links , no springer top link or spring trailing arms, the mount location is vital to good tire hook up. As found distance from rt rear CL was 32" on 66" rear track width. So 58% left side weight means the mount point is 66 x .58 = 38.25" and changing it means both rear tires are loading the same.

Hi Ranger Mike,
I stumbled across this website, and from what I've been able to soak up so far from your posts has helped me out tremendously, and I appreciate your input. I have a question concerning the correct top link mounting point as illustrated in your post above. I hope that it's not a stupid one, but I'm kind of perplexed as to how you would go about changing the mounting point for the top link on your rear end. In your illustration, it appears that the link is not connected to the center of the rear end. Maybe I'm interpreting that wrong, but could you explain how you would make the top link mount from the chassis to the rear end a straight line without shifting the entire rear-end housing over to the left? (or is that what you need to do?)

 

[RaceMan12]

Outlaw, This is what we did , probally different rear than yours but hopfully it may help.

 

[Ranger Mike]

I sincerely thank you both..please let me work up a teaching point from you racers but you both are sure as hell going to the winners circle soon!
do not forget the card board box...for the trophy!
rm

 

[Ranger Mike]

Thank you Racerman,,exactly what I was talking about! 3rd link properly connected. Good job!

Why is top link mount so critical?

The top link is the rear end link that pulls the race car. This is why the spring type top links have a compression spring to lessen the rear end loading when you get back on the gas at corner exit. This top link directs all rear end force to the chassis. The rear tires grip the track and try to pull the rear end to the rear as the trailing arms on the bottom push the car to the front and try to climb up under the car.

Why location matters- In road course car set ups you want everything set up 50/50 % weight bias, so all front tires scale close to equal and the rear end tires scale equal.

Not so on left turn racers where you want a left side weight bias. When in a turn you want the left side weight rolling over to the right side to assist the car with better traction (tire grip).

Correct location of the 3rd link mounting is a real help so the tires are pulling on the third link equally otherwise when you step on the gas, one tire will bite more than the other and shoot you toward the outside of the track or the inside.

Think of a shipping pallet on the garage floor. You hook a chain on the pallet , not at the center but a foot to the right of center. Now pull the chain, The pallet will cock to the right.

The pallet example is a way to show that you must hook up a locked rear end so both tires bite the same. The pallet example above shows that the right side moves first because there is less weight on that side. Remember down force! We do not really cock the rear end but what really happens is more force is added to the side of the car the link is closest to. In this case we have more force added to the left rear tire ( same as adding a lot more wedge) so we create an off corner PUSH condition.

If you run a 10 year old chassis check the 3rd link mount. When it left the chassis factory back in the day the car was set up with about 52% left side weight. Today you may be running 58% left side weight. This means you can be 2 to 3 inches off the correct location. It is so easy to cure and eliminates one huge rear end traction problem, so fix the 3rd link mount. So screw the chassis builders old specs. They are no longer valid as the chassis has been hacked on so much over the years.

So you need to mount the top link as my post 81 on page 3, post 253 on page 8, post 707 page 21 show.

 

[Ranger Mike]

3rd link mounting 253 8
3rd link mounting 707 21
3rd link mounting 81 3
3rd link mounting 1603 46
3rd link spring rate 261 17
4 link I C 301 16
4 link rear suspension 132 9
Ackermann 646 33
Aero Burnulli effect 574 29
Anti Dive 403 21
Anti Dive 492 25
Anti Squat 314 16
Anti Squat 327 17
ARB (sway bar) front 357 18
ARB (sway bar) front 358 18
ARB (sway bar) rear 521 27
Benchmark the car 285 15
Big Bar Soft Spring 1118 56
Big Bar Soft Spring 362 19
Big Bar Soft Spring 381 20
Big Bar Soft Spring 568 29
Bump steer 13 1
bump steer 643 36
bump stops 220 11
Camber build 663 37
Caster 319 16
Center of Gravity 563 29
Chevelle rear end 830 42
design suspension from scratch 388 12
design suspension from scratch 566 19
Eccentric 229 12
Front RC location 251 9
Front RC location 691 24
Fuel Cell location 272 14
Fuel Cell location 505 26
Gas shock tuning 217 11
Heat cycle machine 572 29
Hotchkiss suspension 353 18
jacking effect 229 13
jacking effect 691 35
jacking effect 811 41
jacking effect 879 44
Lead - front end geometry 1369 69
leaf spring 789 40
leaf spring 1322 67
Light is right 560 28
Metric clip street stock rear end 301 16
Metric clip street stock rear arb 521 27
Metric clip street stock 830 42
Metric clip street stock 832 42
Metric clip street stock rear steer 858 43
Metric clip street stock 1264 64
Metric Spindle swap 284 15
Metric Spindle swap 809 41
Motion rate - rear 308 16
Myth of Weight Transfer 228 12
Myth of Weight Transfer 676 34
Myth of Weight Transfer 811 41
Myth of Weight Transfer 676 34
Myth of Weight Transfer 228 12
Myth of Weight Transfer 676 38
Myth of Weight Transfer 470 24
Panhard bar 246 13
Penske shocks 217 11
Polar moment 562 29
progressive spring 216 11
Race Line 667 38
RC Height 229 12
rear end camber 1326 67
Rear end Instant Center 301 16
Rear roll steer video 1200 60
Rear roll steer video 858 43
rear steer 116 8
rear steer 81 5
Ride height 552 28
Roll center & offset 229 8
Roll center distribution 229 8
Scrub radius 325 17
Shocks (dampers) 703 40
Spindle Angle 325 17
Spindle Angle 332 17
spring rate calculations 19 2
spring rate calculations 589 30
Spring rate vs wheel rate 17 2
Squaring the car 270 14
Squaring the car 479 24
Stagger 36 3
Stagger calc 36 2
Stagger tape 426 27
Street Stock 1314 66
Street Stock 1264 64
Street Stock 830 42
Street Stock 832 42
Stringing the car 269 14
Stringing the car 293 15
Tire down force 62 4
Tire temp readings 468 24
Track width 255 13
Track width 264 14
Track width 322 17
Track width 505 26
Upper A-arm angle 312 16
Wheelbase 264 14

 

[Outlaw850]

Thank You RaceMan! That picture is very helpful.

 

[Outlaw850]

3rd link mounting 253 8
3rd link mounting 707 21
3rd link mounting 81 3
3rd link mounting 1603 46
3rd link spring rate 261 17
4 link I C 301 16
4 link rear suspension 132 9
Ackermann 646 33
Aero Burnulli effect 574 29
Anti Dive 403 21
Anti Dive 492 25
Anti Squat 314 16
Anti Squat 327 17
ARB (sway bar) front 357 18
ARB (sway bar) front 358 18
ARB (sway bar) rear 521 27
Benchmark the car 285 15
Big Bar Soft Spring 1118 56
Big Bar Soft Spring 362 19
Big Bar Soft Spring 381 20
Big Bar Soft Spring 568 29
Bump steer 13 1
bump steer 643 36
bump stops 220 11
Camber build 663 37
Caster 319 16
Center of Gravity 563 29
Chevelle rear end 830 42
design suspension from scratch 388 12
design suspension from scratch 566 19
Eccentric 229 12
Front RC location 251 9
Front RC location 691 24
Fuel Cell location 272 14
Fuel Cell location 505 26
Gas shock tuning 217 11
Heat cycle machine 572 29
Hotchkiss suspension 353 18
jacking effect 229 13
jacking effect 691 35
jacking effect 811 41
jacking effect 879 44
Lead - front end geometry 1369 69
leaf spring 789 40
leaf spring 1322 67
Light is right 560 28
Metric clip street stock rear end 301 16
Metric clip street stock rear arb 521 27
Metric clip street stock 830 42
Metric clip street stock 832 42
Metric clip street stock rear steer 858 43
Metric clip street stock 1264 64
Metric Spindle swap 284 15
Metric Spindle swap 809 41
Motion rate - rear 308 16
Myth of Weight Transfer 228 12
Myth of Weight Transfer 676 34
Myth of Weight Transfer 811 41
Myth of Weight Transfer 676 34
Myth of Weight Transfer 228 12
Myth of Weight Transfer 676 38
Myth of Weight Transfer 470 24
Panhard bar 246 13
Penske shocks 217 11
Polar moment 562 29
progressive spring 216 11
Race Line 667 38
RC Height 229 12
rear end camber 1326 67
Rear end Instant Center 301 16
Rear roll steer video 1200 60
Rear roll steer video 858 43
rear steer 116 8
rear steer 81 5
Ride height 552 28
Roll center & offset 229 8
Roll center distribution 229 8
Scrub radius 325 17
Shocks (dampers) 703 40
Spindle Angle 325 17
Spindle Angle 332 17
spring rate calculations 19 2
spring rate calculations 589 30
Spring rate vs wheel rate 17 2
Squaring the car 270 14
Squaring the car 479 24
Stagger 36 3
Stagger calc 36 2
Stagger tape 426 27
Street Stock 1314 66
Street Stock 1264 64
Street Stock 830 42
Street Stock 832 42
Stringing the car 269 14
Stringing the car 293 15
Tire down force 62 4
Tire temp readings 468 24
Track width 255 13
Track width 264 14
Track width 322 17
Track width 505 26
Upper A-arm angle 312 16
Wheelbase 264 14

Thanks RM for all the information you provide and the reference guide to various topics. Being new to this forum, this information helps me quickly find information and hopefully, will keep me from asking the same question twice...LOL. THanks Again!

 

[RaceMan12]

@Ranger Mike
I've looked( and probally missed it lol) but could you tell me your thoughts on a panharb bar running from left rear just inside the wheel and about 2 inches infront of the axel housing to the right side chassis about 10 inches in front of the axel . So roughly 8 inches forward on the right as compared to parallel to the rear. I have seen this on a few pavement oval track cars and have thought it may give added bite on throttle.
Thanks !!

 

[UFO]

Thank you Racerman,,exactly what I was talking about! 3rd link properly connected. Good job!

Why is top link mount so critical?

The top link is the rear end link that pulls the race car. This is why the spring type top links have a compression spring to lessen the rear end loading when you get back on the gas at corner exit. This top link directs all rear end force to the chassis. The rear tires grip the track and try to pull the rear end to the rear as the trailing arms on the bottom push the car to the front and try to climb up under the car.

Why location matters- In road course car set ups you want everything set up 50/50 % weight bias, so all front tires scale close to equal and the rear end tires scale equal.

Not so on left turn racers where you want a left side weight bias. When in a turn you want the left side weight rolling over to the right side to assist the car with better traction (tire grip).

Imagine a you have a log chain and a 5 foot x 5 foot x 4 foot box. You want to pull a 2800 pound box and inside a spare engine located to the left side and a few old tires filling up the other side.

You want to find the center of mass so the box will slide straight and not pull to one side. If you use the centerline of the box and hook the chain at 2 ½ foot. The box will not slide straight as you pull it. You have not pulled the box on its Center of Mass. If the top link is offset to the right of the center of mass, the right rear tire will be loaded more and the left rear tire will be loaded less. We have a push or understeer situation just like when you have too soft a right rear spring. Right rear has too much traction. This is why you have a mystery induced push on corner exit. You are not loading the tires equally when you step on the gas coming out of the turn.

So you need to mount the top link as my post 81 on page 3, post 253 on page 8, post 707 page 21 show.

 

[UFO]

Hi RM
I like your analogy with the box. Wouldn't that be similar to the rear pusing that box. If the right rear tire was loaded heavy and have more traction. Wouldn't it turn the box to the left and vice versa for the left tire?