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Author Topic:   Rear spring location
istock59
Member
posted October 01, 2003 08:42 PM
Okay, stock metric 4-link rear suspension. By rules, we can move the spring locations, but 50% of the spring must remain over the axle housing. I've ran most of the season with both springs on the front side of the housing. But recently moved the right spring to the back side of the housing. And the car seems to hook up better off the corner.

Any thoughts on this or am I feeling something that really isn't there??? Is there any benefit to doing this, or am I just wasting my time?

I know the fancy 4-bar LM suspensions mess with spring locations, but they use birdcages and such...

BIGDADDYBOZ
Member
posted October 01, 2003 10:08 PM
I have a friend that did this on his Imca stockcar and he said it made a huge difference.


ssaamm
Member
posted October 02, 2003 08:13 AM
Hey istock, Could you either email me, or post more details about your findings? I am looking at my rear suspension for better grip, and your experience may help me a bit.
I used my stock location last year and I was trying harder to stay in front of the rear end of my car than I was to raceing for possitions.
Thanks in advance.
Sam


cd2
Member
posted October 02, 2003 08:46 AM
istock59 with the R.R.behind the axel an L.R.in front the car should stick the R.R. better going in as you get off the gas.When you get off the gas an the pinion drops the R.R. mount raises up an this helps to keep pressure on that spring an does not let the car get to loose going in.When you get back on the gas an the pinion tries to raise back up it lifts up on the L.R.spring.With this lifting and the weight transfer to the rear on accel.it will load the L.R. quicker an more helping the car to drive off the corner better.On the stock 4 link you useally do not have a lot of pinion up an down but what you have you are getting more use from it.Also with the L.R. in front that makes it closer to the center of mass weight which is better for off the corner bite.


istock59
Member
posted October 02, 2003 10:29 AM
That was kind of the theory I was working from cd2, thanks for confirming it. The season is over now, but I think I'll start with this setup for 2004. Was also thinking about softening the OEM rubber bushings in the upper arms, to promote more movement of the pinion angle and giving more rotation to the staggered rear springs. The lower arms have urethane bushings, so any "give" is done thru the uppers.

One thing I should mention, because of shock location rules, when I moved the RR spring behind the axle, I had to move it 2" inward. That would have changed the effective spring rate that the RR tire sees too. So I really don't know which move (rearward or inward) made the car bite better. Regardless, it's all about driver perception, so if it "feels" better, do it...

ssaamm, I only ran this for two races, and at tracks I'd never ran before. So I can't tell you that it really is better bite... That's why I was posting, trying to get more info regarding!!

cd2
Member
posted October 02, 2003 12:29 PM
istock When you moved the R.R. spring in the 2" that gave the car the same effect as softening the spring. This helps the car turn in better an coming off helps it to load L.R.more.The faster you can run the corners the faster down the straight aways.Corner speed is what wins races.Don't get carried away with to much pinion movement,Work with L.S.,rear an cross weight.Weight placement is what makes you fast from corner entrance,through an off corner. cd2


ssaamm
Member
posted October 02, 2003 08:45 PM
any idea how to figure out how much a shock rate is affected by moving it in or out?
Thanks again guys


cd2
Member
posted October 03, 2003 10:49 PM
ssaamm I have always been told it does not change dampening rate of a shock to move it closer to a wheel or farther away.A shock is a hydrolic dampner.Move it closer an the travel becomes more like 1 to 1,move it away from the wheel an the shock moves less. With the shock mounted straight up you will have the full rate of the shock.As youlean the shock over you loose some of the effective rate,such as 10 degrees you would have like only 97% of the shock rate. You can call Walter Stanley @Pro Shocks an he can explain much better an give you a lot of good info. on shocks an springs.The ph.# is 770- 995-6300 cd2


BIGDADDYBOZ
Member
posted October 04, 2003 02:39 AM
When I originaly posted on this subject I forgot to say My friend was Mike Nichols and he told me moving the springs made the diff from wining to losing.


ssaamm
Member
posted October 04, 2003 06:36 AM
cd2, I'm sorry, I meant spring rate not shock, because you said this to istock "When you moved the R.R. spring in the 2" that gave the car the same effect as softening the spring."
I hear that I'll be swapping my 7.5 for an 8.5 figured I get some extra related info while I was at it.


cd2
Member
posted October 04, 2003 12:03 PM
ssaamm Yes it will make a difference when moving the spring in or out.I would place the rear springs so the tires will not hit the spring when going through the corner with the deepest off set wheel on the car.Like on the R.R.if you run a 4" off set an the track goes dry you can put on a 6" an this will tighten you back up.Not only does it move the R.R.closer to the center of weight it also has less leverage on the spring as making it stiffer an planting it harder going in.It also will make your center to center rear tracking move left 2" an this helps from center to off corner.When the track is heavy with a lot of bite an you are tight through the corner you can put on a 2"off set an move the R.R. out to loosen the car.This gives more levrage on the spring an softens it putting les pressure on it an takeing away side bite loosening the car.Also this makes your tracking wider moving you 2"to the right of the center making the rear push the car loose from center out. Example with the 6" off set on or how ever much i could run without tire hitting the frame place the springs 2" from the side wall of the tire an then if you can work out front an rear tracking where you can run an offset allowing a change in an out for these effects that is best cd2


cd2
Member
posted October 04, 2003 01:03 PM
ssaamm Lets go to the front springs an wheels .useing this for an example.Front springs 900-900 rear 250-250.This is to try an help you to understand.watch it open a big can of worms an cause a mess.As i said useing a spacer or diffrent offsets on the rear will tighten or loosen the car.You can tighten or loosen the car with offsets on the front also.With our spring setup if the track goes dry an the car gets loose you can move the R.F.out an the car will tighten up .As you move the R.F.out it has the effect of softeing the spring from more leverage an the L.F.an R.R.will carry more load decreasing crossweight an tighting the car going in an if you look at your tracking you will see where it will help to make you tight in center an off.When the track has a lot of bite an you are tight you can move the R.F. in an it will loosen the car.Moving the wheels in or out changes the distance from wheel to the center of mass weight,changes the leverage on the spring or spring rate changes tire loads an side bite. Always place springs an shocks as close to wheel as you can alowing for wheel changes an do your changes with offset,more or less depending on if you need to be tighter or looser.If your right side wheels are lined up front to rear which ever wheel you move in will stick harder an which ever you move out will stick less.Left side weight,rear weight an crossweight is very important for corner entry,mid corner an corner exit .The fastest car in,around an off is the car out front.Anything i can help with,will be glad too. cd2


ssaamm
Member
posted October 04, 2003 03:44 PM
cd....all I can say is thanks man, you make a lot of confusing stuff make sense.


DL406
Member
posted October 06, 2003 10:18 AM
Mark Ortiz presented some info on this in his Jan 2003 Newsletter, Spring placement on triangulated 4-link.


o5racer
Member
posted October 06, 2003 11:09 AM
How do I get on his mailing list?


DL406
Member
posted October 07, 2003 11:01 AM
http://www.auto-ware.com/ubbthreads/ubbthreads.php Look in the Knowledge-Base section


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