4 link help

[prostreet34]

Well I have most of the bugs worked out of my dart 427 sbc build that some of you have helped me with. I'am in FL. so we get to drive em all year round. Car is an outlaw bodied 1934 chevy with their prostreet frame, no cage.

For now, street car only.

Suspension is parallel 4 link with panhard bar, all pretty basic stuff.
Tires are 21.5x33 M/T sportsman (very old and hard)
Car weighs 2600lbs.
Rear coil overs have 275 springs
Front suspension is mustang 2

Problem being, car is quite spooky to drive, gets away from you real quick. I know the car is sprung to stiff, very little shock travel. Doing some checking on tires now, may even drop down a size in width to get the suspension travel needed.

Looking for some basic starting point advice or some recomended reading. (articles or books)

Any thoughts on brand of rear coil overs and spring rate?

Thanks,
Jason

[ComaxRacing]

Define "SPOOKY"


Corey

[prostreet34]

Corey,

Maybe the word scarry would suite you better.

[prostreet34]

Looking to improve my set up and not just throw soft tires at it.

[ComaxRacing]

I guess what I meant was, does the car go sideways,does it break the tires loose. ETC. My car is scary to drive too.:D


Corey

[prostreet34]

Yea, I guess a better statement would be lack of traction. Car drives very nice and straight down the road, but even to just roll into the throttle at 45 mph the rear of the car feels like it raises up and just blows the tires off. I maybe wrong but my thinking was the car should squat in the rear not raise. I'm not trying to put crazy power to it, maybe 525hp. Thats why I'm thinking bar angles, shocks and springs.

[ComaxRacing]

That is what I was talking about. It sounds like you percentage of rise is way to high. With a four link you can set the rear to rise or squat depending on the bars. Do you understand the concept of "instant center"?

I am going to stop there untill I hear from you, if you do understand "instant center" then I can explain how to possibly adjust out the problem you have.


Corey

[want-a-be]

Sounds like you may have some bump steer in it if it's seems darty when you are on it hard. But right out of the box,...it could be alot of things. Best thing to do is let us know everything that is happening with the car.

Don

[lun40119]

Ohhhhhh Don and Corey here we go. Get out the chalk :D

[want-a-be]

Ohhhhhh Don and Corey here we go. Get out the chalk :D

LOL...if you ever took the time to measure out your suspension you'd be able to figure out what changes you need to be making. Shocks will only help so much.

Don

[prostreet34]

Thanks guys,
May be a few days before I get some IC and CG numbers back to you, have family in town.


Don,
I don't think its a bump steer isue, the car is controlable, just a very lack of forward bite.

[want-a-be]

AAAhhh...ok..Sounds like you were leaning towards a darty type problem.

In the ic length and it's height,...I'd start out with something like 50"-55" on your set-up. Try to get it about 6" off the ground for starters. What are you doing with the bottom like bar. Level, or is the front of the bar higher or lower then the rearend mounting point? How much agnle do you think the top bar has. Does it look like alot or is it pretty much flat?

As far as rear springs....I'd start with around 110-125# srpings. What %age of the cars weight is on the rear wheels?

What springs are you running up front?

Gear, rear tire size, and tranny type?

Don

[lun40119]

LOL...if you ever took the time to measure out your suspension you'd be able to figure out what changes you need to be making. Shocks will only help so much.

Don

I am just one of those guys that thinks more power will fix it. ;) I think once I am done this year, I WILL HAVE TO get it figured out. It is just so boring to me. :D

[ComaxRacing]

I picked up a copy of 4-link pro from performance trends a while back, once we get some IC numbers I'll plug them in and see what it says for numbers.

Corey

[prostreet34]

Not sure if it's relivent for determining good starting point for length of IC, but wheel base is 108"


length of IC 40 3/8"
height of IC 11 3/4"


top bar down 11* in front
lower bar up 2* in front

Have adjustments up or down 1" at all mounting points except top bar at rear end.

Don,
Here are the #'s I came up with, after talking with you, just haven't had time yet to move the bars.


If I do the following:
move top bar down one hole in front
move lower bar up one in the rear and down one in the front

length of IC 46 3/4"
height of IC 7 3/4"

Or if I just move the lower bar down one hole in the front
length of IC 53 1/2"
height of IC 9 1/4"

[want-a-be]

I like the last option a lil' better but I'd rather see the IC a little lower. So I'd have to go with the first option first.

What is the ride height of the chassis in the front and rear measured at the rocker panel? If you could lower the chassis in the rear an inch or 2 then I'd look pretty close at the lower one. But if lowering the chassis isn't an option then I'd make the first one my choice.

What size link bolts are you running? 5/8 or ¾ ? Do you have any room to drill some new hole in your rear end or chassis mounts?

Something I was just thinking of....How long would the IC, and it's height off the ground, be if you lower the front of the bottom bar and raise the rear of the bottom bar. Then lower the front of the top bar 1 hole?

When you get that information for us. How much above or below are these IC points from the neutral line for all 3 of the measurements please.

Hope this helps out.

A lil' off topic,...Jake,... all this came from chalk drawings on the floor...lol You can't manage what you can't measure....

Don

[prostreet34]

Measured ride height at frame 12 3/4" at rear and 8 1/4" in front, measurments are on flat part of frame, before front and rear kick ups. Car sits pretty nice, just alittle bit of rake, think I could drop the rear 1".

Link bolts are 5/8" on 1" centers.

Your thought of moving bottom bar up one in rear and down one in front
and also moving top bar down in front one hole is how I came up with option #1 in the above thread.
,
I used the asumed water pump method for finding the neutral line. I would have to think it is actually alittle lower on this car, being a fiberglass streetrod. Their just isn't much mass above the water pump center line.

From above thread:

option #1 IC is 1 1/4" below NL
option #2 IC is 7/8" below NL

If I lower rear of car 1"
drop front of lower bar one hole
and raise top bar one hole (just to keep the same angle in it) after lowering car

IC length 51"
IC height 6 5/8"
IC ends up 3 1/4" below NL, but like I said before I'm thinking the NL may actually be alittle lower than my measurements.

I think all three of these options are alot better than whats in the car now. Also starting to do some home work on replacing front and rear shocks and springs.

[want-a-be]

I Like that last option alot. Next I like the second option.

Don

[lun40119]

I like the last option a lil' better but I'd rather see the IC a little lower. So I'd have to go with the first option first.

What is the ride height of the chassis in the front and rear measured at the rocker panel? If you could lower the chassis in the rear an inch or 2 then I'd look pretty close at the lower one. But if lowering the chassis isn't an option then I'd make the first one my choice.

What size link bolts are you running? 5/8 or ¾ ? Do you have any room to drill some new hole in your rear end or chassis mounts?

Something I was just thinking of....How long would the IC, and it's height off the ground, be if you lower the front of the bottom bar and raise the rear of the bottom bar. Then lower the front of the top bar 1 hole?

When you get that information for us. How much above or below are these IC points from the neutral line for all 3 of the measurements please.

Hope this helps out.

A lil' off topic,...Jake,... all this came from chalk drawings on the floor...lol You can't manage what you can't measure....
Don

BORING................:D :D :D Ill get there gramps.

[prostreet34]

Jake,

Not that I would know, living here in FL. but I'm pretty sure it's not as bad as shoveling snow.

Jason

[want-a-be]

Jake,

Not that I would know, living here in FL. but I'm pretty sure it's not as bad as shoveling snow.

Jason

Hey hey hey Jason!!!!!! Don't be ragging on ole' Jake about his favorite past time.

:p.....LOLOLOL.....:p

Don

[lun40119]

No that sucks too.............:)

[want-a-be]

So Jason,

any update news for us?

Don

[prostreet34]

Have shocks and springs out of car to see what I have and to be sure I order correct length shocks for the ride height I want. Going to move 4 link bars Fri. and put back together with old shocks and springs. (only want to change one thing at a time) also want to get some front and rear weights on sat. before I order springs.
Jason

[prostreet34]

Don,

Car feels alot better even with only doing the bar angle changes. Not perfect yet but car just feels like it reacts better, still spins tires pretty hard but feels like it has more forward motion. Just need to complete the package with springs and shocks all around. Did get to scale car today (1320 lbs. front) (1440 rear).

Thanks again,

Jason

[Awesome Bill]

If your car just blows the tires off but maintains a straight shot, your tires are junk and most likely to hard. Get a good drag radial for street use. The heavy spring rate will not cause your problem. We like a great amount of stored energy in our springs for a hard planting rear suspension. Makes for a little bumpy ride but we don't care, this is racing. Now if your car is going hard to the right or to the left when power is applied, you have a preload problem. You can tell this by stopping the car, then crack the throttle let the tire spin. Both tread patches should be exactly the same color and width. If not you have to start with getting both to be the same. Get back to me and I will walk you threw it. It is not brain surgery here!

[want-a-be]

Don,

Car feels alot better even with only doing the bar angle changes. Not perfect yet but car just feels like it reacts better, still spins tires pretty hard but feels like it has more forward motion. Just need to complete the package with springs and shocks all around. Did get to scale car today (1320 lbs. front) (1440 rear).

Thanks again,

Jason

Thats good to hear Jason. It's always good to make steps in the right direction. Once you get the right springs and some new rubber under this thing you ought to make even more gains. Keep in touch on how things go in the future. Feel free to give another call if you need to.

Don

[Awesome Bill]

Don, tell me how you know he has the wrong springs when he has never done a patch test? Do you know what a patch test is? I explained it in my thread. Both tires have to have the same dark color on the groudn and the same width, then you go from there. I would like to learn this one? Sounds like he is just blowing his tires off to me?

[want-a-be]

Bill,

I have, and still do pay attention to the patch test. It's a very handy trouble shooting tool. But in this case his IC was so short and high it was actually hurting any possible traction. You're right Bill,...he is just blowing his tires away.

We have talked some on the phone and PMed a bit before he made any adjustments. I forget what his springs are on the rear,...but I was thinking they were in the neighborhood of 300-350 pounds. With out knowing what his front and rear weights were I took his total weight and suggested a spring weight that I would use for a given weight. His engine has a lot of set back. So we figured he would be about 52%, or so, on the rear tires. Turns out we weren't too far off by the numbers he has posted. Depending on how long a spring and shock combination he will go with, I think he should be running between 110#-125# springs. His Front springs are wrong also but I forget those numbers. His plans are to correct them also. Jason has some race experience he can tap into also. So he isn't a newb to tuning a race cars chassis. That made the conversation a lot easier. Because he understood everything we were discussing. He's pretty sharp.

As far as his IC length and height. I have a base line that I like to start out with for both SB and BB cars. N/A that is.... Usually 50"- 55" for the SB car and 55"- 60" for the BB cars. With around 6"- 8" off the ground. Those numbers have been good numbers for me on new set ups. Then tune from there. From here I look at alot of different things to get the car to react how I want it. But being at the track is almost a must for me being able to shorten the chassis tuning session. Thats when I look at the patch to see how things are looking. Theres alot of data to gather from the patch then just looking for how even they are. You can tell if you're not hitting the tires enough or even too hard. Hard to explain that though as sometimes its a judgement call.

Perfect traction is actually a fine line imo though. Too much traction and you bog the car to little and you're up in smoke, or worse,....you get a combination of the 2 and rattle your teeth out. (Tire shake) Some of the best times I see a given car run is right on the verge of losing traction. The patch will actually be a bit more narrow then the tire when that happens. Of course this is all in N/A cars. You just need to be a lil' more aggresive with the power adder cars. But even they run best on the ragged edge of traction. Wathc a fuel car leave sometime.

All this is just for forward bite though. I look at other things to decide on the amount of preload I want to give the car. Once Jason gets the forward bite under control then we will have another conversation about preload. I will say though, I think he is doing his testing on the street. The track will be a whole different deal. I doubt he ever gets the traction he would like to hook on the street. But he knows that already. Preload is going to be another long post once someone asks. Like Jasonnow knows,...and alot of others, I'm very easy to talk to and am more then willing to help out when I can. I think the price was right enough,...wasn't it Jason?...lol

BTW,...I prefer to get the chassis to work correctly before I have the sway bar, (also known as a torsion bar I believe), added to the rear end. The sway bar is a great load leveler,...might even call it somewhat of a traction control, with in reason. But I seriously frown on adding the sway bar before the chassis is lined out. It can be a huge crutch for a poorly tuned chassis.

Like I said though,...it's hard to make calls when you're not there to watch everything. Unless whoever is feeding me the data knows what to look for.

Don

Bill,... most of this really wasn't aimed at you because I know you already know most of it. It's actually aimed at the reader who doesn't know. My chassis tuning technique really has no science to it. It's just what I was taught to me by a friend, Mike Sully, and what I learned after many conversations with him and track time.

Sorry for the long post,...but books are written on the subject. Hard to fit in only a few lines.

[lun40119]

Good post geezer, thanks for sharing.

[want-a-be]

Thanks,...I appreciate that.

Don

[lun40119]

Thanks,...I appreciate that.

Don



LOL, the geezer part? ;) I know what you meant.

[prostreet34]

Don,

Just a quick update, ordered shocks, springs and tires. I ended up going the QA1 route, I've herd mixed reviews on their stuff (kinda like we talked about) But I think for what I'am doing they should be fine. The 3 or 4 times I talked to someone from their tech line they were great to deal with. They also seem to have one of the nicer coilover conversion kits for the mustang 2 set up I have.

I'am going to start out with a 200 lb 10" rear spring. I know you wanted to see it softer, but since this thing sees so much street use, I was concerned about going that light. At lease springs are cheap enough I can afford to be wrong.

I ordered a set of M/T sportsman pro 19.5 x 33 tires witch I think will have a better foot print than the 21.5 x 33 that are on it now, because of the 15" wheels that I have.

Thanks again for the advice at such a great price!!!!!

Jason

[want-a-be]

yikes,...200 huh? I'd like to see 150s at most. Maybe 12"-14" long. But like you said, springs are cheap. 250ish is what I would be putting on the fronts.

everyone can afford free....lol

Don

[prostreet34]

Yea, I was kinda afraid to tell you what springs I decided to start with. Hate to be that guy that asks for advive and then doesn't listen.

[want-a-be]

Hey,...no problem at all. It's your car not mine. You have to make the choices that works for you.

Don

[want-a-be]

Anything you'd like to report back on?

Don

[prostreet34]

After lowering rear of car 1", the IC length is at 48" and the height at 7"
The car is night and day better, even with the 200 lb. springs. Think I'am going to try a set of 150 springs, I want to drive the car some more miles first, to keep an eye on shock travel. I think the 150's will work even better, I'll just put alittle preload in them.

Going to mount new tires this weakend, using M/T sportsman pro 19.5x33. Wasn't using tubes on old tires but think I'am going to use screws and tubes on this set. Any thoughts?

Car leaves fairly straight, going to check and set upper right bar with neautral preload also need to recheck pinion angle this weakend. Then with new tires, I'll see how it wants to leave.

What are your thoughts on a gear. Old motor and converter (fairly stock) 70 mph was 2,600 rpm. New motor and converter (10" ATI treemaster) 70 mph is 2,900 rpm.

with 3.73 gear and 33" tire

I'am thinking a 4.30 gear should put my 70mph cruise speed at 3,100 and get the converter locked up and help to keep the trans. alive

I think Jake runs alot more converter, but I don't know what gear he runs.

[want-a-be]

You might want to poll the crowd about tubes in the tires or not. Myself,.. I had better luck not running tubes. Noone I know that races, circle, (in the dirt), or at the drags runs tubes. Those that I know have ran them say they would never go back to running them.


I'd ask Jake about the gear. 3.73 is a good gear for the street if you plan on much wighway time. 4.30 will get you out of the hole better though. Depends on what you're actually wanting.

I think you'll like the 150 springs even more.

keep us informed.

Don

[Awesome Bill]

Well I have most of the bugs worked out of my dart 427 sbc build that some of you have helped me with. I'am in FL. so we get to drive em all year round. Car is an outlaw bodied 1934 chevy with their prostreet frame, no cage.

For now, street car only.

Suspension is parallel 4 link with panhard bar, all pretty basic stuff.
Tires are 21.5x33 M/T sportsman (very old and hard)
Car weighs 2600lbs.
Rear coil overs have 275 springs
Front suspension is mustang 2

Problem being, car is quite spooky to drive, gets away from you real quick. I know the car is sprung to stiff, very little shock travel. Doing some checking on tires now, may even drop down a size in width to get the suspension travel needed.

Looking for some basic starting point advice or some recomended reading. (articles or books)

Any thoughts on brand of rear coil overs and spring rate?

Thanks,
Jason

Don, I really don't get to upset with what anyone says, its all just information. What I find wrong with your post and mine that I went back and read it is. This guy don't have a clue. We are all trying to get his flexiflyer cheaper chassis car kit or something to actually work when he has no cage.

There is only so much you can do with something like this before bending and flexing overrides anything you can do. I do not understand your theory on too much bite, NO SUCH thing and that is non sense. The converter or clutch controls bogging. I would rather have a 5500 rpm launch with a dead hook than any "on the edge traction theory" I have never had to much bite.

Bite is the ability for the chassis to keep the sidewall moving the car and weight versus torque forward and tire patch from slipping and loosing traction or being on the edge. There are 2 items you have to address with a chassis and I have never heard that from any one even you on this board or others. People think they know but I find it funny that no one ever address the root, just lets bandaid it and ask a lot of questions about IC and other things that really mean nothing until you watch what is going on.

If it is on the edge, its is always going to kick your ass!!!!!. If you can't get it to hook, you will never get a handle on it. I have tuned the chassis on these hot rods with the ladder bars and 4 links with 1000hp engines had I get them to go dead straight with no cage. An anti roll bar for the back is nice but these cars are usually painted or coated and no one wants to redo that. The sway bars or anti roll bars are a perfect addition to any car and will always make the car respond to more power with less deflection engine and drive train torque steer! You slow mo any hard hitting car and you will see the tire does not spin nor does the car go left or right when they are tuned right.

My Camaro will hold both stages of N2O off the trans brake which is up to 600hp with a ladder bar stock suspension front end tune up. Car has been a best of 7.86 with 3.73 gears and a 10.5W and a 1.15 60. Took me a while to get the bugs out but the chassis was always there. I just had to find it. I never once changed the IC line until I had a complete hold of the tire spin. I did lower the bar after wards and that calmed the wheel standing down a tad and I do not use an "anti roll bar" So with all respect, without seeing what his car is doing, we can only suggest what we know.

[want-a-be]

It's true that a cage will make this chassis work better, and more consistant, at the track. But it is what it is. He has to work with what he has. If he decides to put a cage in the car it will be his decision,...or the track he runs at if he runs too fast...lol

I'm not sure that you could ever really dead hook a set of 10.5" tires with some real racing torque. (not implying that you don't have the power) So I couldn't imagine having this kind of problem on them. I don't run and never have ran the 10.5" tire classes. It's always a ballance of power to traction to get the best times.

But with a set of the wider, taller tires I have seen dead hook be a problem. Power adders do help though. I have been in conversations with some Fuel, Top alky, and ProStock guys who have made this very comment about being up on the tires out of the hole to get the best times. But these guys aren't using a converter, they are all slipping a clutch off the line. The Fuel guys, (Top Fuel and Top Funny car), are slipping their clutches all the way down the track. Well except for the last couple of hunderd feet that is. That all actually changed when Bernstein welded his clutch up in the traps, (due to parts failure), and set a speed record of 320mph from his record of 311mph. That next Monday Dale Armstrong was on the phone with Mike Sullivan to see what it would take to lock his clutch up when they wanted it to. Hence todays amazing speeds in the fuel classes. But thats all racing history that I happened to be a part of. A bit off topic. But it is all fact and too long a story for this thread.

Converters tend to hit the tires harder then the, "pro style clutches", clutch cars do. Mainly because they are slipping the clutches off the line. Don't get me wrong though...they are still leaving the line hard. So for the converter cars it can be hard to tune for the right amount of traction and not have so much that you're bogging the engine. Bogging an engine equates to slower times. Remember though...I'm talking about normally asperated engines. Not those that are running power adders, in ET racing, as you are.

Don

[Awesome Bill]

It's true that a cage will make this chassis work better, and more consistant, at the track. But it is what it is. He has to work with what he has. If he decides to put a cage in the car it will be his decision,...or the track he runs at if he runs too fast...lol

I'm not sure that you could ever really dead hook a set of 10.5" tires with some real racing torque. (not implying that you don't have the power) So I couldn't imagine having this kind of problem on them. I don't run and never have ran the 10.5" tire classes. It's always a ballance of power to traction to get the best times.

But with a set of the wider, taller tires I have seen dead hook be a problem. Power adders do help though. I have been in conversations with some Fuel, Top alky, and ProStock guys who have made this very comment about being up on the tires out of the hole to get the best times. But these guys aren't using a converter, they are all slipping a clutch off the line. The Fuel guys, (Top Fuel and Top Funny car), are slipping their clutches all the way down the track. Well except for the last couple of hunderd feet that is. That all actually changed when Bernstein welded his clutch up in the traps, (due to parts failure), and set a speed record of 320mph from his record of 311mph. That next Monday Dale Armstrong was on the phone with Mike Sullivan to see what it would take to lock his clutch up when they wanted it to. Hence todays amazing speeds in the fuel classes. But thats all racing history that I happened to be a part of. A bit off topic. But it is all fact and too long a story for this thread.

Converters tend to hit the tires harder then the, "pro style clutches", clutch cars do. Mainly because they are slipping the clutches off the line. Don't get me wrong though...they are still leaving the line hard. So for the converter cars it can be hard to tune for the right amount of traction and not have so much that you're bogging the engine. Bogging an engine equates to slower times. Remember though...I'm talking about normally asperated engines. Not those that are running power adders, in ET racing, as you are.

Don

I can kill any engine with a tighter converter, means nothing to dead hook. Kill the engine before its peaks and you will have a smooth take off with a killer top end. Most likely in the shifts it will not recover very well. Dead hook is a killer chassis that will do that, dead hook every time. Don I leave on the wood with a 300 or so shot of N2O as soon as I mat it. Pro tree I leave pretty quick. Now thats a fact and run very close to 8.50 every time. we do pedal if we tree them. If not I run them out the back door and hope the the best. ASK Mobley, he runs a 10.5 tire with a 3000hp blown engine. He does it every time. Hell he wins everything.

[want-a-be]

I always like it when you have the time to post Bill. You do a good job of promoting thought with a no B.S attitude. The proof is in the amount of traffic generated after you done.

Looking forward to your next visit.

Don

[Awesome Bill]

flattery will get you no where, I will bust your butt anyway, just kidding, we are playing with a whole new series of torque converters designed to kill power on the bottom end but be able to lauch with up to 500hp of juice, it is working very well with no 2 step. WE are not blowing the tires off either and not using timing controllers!

[Mattsv8_03]

a parallel 4 link isint supposed to hook in my opinion. no instant center at all. its a good design for a driver or lowered car or truck.

[want-a-be]

a parallel 4 link isint supposed to hook in my opinion. no instant center at all. its a good design for a driver or lowered car or truck.

Yea, the more parallel the upper and lower bars are to each other the more smooth the ride. But it does greatly change how you're going to hit the tires.

Don

[Awesome Bill]

a parallel 4 link isint supposed to hook in my opinion. no instant center at all. its a good design for a driver or lowered car or truck.

It does not care what the bars are for a true street car. But, put those top bars way up there with a dead hook and power and watch the front end come up so fast it will flip over before he can get out of it.

With no roll cage to stiffen up everything, the only way to get it to hook is kill the power with a tight converter keeping the torque curve very slow and smooth to keep it all sutle. Either way, a true cruiser will work with anything. It is obvious he does not drag this thing or wants to.