Make it handle

[hairlesshobo]

OK now that I have decided what steering components I am going to put on the truck, now time to look into suspension upgrades. One annoying problem that I have right now is the front likes to "bounce" for a number of seconds when I hit any bump or apply the brakes quickly. I assume this "bouncing" is actually spring oscillation. On this point, I have a few questions.

1. From what I understand, adding a sway bar (either front or rear) increases the effective spring rate. Or in other words, if I add a sway bar, it will make the truck feel as if the springs are a higher rate than they actually are, right?

2. Assuming that I am correct about #1, will increasing the spring rate make things better or worse in relation to the annoying bouncing.

3. Regardless of the answer to number 2, I assume that investing in high quality shocks would help tremendously with the "bounch" or "repeated dive" in the front end, is this correct? Currently I have sensa-trac shocks on the front and rear that are about a year old. While not the cheapest on the market, by no means the most expensive.

And finally, 4. I've read that cutting a coil off the front spring lowers it AND stiffens the spring. Would cutting a coil off be beneficial. First, the springs have close to 200k miles on them and I assume this makes them very bouncy and wore out. Is it even worth trying to keep the factory springs or do I need to just look into getting new springs as well?

[SCOTI]

Originally Posted by hairlesshobo

OK now that I have decided what steering components I am going to put on the truck, now time to look into suspension upgrades. One annoying problem that I have right now is the front likes to "bounce" for a number of seconds when I hit any bump or apply the brakes quickly. I assume this "bouncing" is actually spring oscillation. On this point, I have a few questions.

1. From what I understand, adding a sway bar (either front or rear) increases the effective spring rate. Or in other words, if I add a sway bar, it will make the truck feel as if the springs are a higher rate than they actually are, right?

2. Assuming that I am correct about #1, will increasing the spring rate make things better or worse in relation to the annoying bouncing.

3. Regardless of the answer to number 2, I assume that investing in high quality shocks would help tremendously with the "bounch" or "repeated dive" in the front end, is this correct? Currently I have sensa-trac shocks on the front and rear that are about a year old. While not the cheapest on the market, by no means the most expensive.

And finally, 4. I've read that cutting a coil off the front spring lowers it AND stiffens the spring. Would cutting a coil off be beneficial. First, the springs have close to 200k miles on them and I assume this makes them very bouncy and wore out. Is it even worth trying to keep the factory springs or do I need to just look into getting new springs as well?

The springs oscillation is controlled by the shock. If you're bouncing more than 1-revolution/cycle, the shocks are not doing their job & need to be replaced.

Cutting a coil does drop the overall ride height as well as slightly increase the spring rate. It doesn't usually increase the spring rate enough to offset the amount of drop so it can bottom out easier if things are already close (some vehicles might have an issue while another type won't). A specific, known spring rate is the best way to go but cutting a coil is common & effective drop just don't expect much change in the spring rate (10-20% increase).

[robnolimit]

1. Yes, sway bars do increase the effective rate, BUT, only in a corner, and only on the outside spring. Not in a straight line.

2. too hard to tell.

3. Listen to Scoti, spring oscilation is usually a sign of weak shocks.

4. Springs are pretty tough, but, 200k miles will take it's toll. Get some new springs first.

[hairlesshobo]

OK, thanks guys. That perfectly answers my questions. So now my plan is to replace my front spindles (1" drop) and new 2" drop springs, add swaybar to front and rear (likely going to be 1 1/4 front and 1 1/8 rear), and lower my rear 4 - 5" using mounts and shackles. And I am going to invest in some quality shocks, both front and rear... sensa-track just isn't cutting it. One of these days I also hope to convert to a trailing arm coil spring setup and lose the leaf springs, but that's going to be a while yet due to lack of money. Oh, and I need to get around to getting my truck weighed so that I can have an idea of what I'm working with when choosing springs.

ps. Post #1,000... woohoo! lol

[SCOTI]

Originally Posted by hairlesshobo

OK, thanks guys. That perfectly answers my questions. So now my plan is to replace my front spindles (1" drop) and new 2" drop springs, add swaybar to front and rear (likely going to be 1 1/4 front and 1 1/8 rear), and lower my rear 4 - 5" using mounts and shackles. And I am going to invest in some quality shocks, both front and rear... sensa-track just isn't cutting it. One of these days I also hope to convert to a trailing arm coil spring setup and lose the leaf springs, but that's going to be a while yet due to lack of money. Oh, and I need to get around to getting my truck weighed so that I can have an idea of what I'm working with when choosing springs.

ps. Post #1,000... woohoo! lol

FYI, I've never heard of a 1" drop spindle. They start @ 2", then 2.5", & 3" increments. A 2" spindle & 1" spring would be an excellent choice if you're targeting a 3" drop up front.

[hairlesshobo]

Originally Posted by SCOTI

FYI, I've never heard of a 1" drop spindle. They start @ 2", then 2.5", & 3" increments. A 2" spindle & 1" spring would be an excellent choice if you're targeting a 3" drop up front.

Thanks for the correction.

[robnolimit]

I have to admit that this project has slipped off of my top pile. I'll make a call today to see where we're at. All prodution samples have been approved, just waiting on a few parts.

[robnolimit]

Lots of questions lately about rear suspensions. 3 and 4 bar, traling arm, .... I'm going to try to sort these out a step at a time. First, realize that there is a LOT going on here. to really compare, think about all that is happening. The basic scenario goes like this. The rear suspension has to locale the axle. Front/rear, side/side, and up/down. Next, it will aply forces from the ground/tire contact patch, to the chassis. Forward, rearward, side/side, bump/jounce. How these forces are applied is important to us. Next, you have to consider pinion angle change, roll steer, IC movement, anti-squate, or rate-of-rise, and lastly, packaging onto the chassis. At this point, we havent even started to think about how to get a good ride. I'm still thinking about how to lay this out for discussion. Give it some thought, what is most important to you?

[oldblue1968chevy]

LOW budget handling, simple stuff for average person, not a 5k handling kit lol

[hairlesshobo]

Since my truck is a daily driver, personally I shoot for about 75% performance and 25% ride quality. The way I see it, if I wanted a daily driver that feels like a Corolla, I'd go buy a corolla. I am willing to sacrifice some comfort for sake of a very fun ride.

[gringoloco]

Originally Posted by oldblue1968chevy

LOW budget handling, simple stuff for average person, not a 5k handling kit lol

Originally Posted by hairlesshobo

Since my truck is a daily driver, personally I shoot for about 75% performance and 25% ride quality. The way I see it, if I wanted a daily driver that feels like a Corolla, I'd go buy a corolla. I am willing to sacrifice some comfort for sake of a very fun ride.

Agreed. I'm cheap. Low buck is king, but only to a point. 50/50 ride/handling- cake AND eating it, too. Too much to ask?
Posted via Mobile Device

[robnolimit]

I think we should really go back to the begining. Lets start out by looking at the basic types of rear suspension available for these trucks.

Leaf Springs These are pretty common, and one of the most used and sometimes under rated. Leafs are widely used because of the manufacturing costs, and vehicle packaging. Leafs do many jobs at one time. They are the locators, front/rear and side/side, and the spring. The 'Instant Center', where the force pushes on the truck, is right at the center oof the front spring mount - non adjustable. The roll center is appx at the same height, and non adjustable. There is some side/side motion due to spring flex. HP threshold is around 400, after that the spring wrap is a big problem. Sway bars, shocks, and bushins can help. Be honest with your build. Once you add traction bars, sway bars, shocks and bushings, you've passed up the cost of link style suspensions.
Leafs can ride great, and handle good. Mary Pozzi won MANY autocross championships with her leaf spring 72 camaro. Keep in mind that the Big three automakers are there to make a profit, and leafs are a low cost, effective way to get the job done.

[jmlcolorado]

Dude, your such a wealth of knowledge, you need to build a website for guys like us to reference.
I'm building a trailing arm 68 with a 1950 international cab and bed. My sister and brother in law both auto cross and would love to get into the sport in an unusual truck.
Ive started (made it about 20 pages in) reading this whole thread, and thought how nice it would be to be able to open a page and look up specific topics. Roll center and Instant center are perfect examples of things I need further understanding and education on to understand d their cause and effect.
Posted via Mobile Device

[robnolimit]

Originally Posted by jmlcolorado

Dude, your such a wealth of knowledge, you need to build a website for guys like us to reference.
I'm building a trailing arm 68 with a 1950 international cab and bed. My sister and brother in law both auto cross and would love to get into the sport in an unusual truck.
Ive started (made it about 20 pages in) reading this whole thread, and thought how nice it would be to be able to open a page and look up specific topics. Roll center and Instant center are perfect examples of things I need further understanding and education on to understand d their cause and effect.
Posted via Mobile Device

Sounds cool, and thanks, BTW, nice place to live.
, Another note on leafs. The WIDTH of a leaf can make a big difference. '54 and earlier chevys, and '47 and back fords use a 1 3/4" wide leaf. Through the 50's it was 2", then 2 1/4", and in the late 60's, 2 1/2". Some newer trucks have 3" or 3 1/2". The wider springs have less side flex, and usually a smoother ride, fewer leafs are required. Changing you leaf set up from 'truck' style, Axle under and shackle going up, to a 'car' style, Axle over, and shackle going up, can really improve the ride, but it drops the load capacity. Many, many people 'flip' the axle, which drops the truck, but almost nobody flips the shackle. Yes, that will lift the truck a bit, appx. 1 1/2", but the ride is way better.

[hairlesshobo]

Originally Posted by robnolimit

Sounds cool, and thanks, BTW, nice place to live.
, Another note on leafs. The WIDTH of a leaf can make a big difference. '54 and earlier chevys, and '47 and back fords use a 1 3/4" wide leaf. Through the 50's it was 2", then 2 1/4", and in the late 60's, 2 1/2". Some newer trucks have 3" or 3 1/2". The wider springs have less side flex, and usually a smoother ride, fewer leafs are required. Changing you leaf set up from 'truck' style, Axle under and shackle going up, to a 'car' style, Axle over, and shackle going up, can really improve the ride, but it drops the load capacity. Many, many people 'flip' the axle, which drops the truck, but almost nobody flips the shackle. Yes, that will lift the truck a bit, appx. 1 1/2", but the ride is way better.

Let's say you wanted to do a drop but didn't want to go as low as a flip kit provides. I assume flipping the axle AND the shackle would be a good way to lower it, but not go quite as low as a flip kit by itself and would provide a better ride. Also, I assume this may help remove the need for a C notch, but that's just a guess since I've never done a flip kit before. Am I completely off on this one?

[robnolimit]

[QUOTE=hairlesshobo;5114016]Let's say you wanted to do a drop but didn't want to go as low as a flip kit provides. I assume flipping the axle AND the shackle would be a good way to lower it, but not go quite as low as a flip kit by itself and would provide a better ride. Also, I assume this may help remove the need for a C notch, but that's just a guess since I've never done a flip kit before. Am I completely off on this one?[/QUOT

Right you are. A flip drops you 6-7" and requires a notch. There is no ride improvement. If you flip the shackle also, the net drop is 4 to 5". This can done without a notch, and gives you a better ride.

[tasian]

Originally Posted by robnolimit

Many, many people 'flip' the axle, which drops the truck, but almost nobody flips the shackle. Yes, that will lift the truck a bit, appx. 1 1/2", but the ride is way better.

this is exactly what i've been planning to do mainly just to lift the rear end back up a little bit is there any way to flip the shackle that is better then another? we did this on my brother in laws 4x4 and i think we just took out the factory rivets flipped the mount over and used the same holes but i wasn't sure if it would be better to move the mount maybe?

also you said the ride is better so i assume that it changes the spring rate somewhat any insight you can share on that? as always thanks for all the great info

[robnolimit]

Originally Posted by tasian

this is exactly what i've been planning to do mainly just to lift the rear end back up a little bit is there any way to flip the shackle that is better then another? we did this on my brother in laws 4x4 and i think we just took out the factory rivets flipped the mount over and used the same holes but i wasn't sure if it would be better to move the mount maybe?

also you said the ride is better so i assume that it changes the spring rate somewhat any insight you can share on that? as always thanks for all the great info

With the shacle running 'UP', truck style, the heavier load, or bump, puts the spring and shackle 'at odds' with each other. The spring wants flatten out, and extend (this would cause the shackle to lean back), but the load if pushing the shackle to be straight up (gravity) This gives a steep Progression in effective spring rates. With the shackle 'down', car style, the leaf and shackle work together. When the spring wants to flatten out and extend, the load, or bump, is also causing the shackle to want to lay back. This gives a more consistant spring rate, and a smoother ride. I usually move the shackle hanger forward 5/8" when I flip the mount, this helps the shackle to be straight up/down at RH

[aggie91]

Originally Posted by robnolimit

Sounds cool, and thanks, BTW, nice place to live.
, Another note on leafs. The WIDTH of a leaf can make a big difference. '54 and earlier chevys, and '47 and back fords use a 1 3/4" wide leaf. Through the 50's it was 2", then 2 1/4", and in the late 60's, 2 1/2". Some newer trucks have 3" or 3 1/2". The wider springs have less side flex, and usually a smoother ride, fewer leafs are required. Changing you leaf set up from 'truck' style, Axle under and shackle going up, to a 'car' style, Axle over, and shackle going up, can really improve the ride, but it drops the load capacity. Many, many people 'flip' the axle, which drops the truck, but almost nobody flips the shackle. Yes, that will lift the truck a bit, appx. 1 1/2", but the ride is way better.

I know this is back tracking a bit, but I did the rear shakle/hanger flip on my son's '82. We are not done and it is not on the ground yet, but my priliminary measurements with how I did the flip put the spring piviot of the shakle at about the same measurement from the floor (actually about 1/8" lower) There are pictures on my son's build thread. We did do a notch on the frame for other reasons and the floor of the bed will be raised 4". That still puts one of the floor cross supports just kissing the hanger...

[no moa]

Originally Posted by robnolimit

I think we should really go back to the begining. Lets start out by looking at the basic types of rear suspension available for these trucks.

Leaf Springs These are pretty common, and one of the most used and sometimes under rated. Leafs are widely used because of the manufacturing costs, and vehicle packaging. Leafs do many jobs at one time. They are the locators, front/rear and side/side, and the spring. The 'Instant Center', where the force pushes on the truck, is right at the center oof the front spring mount - non adjustable. The roll center is appx at the same height, and non adjustable. There is some side/side motion due to spring flex. HP threshold is around 400, after that the spring wrap is a big problem. Sway bars, shocks, and bushins can help. Be honest with your build. Once you add traction bars, sway bars, shocks and bushings, you've passed up the cost of link style suspensions.
Leafs can ride great, and handle good. Mary Pozzi won MANY autocross championships with her leaf spring 72 camaro. Keep in mind that the Big three automakers are there to make a profit, and leafs are a low cost, effective way to get the job done.

Great info on leafs, thank you, i'm running stock HD 5 leaf set up in mine. 454/400 with around 400 hp. But i dont' plan to run it to hard. well maybe in a straight line.

[Matt R]

Awesome thread, i've been keeping up with it for a while now. I picked up the Herb Adams book and have read it a couple times now. Rob, I see you recomended the suspension pro computer program, is there any other programs out there or is that the best one?

I've been doing a good bit of tortional frame bracing and am real close to welding up my No Limit 4 bar kit. I'm gettin real excited, this thread has really done it for me!!!!

[robnolimit]

Looks good Matt R. Keep it up, and kkep us posted.

[robnolimit]

The "Wrap-up" on leafs. Easy to understand, fairly inexpensive. They can have a good ride and handling. Mostly non-adjustable. Expected Hp/Tq limit, 400/400. The lower the front spring eye mount is, the lower the anti-squat is, this could have less traction.

[69gmcc10]

Originally Posted by robnolimit

The "Wrap-up" on leafs. Easy to understand, fairly inexpensive. They can have a good ride and handling. Mostly non-adjustable. Expected Hp/Tq limit, 400/400. The lower the front spring eye mount is, the lower the anti-squat is, this could have less traction.

When you said the lower the front spring eye mount is the lower the anti squat, in what relatino is that? Is that to where the shackle mounts on the frame or the shackle to the leaf? Would longer or shorter shackles make a difference? Is there a correct ratio people should shoot for? how do cal-tracs effect this? Thanks

[hgs_notes]

Originally Posted by 69gmcc10

When you said the lower the front spring eye mount is the lower the anti squat, in what relation is that? Is that to where the shackle mounts on the frame or the shackle to the leaf? Would longer or shorter shackles make a difference? Is there a correct ratio people should shoot for? how do cal-tracs effect this? Thanks

He is talking about the front leaf spring mount which does not have a shackle, which is why there is no adjustment. (unless the mount is modified for upwards or lower mounting of course)

The rear mount has the shackle. Shackle length in the rear will effect ride quality and the longer the shackle the more side to side flex there will be. On a truck a longer shackle will lower the rear, unless the shackle is flipped like the car style, which will then raise the rear. Think 70's car with giant m50's in the back and the gas tank showing because the ass end is sticking up. Longer shackles on jeeps was a common inexpensive way to get soe lift, but the shackle is weaker, so now those kits usually have a bar welded between the shackle plates to strengthen it.


Shackle flip kits for trucks are available through the off road after market as a common lift option. Othere will remove the front spring mount of the rear axle and swap it into the rear mount, so the shackle can point downwards. I have also seen pics of the regular rear spring mount with a hole cut through the bottom for the shackle to go through, but I think this would really reduce the strength of the mount.

Here is a typical shackle flip mount...