Suspension and the Savage.

This site may earn a commission from merchant affiliate
links, including eBay, Amazon, and others.

Pope

Well-Known Member
Messages
3,442
Location
Columbus Ohio
There are many things that effect the proformance of your RC but none more than suspension setup. This is a indepth look into the princeables of suspension as applied to the savage. I will skip the aspects that are not changeable on a savage for the sake of time and the fact that there is nothing that can be done about it one way or the other.

First an over view of terms.

1. Suspension travel- The diffrence between the length of a fully extend suspension and a fully compressed suspension.

2. Toe- The angle of of the wheels in relation to straight forward and back.

toe-in-out-1a-1.jpg


3. Camber- the angle of the wheels in relation to a straight vertical line.

camber-gauge.jpg


4. Caster- The angle of tilt forward or back of the line of rotation of the steering axis.

caster-angle.jpg


5. Ride height- the height that a truck sits at rest.

6. Droop- the amount of downward travel a suspension has below ride height.



Now to start lets begin with suspension travel and ride height

This is an often over looked aspect of suspension set up.

It is important to have all aspects of suspension travel set up correctly to have a truck that handles well.

First is your ride height. If you have your truck lifted way up in the air you will create a high center of gravity on your truck causing your truck to become very unstable in turns and at sideways angles. If you have your truck super low to the ground you will limit the amount of suspension compression you have and make your truck very unstable over rough ground.

(The sweet spot for ride height on a savage is right around the point at which the lower arms are level to the ground)

Next is compression beyond ride height. It is important that a trucks suspension be able to compress to absorb rises in the elevation of the ground when running do to washboard sections so that the truck itself does not bounce into the air everytime you hit a bump. The compression is also important when jumping; the compression of the suspension is what absorbs most of the impact of the landing.

(On a savage you want more suspension compression than your truck will alow before bottoming out. This extra compression is used when turning as when turning the roll of the chassis alows for the suspension to compress farther than it would be alowed to do when the truck is compressed equally)

Suspension Droop is another often overlooked aspect of suspension set up. Droop alows the tires to drop down when the elevation drops on do to a pot hole or over washboard sections of tracks. This alows the chassis of the truck to remain level and prevents loss of tracksion do to the truck bouncing. Droop also alows the suspension to decompress beyond ride height when jumping to alow more suspension travel when landing.

( You can limit both compression and droop with spacers placed either inside or outside of the shock body on the shock shafts. Inside will limit Droop, outside will limit compression.)

Another thing effected by these aspects of suspension is how a truck handles under breaking and acceleration.

When Breaking the weight of the truck is transferd to the front of the truck compressing the front shocks and causing the rear shocks to decompress. The amount of droop in the rear suspension determins how much weight can be transfered. The more droop the more weight will be transfered, the less droop the less weight will be transfered. Extra weight on the front tires when breaking will cause your truck to stop faster and pull through the turns under break do to the extra traction on the front wheels. Less weight transfer means less traction and a slower stop along with causing the truck to push trough turns under break.

When accelerating weight is transferd to the rear wheels causing the rear suspension to compress and the front to decompress. This leads to more traction on the rear wheels. The amount of weight transferd again relates to how much droop there is in the front. The more weight transfer the more traction you have under acceleration and the less traction on the front wheels. The more weight transfer the harder a truck will push in turns under power.

(There is a fine line on these setups and most is determinded by driving style. Do you break early and power through turns? Do you break late and power out of them? What line do you like to take? What tires are you using? The list goes on and on and keeping track on set up sheets of what you did and what worked and didn't work for you is going to make you much better in the long run. Being able to get this right is often what seperates first and last place.)


Now lets move on to Toe. Here is a fast break down of it.

Front toe in will increase stability on the straight aways, but it will increase drag causing you to be slower.

Toe out on the front improves cornering ability, but can make your vehicle twitchy on the straights. (adding a little expo will help with this making your imputs around center less sensitive)

Rear toe out is not used on either on or off road r/c's.

Rear toe in on all other vehicles helps to counteract over steer, improve off power steering and increase traction but again adds drag and decresses top speed.

(No more than about two degrees in or out on the front is needed and no more than two degrees on the rear. Note: The Hpi suspension conversions rear tie-rod elimanators have two degrees of toe-in built into them.)

Now for camber.

Camber effects the amount of the tire that contacts the ground either when turning or in a straight line.

Camber is used to counter act the roll of the truck when turning to keep the largest contact patch between the tires and the ground.

Raising or lowering the points at which the Camber links aka top a-arm intersect will effect how camber changes in a turn.

The more of an angle downwards towards the chassis the more on power steering you will have as it causes the camber angle to incresses as the suspension compresses. This also slows the response of your truck to your steering inputs making the truck less twitchy.

(The HPI suspension conversion increeses the downwards angle of the camber link by adding a cross brace that drops down the inside conection point.)

The less of an angle downwards towards the chassis the more off power steering you will have and the faster your truck will respond to steering inputs.

Next is Caster.

For the savage there is only two options for caster and it is only avalible in the front of the truck so I will do this in terms of one verses the other.

The only two settings on a savage are either stock at 0 degrees or the angle avalible with the HPI suspension conversion.

Lets look at what happens with the Suspension conversion.

The added caster slows down steering, increases stability in the corner and improves self-centering of the steering on straights.

It incresses both in and out of corner on power steering alowing you to take turns at a higher rate of speed.

Also when running the Suspension conversion you do not need as much camber because of the change in axis of the outside tire.

(How to tell if you have the corect camber angle: if the outside of your tire is wearing more than the inside you need more camber if the inside is wearing more than the outside of the tire than you need less.)
 
Now for stock hubs.

These hubs give no caster angle and this incresses off power steering, make for a more twitchy truck in the straights do to incressed steering response and no auto centering of the wheels.

Now for the shocks themselves.

When setting up your shocks it is important to rember that the shocks left to right should be the same to prevent dissimaler handling left to right. You can use one of these shock gauges to help

shock-damping-8a-1.jpg


Several things need to be considered when tuning shocks some of which was touched on earlier with ride height, droop, and compression; here are the rest.

The type and size of piston used.
The spring rate of the springs.
The wt. of shock oil used.

Okay so lets look at how each part works with the others.

The type of piston combined with the wt of shock oil used determins how much force is needed to compress or decompress the suspension. The spring rate determins how much force is applied to the shock to decompress it.

All of these have to work perfect together in balance to achieve the best handling truck you can get.

Lets look at piston's first.

The piston is what is put on the top of the shock shaft inside the shock body to restrict the flow of oil from one side to the other creating the dampaning of the shock.

Pistons can be altered in many ways. The number of holes in a piston, The size of the holes, and the taper and direction of that taper.

The larger the hole the less force is needed to compress or decompress the shock because the oil can travel more freely though them. This results in a softer suspension.

Tapered holes is where it gets a little more complacated. A tapered hole piston has a hole that is shaped like a cone not a straight tube. The reason to use a tapered piston is simple. It makes a shock act two diffrent ways; one way when being compressed and another when being decompressed.

If the wider part of the taper is faced up than the shock will compress with less force than it takes to decompress. This alows for a shock that will absorb the bumps in a track quickly than decompress slower to keep the truck from bouncing back.

If the wider part is faced down than the shock will compress with more force than it takes to decompress. This alows for the shock to decompress faster after being compressed to return the truck to ride hight much faster.

Oil Wt

Oil wt is simple the higher the wt. of the oil the more force is needed to push it through the pistons. This makes the suspension stiffer and causes it to react slower the heavier you go.

Spring rate

Spring rate is balanced against what oil and pistons you use to make your truck return to ride hight at the speed you want. The higher the lb rate of a spring the harder it pushes back on the shock to return it to ride height.

The trick to it is to make it so that a truck comes back to ride height as quickly as possible to prepare for the next bump or jump but not to cause the truck to bounce.

Also these will effect how a truck reacts when jumping. When you start up a jump your suspension compresses. You have to find that sweet spot of all three factors to get a truck to handle right and those thing will change depending on the type of track you are on.

(Things to note: You don't want to make you suspension so stiff that your truck soaks up massive amounts of air. That only causes huge amounts of force on the conections between the bulks and the TVP's and also hinders handling. You want your truck to bottom out on larger jumps to help absorb some of that force and also to slow the truck down. Jumps are often quickly followed by turns and the alowing the truck to bottom out when it lands scrubs off speed so you can enter into the turn and power through it instead of having to hit the breaks hard after you land to slow the truck down to enter the turn. This also will keep you from breaking to soon and landing under break and blowing diffs. Also using springs in the front that are softer than what is needed to fully return the truck to ride height artaficaly incresses droop and alows for the front end to be raised back to ride height as you accelerate.)

You can also use preloads on your shocks to adjust ride height within your suspensions travel limits.

Shock angle

I will break this down very fast as the effects will be obvious and a matter of what a driver likes.

More vertical- stiffer feeling suspension as the corolation between wheel travel and shock compression are more directly related
More angle- softer feeling suspension as the corolation between wheel travel and shock compression are less directly related ex: wheel moves 1 inch for every .5" shock compresses.

Adding angle to the shocks will increese the amount of travel possible at the wheels. Decreesing angle will decreese the amount of travel possible at the wheels.

Sway Bars

Sway bars link the two sides of the truck to increese handling. The thickness of the sway bars effect how the truck reacts.

What they do exactly:

As one side of the suspension is compressed it pushes up on the suspension on the other side preventing it from decompressing lowering the center of gravity of the truck as it turns preventing it from rolling over.

without-sway-bar-2a-1.jpg


with-sway-bar-1a-1.jpg


Changing the thickness of the sway bar itself is used to effect how the truck handles.

A softer front bar:
1. Increases front chassis roll.
2. Increases front grip or traction, while decreasing rear grip or traction.
3. Slower steering response.
4. Increases off-power steering at corner entry.


A stiffer front bar:
1. Decreases front chassis roll.
2. Decreases front grip or traction, while increasing rear grip or traction.
3. Faster steering response.
4. Decreases off-power steering at corner entry.


A softer rear bar:
1. Increases rear chassis roll
2. Increases rear grip or traction, while decreasing front grip or traction.
3. Less on-power steering.


A stiffer rear bar:
1. Decreases rear chassis roll.
2. Decreases rear traction, while increasing front grip or traction.
3. Faster steering response in high speed corners and chicanes.
4. Increases on-power steering.

The final thing for a savage suspension is ackermen steering.

Ackermen steering causes the inside tire to turn more than the outside tire. This is used to make both wheels revolve around the same central point creating a much tighter turning truck. The HPI suspension conversion is need to add this to the Savage. There is a small amount of it in the stock set up but not as much as is needed.

ackerman-6b.jpg


ackerman-7b.jpg


ackerman-8a.jpg


Thank you for reading.

Sources:

http://www.rc-truckncar-tuning.com/index.html

www.hpisf.com Members

www.google.com

My own time and research.
 
Last edited by a moderator:
wow nice write up!! i have to admit that clears up alot of questions i've had about toe in and camber so thanks for the effort should help alot of people!!!
 
This sums up everything I have ever read on the subject. It really puts it in a way that is a lot easier to understand with a more direct reference to the Savage.

+rep
 
I finished the write up in post 2. I edited it in.

JR sources are listed at bottom.

If I missed anything you want to know about or think others might let me know.
 
Last edited by a moderator:
rated it
stuck it
repped it.

great write up alex.
 
well at least i know the proper terminology by which you make me drop another $80 on my shocks, lol.
 
awesome Alex.....i knew almost all of it (except shocks) from doind front end alignments and work on real cars. the shock part was very interesting....brought out some points i never thought about. nice dude nice!!.................and you have TOO MUCH TIME ON YOUR HANDS!!! LMAO!!
 
It was going to be in a podcast but it would have made for one that was to long.
 
i just saw this alex. great write up, lots of good info. appreciate the time you took to do it up!
 
WOW Great Job!! I even put in my order for the suspension conversion kit! This should be mandatory reading for anyone wanting to put a Savvy on a track. LOL
 
Love it thanks for your time spent on this!!!
Jay
 
Wow I just joined this site and after reading this write up, pretty much cleared up ever question I had. THANK YOU!!!
 

Latest posts

Members online

Back
Top