Steering arm length...

[Krooser]

Building up the Smackdown chassis I bought a bit ago...

Got a pair of S7 spindles. Steering arms are 4 1/2" long. I've heard some chassis use a shorter arm on the left side....not sure really.

Since I have to do a little repair to the left side tie rod bung anyway (it's wallowed out) would there be any advantage to shortening up the left steering arm 1/2". Could also weld two bungs on it and make it adjustable.

Since I've never run this car maybe I should just leave it as is but I have heard some of you guys say you can get a Smack to steer a bit better with a little work.

I plan on a 19" or 20" lower right control arm... 8 1/4- 8 1/2" upper. Any advantage to mounting the left upper a arm inside the frame mounts (tower) like some of the newer GenX cars? I can make a set of those curved uprights if needed... worth the trouble? What length would I use?

I guess whatever i do the left side wheels should track inline, correct? I'll likely use a qc with 33/36 or 34/36 axles depending on what left front set-up I use.

I'll be using a Woodward rack with a remote servo. Will the 3.66 ratio be fast enough? I know 4.0 plus is the hot set-up but I don't have the cash to buy another rack.

One more thing... I'll also be raising the right frame rail as MasterSbilt Racer suggested and will also raise the rack likely with a flat plate mount or by moving the rack plate to the same level as the present front x member.

Now that I can run a bit softer set-up what spring rates do you suggest? Adam Janke (Janke87 on 4M) has a pile of springs for sale and right now I only have 400-450-500-550 for the front as I bought those for my older wide combo car.

Thanks as usual.

[hucktyson]

Most people do run 4.0+ but I’ve noticed a lot of the “ veterans “ also run a 17” wheel maybe run a 15” with the slower rack

[billetbirdcage]

Building up the Smackdown chassis I bought a bit ago...

Got a pair of S7 spindles. Steering arms are 4 1/2" long. I've heard some chassis use a shorter arm on the left side....not sure really.

many cars have slightly different steering arms (L vs R), some are same or really close and others can be a fair amount of difference. Although most modern cars have reduced this to a minimum. But think about what is happening with a shorter LF arm...

Sure it steers more when turning left but what happens when you steer right? it toes in! Ever hit a Ute tire and toed the car in...it pushes like a Mack Truck! Is this really something you want and how much do you actually turn left?

Since I have to do a little repair to the left side tie rod bung anyway (it's wallowed out) would there be any advantage to shortening up the left steering arm 1/2". Could also weld two bungs on it and make it adjustable.

You can but your basically looking at 7/8" minimum change using threaded slugs welded next to each other, so it's a pretty large change. Also if you fixing that stuff, you may need/want to angle the slug to allow enough rod end movement. Also keep in mind that placement of the slug closer or away from the wheel has an effect on the ackerman

Since I've never run this car maybe I should just leave it as is but I have heard some of you guys say you can get a Smack to steer a bit better with a little work.

I plan on a 19" or 20" lower right control arm... 8 1/4- 8 1/2" upper. Any advantage to mounting the left upper a arm inside the frame mounts (tower) like some of the newer GenX cars? I can make a set of those curved uprights if needed... worth the trouble? What length would I use?

I guess whatever i do the left side wheels should track inline, correct? I'll likely use a qc with 33/36 or 34/36 axles depending on what left front set-up I use.

That is a good starting point, IMO

I'll be using a Woodward rack with a remote servo. Will the 3.66 ratio be fast enough? I know 4.0 plus is the hot set-up but I don't have the cash to buy another rack.

With a slower rack, then having shorter steering arms is a plus as far as turning speed, but will/can effect the ackerman by reducing the angle in the tie rods (however there is more to ackerman then just that)

One more thing... I'll also be raising the right frame rail as MasterSbilt Racer suggested and will also raise the rack likely with a flat plate mount or by moving the rack plate to the same level as the present front x member.

Rack hieght plays an important part of bumpsteer assuming you don't have a clevis rack, so get as high as you can but leave room so your not to high to correct bumpsteer. Since I assume your not moving the lower control arm holes the rack should be in the correct place and doesn't need to be moved. However if it has a ton of shims on top of the rack below the tie rod end, then you can move it up and remove some shims. But if everything was correct before it doesn't need to be moved unless you can some for ground clearance

Now that I can run a bit softer set-up what spring rates do you suggest? Adam Janke (Janke87 on 4M) has a pile of springs for sale and right now I only have 400-450-500-550 for the front as I bought those for my older wide combo car.

I know your on a budget, but I don't own any of those springs for a RF, LOL. Having some more springs, just to find what you like or need would be a plus and once you figure that out you can get some good ones or to fill the gaps on what you have.

Thanks as usual.

EDIT: message too short since I did in quotes

[Krooser]

Good points everyone...

The rack I'm using does not have clevis ends but I could change those. I have a 15" and a 17" wheel so I can experiment.

I drove a b mod a couple years ago with a 12" wheel... drove like a go kart.

Sounds like changing the steering arm bungs would be the wrong thing to do. Starting with standard parts and a good baseline will be the right thing to do for me.

[fastford]

you could use a slotted bung so you could adjust the length of the steering arm , we did this several years ago , but we use controlled bump steer instead of akerman to help turn the car now......

[Krooser]

you could use a slotted bung so you could adjust the length of the steering arm , we did this several years ago , but we use controlled bump steer instead of akerman to help turn the car now......

That might work.

Kind of amazing how things have changed in chassis over the years.

The sportsman I built 36 years ago had a Ford stub... I built a zero bumpsteer steering setup for it... rear steer deal. Now rear steer means something entirely different... we did our best to get rid of Ackerman now it's desirable...

[fastford]

i guess you could consider bump steer a form of akerman , but i think traditional akerman ie: different length steering arms and such , is not desirable any more , as in what billet explained above...

[billetbirdcage]

Again back to my point are you turning left, some, slightly or ever?






This is the position the wheels was most left (really most straight) .42 degrees right

[Krooser]

BBB....where did that chart come from...?

[billetbirdcage]

BBB....where did that chart come from...?

Data acquisition. That is just the steering trace over one lap, starting at the flag stand and completing one lap.


*Note: how much steering is going on, is very dependent on the car, driver, track and obviously how the car is handling. So I just picked one, to show that you may not turn left


If you look at the track map, you will see the lines at the start/finish don't line up. That is because he was 3 or 4 feet farther from the wall at the finish of the lap then he was when he started the lap (end of the lap before).

[Ghopper]

Billet, that must be a crate car on a slow track. 0-20deg steering angle range? We should call that person something like Iceman.....

[Matt49]

My guess was going to be a hammer down track. That much back steer the car would have to be pretty sideways or have a TON of rear steer....I would think...interesting discussion. Can we see the wheel spin graph overlaid? :-)

[billetbirdcage]

Billet, that must be a crate car on a slow track. 0-20deg steering angle range? We should call that person something like Iceman.....

Are you saying that driver wasn't up on the wheel enough....(grins) You gonna make it to Knoxville this year?

*Note: how much steering is going on, is very dependent on the car, driver, track and obviously how the car is handling. So I just picked one, to show that you may not turn left As I said it can vary a ton, I picked one that did minimal steering but I could post some on a super that is similar as well as some that go the other direction like -10 to +50.

Ghopper is correct, a crate on medium speed track that was already slow and slick. (60 MPH in center of corner and 90MPH top speed on straight).

The point of my post was I rarely see decent handling cars turn left from zero if zero is set with the car static. Definitely not saying it don't happen but is rare for the cars I mess with but may not be the case for others. What I see is generally the fastest laps are the ones with the least steering range (talking slick stuff).

[billetbirdcage]

My guess was going to be a hammer down track. That much back steer the car would have to be pretty sideways or have a TON of rear steer....I would think...interesting discussion. Can we see the wheel spin graph overlaid? :-)

I'm not sure I trust the yaw rate degree's this unit puts out, but it shows upwards of 35 degrees of yaw in the car sometimes but looking at car it's being driven pretty straight compared to others.

Sorry not gonna post more detailed graphs on the car like wheel spin and travels.