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Forward or Rearward Steering Position

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Poll Question: Do you run your tie rods in front of or behind your front shocks?
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Purduebaja View Drop Down
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    Posted: Sep/26/2011 at 7:09pm

I'll let you in on a little debate our team has been having over the course of the past few years. Running the steering rack in front or behind the shocks and pedal assembly.

For the last 3 years our team has run the Wilwood overhung brake pedal assembly.

Picture: http://www.wilwood.com/Images/PEDALS/pedal_Photos-large/340-5180-lg.jpg

Drawing: http://www.wilwood.com/Images/PEDALS/Pedal_Drawings-Large/340-5180_dwg-lg.jpg

Our steering rack is mounted on a post nearer to the driver. A cover has been fabricated and the rack serves as a heel rest for the drivers feet. However, in our setup this can lead to some weird ergonomics  depending on the driver, and also makes our pedal box dimensions very tall.

What I propose is to use a floor mounted design, either custom made or possibly from tilton engineering, with the steering shaft going between the brake and throttle pedals similar to on Laval's car. I would turn the rack over and mount the tie rods to the front of each upright/spindle. We plan to use a sliding pedal assembly which could be tailored to different size drivers.

I understand that tie rods in the line of fire of rocks, logs, and whatever the crazy track designers come up with is generally a bad idea, but I have seen some clever designs in which the lower A arms are made extra wide to serve as a first defense to anything that may hit the front of the car.

Please feel free to share your experiences with both designs as I would like to know what setup you prefer and why. I need some outside opinions give the rest of my team some insight on which design to choose.

EDIT: Forgot to mention another reason were trying to get away from the wilwood setup is due to several of the fasteners not passing tech. This was due to studs which were held in place with threadlocker, and the main pivot which was a straight pin with a cotter pin to hold it in place.

Thanks,

George


Edited by Purduebaja - Sep/26/2011 at 7:12pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote CLReedy21 Quote  Post ReplyReply Direct Link To This Post Posted: Sep/26/2011 at 10:19pm
Behind.  Your A-Arms can be big enough to protect a tie rod, but they also protect you from having any kind of decent steering angle.  Really the only thing you need  to worry about is trees.

We always bet on hitting a tree at the worst possible moment in the worst possible place so we run rear mounted steering. 

Really you just have to ask yourself, how confident you are that you can either A) Avoid obstacles that eat tie rods.  or B)  Replace bent tie rods in a hurry.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Nick914 Quote  Post ReplyReply Direct Link To This Post Posted: Sep/26/2011 at 10:50pm
You'd have to check if your suspension/direction/chassis geometry allows to put it either at the front or the rear...
If you can put it in rear, it would be wise, but  if it carries interference or requires major modification of something else, well...
We have been running tie-rod at the front for 3 years now and had no issues, but we've been criticized often  for the reasons brought by Chris...

PS: most fasteners no longer require grade 5 at tech
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Post Options Post Options   Thanks (0) Thanks(0)   Quote T_Patn Quote  Post ReplyReply Direct Link To This Post Posted: Sep/26/2011 at 11:04pm
we are changing over to front steer from rear this year due to packaging and dynamic advantages. We had alot of debate about protecting the tie rods and we came to the conclusion that if you have just a little bit of clearance to the front of the a-arms you'll be fine. I think the exact words were "If its good enough for a 1 car or trophy truck its good enough for us"
Tyler Patten
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Post Options Post Options   Thanks (0) Thanks(0)   Quote AndyRIT Quote  Post ReplyReply Direct Link To This Post Posted: Sep/27/2011 at 10:58am
If you hit a tree at speed then you are probably going to bend more stuff then just a tie rod.  Ran both and prefer front because of packaging and fitting in the car. I think we have had one or two bend but kept driving.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote jeiB Quote  Post ReplyReply Direct Link To This Post Posted: Sep/27/2011 at 11:26am
Originally posted by T_Patn T_Patn wrote:

we are changing over to front steer from rear this year due to packaging and dynamic advantages.


What are they?


Edited by jeiB - Sep/27/2011 at 11:27am
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Post Options Post Options   Thanks (0) Thanks(0)   Quote p.lewis Quote  Post ReplyReply Direct Link To This Post Posted: Sep/27/2011 at 2:17pm
Originally posted by Nick914 Nick914 wrote:

We have been running tie-rod at the front for 3 years now and had no issues, but we've been criticized often  for the reasons brought by Chris...
 
Not long ago the safety rule was that forward steering position required a bumper to protect against obstacles. You might get less criticism from judges if you added a bumper. Of course, there's the weight penalty.
 
I think running forward steering is the same risk you take using junk spherical joints in your suspension. You can take the risk, but you have to be prepared to pay for it with DNFs and lost endurance race laps. 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote CLReedy21 Quote  Post ReplyReply Direct Link To This Post Posted: Sep/27/2011 at 3:22pm
Originally posted by AndyRIT AndyRIT wrote:

If you hit a tree at speed then you are probably going to bend more stuff then just a tie rod.  Ran both and prefer front because of packaging and fitting in the car. I think we have had one or two bend but kept driving.


I don't think this is true.  I know we've had several hard tree strikes and only one that I can remember cause any deformation within the suspension system.  However our tie rods are something like .625" x .035" tubing which I am pretty confident would yield pretty easily in bending.  Just sayin. 

I don't really have a strong opinion either way, but the decision that I've come to over and over says rear mount.  And really it depends on what races you're going to.  If you're headed to Auburn or Oregon I'd be way more worried for my tie rods than in say Wisconsin.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote collinskl1 Quote  Post ReplyReply Direct Link To This Post Posted: Sep/27/2011 at 4:20pm
I'm a proponent of rear locations too.  As many have mentioned, the inherent protection is nice.  And like Chris just said, I've smacked many a tree/rock/small child/whatever and have yet to do any damage to the a-arms or other components.  When the weak link in the suspension/steering design is the driver's wrist I'm happy with the robustness of my system. 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote CLReedy21 Quote  Post ReplyReply Direct Link To This Post Posted: Sep/27/2011 at 4:47pm
Just so everybody knows, I'd like to run a front steer position as it makes packaging in the controls are way more better, but I don't kid myself and I'm well aware of TTU's reputation of driving our cars like we stole them haha.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote T_Patn Quote  Post ReplyReply Direct Link To This Post Posted: Sep/27/2011 at 10:57pm
Originally posted by jeiB jeiB wrote:

Originally posted by T_Patn T_Patn wrote:

we are changing over to front steer from rear this year due to packaging and dynamic advantages.


What are they?
It just worked better for our steering geometry this year.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote AndyRIT Quote  Post ReplyReply Direct Link To This Post Posted: Sep/28/2011 at 12:22am
Originally posted by CLReedy21 CLReedy21 wrote:

Originally posted by AndyRIT AndyRIT wrote:

If you hit a tree at speed then you are probably going to bend more stuff then just a tie rod.  Ran both and prefer front because of packaging and fitting in the car. I think we have had one or two bend but kept driving.


I don't think this is true.  I know we've had several hard tree strikes and only one that I can remember cause any deformation within the suspension system.  However our tie rods are something like .625" x .035" tubing which I am pretty confident would yield pretty easily in bending.  Just sayin. 
 
Check the wrecked baja car thread ;)
 
I always liked front position because of the foot room that you gain from it. We had one rear position car that limited who could drive because of the steering box location.
 
I guess it depends on you A-arm geometery, also. I was never worried about running front because our tie-rod was still behind the legs of the A-arm. There was only so much exposed driving straight. At full lock there is no way a tree should be on the inside of the wheel on the inside of a turn.
 
I only remember bending 1 tierod in all of the front position cars since 04' and that was because of freshman driver.


Edited by AndyRIT - Sep/28/2011 at 12:24am
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Post Options Post Options   Thanks (0) Thanks(0)   Quote ErikHardy Quote  Post ReplyReply Direct Link To This Post Posted: Sep/28/2011 at 12:33am
Originally posted by AndyRIT AndyRIT wrote:

 
I always liked front position because of the foot room that you gain from it. We had one rear position car that limited who could drive because of the steering box location.
 
There is always the option of mounting the Rack, master cylinders and Pedals below the feet and running a false floor, enabling a rear rack position while having the pedals at the very front of the car.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote AndyRIT Quote  Post ReplyReply Direct Link To This Post Posted: Sep/28/2011 at 1:11am

Ergonomics! Normally you don't want your feet above your waist because of circulation and driver comfort.

Granted a couple of inches probably will not make that much of a difference but the thought is there in design judging.
 
 
Edit: anyhow it really doesn't matter to me anymore, just sharing my opinion and experience Wink


Edited by AndyRIT - Sep/28/2011 at 1:12am
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Post Options Post Options   Thanks (0) Thanks(0)   Quote johnfar109 Quote  Post ReplyReply Direct Link To This Post Posted: Sep/28/2011 at 7:19am
there is clipping a tree (just lightly touching it)and there is hitting a tree Impacting it a WOT. i have done both. in the first case most of the time the steering arm would give before the tie rod. in the later case i didn't matter all of the corner was coming off. like Andy said if you do up your a-arms right you can protect most of the tie rod. Also the old bumper rule was a joke int "Protecting" the suspension or searing components. just my .02
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Post Options Post Options   Thanks (0) Thanks(0)   Quote CLReedy21 Quote  Post ReplyReply Direct Link To This Post Posted: Sep/28/2011 at 9:49am
Originally posted by AndyRIT AndyRIT wrote:

Check the wrecked baja car thread ;)
 
I always liked front position because of the foot room that you gain from it. We had one rear position car that limited who could drive because of the steering box location.
 
I guess it depends on you A-arm geometery, also. I was never worried about running front because our tie-rod was still behind the legs of the A-arm. There was only so much exposed driving straight. At full lock there is no way a tree should be on the inside of the wheel on the inside of a turn.
 
I only remember bending 1 tierod in all of the front position cars since 04' and that was because of freshman driver.

Yeah yeah :)  I'm just saying that from my experience you can head on a tree at 30 and snap an .035 cross tube but when you catch a heat treated .065 A-Arm at 30 you get a bent A-Arm and in both cases you get a sore neck and a good yelling at.

So based on that information I will present the theory that under similar conditions hitting a tree will completely fail a 1x.035" tube but only bend a heat treated 1x.065".  This would suggest a threshold of carnage above that of tie rod but below that of a (TTU) A-Arm.

Once more, with feeling; I'm totally for a front mount position and I'm well aware of how remote the probability of smashing a tie rod bad enough to  cause a problem is.  I've weighed the risks versus the gains and we were able to come up with a workable solution that might not be optimal, but it works pretty well and keeps the tie rods for sure protected.
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