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 Post subject: Bumpsteer
PostPosted: Sat Sep 28, 2013 6:58 am 
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Location: Bardstown KY
Done a search and didn't find what I needed so I'll ask here. Running a BJ beam and fixing too add a rack and pinion. Whats the easiest way too measure and eliminate bump steer?


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 Post subject: Re: Bumpsteer
PostPosted: Sat Sep 28, 2013 10:19 am 
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madmike is the best one to answer that question . but you need to give more details of what your doing. what rack are you using.


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 Post subject: Re: Bumpsteer
PostPosted: Sat Sep 28, 2013 12:20 pm 
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Location: Bardstown KY
Picked up a Econo rack yesterday cheap, plan on using IH rod ends on box and heim on spindles. Stock bj front end and spindles also.


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 Post subject: Re: Bumpsteer
PostPosted: Sat Sep 28, 2013 1:01 pm 
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Location: monroe indiana
If it an empi or latest rage rack its a one to one ratio and it will rip the the wheel out of your hands you better have a death grip on the wheel at all times cause its bear to hang on too. Far warning so you don't break a arm or cut your fingers off . To set bump steer you mount your rack rack in the center of beam and put 2 tack weld on rack mount where u can cut off easily . Now at your ride height set the toe so back and fron of tire is the same then raise buggy up and measure .then drop front of buggy as low as u can then measure all 3 measurement should be the same . If not cut tacks on and rotate rack up or down . Keep doin this til all 3 are the same . This is how we do it mabe someone else does it differ.


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 Post subject: Re: Bumpsteer
PostPosted: Sat Sep 28, 2013 2:32 pm 
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I would start by seeing how far the tie rods are from the beam stock and try to get the rack in the same amount from your beam should really close. To check bumpsteer I bolt angle on hubs about 2' long and center at full drop check it across from side to side front and back like you would to do alignment get both the same then place jack stands under your hubs and let your buggy down leting your beam down as you do that keep checking it across. If your hubs turn in on the front move your rack down so if it moves out go up with your rack.

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 Post subject: Re: Bumpsteer
PostPosted: Sat Sep 28, 2013 2:38 pm 
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You can also do check one side at a time by putting jack stands under your beam and a square on the floor and against the hub and jack up that side and watch and see if it moves your square

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 Post subject: Re: Bumpsteer
PostPosted: Sat Sep 28, 2013 4:35 pm 
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Location: Bardstown KY
How do I tell what ratio I have?


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 Post subject: Re: Bumpsteer
PostPosted: Sun Sep 29, 2013 6:47 am 
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I do not believe the ratio will effect your bump-steer. I think that was just a warning of caution. I rode with generic 'Off Road' Rack and they are not kidding about the wheel getting ripped out of your hand.

I actually liked the 1:1 ratio. My buggy steered like a go-cart. I could go from full left to full right with out moving my hands from the wheel.

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 Post subject: Re: Bumpsteer
PostPosted: Sun Sep 29, 2013 7:37 am 
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First thing is you need to know what bump steer is. (its NOT when you hit a bump and the steering wheel gets ripped out of your hands).

Bump steer is the change in wheel geometer (ie. camper, toe) through the suspensions range of motion.

So for example you hit a hump in the road. The front end compresses down and you see the fronts of your tires point outwards. OR in other words your toe goes way positive.

Its not from the Bump you just hit, its cause by your alignment, tierod angles in correlation with the travel of your front arms, tierod lengths.

The best way to setup a new rack is to take out the front springs and then you can easy move the front arms through there range of motion. Then you can measure the changes in you wheel alignment.

If you are hitting holes and bumps an the steering is being ripped out of your hand, you can fix that with 1 or 2 steering dampeners, a larger steering wheel, power steering.

There are man books out there on suspension setup and theory.


**Disclamer** Im not a bump steer expert but I did stay at a holiday in express last night.


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 Post subject: Re: Bumpsteer
PostPosted: Sun Sep 29, 2013 9:42 am 
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Location: monroe indiana
I agree with all of you about the ratio doesn't affect bump steer . I prob didn't make any sence in my post. I aslo was just trying to warn him that it will rip the wheel out of his hands .


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 Post subject: Re: Bumpsteer
PostPosted: Sun Sep 29, 2013 8:37 pm 
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I think someone could get the idea on what Bump Steer is and how to correct it buy the previous posts.
I'm thinking about doing a video on this and and how to set up link pin front ends. Seeing something done is WAY better than being told how to do something. Need to run this through management to get their thoughts on it.

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 Post subject: Re: Bumpsteer
PostPosted: Mon Sep 30, 2013 2:12 pm 
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You really need to measure it either through all the travel or a few points through it, the bumpsteer curve is generally S-shaped, so only 3 spots could show little bumpsteer, when it's actually got a lot between the points.

You'll never get the toe-change to zero on a beam though, there's always some bumpsteer, it's more about minimising it and making what you do have work for you rather than against you.

WRT the steering wheel getting ripped out of your hands, that's more of an issue with the wrong wheel offset or trail.


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 Post subject: Re: Bumpsteer
PostPosted: Mon Sep 30, 2013 2:55 pm 
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PhillipM wrote:
You really need to measure it either through all the travel or a few points through it, the bumpsteer curve is generally S-shaped, so only 3 spots could show little bumpsteer, when it's actually got a lot between the points.

You'll never get the toe-change to zero on a beam though, there's always some bumpsteer, it's more about minimising it and making what you do have work for you rather than against you.

WRT the steering wheel getting ripped out of your hands, that's more of an issue with the wrong wheel offset or trail.


PhillipM, you are correct, zero bump steer is not possible with a beam style suspension. What is most important is what kind of bump steer you have or end up with. Any bump steer that results in a tow out situation is BAD, your car will wonder around and it will beat you up trying to keep it on track. Toe in on the other hand tends to cancel it's self out, right pushes to the left and the left pushes to the right.

As far as getting the steering wheel ripped out of your hand, besides wheel offset, is how far back one leans the top of the beam back towards the rear of the car. The more rake you put in the beam the more you change the king pin angle. The more the king pin leans back the harder it is to steer and the more prone it is to being forced to do what you don't want it to do. What actually happens is when you turn you are lifting one side of the car up slightly.
Adding a steering damper, or two makes the steering harder all the time. That changes a 5 or 6 hour ride into one that feels like a 10 or 12 hour ride.

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 Post subject: Re: Bumpsteer
PostPosted: Tue Oct 01, 2013 9:49 am 
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That's part of the mechanical trail, you can offset it somewhat by pushing the spindle forwards on the upright.


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 Post subject: Re: Bumpsteer
PostPosted: Tue Oct 08, 2013 10:07 pm 
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Location: Bardstown KY
After about 2.5-3hrs I got the bump steer too 3/16" so I called it by good and welded it in. Hopefully it will be all back together tomorrow afternoon. Big shout out too Mad Mike for taking time out of his schedule too call me and help me getting everything set up.


PS....... Putting those tortion springs back together in the front beam is a PITA


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 Post subject: Re: Bumpsteer
PostPosted: Wed Oct 09, 2013 11:49 am 
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OrangeCrush wrote:
PS....... Putting those tortion springs back together in the front beam is a PITA


Should have asked about that. When I ran them I just zip tied them together and beveled the end and they slip right in. Just leave the zip tie on and put it all back together.


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 Post subject: Re: Bumpsteer
PostPosted: Wed Oct 09, 2013 11:55 am 
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And an easy way to set your rack is.

Tack the mount together, bolt it to the rack, get two large hose clamps. Use the hose clamps to hold the rack to the beam then you can cycle your suspension and find the sweet spot by just loosening the clamps and move the rack. Then once you find the spot weld it up.

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 Post subject: Re: Bumpsteer
PostPosted: Wed Oct 09, 2013 2:34 pm 
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OrangeCrush wrote:
After about 2.5-3hrs I got the bump steer too 3/16" so I called it by good and welded it in. Hopefully it will be all back together tomorrow afternoon. Big shout out too Mad Mike for taking time out of his schedule too call me and help me getting everything set up.


PS....... Putting those tortion springs back together in the front beam is a PITA


Glad everything worked out for ya.

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 Post subject: Re: Bumpsteer
PostPosted: Mon Jan 06, 2014 2:57 pm 
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Location: bardstown, ky.
Bumpsteer experts!!!!! Im fighting a bad bumpsteer . Is putting the outer tierod connetion out past the kingpin a no no
I run a very narrow frontend with 2 1/2 longer arms but about 1 inch narrower and I think this makes that worse.ive moved the box alot and still no better.any help is appreciated thanks
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