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| | | | Joined: Aug 2004 Posts: 54 'Bolter | | 'Bolter Joined: Aug 2004 Posts: 54 | What the heck is "bumpsteer"? I lowered my '51 truck using the method described by some of you guys. "remove every other spring, starting from the bottom, remove 1-3-5." The only problem I have experienced is when I hit a bump, the steering goes CRAZY, is this BUMPSTEER and what will fix this?
Last edited by Dendo; 07/01/2008 1:07 PM. Reason: spelling
| | | | | Joined: Nov 2005 Posts: 238 Shop Shark | | Shop Shark Joined: Nov 2005 Posts: 238 | Bumpsteer is where the vehicle steers when the suspension moves, sounds like you're experiencing it with your truck.
If you've lowered it a lot and it still has the standard steering setup, you'll need to either shorten the Pitman arm or make a bracket to move the steering box up on the chassis so that the drag link is more or less parallel to the ground when your truck is normally loaded.
If the drag link makes a big angle to the ground, every time you go over a bump the truck will steer one way on bump and the other on rebound. IMHO, moving the steering box up is best; if you shorten the Pitman arm, it increases the amount you'll need to turn the steering wheel to get full lock. Also cutting and welding steering arms has led to some tragic accidents in the past.
The other thing that might be causing or making thee steering worse is that the castor angle may have changed through lowering your truck, would be worth checking as it's easy to adjust.
Stuart.
| | | | | Joined: Aug 2004 Posts: 54 'Bolter | | 'Bolter Joined: Aug 2004 Posts: 54 | How do you chack and correct the castor? the pittman arm is causing the connector ar to run uphill toward the front of the truck. | | | | | Joined: Nov 2005 Posts: 238 Shop Shark | | Shop Shark Joined: Nov 2005 Posts: 238 | Dennis,
Over here we use a Dunlop castor/camber gauge, there must be a similar tool in the US. Too much camber makes the road wheels kick at low speed, too little causes high speed instability.
If you need to correct castor angle, you do it by fitting tapered wedges between the front springs and the axle; the U bolts keep them clamped in place.
The connector (it's called a drag link in the UK) needs to be about parallel to the road if you're not going to get bumpsteer. I think you'll need to fix this to get stable steering even if the castor is out of adjustment too.
Hope this helps, Stuart. | | | | | Joined: Nov 2006 Posts: 60 Wrench Fetcher | | Wrench Fetcher Joined: Nov 2006 Posts: 60 | Dendo. The best way that I have found to determine drag link
angle is; Take a common yardstick and place one end of it
at the center of the bolt that secures the back of the front
spring to the frame bracket. Now place the middle of the
yardstick as close to the middle of the spring pack at a
point directly under the front axle. Then, with an angle-finder,
placed on top of the yardstick, read that angle. You should
try to get the draglink to achive that same angle from the
pitman arm foreward to the steering arm. You might have to
heat the steering arm slightly to achieve the desired angle,
and remember, if you do decide to heat it, let it air cool
naturally. Don"t blow air or water on it to hasten cooling.
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