bumpsteer on lowered trucks - The 1947 - Present Chevrolet & GMC Truck Message Board Network

jiggs · 09-13-2002, 04:13 AM

For those of you who have spindles and spring lowering kits. When you go over bumps or railway crossings does your truck want to change direction. Do they want to wander on rough roads? Or are they rock solid? It is a concern of mine with lowering my truck.

Project1970 · 09-13-2002, 05:28 AM

Mine is pretty...scratch that...really stable, even at relatively high speed. I've got the Early Classic 2.5" drop spindles on mine. No bump steer to speak of at all.

MOTHERTRUCKERS · 09-13-2002, 07:58 AM

If you use drop spindles and a 1 or 2" drop coil there is no problem with bump steer,any lower than that and it might require a steering stabilizer kit. MOOG kits are around 75.00 from us or just about everywhere they sell MOOG.

XXL · 09-13-2002, 08:44 AM

Quote:

Originally posted by MOTHERTRUCKERS
If you use drop spindles and a 1 or 2" drop coil there is no problem with bump steer,any lower than that and it might require a steering stabilizer kit. MOOG kits are around 75.00 from us or just about everywhere they sell MOOG.

Mine has NO steering stabilizer and NO sway bars and I can stick it in the tightest highway entrance ramps as fast as I can get my inline 6 to go and the only thing that's not rock solid is me trying to hang on to the steering wheel.

Kenneth

**1970 CST Short Wide** · 09-13-2002, 09:58 AM

My truck is lowered 3" in front (springs only) and before I installed the sway bar if you hit a good bump you could change lanes if you were'nt ready for it. The sway bar helped but theres still a bit there. If I were to do it again I would go to Early Classic and get spindles and all

MOTHERTRUCKERS · 09-13-2002, 10:04 AM

XXL how low did you drop it and what did you use spindles or springs?

XXL · 09-13-2002, 02:37 PM

Quote:

Originally posted by MOTHERTRUCKERS
XXL how low did you drop it and what did you use spindles or springs?

Spindles and air in front, air and 2" blocks in rear.

Quote:

Originally posted by 1970 CST Short Wide
My truck is lowered 3" in front (springs only) and before I installed the sway bar if you hit a good bump you could change lanes if you were'nt ready for it. The sway bar helped but theres still a bit there. If I were to do it again I would go to Early Classic and get spindles and all

Spindles do help with suspension travel because you get 2.5" of drop and your control arms aren't already part way through their arc, but it sounds like your problem is with camber and caster. If you've got a strong negative camber ( wheels look like this // \\), then they are both pushing away from the truck as you roll, so when one hits a bump it changes the "balance" of the two pushing in opposite directions, causing it to shoot to one side. Also, if the caster is off too far (think of the vertical axis drawn through upper and lower ball joints-- also sometimes referred to as kingpin inclination) the suspension gets "misaligned" for oncoming bumps (the caster is supposed to be laid back at a slight angle to offset the fact that you'll be rolling forward when you hit a bump). This is something of a simplification of the front suspension geometry, but something to consider.

Kenneth

ChevLoRay · 09-13-2002, 04:42 PM

I also have the ECE 2.5-inch lowering spindles, with stock height springs. I have nothing but praise for their products. My alignment is spot-on with factory specs, and I have NO bump steer, wandering, wheel tramp, or any other steering problem.

I lowered the rear 4-inches, with springs and have the adjustable track bar and shorter shocks. I can pull my utility trailer without it bottoming out, too.

jiggs · 09-13-2002, 08:05 PM

Thanks guys for the responses. I want to also add to my question. For those of you with lowering springs. If you were to look at the suspension from the front, at eye level, is the upper control arm pointing down, up or parallel with the ground. The reason I ask is for camber gain during suspension compression. Thanks for the help!!

MellowYellow70 · 09-13-2002, 08:27 PM

Quote:

Originally posted by jiggs
Thanks guys for the responses. I want to also add to my question. For those of you with lowering springs. If you were to look at the suspension from the front, at eye level, is the upper control arm pointing down, up or parallel with the ground. The reason I ask is for camber gain during suspension compression. Thanks for the help!!

On my '70. I'm using modified lower control arms (about 2.5" drop) and 71 spindles with 1 inch drop coils. The rear uses a 3.5" block, 1 inch drop coils, and a small c channel notch for axle travel. Works fairly well. Only had to realign the front end after doing so 5 years ago.

Dropt72Shortbed · 09-13-2002, 09:08 PM

Quote:

Originally posted by XXL

Mine has NO steering stabilizer and NO sway bars and I can stick it in the tightest highway entrance ramps as fast as I can get my inline 6 to go and the only thing that's not rock solid is me trying to hang on to the steering wheel.

Kenneth

kenneth is right, mines not bagged but ive got drop spindles and hacked coils for a 5-5.5" drop. think is solid to drive, no bumpsteer the ride is smoother than my brand new blazer was stock. only problem with my drop is that i drag my headers the truck is so low.

i can stick the corners as fast as my $25 205/70/15 kirkland signatures will allow me lol

Low67C10 · 09-13-2002, 11:27 PM

I have a set-up similiar to XXL's. No bumpsteer, wander or funny tire wear but has a tendency to understeer which gets real bad(scary) when pushed to the limits. If it wasnt for throttle oversteer I'd have killed myself going down the mountian a long time ago. Its has a bit of body roll but hopefully antisway bars will help that as well as the understeer problem. The best thing to do is to go to a quality alignment shop after its been lowered. When I say quality I mean one that will spend the time to set camber and caster and not just toe. Best alignment specs are most caster as possible within specs, camber as close to zero as possible and toe set to specs. As far as the the camber gain problem goes, as long as some of the drop is gained by cutting the spring or air bags, its gonna occur, the results arent too bad, and theres always the option of buying/building a longer upper A-arm.

jiggs · 09-14-2002, 05:05 AM

So if the front is lowered with springs then when the suspension experiences bump the front suspension goes into negative camber gain. Or is it possitive for an inch and then negative?

The way I look at it is: If the upper a-arm is sitting uphill from the frame at static ride height then under bump the spindle should go into negative camber gain. That is why I want to know if the arm is sitting uphill. If not then a spindle extender or as you say longer upper a-arm with a lower pivot point will be needed. Please correct me if I'm wrong.

So just for my own info; is the upper control arm pointing uphill, downhill or parallel with 1,2,3" lowering springs? I haven't ordered any suspension parts yet because I want to figure this out first.

XXL · 09-14-2002, 08:54 AM

Quote:

Originally posted by Dropt72Shortbed
i can stick the corners as fast as my $25 205/70/15 kirkland signatures will allow me lol

So you've got cheap tires and I have a wimpy motor

. If you ever get some sticky tread or I do an engine swap, the entrance ramps are going to be in big trouble!

Kenneth

09-13-2002, 04:13 AM	#1
jiggs poker face Join Date: Jul 2002 Location: Saskatoon, Saskatchewan Posts: 218	bumpsteer on lowered trucks For those of you who have spindles and spring lowering kits. When you go over bumps or railway crossings does your truck want to change direction. Do they want to wander on rough roads? Or are they rock solid? It is a concern of mine with lowering my truck. __________________ If you could kick the person in the *ss responsible for most of your trouble, you wouldn't sit for a month.

09-13-2002, 05:28 AM	#2
Project1970 14.1 @ 96MPH Join Date: Jul 2001 Location: Mesa, AZ Posts: 2,811	Mine is pretty...scratch that...really stable, even at relatively high speed. I've got the Early Classic 2.5" drop spindles on mine. No bump steer to speak of at all. __________________ Project1970 - LS1 Swap Complete!

09-13-2002, 07:58 AM	#3
MOTHERTRUCKERS Registered User Join Date: Dec 1999 Location: BRADENTON FLA Posts: 3,269	If you use drop spindles and a 1 or 2" drop coil there is no problem with bump steer,any lower than that and it might require a steering stabilizer kit. MOOG kits are around 75.00 from us or just about everywhere they sell MOOG. __________________ Rest in Peace Ed. Thanks for all the good times.

09-13-2002, 09:58 AM	#5
1970 CST Short Wide Senior Moment Join Date: Mar 2002 Location: Pittsburg Ca Posts: 4,111	My truck is lowered 3" in front (springs only) and before I installed the sway bar if you hit a good bump you could change lanes if you were'nt ready for it. The sway bar helped but theres still a bit there. If I were to do it again I would go to Early Classic and get spindles and all __________________ 1970 CST LS 1 6 speed Ford 9 inch Detroit Tru Track, Dakota Didgital, Vintage Air, QA1 Coil Overs Front & Rear Lots of FUN 2013 GMC PU, Oldest Son 71 GMC LWB. QA1 Suspension, Angry SB. Youngest Son 2019 GMC Diesil Dually. Youngest Son 2017 Toyota SUV Daughters car 2018 Traverse , Wife’s Ride Pittsburg Ca 94565

09-13-2002, 10:04 AM	#6
MOTHERTRUCKERS Registered User Join Date: Dec 1999 Location: BRADENTON FLA Posts: 3,269	XXL how low did you drop it and what did you use spindles or springs? __________________ Rest in Peace Ed. Thanks for all the good times.

09-13-2002, 04:42 PM	#8
ChevLoRay Old Skool Club Join Date: Jun 2001 Location: Benton, AR "The Heart of Arkansas" Posts: 10,880	I also have the ECE 2.5-inch lowering spindles, with stock height springs. I have nothing but praise for their products. My alignment is spot-on with factory specs, and I have NO bump steer, wandering, wheel tramp, or any other steering problem. I lowered the rear 4-inches, with springs and have the adjustable track bar and shorter shocks. I can pull my utility trailer without it bottoming out, too. __________________ Member Nr. 2770 '96 GMC Sportside; 4.3/SLT - Daily driven....constantly needs washed. '69 C-10 SWB; 350/TH400 - in limbo The older I get, the better I was.

09-13-2002, 08:05 PM	#9
jiggs poker face Join Date: Jul 2002 Location: Saskatoon, Saskatchewan Posts: 218	control arms Thanks guys for the responses. I want to also add to my question. For those of you with lowering springs. If you were to look at the suspension from the front, at eye level, is the upper control arm pointing down, up or parallel with the ground. The reason I ask is for camber gain during suspension compression. Thanks for the help!! __________________ If you could kick the person in the *ss responsible for most of your trouble, you wouldn't sit for a month.

09-13-2002, 11:27 PM	#12
Low67C10 Registered User Join Date: May 2002 Location: Southern California Posts: 66	I have a set-up similiar to XXL's. No bumpsteer, wander or funny tire wear but has a tendency to understeer which gets real bad(scary) when pushed to the limits. If it wasnt for throttle oversteer I'd have killed myself going down the mountian a long time ago. Its has a bit of body roll but hopefully antisway bars will help that as well as the understeer problem. The best thing to do is to go to a quality alignment shop after its been lowered. When I say quality I mean one that will spend the time to set camber and caster and not just toe. Best alignment specs are most caster as possible within specs, camber as close to zero as possible and toe set to specs. As far as the the camber gain problem goes, as long as some of the drop is gained by cutting the spring or air bags, its gonna occur, the results arent too bad, and theres always the option of buying/building a longer upper A-arm. __________________ No, Its not a 454

09-14-2002, 05:05 AM	#13
jiggs poker face Join Date: Jul 2002 Location: Saskatoon, Saskatchewan Posts: 218	for low67 So if the front is lowered with springs then when the suspension experiences bump the front suspension goes into negative camber gain. Or is it possitive for an inch and then negative? The way I look at it is: If the upper a-arm is sitting uphill from the frame at static ride height then under bump the spindle should go into negative camber gain. That is why I want to know if the arm is sitting uphill. If not then a spindle extender or as you say longer upper a-arm with a lower pivot point will be needed. Please correct me if I'm wrong. So just for my own info; is the upper control arm pointing uphill, downhill or parallel with 1,2,3" lowering springs? I haven't ordered any suspension parts yet because I want to figure this out first. __________________ If you could kick the person in the *ss responsible for most of your trouble, you wouldn't sit for a month.



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