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Hot Rod Forum : Hotrodders Bulletin Board > Tech Help> Suspension - Brakes - Steering> "soft" front end
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Topic Review (Newest First)
12-19-2007 02:43 PM
oldguy829
re: "soft" front end

Update: took the car to the alignment shop and had them check it from stem to stern. Also had the foreman drive it. He put it thru some paces, and disagreed with my assesment. He felt springs/shocks/sway bar etc. were all fine as it returned to center and responded as it should. He classified it as "over responsive", not soft. He's right, thats the proper description.
Here is where it got interesting. He says more caster will help high speed stability, but too much caster can cause my over responsive symptoms. so we reduced the caster to 1 1/2 - 1 3/4. We can increase the toe, and maybe try to adjust bump steer, etc. but he wants to do one thing at a time, so for now, just the reduced caster. Going to drive it over the holidays and decide if it's better/worse/ or the same. [ the drive home was in heavy traffic, so I'm reserving judgement till I drive it under many conditions, but seemed to feel better]
12-18-2007 03:42 PM
joe k When I built my model A,I used M/T bias ply tires. For three years I drove it with a front end that felt light at highway speeds. I thought that maybe at high speeds air was getting under the front fenders and lifting the front enough to make the car light in front. Some times it was even a white knuckle ride until I slowed down. To make a long story short I put on radial tires and got a new car ride.
12-18-2007 10:22 AM
OneMoreTime On the cars I have had the soft floaty feeling was solved by going to a more aggressive shock..The stock shocks were picked to get a very soft ride..the other guys are right on as far as things to look at in alignment..

Sam
12-18-2007 08:24 AM
427v8 Static toe and dynamic ( roll or bump steer) cause completely different issues.
Static Toe in, at ride height, makes the car drive in a nice straight line, too much will wear the tires. Toe out will make the car like to turn, great for roadracing, not so good for street driving.

Dynamic toe changes, come in two flavors which are manifestation of the same thing.
In most suspension systems bump steer and roll steer are caused by the same suspension adjustments and cannot be adjusted seperately ( unfortuneately)

Bump steer you are driving aloog and one wheel hits a bump ( or a hole), the wheel should sty pointing where it was before, it shouldn't turn as it goes over the bump. Any turning, toe in or out, will make the car feel unstable.

Roll steer is what happens when you go around a corner, the car rolls and puts more weight on the outside wheels.
More weight causes compression of the suspension just like going over a bump.
Again, if the wheel turns, the driver will have to compensate.

But it's more complicated than that...
If the car toes in on roll, the car will turn sharper, causing more roll, causing more turn...the driver will compensate by straightening the wheel, which causes less roll, less toe in, less steering...So the driver will turn sharper, back to square 1 !
This is oversteer, and is unnerving to the driver.

If the car toes out on roll, the car won't turn as much as the driver expects, so they will turn a little more. end of story.
This is understeer, and a little makes the car feel stable and predictable, a lot makes the car feel like a Ford, sluggish and unresponsive.

BTW roll steer is what makes a car want to turn into the ditch on a crowned road, it because the car is leaning just like going around a corner.
12-17-2007 05:49 PM
oldguy829
re: "soft" front end

Thanks for the input guys.
Couple of things; everything is new in the front end. Nothing binding, sticking or bent. Tires, 215/70 15's so that may be some of it.
Toe in is just 1/16, so I can up that a little.
427V8, you threw me there. I know (or think I know) that toe out will make em squirrelly. So I designed it to toe in (if anything) on bump steer.
Splain to me why I want toe OUT on bump steer?

Generally, you all are confirming my gut hunch. It's in the alignment. The shop that did it has been around about 50 years and has those "old guys" that know their stuff. They would have put another 1/2* or so of caster on it if they could, but thought it would be fine with what I had.
Guess it won't hurt to have them recheck it.


Any other idea?
12-17-2007 05:17 PM
427v8 Toe is important.
Wht is your toe at ride height? It should be about 1/8" in. toe out will make it squirrely

Bumpsteer is also very important. You need toe OUT on bump, toe in will make the car squirrly and like to wander

Wide Tires can cause tramlining, where the tires try to follow the ruts in the road. i have 255 50 R17's on my vette that tramline like crazy. No cure for that except for fixing the road.
12-17-2007 05:08 PM
AntnyL
Quote:
Originally Posted by oldguy829
My car doesn't ride like I want it to, but I can't put my finger on it. "floaty" maybe? Everything is new, and tight, but it doesn't "track" like I want at high speed. It is like it comes off the center line very easily. Undulations in the road, cross winds, etc. Honestly feels like the front end is light, like when you overload your trunk.
Without changing the stance to add more weight up front, any other ideas?
Here is what I am considering; (any help in identifying, or eliminating, a culprit would be appreciated.)
1. spring rate/shocks - The ride is smooth and it responds to a "bounce" test like it should. Still considering stiffer springs or heavy duty shocks.
2. Bump Steer - I don't think this is it. I believe my toe changes less than 1/4 inch through the entire suspension travel, and it changes to toe in, not out.
But I will double check this as it sounds like a possible culprit.
3. Caster too low. I'm at 2 1/2 - 2 3/4 positive. I'm out of adjustment and changing this is major PITA, so last resort.
4. Drop Spindles - anyone get squirelly results from a drop spindle change?
5. Rack too sensitive - I have modified the flow rate and pressure to match the original Cavalier set up. Could the weight and non strut character of my front end dictate a flow and pressure less than the original cavaleir setup?

Understand, the sensation is subtle. Drives good, but I wouldn't take my hand off the wheel and let it drive itself, which is what i want.
An old timer alignment guy that I used to work next to (his alignment shop was adjacent to garage) used to tell customers that by toe'ing the wheels in a tad from spec, this would cure what you're explaining; would help the car track straight. I've never tried it, but he swore by it, and so did his customers. It's worth a try.

After he'd close up shop, he'd stroll into our place for a nightcap and tell war stories from his younger years. Man, I miss that guy and his stories.

Antny
12-17-2007 03:01 PM
F&J I'd say caster also, "if" it still feels like it won't stay arrow straight on a perfect straight & flat highway. Of course, I'd recheck the toe as accurately as possible, first,....in case it somehow got slightly toe'd out. If it is really out instead of in, it will act spooky like that.

longshot: A frozen or stiff steering part like a kingpin can cause that.
12-17-2007 02:13 PM
Deuce NUMBER # 3 ...

You need more caster ...
12-17-2007 10:25 AM
oldguy829
"soft" front end

My car doesn't ride like I want it to, but I can't put my finger on it. "floaty" maybe? Everything is new, and tight, but it doesn't "track" like I want at high speed. It is like it comes off the center line very easily. Undulations in the road, cross winds, etc. Honestly feels like the front end is light, like when you overload your trunk.
Without changing the stance to add more weight up front, any other ideas?
Here is what I am considering; (any help in identifying, or eliminating, a culprit would be appreciated.)
1. spring rate/shocks - The ride is smooth and it responds to a "bounce" test like it should. Still considering stiffer springs or heavy duty shocks.
2. Bump Steer - I don't think this is it. I believe my toe changes less than 1/4 inch through the entire suspension travel, and it changes to toe in, not out.
But I will double check this as it sounds like a possible culprit.
3. Caster too low. I'm at 2 1/2 - 2 3/4 positive. I'm out of adjustment and changing this is major PITA, so last resort.
4. Drop Spindles - anyone get squirelly results from a drop spindle change?
5. Rack too sensitive - I have modified the flow rate and pressure to match the original Cavalier set up. Could the weight and non strut character of my front end dictate a flow and pressure less than the original cavaleir setup?

Understand, the sensation is subtle. Drives good, but I wouldn't take my hand off the wheel and let it drive itself, which is what i want.

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