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help me eliminate understeer

euro-trash97

euro-trash97

Member
Joined
May 8, 2015
Location
Virginia
I have a 91 940 wagon with billy struts, ipd springs, 960 braces, 24mm front and 19mm rear bars, 215/45/17 BFGoodrich Sport Comps 2, camber mod, and kaplhenke quick steer roll correctors (on the quickest setting). The only other things I can even think to put on are a strut tower brace and under chassis brace. I see people talking about taking off the rear bar but I don't think I want to do that because I love how it has no body roll what so ever. Then I was thinking more camber but I don't know how to do that without coils. Please tell me if Im wrong and what I should do. Thank you.

PS if you're on the fence about the roll correctors get them! They totally changed the car for better, worth every penny.
 
I'm nobody's expert on anything, but unless Volvo 900s are different than every other car, removing the rear bar should increase your understeer even more. Doesn't IPD make a bigger rear bar? I just put bars on my 240 and went with the smaller rear bar because I didn't want my wife going around offramps sideways.
 
What are your alignment specs?

In general, to cheaply "eliminate" understeer, you would increase oversteer. To do such a thing simply, you would want to stiffen the rear bar rather than loosen (remove) it. But suspension has limits on either end.

Increasing camber blindly will also not necessarily affect your under/oversteer as it is based on many factors many of which I suspect most people aren't going to change on their 240's.

If you have the stock width springs on the front, lowered or not, corrected or not, your camber adjustments will be quite limited (I recalled it being something laughable like -.8 or something)... but...
 
Also, what understeer are you trying to eliminate? Like... what's your speed range?
 
Yeah, if you want to reduce understeer by removing things, remove the front ARB (don't do that). Installing a stiffer rear ARB should bias the handling more towards oversteer. Remember: increased roll stiffness on one axle increases the relative cornering grip of the opposite axle and vice-versa. If you want the front to grip, stiffen the rear.

Tire pressure also makes a huge difference in how the car handles. Maybe try lowering your front tire pressures slightly and increasing the pressure in the rear. Just a few PSI though, you don't want to start rolling your sidewalls when you're cornering.
 
I don't know how bad the understeer is, but if we're talking catastrophic, borderline undriveable plowing, you might have something else going on. Worn suspension bushings maybe? Something binding during suspension travel? Bald as hell front tires? Totally jacked up toe?
 
225s in front, spare tires in the rear....

Also, what shocks to do you have in the rear? You mentioned your Billy struts up front...which are stiffer than stock. But if you've got the soft stock shock out back....it's going to throw the balance of your car off.
 
did you already do the caster mod? get some control arm stays that are adjustable, or just longer or use rivets to space the controlarm forward. Or shift the topmount backward.
More caster angle will give the wheel more grip in slow tight corners

use no more then about 2.4bar (cold).
If the tires are over inflated the car will ride on the middle section of the thread only. You need rubber touching the ground to generate grip.
 
Last edited:
Fjergus said:
Installing a stiffer rear ARB should bias the handling more towards oversteer. Remember: increased roll stiffness on one axle increases the relative cornering grip of the opposite axle and vice-versa. If you want the front to grip, stiffen the rear.

Tire pressure also makes a huge difference in how the car handles. Maybe try lowering your front tire pressures slightly and increasing the pressure in the rear. Just a few PSI though, you don't want to start rolling your sidewalls when you're cornering.
Click to expand...

+1!

Nothing else in your combo sounds like you're too stiff or likely to cause skating during turn in.

Is this a consistent thing or only when trail / limit braking into an apex on a bumpy road (as an example)?
 
also get your front shocks revalved. how much travel do you have on the piston of the shock? you may be hitting the internal bumpstops in corners
 
To eliminate understeer, you need a stiffer rollback in the rear or softer in the front.
Lower the tire pressure in the front and run higher pressure in the rear.
Lower chassis brace is a must! It's a standard feature on european volvo's.
The upper side of the chassis is already pretty stiff.

I'd follow janspeeds advice about caster mod.
 
Ill start out with less pressure in the front tires, but I do plan on getting a lower chassis brace and ipd sway eventually.
 
What is the toe out on your front end? A little toe out will improve your turn in and can get you on the right path to controllable oversteer. Don't go crazy with it because it reduces your car's ability to track well in a straight line (cruising on the highway). Also, if you travel back/country roads you'll experience more pronounced tramlining. With your 215's it shouldn't be too bad.
 
ellist said:
What is the toe out on your front end? A little toe out will improve your turn in and can get you on the right path to controllable oversteer. Don't go crazy with it because it reduces your car's ability to track well in a straight line (cruising on the highway). Also, if you travel back/country roads you'll experience more pronounced tramlining. With your 215's it shouldn't be too bad.
Click to expand...

It actually has a bit of toe in
 
euro-trash97 said:
It actually has a bit of toe in
Click to expand...

Yeah toe in is pretty standard as it helps the car track straight on the highway and promotes understeer. Manufacturers love understeer.

Go to zero toe (wheels pointed straight) and see how you like it or set up just a little toe out.

Can the rear end alignment of your car be changed? If so, the same holds true but start up front. Make one change at a time.

FYI, it can be tough finding a shop who'll set your alignment outside factory specs. When you get it set, hold onto the printout of the settings.
 
Does your car have ABS?
if not buy the lower ball joints for ABS, this will gain Caster. Get maximum Caster.
Maximum Camber
Harder shocks in the rear, softer in the front
No ride on bumb stops!
Less ARB in front, more in rear
Did you got the Kaplhenke with Ackermann correction? If not do a chat with him
Ls, a real one helps more
less tyre pressure in the front , more in the rear.
No poly in the rear suspension, only the panhard

You can play a lot and get the car you like: Understear or overstear

the lower chassis brace will gain the reaction of the steering, and will do nothing with understear or so.

regards, Kay
 
To much front bar not enough rear bar.I have a 1"rear bar on my V8 wagon it made all the difference in the the way the car handled.
 
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