Effect of IC/AS changes fore handling?

[daveyboy]

So I am doing some IC changes to better my Drag strip times. I was kind of curious what effects It has to the handling of the car. This is more of a multi purpose car as I am doing some auto crossing this year and possibly a Driving school at the end of the year.

 

[csamsh]

It can make braking pretty crazily awful if you go too far. I had around 100% AS in a setup once...awesome coming off a turn, but go anywhere near the brakes and hop hop hop goes the axle.

 

[daveyboy]

so what should I adjust to for handling?

 

[csamsh]

so what should I adjust to for handling?

Sorry about this answer...but....whatever works for you your car, tires, shocks, surface, driving style, and event type. It's the good old, "eveything affects everything else." BUT, I would think "less" would be a good direction to start.

 

[Whiskey11]

I would start with the LCA's horizontal or slightly lower at the axle end and go from there. On my car that happened to be the top hole and this corresponds to about 65% anti-squat. Car has great power down and isn't difficult to drive. I didn't mess with it since the next to spots put me into some serious %AS values (85% and 100%) that I think are too much for a torque arm suspension.

 

[CPRsm]

It can make braking pretty crazily awful if you go too far. I had around 100% AS in a setup once...awesome coming off a turn, but go anywhere near the brakes and hop hop hop goes the axle.

That sounds more like a cause of a short IC length, not really a 100% antisquat

 

[daveyboy]

I would start with the LCA's horizontal or slightly lower at the axle end and go from there. On my car that happened to be the top hole and this corresponds to about 65% anti-squat. Car has great power down and isn't difficult to drive. I didn't mess with it since the next to spots put me into some serious %AS values (85% and 100%) that I think are too much for a torque arm suspension.

I have the whiteline LCA relocation brackets so I have on adjustment. I have to remeasure everything but it puts me over 100%. Not Ideal, I was going for right around 100% due to some issues at my last drag event.

Sorry about this answer...but....whatever works for you your car, tires, shocks, surface, driving style, and event type. It's the good old, "eveything affects everything else." BUT, I would think "less" would be a good direction to start.

I totally hear you on the "what works for the car". I just needed to be reminded again LOL. I think I am going to keep my adjustments that I made for the next autocross and drag race Just to see what goes on. Gotta test sometimes right? If it is two terrible I can put it back. Thanks for the help... I just need two cars I think....sigh

 

[csamsh]

I just need two cars I think....sigh

There we go. The real answer lol

 

[Norm Peterson]

That sounds more like a cause of a short IC length, not really a 100% antisquat

I'm not entirely sure about that.

100% AS doesn't want to let the axle "drop" during deceleration because all of the forward load transfer off the rear axle is going through the suspension geometrically. I think you need to have some (damped) suspension compliance to keep the braking forces from varying wildly as you encounter pavement unevenness and variations in tire loading/deflection.


There is also the matter of axle roll steer varying when you're moving the SVIC around via adjustments in LCA inclination. It isn't hard at all to drive this little piece of the understeer budget into it becoming an oversteer effect at the end of the car that your steering cannot directly manage.


Norm

 

[Sky Render]

The antisquat percentage doesn't affect cornering per se, but the lower control arm angle does affect roll steer.

 

[Whiskey11]

I have the whiteline LCA relocation brackets so I have on adjustment. I have to remeasure everything but it puts me over 100%. Not Ideal, I was going for right around 100% due to some issues at my last drag event.

I really don't understand why people buy the Whiteline brackets when the BMR units are superior in every way. To each their own though. If it were me I'd ditch the WL units for BMR's and enjoy the additional tweaking.

Otherwise, mess with the UCA mounting point if you can do that. I'm assuming you can to get the %AS you are at.

As for %AS and cornering, well, it may not change grip levels in steady state, but it definitely makes a difference coming off the corner. Torque Arm helped a lot there too though.

 

[daveyboy]

I really don't understand why people buy the Whiteline brackets when the BMR units are superior in every way. To each their own though. If it were me I'd ditch the WL units for BMR's and enjoy the additional tweaking.

Otherwise, mess with the UCA mounting point if you can do that. I'm assuming you can to get the %AS you are at.

As for %AS and cornering, well, it may not change grip levels in steady state, but it definitely makes a difference coming off the corner. Torque Arm helped a lot there too though.

The white lines were free which is why i got them. I now know why they were so cheap. Plan on the BMR units soon...gotta stop spending money on nitrous parts first lol. As for the UCA adustment, I have is adjusted for the most AS for my car.(bottom hole)

 

[Sky Render]

I've run both the Whiteline brackets and the BMRs. The BMR units are superior in every way. And they come in red, which everyone knows is a faster color.

FYI, the Whiteline bracket is roughly the equivalent of the center hole on the BMR units.

 

[oldVOR]

The white lines were free which is why i got them. I now know why they were so cheap. Plan on the BMR units soon...gotta stop spending money on nitrous parts first lol. As for the UCA adustment, I have is adjusted for the most AS for my car.(bottom hole)

When you're ready, I've got the things which you seek.
I'd list them but haven't reached the point of membership to post in the classified's. Biding my time until then.
MOD's, if this crosses the line, please delete.

 

[daveyboy]

And they come in red, which everyone knows is a faster color.

True story

FYI, the Whiteline bracket is roughly the equivalent of the center hole on the BMR units.

The Relocation brackets I have measure 3" lower then stock

 

[Norm Peterson]

The antisquat percentage doesn't affect cornering per se, but the lower control arm angle does affect roll steer.

Yes, basically an indirect consequence rather than a direct intentional effect.


Norm

 

[daveyboy]

The antisquat percentage doesn't affect cornering per se, but the lower control arm angle does affect roll steer.

Can you exsplain this a little more for me. Im not sure what it means.

 

[Sky Render]

Can you exsplain this a little more for me. Im not sure what it means.

Read the link in that post.

Sent from my Samsung Galaxy Note 4 using Tapatalk

 

[daveyboy]

Read the link in that post.

Sent from my Samsung Galaxy Note 4 using Tapatalk

Wow, Im an idiot I totally missed that link.


Great article, If i understand that correctly to much of a LCA angle one way "can" cause understeer and a good angle the other way can actually help turn the car

 

[Norm Peterson]

Maybe this is a little picky, but what LCA inclination does is provide half of the definition of axle roll steer (in the S197 the PHB's midpoint or a Watts link's main pivot provides the other half). It's from there that you get a contribution to handling balance in either the vehicle understeer or vehicle oversteer direction. This contribution gets added to handling balance contributions from camber, bushing compliances, Ackermann, and several other effects to arrive at the vehicle's overall handling balance. Some of these effects will be US in nature, others OS, so handling balance is a "net result" kind of thing. Incidentally, there's a reason I'm specifically defining US and OS in the "vehicle" sense.

Strictly speaking, defining the axle's own "roll axis" is a 3-dimensional geometric construction. But showing axle steer as a consequence of LCA inclination and ignoring the rest does get the main point across - that the axle does steer ("passively") as the car rolls in a turn even though the steering wheel isn't connected to it.

Be careful about making judgments about whether axle steer in either the vehicle US or vehicle OS directions is a good or bad thing. It's perhaps situation-specific - you might want a heavier US contribution when you're heavily loaded (to help keep the tail from ever even starting to run wide), possibly mildly OS-ish at autocross so it'll help you turn, and most likely just enough US-ish at HPDE out on the big track so you're not chasing looseness in every corner.


Incidentally, a neutral contribution - neither US nor OS - is perhaps possible instantaneously as brief unique occurrences. But it'll go into US or OS again as soon as the suspension continues to move.


Norm