soft RF spring helping or hurting?

[Dirtmod13]

We have played with a soft rf spring and it seems like we are losing LR drive with it in the slick. Just re-read an article from Mark Bush saying people put in a soft rf and while it looks like its planting the rf harder it actually doesnt,and does not help with drive. Yet all the cars builders say to go softer in the slick. Rocket says 375 then 350/325 in the slick.

[MasterSbilt_Racer]

There is more to a fast lap than drive. If you simply bolt on a softer rf spring, you will lose dynamic wedge. That is correct.

That change could be positive if you have too much LR drive before the change. Properly loaded rear tires, that share the load, is how you go forward

[25drtrkr]

Mr. Bush has repeatedly stated, also, to take some of the rebound out of the rf shock.

[MasterSbilt_Racer]

Mr. Bush has repeatedly stated, also, to take some of the rebound out of the rf shock.

And, Mr Bush may or may not be correct depending on your dynamic wheel rate behavior.

[Dirtmod13]

So if the soft rf takes away traction then why do the builders say to run softer?

[Dirtmod13]

As the summer has made our track more dry, our soft rf has slowed us down

[MasterSbilt_Racer]

So if the soft rf takes away traction then why do the builders say to run softer?

It doesn't remove traction. It goes to other tires.

[25drtrkr]

If the CoG stays the same, the weight removed from the rf will transfer to the rr, generally making the car tighter on entry.

[rakracing]

mastersbilt is correct, also agree with 25dtr, whats it doing in and in the middle, bad there and off sucks to, I like enough rf spring to not bottom out the frame and soften or stiffen the lf to help in then play with rebound in rf for off. mark calls it a imbalance of traction

[billetbirdcage]

It's rare in the slick that the person with the most drive off the corner wins, least if your not racing locally, on some paperclip stop and go racetrack, or a one lane track.

Drive off the corner is the last thing I generally ever worry about, momentum in and thru the corner generally always takes care of drive off the corner.

If you are constantly complaining about drive off the corner, you might need to reevaluate your racing program, IMO.

[Dirtmod13]

Our real issue is lr drive. Seems like the soft rf ( which as suggested by the chassis builder during setup) is the reason we can't get any lr traction. Car is loose as hell. Can go through corner but only quarter/ half throttle. Off ain't so bad.

[Kromulous]

If your going to run the soft RF spring, wouldnt that in turn make the RR spring that much more critical on corner exit, all the way thru actually?

[swartzman]

refer back to post #10.. and yes the rr spring has a lot to do with what people are running in the right front.. you can bet there was a lot of trial and error getting their cars back to running fast again with the soft right front..

[swingarm4life]

Tire rule?

[Dirtmod13]

Hard tires

[3wheelinphotos]

How about are you doing anything in the rear to make more traction or just changing the RF spring?

[Dirtmod13]

Giving lr more drop and less rear steer to tighten mid and exit. Just doesn't seem to be enough. Can't run stacked or bumps

[HuckleberryB4]

More Drop = More rear steer = Loose
Less Drop = Less rear steer = Tighter

[hsdiefusion16]

What is the rule for bumpstops and stacked springs?

[7uptruckracer]

Those are two completely different animals

[hsdiefusion16]

Yes they are, I work for a spring company so that's why I asked.

[Matt49]

More Drop = More rear steer = Loose
Less Drop = Less rear steer = Tighter

But you could also say:
More drop = more thrust angle and cage indexing = tighter exit
Less drop = less thrust angle and cage indexing = looser exit

[HuckleberryB4]

Agreed. I almost went back and edited with those other possible affects. I "personally" feel that the LR bar adjustment or LR drop has more to do with the change in roll steer, than the change in indexing/thrust angle.

[billetbirdcage]

But you could also say:
More drop = more thrust angle and cage indexing = tighter exit
Less drop = less thrust angle and cage indexing = looser exit


This is another pet peeve of mine.

There's too many things to drop amount to throw out really simple guidelines on what it does, like Matt's post and the one he quoted.

Hike on LR does 2 basic things adds wedge and adds rollsteer, both of these are contradicting each other in whether they tighten or loosen a car. Obviously when hike first starts it adds very little steer for the amount of wedge it adds thus a tightening effect because the wedge tightens more then the small amount of rollsteer loosens the car. As the hike gets farther on it's travel it comes to a point where the steer increase becomes large enough compared the the amount of lift/wedge is added thus gets to a break-over point (just a term I use, not talking over-centering the cage) where going farther will only loosen the racecar.

Pretty straight forward so far, but here is part of my pet-peeve. Many will go off that 45 degree's someone started (probably Mark Bush), while it's good basic general guideline to help the uninformed it had huge flaw's in it. Like it doesn't take into consideration of bar lengths, the lower bar angle being used, or the bars location on the birdcage.

My point is you can have the breakover point happen before or way after the top bar is at 45 degree's, depending on the arrangement of the rear suspension.

Not picking on the guys posts, just voicing an opinion on something and Matt's posts eludes to not lumping into a easy generalization of it.

[Matt49]

I'll add two more points and then I'll go back to doing something else.
1) Adding hike also increases the vertical center of gravity which increases front to back weight transfer on corner exit.
2) More rear steer theoretically makes the car looser because it helps "turn" the car. But this isn't necessarily a bad thing slick conditions, contrary to popular belief.

[25drtrkr]

This is another pet peeve of mine.

There's too many things to drop amount to throw out really simple guidelines on what it does, like Matt's post and the one he quoted.

Hike on LR does 2 basic things adds wedge and adds rollsteer, both of these are contradicting each other in whether they tighten or loosen a car. Obviously when hike first starts it adds very little steer for the amount of wedge it adds thus a tightening effect because the wedge tightens more then the small amount of rollsteer loosens the car. As the hike gets farther on it's travel it comes to a point where the steer increase becomes large enough compared the the amount of lift/wedge is added thus gets to a break-over point (just a term I use, not talking over-centering the cage) where going farther will only loosen the racecar.

Pretty straight forward so far, but here is part of my pet-peeve. Many will go off that 45 degree's someone started (probably Mark Bush), while it's good basic general guideline to help the uninformed it had huge flaw's in it. Like it doesn't take into consideration of bar lengths, the lower bar angle being used, or the bars location on the birdcage.

My point is you can have the breakover point happen before or way after the top bar is at 45 degree's, depending on the arrangement of the rear suspension.

Not picking on the guys posts, just voicing an opinion on something and Matt's posts eludes to not lumping into a easy generalization of it.

Billet, in a recent DLM mag tech article, Mr. Bush stated that indexing generally overrides roll-steer. The article was about changing the bar angles laterally to fine tune your set-up. Its been my experience also. Whats your opinion on this?

[7uptruckracer]

This is when you get out the tape measure and angle finder and see what changes and when. I am currently having this situation on a rocket that runs the Shorter LR upper. Trying to figure out if long bar and more angle is better with a constant hike number or it the short bar and adding angle quicker is better, which you sometimes get late exit loosness from. It really depends on the track and the driver in most cases but I find more on the longer bar these days

[billetbirdcage]

Billet, in a recent DLM mag tech article, Mr. Bush stated that indexing generally overrides roll-steer. The article was about changing the bar angles laterally to fine tune your set-up. Its been my experience also. Whats your opinion on this?

Ain't read it so in the dark here, but going of what I understand from your post..... I disagree I guess.

I assume when you say indexing your talking rod position on the birdcage and not the static clocking of the cage or rotation of the cage during hike.

Too vague to really give and answer without knowing what was said.

[25drtrkr]

Ain't read it so in the dark here, but going of what I understand from your post..... I disagree I guess.

I assume when you say indexing your talking rod position on the birdcage and not the static clocking of the cage or rotation of the cage during hike.

Too vague to really give and answer without knowing what was said.

The article was about moving the rod position side-to-side on the frame mount and/or the birdcage. He said the effects of indexing generally overrides the effects of rollsteer.

[billetbirdcage]

The article was about moving the rod position side-to-side on the frame mount and/or the birdcage. He said the effects of indexing generally overrides the effects of rollsteer.

When I refer to indexing, I generally use that to refer to rod position on the cage as in up or down location in the slot from axle tube centerline, but anyway.

Depends on how far you believe the rear end/bars are traveling side to side. I redrew in cad real quick because my memory sucks and couldn't remember the actual numbers.

From straight to X (X = travel in inches left or right)

17" bar from straight to 2" of angle = .117 shorter
3" travel = .266 shorter
4" travel = .475 shorter

Say its traveling 4" total

If bars are straight on LR, then the LR pulls forward .475 at the birdcage

If bars had 1" of toe to the right static and moves the same 4" then:

+.118 back for first inch travel left then forward -.266 for the next 3" for a total of .148 forward

A difference of .327 of steer at the cage between straight bars vs 1" of toe to RF, but I also don't think it's moving that far unless you got a ton of J-bar in the car, long chain length, so that number is likely more then actually seen.

Just to show you 4" of travel right to left is unrealistic, I drew it up in cad also:

19.5" j-bar starting a 8.5 of static rake

X = total rear end travel for inches dropped at pinion (keep in mind this is drop in pinion NOT the LR drop)

1" of drop = .520 to left
2" of drop = 1.118 to left
3" of drop = 1.801
4" of drop = 2.583

More static rake of 10.5" and 4" of drop at pinion is only 3.393 to the left

You can do the math or check for yourself what is likely a more reasonable amount of left movement on the rod ends and see if it makes that much difference for yourself.

Keep in mind the rotation of the rear end (rear view) is going to effect each rod ends movement left or right also, meaning that the RR upper rod will also move more left from the rotation of the rear end cause the LR is dropping and/or the RR compressing. (see below)

This may be small but still there and should be taken into consideration.

Only from rotation of rear end:
LRU = left then maybe back right
LRL = right
RRU = Left
RRL = Right then maybe back left

Billet

[Matt49]

When Mr Bush says "more indexing" he is usually referring to dynamic indexing whether that be through moving the bottom bar up on the frame or down on the pinion. Or moving the top bar down on the frame or up on the pinion. Just in general referring to the birdcage's ability to have the LR shock mount "chase" the chassis during rebound.
Indexing certainly gets thrown around in many different contexts but that is usually how I've seen him refer to it.

[fastford]

Giving lr more drop and less rear steer to tighten mid and exit. Just doesn't seem to be enough. Can't run stacked or bumps

you could do like some were doing before bump stops and two stage springs, run a soft right front and let it coil bind. you will have all the left rear drive you can stand. however, this is dangerous , especially on a rough track, but there has been a lot, and I mean a lot of races won in the slick this way before bumps and stacked/2stage was even heard of. I personally don't like this, but if my rules didn't allow bumps or 2 stage, id probably do it.

[Windy]

you also need to watch how much the track slows down to consider softening the right rear spring..a 1 and a 1/2 second slower track will need a 225 over a 250 or a 200 over a 225..lots of factors go with tuning a soft right front spring setup..you might even use a 175 left rear..lots of guys soften r.f. 25 lbs. each time on track and add a few turns to left rear..figuring everyone tunes like they used to..do you guys still tilt in the real slick..????..windy..