1 2
jharry3
jharry3 Dork
8/24/21 5:17 p.m.
Tom1200 said:

I always go by Carroll Smith's fix the end that isn't working. With that said if adjusting the rear bar leads to improved times then so be it.

He also said to stiffen the rear to reduce front understeer...

Tom1200
Tom1200 SuperDork
8/24/21 6:03 p.m.

In reply to jharry3 :

True but the preffer option was to work on the end that was the problem.

End of the day it's improved times that matter; whether you get there with a stiffer rear bar or a softer front really doesn't matter, regardless of one might prefer. 

Patientzero
Patientzero Dork
8/24/21 7:47 p.m.

This is a great read.  It does a good job of explaining balance.  He also says to improve the end that isn't working first but unstick the other end is a secondary (but ultimately slower) option.

http://farnorthracing.com/autocross_secrets7.html

Driven5
Driven5 UltraDork
8/25/21 10:24 a.m.
Tom1200 said:

I always go by Carroll Smith's fix the end that isn't working...

It's been a while, but didn't he also typically allude to his generalizations being based on cars with more idealized designs for racing? Struts can often act contrary to his conventional weight transfer based suspension tuning due to their poor camber control in roll, especially when paired with a suspension that doesn't need good roll control to maintain camber at the opposite end. You can often counter-intuitively reduce understeeer on cars with front struts by putting on a larger front sway bar, since more is gained from the additional roll (and thus camber) control than is lost by the worse lateral load transfer. While my guess is that the front is already stiff enough to get beyond that, reducing the front roll (and thus camber) control will still be fighting against your lateral load transfer gains from doing so. So in this particular scenario, it seems to me that fixing the the end that isn't working might actually mean increasing lateral load transfer to the inside front tire, but in a way that specifically doesn't also allow for additional total roll... Or perhaps even reduces it. So stiffening the rear would fit still the bill.

asphalt_gundam
asphalt_gundam Reader
8/25/21 11:07 a.m.

I just dealt with understeer on my cutlass on the road course last weekend. Fix was softening the front shocks a few clicks and stiffening the rears a couple clicks. I started out with the rear sway bar off and tested putting it on...bad move...wild ride of very loose rear after that. The shocks were the much better adjustment. Also where are your rear control arms at? If they're set to provide maximum traction they could be taking a lot of weight away from the front making it push on throttle. Verify that you're not on the bump stop mid corner too.

Pete. (l33t FS)
Pete. (l33t FS) MegaDork
8/25/21 12:09 p.m.
Driven5 said:
Tom1200 said:

I always go by Carroll Smith's fix the end that isn't working...

 Struts can often act contrary to his conventional weight transfer based suspension tuning due to their poor camber control in roll, especially when paired with a suspension that doesn't need good roll control to maintain camber at the opposite end. You can often counter-intuitively reduce understeeer on cars with front struts by putting on a larger front sway bar, since more is gained from the additional roll (and thus camber) control than is lost by the worse lateral load transfer.

When strut suspension gets this bad, it is usually on something that lifts a rear tire. Once you are on three wheels, the idea of adjusting suspension by juggling load transfer goes out the window, one end is already at 100%, so the other end's load transfer is strictly G vs. track width vs. center of gravity height, no matter what the suspension is doing.

 

Puhn said you can't tune a tricycle, and he's right to an extent, but sometimes you just gotta lift a wheel on corner entry (or exit) so the suspension works the rest of the time...

Tom1200
Tom1200 SuperDork
8/25/21 1:12 p.m.

In reply to Driven5 :

I actually raised the ride height in the front of the Datsun due to roll effecting camber, the car was to low. The real solution would be to move the pick up point for the lower control arm but that's a lot of work relative to the ride height change. 

Driven5
Driven5 UltraDork
8/25/21 2:37 p.m.
Pete. (l33t FS) said:
Driven5 said:
Tom1200 said:

I always go by Carroll Smith's fix the end that isn't working...

 Struts can often act contrary to his conventional weight transfer based suspension tuning due to their poor camber control in roll, especially when paired with a suspension that doesn't need good roll control to maintain camber at the opposite end. You can often counter-intuitively reduce understeeer on cars with front struts by putting on a larger front sway bar, since more is gained from the additional roll (and thus camber) control than is lost by the worse lateral load transfer.

When strut suspension gets this bad, it is usually on something that lifts a rear tire...

What you're describing is a FWD specific variation of what I described.

.

In reply to Tom1200 :

Good point. Raising the front ride height to raise the roll center would be something both cheap and easy to test as well.

1 2
Our Preferred Partners
8xqs1tlD3TVf7XYO6RLnILtdUcyN6Bmg1z50z4XntTbcJuWMoUbLrNFKfLRuHU4K