Thoughts on LF spring rate

[Matt49]

The prevailing mindset for years has been that LF spring rate really only affected corner entry. Which made a lot of sense when we were carrying the LF tire off the ground almost all the way around the track. But since we are getting the front ends of the car much flatter now on corner exit, is it time to re-examine this? I'm thinking one could really stand to benefit in the forward bite department by running a much softer LF spring to help dynamically wedge the car on exit. Then tighten entry back up using something else.

Any thoughts or am I losing my mind?

[swartzman]

I think you would fall out of your chair if you knew what people were really running in the fronts now days.. but your on the right path go explore some and see what you find

[FlatTire]

So englighten us Swartzman.....don't be a cahk tease.

[7uptruckracer]

I've seen as low a 400#s I still only use it for entry because that's the only time weight is transferring to the LF is on decel, and alot is being done on the compression side of the shock there to that is away from the old school trends to help get the weight there. This can allow you to run less rear steer which will help you get off the corner in certain conditions. Its a package deal for sure.

[swartzman]

350 at some tracks with a 200 and a bumpstop on the other.

[Matt49]

350 at some tracks with a 200 and a bumpstop on the other.

For flat, smooth, black slick race track. I don't doubt this one bit.

[hpmaster]

350 at some tracks with a 200 and a bumpstop on the other.

You got my attention please explain what your thoughts are.

[7uptruckracer]

On a LF????? Thats alot of rebound to get one on a bumpstop on the LF I'd imagine you have to be soft on the RF as well so the front end doesn't roll off the LF? We do that on the rears for asphalt when we run LR bumps

[Matt49]

On a LF????? Thats alot of rebound to get one on a bumpstop on the LF I'd imagine you have to be soft on the RF as well so the front end doesn't roll off the LF? We do that on the rears for asphalt when we run LR bumps

I think he meant 350 LF and 200 RF with a bump stop on the RF.

[RoundNrOUND]

200 with a bump on the RF makes sense if you can stop it from burying the frame. Also how bad is that killing your drive being that soft on the RF? I've ran a 300 with a bump but never softer than that.

[Matt49]

200 with a bump on the RF makes sense if you can stop it from burying the frame. Also how bad is that killing your drive being that soft on the RF? I've ran a 300 with a bump but never softer than that.

If using a xmas tree style bump, frame bottoming shouldn't be a big issue as long as the track is smooth. Running a bump on a rough track is pretty nuts anyway.
The trick is to have enough rebound in the shock to hold it on the bump thereby maintaining dynamic wedge to promote drive. Yes if you come off and end up on the 200 too soon, you're gonna be hosed on exit.
It takes some tweaking and patience to get it right...more than most people are willing to fuss with which is why many try it and can't get it to work right away and then give up on it.

[Ltemodel]

There are a couple different things going on with the LF that I see. The largest difference isn’t as much with the cars, but with the way people are thinking about their cars.

Years ago people used to charge the corner and decelerate quickly. A stiff LF spring used to add that good feel of side bite when they needed it. (deep in the corner) Now more and more people are lifting early and backing the corner up. They get back on the gas early and still have to finish the rest of the corner; using most of their tire for forward bite rather than sidebite.

Too stiff of a LF won’t allow the car to turn enough on entry and cause a car to be tight the rest of the corner. Softening the LF make the car drive better through the entire corner.

We tried stacking the LF a couple years ago with a driver who charged the corner and he hated it. He loves 525 or stiffer. (Anything under that and it’s too free on entry)

I think about the LF a little differently than most.

On acceleration, the LF can be considered like a four legged table with only three legs touching the floor. The stiffer the spring, the faster the weight leaves that corner of the car on acceleration. Picture a car with a 300 lb LF spring. If the LF spring is preloaded 2”, it takes 2” of lift to totally unload that spring and redistribute the weight somewhere else in the car. A 600 lb spring will only take 1” of lift to redistribute the same amount of weight. The soft LF will potentially hold more weight longer.

A soft spring will compress more on deceleration and lower the nose to keep more air going over the top and less underneath. (producing more down force on the car.) I consistently hear more and more drivers complain about aero problems nowadays than I did years ago. So, I think this also needs to be taken into consideration when choosing a LF spring.

Then you could potentially chain your LF down. There are whole new avenues to go to here. Running a stiff spring and chaining it down could have the aero advantages of the soft spring by keeping the nose down; while still keeping the car tight on entry like some drivers like.

For the guys who are running the softer spring, what do you feel is the advantage you are gaining? Where do you feel it helping your car the most?

Interesting topic.

Kevin

[HuckleberryB4]

BTT. Hoping to see some more info on this.

[7uptruckracer]

I've put alot of thought into this and I think this is one of the newest areas to work. The front ends are so much more efficient then they use to be. They used to be rear end dominant and now that's not the case you see a lot less rear weight then days past, A lot more left side weight. Lower front roll centers. Less rear steer. You really see the LF working these days. The cars don't roll as much yes they still dive on the RF but you have the LF getting into the track with it and you see them with the noses sealed off and don't see the nose height change much down the straights and the LF fender gap change much as they go into and through the corner. Like someone else said you don't have to use all your grip up to get in and turn because the care is doing it on its own. One new manufacturer their baseline is a 400 LF in the heavy. I like the ideas maybe a low compression high rebound soft spring combo is next like we run on asphalt I can totally see that, asphalt it effect exit because it holds available weight for transfer on exit from being able to get back there. Why wouldn't this work on dirt?

[Matt49]

The cars of today even compared to 10 years ago have so much more side bite and so much more front end "steerability" that when the track is slick they can basically be steered through the corner rather than sliding so much. It's like racing on slick pavement. What's been the hot setup on pavement for several years? BBSS. Well dirt cars don't have a sway bar but there are things that can be done to make it behave like it does...
...just more food for thought.