What does this picture say??

[Mad Hatter]

Am in the middle of a heated argument with my mechanic, he wants to stiffen the front shocks and springs because of this picture ( no rear bar)

And this Pic with rear bar.

Am I right to think that the weight transfer to the front is helping with front end grip?? and no need to stiffen up any more the front....

And yes..... In both pics am turning in a little late while braking..... No pics handy doing it right....

Have a BMR ajustable sway bar on full stiff and 600 lbs front springs. front Cortex coilover shocks are almost full hard.

Who is right????

 

[Grant 302]

I'm thinking only the guy behind the wheel can answer.

Hard to say that any changes are needed right now. The included pics aren't really helping IMO.

Was the car faster with the rear bar removed? Any issues with over/understeer anywhere?

I don't see excessive roll or dive and I'm thinking you don't need stiffer springs up front. If you aren't having or creating any understeer conditions, you could probably tolerate an increase up front.

...

And not to open the old can o' worms back up, but are you putting the power down on corner exit and thinking of more squat?

 

[Mad Hatter]

Lol, so as not to go back to the squatting debate!! Was just trying to focus on the brake dive.... Really like the way the car corners with either no bar or a new 15 mm setup that we were trying out.... (but the new bar snapped that day)...... But any ways back to brake dive...Went through lots of PWC videos looking at the Phoenix and Roush Stangs braking... (boy those car handle great)..... But did not find any so extreme as mine, the braking zone goes from 170km/h to 75km/h at that corner. My friend and mechanic is a avid racer who was a local champion is the 80's and 90's..... But some of his ideas are a little off the wall! Was looking for some info before he berates me again over this topic...

 

[Coz]

If controlling brake dive is a priority, what about a Torque Arm?

 

[ArizonaBOSS]

Better not show him this photo

 

[Norm Peterson]

front Cortex coilover shocks are almost full hard.

If those front coilovers are single-adjustable, them being full stiff isn't going to be doing much for you in those pictures (outside front moves in compression from both effects, inside front sees the difference between them and ends up not moving very much in either direction on corner entry).

With roll as well as dive going on, perhaps the front geometric roll center is too low.


Norm

 

[racer47]

Am in the middle of a heated argument with my mechanic...

You should not debate about if you need a change or not. You should only be debating about what to change now and what to try after that.

Unless you do something different and try things, you will never get faster. You will never learn for yourself how a given change effects the car. You will always be asking others for help and you will never really know for sure if they know what is best for your car, your track, your tires, your setup, etc. Free advice is worth exactly what you paid for it, including mine. Do you think those PWC cars are setup based on forum advice? Of course not. They do a lot of testing. So should you.

My free, arguably worthless, advice is to change something every time you go out on the track. If doesn’t always have to be big. At some point you will run out of hard parts to try like springs and bars, so try 2 psi higher or lower in the tires, try 2 psi more in front only, adjust the shocks, do something. Even if the car is good, tweak it and see if you notice a difference.

Back to your original question, if the car seems neutral and your mechanic thinks you need more front roll bar, talk about what you need to do to maintain car balance. Are you going to add a soft rear bar? Maybe go up 25 lbs on the rear spring rate? 50lbs? That should be the discussion. And yes, if you are aggressive with changes, sometimes you will end up slower but you can always go back and you will always be smarter regardless of the outcome.

Plus, don’t underestimate your mechanics knowledge and experience. We grew up racing with no internet, no forums, no free advice. I’m sure his knowledge was hard earned on the racetrack and he knows more about your car than all of us put together.

 

[Mad Hatter]

Lol,,, my car goes to the track with two or three changes at least for each event... have a hard time keeping up to his changes!! Don't worry! my crazy mechanic needs no defense!! ... I only but the brakes on him when he wants to strip out my cortex setup and make me a new suspension out of my old OEM boss shocks. Here in Chile he is known as "Loco Ramirez" but we get along well.

I was checking my logs, and at the point in the pictures, the car is pulling 1.31 G's, will check the front roll center as we just finished putting in the OEM A arms with spherical bearings and need to recheck the angles.... Am hoping roll center is the issue as the cars in the PWC videos are probably running 500# springs?? (and much better shocks) and you barely notice much dive (at least in the videos I saw). Is that right @blacksheep-1??

 

[racer47]

Straight line brake dive is a geometrical thing just like anti squat. Its often shown in side view with lines just like squat. Roll center is often shown with lines in front view. But both are really the 3d intersection of planes. To change dive you need to change the front to back angle of the control arms. Roll centers will change with ride height and suspension travel. And if you change ball joint height or contol arm mounting heights.

Maybe this will help, maybe not https://www.joesracing.com/rt-4196-why-anti-dive.html

I think you may be too focused on copying other cars. I'd focus more on your combination because you will never be able to get all the info on someones pwc car.

 

[Mad Hatter]

Interesting article. You mistake copying other cars with wanting to understand what makes them go fast. But I get your point. If some one is going faster then you it would be nice to know why.... Apart from having loads more talent!!

Now naturally if all this is old hat to you, things would be different......

 

[blacksheep-1]

Lol,,, my car goes to the track with two or three changes at least for each event... have a hard time keeping up to his changes!! Don't worry! my crazy mechanic needs no defense!! ... I only but the brakes on him when he wants to strip out my cortex setup and make me a new suspension out of my old OEM boss shocks. Here in Chile he is known as "Loco Ramirez" but we get along well.

I was checking my logs, and at the point in the pictures, the car is pulling 1.31 G's, will check the front roll center as we just finished putting in the OEM A arms with spherical bearings and need to recheck the angles.... Am hoping roll center is the issue as the cars in the PWC videos are probably running 500# springs?? (and much better shocks) and you barely notice much dive (at least in the videos I saw). Is that right @blacksheep-1??

Remember AJ was making spring adjustments in 15 pound increments at the end. the shocks really are the key once everything is close, those cars had well over the minimum of 4 inch ground clearance as well.
Maybe he'll chime in on this

 

[Grant 302]

You should not debate about if you need a change or not. You should only be debating about what to change now and what to try after that.

^This. And try more squat!

JMO, but if your car is turning fine, I think there's more time to be shaved in getting on the gas earlier, unlike what is shown in the posted pics. If there isn't a problem with the braking or some other problem that can't be described...I agree about not chasing the Phoenix/PWC setup, but 'learning to drive it the fast way' as mentioned previously in other threads.

Again, unless there's a problem, I wouldn't look for solutions that ultimately *reduce* grip on either axle. Stiffer up front would do that IMO, unless it would solve some other problem with balance or loss of grip via roll. Unless, perhaps, for the sake of 'fine tuning' as might be achieved with very small changes. But I don't think you're there yet.

 

[Mad Hatter]

Would happily agree with that.... Will keep fending off my guy for a bit... We made so many changes this last month I have a hard time keeping track. At least we are off to the track next on the 10 for a "test" day so will be checking all the variables!

Wanted to go from 600 to 500 front springs Lol

One thing I did check right away was the ground clearance to the K member and that was 4.25"

 

[docs302]

Remember AJ was making spring adjustments in 15 pound increments at the end. the shocks really are the key once everything is close, those cars had well over the minimum of 4 inch ground clearance as well.
Maybe he'll chime in on this

I think AJ may be too busy! I was at the shop Wed night talking to Joe about what I want them to do to my car and he gave me a tour of the facility. I walked into one of the garages and there are a couple of young guys busy wrenching on two cars. Had no idea it was AJ and Kurt. Amazing the number of cars scattered throughout the garages. Lots of Vettes. The Phoenix Boss 302's. Even someone's personal GT350. Pretty cool. Joe was great....can't wait to get the car set up and on track!

 

[Grant 302]

Would happily agree with that.... Will keep fending off my guy for a bit...

Just ask him to ride shotgun...

...In the trunk!

We made so many changes this last month I have a hard time keeping track.

I think that's a big danger if you don't have enough seat time to test and evaluate/quantify each change. Like do you have a read on if you were faster with the 15mm bar (before it broke) or no bar?

Wanted to go from 600 to 500 front springs Lol

Pretty sure that ain't the right direction! Well, not unless you drop a bunch of weight off the nose... or raise the roll center. JMO.

One thing I did check right away was the ground clearance to the K member and that was 4.25"

Are the A-arms level? And how much did the spherical bearings lower the rear connection? I try not to use clearances or ride height to verify geometry since tires and pressure make it variable and irrelevant. Good for a spot check but that's about it IMO.

 

[blacksheep-1]

In any case, the bottom pic says you need more camber..

Some pics of cars in transition, all of these are a bigger radius corner than the one in your pic. I suspect that the car works better in the larger corners, remember the corner leading onto the longest straight is crucial

one of the Roush cars running 275s at Daytona..under braking


Maybe Mid Ohio


COTA on Pirellis

 

[blacksheep-1]

I think AJ may be too busy! I was at the shop Wed night talking to Joe about what I want them to do to my car and he gave me a tour of the facility. I walked into one of the garages and there are a couple of young guys busy wrenching on two cars. Had no idea it was AJ and Kurt. Amazing the number of cars scattered throughout the garages. Lots of Vettes. The Phoenix Boss 302's. Even someone's personal GT350. Pretty cool. Joe was great....can't wait to get the car set up and on track!

If those guys aren't working, they're not breathing..

 

[Grant 302]

If those guys aren't working, they're not breathing..

When they're not working, I thought they come here and spread their knowledge!

 

[Grant 302]

In any case, the bottom pic says you need more camber..

Didn't look so bad when I bumped up the contrast to see the front left a bit better. Or I don't think it's quite gone positive in that pic.

I suspect that the car works better in the larger corners, remember the corner leading onto the longest straight is crucial

Thanks for putting up the pics Rob. I was going to refute the point about not finding pictures of either cars showing significant dive. I recall some others of the Phoenix cars tail up and nose down too.

 

[Norm Peterson]

Be careful if you're using the left rear wheel plane for reference. That wheel will be at a slight amount of positive camber, half a degree, maybe a bit more. Unless the rear axle has been cambered.


Norm