Chassis Stiffening importance...?

[TeeLew]

Generally, bump rubbers (which are just another spring) are used to 'help' with the aero loads, but also third or center springs. Bump rubbers can be a problem if track bumps cause you to hit them at the wrong time. Third springs are the opposite of an anti-roll bar. They act purely in heave and have no roll-stiffness contribution. If one makes the 3rd spring too stiff, though, it causes other issues. So what do you end up doing?

3rd spring as stiff as you can without it getting difficult to drive, bump rubbers as stiff as you can, but with a large enough gap that you're not touching them inadvertently, and the rest of the corner stiffness comes by way of the corner spring. If you need extra roll stiffness, then add an ARB. If you don't, remove it.

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[TeeLew]

Oddly enough he got the logic backwards. On a street circuit (or the street), you want less spring in favor of more ARB (better ride, important on bumpy street circuits). And race cars pretty much always want to run ARBs (for quick adjustability, especially something like a IndyCar, which has cockpit adjustable ARBs).

Not sure how we got to this discussion, from "How important is chassis stiffening."

It depends what you're trying to optimize. On an aero dominated car, controlling the aero platform is often a greater gain than the loss in grip due to reduced compliance. Making the car fast is more important than making the car ride smoothly. Driving a truly fast racecar on a street circuit is not a particularly nice thing. It's work.

It really doesn't matter who is saying what I am. Arguments from authority don't make a thing any more or less true.

We got here by the comment that some road cars run ARB's as decoration. I commented that race cars sometimes run then for the same reason.

 

[Grintch]

Generally, bump rubbers (which are just another spring) are used to 'help' with the aero loads, but also third or center springs. Bump rubbers can be a problem if track bumps cause you to hit them at the wrong time. Third springs are the opposite of an anti-roll bar. They act purely in heave and have no roll-stiffness contribution. If one makes the 3rd spring too stiff, though, it causes other issues. So what do you end up doing?

3rd spring as stiff as you can without it getting difficult to drive, bump rubbers as stiff as you can, but with a large enough gap that you're not touching them inadvertently, and the rest of the corner stiffness comes by way of the corner spring. If you need extra roll stiffness, then add an ARB. If you don't, remove it.

Good points on heave (3rd) springs being used for aero loads (generally only Formula cars and Prototypes). And bump rubbers being used for progressive rate.

 

[TeeLew]

Good points on heave (3rd) springs being used for aero loads (generally only Formula cars and Prototypes). And bump rubbers being used for progressive rate.

I'm not trying to be argumentative. I'm just sharing ideas. I've spent a fair bit of time thinking about these things.

 

[K4fxd]

I just did a manifold swap that I thought I was going to hate. So when I did my test drive I left off my strut tower brace and did not bolt down the strut to cowl brace.

I thought the whole front end was going to fall off. Pops bangs all kinds of movement up there.

This very unscientific test tells me the braces do work.

 

[Norm Peterson]

"Pops" and "bangs" are strictly NVH. Obviously small amounts of movement - vibration modeshapes - are happening, but they aren't significantly compromising the car's basic bending and torsional stiffnesses.


Norm

 

[K4fxd]

The witness marks showed the studs hitting the cowl brace. It felt noticeably firmer when I bolted everything back down.

The way I look at is if it didn't need it Ford would not have put them on the PP cars.

 

[Grintch]

The witness marks showed the studs hitting the cowl brace. It felt noticeably firmer when I bolted everything back down.

The way I look at is if it didn't need it Ford would not have put them on the PP cars.

Then the question is if it needed it, why didn't Ford put it on the non PP cars?
I am thinking different application, different needs.
Full race with slicks, full cage, various braces, and aftermarket K members etc. are useful.
Never take it to the track, and a stock, no brace non PP is fine.
As long as you have stock bushings everywhere, you will normally get a lot more defelection from those compared to from twist in the chassis. As you stiffen up everything else, you will start to have more benefit for chassis stiffening.

In general, bolting on braces doesn't show much improvement on lap times. So by my account not a must do, or a great value. You kind of do them when needed. The car should tell you when. If the car feels great now, it is not needed.

Give someone sugar pills and tell them they are medicine, and 80% of people will feel better. It doesn't make sugar pills the best medicine available. Or a must do. Change more money for the pills, and people will likely believe in them even more (or at least be less willing to admit they didn't do anything).

Note aftermarket K members, etc. sometimes have suspension geometry changes that are a completely different type of improvement.

 

[shogun32]

Then the question is if it needed it, why didn't Ford put it on the non PP cars?

artificial differentiation and opportunity to gouge customers $4000 for cost of goods of 1200.
This is not hard.

Never take it to the track, and a stock, no brace non PP is fine

Yes the car won't tie itself into knots and twist the frame apart while going thru a 4-leaf interchange. Is that the pathetically weak standard by which we accept "quality is job #1" from Ford?

Iif you give a prospective buyer a back-to-back drive in a non-PP and PP1 I'd guess a good 50% will readily tell the difference and prefer the latter. Ford is known to half-ass stuff because it's cheaper and for no other defensible reason. No, they don't need to make the cheapest Ecoboost set lap records at Gingermann, but if some trivial parts can improve performance, and you are going to make the assertion you're selling a 'performance' car, then you do ALL of the reasonable and customary stuff.

What possible reason was there to create 3 different dampers? The PP1 (nee FP Street) are complete and utter crap (rears at least) so it should never have been offered at all. If Ford Performance can't tell how shitty their namesake product was, then they need to resign in disgrace and be banned from ever working on suspension again.

In general, bolting on braces doesn't show much improvement on lap times. So by my account not a must do, or a great value. You kind of do them when needed. The car should tell you when. If the car feels great now, it is not needed.

practically nobody drives on a road course. While your skills may be such that you can wring the most out of a shitty platform and an extra brace here or there doesn't improve your times, good for you; but Normies and lesser-skilled people are able to feel the difference and appreciate it even if it doesn't make even a tenth per lap.

 

[K4fxd]

I have an S550 base and I did not like the way the car felt from the factory. It felt like a 70's Cadillac, float city.

Anyway for me the braces were a 100% improvment in the way the car feels. At the end of the day that is all that counts.

 

[Grintch]

I have an S550 base and I did not like the way the car felt from the factory. It felt like a 70's Cadillac, float city.

Anyway for me the braces were a 100% improvment in the way the car feels. At the end of the day that is all that counts.

Completely true.

But were the braces the only change you made? I wouldn't expect just braces to help with the under damped and too soft base suspension much. If it did for you, great.

Most of the look how great adding braces accounts I see are from when they added a whole bunch of suspension upgrades, and there is no way to tell what made what difference. Because they were not tested one by one, but only before and after.

 

[K4fxd]

I do have a bunch of suspension upgrades. I did them one at a time so I know what each contributed to the feel.

The order was, IRS braces then PP front braces, then dampers, then springs, then bushings. When I went around the block with the cowl brace unbolted I quickly remembered why I put it on.

 

[shogun32]

Most of the look how great adding braces accounts I see are from when they added a whole bunch of suspension upgrades, and there is no way to tell what made what difference. Because they were not tested one by one, but only before and after.

I'll give you that. But unless someone does their own work and doesn't value their time, very few people are going to do this strictly by the scientific method. they do all the "commonly accepted wisdom" upgrades all at once and be done with it.

I did all the upgrades at once and then when it was time to sell, removed the suspension and then the big K-brace from underneath and the Steeda IRS brace. Downgrade on the suspension was noticeable. Removing the braces was perceptible as well.

 

[Jaymar]

Long, long ago I had a '96 Mustang 2V with the factory handling pack consisting of 17" rims and the strut tower brace if I recall. After pulling the intake manifold (coolant leak, thank you Ford) I had the strut tower brace off and I went for a test drive, the difference was very noticeable but the SN95 platform wasn't known for its rigidity.

Fast forward to 2017, I have an Ecoboost PP1 which has the factory k-brace and cowl brace in place but for reasons only Ford could answer it didn't have the strut tower brace so I added one. Full factory PP1 no other modifications I think I felt a difference in front end responsiveness but I have to admit that the difference was so small that I can't tell you if it is an actual improvement or new part euphoria. I can't give you any objective feedback regarding lap times and I highly doubt there would be any but that's my take on the subjective feel.

Thank you everybody for your feedback though. I generally feel like most chassis braces are snake oil once you get beyond the Fox/SN95 chassis but I've been on the fence about the aftermarket forward K member braces and I think the discussion here has reaffirmed my feeling that it would be unnoticeable at best.

 

[K4fxd]

On the s550 the strut to cowl brace is more effective than the strut tower brace. Since both come in the kit I installed both. The front lower K brace was surprisingly effective.

I installed each piece one at a time to see what it did.

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