I'm not talking about shifting around, I'm talking about flexing. Flexing because the loading exceeds the torsional rigidity of the subframe.

 

My job is to test vehicles at the limit. I test for steering, suspension, and tire performance. When I test, the cars have sensors and we take data like steering angle vs yaw rate, yaw rate vs lateral g, steering angle vs yaw rate at different lateral g loads and lap times. There's GPS data to make sure I'm doing the same thing each time. When I test, every single variable is accounted for, down to tread depth and weather conditions. If the conditions aren't right, we don't test. I test in slaloms, max lateral g, auto-x, double lane change and hot laps sessions. It's my job to be consistent, precise, and fast. I find the limit and keep it there, so when something makes a car easier to hold at the limit and truly makes the steering more precise I notice it and appreciate it. I just want to let you know that I'm calibrated and my opinion is actually backed up by training and experience. Plus I've been going to track days for 11 years and worked for Honda's road race team for 4 years.

You're not wrong, all of those things go into car control. The discrepancy between what we're saying is that I feel a difference and you don't. You don't think I'm qualified to say that these parts do make a difference and I just "believe" it.

 

What did your instrumentation tell you about the x-brace? You've only mentioned the improved subjective 'feel.'

You say it's your job to be fast. How do you know you're fast? Do you race or run time trials? Competition will make you push your car beyond the limit and yet gather it up without loosing too much time. Because of that consistency suffers when trying to get that one golden lap out of 10 during qualification or TT. It's very different from running fast but consistent test laps.

I started doing track days in my bone stock S2000 and modified it over the years into a fully caged race car. I went from very slow newbie to NASA Mid Atlantic TTC champ. My car held the Summit Point TTR record for almost three years and I got within seven hundredths of the overall S2k track record (includes forced induction, NASA & SCCA racing qual and fastest race laps and time trials). The s2k handles very differently when approaching record lap times.

I still say if the x-brace improved the s2k's handling it would lower lap and course times and it would be a standard competition item like a bigger front anti-roll bar, camber adding front ball joints or the rear bump steer kit for the AP1. Instead the x-brace is known for adding weight to your car and reducing the weight of your wallet.

 

I thought we all got to a point where we agreed the x-brace didn't make the car faster but improved feel which improved consistency which in turn helped a turn faster lap times. Sounds to me like its a confidence booster thing. I have no doubt that an equal s2k with and without would turn identical lap times.

 

So back to alignment advice. -2.5 all around, stock toe. You'll be good

 

My $0.02, I agree with Rob.

An X-brace is not worth the mod money, but you can feel the difference in chassis stiffness…. IF you don't have other supporting mods.
We put an X-brace on back in 2003 and had it on for a year or so. It was tighter and if I think about it, it felt like an extra 50# of front sway bar stiffness or so. Maybe due to reducing torsion? But very subtle and would rather just do it with sway bar and spring.

Points of clarification:
X-brace would do even less in a car with a cage that has more chassis stiffness.
X-brace not legal for almost all autocross classes.

Just my opinion from my brief personal experience with them.

 

No track records here, must not be fast, so I'm out. What do I know?

No data on the X-brace. I've only tested for new model development stuff and Grand-Am cars, so there's no way that my subjective opinion means anything on my own personal car.

You win, I'm not qualified to offer a meaningful opinion.

 

These are the points raised in this thread that I disagree with:
This is the Racing and Competition forum and we live and die by lap times.





It's not the only way to test parts but it's the most important for people interested in competition.





More steering precision, feel and response will lead to better car control and lower lap times period.





'The limit' is a moving target and 'holding' the limit isn't the goal. A modification may lower the car's limit but the car may still feel good at the new lower limit. If you don't compare lap times you might think the modification was positive. This is the R&C forum and lap/course times trump 'feel'.

 

I get what you're saying and I agree that steering feel precision and control improve car control and can lower your lap times. What do you mean by "the limit is a moving target?"

I'm a test driver for suspension, steering, tire and brake performance. Understanding the tire's limit and what the car is doing at the tire's limit is what I do for a living to make sure the car handles and performs in all situations. In the same way that you described hitting kerbing, going offline to pass cars, off camber turns, etc. I test to make sure steering feel is consistent and predictable in those conditions. When a front subframe flexes, it is easy to tell through the steering wheel. Ever notice subframe or steering rack stiffeners on your Hondas? There are steering rack stiffeners on the CR to help improve steering feel and precision. They may help you set an overall faster lap time and you may not know they're on the car. If they didn't make a difference, Honda wouldn't spend the money to put them on the car.

When in a race car, in situations when I'm off line or going over kerbing and the car is loaded in an unpredictable manner, a stiffer front subframe improves the consistency of steering feel. But by virtue of being in that situation in the first place, you're probably not on your fastest lap and you're adapting to the track conditions at that point. Race car drivers tend not to care or notice in most cases (I've set cars up for professional drivers like Shane Lewis and I've worked with guys that were in F1, we've got a few of those hanging around at Honda), they just wheel the car into making it go fast. Also, fast laps differ with racing conditions like temp, sun, recent rain, dirt, dust, rubber, oil and coolant. So while that's great for getting fast lap times relative to a field of other cars that you're focused on avoiding and going around, it doesn't always help to improve and develop the car. Most of the time take the driver's description of what was happening and compare it with the data to fix handling issues and make the driver happier. That's not always the case, I've worked with several brilliant drivers that know far better than me what the car was doing and what needs to be improved...but those guys have own multiple national titles in SCCA and even a few grand am cup titles and they're working on the next NSX

Front subframe stiffness is key because it allows better tuning of the steering assist curve and the damping rates. If you're fighting any type of flex while trying to tune steering and damping you're chasing your tail. Tying the pick up points of the gaping hole across the bottom of the subframe (below the CG of the car too) is a good way to improve the rigidity of the front subframe.

I understand you're all about lap times and you're in the right forum for that, but it doesn't make you the end all authority. You have your experience and your opinion and people will listen to you. I also have an opinion and experience, they happen to be different from yours. You say I'm not qualified and my opinion and experience are wrong. I disagree and I think my job as a product development engineer for Honda and experience do qualify me and validate my opinion. If my opinion wasn't valid, I wouldn't be doing what I'm doing as a career.

 

I never said you're not qualified I just disagree with you on the x-brace. I agree a stiffer front subframe would be beneficial but the S2k has a stiff little chassis so I just don't think the x-brace does enough good to overcome its weight penalty--and that is just my opinion.



The 'limit' of tire adhesion changes during a race or session as the tires' temps and pressure changes. Overdrive the tires and the 'limit' lowers and lap times increase. A modified part may lower the car's limit but it could still feel good but the lower limit will raise lap times. A modification may raise the limit but give the limit a more knife edge feel that doesn't feel sd good but lap times come down. A smoother driver can raise a car's limit by not inducing understeer at corner entry or breaking the tires loose at exit. Two drivers can drive the same car 'at the limit' but the smoother driver's limit is probably higher with correspondingly lower lap times.

The limit is constantly changing. If your are "finding the limit and keeping the car there" without referencing lap times you're losing valuable data.