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Discussion Starter · #1 ·
So I finallly got a chance to test some of my new mods this past weekend. I headed over to BeaveRun in PA for a lapping day. Jinxxycat was there too and we both had a great time.

Okay, about the mods and the change in performance. Since the last time I hit the track (over a year ago), I added Hotchkis adjustable sway bars and set them for medium up front and medium in the rear. I also added Volk LE37T rims in 19x8.5 front and 19x9.5 rear. The rims are wearing Toyo T1-S 245/35-19 in front and Toyo T1-S 275/35-19 in rear.

Why did I make these changes? Well, when driving at Gingerman Raceway and Mid-Ohio, I noticed some pretty serious understeer for a sports car. I later read that some people had corrected the issue with adjustable sway bars and 245-series tires all around. In other words, they added mechanical grip up front with sways and wider tires. Since I have VDC and need (for the moment) to run my street tires on the track, I had to stick with 245 front and 275 rear.

This past Sunday, I discovered the results. The understeer is almost completely gone. The car is pretty flat in the turns and is very neutral. However, I still have the tiniest amount of understeer. So tiny in fact that I would not try to adjust it out with a stiffer sway setting in the rear. Instead, I am going to switch springs. The springs will add roll stiffness to the front and should work out that last little bit. If that does not work, then I will live with it. Truly, it is to tiny to be really concerned about.

As for the wheels and tires, the wider tire up front really helped. Also, the stickier TOYO tires made a huge difference in my cornering speeds. I could easily hold a higher speed through the corners. It was all really worth it.

Finally, for those that live in the midwest, I would highly, highly recommend attending a lapping session at BeaveRun. The facility is awesome, the track is wicked and safe, and the staff is great.
 

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So I finallly got a chance to test some of my new mods this past weekend. I headed over to BeaveRun in PA for a lapping day. Jinxxycat was there too and we both had a great time.

Okay, about the mods and the change in performance. Since the last time I hit the track (over a year ago), I added Hotchkis adjustable sway bars and set them for medium up front and medium in the rear. I also added Volk LE37T rims in 19x8.5 front and 19x9.5 rear. The rims are wearing Toyo T1-S 245/35-19 in front and Toyo T1-S 275/35-19 in rear.

Why did I make these changes? Well, when driving at Gingerman Raceway and Mid-Ohio, I noticed some pretty serious understeer for a sports car. I later read that some people had corrected the issue with adjustable sway bars and 245-series tires all around. In other words, they added mechanical grip up front with sways and wider tires. Since I have VDC and need (for the moment) to run my street tires on the track, I had to stick with 245 front and 275 rear.

This past Sunday, I discovered the results. The understeer is almost completely gone. The car is pretty flat in the turns and is very neutral. However, I still have the tiniest amount of understeer. So tiny in fact that I would not try to adjust it out with a stiffer sway setting in the rear. Instead, I am going to sway springs. This sway will add roll stiffness to the front and should work out that last little bit. If that does not work, then I will live with it. Truly, it is to tiny to be really concerned about.

As for the wheels and tires, the wider tire up front really helped. Also, the stickier TOYO tires made a huge difference in my cornering speeds. I could easily hold a higher speed through the corners. It was all really worth it.

Finally, for those that live in the midwest, I would highly, highly recommend attending a lapping session at BeaveRun. The facility is awesome, the track is wicked and safe, and the staff is great.
Great to hear, Peptide. I had the same experience with my setup changes. Isn't it incredible the difference the sways and tires make? I felt the same: before the mods, the car had too much understeer; after the mods it was perfectly balanced. I think it really shows how well the underlying systems are designed (suspension geometry, etc).
 

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What is a sway spring? Any more info on these?

I read somewhere that nylon (as opposed to urethane) sway bushings would be much better too. Not sure if it's correct or not though :dunno:
 

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I'm glad you posted this. That's almost the exact route I want to take with modding my car. I was thinking of sways and springs along with a wider wheel/tire combo. :clap:

Now to find a track in my neck of the Midwest... :wink:
 

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I'm glad you posted this. That's almost the exact route I want to take with modding my car. I was thinking of sways and springs along with a wider wheel/tire combo. :clap:

Now to find a track in my neck of the Midwest... :wink:
Don't pretend like you don't know about Brainerd, Dave. :nono: I'd better see you there next year. Need some Z's representing there. :cheers:
 

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Don't pretend like you don't know about Brainerd, Dave. :nono: I'd better see you there next year. Need some Z's representing there. :cheers:
:doh: Busted. You bet I'll be there next year! :shiftdrive:
 

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Well that's all good on paper Buddy but I can't distinguish if/or how bad it is, I am concentrating on keeping the 4 "contact patches" on the pavement first :wink: :rolf2:
yeah, it takes a lot of experience to be able to feel it in your butt when there's any loss of grip. Sure, anyone can tell when the tail is coming around fast, but to be effecient when driving on the track, you need to be able to tell when the front or rear (or all 4) starts sliding the teensiest bit. The best way to do that is to practice by finding a nice wide open parking lot and just throw the car around and find all the limits of adhesion. To practice understeer (again, this is in a BIG empty parking lot or something), go about 40-50 mph in a straight line, then turn the steering wheel sharply (about 1/3 to 1/2 turn) left or right and hold it there -- all the while maintaining constant throttle. You should notice how the car tracks outside the expected arc ("pushes").

Just a suggestion.
 

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I don't have enough track time under my belt to really recognize "understeer" but we are going to make some changes to our set up for next year's season for sure. :clap:


I recommend you take the Audi on the track for a lap. You will know understeer inside and out after that. I recently autocrossed a 2005 Audi A4 3.2, extreme understeer. Braking early is a must. Accelerating right on the apex is also a must - any sooner and you're going straight through the turn.
 

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Discussion Starter · #15 ·
What is a sway spring? Any more info on these?

I read somewhere that nylon (as opposed to urethane) sway bushings would be much better too. Not sure if it's correct or not though :dunno:
I meant "switch springs". By going to a spring with more roll stiffness in the front, I should be able to dial out the remaining understeer. Plus, the the softer rate in the rear will help to keep the ass planted under heavy acceleration.
 

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Finally, for those that live in the midwest, I would highly, highly recommend attending a lapping session at BeaveRun. The facility is awesome, the track is wicked and safe, and the staff is great.

Thank you!!

And just think, the best guy there, was out of the country!! :p

:nana:


:shiftdrive:
 

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With the reasonable torque available from our engine, a little corner entry understeer is a necessary evil in order to get the power down quick. If you are neutral during entry, you WILL exceed the traction limit of the rear tires on exit OR have to wait far too long to get back into the throttle. Just my experience.

uwaeve
 

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Discussion Starter · #18 ·
With the reasonable torque available from our engine, a little corner entry understeer is a necessary evil in order to get the power down quick. If you are neutral during entry, you WILL exceed the traction limit of the rear tires on exit OR have to wait far too long to get back into the throttle. Just my experience.

uwaeve
I didn't really have a problem with this. I was pretty neutral on entry and maintained the throttle to get into the turn. Then, just a split second after each apex, I got back on the throttle hard. It seemed to take the torque just fine. Even in the semi-hairpin #10 turn, it was just fine. Maybe this is because of the wider tire in the rear.

However, I did exceed the rear traction once. Again, it was in the #10 semi-hairpin, but it was my fault. I did not brake hard enough headed into the turn. Consequently, I almost overshot my turn-in point and I had to turn under braking. Well, we all know the risk of trail braking. About halfway though #10, I lost the rear end. It started to come around on me. Thankfully, I knew it was coming. I crammed on the gas and counter-steered. I saved the spin and we did not go all the way around. The next lap around, I found a better line for braking into #10.
 

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Discussion Starter · #19 ·
I don't have enough track time under my belt to really recognize "understeer" but we are going to make some changes to our set up for next year's season for sure. :clap:
I learned what understeer was in my old Maxima. I would enter a highway on one of those "clover leaf" ramps. I would head in with moderate speed and keep adding more through out the turn. About halfway up the ramp, you could feel the front "pushing". Essentially, I would have to dial in more and more steering to keep it on line. The front just wanted to straighten out. Essentially, the weight of the engine was pushing the front out.

If you want to feel it, grab the sedan you have and head for sharp highway on-ramps. It is a great way to safely learn what understeer is. You can also hit a empty parking lot. Start going about 35 and slowly turn. As you turn, constantly tighten the radius of the turn (as though the turn is getting smaller and smaller). You will end up going in tighter and tighter circles. Eventually, the radius of the turn will exceed what the car can handle at 35mph. The front will then start to "push".
 

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With the reasonable torque available from our engine, a little corner entry understeer is a necessary evil in order to get the power down quick. If you are neutral during entry, you WILL exceed the traction limit of the rear tires on exit OR have to wait far too long to get back into the throttle. Just my experience.

uwaeve
As you noted, that is your experience. Even at the top levels of racing, different drivers perfer different cornering tactics. I prefer a totally neutral setup simply because I like how it feels better than having any oversteer present.

Also, I think you are talking about an acceptable amount of understeer. IMO, the 350Z's stock setup has way too much. The car never had enough torque to correct the large amounts of understeer it had with the way it was setup. So the easiest (and cheapest) way to fix it was to dial out the understeer. The other solution would be to add more torque/power, but I prefer the low cost option, myself. :cheers:
 
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