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New 350Z Owner - trying to cure snap oversteer with Nismo S tune
Hello! I am a longtime motorhead but new to 350Z. This car is my replacement/upgrade track car. It has the Nismo S tune struts and springs, Hotchkiss adj sways and front adj upper control arms. At present it has 245/40/18 street tires on the rear and 225/40/18 on the front. Last alignment had 0 toe, -2 camber front; 1/4" toe in, -1 camber rear.
The problem is snap oversteer (not power oversteer - very little throttle involved). Wet road, right turn yield merge lane, not aggressive speed and whoosh, the car swaps ends. Later I try some on dry pavement and the feeling is the rear end taking the turn input and magnifying it rather than following the front. It is bad enough that I have NO confidence in this setup.
I'm looking for slight understeer and balance it with throttle. This is a track car, road race courses.
I've read the Nismo S tune rear progressive spring rates are too high. It does seem the harder I turn the worse the problem gets - i.e., the progressive firmness of the rear springs. The front sway bar is full stiff and the rear is full soft - I'd rather not disconnect the rear bar entirely.
My solution is to first go with NT01 track tires - 235/40/18 front, 275/35/18 rear. I would prefer however to have the same tires all around if possible but the car is useless the way it is. Second, replace the rear Nismo S tune springs with Tien S-tech - they have a lower rate and it is linear. I'd leave the Nismo shocks installed. If I get too much understeer at that point, I can start adjusting the sway bars and playing with tire pressures.
Am I on the right track? Any experience with the same problems?
Welcome and thanks for posting so much info on your suspension setup. While I have no experience with the S-Tune shock/spring package, I'm surprised to learn you have so much oversteer with your package. S-tune parts are not radically different than OEM, so I suspect they are not the biggest factor in your handling problems.
A couple of questions before offering any suggestions:
-What type of street tires are on the car? How worn are your rears compared with the fronts?
-What are your inflation pressures currently?
-Did you set the swaybars? Is it possible the links are preloaded?
-Did the previous owner offer any thoughts on how this suspension performed? Did he set it up himself and give you the specs, or did you have it recalibrated afterwards?
Street tires are Riken Raptor all season. Riken has always been crap but these actually get good reviews, even on Tire Rack. 300 A A rated. Not what I would buy but they are new and good enough for getting to the track (as long as I don't swap ends!)
Inflation pressures with the tires warm were around 38 PSI all around - I dropped that to 35 which is Nissan spec.
Sway bars were already set - which leads me to believe that contrary to the previous owner's assertion about the great handling, with the sway bars set to dial out as much oversteer as possible this problem has been there. Add to that the fact that the PO was a 911 driver - they like tail-happy cars. I prefer a bit of understeer - I've crashed once, thank you very much.
I have the specs and the records for the alignment, they all make sense. Visually I can confirm that the rear is not 6" toe-out - it looks right.
I found one thread on this forum that makes it sound like at least one other has had this problem with the Nismo S tune rear springs. If I find it again I will link it..........
I'm inclined to agree with DK. What I'd do-
1 Inspect fr and rr sways to rule out preload. You've got a nice suspension but if sways are installed incorrectly forces will fight each other.
2 Borrow a friends rr tires or replace with a better set on back.
3 Do a baby powder test on concrete to ck your tread contact patch.
Just a FYI always take tire rack and alike companies reviews and ratings with a grain of salt. Most people who buy tires off those sites (especially cheap ones) give them 5 stars as long as they don’t blow up in the first week. Most don’t even come close to pushing them hard enough to actually now how bad/good from one tire or another is.
And after workin I’m shops for a number of years the people who still think tires are good even past the cords is shocking.
I remember hearing rumors a while back that they have also been accused of hiding or deleting bad reviews from their site. Not sure how much truth that holds but I remember seeing a few people discuss it years back on other sites.
That said I would also double check sways bars for correction.
Inspect all suspension parts aren’t loose or broken
Try new better tires
And recheck alignment camber and all adjusters to make sure nothing walked or is messed up.
So on the "swaybar bind", the end links are factory, non-adjustable. I don't have any options there. Any pre-load should be minimal, and if it is somehow preloaded wouldn't that show up as "the car turns better in one direction versus the other"?
Forgot to mention, also have a Quaife LSD rear end...............
Ah, that's a big omission from your original post. A quaife LSD can bite hard and transfer power abruptly. That could be a significant factor in snap oversteer. My street Z still uses the VLSD and is quite mild on either the road or track. My race Z uses Koni 2812 DA shocks with #700 Eibachs up front and 450# springs in the rear. Together with the Nissan Comp swaybars (36 mm front, 27 mm rear) fully adjustable and a NISMO clutch-type LSD. My setup is to understeer slightly at the limit, but transition to power-on oversteer with power. It could be that your combination of suspension, tire and LSD is interacting with the good low end torque from the VQ to get you sideways quicker than you can catch.
So on the "swaybar bind", the end links are factory, non-adjustable. I don't have any options there. Any pre-load should be minimal, and if it is somehow preloaded wouldn't that show up as "the car turns better in one direction versus the other"?
Yes, that's usually true. But unless you have access to a skid pad or race course, it's hard to really say. However, if you're using the OEM (non-adjustable) end links, there's likely significant preload on them. And you DO have options- just buy some heim jointed swaybar links that'll fit your Hotchkiss bars and install them without any preload.
If you're skeptical if that'll help, just unbolt your rear bar and see how the car drives. It won't hurt anything and you might learn a thing or three.
Ah, that's a big omission from your original post. A quaife LSD can bite hard and transfer power abruptly. That could be a significant factor in snap oversteer. My street Z still uses the VLSD and is quite mild on either the road or track. My race Z uses Koni 2812 DA shocks with #700 Eibachs up front and 450# springs in the rear. Together with the Nissan Comp swaybars (36 mm front, 27 mm rear) fully adjustable and a NISMO clutch-type LSD. My setup is to understeer slightly at the limit, but transition to power-on oversteer with power. It could be that your combination of suspension, tire and LSD is interacting with the good low end torque from the VQ to get you sideways quicker than you can catch.
Well it would be an important omission except for the fact that I wasn't transferring any power - the initial rear-end swap happened without throttle input on a wet road and a mild mannered approach to the turn. Completely caught me by surprise, there was no input of power. Subsequent dry corners around the local curvy roads, without change in throttle, produced a rear end that was very eager to go 'round.
Yes, that's usually true. But unless you have access to a skid pad or race course, it's hard to really say. However, if you're using the OEM (non-adjustable) end links, there's likely significant preload on them. And you DO have options- just buy some heim jointed swaybar links that'll fit your Hotchkiss bars and install them without any preload.
If you're skeptical if that'll help, just unbolt your rear bar and see how the car drives. It won't hurt anything and you might learn a thing or three.
Certainly, unbolting the rear sway should help kill the oversteer, preload or not,, that is my last resort. But I should be able to check for preload just by pushing on the ends of the sway bar. If it is substantially preloaded, I won't be able to move it. And adjustable links are already on the wishlist.................
More searching on the Riken tires and really no complaints on a dozen different websites. Again, not what I would buy but they shouldn't be ice skates. When I get track tires (NT01) I'll set up the suspension for those but the decision to stagger or not is based on the car's handling before I buy them. I guess I'm going to pay the price and stagger - 235/40/18 up front and 275/35/18 in the rear. If I do understeer with these I still have all the sway bar adjustment range to get me back towards neutral, plus tire pressures as well. And some rear springs if I have to..............
Another update - After studying up on sway bar end links, I took another look at mine. The beefy Moog are on the back (where I have been spending the most time) but the front, with that monstrous Hotchkiss bar set full stiff, are the puny little OEM end links. I have service records showing the rear links being replaced but not the front. In my car's present state I can't get under it (yes, I started ripping stuff out to do other improvements) but I'm betting the cost of new end links that the front end links are toast. THAT would explain the severe oversteer, would it not?
I need to get this issue sorted before I plunk down a ton of money for staggered wheels and tires that go off sale in 13 days, so I ordered some Moog end links for the front. Hopefully my other parts will be here and I can road test it again before time runs out on the wheels and tires.
I double the opinion that you should look beyond your s-tune suspension to solve your problem.
I am on s-tune shocks and springs + stock sway bars - no oversteer at all...
Well I didn't like the design of the cheaper end links (that front bar will destroy them!) and I didn't like the price of the better end links. So I spec'd my own beefy links for less than $200:
Well I didn't like the design of the cheaper end links (that front bar will destroy them!) and I didn't like the price of the better end links. So I spec'd my own beefy links for less than $200:
04-16-2018, 05:05 AM
New 350Z Owner - trying to cure snap oversteer with Nismo S tune
