Nissan 370Z Forum - too much understeer now!

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Nissan 370Z Forum (http://www.the370z.com/)

- Brakes & Suspension (http://www.the370z.com/brakes-suspension/)

- - too much understeer now! (http://www.the370z.com/brakes-suspension/27773-too-much-understeer-now.html)

djpathfinder

11-16-2010 09:55 PM

Quote:

Originally Posted by vortrex (Post 811764)

anyone have pics of a 275/35 on a 9" wheel? it seems like that will be bulging like crazy. a 255/35 is a perfect fit. I thought I saw pics of a 265 on a 9" and even that looked like too much.

This is Zat_Zuma's ride. He's got 275 front and 305 rear on stock sport Rays.
http://www.the370z.com/members/djpat...mm-spacers.jpg

vortrex

11-17-2010 01:12 PM

wow, those fronts are really bulging.

djpathfinder

11-17-2010 01:51 PM

No they're not.

s30z	11-17-2010 02:34 PM

Yes, they are.

ChrisSlicks

11-17-2010 03:57 PM

No there not. It is just the design of the tire lip.

Nikon FM

11-18-2010 05:47 PM

Quote:

Originally Posted by vortrex (Post 809207)

I put 9x19 and 9x11 wheels with 255/35 and 295/30 hankooks with eibach springs and now have too much understeer. the alignment specs post spring install show -1.3deg and -1.4deg camber in the front.

can I get more negative camber out of the front with the stock bits? if so, what is suggested to relieve the understeer based off the tire sizes I am running? also, at what point do I start getting tire wear because of too much negative camber?

would sway bars help my situation at all?

thanks.

I run the OEM wheels with
255x30 Front
295x30 Rear
Toyo R888 tires on the track. I haven't experienced any understeer with the OEM suspension whatsoever. Pretty much point and go. With the springs and different wheel sizes there are a bunch of changes happening at once. If you still have your OEM wheels I'd swap out and see if the problem persists. Try and fix this by very small adjustments at a time…..just my 2 cents.

vortrex

11-18-2010 09:21 PM

I turned VDC off tonight and believe it or not that made a noticeable difference for the better. it's still not great, but much better than it was. I'll do some more testing with it to be certain.

djpathfinder

11-18-2010 10:22 PM

I'm puzzled...how would turning VDC off improve understeer?

vortrex

11-18-2010 11:38 PM

no idea, but I take the same route every day and it seemed better to me with it off.

Jessobear

11-19-2010 07:01 AM

The VDC system uses the brakes (I believe) to try and compensate for things like wheel spin. If he changed tire diameters significantly from stock, the VDC system may rear that as wheel slip due to differences in the rotational speed of the tires.

Next, try raising the front tires a bit and lowering the rears.

djpathfinder

11-19-2010 08:00 AM

Yeah, but with VDC on, are you noticing the slip light flashing, hearing/feeling the ABS go off, or feeling the car not keeping its speed during a turn? I thpught a 0.6" difference in tire diameter was acceptable. I know others have run a similar difference. How about slightly deflating the front (since the diameter is larger) and see if that equalizes front to back?

Jessobear

11-19-2010 10:06 AM

Reducing air pressure in the front tires reduces grip. It causes the tire to roll more in a corner.

corner3garage

11-19-2010 12:11 PM

i think a camber kit for the front with 2-2.5 degrees of negative camber would help a little bit, but you can also run a 255/285 combo to try and see if the rear doesnt push as hard.

vortrex

11-19-2010 12:23 PM

maybe the VDC thing is just my imagination then...

what air pressures should I be running?

my setup:

Hankook V12's

9x9 255/35
9x11 295/30

front = -1.3/-1.4 camber, .04 toe
rear = -1.6/-1.6 camber, .10/.08 toe

Jessobear

11-19-2010 01:08 PM

Not sure what the factory alignment specs are, but you have twice as much total toe in the rear than the front. I'll take a look at the settings later.

As far as tire pressures, take the factory spec and try +3 in the front and -3 in the back.

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