Nissan 370Z Forum  

Reduce nose dive under heavy braking

Hi guys need a bit of help here, During autox events whenever I do heavy braking I notice that the rear end gets very loose and unstable. Since I have

Go Back   Nissan 370Z Forum > Tech Area > Track / Autocross / Drifting / Dragstrip

Like Tree2Likes

Reply
 
LinkBack Thread Tools Display Modes
Old 06-29-2015, 10:48 AM   #1 (permalink)
Enthusiast Member
 
redline10000's Avatar
 
Join Date: Nov 2012
Location: boston
Posts: 256
Drives: 2011 370z sport
Rep Power: 5
redline10000 is on a distinguished road
Default Reduce nose dive under heavy braking

Hi guys need a bit of help here,

During autox events whenever I do heavy braking I notice that the rear end gets very loose and unstable. Since I have installed coilovers it has gotten better but I still would like to reduce nose dive and increase stability if possible.

I understand that one way to fix this problem is to up my front spring rate but I really don't want want stiffer springs up front. 750lb is already rough at times, lots of potholes where I live. Is there another way to gain stability by adjusting ride height,toe or reducing rear spring rates?

Here is my setup incase this helps:

custom valved konis with 750lb springs up front and 600lb (might be too stiff) springs in the rear.
-1.9 degrees camber front and -1.7 degrees camber rear
0 toe front 0.16 rear
Car is corner balanced and has a ride height of 27" in front and 27" 3/16 rear
__________________
AAM Axleback + AAM Midpipe | K&N Drop in filters | Eibach Front Sway bar |Whiteline diff bushing| Dunlop ZII
redline10000 is offline   Reply With Quote
Old 06-29-2015, 11:01 AM   #2 (permalink)
Base Member
 
Blighter's Avatar
 
Join Date: Jun 2015
Location: Oklahoma
Posts: 137
Drives: 13Nissan370zBlkM6
Rep Power: 8
Blighter has a reputation beyond reputeBlighter has a reputation beyond reputeBlighter has a reputation beyond reputeBlighter has a reputation beyond reputeBlighter has a reputation beyond reputeBlighter has a reputation beyond reputeBlighter has a reputation beyond reputeBlighter has a reputation beyond reputeBlighter has a reputation beyond reputeBlighter has a reputation beyond reputeBlighter has a reputation beyond repute
Default

Just wondering, but can't you stiffen up or adjust the front struts to be stiffer?
__________________
2013 Base 6 speed MT Magnetic Black
Injen CAIs
Berk Resonated Cats
Swift Springs
Blighter is offline   Reply With Quote
Old 06-29-2015, 11:48 AM   #3 (permalink)
Bad Decision Maker
 
gomer_110's Avatar
 
Join Date: Aug 2011
Location: Perrysburg, OH
Posts: 15,746
Drives: '11 Nismo #528 GM
Rep Power: 6129
gomer_110 has a reputation beyond reputegomer_110 has a reputation beyond reputegomer_110 has a reputation beyond reputegomer_110 has a reputation beyond reputegomer_110 has a reputation beyond reputegomer_110 has a reputation beyond reputegomer_110 has a reputation beyond reputegomer_110 has a reputation beyond reputegomer_110 has a reputation beyond reputegomer_110 has a reputation beyond reputegomer_110 has a reputation beyond repute
Default

Single or double adjust Koni's? Also what brake pads front and rear are you running?

fwiw I run 1100 lb springs front and 900 lb rear on mine with custom valved 2-way AST shocks.
__________________
'11 370Z Nismo #528 Fast Intentions | Stillen | Motordyne | CSF | Zspeed | Z1 Motorsports | AST | SPC | SPL | Whiteline | Hotchkis | Bride | Schroth | Robispec | Cusco | Whiteline | Nismo | Volk | Hoosier
'17 Titan Bone Stock
gomer_110 is offline   Reply With Quote
Old 06-29-2015, 12:11 PM   #4 (permalink)
Enthusiast Member
 
redline10000's Avatar
 
Join Date: Nov 2012
Location: boston
Posts: 256
Drives: 2011 370z sport
Rep Power: 5
redline10000 is on a distinguished road
Default

Quote:
Originally Posted by Auspicious_one View Post
Just wondering, but can't you stiffen up or adjust the front struts to be stiffer?

Good point I have my konis on .5 turn from full stiff front and 1 turn from full stiff rear.

Quote:
Originally Posted by gomer_110 View Post
Single or double adjust Koni's? Also what brake pads front and rear are you running?

fwiw I run 1100 lb springs front and 900 lb rear on mine with custom valved 2-way AST shocks.
Its SA Koni yellows revalved by proparts usa. The shocks can handle higher rates but the car is my DD. I have EBC redstuff front and rear with stock rotors.
__________________
AAM Axleback + AAM Midpipe | K&N Drop in filters | Eibach Front Sway bar |Whiteline diff bushing| Dunlop ZII
redline10000 is offline   Reply With Quote
Old 06-29-2015, 01:22 PM   #5 (permalink)
Track Member
 
Join Date: Apr 2015
Location: Columbus OH
Posts: 508
Drives: K2|Z34|C6Z06|C5Z06
Rep Power: 4
POS VETT will become famous soon enough
Default

You will need double-adjustable dampers with individual adjustment. Increasing compression damping reduces brake dive to a point. While brake dive is one thing, there is a possibility that the rear brake pads are a bit too aggressive initial bite creating a slight instability during heavy braking.

Also, some suspension designs incorporate an anti-dive geometry. Has the car been lowered by a substantial amount?
POS VETT is offline   Reply With Quote
Old 06-29-2015, 03:40 PM   #6 (permalink)
Enthusiast Member
 
redline10000's Avatar
 
Join Date: Nov 2012
Location: boston
Posts: 256
Drives: 2011 370z sport
Rep Power: 5
redline10000 is on a distinguished road
Default

Quote:
Originally Posted by POS VETT View Post
You will need double-adjustable dampers with individual adjustment. Increasing compression damping reduces brake dive to a point. While brake dive is one thing, there is a possibility that the rear brake pads are a bit too aggressive initial bite creating a slight instability during heavy braking.

Also, some suspension designs incorporate an anti-dive geometry. Has the car been lowered by a substantial amount?
The car is 27 inches from the ground in the front and 27 and 3/16th in the rear. I don't think its the brake pads since its was squirrely when I had stock pads. The car is much more improved this year with SA colivers and the drop vs stock but I still feel like there's more stability to be had under hard braking.

Could some of the instability under braking be caused by toe loss when the rear end is unloaded?
__________________
AAM Axleback + AAM Midpipe | K&N Drop in filters | Eibach Front Sway bar |Whiteline diff bushing| Dunlop ZII
redline10000 is offline   Reply With Quote
Old 06-29-2015, 04:09 PM   #7 (permalink)
Track Member
 
Join Date: Apr 2015
Location: Columbus OH
Posts: 508
Drives: K2|Z34|C6Z06|C5Z06
Rep Power: 4
POS VETT will become famous soon enough
Default

Quote:
Originally Posted by redline10000 View Post
The car is 27 inches from the ground in the front and 27 and 3/16th in the rear. I don't think its the brake pads since its was squirrely when I had stock pads. The car is much more improved this year with SA colivers and the drop vs stock but I still feel like there's more stability to be had under hard braking.

Could some of the instability under braking be caused by toe loss when the rear end is unloaded?
I'm unsure about those ride height numbers since I don't have a point of reference.

Rear toe out gain is also a possibility. If there is a considerable amount of rear-steering is built into the suspension design, rear would toe out during a hard braking. However, this is only at an autox; can you adjust your driving style to take advantage of it? I don't race my 370Z, but many years ago when I autoxed my '95 Eagle Talon TSi AWD, I gained a habit of trail braking because the car would rotate under hard-braking.

One other thing, if the instability was indeed due to the rear wheel steering, see if more toe in in the rear could be dialed in.

Last edited by POS VETT; 06-29-2015 at 04:13 PM.
POS VETT is offline   Reply With Quote
Old 06-29-2015, 04:25 PM   #8 (permalink)
Enthusiast Member
 
redline10000's Avatar
 
Join Date: Nov 2012
Location: boston
Posts: 256
Drives: 2011 370z sport
Rep Power: 5
redline10000 is on a distinguished road
Default

Quote:
Originally Posted by POS VETT View Post
I'm unsure about those ride height numbers since I don't have a point of reference.

Rear toe out gain is also a possibility. If there is a considerable amount of rear-steering is built into the suspension design, rear would toe out during a hard braking. However, this is only at an autox; can you adjust your driving style to take advantage of it? I don't race my 370Z, but many years ago when I autoxed my '95 Eagle Talon TSi AWD, I gained a habit of trail braking because the car would rotate under hard-braking.

One other thing, if the instability was indeed due to the rear wheel steering, see if more toe in in the rear could be dialed in.
stock height is 27.89 and 27.99 so my drop is very mild. If toe is my problem I can definitely go and get some more dialed in. At the moment I only have about 1/8th toe in with me in the car. I can try trail braking if that is what it will take to keep the rear end from wagging around.
__________________
AAM Axleback + AAM Midpipe | K&N Drop in filters | Eibach Front Sway bar |Whiteline diff bushing| Dunlop ZII
redline10000 is offline   Reply With Quote
Old 06-29-2015, 06:53 PM   #9 (permalink)
A True Z Fanatic
 
Join Date: Jun 2014
Location: Claxton, Ga
Posts: 2,493
Drives: 2013 Nismo 370z
Rep Power: 2192
Spooler has a reputation beyond reputeSpooler has a reputation beyond reputeSpooler has a reputation beyond reputeSpooler has a reputation beyond reputeSpooler has a reputation beyond reputeSpooler has a reputation beyond reputeSpooler has a reputation beyond reputeSpooler has a reputation beyond reputeSpooler has a reputation beyond reputeSpooler has a reputation beyond reputeSpooler has a reputation beyond repute
Default

The number one thing I would say is to adjust your driving style to not require so much braking. Braking scrubs off speed. Find a way to keep more speed requiring less braking.
Spooler is offline   Reply With Quote
Old 06-29-2015, 06:54 PM   #10 (permalink)
Enthusiast Member
 
redline10000's Avatar
 
Join Date: Nov 2012
Location: boston
Posts: 256
Drives: 2011 370z sport
Rep Power: 5
redline10000 is on a distinguished road
Default

I found this article. I might try some of the tips.My rear damping was up a bit high.

Handling Guide | RACING ON THE CHEAP

Instability under hard braking: car wants to spin
• Excessive rear brake bias
• Insufficient rear droop travel
• Wildly uneven corner weights
• Excessive rear damper rebound force
• Unbalanced ride/roll resistance – too much at rear
• Insufficient rear camber (usually in combination with one or more of
the above)
Brendan likes this.
__________________
AAM Axleback + AAM Midpipe | K&N Drop in filters | Eibach Front Sway bar |Whiteline diff bushing| Dunlop ZII
redline10000 is offline   Reply With Quote
Old 06-29-2015, 07:01 PM   #11 (permalink)
Premium Member
 
Join Date: May 2011
Location: Hinckley IL
Posts: 227
Drives: 2012 370Z, 99 SM
Rep Power: 7
Zauskycop will become famous soon enough
Default

A tad more rear toe, softening the rear shocks, and more importantly, is the is happening in straight lines, or trail braking??

Tracy Ramsey
Zauskycop is offline   Reply With Quote
Old 06-29-2015, 07:58 PM   #12 (permalink)
Track Member
 
Join Date: Apr 2015
Location: Columbus OH
Posts: 508
Drives: K2|Z34|C6Z06|C5Z06
Rep Power: 4
POS VETT will become famous soon enough
Default

When I mentioned trail braking, I meant to say that I changed my driving and used that feature to my advantage. In my current car that's RWD, I can't use trail braking; it just doesn't work in an autox, might work when I want to slide around, but it induces major, sometime unrecoverable, power oversteer. I use a small amount of throttle to maintain a more steady cornering speed.

It's hard for me to say what you could use that instability for without being there. A very brief application of trail braking might work in your case as long as throttle is applied gradually afterward. Watch for the weight shift and start from there. You might or might not be comfortable with a tiny slide for a quicker rotation purpose. What tires do you run?
POS VETT is offline   Reply With Quote
Old 06-29-2015, 10:13 PM   #13 (permalink)
Track Member
 
GSS138's Avatar
 
Join Date: Mar 2013
Location: Mission Viejo, CA
Posts: 769
Drives: '12 370Z 6M Sport
Rep Power: 6
GSS138 is a jewel in the roughGSS138 is a jewel in the roughGSS138 is a jewel in the rough
Default

Quote:
Originally Posted by redline10000 View Post
Hi guys need a bit of help here,

During autox events whenever I do heavy braking I notice that the rear end gets very loose and unstable. Since I have installed coilovers it has gotten better but I still would like to reduce nose dive and increase stability if possible.

I understand that one way to fix this problem is to up my front spring rate but I really don't want want stiffer springs up front. 750lb is already rough at times, lots of potholes where I live. Is there another way to gain stability by adjusting ride height,toe or reducing rear spring rates?

Here is my setup incase this helps:

custom valved konis with 750lb springs up front and 600lb (might be too stiff) springs in the rear.
-1.9 degrees camber front and -1.7 degrees camber rear
0 toe front 0.16 rear
Car is corner balanced and has a ride height of 27" in front and 27" 3/16 rear
This car does funny things with rear toe out try a touch rear toe in. Your spring rates are not the reason (most likely) you are having braking problems. Probably your pads. Most people prefer a little less aggressive pad in the rear.

OEM anti-sway bars?
__________________
Current Mods: Vorpal Weapon +5.
GSS138 is offline   Reply With Quote
Old 06-30-2015, 06:50 AM   #14 (permalink)
Bad Decision Maker
 
gomer_110's Avatar
 
Join Date: Aug 2011
Location: Perrysburg, OH
Posts: 15,746
Drives: '11 Nismo #528 GM
Rep Power: 6129
gomer_110 has a reputation beyond reputegomer_110 has a reputation beyond reputegomer_110 has a reputation beyond reputegomer_110 has a reputation beyond reputegomer_110 has a reputation beyond reputegomer_110 has a reputation beyond reputegomer_110 has a reputation beyond reputegomer_110 has a reputation beyond reputegomer_110 has a reputation beyond reputegomer_110 has a reputation beyond reputegomer_110 has a reputation beyond repute
Default

A few things to try:

1) 1/16-1/8 total toe-in in the rear.

2) Disconnect one side of the rear sway bar at your next autox event.

3) For at least one run go full soft on the rear shocks and full stiff (or close to it) on the front shocks.

While none of these will do much for the nose dive issue, both of these should "tighten" the car up and help stabalize the rear end.
__________________
'11 370Z Nismo #528 Fast Intentions | Stillen | Motordyne | CSF | Zspeed | Z1 Motorsports | AST | SPC | SPL | Whiteline | Hotchkis | Bride | Schroth | Robispec | Cusco | Whiteline | Nismo | Volk | Hoosier
'17 Titan Bone Stock
gomer_110 is offline   Reply With Quote
Old 06-30-2015, 11:54 AM   #15 (permalink)
Enthusiast Member
 
redline10000's Avatar
 
Join Date: Nov 2012
Location: boston
Posts: 256
Drives: 2011 370z sport
Rep Power: 5
redline10000 is on a distinguished road
Default

Thanks for all of the replies lots of good info here. One thing I want to clear up first is that I do have 1/8th toe in, actually I have 0.16 so a little more than 1/8th. My previous statement about toe out was that maybe as the rear is unloading the reduction of toe-in is causing me some grief.

Suggestions that I will try at this weekends event are:
Setting the rear shocks to full soft
Disconnecting the rear bar ( if i can borrow a jack while at the event)
Upping my front damper stiffness to reduce nose dive

If none of the above helps I will get my alignment checked and make sure that nothing got out of whack.

As for the nose dive, I guess I will have to learn to live with it. I don't want heavier springs up front as roads are really rough here and I can't find a set of 2 way coils that don't cost 3k+.
__________________
AAM Axleback + AAM Midpipe | K&N Drop in filters | Eibach Front Sway bar |Whiteline diff bushing| Dunlop ZII
redline10000 is offline   Reply With Quote
Reply

Bookmarks

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Brief RPM dive when stopped. gbrettin Engine & Drivetrain 35 09-15-2015 09:25 AM
Tires that reduce noise Steve G Wheels & Tires 14 05-03-2014 07:22 PM
Reduce Brake Temperatures : Ideas ?? osbornsm Nissan 370Z General Discussions 7 10-09-2012 05:30 PM
Want to reduce weight need ideas Mino Track / Autocross / Drifting / Dragstrip 3 06-30-2012 01:16 PM
Fender Coating to reduce noise Minicobra1 Nissan 370Z General Discussions 44 02-13-2011 08:12 PM


All times are GMT -5. The time now is 07:48 PM.


Powered by vBulletin® Version 3.8.4
Copyright ©2000 - 2017, Jelsoft Enterprises Ltd.
Search Engine Optimization by vBSEO 3.6.0 PL2