I have a 1990 NA z32 as a race car. Full cage. 350 z rotors calipers on front. New wheel bearings and lower ball joints. Aftermarket front and rear sways. Everything torqued to spec. prior to run. Running 295/30/18 rears and
265/35/18 on front. Both have aluminum spacers.
Issue is violent front end shake with heavy braking. This is with straight line brake application. This gets worse as brakes have heat (2 laps on a road corse). At a loss as where to turn next. Looking for suggestions please.
Intense shudder to violent shaking when braking
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redmanmdsc
- Posts: 2
- Joined: Sun Apr 30, 2017 5:28 pm
- Car: 1990 300zx NA
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centralcoaster33
- Posts: 2634
- Joined: Tue Apr 05, 2005 10:41 am
- Car: 1997 Nissan 240SX #5
- Location: Central Coast, CA
Re: Intense shutter to violent shake with braking
I would have guessed bad wheel bearings. They are supposedly new. They have huge nuts to tighten to a heavy torque spec. Did you do those yourself or have them done? They might not have been installed correctly. That's what first comes to mind and since you've had them messed with, I suspect them even more.
Beyond that, spacers might be too thick. That would lend to your bearings not lasting long due to the leverage. Maybe the small bolts aren't torqued to spec for the spacers. Rotors may be warped. Steering rack may be worn, loose, have play or bad bushings letting it shimmy under heavy load.
Anyway, welcome to NICO Club! Hopefully some 300zx owners can chime in with some more experience.
Beyond that, spacers might be too thick. That would lend to your bearings not lasting long due to the leverage. Maybe the small bolts aren't torqued to spec for the spacers. Rotors may be warped. Steering rack may be worn, loose, have play or bad bushings letting it shimmy under heavy load.
Anyway, welcome to NICO Club! Hopefully some 300zx owners can chime in with some more experience.
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redmanmdsc
- Posts: 2
- Joined: Sun Apr 30, 2017 5:28 pm
- Car: 1990 300zx NA
Re: Intense shutter to violent shake with braking
New rack. This is our 3rd time through the bearings so I don't think the issue is on our end. The back nut was torqued to spec. We are replacing the rotors and pads to EBC orange. Also discussing suspension upgrades. Head scratcher right now though.
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DCaff300ZX
- Posts: 4202
- Joined: Sun Jun 14, 2009 8:18 am
- Car: .
1993 CRP TT- Modified - Location: Tacoma, Washington
Re: Intense shutter to violent shake with braking
Tension rods new, checked recently? Also, front upper control arms are often a problem, and the adjustable ones can come loose at the worst times unless the latest upgraded with locknuts.
My two first suspects beyond the large spacers which are never recommended.
My two first suspects beyond the large spacers which are never recommended.
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centralcoaster33
- Posts: 2634
- Joined: Tue Apr 05, 2005 10:41 am
- Car: 1997 Nissan 240SX #5
- Location: Central Coast, CA
Re: Intense shutter to violent shake with braking
Yeah, on my way home from work I was thinking about this and wanted to add that I've read about control arms and bushings being an issue for these cars in the front. Dcaff knows his stuff. I'm glad he's following. 3 sets of bearings? Well, you should be good at installing those by now. Have you ever replaced the knuckle or hubs? I think you could measure runout with a dial gauge so that you know you're putting new bearings between good components. I don't know though. I'll let the experienced guys take over. I hope you get your ride running strong for more track fun. Best of luck!
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DCaff300ZX
- Posts: 4202
- Joined: Sun Jun 14, 2009 8:18 am
- Car: .
1993 CRP TT- Modified - Location: Tacoma, Washington
Re: Intense shutter to violent shake with braking
Thanks centralcoaster!
BTW OP, I also cleaned up your post title.
I also just recently remembered the runout issue from my own brake issues, came back to update and am betting this is your issue.
Basically because of runout that is somewhat-known in the front hub of the Z32's, there is a TSB out regarding that Z32 front rotors should be spun and ground ON the car for accuracy to avoid the issue which is that due to runout in the hub that Nissan decided to NOT correct, and which after awhile and normal usage the pad thickness gets too light to completely grab the rotor as it spins and "loose spots" are the shaking feeling, not to mention the fact the runout makes for a non-circular rotation pattern we usually won't feel until braking. My clue was uneven pad wear, the bad (passenger) side was almost ground down on the edge while 90% at another location on the same pad. The other front was not nearly as bad, maybe 50% at worst spot while 80-90% elsewhere. BTW, I have completely replaced the front suspension with Powertrix coilovers and the necessary support arms, etc. so everything but the hubs and knuckles are new.
The solution is new components and changing out pads more often (complete GTR brakes, semi-metallic pads were my choice as it's not my DD), or to find someone who can handle rotor grinding on the car per the TSB instructions. I never went that far since the issue occurs after about two years of solid driving on fresh equipment which the car willdefinitely never see again.
I also would check the control arms for SURE as the FUCA is notorious and a really crude unit to boot, definitely the first thing I replaced in both cars and I'd DEFINITELY recommend that also for you if you have not- Powertrix has probably the best unit available, while the Z1 unit looks OK as well- both are DIY-able, have locking nuts and a very sensible system compared to crude OEM and other aftermarket solutions.
Last up would be subframe connector bushings and the bushings for the steering rack which I have read about failing often, my NA required a lot of service there.
Hope this helps!
BTW OP, I also cleaned up your post title.
I also just recently remembered the runout issue from my own brake issues, came back to update and am betting this is your issue.
Basically because of runout that is somewhat-known in the front hub of the Z32's, there is a TSB out regarding that Z32 front rotors should be spun and ground ON the car for accuracy to avoid the issue which is that due to runout in the hub that Nissan decided to NOT correct, and which after awhile and normal usage the pad thickness gets too light to completely grab the rotor as it spins and "loose spots" are the shaking feeling, not to mention the fact the runout makes for a non-circular rotation pattern we usually won't feel until braking. My clue was uneven pad wear, the bad (passenger) side was almost ground down on the edge while 90% at another location on the same pad. The other front was not nearly as bad, maybe 50% at worst spot while 80-90% elsewhere. BTW, I have completely replaced the front suspension with Powertrix coilovers and the necessary support arms, etc. so everything but the hubs and knuckles are new.
The solution is new components and changing out pads more often (complete GTR brakes, semi-metallic pads were my choice as it's not my DD), or to find someone who can handle rotor grinding on the car per the TSB instructions. I never went that far since the issue occurs after about two years of solid driving on fresh equipment which the car willdefinitely never see again.
I also would check the control arms for SURE as the FUCA is notorious and a really crude unit to boot, definitely the first thing I replaced in both cars and I'd DEFINITELY recommend that also for you if you have not- Powertrix has probably the best unit available, while the Z1 unit looks OK as well- both are DIY-able, have locking nuts and a very sensible system compared to crude OEM and other aftermarket solutions.
Last up would be subframe connector bushings and the bushings for the steering rack which I have read about failing often, my NA required a lot of service there.
Hope this helps!