Car: 07 350z Grand Touring with 19x10 in back with 265 35 19 and 18x9 in front with 245 45 18 in front(stock 07 GT rims and tire size), SPC Front A arms, BC Coilover shocks with 10/10 springs, lowered approximately 1.5" in front and 1" in back. Symptom is over rough road(not even large bumps-more like man hole cover, pot hole, bridge pavement bump and such) I would get this annoying metal on metal clunk. After hours of research, lots of time on the phone and some time under my fender I found the main reason for my clunk noise(see pic links). Now keep in mind BC Racing is being cool about checking their stuff and I still have a few question for them on spring rates. ALL components were professionally installed by a shop and aligned as well. The shop that installed the stuff is also being cool and working with me to get this fixed. So to what I know or have been told - SPC said their arms are taller than stock so they can be adjustable and maybe bump stops on my shocks or even stiffer springs . Ok so stiffer springs equal stiffer ride, not what I want thats why I went with a street coilover instead of a racing coilover and budget of course Now to bump stop, ok I could see this working but a band aid fix if you ask me and would loose out on travel of shock along with would still get a thud type sound as shock hit bump stops(right?) So the questions I have are: 1 - Do SPL arms clear better, from what I read , because they are not as 'tall' (have not read nearly the amount of posts on clunking with SPL v SPC)? 2 - Do SPL arms clunk at all, because I dont want to spend time and money on something that could be a similar problem. So if you have SPL A arm with BC coilovers I would appreciate your wisdom. If you have SPL A arms with other coilovers your input will help but keep in mind different spring rates will make a difference.

http://i929.photobucket.com/albums/a...nster/Hit1.jpg
http://i929.photobucket.com/albums/a...nster/hit2.jpg
http://i929.photobucket.com/albums/a...nster/mark.jpg


***FIXED**** went to SPL arms after many hours of spent time and more money wasted. Sad to say but SPC on at least my car would not travel correctly in the fender space given with the way SPC designs the Arm(wider and taller than stock). I talked to them and their engineers about this and even had a moment of hope when they redesigned the arm, but after talking to them and showing them pictures they said I would have the same problem. Now that I am on SPL not a single clunk and my car rides smooth as silk on BC coilovers

 

Welcome to the world of aftermarket A-Arms. Your coilovers are not to blame. Your A-Arms are going to travel regardless of your spring rates.

 

Well first off, your drop is one problem....

1.5" front and 1" rear?? you are nose diving the car thus adding too much weight to the front, so your hitting unknowingly with that set up..

Your car should be set up with the .967 ratio as shown here front to rear: 26.89/27.80 = .967

READ HERE - https://my350z.com/forum/8293471-post9.html

First set that correctly then take it for a test drive, from there i have other options for you...
-J

 

half the peeps that have this issue are either slammed redicuoulsly low or are doing the same incorrect drop as the OP.........

the A-arms are hardly the issue......as that upper end of the suspension travel range is not needed really........

-J

 

oopppssss ...the other way around on 1.5" in back and 1" in front ) these are approximate as the shop did it so I can only do a measure and compare at this point, but currently have stock on front so will measure to try...odd though so from your description would that mean most that have the clunk problem with SPC so much would also have the problem with SPL without changing the height. I know Im not slammed....shop first comments was you arent even close to what others do as far as drop, so I know this is should not be the problem. The front could be too low compared to back so I will check the link. If it is, what do you think would have less negative impact if any - lowering the back more for the correct ratio or raising the front?

 

Wow, your second post about the same problem.

 

not very much info and answers in first one and also confirmed with pictures part of the problem on here.....Better title

 

SPL, SPC, etc....any one will make contact if the height of the car is not set up correctly.....Doesn't matter which way you go with front or back, just get to the drop you want with the same ratio........... so long as you get the ratio front to back correct on your car.

I would start there - Fix the height issue and test.

Next,
would be to ensure that the spring pre-load on all the coilovers is the same. AS IN, the adjustment ring at the bottom of each coilover is at the same dimension left to right and that they are not loose, should be at least 2 turns once resistance is felt, then locked into place.

odds, are thats fine and its only your height, so once again, get a yard stick, stop in an empty parking lot and measure at the fenders and note them down.

-J

 

Yeah coilovers were first thing I checked because BC Racing said some customer have adjusted their coilover incorrectly from the spring perch for ride height adjustment so we should be good there. Plus they have the front coilovers right now and hopefully will be setting them correctly again as I asked them to and the spring load had been released to do a push test for response per them.

Will do the height adjustment check in a week or so when I get them back and install the fronts back on and let you know. Hopefully this is it, looking for possibilities and fixes rather than Band Aid fixes that were suggested by others, so your help is appreciated Jason.

 

^ my car is lowered 1.5 inches both front and rear and sits at .966 ratio.

I hit drift events and autoX events....gone over hwy bumps, uneven pavement,etc and dont hit with my Ksport coilovers.

im purdy sure the height issue is whats up...

-J

 

One more question at this point, so my car is the Grand Touring model and I found the FSM for it and looked at the height adjustment. Did the calculation with it coming out to .971 Is that correct and how close should I be, example would .966 be too far or is the margin some what flexible

 

^ Get as close are your comfortable with it for your car.....me, im more of a spot on kinda guy, so I would aim for as close as possible, but thats up to you.

I would say 10% as a min/max would suffice...........

-J

 

SPC A-arm is the problem. I've bought a SPC A-arm for my brother's G35. The right side clunks like hell and the car is not dropped.
Spent toooo much for this arm..

 

Yeah that was my first impression also but Jason has a lot of experience with various suspension items so I'm going to try his suggestion first as it wont cost me anything additional. Also BC Racing was really cool and basically rebuilt the shocks and included stiffer spring sets (12/10) for a great price (with the ability to return them if I don't use them). Should hopefully get the shocks back next week to try and get this fixed. I'm pretty much in the process of elimination. Hopefully I wont get to SPC A Arms being it and have to replace them with something else to get rid of clunk. Still don't like their response of using bump stops because they are taller than stock for adjustability

 

^ the SPC's are taller yes, but that still shouldn't be an issue with the correct ratio drop and proper coilover spring perch preload, equal dampening side to side, etc..

-J

 

What's his suggestion?

 

Jasonz, uh.....read the above posts.

 

see post #3, followed by post 8

-J

 

I'm having the same issue and I also have SPC.. So I need to check me pre load, and raise up the front a little?

 

holy crap man......okay not to spoon feed or anything anymore but start by reading post 3, then post 8..............
and if you still don't get it, then do the instructions on post 18.

-J