Stuck on Cobb vs Hotchkis Kits...Spring Rates / Shock Valving
YOu forgot the link, i would like to see what is being talked about.
Thread Starter
Registered User
iTrader: (3)
Joined: May 2006
Posts: 300
Likes: 0
From: Less Talk, More WOT | Hou, TX
Originally Posted by idrive_MD
I'm curious where you got the springs rates from? I provided some calculated measurements on driver, but they were solely based on a scientific spring rate equation and at the time I didnt have an OEM spring to compare them to. Also I could not account for the material type so what I provided wasn't completely accurate.
I
I
From your post on G35 driver, I think I know what's going on.
this might clear up some info about the cobb suspension...
yes the sways are made by hotchkis, supposedly the exact same as their newest versions (welded collars). however I have seen some discrepencies from post saying the sway bar rates a smidgen different...I chalk that up to margin of error as they're within a few %'tage of each other.
and as for the springs and the questions regarding which Z-gen the springs were designed for, it was developed from a newer Z, so it should be 15% stiffer f/r compared to the revised suspension on the Z.
I found this from my350z:
"the Hotchkis and Cobb sways are the same thing
the Cobb springs are stiffer than Hotchkis, since Hotchkis was designed around pre 04.5 cars and Cobb was designed on a later model (which have different struts)"
UPDATE 09-02-08
just received mine today, did some quick spring calcs for the info below, please note, the measurements do not take into account the material type, so these are rough estimates at best, make the same measurements with OEM springs for a comparison:
Front
wire diameter = .55-in
mean coil diameter = 3.95-in
free coils = 5
Using this it measures 436-lbs/in
Rear
wire diameter = .60-in
mean coil diameter = 4.465-in
free coils = 4
Using this it measures 535-lbs/in
yes the sways are made by hotchkis, supposedly the exact same as their newest versions (welded collars). however I have seen some discrepencies from post saying the sway bar rates a smidgen different...I chalk that up to margin of error as they're within a few %'tage of each other.
and as for the springs and the questions regarding which Z-gen the springs were designed for, it was developed from a newer Z, so it should be 15% stiffer f/r compared to the revised suspension on the Z.
I found this from my350z:
"the Hotchkis and Cobb sways are the same thing
the Cobb springs are stiffer than Hotchkis, since Hotchkis was designed around pre 04.5 cars and Cobb was designed on a later model (which have different struts)"
UPDATE 09-02-08
just received mine today, did some quick spring calcs for the info below, please note, the measurements do not take into account the material type, so these are rough estimates at best, make the same measurements with OEM springs for a comparison:
Front
wire diameter = .55-in
mean coil diameter = 3.95-in
free coils = 5
Using this it measures 436-lbs/in
Rear
wire diameter = .60-in
mean coil diameter = 4.465-in
free coils = 4
Using this it measures 535-lbs/in
Rear spring outside diameter cannot be correct, in order for the spring to work with the oem upper seat and sit in the lower control arm, it would have to be a larger outside diameter. Which would bring the number closer to the Hotchkis number.
This thread is very interesting. I had the stiffer OEM springs in the rear (04.5) and noticed a significant amount of bounce moving to the weak rate of Hotchkis. Cobb and some Bilsteins might be a great combo for me.
From your post on G35 driver, I think I know what's going on.
Rear spring outside diameter cannot be correct, in order for the spring to work with the oem upper seat and sit in the lower control arm, it would have to be a larger outside diameter. Which would bring the number closer to the Hotchkis number.
Rear spring outside diameter cannot be correct, in order for the spring to work with the oem upper seat and sit in the lower control arm, it would have to be a larger outside diameter. Which would bring the number closer to the Hotchkis number.
glad to know what the true rates are now though.
Registered User
Joined: Nov 2005
Posts: 204
Likes: 0
From: Inland Empire
don't waste your money....all the fitment issues are true.....Cobb tech support even said that they designed them this way....
on the stock spring the bottom tapers to fit the bottom strut perch like a glove.
the cobbs do NOT taper in....they are the same diameter from top to bottom....and you can actually fit an entire finger in between the perch and the spring.
if you want to see what i mean here is a picture.....
getting Cobb to give me any support is a nightmare.....i have been asking for front spring pictures for one business week....and all i got was rear spring pictures sent to me TWICE!!! these guys are NOT stupid...they are playing a game with me on purpose
the slop of the spring that sits on the bottom perch is SO BAD that at 15mph if i hit a slight bump the entire car pulls hard to one side "because of the springs sliding around on the base of the strut!!!!"
seriously i was afraid to drive any faster....they refuse to give me a refund because they were installed!!!!!
this is an American based company....that's what i get for buying American!!!
Don't buy corn on the cobb springs...i think a redneck made them
you can see as plain as day the problem with this picture
since i am desperate for a linear spring and already wasted money on Tanabe gf210's which were junk also
my last resort is the RS*R springs! at the very least they will be better than stock. SIGH
on the stock spring the bottom tapers to fit the bottom strut perch like a glove.
the cobbs do NOT taper in....they are the same diameter from top to bottom....and you can actually fit an entire finger in between the perch and the spring.
if you want to see what i mean here is a picture.....
getting Cobb to give me any support is a nightmare.....i have been asking for front spring pictures for one business week....and all i got was rear spring pictures sent to me TWICE!!! these guys are NOT stupid...they are playing a game with me on purpose
the slop of the spring that sits on the bottom perch is SO BAD that at 15mph if i hit a slight bump the entire car pulls hard to one side "because of the springs sliding around on the base of the strut!!!!"
seriously i was afraid to drive any faster....they refuse to give me a refund because they were installed!!!!!
this is an American based company....that's what i get for buying American!!!
Don't buy corn on the cobb springs...i think a redneck made themyou can see as plain as day the problem with this picture
since i am desperate for a linear spring and already wasted money on Tanabe gf210's which were junk also
my last resort is the RS*R springs! at the very least they will be better than stock. SIGH
Registered User
Joined: Nov 2005
Posts: 204
Likes: 0
From: Inland Empire
by the way...even if someone was stupid enough to install them upside down it would not matter.....the springs are the same diameter from top to bottom.
these springs are going in the trash if i cant get a refund.
since cobb verified i got the right part i would be a fool to try to sell them to someone else...they would just complain about the same problem and want their money back.
these springs are going in the trash if i cant get a refund.
since cobb verified i got the right part i would be a fool to try to sell them to someone else...they would just complain about the same problem and want their money back.
The only reason that I have not gotten the Cobb springs is because of a review on them I read that explained how the bottom of the spring was slightly bigger than the mount causing part of the bottom coil to not seat properly. And the customer uninstalled them because he thought they would be unsafe. Every time I ask this, I never get an answer as to if this is the case with these springs.
although i was skeptical about getting them for the same reason (bottom of spring), i had and have no issues with my set. hope this helps.
Thread Starter
Registered User
iTrader: (3)
Joined: May 2006
Posts: 300
Likes: 0
From: Less Talk, More WOT | Hou, TX
Looks fine to me. I've yet to see someone post hard data that shows there being an actual issue with these. 
Gerry, did you need camber arms after the drop?
im getting impatient with waiting on the road contruction projects on base to end so I may just say F'it and put on my tokico/cobb setup....I'll probably work on it after I move into my new house over the next month or so.
well as stated, I installed my D-Specs and Cobb springs on my G35 a week ago. I've been driving around with them like i normally do and I have had zero issues, noises, knocks etc. I noticed the same thing everyone is complaining about, the springs do not exactly fit snug at the lower spring seat (they seem perfect on top).
The only thing I can suggest is to first, install the spring insulators that are on your stock springs. They're the part that wraps around the lower coils. You can usually buy these new from auto stores as well. Second, before tightening them down, I would make sure they are centered on the seat as it is possible to off-center them which I would think could lead to some unpleasant dynamics.
I used 350Z spec D-Specs anf the Cobb springs are only made for the Z, I'm quite pleased with the drop. I'm not sure yet if I'll do a spring mount mod yet in the rear. I want to get wider wheels and tires before I do anything else.
Also I have these paired up with the Cobb sways, I love the entire package so far. I've had the sways on for a while now and loved them from the beginning. I have always had some rear endlink clunking though.
The only thing I can suggest is to first, install the spring insulators that are on your stock springs. They're the part that wraps around the lower coils. You can usually buy these new from auto stores as well. Second, before tightening them down, I would make sure they are centered on the seat as it is possible to off-center them which I would think could lead to some unpleasant dynamics.
I used 350Z spec D-Specs anf the Cobb springs are only made for the Z, I'm quite pleased with the drop. I'm not sure yet if I'll do a spring mount mod yet in the rear. I want to get wider wheels and tires before I do anything else.
Also I have these paired up with the Cobb sways, I love the entire package so far. I've had the sways on for a while now and loved them from the beginning. I have always had some rear endlink clunking though.
Thread
Thread Starter
Forum
Replies
Last Post
