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Differences in Front Suspension 2009-2014

- - - - - suspension differences

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#41
HiBoost

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I haven't read the links posted so this may have been mentioned, but we are doing a lot of suspension R&D here for some shocks in the works and we've realized that the motion ratio of the front suspension is different on the older ones. I can only assume CBA and DBA is where the change happened, but hard to say yet. On the 09, the front lower shock mount is about 1" further inward than on a 2013.


That's very interesting. So it would seem that the older shocks would not have as much travel as the newer shocks, and therefore one might wonder if the new shocks running in the old locations would actually work as designed. Even the zero point (don't know the actual term) where the 13 shock sits under weight but standing still would be different when installed on an 09, no? Seems like it would have to be more compressed to fit that further inward mount. Are the OE springs progressive or linear?
-Jeff

#42
Tony1

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Yeah, the newer cars will use more shock travel.  I don't know if they changed the travel with the new shocks, but the theory is right about travel. 

 

Not sure on the OE springs, Paul just bought a spring tester to be able to test the stock spring and bump stop together, since that's how it's used stock. 


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#43
7racer

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Tony, thanks for the great info!


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#44
descartesfool

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Nissan announced the changes to the suspension in terms of damper position mounting point that went along with damper changes, plus caster alignment and likely camber curve changes. It was known that to change up to the newer suspension required changing dampers, springs and at least the lower A-arms, since they are all tuned as a system. So motion ratio change was one of their intentions. They also discovered when running with a fully instrumented car in a 24 hour race at the Ring that the roll-centre movement in reality was different from what they had assumed in their CAD models, and they said they would make changes to fix that as well. Mizuno and others described that in a video about the cars they ran in the race, where they talked about a $1 circlip failure in the axle as I recall. In the latest 2015 car, they said they were also changing the stiffness of the suspension bushings to make the car more compliant and softer over bumps. So lots of little refinement changes.


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#45
NJNYCGTR

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Nissan announced the changes to the suspension in terms of damper position mounting point that went along with damper changes, plus caster alignment and likely camber curve changes. It was known that to change up to the newer suspension required changing dampers, springs and at least the lower A-arms, since they are all tuned as a system. So motion ratio change was one of their intentions. They also discovered when running with a fully instrumented car in a 24 hour race at the Ring that the roll-centre movement in reality was different from what they had assumed in their CAD models, and they said they would make changes to fix that as well. Mizuno and others described that in a video about the cars they ran in the race, where they talked about a $1 circlip failure in the axle as I recall. In the latest 2015 car, they said they were also changing the stiffness of the suspension bushings to make the car more compliant and softer over bumps. So lots of little refinement changes.


Wasnt the change for the 2015 suspension bushings for the premium only for a smoother on road ride?

#46
descartesfool

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Wasnt the change for the 2015 suspension bushings for the premium only for a smoother on road ride?

 

Here is what Car & Driver wrote: "Here’s what’s different for the non-NISMO car: The suspension gets new spring rates, revalved shocks, a softer, hollow 34-mm front anti-roll bar, and bushings that are softer in the vertical plane. New tires—measuring 255/40-20 up front and 285/35-20 at the rear, and still branded as Dunlop SP Sport Maxx GT 600 DSST CTTs—have stiffer sidewalls and are said to be not so much softer as more compliant." http://www.caranddri...st-drive-review

 

and a little more info here: http://www.autoblog....st-drive-video/

"In the standard car, much of the work was done on the suspension, the aim being to better balance the apportionment of load between the four wheels. It was given a longer stroke and a new front stabilizer, spring rates were adjusted, bushes were revised and the electronics controlling the shock absorber valves were recalibrated. The primary result of that was more grip, the secondary – and maturing – result was a smoother ride that didn't need antsy hands on the steering wheel in order to keep a straight line.  new steering pump was installed that eased the force required for low-speed maneuvering. Braking gets a more linear response and better modulation. Body stiffness in the rear is increased through better manufacturing processes and even more accurate fitting. The 20-inch Dunlop Sport Maxx GT DSST CTT tires have a new compound, stiffer sidewall and a stepped tread block to cut down on road noise....its body has been stiffened through the use of additional adhesives on the bodyshell around the door and backlight openings." 



#47
shawnhayes

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Figure I should get the DBA lower control arms to take advantage of the 2013 suspension I have now.

Shawn

#48
icarus

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Remember that Mizuno's successor calls the 2015 GT-R a "gentleman's car" and seemingly all the Ring development efforts were spent on the Nismo. So if you read between the lines, maybe they made the 2015 suspension softer without regards to performance, or timed Ring testing.
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#49
shawnhayes

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Remember that Mizuno's successor calls the 2015 GT-R a "gentleman's car" and seemingly all the Ring development efforts were spent on the Nismo. So if you read between the lines, maybe they made the 2015 suspension softer without regards to performance, or timed Ring testing.


A good point. I will be aiming to find a used 2013 lower set of arms.

Or new 2013 arms if I have to.

Shawn

#50
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From their website it appears that Litchfield only offers 1 kit for all years of GTR and I don't see any mention of them replacing the lower control arms.  This would seem to suggest that both lower mount locations work ok with their springs and dampers... so perhaps we're exaggerating the impact of the updated arms and you can get by fine with yours Shawn?


-Jeff

#51
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From their website it appears that Litchfield only offers 1 kit for all years of GTR and I don't see any mention of them replacing the lower control arms.  This would seem to suggest that both lower mount locations work ok with their springs and dampers... so perhaps we're exaggerating the impact of the updated arms and you can get by fine with yours Shawn?

 

I've thought about that as well.  Yes, the Litchfield only has one, and all the coilover sellers only sell one as well.  That being said, a 1" movement of a lower shock mount changes things "just a little" - but maybe "just enough".  I've thought about doing the install with the old control arms first, and then if it wasn't fully satisfied then trying the newer lower control arms.

 

Lots of good thoughts in this thread.   It still amazes me of HOW MANY small changes Nissan has made over the years.

 

Shawn



#52
7racer

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I've thought about that as well. Yes, the Litchfield only has one, and all the coilover sellers only sell one as well. That being said, a 1" movement of a lower shock mount changes things "just a little" - but maybe "just enough". I've thought about doing the install with the old control arms first, and then if it wasn't fully satisfied then trying the newer lower control arms.

Lots of good thoughts in this thread. It still amazes me of HOW MANY small changes Nissan has made over the years.

Shawn


Might be overly expensive. But what about the new lit field lower tubular arms?

In7anity!!


#53
shawnhayes

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Might be overly expensive. But what about the new lit field lower tubular arms?

 

Too much experience with overly ambitious aftermarket parts.  My experience with OEM parts (especially later model upgrade parts) has been less,,,,uh....."interesting"

 

I've spent a lot of money over the years that later turned out a little sour.

 

If the OEM DBA suspension doesn't perform well on a CBA, adding about $1400 in lower OEM control arms doesn't seem too out of line.  It could be, but we'll see.

 

Thanks for your suggestion though.   It's a nice thought.

 

Shawn



#54
elf_cruiser

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Changing the motion ratio will have a noticeable effect for sure, the closer to 1:1 you can get, the better everything works. The related change in angle of the upper strut mount is inconsequential.

Motion ratio adjustments are one of the nice benefits of inboard cantilever suspensions. You can very easily change that ratio, and many race cars go beyond 1:1 so that the dampers and springs can place even more leverage on the tire than is possible with a standard strut design.
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#55
icarus

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From their website it appears that Litchfield only offers 1 kit for all years of GTR and I don't see any mention of them replacing the lower control arms. This would seem to suggest that both lower mount locations work ok with their springs and dampers... so perhaps we're exaggerating the impact of the updated arms and you can get by fine with yours Shawn?


It may make little or no difference. As far as I know, all the aftermarket suspension offerings are a "universal" fit between CBA and DBA. Unfortunately, because they likely can't justify the R&D of producing a separate offering.

But, Nissan made revisions to the shocks and springs along with the geometry changes, and they have hundreds of Ring laps and years of intensive and detailed data acquisition/analysis to support their changes. And last but not least an improvement of 20 sec per lap at the Ring between 2008 and 2014 model years.
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#56
icarus

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It still amazes me of HOW MANY small changes Nissan has made over the years.
Shawn


It was Mizuno's vision for constant improvement of the R35. Upon the introduction in 2007, he stated it was only the beginning, and his team's goal was to never be satisfied, to always be reaching higher.

I can think of no other road car ever produced where every year the design team went back to the Ring for testing and improvement. In that way the R35 is truly special and follows a racecar platform approach, making it faster and better every year.
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#57
shawnhayes

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Well well. Quite the discussion we have here, but in my own personal interests, I need a vote:

1. Just try the DBA shocks and shut up, man.
2. Buy DBA lower control arms from the get go to "match" the later cars.
3. Source a whole front DBA clip with ALL the suspension pieces to make sure all variations have been covered (I'm not likely to try this - too much money for too little gain, but I wanted to see how many of you might even consider it)

Shawn

Edited by shawnhayes, 26 April 2014 - 05:19 PM.


#58
descartesfool

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A motion ratio change has a huge effect on the suspension wheel rate, which is all you care about, as the wheel rate is what the car's tires actually see, and not the spring rate. That is the effective spring force that the tire sees as it is translated from the spring to the tire by the suspension geometry. The spring is compressed as the wheel moves up by a lesser ratio called the motion ratio. If the motion ratio is 0.8 in one case, then if the wheel moves up 1", the spring compresses by only 0.8" which is how the motion ratio is defined: measure spring and wheel displacement and divide one distance by the other. But since spring rate is in lbs per inch, it means that the force at the spring is 0.8" times the spring rate, which we might assume is 1000 lb/in for an example. Thus moving the spring by 0.8" x 1000 lb/in gives a force at the spring of 800 lbs. The force at the wheel is reduced by the motion ratio, so it is 0.8 x 800 lbs or 640 lbs. The wheel rate is thus 640 lbs/in, which is the spring rate if 1000 lbs/in x motion ratio squared. Motion ratio is super important because the force at the wheel is dependant on the motion ratio squared.

 

Now make a geometry change in the lower arm which changes the motion ratio to 0.7 for example. Assuming the spring is the same at 1000 lbs/in, the new wheel rate is 1000 x 0.7^2 = 490 lbs/in compared to 640 lbs/in before. That is a very, very large reduction in % terms as the wheel rate has gone down by 150 lbs/in or 150/640 x 100% = 23%. That is a lot! It is like changing your springs from 1000 lbs/in down to 770 lbs/in.

 

So if you use springs and dampers tuned for a 0.8 motion ratio, they will not be correct (not even remotely) for a 0.7 motion ratio suspension.

 

Now I just used some random numbers as an example, as I don't know the GT-R's CBA and DBA motion ratio values, but if I was changing dampers and springs from CBA to DBA values, I would absolutely change the control arms to get the motion ratio those components were designed for. 


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#59
ian.r

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agreed. however i think it would be good to get some stuff from Tudor and or the hawk gtr... specially that rear suspension they were talking about on life.

#60
elf_cruiser

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Descartes for the win with the explanation!!
Now I'll boil it down to a few words - the dba lower arms will make whatever springs you have feel firmer than the cba lower arms.

Shawn - I would try #1, and be prepared to find that maybe everything is too soft, and then try #2.

Are you sure that the dba arms will fit the rest of the cba chassis? Mount points, sway bar, anything else???

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