Choosing the right coilovers
03-21-2016, 04:32 PM
#18
Ok after a few more calls, I'm now considering a set of BC Racing coil-overs. I've read a few reviews on other boards including this one which really breaks down some of my own concerns:
http://www.nsxprime.com/forum/showth...hensive-Review
Also read a thread on the STi forum where they specifically addressed wheel frequency and his setup was quite high. Had dyne plots for his shocks as well and it's worth noting this was more than a few years back and they may have made improvements.
Suspension/Stiffening BC Racing ER series coilover comprehensive review! - Subaru Impreza WRX STI Forums: IWSTI.com
One of the issues brought up in the Sti thread dealt with discrepancy in damping between shocks left and right as well as using the same shock design for the front and rear of the car. BC North America says they now test the shocks on a dyno and match the valving to the spring rate.
I'm also considering higher spring rates, 14K front/12K rear although I may chicken out and stick with a 12/10 setup. Need a few more questions answered and I'll update shortly.
I did read one review on this forum where the BC Racing BR shocks lasted 40K miles before issues developed after switching to Swift springs. That's actually good for a high performance shock which was street and track driven. Stance recommends a 60K interval for street only, 40K for mostly street and some track. Hell, every OEM shock I've ever experienced starts to fall off at 40K. So doesn't seem like such an issue to me. More to come.
http://www.nsxprime.com/forum/showth...hensive-Review
Also read a thread on the STi forum where they specifically addressed wheel frequency and his setup was quite high. Had dyne plots for his shocks as well and it's worth noting this was more than a few years back and they may have made improvements.
Suspension/Stiffening BC Racing ER series coilover comprehensive review! - Subaru Impreza WRX STI Forums: IWSTI.com
One of the issues brought up in the Sti thread dealt with discrepancy in damping between shocks left and right as well as using the same shock design for the front and rear of the car. BC North America says they now test the shocks on a dyno and match the valving to the spring rate.
I'm also considering higher spring rates, 14K front/12K rear although I may chicken out and stick with a 12/10 setup. Need a few more questions answered and I'll update shortly.
I did read one review on this forum where the BC Racing BR shocks lasted 40K miles before issues developed after switching to Swift springs. That's actually good for a high performance shock which was street and track driven. Stance recommends a 60K interval for street only, 40K for mostly street and some track. Hell, every OEM shock I've ever experienced starts to fall off at 40K. So doesn't seem like such an issue to me. More to come.
03-21-2016, 10:14 PM
#20
slartibartfast, looked up the Fat Cat website and I've started reading/watching the videos. I somehow missed they were an actual company producing suspension systems. Doesn't look like they had any specific applications for the G37 Coupe and no experience with the 370Z. Which is pretty much on par with every other shock manufacturer, LOL. It sounds like they could do something for me but I'd need to know a lot of specs that I currently have no hard numbers for (like IPL sway bar rate for starters).
So to figure out frequency, it's 3.13*sqrt(wheel rate/sprung weight). So one needs to figure out the sprung rate for the front and rear wheel plus the wheel rate (motion rate?) and would thus need scales.
And much of this is affected by a whole lot of variables including wheel width, offset, spacers, spring location, whether or not you have a spare in the rear, overall weight of the vehicle etc...I could switch wheels or spacer width and it would change all sorts of data.
And in the end, knowing the frequency, what's it really telling us? Is it a predictor for how the car will ride? How is it helpful? From my limited understanding, it correlates directly to the potential for grip.
A simple explanation from a quick google search...The spring frequency is the natural frequency of the suspension - if the car was to bounce up and down on it's springs unrestrained by the shocks, it's a measure of how many cycles would it go through in one second (Hz) - or in one minute (cycles per minute, CPM).
The spring frequency is a function of the sprung weight acting at the wheel, and the vertical stiffness, wheel rate or effective stiffness acting at the wheel.
I do know from reading that a true coil over retains much of it's spring rate at the wheel while the OEM location is a fraction of it's listed rate. I sort of relate to this in terms of a nut cracker. The further away you move the nut from the nutcracker's pivot, the harder it is to crack the nut (more force needed to achieve the same results).
So generally speaking a heavier car will require a higher spring rate to achieve the same frequency of a lighter car. To me, this is why I pause when I see the spring rates on a G37 coil over setup being offer with the same rate for the lighter 370Z. They won't perform the same. And how does that extra 12" of wheelbase affect the optimal ratio between front and rear wheel spring rates (or ultimately frequency)?
The end goal of the entire suspension system is to keep the wheel in contact with the road. The springs are the main structure and force which accomplishes this task. The shock controls the spring's osciliation or frequency but not it's force rate/distance. So as the frequency goes up, and grip goes up, so will the necessary spring rate needed to achieve that frequency. And the needed rate changes based on where the spring is positioned in relation to the wheel and the suspension pivot point.
So I'm guessing with an OEM-style tire there's a point where the wheel frequency can surpass the inherent grip of the tire. You move up to an R-spec and you can take advantage of the increase in frequency.
Again I've got to somehow relate all of this (within reasonable limits) to my own suspension choice for a daily-driven vehicle. And while I should be able to figure out a decent spring rate, it doesn't help with the damper end of things. I really wish I had a quality performance shop in town that also dealt with suspension. They'll all make your car go fast but fail to make it turn more effectively.
So to figure out frequency, it's 3.13*sqrt(wheel rate/sprung weight). So one needs to figure out the sprung rate for the front and rear wheel plus the wheel rate (motion rate?) and would thus need scales.
And much of this is affected by a whole lot of variables including wheel width, offset, spacers, spring location, whether or not you have a spare in the rear, overall weight of the vehicle etc...I could switch wheels or spacer width and it would change all sorts of data.
And in the end, knowing the frequency, what's it really telling us? Is it a predictor for how the car will ride? How is it helpful? From my limited understanding, it correlates directly to the potential for grip.
A simple explanation from a quick google search...The spring frequency is the natural frequency of the suspension - if the car was to bounce up and down on it's springs unrestrained by the shocks, it's a measure of how many cycles would it go through in one second (Hz) - or in one minute (cycles per minute, CPM).
The spring frequency is a function of the sprung weight acting at the wheel, and the vertical stiffness, wheel rate or effective stiffness acting at the wheel.
I do know from reading that a true coil over retains much of it's spring rate at the wheel while the OEM location is a fraction of it's listed rate. I sort of relate to this in terms of a nut cracker. The further away you move the nut from the nutcracker's pivot, the harder it is to crack the nut (more force needed to achieve the same results).
So generally speaking a heavier car will require a higher spring rate to achieve the same frequency of a lighter car. To me, this is why I pause when I see the spring rates on a G37 coil over setup being offer with the same rate for the lighter 370Z. They won't perform the same. And how does that extra 12" of wheelbase affect the optimal ratio between front and rear wheel spring rates (or ultimately frequency)?
The end goal of the entire suspension system is to keep the wheel in contact with the road. The springs are the main structure and force which accomplishes this task. The shock controls the spring's osciliation or frequency but not it's force rate/distance. So as the frequency goes up, and grip goes up, so will the necessary spring rate needed to achieve that frequency. And the needed rate changes based on where the spring is positioned in relation to the wheel and the suspension pivot point.
So I'm guessing with an OEM-style tire there's a point where the wheel frequency can surpass the inherent grip of the tire. You move up to an R-spec and you can take advantage of the increase in frequency.
Again I've got to somehow relate all of this (within reasonable limits) to my own suspension choice for a daily-driven vehicle. And while I should be able to figure out a decent spring rate, it doesn't help with the damper end of things. I really wish I had a quality performance shop in town that also dealt with suspension. They'll all make your car go fast but fail to make it turn more effectively.
03-22-2016, 11:40 AM
#21
I'm going to list the questions I personally would want answered before purchasing a set of coil overs for mostly street duty. Your questions may differ due to different priorities. I'd also comment these questions should be asked of the manufacturer or the supporting facility which may be buidling/valving these here in the states, not by a vendor who (no offense meant) is a sales person who probably doesn't have first hand experience with your particular car brand/model. There are most definitely exceptions but I am speaking from a generalized point of view as there aren't any specialty shops for G37's...also if anyone wants to add to the list, feel free! If there's something I'm not thinking of please add your thoughts or counterpoints.
-Are your shocks TUV approved?
-Is the manufacturing facility ISO certified and if so, what's the certification?
-Was there first hand development with a G37 on the track, autocross or via spirited street driving?
-Is the rear spring/shock setup a true coil-over or does it retain the OEM spring location? -If it's a true-type, is there an option to use the OEM spring location?
-What is the MINIMUM drop for the setup? Can it achieve OEM height?
-Is it a twin tube or a mono tube?
-What's the piston and shock body diameter?
-Is it a linear or digressive piston design?
-What material is the shock body made of? Steel? Aluminum?
-How about the coatings...are they durable anodization coatings on the threaded portions and powder coated on the other parts? Or is it just paint?
-Is there an option for Swift, Hyperco or Ohlins springs direct from you?
-Do you match the shocks left to right in damping specs? Do you provide a shock dyno for each shock? Are the front/rear shocks exactly the same or are they specific to the location? (Talking about the shock itself, not the mounting brackets, top mount, etc...)
-Do the shocks come with spring isolators top/bottom whether they're the original springs or an upgraded spring like swift?
-If you're recommending a spring rate, is that based on first-hand experience?
-Why are the rates exactly the same as the 370? (if applicable)
-Are the springs linear or progressive?
-If you recommend rates and they're not satisfactory (either too harsh, bad handling, etc) can they be swapped out for a different rate for a minimal fee?
-What's the warranty on the entire kit?
-What is the rebuild interval based on usage? (All street, mostly street, some track, 50/50, mostly track, all track)
-Do you match the shocks left to right in damping specs? Do you provide a shock dyno for each shock?
-What type of upper mounts do the shocks have?
-What type of seal material is used? Are they a name brand?
-Can the shocks be easily adjusted without removal? Are the adjustment ***** easily accessible? Are extenders for the rear shocks offered?
-Are the shocks ready to go out of the box with the recommended ride height and spring preload set? Is there anything else needed for installation?
-Do they come with instructions in my native language?
-What is the replacement cost for just the shock itself? How about a rebuild fee? What's the turn around for a rebuild?
-Can they be serviced in my home country?
-Can I order with custom spring rates and matched valving? If so, what's the cost?
Much of this information can be found on websites for the individual manufacturers. Not all though so you'll have to be diligent. I tend to avoid companies that have zero information on their site like D2. Have to say, BC's site isn't that great either. Stance is pretty good, any of the high end stuff is exceptional but you're often dealing with an individual dealer who specializes in suspension. But even companies like Bilstein or KW don't offer all the specs. They should.
-Are your shocks TUV approved?
-Is the manufacturing facility ISO certified and if so, what's the certification?
-Was there first hand development with a G37 on the track, autocross or via spirited street driving?
-Is the rear spring/shock setup a true coil-over or does it retain the OEM spring location? -If it's a true-type, is there an option to use the OEM spring location?
-What is the MINIMUM drop for the setup? Can it achieve OEM height?
-Is it a twin tube or a mono tube?
-What's the piston and shock body diameter?
-Is it a linear or digressive piston design?
-What material is the shock body made of? Steel? Aluminum?
-How about the coatings...are they durable anodization coatings on the threaded portions and powder coated on the other parts? Or is it just paint?
-Is there an option for Swift, Hyperco or Ohlins springs direct from you?
-Do you match the shocks left to right in damping specs? Do you provide a shock dyno for each shock? Are the front/rear shocks exactly the same or are they specific to the location? (Talking about the shock itself, not the mounting brackets, top mount, etc...)
-Do the shocks come with spring isolators top/bottom whether they're the original springs or an upgraded spring like swift?
-If you're recommending a spring rate, is that based on first-hand experience?
-Why are the rates exactly the same as the 370? (if applicable)
-Are the springs linear or progressive?
-If you recommend rates and they're not satisfactory (either too harsh, bad handling, etc) can they be swapped out for a different rate for a minimal fee?
-What's the warranty on the entire kit?
-What is the rebuild interval based on usage? (All street, mostly street, some track, 50/50, mostly track, all track)
-Do you match the shocks left to right in damping specs? Do you provide a shock dyno for each shock?
-What type of upper mounts do the shocks have?
-What type of seal material is used? Are they a name brand?
-Can the shocks be easily adjusted without removal? Are the adjustment ***** easily accessible? Are extenders for the rear shocks offered?
-Are the shocks ready to go out of the box with the recommended ride height and spring preload set? Is there anything else needed for installation?
-Do they come with instructions in my native language?
-What is the replacement cost for just the shock itself? How about a rebuild fee? What's the turn around for a rebuild?
-Can they be serviced in my home country?
-Can I order with custom spring rates and matched valving? If so, what's the cost?
Much of this information can be found on websites for the individual manufacturers. Not all though so you'll have to be diligent. I tend to avoid companies that have zero information on their site like D2. Have to say, BC's site isn't that great either. Stance is pretty good, any of the high end stuff is exceptional but you're often dealing with an individual dealer who specializes in suspension. But even companies like Bilstein or KW don't offer all the specs. They should.
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blnewt (03-22-2016)
03-22-2016, 11:42 AM
#22
I found the thread! This is a 350Z related discussion about OEM rear spring location vs. true-type coil-over shocks in the rear.
True Coilover Rear Damper Or Not - MY350Z.COM Forums
True Coilover Rear Damper Or Not - MY350Z.COM Forums
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Nico-derm (04-05-2016)
03-23-2016, 11:40 PM
#23
Ok I sent BC an email to get answers I didn't already know about their product. This is a direct copy/paste of the response, I've not added a thing.
Thank you for contacting us.
We do have a specific kit for the G37 with different spring rates and valving. The part number is V-02 and it is different than the 370Z setup.
The spring rates are 12Kg front (674lbs) and 10Kg rear (564lbs).
Our coilovers do carry a TUV certificate and are sold regularly overseas including Europe.
The Company does also have ISO certification for ISO9001.
To answer your questions in the format they were sent over:
The G37 chassis is one that we have extensive development time on in both street and real world track situations both amateur and professional.
Minimum drop for the kit will be 1.2 inches front and rear and the will not unfortunately go as high as OEM. This is also the ride height it comes preset out of the both with.
The shock bodies are 53mm with piston shaft sizes of 12.5mm front and rear.
All of our kits are currently a linear piston design with only the DR's running the new digressive design. We are currently working on implementing the DR piston across the range we offer.
The main advantage of a digressive piston is its reaction time. Lower down in the dampening curve it reacts to force input much quicker than a linear piston. This means it has better bump absorption overall and allows the chassis to react in a more predictable manner.
All of our kits feature spring seat isolators on all springs front and rear. We always ensure the most quiet ride possible.
Rebuild will be determined by usage as you stated. Normal usage can easily result in 70-80k miles without issue. Heavy track use will decrease overall life.
The kit default has rubber top plates to again ensure noise free operation, pillowball top plates are available as an option.
Our piston shaft seals are a reinforced rubber. It is our own proprietary design and not an off the shelf piece.
The kit is ready to go out of the box and all OEM mounting tabs are retained to make it a 100% bolt on installation. Rear camber arms are suggested if you plan to lower more than 2 inches for alignment purposes.
A bare shock cartridge replacement is 95.00 plus shipping. We provide a brand new shock body for that price to the customer to aid with vehicle downtime rather than offering rebuilds.
END QUOTE.
So...pretty impressed they were thorough with their answers. I've sent a reply to find out how soon the digressive piston will be available. If it's soon, I may hold off for that version. I didn't get an answer about shock dyno charts but it's good to know these are valved differently from the 370Z.
Thank you for contacting us.
We do have a specific kit for the G37 with different spring rates and valving. The part number is V-02 and it is different than the 370Z setup.
The spring rates are 12Kg front (674lbs) and 10Kg rear (564lbs).
Our coilovers do carry a TUV certificate and are sold regularly overseas including Europe.
The Company does also have ISO certification for ISO9001.
To answer your questions in the format they were sent over:
The G37 chassis is one that we have extensive development time on in both street and real world track situations both amateur and professional.
Minimum drop for the kit will be 1.2 inches front and rear and the will not unfortunately go as high as OEM. This is also the ride height it comes preset out of the both with.
The shock bodies are 53mm with piston shaft sizes of 12.5mm front and rear.
All of our kits are currently a linear piston design with only the DR's running the new digressive design. We are currently working on implementing the DR piston across the range we offer.
The main advantage of a digressive piston is its reaction time. Lower down in the dampening curve it reacts to force input much quicker than a linear piston. This means it has better bump absorption overall and allows the chassis to react in a more predictable manner.
All of our kits feature spring seat isolators on all springs front and rear. We always ensure the most quiet ride possible.
Rebuild will be determined by usage as you stated. Normal usage can easily result in 70-80k miles without issue. Heavy track use will decrease overall life.
The kit default has rubber top plates to again ensure noise free operation, pillowball top plates are available as an option.
Our piston shaft seals are a reinforced rubber. It is our own proprietary design and not an off the shelf piece.
The kit is ready to go out of the box and all OEM mounting tabs are retained to make it a 100% bolt on installation. Rear camber arms are suggested if you plan to lower more than 2 inches for alignment purposes.
A bare shock cartridge replacement is 95.00 plus shipping. We provide a brand new shock body for that price to the customer to aid with vehicle downtime rather than offering rebuilds.
END QUOTE.
So...pretty impressed they were thorough with their answers. I've sent a reply to find out how soon the digressive piston will be available. If it's soon, I may hold off for that version. I didn't get an answer about shock dyno charts but it's good to know these are valved differently from the 370Z.
The following users liked this post:
blnewt (03-25-2016)
03-23-2016, 11:45 PM
#24
Link to a suspension worksheet.
http://www.truechoicekoniracingservi.../worksheet.pdf
What I may do is start compiling the same data for each make/model shock I research (based on questions above) and paste that in my first post.
http://www.truechoicekoniracingservi.../worksheet.pdf
What I may do is start compiling the same data for each make/model shock I research (based on questions above) and paste that in my first post.
03-24-2016, 01:48 PM
#25
I called BC sales this morning and the DR series is available with a, best case, 4-week lead time. I'd double that to be uber conservative. The cost is $250 above the cost of the BC series kit.
The ZR series uses a digressive piston already and it's three way adjustable with the EC using a standard linear piston.
The ZR series uses a digressive piston already and it's three way adjustable with the EC using a standard linear piston.
03-24-2016, 06:27 PM
#26
Wheel frequency determines ride characteristics. It is dependent upon motion ratio AND spring rate which can vary dramatically so can't by itself give an indication of ride characteristics. A lot more goes into wheel frequency that what you list. It includes stabilizer bar rates, wheel weight*, car weight* and other suspension components, etc.
Shaikh address wheelbase with his flat ride concept. He briefly mentions a Rolls Royce suspension engineer named Ollie. This is the guy who determined back in the Twenties that front/rear wheel frequency ratio of 1 leads to a hobby horse ride. I note this in my RWD Sedan coilover sticky. Miatas come stock with front frequency about 10% higher than rear. Looking at the G coupe stock spring rates, it appears Infiniti is shooting for the rear to be a tad bit higher than the front, very much in line with the flat ride concept.
I spent an hour Googling several years ago this Ollie fellow and found just one document. I don't know if I could find it again. Maybe if someone is an SAE fellow and has access to their technical library...
Great thread on 350Z.com! Makes the "lazy" aftermarket guys seem prescient. I'm wary of their damping decisions but I'm backing away from my personal desire for a true coil-over in the rear. I have no desire to reinforce the rear shock tower.
For those reading who don't want to negotiate the deep subject on the Z board, shock tower metal thickness is suspect as is hub-arm bushing strength when using true coil-over rear. There were other factors listed but they seem small in comparison to these two.
Make sure to watch all the Fat Cat videos regarding damping curves and dynoed shocks. While he doesn't list much for Nissan, in one of his videos I spied a dyno folder for the Bilstein PSS10 for the G35, so he's not completely clueless about our cars.
*Basically, sprung/unstrung weights
Shaikh address wheelbase with his flat ride concept. He briefly mentions a Rolls Royce suspension engineer named Ollie. This is the guy who determined back in the Twenties that front/rear wheel frequency ratio of 1 leads to a hobby horse ride. I note this in my RWD Sedan coilover sticky. Miatas come stock with front frequency about 10% higher than rear. Looking at the G coupe stock spring rates, it appears Infiniti is shooting for the rear to be a tad bit higher than the front, very much in line with the flat ride concept.
I spent an hour Googling several years ago this Ollie fellow and found just one document. I don't know if I could find it again. Maybe if someone is an SAE fellow and has access to their technical library...
Great thread on 350Z.com! Makes the "lazy" aftermarket guys seem prescient. I'm wary of their damping decisions but I'm backing away from my personal desire for a true coil-over in the rear. I have no desire to reinforce the rear shock tower.
For those reading who don't want to negotiate the deep subject on the Z board, shock tower metal thickness is suspect as is hub-arm bushing strength when using true coil-over rear. There were other factors listed but they seem small in comparison to these two.
Make sure to watch all the Fat Cat videos regarding damping curves and dynoed shocks. While he doesn't list much for Nissan, in one of his videos I spied a dyno folder for the Bilstein PSS10 for the G35, so he's not completely clueless about our cars.
*Basically, sprung/unstrung weights
Last edited by slartibartfast; 03-24-2016 at 06:37 PM.
03-24-2016, 07:08 PM
#27
I have a pretty good handle on wheel frequency now but there's no definitive guide that says not to go above a certain frequency for a street driven vehicle. Ride can be subjective too. And the bump/rebound curves have a dramatic effect on the perceived ride of a vehicle. So frequency alone isn't enough IMO.
I did leave out away bars in my last post but mention them in earlier posts. Interestingly some of the 350/370 guys are upping spring rate and removing the rear sway which makes sense in certain scenarios. I may find it necessary to go with "smaller" bars that have a lower rate if I choose to go up in spring rate.
I may be backing off the BC's now too, taking another look at Stance and reworking a set of KW's. Even exploring some Koni's now.
On another note, I actually scraped my under tray this morning on a slight dip. Stock suspension.
I did leave out away bars in my last post but mention them in earlier posts. Interestingly some of the 350/370 guys are upping spring rate and removing the rear sway which makes sense in certain scenarios. I may find it necessary to go with "smaller" bars that have a lower rate if I choose to go up in spring rate.
I may be backing off the BC's now too, taking another look at Stance and reworking a set of KW's. Even exploring some Koni's now.
On another note, I actually scraped my under tray this morning on a slight dip. Stock suspension.
03-24-2016, 11:19 PM
#28
One of my early posts noted that a wheel frequency of 2 Hz was supercar territory while 3 Hz was F1 and such. I speculated the G Sport is about 1.3 Hz. The sedan suspension is rather soft though the low-speed damping kind of masks it. I bounced the rear of the car the other day and it was roughly 1 Hz though this was with shocks installed and that is not a true value. Nor did I have a stop watch running, just the thousand-and-one counting system. Front is somewhat stiffer but I didn't have a good surface on which to push, unlike the rear bumper.
03-24-2016, 11:57 PM
#29
There are a few Subaru guys running in the 2.3hz range, on the street, and they say it's livable. Again, may just be their tolerance, who knows.....If we ever figure out that the IPL bars are the same as the Nismo bars, we can just use their numbers if someone corner weights their car (minus the front/rear ratio).
