posted on June 06, 2011 01:43
Suspension & Handling Goodies
by Martin Gonzales & Steve Rockwood
Check out the rest of our Project Infiniti G20 Racecar build here!
Manufacturers of econoboxes – in our case, luxury econoboxes – don’t seem to have racing in mind when designing suspensions. Instead, they tend to focus on ignoble things like making cars ride smoothly and quietly while simultaneously neutering handling dynamics just enough to keep the product liability lawyers at bay, regardless of their drivers’ level of driving ability (or lack thereof). This, unfortunately, ends in a car that is going to wallow like a pig and suffer from snow-plow levels of terminal understeer. What does this mean to you? It means that you are going to annihilate the shoulders of those expensive and fast wearing R-compound tires, not to mention scrape the paint off the door handles, if you show up with OEM springs and dampers on race day. In this article, we will take you through the daunting task of turning our luxury econobox into a luxuriously handling machine.
Dampers are one of the most important parts of a racecar, as they keep racecar appropriate spring rates under control as well as give the race team the ability to fine-tune many behavioral aspects of the car’s handling. Pro race teams pour enormous amounts of time and money into developing dampers with dizzying amounts of adjustability. Luckily for our wallets, the Performance Touring (PT) rules penalize teams who use exotic dampers as a means to even the wildly varying economic playing field (NASA paddocks are filled with rigs ranging from UHauls to custom 18 wheelers).
|The Infiniti G20, also know as the Nissan Primera, has a rich racing history dating back to the inaugural season of the British Touring Car Championship's (BTCC) Super Tourer class.
For our car, we wanted dampers that had seperate adjustments for both compression and rebound, and could handle spring rates ranging between 500-1000 in-lbs. This turned out to be more easily said than done. It seems the only people other than us who race the P10 chassis live in Great Britain and ran in the British Touring Car Championship (BTCC). The dampers used on these cars were far too exotic for us and were installed on suspensions that had little in common with the OEM suspension. As a result, no one makes an off the shelf solution for dampers capable of handling our planned spring rates. In addition, due to our car’s combination of shocks and struts, finding adaptable dampers out of a catalogue proved difficult as well.
|Though the Primera was used for many years in the BTCC, there is a lack of after market "race level" options for nearly every part of the car besides the engine.
Monday, June 06, 2011 11:07 AM
Wow, that is a completely brilliant idea for replacing end links!
Monday, June 06, 2011 12:23 PM
^^^ No locknut on threaded part of new endlinks?
Monday, June 06, 2011 1:45 PM
Nice Martin !
Like mxpop mentioned: I think you should thread in some nuts on the end-links, so that they don't get loose (if you haven't done it already).
Any plans to gusset and beef up the rear subframe?
Ditch the current wheels and get Enkei RPF1 in 15X7. Tire Rack advertise them at 9.5 lbs each (they're slightly heavier than 9.5lbs....more like 10.5lbs). You could knock off almost 3lbs of rotational mass in each corner ! If you do that, you know your brakes will thank you :)
Monday, June 06, 2011 1:56 PM
Great article guys! In the offroading world, sometimes a custom made leaf spring can end up being less than an off the shelf piece but MUCH better suited to your rig. How did this process end up comparing to an off the shelf component dollar-wise and handling/ride let's say to a Sentra equivalent?
MXPOP - I definitely agree. Unless those thread ends are long enough in both spherical ends so that one end couldn't become exposed due to vibrational rotation, then lock washers and nuts would be prudent for sure.
Monday, June 06, 2011 2:11 PM
BTW, I dont think a locknut or even lock washer is needed, just a simple nut to act as a jam nut on both ends so niether end gets to rotate freely. Helps to index/locate spherical bearing orientation as well.
Gawd I love bagging on Kojima over these trivial little BS nit-picks! Too much fun!!!
Cool project! Great creative and unique solutions to racing a non-typical platform. Too much simple bolt-on solutions for typically raced cars get all the press, nice to see something out of the ordinary ;-)
Monday, June 06, 2011 2:38 PM
Though there is no way those ends would ever work themselves off, there are nuts at the end of each spherical end. Thanks for you concern fellas ;)
JDMized: No plans at all to beef up the rear. It's a unibody car so the shell is the subframe and the "jungle-gym" in the back is taking care of beefing that up. http://www.motoiq.com/magazine_articles/articletype/articleview/articleid/1548/pageid/1985/project-infiniti-g20-racecar--roll-cage-additions-final-interior-prep.aspx
Der Bruce: Having plenty of experience with comparable B chassis set-ups, I have to say that the car was pretty balanced right off the bat. All we have played around with are shock settings so far and are now thinking of upping the rears to 600in-lb. The alignment settings have given us damn near perfect tire wear, but we do need another degree of negative camber up front to have it right on the money. That's going to require a new thinner front shock set-up or some more custom trimming of the vertical third link.
Monday, June 06, 2011 3:36 PM
They arent cool until you paint them pink.
Monday, June 06, 2011 7:44 PM
Those endlinks are bolted to the strut and sway bar. As a result, they're not going to turn more than a couple of degrees before they run out of articulation anyway. I think it's highly unlikely that they threaded rod will find its way out of those spherical bearings, but if you're really worried about it, you can come on over and put a jam nut on there. :)
Martin, my plan for the front suspension was to move the upper shock mount inboard an inch or so, which will move the whole assembly away from the upright the same amount, and return the shocks' angle relative to the control arms to stock as well. Our only limitation there is the frame rails.
Monday, June 06, 2011 10:16 PM
I keep thinking how nice it would be if you could just shim the upper shock mount to get that 1 degree or modify the way the shock mounts down below.
Tuesday, June 07, 2011 2:17 AM
Your diagram of the rear suspension looks identical to the rear suspension on my car. Before you did the bushings, did it toe out much during cornering?
I'm trying to chase down a wobble on corner entry and wondered if you guys had the same problem.
Tuesday, June 07, 2011 10:04 AM
Der Bruce: How would we shim the upper shock mount to get more camber? The two problems I see:
1. As you probably know (but making sure), the suspension is multi-link. As such, the shock's position has nothing to do with camber other than for interference.
2. I just don't see where shims would have any effect on the upper mount, other than to increase droop and limit bump travel.
The lower mount is offset about as much as we can get away with before causing the modified upright to get dangerously close to the frame rails under bump.
My plan was to re-plate the upper shock mounts on the tower with new holes about 1" inboard, which should be possible considering how much wider the stock spring was than the 2.5" Eibachs we're running. This should give us oodles of clearance for JDM y0! levels of camber, return the shock's overall angle to 90* at full bump (better control over the suspension at a critical point in travel), and possibly solve world-hunger. ;-p
Daewoo: we never paid any attention to the rear toe curve with stock bushings. Hell, we've never paid attention to it period. If you're having a wobble on corner entry, this may be your cause. Should be pretty easy to grab a medium-sized pry-bar and check the condition of your bushings. If they've got excessive play (which is HIGHLY likely on a 20 year old car like ours), then a visit to the Energy Suspensions catalog is likely in order.
if not, then you might want to check your toe curve under bump to see if you've got an issue with the stock geometry, and either set your static toe to band-aid this, or look at moving pickup points.
Tuesday, June 07, 2011 12:31 PM
Steve: I spent about seven years and thousands upon thousands in the off roading world and started my switch over to the road going world a few years back, so my experience with road going suspension is limited.
BUT my thought was derived from your desire to move the whole mount inward about an inch or so. This may be where i'm confused because although shock position may no effect camber, as you mentioned, but I was under the impression that the shock angle does!? I was visualizing in my head that an angled shim, with one end thicker, one might be able to utilize the existing mount holes, prior to the extreme of moving the mount inward. Another thought was an adjustable camber plate.
I probably have better ways to help you fight world hunger, but I starred at that diagram on page 2 for a while trying to be helpful!
Tuesday, June 07, 2011 1:24 PM
30 series shocks don't have an option to be inverted. The only mono tube you can invert from Koni are the 28's
Tuesday, June 07, 2011 2:36 PM
Since you're talking off-road speak, think of a 5 link setup. You could put the shock at any angle, and it wouldn't change camber, since that is controlled by the upper links. Same thing with this setup: the upper link is what controls camber, the shock is only there to support the suspension and control the spring.
If you look at the diagram on page 2 for the front suspension (first diagram), find #5 shows you the upper link that controls camber. Note that no matter what you do to the shock, that upper arm is still going to hold the spindle upright. Also, if you look at the pillow ball mounts on page 3, you'll see that shims would only move the mount up and down, not side to side.
EB Turbo: I re-read the entire article, and see no mention of 30 series shocks being inverted. Errr, thanks?
Tuesday, June 07, 2011 3:36 PM
I had made a previous comment about the shocks being used on the car are not 3011's. They are twin tube 80 series. It mush have been deleted or something. monotube struts cannot take the side load so they must be inverted. That being said, Koni does not offer 30 series for a strut application. only 28's can be used as struts.
Tuesday, June 07, 2011 3:55 PM
EB Turbo: Your comment was deleted for your own good, thinking you'd reconsider your words. Since you insist, I implore you to re-read the article. We used Koni 3011 SHOCKS on the FRONT MULTI-LINK suspension and had the stock rear STRUTS rebuilt with a Koni wet kit.
So, again: errr, thanks? ;-p
Tuesday, June 07, 2011 8:07 PM
Steve: I think I'm understanding much better, but nobody makes a shorter upper, longer lower or modified spindle? No wonder it's so difficult to make adjustments :( I think I'd have to explain my shim theory with some poor drawings and in person. As someone older and less open minded than me once said, if it was such a great idea, someone would've invented it already.
Tuesday, June 07, 2011 10:05 PM
I could imagine a pair of shims. One below the mounting point and one above. They are angl cut, but allow for a flat bolting surface.
Wednesday, June 08, 2011 8:16 AM
Koni 30 series (not what they used) as well as Koni 3011 and 3012s can all be run inverted since they're a monotube shock. Even some twin tubes can be run inverted (I know QA1 claims this for many of their monotube shocks).
What kind of guts did you guys use in the rear? Any reason why you didn't just go with an 8611 in a separate body?
Wednesday, June 08, 2011 10:21 AM
Der Bruce: Going to be at Willow Springs? You can draw your ideas on a bar napkin and present them to me... ;-p
Jasonrg77: That seems like it would bind the pillow ball before we had any meaningful change in shock angle.
For the upper mount, we'll either weld a plate on the shock tower with new holes, and incorporate a shock tower/master cylinder brace, or just have a machine shop make us new plates with the hole 1/2-1" inboard (depending on available space).
Def: Went with a wet kit (basically, 8611 valving components) because no one made a G20 rear housing, and we had our stock housings just sitting there, gathering dust. We could've fit 8611s in the stock housing, but we felt that would increase sprung weight and waste interior space that could otherwise be used for fluid. Fabricating a new housing for this application was beyond my skills at the time, and would've cost more money for little net gain. We've been more than happy with the setup as it is now.
Wednesday, June 08, 2011 2:05 PM
Steve: I wish. I flew down for the Phoenix event and got to worked for the Redline tech crew. Met Martin taking pictures! I even took off work for the Thunderhill event to make the 7hr drive south. Now I have no Redline event this month with the closest looking like the PIR event up here in September :( I'm just going to have to go to the lake with one or two of those days now :)
Tuesday, June 14, 2011 5:17 PM
I'm making shortened upper control arms with eccentric adjustment for camber for G20's. It's still in the early stages having only finishing my second set. Camber change should be close to 2.5 degrees, mostly all negative. To go with these I also offer 3rd links(uprights that connect the upper control arm to the knuckle) with the lower shock mount moved in 1/2" and down 3/4". Also, I make upper shock mounts for G20's that move the shock rod position up almost 1" from stock, which gains back that amount of lost travel when lowering with oem replacement style shocks. The shock mounts are sized to fit the oem size springs but I'll be adding mounts to fit 2.5" springs to the line up also. I have made one set of nylon seats to fit the upper mounts and take 2.5" springs but they have not been proven yet. If any of these will help out let me know.
Tuesday, June 14, 2011 5:30 PM
Hmmm. Some typos in that last post.
Anyway, I forgot to add that the upper shock mounts are now being made with offset shock holes also, moving the rod towards the center of the car 3/8".
Wednesday, June 15, 2011 8:50 AM
@ DMS: Interesting. Would -2..5* be the maximum amount of negative camber you could get out of these, or is the base delta -2.5* over stock before playing with the eccentric bushings?
We've already moved our lower shock mount in 3/4", and don't plan on needing to move the upper or lower shock mounts down since we've got shorter than stock shocks that have limited droop as it is - if you look at the rear upper mounts, we had to make a spacer to return the perch to the stock position, since we had already shortened the struts.
Got any pictures of the arms, mount and upright? Shoot me an email at email@example.com and we'll talk some more.
Tuesday, July 12, 2011 1:20 AM
some questions about suspension:
i was wondering why your addco bar is goldish and the one i got is black?
is it possible to get some more pictures of your homemade end links, as i have just received mine though not as beefy and big as yours it was all i could get in a hurry on ebay. Was unsure about what you have done to properly connect them to the original mounts.
also would love some pics of the front links.
pleas hitt me up with info and pics on Ztaal3@gmail.com
ps Love this project, hope more is soon to come!
Tuesday, July 12, 2011 10:20 AM
Not sure why our Addco bar is gold and yours is black. We bought it direct from Addco in 2005 or 2006. They've probably switched coatings.
We still haven't made the front links. In order to connect them to the front suspension, you're going to need to weld a vertical tab on the upright instead of the horizontal tab so that you can just bolt the endlink to it. Sorry, no pictures, but we'll probably have to make a suspension article, part deux, since we've made some changes since writing this article (if you're not getting better, you're getting worse, they say ;-p).
Monday, April 30, 2012 6:02 AM
It really rocks. Really nice. :)