So, I think I need to increase my spring rates....

Discussion in 'Suspension and Chassis' started by Nvrfinished, Apr 12, 2018.

  1. Nvrfinished

    Nvrfinished TMO Advanced

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    Hey everyone. My S550 GT is setup on RideTech coilovers with Steeda front and rear sway bars. My spring rates are 350 lb front and 450 lb rear. The front sway bar is 35mm and the rear is 28.5mm. The front sway bar is a 4 hole adjustable and the rear is a 3. The front was originally set at the 2nd hole from stiffest with the rear in the middle. This setup seemed to work fairly well with the stock 19" Pirelli tires and wheels with the staggered sizing - albeit there was still understeer from the staggered setup when pushing it hard.

    I have since moved to a 19x11 square setup with 305/30R19 R compound tires. I also installed Vorshlag caster/camber plates set at -2.6* camber with 0 toe. The rear is -2* camber with 1/8" to 3/16" total toe in. Brake pads are G-loc R16 fronts and R12 rears with brake cooling on the fronts. I had to move the front sway bar 1 hole softer due to clearance issues I'm having with the sway bar end links interfering with the bottom of the struts (another story).

    Anyhow, I had some trips to Buttonwillow and a few other tracks with the previous setup. A couple weeks ago I got to run Buttonwillow with the new setup. My times improved considerably, but I now have some other issues to work out. The first seems to be spring rate related. I opted for 50 lb higher spring rates at all four corners than the default rates that RideTech selects for the S550 with the initial setup. The idea after talking with them was to find a decent compromise between street and track. This seemed to work well with the stock street tires.

    Well, when I ran Buttonwillow last week with the new changes I was noticing much more roll when transitioning from one corner to the next, particularly in the higher speed corners. I believe this is from the extra grip and speed that the new setup is generating. For example, it was most noticeable when exiting Club Corner (high speed 45* right hand turn) and then immediately transitioning into the short left hand sweeper towards the Bus Stop. The car held it's line well without getting upset, but the body roll was significant (relatively speaking). I attached some great pics I got entering into and beginning the exit out of Club Corner. You can see how much travel the suspension is going through.

    As a result, I'm thinking about upping the front spring rates to 400 lb fronts and 500 - 550 lb rears. I was hoping to get some input from you guys about this. The more I'm reading about suspension tuning for an IRS, the more I'm beginning to think that there needs to be more than a 100 lb difference in spring rate between the front and rear.

    Also, in a somewhat related issue, I'm getting a low speed push when entering the tighter corners. I believe I can help the issue by introducing some trail braking into the corners. For suspension tuning, everything I've been reading says to soften the front sway bar adjustment. Is that correct? I'm also thinking of increasing negative front camber as well.

    In higher speed sweepers I can induce some push with throttle, but it's nothing like the push in low speed corners. If I let off the throttle the front tends to bite more and the car feels neutral to a hair loose depending on how close to the edge of grip the tires are at.

    Pics are below. Any input is appreciated! Buttonwillow-club-corner-1.jpg Buttonwillow-club-corner-2.jpg Buttonwillow-club-corner-3.jpg Buttonwillow-club-corner-4.jpg
     
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  2. bpracer

    bpracer Mark

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    Don't do two things at once like I always do...

    If you are always pushing I would try more front camber. Looks like you have more camber in the back than the front in those pics. You certainly are working the rear tires.

    I'm always hesitant to stiffen rear sway bars, but you can soften the front one more hole as another step.

    Lookup the "learning to squat" thread if you are worried about too much body roll...
     
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  3. Nvrfinished

    Nvrfinished TMO Advanced

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    Thanks. I won't be doing two things at once. I just got done increasing my front camber and moving the front sway bar adjustment back a hole to the softest setting. I then checked the alignment and adjusted front toe (string alignments rock when you get the hang of it). The rears are still good at -2* - they've never been more than the front. The front in those pics was at -2.6* and now I have them at -2.9*.

    I think the reason the rears look the way they do in the pic is due to the amount of body roll and the fact that I'm accelerating some through the turn.

    I'm saving the possible spring rate upgrade for a little later while I work on the current push.
     
  4. Competition Orange

    Competition Orange TMO Advanced

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    I think those are the moves to make. Also ensure your tire pressures are good.

    You should be able to get it neutral with what you have, before making rate changes. Also, I'd jump 100lbs when you do end up changing, you probably won't notice 50lbs.
     
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  5. apex15stangPP

    apex15stangPP TMO Beginner

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    My 2 cents .... Your front spring rate is fine. Have you tried putting the front bar to full stiff?

    Also, you defiantly need more rear spring. The lowest I would run on a tracked S550 would be a 600. 400/600 would be a great setup for slicks, and then tune with the bars. Run very little rebound in the front( out 15-20) and 8-12 in the rear.
     
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  6. stuntman

    stuntman TMO Advanced

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    Sounds like a lack of damping. Where are your shocks set at and whats the adjustment range?

    Also get different droplinks and try the front bar at full stiff. Also measure your tire temps. That will dictate your camber.
     
  7. Nvrfinished

    Nvrfinished TMO Advanced

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    I appreciate the feedback!

    I didn't go full stiff on the bar for two reasons. The first is that I'm having a hell of a time with sway bar end links interfering with the RideTech strut. I couldn't go full stiff if I wanted to. It's a serious issue that is really causing problems. I can only go full soft or 2nd hole from soft on a 4 hole Steeda sway bar right now. I need to find a solution to this fast because it's frustrating me to no end. I don't know if it's because of the large monotube strut or a geometry issue on RideTech's part. They claim that clearance was checked on the factory bar and found to be OK. I know that people other than me are very happy with RideTech and finding a work around. I need to find out what that is.

    The second reason is that everything I read said to soften the front bar if you are getting a push on corner entry. One of my big complaints since going to a square setup was the amount of push I was getting on corner entry, particularly slower speed entries.

    I was back at Buttonwillow yesterday and I had increased my front camber from -2.6 to -2.9. I also moved one hole back to full soft on the bar. It made a big improvement on initial turn in and I lost a lot of the push I had, though not all of it. It felt much better regardless. I couldn't compare times to a couple weeks earlier since we ran 1cw yesterday with the Star Mazda turn vs 13cw with the sweeper from before.

    The more I've been investigating, the more I was thinking that I need rear springs with a larger spread in rate vs the front. I was thinking 400f - 550r, but you say 600 is more ideal? I do feel like I'm burying the rears with lots of travel in higher speed turns.

    I was 8 clicks out from 24 on all 4. I kept it the same after making the above changes since I wanted to see what type of difference they would make. It still felt softer than it should, though the feeling of too much roll did subside some.

    Excuse my ignorance, but I'm assuming that drop links are the same as end links, no? And yes, measuring tire temps is going to be the next step as I go along with this.
     
    Last edited: Apr 17, 2018
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  8. apex15stangPP

    apex15stangPP TMO Beginner

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    What brand of endlinks do you have? I'm very familiar with the ridetech setup. I'll help in anyway I can. I've done a ton of spring testing over the last 3 years, and I have two setups I think worked very well (for my driving) but anything under 600 in the rear and I was always bottoming out in this case the shock is not longer working. Ive even tried 750, 800 range in the rear but it was a bit much for a 200 treadwear tire. Now corner entry push I would first look at my driving style, how is my brake release, down shifting, etc. In a road course setup I would run less rebound in the front, again works for my driving style. I also have the triples so I have a wider range of dailing in the setup, but I also ran the singles.
     
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  9. Nvrfinished

    Nvrfinished TMO Advanced

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    Thanks much, that would be fantastic! Any help would be greatly appreciated to solve this end link issue. Your experience also confirms my suspicion about the spring rates.

    Initially I was running Steeda adjustable end links with Steeda bars. I still couldn't go full stiff on the front bar, but I could use the other three holes. I recently installed Vorshlag camber/caster plates to get more camber as well as to make adjusting the camber easier. I did this because I was switching to R compound tires with 19x11 wheels and knew I was going to need more front camber.

    After doing that, the larger ball joint ends were interfering with the hard brake line from the strut moving closer inboard with more camber. I slightly bent the hard brake line mount inboard to gain clearance on the driver side and drilled a new hole in the mount on the passenger side to move it back 1/2". This gained clearance for the top, but then the shaft of the end link was contacting the bottom of the front strut.

    I have since installed a set of Scott Drake end links up front. They use a heim joint that is smaller in diameter than the Steeda ball joint and the stud length is slightly shorter from the back of the joint to the mounting surface for the bar. This allows enough room to run the two rear holes without interference. I had tried flipping the bottom link to the the other side of the bar, but the geometry is not right and will lift or push down on the bar when turning. I'm at the point where I was going to start measuring bars to see if there is a difference among manufacturers.

    Going with the Vorshlag camber plates created more front droop due to the fact that the top of the strut actually sits about 3/4" lower in the upper perch than the RideTech perch, but I do not believe it changed end link geometry. It just required that I adjust the collars to gain the same ride height as before.
     
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  10. stuntman

    stuntman TMO Advanced

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    8 from full soft or full stiff?

    Yes droplinks = endlinks.
     
  11. Nvrfinished

    Nvrfinished TMO Advanced

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    8 from full stiff with a range of 24 total
     
  12. gtorpedo

    gtorpedo TMO Advanced

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    I've got a similar setup and here's how I run currently - I really like it.

    Ridetech Level 2 400f/500r
    7-8 clicks from full firm front & rear
    BMR sways set to full soft front/rear (delrin bushing up front)
    Full tilt boogie endlinks
    I also have the endlink interference issue with the front strut and I understand your frustration. Fortunately, I've not felt the need to increase the stiffness of the front bar.

    I ran this setup last month at VIR with 285/35/18 RS4's and was very happy. I'll be back out this weekend with 305 NT01's so I may have to tweak but I think this will be a good starting point for me.
     
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  13. Nvrfinished

    Nvrfinished TMO Advanced

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    Great! I'm glad to hear that I was thinking in the right direction about increasing my spring rates. It's even better hearing from others running RideTech. With the exception of the end link issue, I really like how they perform.
     
  14. gtorpedo

    gtorpedo TMO Advanced

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    BTW, I am running less camber than you. 2.3* front and 1.5* rear. I have the Vorshlag CC plates that I’m waiting to install and will likely push the front camber out a bit with the NT01’s.


    Sent from my iPhone using Tapatalk
     
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  15. Nvrfinished

    Nvrfinished TMO Advanced

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    FYI, the Vorshlag plates locate the top of the strut about 3/4" lower than where it sits currently and the upper perch is located higher than the RideTech perch. This creates a shorter overall assembly. If your care sits low, you will have a small gap between the top of the spring and the perch at full droop. I've been holding off on getting a set of 4" helper springs and stackers from Hyperco until I order the higher spring rates.

    Also, I had a conversation with a member on another forum, ddozier, who runs RideTech as well. He said that to run the two forward stiff holes on the front bar, he swaps the front struts to opposite sides which allows the mount on the strut to point forward, thus avoiding contact with the end links. It will not work for the softer settings though and requires that you change the struts back.
     
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  16. ddozier

    ddozier TMO Intermediate

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    Hello Nvrfinished sorry for the delay I do not get to this forum very much anymore, I just did a Ridetech install on a GT350 and the new updated design of the Ridetech single adjustable allows for the upper sway bar mounting point to now be mounted on either side of the strut body so you no longer have to swap the strut assembly from side to side to move the end link mounting point. If you have the old design struts like I have they have the mount welded to the body of the strut and they need to be swapped side to side to make the change.

    I have the early RideTech single adjustable setup on my car and run a 7" spring height and a tender spring as the higher you go in spring rate the harder it is to keep the ride height low enough for what I want. If you stay with the standard length 8" springs you will run out of adjustment on the shock body to lower the car. I think this happened at about the 650lb rate in the rear that I started having this problem. I do run my car low with only about a 1/4" of rake front to rear.

    Rake and overall ride height will effect everything in your setup so consider ride height and rake as another method of tuning along with alignment and spring rate front to rear. If you have a slight understeer at apex and steady state of turn try adding a little more rake to your setup, 1/16th to 1/8" changes are big changes so think in 1/2 turns on the shock body adjuster. You may find this cures your understeer if all other states of the turn the car feels neutral.

    With so many things to adjust if you have access to a skid pad (or a really flat parking lot and a chalk box to make your own circles) I would spend a day driving the skid pad and making a single change, drive the car and feel the effect of the adjustment and how it effected the car at low and high speeds. If you get a chance to do this you can dial in your shock settings and bar settings very quickly. This will set the cars steady state turning feel for oversteer, understeer or neutral. Once that is set consider this you home starting point for all future adjustments. This is also a good way to get the tire temp data you need to set camber both front and rear. Couple of jacks and some hand tools and you can make a lot of adjustments in a few hours and get real time feedback for what you have done. Take notes you will need them for future setup changes. You will know what effects what so at you next track event if the car feels loose you know what steps to take to cure it on your car with your current setup and without spending a dime.

    For me the key was to get the rear locked down then dial in the front, I am willing to live with a very slight push while on the power coming out of a corner if it means I can get on the power faster. Everyone likes a different feel, I setup my car to be very neutral at turn in with a hint of understeer building through the turn as this is the safest setup for most drivers and my car is a demo car for the builds I am doing so it gets handed out a lot. A couple of shock settings, a bar change and a tire pressure change and the car can have no sign of understeer. This assumes you are driving it correctly, most cases of understeer are really caused by driver inputs not necessarily a particular setup.

    Dave
     
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  17. JDee

    JDee Ancient Racer

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    Totally agree with that last sentence. I've always thought the very best racers could drive through/around car handling issues and that's what separates them from mere mortals like me.
     
  18. Eritas

    Eritas TMO Intermediate

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    Pic of your static ride height? Running too low in the rear lowers the rear roll center A LOT - increasing rear grip and roll.
     
  19. Nvrfinished

    Nvrfinished TMO Advanced

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    Thanks for the additional info, Dave. I learned a lot from our last conversation in the other forum. And yes, I have the older style with the mounts welded to the body.

    I won't be changing spring rates for another month since the tracks out here in SoCal are too hot during the summer. My thoughts are to go with 400lb fronts and 600lb rears to start. I will just order the 7" coils then since I already need helper springs in the front from the Vorshlag camber plate install. Due to spring rate being the most important change to make at this point, I will start making initial adjustments from there. My current height at the front fender lip is 26-3/8" with 305/30R19 tires and a rake similar to factory with an approximate 1/2" difference front to rear. I will start with a 1/4" difference as you suggest.

    Ultimately, the handling characteristics I'm seeking is similar to your ride. Unfortunately, I don't have access to a skid pad or a large empty parking lot without inviting a visit from the local police :p
     

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