GT350R Springs for GT (high rate, minimum lowering)

Discussion in 'Suspension, Brakes & Chassis' started by valentinoamoro, Oct 12, 2016.

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  1. Bluemustang

    Bluemustang Well-Known Member

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    Agree with recommendations above. Alignment and front sway bar. Might also want to consider increase to the rear camber too. More to the negative.
     
  2. Radiation Joe

    Radiation Joe Well-Known Member

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    Thanks for the great advice. This why the forum is so valuable. Sounds like these cars are sensitive to toe settings.
    No need to clock bushings. Ride height hasn't changed noticeably.
     
  3. Radiation Joe

    Radiation Joe Well-Known Member

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    Check corner weights off the list.
    I've never seen a perfect balance without spending time adjusting coil-overs til now.
    LF-1000#
    RF-1000#
    LR-920#
    RR-920#
    Granted I used a truck scale but it's good to +/- 20#. I was in the car. Wow!
     
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  4. BmacIL

    BmacIL Enginerd

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    That's amazing!
     
  5. Radiation Joe

    Radiation Joe Well-Known Member

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    I weighed the two fronts (2000) and then the whole car (3840) then the right front (1000) and then the right side (1820). I'm sure if I had then hit the left rear and then left side it would have changed, but there is no way it would change enough to discount a great corner balance set up. I spent an hour and a half balancing the e46 with coil-overs and didn't get it perfect. Disclaimer is that today was on a truck scale that isn't any more accurate than +/- 20#.

    So theoretically at +/- 20 lbs, it could have been
    LF-1020
    RF-980
    LR-900
    RR-940
    That would still yield a cross percentage of 51/49 which is nothing to sneeze at.
     
  6. MajHazrd

    MajHazrd Member

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    I finally got to install my suspension. I bought the parts last fall. Between work and home projects I didn't get a couple days to work on it.
    I got the SP083s, BMR adjustable sway bars and the yellow Konis.
    I took it on a 6 hour cruise yesterday to see family. I had the Konis on full soft. My wife even said this rides better than stock!
    It is more planted, responsive (took that "feels big" feeling out) and stable. To me the PP always felt like it would rock from side to side and was stiff. The ride is plush at full soft. This is just what I wanted to be able to do, dial soft DD, dial stiff for Track Day.

    Can't wait to get to the track to try out stiffer settings on the Konis.Two weeks to BIR!

    I could not be happier with the set.
    Thanks a lot guys!
     
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  7. BmacIL

    BmacIL Enginerd

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    Try the Konis at around 3/4 turn up from soft for the street. They rode better to me there than at 1/4 turn (basically full soft).
     
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  8. SlowStangGT

    SlowStangGT New Member

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    Hi All!

    I'm new here, and there's a lot of great information on this thread and across this forum. Hopefully this is the right place to post this!

    I'm looking to stiffen-up my car and make the steering more responsive - while still being daily-drivable.
    I daily drive a 2017 Mustang GT PP completely stock (with the exception of the Steeda clutch assist spring and a Corsa Sport cat-back)
    I currently do a lot of spirited driving through Bay Area backroads and in the future I plan on taking my car to auto-cross events.

    Based off of research gathered from this forum, my build proposal so far is as follows:
    • APEX SM-10 19x10 + Michelin Pilot 4S @ 285/35r19
    • FRPP Track Dampers
    • Steeda Tension Link with Bearing
    • Steeda Roll Center Correction Lateral Link + Bumpsteer kit
    • Steeda Stop-The-Hop Kit (IRS Alignment, Brace, Bushing Supports)
    • FRPP Knuckle to Toe Link Bearing
    • BMR SM760 Rear Shock Mount
    I am holding off on the RLCA bearing for now due to concerns over NVH.

    The only decision remains is what springs to choose, namely GT350R springs or BMR SP083 springs.
    • GT350R - 240f/920r lb/in @ .7/.3 inch ride height drop
    • SP083 - 250f/980r lb/in @ .88/.75 inch ride height drop (or .5 inch rear if used with a Steeda 1/8 inch spacer)
    I am hung up on the following reasons:

    - The GT350R has less of a drop front and back, but Steeda's Extended Ball Joint is *ideally* designed for a 7/8 inch drop; the joint is .625 inch more than stock whereas a GT350R ball joint is .5 inch more than stock. Given the design of a McPherson strut cg to rc drop ratio is roughly ~3:1, I would be raising the roll center probably .6-.7 inches higher than Steeda and/or Ford deems is ideal, and I am not sure how far off from 1:1 the motion ratio would be. I am also not sure what other unintended effects this would have, such as increased camber gain under braking or faster tire wear from scrub during suspension travel if the motion ratio is far off from 1:1. Seems like @BmacIL runs GT350R fronts with this and doesn't have issues, I would love his input :)

    - The BMR SP083 front spring matches PERFECTLY with Steeda's Extended Ball Joint @ a 7/8 inch drop. However, the rear drops too far for my liking and I would probably want to run it with a 1/8 inch spacer to raise it 1/4 inch (total .5 inch drop). I'm still worried that this may be too low of a drop in the rear, as the rear roll center drop is worse than the front roll center when lowering the same distance. I know @Bluemustang runs this without a spacer and loves it, I would love to hear more on his thoughts :)

    - The BMR SP083 springs are 5% stiffer, but this is probably unnoticeable and a non-issue.

    Please tell me if I'm over thinking this too much and I should simply choose one or the other!
    My gut is also telling me I would probably also not notice the difference, which would mean I should choose the GT350R springs for the extra .2 inch of ride height gained, as I'd prefer to lower as little as possible. :)

    Thanks!
     
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  9. BmacIL

    BmacIL Enginerd

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    Flip a coin! Go with your gut on the height. If it were me, now, I'd go with the SP083 set, as the 0.5" drop 980 lb/in rear handling springs that I have are no longer available. IMO, SP083 is slightly better than the GT350R spring setup, but it's really close. If you felt stronger about not lowering that bit extra, I'd say R springs.

    Either way you're going to be very happy with the handling. Two things that I'd add to your list without question: BK055 RLCA bearings and SB044 front sway bar.
     
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  10. Bluemustang

    Bluemustang Well-Known Member

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    I totally agree with @BmacIL. Not much to add because he pretty much summed it up.

    @SlowStangGT
    I will say with that build list, you will do a lot more than just improve the steering response. It'll be transformed. My advice: listen to him on those last two things - the BK055 and the front bar. That completes the handling.
     
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  11. SteedaTech

    SteedaTech Well-Known Member
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    Another great choice great choice is the Steeda Comp Dual Rate Springs. They are remarkable on track and street. Especially coupled with the adjustable Steeda Pro Actoin Dampers!
    Also, our IRS subframe support braces are substantially lighter than other offerings providing outstanding control.
    Steeda Tech
     
  12. Norm Peterson

    Norm Peterson corner barstool sitter

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    I'm guessing it'll run in CAM-C or C-Prepared unless there's a novice class you can run in.


    I agree that for a typical strut suspension that the geo RC height drops by somewhere between 2 and 3 times as fast as the front ride height drops, but I don't think the boldface part above concerning what's essentially an SLA rear suspension in front view is true (I'm thinking the RC to ride height 'drop' ratio should be much closer to 1:1).


    Norm
     
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  13. Rebellion

    Rebellion Well-Known Member

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    There is no shame in mixing spring brands and using spacers. With the rate difference being negligible, it's up to you to decide on the right look with choosing the drop. The small difference in front roll center with the R spring vs the BMR is also not a lot, as you can tune balance with other means (alignment, mainly).

    One caveat here, as I found out empirically, the difference on front vs rear drop has a consequence. The more you drop on the front vs the rear, you will gain rear grip and tend towards understeer (if everything else is kept constant). This is what I found out when adding a spacer to the rear spring, I chose to compensate this change in balance by using a R rear bar (could also be tuned via alignment). Not a big deal, but it's something to consider.

    As other have said, do the LCA bearing, this makes for huge improvement. Personally I would do the CB005 plus alignment sleeves instead of the kit as the attachment points of the BMR part make more sense.
     
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  14. SlowStangGT

    SlowStangGT New Member

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    Hi Rebellion, could you briefly summarize or link examples of alignment changes and how they correspond to the balance of the car? I've never thought about using alignment as a tool for this :)
     
  15. Bluemustang

    Bluemustang Well-Known Member

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    The alignment has a big effect on how the car handles. However it's not that simple as saying do this and it will do that. There are many factors including suspension design/geometry, driving style and intended use of the car.

    For example, changing the alignment can give or take away grip from one end of the car. Most people run more negative camber on the front because of the MacPherson strut design. As the car rolls in corners, running more negative camber up front will give it more grip due to there being a better tire contact patch. This can reduce the understeer (tendency for the front tires to roll over into positive camber, thus losing grip). Generally for cornering and track/road course driving you want a lot of negative camber for this reason. Better tire contact patch during body roll event. This is good, but there is no free lunch. More static negative camber decreases stability to a degree and more negative camber in the rear decreases straight line grip because less ideal contact patch.

    So what you have to ask yourself is, what is your intended use for the car and what is your driving style? All these changes don't exist in a vacuum. There are many factors at play.
     
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  16. SlowStangGT

    SlowStangGT New Member

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    Definitely. My priorities in this order are:

    1. Frequent (weekly) spirited driving through backroads.
    2. Occasional (probably once or twice a year) AutoCross and/or track events.
    3. Meet the above 2 criteria without ruining my spine as a DD (I'm only 26 so I don't mind a firm ride, and my commute is only 10 miles).

    I'm thinking of sticking with Kelly's suggestion of having 1.5 front and 1.25 negative, but with zero front toe.
    Should be the best balance for now.

    Nice to know that if I decide to go SB044, I can adjust my tuning with both the bar setting and the alignment.
    Although I'm thinking I wont notice it 99% of the time as I only would want to be driving 6/10 or 7/10 (if that) on backroads :)

    One question I do have is, I'm wondering if those alignment specs should change with Steedas Roll Center Correction lateral links. Since camber gain is going to be much more, would it make sense to dial front camber back to 1.25?
     
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  17. Bluemustang

    Bluemustang Well-Known Member

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    That's good, and you can also go further more to like -1.8 in front and -1.5 in the rear. A little bit more aggressive but with an emphasis on cornering. I would also recommend caster/camber plates, as the front camber is not adjustable and this will allow you to fully dial in. For autocross/track, you'll want as much front camber as the plates will allow. -2 to -2.5 would be pretty good for this. And then just dial your rear camber to be about 0.5 degree less than the fronts.

    Zero toe up front IMO is the best for responsive steering. But just be aware it'll be a little twitchy. Small corrections. If you want more stability use more toe in (i.e. positive toe). You don't want negative toe as that increases instability (also increases turn in/response). Also on the rear make sure you have at least 0.10 toe in per side. Without adequate toe in the rear will feel unstable.
     
  18. BmacIL

    BmacIL Enginerd

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    Even with the improved camber gain, the dynamic camber still sucks (all McPherson struts do). I would suggest -1.5 front for how you're using the car.
     
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  19. Rebellion

    Rebellion Well-Known Member

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    @BmacIL and @Bluemustang have said most of it.

    The tuning I refer to is to mainly set the camber of the front and rear to adjust the neutral balance of the car (when cornering and not accelerating or braking). With everything else being equal and your caster and toe being already decided, you add lateral grip by putting more negative camber to the front (decrease understeer, increase oversteer) or the rear for the opposite effect, generally. Keep in mind that there are many factors at play here, I prefer to do this at the very end when all of your major mods (including wheels and tires) have been installed.

    There are drawbacks for excessive negative (wear, straightline performance, etc), so don't go crazy with it. When I get my Steeda arms and camber/caster plates done, I will likely start with 0 toe front, 0.1 toe in on each of the rear, -1.7 camber front and -1.2 camber rear. From there I will evaluate the performance of the car in hopefully a track day, and I believe I might need more negative on the front. Also, balance needs to fit well with your style of driving, I prefer a slight neutral understeer so I can control the power oversteer when I need more turn in. I currently have -1.5 front and -1.2 rear, I'm limited on the front since I lack camber plates.

    Following the rough guidelines posted here will give a very good baseline to work with, 0 front toe, 0.1 toe in rear, pick some camber between -2 and -1.5 for the front, add 0.3-0.5 positive and use that for the rear. Drive for a while and get into an event or two, then adjust the camber to your liking.
     
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  20. battousai

    battousai Well-Known Member

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    #580 battousai, Jul 2, 2019
    Last edited: Jul 2, 2019
    Has anyone tried the FRPP Track suspension paired with Swift R springs? I've been running on Steeda Proactions with Steeda progressives for the past 3 years but want to eventually "finish off" my suspension whenever I decide to take apart my rear end for the rear LCA and toe to knuckle bearing.

    I know the FRPP Track + BMR Handling SP083 is a glowing combo but I like the slightly more rear drop of the Swift R and the spring rates seem comparable.

    Here's my current setup:
    Steeda front Proaction fixed struts
    Ford PP rear shocks
    Steeda rear shock mounts
    Steeda progressive springs
    Steeda front LCA bearings
    Steeda tension/lateral links with bearings
    Steeda bump steer kit
    BMR front sway bar
    Steeda G-trac bar
    BMR adjustable rear camber links
    Steeda rear toe links
    Steeda vertical links
    Steeda rear drag sway bar
    BMR cradle lockout
    BMR IRS support brace system
     
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