GT350R Springs for GT (high rate, minimum lowering)

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

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  1. BmacIL

    BmacIL Enginerd

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    You'll probably end up right around or just over 1" drop in the front then.
     
  2. MajHazrd

    MajHazrd Member

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    Update from my first track with the new suspension set up.... I was able to cut 6 seconds off of my previous lap times with the new set up!!
    In May I installed BMR SP083 spring set, BMR adjustable sway bars (middle setting), Koni Yellow adjustable struts and shocks and G-LOC R10 front pads on my 2015 GT PP. I'm running Michelin Super Sport A/S 3+ for tires.

    Track day was at Brainerd International Raceway in MN. It had rained in the morning, humidity was high and it was 80 - 85 degrees out.

    I feel like I had a lot of understeer, the front tires would squeal around every corner, tried to find a line they would be happier and faster at. Previous track day at BIR I had the Perelli P-Zero Ultra Performance factory tires on the front, never had any squeal, but I was also 6 seconds slower. Several were commenting that the track felt slippery.

    For the first session I ran with the Konis set at 1.5 turns and tire pressures down around 30 lbs. I had a lot of understeer and struggled for control.
    I increased the air pressure to 40 lbs Front and rear and set the Koni's to full hard. I had better handling overall, but late in the session the tire pressure must have got to high to the point that twice all 4 tires let go! It as like I hit patch of black ice or oil on the track. Backed off a little to cool them down and they were fine again. I was able to recover safely both times, but it surprised the hell out of me! It would have been a brown trouser moment if it would have been on the long sweeper turn 2!! Needless to say after that I didn't push to hard around turn 2.

    I backed the air pressure down to 35lbs just after I got off the track to make it the warm tire pressure and ran this pressure and the Koni's at full hard the rest of the day.

    I'm wondering if can improve my suspension set up or am I tire limited at this point. I didn't feel like I was railing it or getting slammed into drivers door or the counsel in the corners, yet I was getting understeer.... or was it just smoother and not as noticeable?
    What tire pressures do you guys run on the track, cold/hot.

    I could have shaved off significantly more time if I had less understeer (obviously), because the rearend never broke lose, I had good acceleration/speed and braking with the G-LOCs was incredible.
    I use mine as a daily driver and will get better performance tires some day, but for now I have the AS 3+ as good all around tires.
     
  3. Roadway 5.0

    Roadway 5.0 Strassejager

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    Glad to hear you lapped 6 seconds faster, that's an awesome improvement! To answer your question, yes, you are limited by tires. Get good tires for best results. For now, start with adding camber plates and get your front tires at least over -2.0 (-2.5+ even better) then reassess your under-steer issue; if your front tires are still breaking loose early then adjust your sway bars as needed.
     
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  4. BmacIL

    BmacIL Enginerd

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    Good to see. Can you post your alignment sheet/current settings? You probably don't have enough front camber as mentioned above.

    Your AS tires are going to be far more prone to understeer than a max or extreme performance summer, so that will ultimately be a limiting factor.

    On tires: you should be using pressure to do two things: 1) keep your sidewalls from rolling over, and 2) managing temperature and wear. Run them as low as possible to satisfy #1, unless you are seeing odd wear or temperature spread on the tire. For street tires, you'll probably want to be around 34-36 hot in the front to accomplish this, so 3-4 psi less cold. I've yet to see someone who's quick on track running the same pressure front and rear. I run, and typically see about 2 psi less at the rear.

    On shock settings: do not rely on these for increasing overall suspension stiffness. The function of dampers is to control the rate of weight transfer. Unilaterally setting them to soft or fully hard is not going to maximize the car, usually the opposite. I would start them at about 1-1.5 turns from soft. Because they're single and predominantly rebound adjustable, when you stiffen the damper, you're mainly slowing weight transfer to the opposite end. Stiffening the rear means that you'll end up worsening a corner entry push, and possibly more propensity for corner exit oversteer. Stiffening the front struts, usually the opposite. My advice with this is to think about what phase of the corner you need more grip from quicker or slower weight transfer.

    Bar settings: midcorner balance. Don't fear the front bar if you have an aftermarket rear bar too. These cars like a stiff front to make them work (and there are good reasons why).
    Camber settings, all phases of the corner but you'll really notice a lack of front camber in the middle of the corner.
    Damper settings: entry and exit balance changes only.
     
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  5. Bluemustang

    Bluemustang Well-Known Member

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    Great advice by @BmacIL as to how to tune it. Another thing, which I initially overlooked, is that your tires need to match the suspension. So although the A/S tires will be adequate, they're much less than ideal especially with the firmer than stock suspension. Summer tires and more front camber could be a good place to start.
     
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  6. MajHazrd

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    I'm going to put it on the rack and get new readings on the alignment settings. I'll post once I get them. I don't have Camber plates, so haven't adjusted it.

    Thanks for the suggestions. I'm always guessing at tire pressures. I'm going to check alignment settings all around, back off the Konis to 1.5 and tires with hot 34lbs F and 32lbs R first for the next trackday which is at RoadAmerica. Long straights and wider corners. If I feel I need more bar after that I'll move it to the forward hole to stiffen it up.... not sure I could do it at the track.
    Tires will be next.
    Need to take my laser temperature reader with me this time too.

    One thing I don't like about the Koni shocks on the S550 is that I have to jack the car up to change the settings. I'll have to make a tool I can adjust them with without jacking up the car. I can just reach them, but can't quite turn with my finger tips. I had a couple of guys try and couldn't get it, borrowed a jack from another driver.
     
  7. Chief_GT

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    I’ve read through the whole thread. Lots of great information.

    I have a 2016 GT/PP completely stock. This isn’t an everyday car so ride harshness doesn’t bother me. The car is a weekend/ nice day cruiser with a few track days and auto cross events a year. I don’t want the car to be slammed but slightly lower and a little stiffer. I was thinking if the following but would like some input.

    GT350 Front Struts
    GT350 R Springs
    PP Rear Shocks
    BMR SP082 Springs
    Rear billet shock mount since I would be right there anyways.

    Upon reading it seems the stock PP sway bars are plenty when paired with stiffer springs/ shocks and wider stickier tires.
     
  8. 2015Etrac

    2015Etrac Well-Known Member

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    I'm glad I checked back in on this thread. I'm about to take my car to the track with the GT350R springs and Koni shocks along with the PP braces and GT350R strut tower brace, so I'm hoping it handles as well as I think it should. I'm taking my SVE wheels and Michelin A/S 3+ tires off and putting the factory 20" wheels with stock Pirelli summer tires in 265/35 back on the car. My only concern is that it will be cold (40 degrees or so) and the wheels are about 12lbs heavier per corner than my aftermarket setup. I'm sure the extra weight will slow it down some, but I doubt someone like me with no track experience will notice any great reductions in speed. I just hope the 265 tire is enough for the track, especially with my firmer suspension, it seems like most of the guys will be running much wider tires.
     
  9. shogun32

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    You have a Magneride controller?
    The PP rear shocks are the worst part of the PP package. Scrap them for anything else.
     
  10. Chief_GT

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    Early GT350s didn’t have magnaride only the R did.
     
  11. Bluemustang

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    Good luck Etrac, hope you have a great time man. Let us know how it goes. What event are you doing?
     
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  12. Norm Peterson

    Norm Peterson corner barstool sitter

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    #597 Norm Peterson, Nov 6, 2019
    Last edited: Nov 6, 2019
    On cold weather . . . take it easy for the first two or three laps in order to give the tires time to warm up. This is something that I would expect will be stressed at the drivers' meeting (think "cold tires . . . cold tires . . . cold tires"). Summer tires will warm up, and if anything cooler temperatures help keep them from being overheated and turning "greasy". Maybe don't brake all the way into ABS activation the first lap or two either, as the tires could be a little lazy about returning to full rolling.

    As a true track novice, don't even think about such minor things (let alone worry about how they might hinder lap times or straightaway speeds). Not even ahead of time (once you're at the event you're going to be busy enough learning the differences between street driving and track driving to notice any such minor "equipment limitations"). That's in quotes, because at this point such considerations are just theoretical noise. 265 tires are more than good enough to see you up to an intermediate run group, which is mainly going to come from you demonstrating that you can safely, smoothly, and reliably do your part out there.

    Equipment-wise, keep an eye on tire hot pressures. At the very most dial the Konis up a bit just once and don't touch them again until it's time to drive home.


    Having fun (and learning a thing or two in the process) is where your main focus needs to be at this point.


    Norm
     
  13. 2015Etrac

    2015Etrac Well-Known Member

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    Thanks for the tips. I'm looking forward to being able to push the car a bit and see how the GT350R suspension stuff feels on the track, along with the Brembos I added.

    I ran into a snag today, apparently my SVE wheels are frozen to the PP rotors I installed this spring, I guess I should have used anti-seize. Kicking and big hammers (tough to do on jack stands) failed before the rain came, so I've heard the next best option is to keep 2 loose lug nuts on and drive it back and forth a few feet until it breaks free, which I hope will work. At least I found all this out before track day. One think I noticed about the Koni shocks is the top adjustment part rust badly on the rears, I wish they would have used an alloy or painted it to keep the rust away. So now I'll have to grab some pliers and break that lose to adjust them as well. I need to move to somewhere with less rain.
     
  14. BmacIL

    BmacIL Enginerd

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    You need a big sledge with some mass (8+ lbs). Hit the wheel with a block of wood between it and the hammer. The momentum will take care of it. Hit right at the bottom.
     
  15. 2015Etrac

    2015Etrac Well-Known Member

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    Thank's. I'll give it a try. Even with jack stands I was getting a bit scared hitting the tires from under the car with a sledge. haha

    I bought some anti-seize to help prevent this in the future. Sorry for all the questions and getting off topic everyone.
     
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