GT350R Springs for GT (high rate, minimum lowering)

[BmacIL]

I'm not all that surprised. Wheel rates per BmacIL's table aren't excessive (and are actually a few lb/in softer than the BMR handling springs I now have on my S197).


Norm

Yeah, it's on the firm end of the DD-able spectrum, but still in it. Firm enough for great handling and acceptable body roll when tracking the car, but soft enough to not punish you on your average road. When you start going north of ~300 lb/in wheel rates (corresponding to ~2 Hz) is when it starts getting harsh. Autocross only guys (SP or CAM-C) are running in the 400-450 lb/in range, some even higher than that.

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[GTP]

Just presenting the other side of the coin, and stating the obvious ...

A stiff suspension can also cause loss of traction going over bumps.

Claims of how improved the handling is with stiff springs usually do not also describe how smooth the road has to be. It is hard to justify optimizing the car for the 1% case of racing around a smooth road corner, when 99% of the rest of the time the car is traveling over typical pavement during daily driving.

Hence the case for progressive rate springs, I suppose.

 

[BmacIL]

Just presenting the other side of the coin, and stating the obvious ...

A stiff suspension can also cause loss of traction going over bumps.

Claims of how improved the handling is with stiff springs usually do not also describe how smooth the road has to be. It is hard to justify optimizing the car for the 1% case of racing around a smooth road corner, when 99% of the rest of the time the car is traveling over typical pavement during daily driving.

Hence the case for progressive rate springs, I suppose.

Somewhat, but a lot of that is not being properly damped. Too high of rebound damping will cause issues with tires staying in contact with the road over bumps.

 

[Norm Peterson]

Claims of how improved the handling is with stiff springs usually do not also describe how smooth the road has to be.

Probably because most of the cars that get modified are not getting modified to improve/increase their rough-road capabilities.

It is hard to justify optimizing the car for the 1% case of racing around a smooth road corner, when 99% of the rest of the time the car is traveling over typical pavement during daily driving.

There's more to 'handling' than just the objective skidpad and slalom numbers obtained in testing.


Norm

 

[GTP]

My point (that I did not make sufficiently well) is that the stock suspension is pretty good as a DD, and the occasional "1%" spirited driving can be handled (pun) with Driver Mod.

Note that I am not trying to criticize suspension modding in a roundabout (pun) way. I want to mod mine, too, but it is a balancing act between DD and race car.

Heck, my car is not PP, nor does it have summer tires, but at least I put 275's on it.

 

[2015Etrac]

My point (that I did not make sufficiently well) is that the stock suspension is pretty good as a DD, and the occasional "1%" spirited driving can be handled (pun) with Driver Mod.

Note that I am not trying to criticize suspension modding in a roundabout (pun) way. I want to mod mine, too, but it is a balancing act between DD and race car.

Heck, my car is not PP, nor does it have summer tires, but at least I put 275's on it.

I was worried about modding my suspension since the car is my daily driver and the roads around here are not the best, but the ride actually improved significantly even for driving to work or the store. It turns better, changes lanes better, and even helps me dodge those last second potholes. It feels a lot snappier and more responsive with the ride quality still being pretty close to where it was. I was worried the car would feel like I was riding in a Conestoga wagon after throwing on the new springs and shocks but I was really surprised at how well it works. My only concern would be ride height for a daily driver, but as long as you stick with a minimum drop spring you should be fine. The new suspension made my car feel less boaty if that makes sense. I do want to add some 19x10 wheels and wider tires soon which I think would pull it all together, right now I'm running factory 20" wheels and summer tires.

 

[GTP]

I was worried about modding my suspension since the car is my daily driver and the roads around here are not the best, but the ride actually improved significantly even for driving to work or the store. It turns better, changes lanes better, and even helps me dodge those last second potholes. It feels a lot snappier and more responsive with the ride quality still being pretty close to where it was. I was worried the car would feel like I was riding in a Conestoga wagon after throwing on the new springs and shocks but I was really surprised at how well it works. My only concern would be ride height for a daily driver, but as long as you stick with a minimum drop spring you should be fine. The new suspension made my car feel less boaty if that makes sense. I do want to add some 19x10 wheels and wider tires soon which I think would pull it all together, right now I'm running factory 20" wheels and summer tires.

Thanks for the encouragement to mod the suspension. I had the opportunity to test drive a used GT350, specifically for a harsh ride. But the short drive was on roads that were too smooth, and so it was a waste of time. I think it is important for me to try that again on rougher roads, before I go to all the trouble and expense of a suspension upgrade.

 

[Bahndvr]

Conestoga wagon, now I wonder how old you are?

 

[2015Etrac]

Conestoga wagon, now I wonder how old you are?

I spent some time in one while heading out west.

 

[Bahndvr]

We made it as far as the Illinois Territory. ;)

 

[saf1]

Question if you will. Balance was mentioned in an earlier post and I'm trying to understand what it was in reference too. I think it was noted with the GT350R front and BMR SP085 rear combo.

The GT350R's are 890 rear compared to the SP085 BMR's at 980. The difference is 90 mathematically but I do not know how or what that translates to or if it matters for me (based on being a beginner @ track).

 

[2015Etrac]

Question if you will. Balance was mentioned in an earlier post and I'm trying to understand what it was in reference too. I think it was noted with the GT350R front and BMR SP085 rear combo.

The GT350R's are 890 rear compared to the SP085 BMR's at 980. The difference is 90 mathematically but I do not know how or what that translates to or if it matters for me (based on being a beginner @ track).

Yeah, I'm not sure what difference a 9% increase would be in ride/handling quality. Probably not much of a difference overall for most people.

 

[BmacIL]

Question if you will. Balance was mentioned in an earlier post and I'm trying to understand what it was in reference too. I think it was noted with the GT350R front and BMR SP085 rear combo.

The GT350R's are 890 rear compared to the SP085 BMR's at 980. The difference is 90 mathematically but I do not know how or what that translates to or if it matters for me (based on being a beginner @ track).

Supposedly the GT350R rear rates are 914 lb/in, but Vorshlag's testing showed 890 in the working range of the spring. You need to look at the wheel rates, which is the effective rate at the tire, taking into account the motion ratio (wheel to spring, which is approx 0.48). WR = (MR^2)*spring rate.

The difference in wheel rates between GT350R and SP085 are not huge, but are enough to be noticed (226 lb/in vs 205). Stock PP rear is 168 lb/in.

What's meant by balance is this: the GT350R front wheel rate is 231 lb/in, SP085 are 226 lb/in. That's very balanced and very near the difference in weight distribution front to rear as well, which is imporant for the roll stiffness distribution. It also gives an excellent front/rear ride frequency ratio for ride (see page 10 in the spring rates thread).

 

[saf1]

Supposedly the GT350R rear rates are 914 lb/in, but Vorshlag's testing showed 890 in the working range of the spring. You need to look at the wheel rates, which is the effective rate at the tire, taking into account the motion ratio (wheel to spring, which is approx 0.48). WR = (MR^2)*spring rate.

The difference in wheel rates between GT350R and SP085 are not huge, but are enough to be noticed (226 lb/in vs 205). Stock PP rear is 168 lb/in.

What's meant by balance is this: the GT350R front wheel rate is 231 lb/in, SP085 are 226 lb/in. That's very balanced and very near the difference in weight distribution front to rear as well, which is imporant for the roll stiffness distribution. It also gives an excellent front/rear ride frequency ratio for ride (see page 10 in the spring rates thread).

Thank you.

I was not trying to min or max anything but has I continue to re-read the thread just trying to learn. So thank you for your time and clarification. It helped a lot.

 

[BmacIL]

Thank you.

I was not trying to min or max anything but has I continue to re-read the thread just trying to learn. So thank you for your time and clarification. It helped a lot.

Happy to help

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