BMR Handling springs installed (revised version)

Bluemustang · Feb 19, 2018

BmacIL said:
Try two things before you try another bar:
1. Keep the rear bar as it is, and go full stiff on the front
2. Disconnect the rear bar as Kelly [MENTION=9985]BMR Tech[/MENTION] suggested

See which one directionally feels the best. Drive each for a couple days to get a variety of situations evaluated.

Thanks. I will try #1 first and then #2.

Roadway 5.0 · Feb 19, 2018

Bluemustang said:
The question is: which rear bar is the right choice. I think and I may be wrong, the BMR rear sway bar is 60% stiffer than stock, whether that’s GT or GT PP I do not know.

What tires are you running with the current winter temperatures in Maryland? This can make a huge difference. And yes, go full stiff front, full soft rear and see what happens before you spend more money.

BmacIL · Feb 19, 2018

Bluemustang said:
Thanks. I will try #1 first and then #2.

Yeah, and when you run #2 put the front bar back to full soft.

Bluemustang · Feb 19, 2018

Roadway 5.0 said:
What tires are you running with the current winter temperatures in Maryland? This can make a huge difference. And yes, go full stiff front, full soft rear and see what happens before you spend more money.

Summer tires 235/50/18

Roadway 5.0 · Feb 19, 2018

Bluemustang said:
Summer tires 235/50/18

There it is. Definently don’t waste your money exchanging parts at this point; your suspension is stiff and your summer tires just can’t keep up with winter temps present. Still loosen the rear bar and stiffen the front and you’ll likely see an improvement. But your best results will occur when the ambient air temps rise.

BmacIL · Feb 19, 2018

Roadway 5.0 said:
There it is. Definently don’t waste your money exchanging parts at this point; your suspension is stiff and your summer tires just can’t keep up with winter temps present. Still loosen the rear bar and stiffen the front and you’ll likely see an improvement. But your best results will occur when the ambient air temps rise.

That's some of it. If the car had balanced roll stiffness it would slide, not skip at one end.

My winter tires are 225/55R18 and they just slide progressively when pushed hard. Even when I had my summers on in the cold fall days (30-35 F) before changing over, no skipping.

Roadway 5.0 · Feb 19, 2018

BmacIL said:
That's some of it. If the car had balanced roll stiffness it would slide, not skip at one end.

My winter tires are 225/55R18 and they just slide progressively when pushed hard. Even when I had my summers on in the cold fall days (30-35 F) before changing over, no skipping.

Agreed. Adjusting his bars and hitting warmer temps is needed.

Bluemustang · Feb 19, 2018

BmacIL said:
That's some of it. If the car had balanced roll stiffness it would slide, not skip at one end.

My winter tires are 225/55R18 and they just slide progressively when pushed hard. Even when I had my summers on in the cold fall days (30-35 F) before changing over, no skipping.

Yeah, what I am getting it skipping. And I've been using these tires for awhile and throughout this winter so far. The change in spring rate in the rear is the significant change in this equation.

Both bars are already at full soft. So as you said, my first test is to put the front bar at full stiff. Although what I assume would happen then is the front will skip and the rear will skip less or not at all. So I am thinking that really what I need is a much softer rear bar to take out some of the roll resistance present in the rear.

What I am hoping is not the case - is that the rear spring rate is just too high to deal with bumps mid corner on the street. That would put a big frown on my face.

I love the feel of the car in general now compared to before. I just didn't like the feel of the progressive springs, even though it did corner well and deal with bumps in corners very well. The vague weight shift and vague handling feel in many situations - I did not like.

BmacIL · Feb 19, 2018

Bluemustang said:
Yeah, what I am getting it skipping. And I've been using these tires for awhile and throughout this winter so far. The change in spring rate in the rear is the significant change in this equation.

Both bars are already at full soft. So as you said, my first test is to put the front bar at full stiff. Although what I assume would happen then is the front will skip and the rear will skip less or not at all. So I am thinking that really what I need is a much softer rear bar to take out some of the roll resistance present in the rear.

What I am hoping is not the case - is that the rear spring rate is just too high to deal with bumps mid corner on the street. That would put a big frown on my face.

I love the feel of the car in general now compared to before. I just didn't like the feel of the progressive springs, even though it did corner well and deal with bumps in corners very well. The vague weight shift and vague handling feel in many situations - I did not like.

It's not, don't worry.

Roadway 5.0 · Feb 19, 2018

Bluemustang said:
Yeah, what I am getting it skipping. And I've been using these tires for awhile and throughout this winter so far. The change in spring rate in the rear is the significant change in this equation.

Both bars are already at full soft. So as you said, my first test is to put the front bar at full stiff. Although what I assume would happen then is the front will skip and the rear will skip less or not at all. So I am thinking that really what I need is a much softer rear bar to take out some of the roll resistance present in the rear.

What I am hoping is not the case - is that the rear spring rate is just too high to deal with bumps mid corner on the street. That would put a big frown on my face.

I love the feel of the car in general now compared to before. I just didn't like the feel of the progressive springs, even though it did corner well and deal with bumps in corners very well. The vague weight shift and vague handling feel in many situations - I did not like.

I’m sure you can find a fix with the parts you have, just hang in there. I run 880 rear springs with a massive rear bar on full stiff and a stock PP front sway and have zero issues even with 19 degree F temps (drove today like this actually).

Do you have any abnormalities in your alignment?

Bluemustang · Feb 19, 2018

BmacIL said:
It's not, don't worry.

I am tending to agree with you. I think my setup just needs a bit of tweaking.

If I had started this from the beginning with a set plan in mind like I have now, I'd have done one thing at a time, with bars coming last. But because I did a whole bunch parts of parts at once, without testing one at a time, and without a clear direction and understanding, I've had/am having to backtrack a little and re-tweak.

As Kelly [MENTION=9985]BMR Tech[/MENTION] said, my perseverance in this case will likely be rewarded :clap2:

Bluemustang · Feb 19, 2018

Roadway 5.0 said:
I’m sure you can find a fix with the parts you have, just hang in there. I run 880ft/lb rears with a massive rear bar on full stiff and a stock PP front sway and have zero issues even with 19 degree F temps (drove today like this actually).

Do you have any abnormalities in your alignment?

Will post alignment specs this afternoon :cheers:

Thanks buddy!

Bluemustang · Feb 20, 2018

Hey [MENTION=10281]BmacIL[/MENTION]- how much do the sway bars add to the effective wheel rate? According to BMR’s website the front bar on full soft is 28% stiffer than the stock bar and the rear on full soft is 63% stiffer. If I go to full stiff on the front, it will be a 70% increase over stock.

If I recall, sway bar rate is additive to the spring rate isn’t that right? I’m trying to figure out if there is an optimal rate (on paper). I know I know - go and try it. I just want to understand the theory behind it before I begin.

Bluemustang · Feb 20, 2018

Alignment specs as promised.

Caster (L/R): 7.7, 7.6

Front Camber (L/R): -1.8, -1.8

Rear Camber (L/R): -1.8, -1.7

Front toe (L/R): 0.00, 0.00

Rear toe (L/R): 0.14, 0.12

Thrust angle: 0.01

BmacIL · Feb 20, 2018

Bluemustang said:
Hey [MENTION=10281]BmacIL[/MENTION]- how much do the sway bars add to the effective wheel rate? According to BMR’s website the front bar on full soft is 28% stiffer than the stock bar and the rear on full soft is 63% stiffer. If I go to full stiff on the front, it will be a 70% increase over stock.

If I recall, sway bar rate is additive to the spring rate isn’t that right? I’m trying to figure out if there is an optimal rate (on paper). I know I know - go and try it. I just want to understand the theory behind it before I begin.

It is additive but you have to keep in mind the motion ratio. The front is essentially the same as the front strut. The rear is pretty much at the shock mount, so it has a larger motion ratio (approximately 0.75) than the spring. Then you have to apply that torsional stiffness of the bar with those motion ratios to the wheel rate. There's no true optimal rate, as it depends on what the balance of the car you want. There are optimal ranges for them, but not specific points. I'd need more data about the body/chassis of the car to answer that question.

BMR Handling springs installed (revised version)

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