BMR Handling springs installed (revised version)

[Bluemustang]

On the topic of a softer rear sway, if you happen to have the bar from the FRPP kit, you can try that. I really don't know how they compare to BMR, just a freebie idea.

Unfortunately I don’t. I didn’t buy the whole FRPP track kit, just the springs and shocks separately.

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[Bluemustang]

Well tonight I got an extended drive in. Went to see my girlfriend, as ya do... on Valentine’s Day of course... she lives about 50 mi from me so.. lotta highway driving. But I digress...

More impressions from highway driving:

- On the highway in general, it rides like a DREAM. IMO coming from the FRPP progressive springs it is NIGHT and DAY difference.

- It FEELs much smoother. Over surfaces with many bumps, wavier pavement: it basically glides over them. Previously it would feel unsettled. Not anymore.

- More composed. Over surface changes, highway expansion joints, it feels composed and settled. Even over the worst of expansion joints it is not bad.

- Extremely firm. The car feels flat just as it does driving around town. But firm as in, you feel the road and reaction to it are quick and noticeable. Imperfections are felt through the chassis and a lot of times into the back of the seat. Yet it is not jarring. It is just feeling what’s there. It isn’t overly harsh. The dampers have a lot to do w/ this I feel. It helps the car “glide” and feel more or less supported.

- Steering. Noticeably improved. My alignment settings are almost exactly the same as I had before the switch and I did that purposely. The steering feel noticeably improved by comparison. It feels much much less “notchy” as it did before. Steering feels lighter and curves feel more direct it’s hard to explain why. I feel like I am feeling less tramlining as well. I may have to drive more to confirm that, but I am correcting the wheel MUCH less so far. I could drive now easily most times with one hand for a little while and feel confident which was not the case before. Still feels very responsive maybe even more responsive. But a little more stable? Little less twitchy? Hey it doesn’t overhaul the steering BUT point is noticable difference for sure.

- Feel at higher speed. Way better. Driving at 80 or 85 it feels very confident and planted, on or off throttle (which was an issue previously). Tonight at one point I was cruising at 85... and the car is like come on gimme more this is nothing.

Other notes:

- I do not feel the negative NVH of the RLCA bearing anymore. At highway speeds the quick reactions of the rear are much better controlled.

- I have not “really pushed the car” much yet. But today I did push the envelope a little bit and kept on grinning.

- Braking, acceleration, on/off throttle, braking or accelerating while turning/changing lanes, downshifting. In all scenarios it feels like a significantly more stable car. I predict when I really start pushing the limit on this car it’s not gonna disappoint. But we’ll see.

- One thing is known at this point. Ride quality and handling feel both- are MUCH better and it’s not even close. I was afraid of a worse ride quality and that I’d have to sacrifice that for a better handling feel. I was wrong. It’s surpassed my expectations at this point. I’m shocked by how good the ride quality is, considering the significant IRS mods I have. They contribute some NVH but this is a ride that I want.

 

[Rebellion]

Progressive = better ride...mythbusted!

Glad you're loving the setup. I also had my fingers crossed about harshness when I first put it, turns out to be quite a good ride. I think the dampers have quite a lot to do with it, for instance, I feel like the C6G SS has softer springs than ours, but it is harsher (it seems, but not too bad for street). Can't quite do the analysis on different platforms and asymmetric damping, but I speculate it's because our shock/spring interaction is closer to critical.

 

[Bluemustang]

Progressive = better ride...mythbusted!

Glad you're loving the setup. I also had my fingers crossed about harshness when I first put it, turns out to be quite a good ride. I think the dampers have quite a lot to do with it, for instance, I feel like the C6G SS has softer springs than ours, but it is harsher (it seems, but not too bad for street). Can't quite do the analysis on different platforms and asymmetric damping, but I speculate it's because our shock/spring interaction is closer to critical.

Yes. I came to this same theory about the progressive springs after awhile of driving on it. Progressives are for the birds. The goal is to improve handling, while also keeping the ride more comfortable, but it fails at doing that. There may be some better options for progressives but as far as the FRPP springs are concerned, it's harsher than it needs to be and can ride a lot worse in certain instances.

I agree. I feel like the dampers have a lot to do with the ride quality. The springs seem to be working more so in harmony with the dampers. It doesn't feel overly springy or overly damped. On my first setup - SP080s and Koni shocks, it felt like almost all shocks and the springs weren't allowed to do it's job freely. On the FRPP springs/shocks, it felt more springy and like the dampers were having trouble coping with the changing rates.

I have a feeling the Konis would work well with these springs too, however, I do feel like the Ford Racing shocks are a better match as far as ride quality is concerned. The Ford Racing shocks seem to be tamer, probably on the compression side of things, although I don't have the data to back that up so I could be wrong.

 

[BmacIL]

Progressive = better ride...mythbusted!

Glad you're loving the setup. I also had my fingers crossed about harshness when I first put it, turns out to be quite a good ride. I think the dampers have quite a lot to do with it, for instance, I feel like the C6G SS has softer springs than ours, but it is harsher (it seems, but not too bad for street). Can't quite do the analysis on different platforms and asymmetric damping, but I speculate it's because our shock/spring interaction is closer to critical.

Probably the opposite actually, but more to do with the rebound/compression differences. High rebound with not enough compression leads to a harsh ride, as gravity will start coming into play on the down stroke.

 

[Rebellion]

Probably the opposite actually, but more to do with the rebound/compression differences. High rebound with not enough compression leads to a harsh ride, as gravity will start coming into play on the down stroke.

This is the part of the analysis where I can't process quite yet...mental model can't deal with asymmetry in compression/rebound rates. Maybe EE are too used to think in the frequency domain and not in the time domain :cheers:

 

[Bluemustang]

I had to drive into the city today for work where the roads are bad. This was the situation where I’d say it’s a little uncomfortable. It can be a little harsh on the worser of roads.

That being said, it’s not any more harsh than before. And it’s not that bad. But for some people it probably wouldn’t work for them. I wouldn’t necessarily choose this if you lived IN DC or NYC or some place like that where the roads are ripped up and patched all over. Not unless you’re willing to deal with some considerable NVH at times. But it’s not bouncing around or anything and it’s not sending me bouncing in my seat. If you hit some bad potholes or patchwork, yeah you’ll feel it.

I don’t drive in Bethesda or DC or wherever that much anyway. And the roads in the suburban area I live around the roads aren’t very good and I’m very happy with how it rides. But on the worst of roads, yes it is a negative. But IMO you shouldn’t own a sports car or be modifying your suspension if you live and drive mostly in downtown city areas where roads are awful and you care a lot about soft ride quality and no NVH. You’re not gaining any benefits from modifying your suspension in those conditions.

On another positive note, it seems to handle very well so far. Turn in feels more direct and cornering feels very good. I did some carving down some back roads and the car felt like it had a lot more in it.

 

[BmacIL]

Yeah these rates aren't going to be fun on a bad road. Anything up to that is completely fine though.

 

[Bluemustang]

Yeah these rates aren't going to be fun on a bad road. Anything up to that is completely fine though.

I agree. Every other situation it rides very nice.

 

[Bluemustang]

I am definitely noticing what I feel is oversteer. I’ve had the back end come around me in a few instances. And a few times I’ve felt the rear end skipping when going around a corner. I encounter bumps and what feels like wheel hop. I am thinking the rear sway bar is too stiff comparatively to the front as BmacIL said and maybe just too stiff for the high spring rate in general. I’m hoping it isn’t the rear shocks not having enough rebound.

I do want to try stiffening the front bar to even out the balance. Maybe this will help keeping my rear tires on the ground better in these situations. Despite this I’m overall very pleased with how it handles and thinking some sway bar tuning might improve things.

 

[BmacIL]

I am definitely noticing what I feel is oversteer. I’ve had the back end come around me in a few instances. And a few times I’ve felt the rear end skipping when going around a corner. I encounter bumps and what feels like wheel hop. I am thinking the rear sway bar is too stiff comparatively to the front as BmacIL said and maybe just too stiff for the high spring rate in general. I’m hoping it isn’t the rear shocks not having enough rebound.

I do want to try stiffening the front bar to even out the balance. Maybe this will help keeping my rear tires on the ground better in these situations. Despite this I’m overall very pleased with how it handles and thinking some sway bar tuning might improve things.

That type of thing (skipping mid-corner) is just lack of compliance. You need a softer rear bar and more rubber. It's gotta roll some to let the tires work. I know my car in the snow feels like I'm on solid welded shocks & struts with no travel sometimes :lol:

 

[Rebellion]

Apart from fore/aft sway balance, the only other way around this (that I can think off) is staggered tires...bad solution :doh:

 

[Bluemustang]

That type of thing (skipping mid-corner) is just lack of compliance. You need a softer rear bar and more rubber. It's gotta roll some to let the tires work. I know my car in the snow feels like I'm on solid welded shocks & struts with no travel sometimes :lol:

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.

I have several options: GT PP, GT350, GT, etc. I’m hoping any of those will be soft enough to allow the rear to roll some as you mentioned.

 

[BMR Tech]

Why don't you disconnect the rear bar and see what happens?

 

[BmacIL]

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.

I have several options: GT PP, GT350, GT, etc. I’m hoping any of those will be soft enough to allow the rear to roll some as you mentioned.

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.

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