THSCC Forums

Sometime back, Sam Strano replied to a question of mine in SCCAforums about the subject of the front bar. Here is his reply:

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Current stable:
2019 BMW M2 Competition slicktop 6MT
2011 BMW M3 sedan slicktop 6MT
2007 BMW 328i wagon (slushbox for now)
1975 CanAm 125MX2

That's interesting Chuck. Sam would certainly have a good idea of what works and what doesn't.

Wheel spin it is...

Jim

The "problem" with sedans is that they have a relatively high center of gravity compared to the amount of grip their suspension can generate with R tires.

Considering that the front and rear tires are off the ground (due primarily to weight transfer which is a function of cg height and grip) there is very little he can do in Stock. Maybe less shock rebound and relative front/rear bar stiffness changes can get one tire down (if there is enough droop travel) but how much additional grip will the weight of the wheel/tire assembly and some part of the suspension really add? I don't want to even think about even more grip on a transition intensive course . . .

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Dick Rasmussen

FS 50 2018 Mustang GT

The solution is an S2000.

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Has no responsibility whatsoever.

I told you your BMWs all have too many doors!

Now maybe your family will stop making fun of my 325Ci and the 944!

Fixed it for you.

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Dick Rasmussen

FS 50 2018 Mustang GT

Want to trade some weekend Dick? I've actually driven a Formula Ford before...

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Karl S.
2014 Baby, 2014 House, 2013 Ford Focus ST, 2013 BMW 328i, 1994 Mercedes E320
(Insert passive aggressive signature line here)

I'm sure Sam had better shocks, then. You need one or the other, at least. But given what Sam said, I'd try shocks next as you had planned. I'd have to wonder what size the bar he settled on was, too...


--Donnie

The rear wheel is not off the ground -- not even close. The picture just looks that way in the cut down version on my site. Looking at the original 6Mbit picture shows good contact. It actually had plenty of grip in this section of the sweeper. Nowhere on couse is the rear off the ground. Powering out of this sweeper I could use ~80% throttle with modulation until I could start opening up the wheel and then could get to full throttle. The traction situation isn't really that bad except in slow speed tight corners where you have to (or want to) use 1st gear.

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Current stable:
2019 BMW M2 Competition slicktop 6MT
2011 BMW M3 sedan slicktop 6MT
2007 BMW 328i wagon (slushbox for now)
1975 CanAm 125MX2

Yeah, while I don't disagree that the biggest bar available can improve grip on many cars (like Donnie's STi), once the front bar is big enough to lift the inside front tire, an even bigger front bar isn't going to help. Any front bar stiff enough to lift the inside front results in the same amount of body roll (=same camber on outside front wheel), the bigger bar will just lift the inside front tire higher. Once the inside front begins lifting, the car's body rotates around the diagonal axis between the outside front and inside rear tires, at that point the only way to improve steady state (i.e.: sweeper) grip is to lessen the distance the outside rear spring compresses (squats), which can only be accomplished via stock-illegal changes (increased rear spring rate via stiffer rear springs and/or stiffer rear sway bar).

I'd bet the reason the mega-bar is beneficial on Donnie's car is because the STi is heavily weight biased to the front (61/39), it's unlikely to lift a front tire with anything less than the biggest bar available.

As for the E46, increasing rear compression (and rebound) damping definitely should help as it would delay the transition to full lean/roll. The inside front will still lift the same amount in a steady state (sweeper) turn, but it will take a little longer to get there.

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Keith Q.
2008 Top Gun
http://www.youtube.com/watch?v=KmX8XuZ_DCo&NR=1

Sam mentioned the bar was an H&R, which would be 27 mm with two stiffness adjustments (and he apparently added a third/softer adjustment). I believe Chuck's (Turner Motorsports) front bar is the same spec as the H&R - 27 mm w/2 adjustments.

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Keith Q.
2008 Top Gun
http://www.youtube.com/watch?v=KmX8XuZ_DCo&NR=1

Keith, the only thing I'd point out is that the Peterson Spyder was tested with seven different swaybars from "slightly bigger than stock" all the way to 32mm. It got better with each bar size increase. Your weight balance theory certainly doesn't hold true in that case, since the car was much lighter and exactly the opposite in balance as my STi. Sure, now we're talking mid-engine and all, but...

And it did have pretty stiffly valved DAs on it, too.

Also, while I trust Sam up to a point, he almost never uses anything but off the shelf Koni SAs (with stock valving). He's then such a good driver he gets the car as good as it can be with those shocks and then drives around the rest of the problems. While I may not be the guy to do it, I do think in some cases you could get a better car than what *he* considers the optimum setup with better shocks. Even if it doesn't end up ultimately faster, it would end up easier to get to that same limit that he's finding with his incredible driving skill.

You're probably right that a bigger bar without shocks won't do *that* much for the car. I don't buy the theory that it will "just lift the inside front higher" and do nothing else, but I do think it at least needs shocks and likely can use more bar. I'd start with shocks, and stock valved Konis will probably yield a noticeable difference. Enough that Chuck will probably just stop right there and be *really* happy (and maybe even consider less bar, for *those* shocks).


--Donnie

To clarify, my statement was that a bigger bar would offer no additional grip when a smaller bar already lifts the inside front tire. Did Eric's Spyder lift the front tire with any front bar other than the biggest?

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Keith Q.
2008 Top Gun
http://www.youtube.com/watch?v=KmX8XuZ_DCo&NR=1

I pretty much agree with you that once that wheel is off the ground it doesn't have any additional impact on weight transfer, but I wonder if the bigger bar may cause the inside front to lift sooner (transferring weight to the rear faster) than a smaller bar?? And that might help for some cars?

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Richard Casto
1972 Porsche 914
2013 Honda Fit Sport
2015 Honda Fit EX
http://motorsport.zyyz.com
Money can't buy happiness, but somehow it's more comfortable to cry in a Porsche than a Kia.

I'm not sure I totally buy that argument. I tend to think there are way to many variables at work to make blanket statements like that and I've definitely seen instances where more bar and the resulting higher/sooner wheel liftoff makes the car faster. I'm sure Chuck's BMW is way stiffer than the flexi-flier chassis I was dealing with so it probably reacts differently but the only way to know for sure is to experiment.

And by experiment, I don't just mean bolt stuff on and see how it reacts. As Sam noted, you really need to adjust other things to regain any lost balance and that is often overlooked. If you run out of adjustments to regain lost balance within whatever parameters/rule set you are dealing with, it may be time to take a step back.

I tend to agree with Donnie's assessment that perhaps Sam didn't explore every option and he is perhaps very good at driving around issues but only he knows for sure. Driver feel and confidence definitely plays a huge role in all this.

After reading a couple of Chuck's responses, if he is only having big trouble with wheel spin in first gear, it's probably not worth chasing. If the car puts down power well in second gear and seems balanced for the moment, I'd stick with the shock upgrade route for now.

Jim