I'm posting this in the Racing & Competition section b/c I want to frame this within the context of Racing and Competition. I did search here where someone said a more aggressive front bar (combined with an aggressive rear Hotchkis bar) made the car feel "amazing". Another person said to remove the front bar.

What brought me here is that I came across an interesting YouTube video from Sheikh, the owner, of Fat Cat Motorsports titled "The Hidden Cost of Sway Bars". He's well known and respected in the Miata community. His message is that aggressive swaybars effectively "couple" the left and right side, severely limiting traction benefits of an independent suspension. I know the car in his example is RWD, but it seems that decoupling the front suspension on either RWD or FWD would be a good thing in terms of cornering traction.

Has anyone tried removing the front sway bar in competition, either HPDE/racing or autocross? What was the effect? More traction, but more body roll? More cornering traction, but more inside tire spin-up? Less understeer? I'll probably see for myself, but wanted to hear about your experiences too.

 

I'm reading a "Front Sway Bar Removal??" post from May 10 in the R56 Suspension section, but I'd still like to hear about your experiences. Looks like removing the front bar encourages aggressive oversteer, but it sounds like some of this is from those that haven't actually tried it. Maybe this weekend I'll disconnect the links and see how it feels.

 

Verdict after a 20 minute spirited trial on curvy back roads - I really like it and does not promote widowmaker oversteer as some have suggested. I'm running the H-Sport Comp RSB set on the middle hole. There's definitely more traction and probably less understeer with the front bar disconnected. I did experience a situation where the rear got loose, but I was intentionally trying to induce this.



I'll remove the bar completely and enjoy some reduced unsprung weight and more cornering traction for now.

 

thinking through this it's all about energy transfer and where it gets absorbed.


no sway bar = more body roll as the wheels are free to do what they are asked to do independently.. so the energy is going to letting the car move.


sway bar (or going bigger) = restricting the body roll.. so the energy is being directed into the tires vs moving the chassis..


which is more efficient in going around corners? If you follow any racing and see how tight the cars are sprung you would think tighter.. so if you are going through a chicane id think that no body roll is ideal when you are changing direction.. any body roll is just eating energy that you can use to turning the car. If you go over tight.. you are putting more energy into the tires which will eventually let go.


I have driven a mini back to back - hsport comp bar vs stock at tremblant a few years ago.. i was amazed how much more planted the rear end was with a bigger rear bar, but the physics says so.. less energy was being directed into letting the chassis move around.


other key point in disconnecting the front bar is what you are doing.. if you are doing tight autox where you want to turn very fast (lots of oversteer) then having no bar (more traction) up front would make sense.. but you do compromise energy going into moving the chassis around in that setup.. remember, there is no free energy! so you do make a compromise either way you go.


If you want to go deeper then you need to start changing your suspension geometry to optimize what you are doing. tighter bars will push energy through your tires more.. so you would need to add more camber to increase your traction\tire contact patch during a turn.


I think the main thing between front and rear sway bar is tune in how much body roll you want... AND tune the roll between front and rear for the overall balance.


* this was just off the top of my head from the experimenting i have done.. youd need to find a racing site for more depth on the topic.. suspension is a very complex balance of many parts moving in many directions, BUT you are only adjusting 4 little patches of rubber touching the ground.


phil.

 

Phil,

Thanks for the thoughtful response. I have two last autocrosses of the season coming up and I'm looking forward to trying this out. Definitely room for improvement and I hope to have made more progress by springtime for the new season. More aggressive springs, damping, and lowering are probably in the car's future.

 

np


seat time is always the best upgrade.. you can also do a lot of tuning with tire pressures and chalking your sidewalls..


seat time, mod, seat time seat time, mod (repeat)


oh.. and just have fun

 

I'm not sure what that guy was talking about with all the discussion of "energy transfer" but I'll try to explain how I see it. For starters, the few Minis that were nationally competitive in STX back in the early 2000s were running rear biased spring rates (higher spring rates in rear) and the base cooper front bar. So clearly they thought it useful to install a smaller front bar on the STX cars for auto-x purposes.

The whole point of stiffening springs/bars on a car is to manage the elastic weight transfer from side to side and therefore the roll angle. While you can do this entirely with springs and leave the bars out of it it's not really the best option on a production car. Pick springs so that elastic weight transfer is minimized and you start getting into natural frequencies that are far too high and will cause issues with bump compliance and therefore bump-related grip. Simply stated, one little bump will cause the car to go skittering off sideways. Therefore you have to choose spring rates that give you the natural frequencies you're looking for (front and rear can be different) in your car. Ideal natural frequencies will vary depending on the usage of the car and the surfaces you find yourself on. Not to mention you need shocks that can keep up with the wheel rates which in some cases (poor motion ratios) is difficult to come by or very expensive. If you can't manage roll with just the springs then you have no choice but to go with swaybars. This is why people say they're really a tuning tool more than anything else. You start with spring rates and then fine tune with swaybars. You use a swaybar to increase roll resistance at that end of the car.

So what's all this talk with roll resistance and why do I care? Your tires have a "happy place" where they work best. You want to lower the CG of the car as best you can (with shorter springs) and set up your tires so they are in their happy place static. This is why racers run large amounts of static negative camber. Strut cars (like the mini) lose camber (goes more positive) as the car rolls. Tires work best with a very small amount of negative camber (generally). So now you've got your car sitting and looking pretty and the tires are in their happy place (camber wise) and everything is good till you go around a corner and weight transfer starts to happen and the car starts to roll. The more the car rolls the further the tires get from their happy place and the less grip they generate. This is why swaybars are generally needed on production cars. They help keep the tires in their happy place when springs alone aren't enough.

So how do you use swaybars to tune the balance of the car (oversteer/understeer)? Generally speaking a stiffer swaybar increases the effective spring rate of the outside tire in a turn by coupling the inside and outside wheels. Therefore your wheel rates get very large and the wheel loses grip which makes that end of the car loose. So a stiffer rear bar would make the back end rotate better (oversteer) while a stiffer front bar will make the front end push.

One advantage of a smaller front bar than what might be ideal for the overall car balance is what you've mentioned. Traction on corner exit. Because the front wheels aren't coupled by a large bar the springs can do their job better and keep the tires squished into the pavement where they are generating grip while you're trying to accelerate. So generally speaking a smaller front bar will increase traction on corner exit and reduce inside wheelspin (provided you're not running a lot of rebound in your front shocks). Or you can just install a diff

Sorry if that's clear as mud. It all still confuses the hell outta me

 

Wow, awesome info. I just had a Quaife TBD, NM motor bushing, and Powerflex polyurethane lower A arm bushings installed last weekend and I'm looking forward to my next autocross in a couple weekends. My next HPDE won't be until the spring unfortunately. I need to find a happy medium between track and autocross setup.

Thanks for the info about starting with the springs and then using the sway bars for tuning. I plan on consulting with FCM over the winter about spring rates, shock valving, etc. I might see if the Justa bar is a little smaller than the S bar. I'd also upgrade to poly front sway bar bushings too while I'm at it.

 

I'll be trying it at the next track event the 19th and 20th of October.

I had been thinking about it and decided to try it after finding out the fast HC guys run with no front bar.

I would caution that this may lead to spring breakage if you are using stock springs or spring rates. To be safe you need about a 450 lb/in spring rate minimum.

 

Im watching this thread since me and a few others live in the country are were the population is extremely low. there is a 1 mile area of road way that allows us to keep going in circles with several areas of right and left turns. worst that can happen is we slide into the corn fields. I have had quite a few experiences with the rear of the car kicking out when trying to drive smooth thru the corner. I usually brake slightly going in and accelerate thru the apex of the corner. The car is driven on the street quite often so its not a track car. but it is just a toy so if it is more racey that's fine. I am currently looking into installing polyurethane bushings in the front and a torque arm. any direction as to how to get this back end to stick then work the rest of the car to it to stick better as a whole ? Im not familiar with working suspensions. I build motors and drive. 2008 r56 hardtop

 

Try dialing in more negative rear camber for more rear grip.

 

v10climber beat me to it....

I just installed Powerflex front lower control arm bushings and NM torque arm inserts.

If you want to increase rear traction you can try to dial in more negative camber. If you lower the car you'll automatically see more negative camber at the rear - usually too much. For more rear camber adjustment a lot of people install adjustable lower rear control arms. You can install the upper arms as well, but it's not necessary for simple camber adjustments. Note that if you happen to install a stiffer rear sway bar this will stiffen the rear, encouraging the rear to slide if your inputs ask it to do so.

Good luck. Removing the front bar isn't for everyone, but I'm having fun experimenting. My next autocross is this weekend, so we'll see how it goes.

 

Gonna replace all the bushings and add adjust sway bar end links in the next couple weeks. Referencing the control arm bushings.... What is the consensus about the alta positive steering parts ?

 

Looking more closely at what it takes to remove the FSB...yeah, I'm not doing that any time soon. It was a cool experiment, but I'll just reconnect the SB and live with it. Or maybe I'll cut off the end of the bar and slide the dang thing out...or not.

 

Or take the end links off. Try it with out it. Replace the links with the adjustables

 

Ideally, I'd remove the FSB altogether and add lateral stiffness through increased spring rates and damping to match.

 

The Alta PSRS wears quickly and starts making tons of noise. It sucks. Like many Alta parts.

 

unwanted noises are NOT wanted, neither is wear. SO ! I ordered the polyurethane bushings for the entire front entire.

 

Back in the early MINI years, 03-06 quite a few people running in stock classes ran a "just-a" FSB since it was a factory part and they had to have a FSB on the car.. Alot depends on what you are doing with the car. A good Auto X set up may not be too good on a real road course and vise-a-versa... Alittle loose at 25-45MPH in a parking lot is good for rotation, compared to 100MPH at Road Atlanta etc.

 

Not completely off topic...

Does anyone know what the various R56 front bar rates are anyway???

Lots of info exists for the rear bars, but less so for the front.

 

I race a BMW E30 (front engine/RWD). It's common to not run a rear bar due to the fact that many tend to lift the inside rear in high load corners. The saying in racing is "loosen the end you want to grip," not tighten the end you want to slide.

I haven't tracked the MINI more than maybe 10 days at NHMS, 8 days at Team O'Neil rally school with the Audi club and I just did my first Ice Race with with BMW club this past Sunday, where I won class G (FWD ice tires) by 4.2 seconds, taking 5th over all. I'm going to try disconnecting it for Sunday's Ice Race and see if it helps. I'll post the results and my opinion after the race.

 

Unfortunately, I didn't make it up to the race today (long story). If we race again next week I'll post my opinion and the results.

 

I've had the front sway bar removed from the car for about three months now. I've done one DE and two race weekends. The car is better on corner entry and doesn't push on corner exit near as much.

You need a minimum 450 lb/in (8K) spring rate. You cannot do it with barrel/beehive springs - you will break them.

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I'm running Swift type R springs. If my memory serves me correctly, I believe they're around 550 lb/in for the fronts. They also have fewer coils, which means more travel. I'm assuming these will be okay, but would like to hear your thoughts.

 

If they are Spec R springs you can't disconnect the front sway bar. Too soft barrel springs.

http://www.swiftsprings.net/products...ct/spec-r.html

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