fc front sway bars bad?
 

So I was told by a few people telling me the fc front sway bar design was bad. But no one really explained. I bought my car with an st bar, I heard they bind. The bar or the endlinks? I got adjustable endlinks, they seem ok. Anyone care to explain why people are trying to redesign the factory sway?

The front bar is not bad, you need the bigger front bar to get the car to handle well. It is the endlinks that can bind. I went to the mazdatrix adjustables that are heims on both ends. Even with the bar relocated, they work smoothly. The Racing beat endlinks I had on the car worked ok with the bar in the stock position, but bound up when I relocated the sway bar.

I think S5s had plastic front endlinks? I recall they are different than the S4 versions.

I still have my racing beat ones if you want them.

Mazda has an SAE paper on the body design of the FD, and they used an FC to start with, they found that the front sway bar actually bends the body, if you look at it from the top, its pretty obvious that the bar is putting a lot of leverage on the weakest part of the body...

the S5 has plastic links, but it has a spherical bearing on one end, so it can move in two planes, unlike the S4 ones.

Josh18_2k originally said the ST bar had binding issues at the extremes of travel. I think this was an issue with just that bar, but I don't know the specifics. maybe it wasn't exactly straight in the mounts or hit something? it might have been due to the adjustment holes not being inline with the mounts.

Yes... it's easy to see that since the FC bar is in front of the wheels it has a huge lever arm on the frame rails in which to twist them. This is the reason the FD sway bar (and every other sway bar I've seen) is positioned behind the front wheels.

In the study they removed pieces of the car to see how much they added to the stiffness of the body. the sway bar reduced torsional stiffness by -35% and bending stiffness by -5%.

Here is a chart from that study:
https://cimg7.ibsrv.net/gimg/www.rx7...ea372afd07.png

all of that being said. 99% of people run sway bars without issue. it's not that big of a deal. You're much better off running a sway bar than you would be running no bar and stiffer front springs than your mediocre front dampers can handle... (or worse yet, running no bar and not increasing your front spring rate)

Agreed.

Yes, I believe Josh's problem was related to the relocation of the swaybar for the v8 and the endlinks, or the sway bar was hitting something motor related. I dont remember specifically. I had a similar problem with my RB bar, and had to go with Mazdatrix endlinks with heims on both ends. No issues for me after switching the endlinks.

I ran no front sway bar for a while just to see what it was like... alot of body roll.
It was unsettling to me even in everyday traffic.

I have the mazdatrix links and they are really nice.

the FD is still in the front, they just mounted the bar on something flexible... Rx8, miatae and 2016 mustang have the bar in the front too, i didn't look at any other cars, should mention.

as an aside the mustang suspension is quite crazy

i think the moral of the story is to not run a GIANT bar.

Are you talking about the 2015 mustang? If so.. Yes.

yes, and yes!

For a second there I thought you had said "strut bar" and I was trying to wrap my head around how a strut tower bar could make a car have LESS torsional stiffness.

My car is now lifting the inside front wheel.. so time to revisit sway bars. I may have outgrown the RB bar on the car. I am looking into custom speedway bar setup. I don't know that I want to go higher with my front spring rates, or my rear rates as the car is working pretty well. I have no bar in the rear now, which is probably my problem in the situation below.

Attachment 603583

This one looks extra fun.. explained the tire rub marks up in the rear inner fenderwell..

Attachment 603584

Do you have enough droop stroke in the front? Maybe using a helper spring to push the tire down would help.

That's full droop. I don't need any helper springs.

Try the thinnest stock rear bar?

But if the car is working fine, I wouldn't worry about it too much as it's not a drive wheel.

Yea it does not do this all the time, just on select corners. The car is working really well now. I have had a rear bar on it with the V8 in it because I worried about it reducing drive off the corner. It rotates well, maybe I'll try a small stock rear bar just to see. All I have is the RB rear bar, which is probably too big.

My car doesn't lift wheels anymore.... :gwink:

a splitter might fix it :)

Do you have a clutch pack LSD? You need one.

Nope, a Detroit TrueTrac (Torsen).

I wouldn't say you necessarily have a problem. My 240Z (2300 lb., 240ish rwhp) would lift the inside front as well once I got it dialled in. For sure a rwd car with big power/weight is going to have to have somewhat forward-biased roll stiffness in order to put the power down on corner exit.

Agree on both points :D I would try the thinnest stock bar for grins, and you can easily disconnect one of the end links at the track if it doesn't work.

That's what I do with my FD. It has factory '94 rear bar and at more oversteery tracks I just disconnect it.

If TrueTrac is working for you I wouldn't worry about it. But if you are getting inside wheelspin over curbing or any other weirdness, yeah, you might go clutch-pack. Ultimately a good ramp/Salisbury style clutch type will allow more setup leeway (more tolerant of more rear roll stiffness) as well as bounding over curbing while putting power down, without requiring a lot of static breakaway torque.
I ultimately went OSGiken in place of the T2R Torsen I had in my 8.8 diff.

I agree I don't really have a problem now. The car is working really well as is. Up to this point most changes have been improvements, and I have not jumped the fence yet to where something made the car worse, So I am going to continue to tinker.

I am very happy with the Truetrac, Personally I won't go back to a clutch diff. Part of why I DONT want a rear bar is for exactly that reason - I get no inside wheel spin now, on or off curbing. I don't *think* a stock rear bar would hurt me, but at the same time I don't feel like I need the car to rotate any better, and putting a rear bar on just to plant all 4 tires on exit does not seem like a good trade off, but who knows, maybe it will work better.

As Mike said, the solution is probably a front splitter. I may be to the point of diminishing returns without an aero package.

i'll sort of third this.

before you go buy a bigger bar, plug your setup into any suspension spreadsheet, and compare the bar you have with the bigger one. usually its a small enough difference to not really warrant a bigger one.

I'm going to 4th this from my experience with a 3 wheeling FC (rear bar removed).

With the rear sway bar it would 3 wheel by picking up the inside rear around really tight features (auto-x) or over crests in the road on hillclimb, so I ditched the rear bar and then in addition later went to rear shocks with 1" more travel and zero rate springs to assure that was droop travel.

I liked the FC picking up the inside front a lot more than the inside rear.
It was only on throttle on situations where the grip was there and the weight transferred back.
You could feel the steering get light and mild understeer come in that basically just helped you guide the car along the racing line off the apex.

I hate hate hate understeer before the apex where it messes up your line, but I have found I don't really mind mild power on understeer after the apex. You can drive rough if you want the oversteer after the apex or just set-up for max acceleration of the apex and get the "half-ass wheelie" action on exit.

I had the FD torsen. If I had a good multiplate clutch rear then maybe picking up a rear wheel wouldn't have been as bad.

This thing never understeers before the apex, on or off throttle. After apex it is neutral or slight to moderate oversteer, and that is throttle dependent. It has not lifted a real wheel, and with 700 lb front springs, I don't know that it will... well it might in an AutoX, but I don't do that with the car.

Thanks for the sanity check here guys.

I have seen quite a few well set up and fast fox body mustangs do the same thing. That inside front tire isn't doing much at that point anyway. If you do decide to try a rear bar you could always dial in a little more rear toe in to get the stability and traction back. But I wouldn't mess with something that is working well for you. Plus it makes for great trackside photos!

I am leaning towards not messing with it much, as the side effects are mostly undesirable. I know the difference between the inner front rolling on the ground with no weight on it, and in the air is not much.

I was secretly excited to change the front bar because it will drop some weight.. I still may switch it over for a speedway style bar of a similar rate simply for some extra adjustability to fine tune things.