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Installed super fat sway bars, now car is a slidey boii
Wanted to modify my car, and make it "my own", you know how it goes...
Bought the car stock with Firehawk AS tires, stock size. Installed the Eibach sway bar set (25mm front, 19mm rear, both tubular) with adjustable endlinks. Both sway bars set to most tame, and set endlinks to same length as the OEM links. And now the car is very slidey... I was anticipating some changes in the behavior, obviously, and was driving very cautiously until I could find the new limits of the suspension, but wow. Seriously caught me off guard in a potentially dangerous situation. Shortly after that incident, I tested it in a more controlled environment. I went around a 90deg turn (usually a 12mph turn in a regular car, I suppose) around 18mph and the rear end still knocked loose and got wide before the aids stepped in. I was shocked. You could be driving this car in a rather tame fashion, and the rear end would feel like it's on ice skates. Other factors: I think it was like 45-50F temp. The rear tires have deep tread. Local roads are trash, and 1st time it broke loose, likely had lots of road debris. In some ways, it almost seems 'worse' to drive than with stock sway bars. Previously, you had to try to break the rear loose. Either take a turn with significant speed, or slam into 2nd gear around a parking lot intentionally trying to drift. I don't want to play the "I installed race car parts, but I don't want race car consequences!" card, but what are my options here? Better tires? Stiffer springs/dampers? |
This car doesn't need much rear bar. I have been hunting for a used stock rear one, on a perrin 16mm now.
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Now that I have experience with it, I would say the 19mm Eibach bar is excessive, but that's the only size Eibach offers, and they come together in a kit, so I thought they would be appropriate. I suppose the proper scenario is the car has a suspension setup that can justify (and use) that much stiffness in the rear. Not sure if I should build the rest of the car to match, or install smaller bar :bonk: |
More aggressive tire would help. Even on my 200TW setup I personally don't like a lot of rear bar.
These are the specs Perrin gives on their bars. I know you are on the Eibach but this will give you an idea of the difference in stiffness based on diameter. I'd put your stock rear bar back on for now. PERRIN 16mm Bar Hole #1 30% Stiffer than 14mm OEM bar PERRIN 16mm Bar Hole #2 65% Stiffer than 14mm OEM bar PERRIN 16mm Bar Hole #3 116% Stiffer than 14mm OEM bar PERRIN 19mm Bar Hole #1 150% Stiffer than 14mm OEM bar PERRIN 19mm Bar Hole #2 243% Stiffer than 14mm OEM bar PERRIN 19mm Bar Hole #3 347% Stiffer than 14mm OEM bar PERRIN 22mm Bar Hole #1 400% Stiffer than 14mm OEM bar PERRIN 22mm Bar Hole #2 535% Stiffer than 14mm OEM bar PERRIN 22mm Bar Hole #3 729% Stiffer than 14mm OEM bar |
Swaybars are suspension tuning tools. The reason cars come with body roll and suspension compliance is to avoid what you're experiencing.
Rear bar helps mostly with dialing in oversteer if the car front plows on corner entry. I'd go back to stock bar or induce compliance elsewhere if you can (if you have coilovers, maybe adjusting pre-load or damping to be softer could help) |
"I put the most extreme parts I could find on an otherwise stock car, and am surprised and sad that the car is now worse than before..."
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http://www.ft86club.com/forums/showthread.php?t=67345
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The Perrin 16mm is too much? The TRD bar is 15.8mm I believe. 17+ cars are 15mm? |
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For my taste. I like a little bit of safety understeer since I can always bring the nose in a little bit with left foot braking or trail braking. |
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Gotcha. I like mine a bit looser. At least for now. |
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And I wouldn’t quite call the 16mm too much. I would just like to try a stock one. I bought my car with parts on it already. The rear bar was set at full stiff. |
I'd do the same just to check it out. What front bar does it have and what setting?
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Perrin 22mm in softest setting. On Tein’s with 6kg springs all around. Track tire is a 235 Z3. Street tire a 225 V12 evo which is quite understeery on this setup. Going to T2’s with 400lb main springs. Have a set off 500lb springs too I may try. Track setup has a little bit of understeer on turn in and mid corner which can be neutralized with trail braking. |
Nice, let us know what happens when you switch it out.
(Can't quote you for some reason) |
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https://www.mann-engineering.com/pro...stable-swaybar I believe Cusco has a small hollow bar which should be softer than most aftermarket bars as well. https://www.counterspacegarage.com/c...m-brz-frs-gt86 That is if you're tired of waiting and just want to get one already. Honestly unhooking the rear bar isn't so drastic a change because the stock bar is so flimsy as it stands on top of a 0.59 motion ratio. On track/course based on what you currently have though it might be too far and you'd be fighting a constant push unless you can take some rear toe out which might bring it back to balance... |
I had the same Eibach sway bar set on my car and didn't notice any difference in steering admittedly on 6k/6k springs. Given they are a set I am a little surprised in the difference they produced in your car. I imagine on oem springs the cross-talk would be quite noticeable.
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Make sure the rear bar is moving freely. If you really crank down on the mounts, unmodified bushings won't let the bar move. Dremel out some of inside of the bushings or do whatever it takes to let the bar move freely with the end links disconnected.
Also, make sure the end links aren't bound up. I can't speak for how it is with stock springs, but with the SSC autocross package with those bars, the stock end links are at pretty extreme angles, especially at the soft setting. Stiffening the rear bar actually calmed the oversteer, which goes against conventional wisdom. |
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I'm not really sure how serious it is, but I definitely wouldn't recommend them (at least the rear) for a novice driver. I'm no professional, but I'm at least somewhat experienced, and I was driving rather cautiously on the maiden journey until I had time to assess them properly. Still, the rear swung out on me in a way that could have caused issues if a car happened to be in the next lane. I was on a highway exit that veered to the left, and was downshifting while slowing down for the final semi-sharp left turn onto the local road. Downshifting into 2nd seemed to do the trick. Definitely not even remotely close to what would happen in an auto-x run. I think the most surprising part to me is how delayed the aids were. It seems like this corresponds to the "more traction, but lower breakaway threshold, and less warning approaching the threshold" characterization. I wonder if a car like this has any sort of predictive traction control or if it's 100% reactive. Quote:
I re-used the Eibach bushings that came with the kit. I also followed the instructions and lubed them up with some multi-purpose grease. |
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I am saying I didn't notice a difference in steering. That is, the car was no more under or over steery than with the stock bars. Certainly the car didn't roll as much and I noticed some cross-talk at the front when on a track. |
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What tires are you running? |
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Your setup was well matched. The OP doesn't have tires that match the beefy bars. |
The TRD (Eibach) sway bars are 20.6 front and 15.8mm rear - you've gone way too big for your setup.
I have had TRD sways and the TRD springs, on stock dampers, installed for a couple of weeks and it's a great combo as you'd expect for a kit designed specifically for the car and street use. Sits flat in corners compared to stock, feels planted. I run Bridgestone Potenza RE003 (equivalent to Firehawk Indy 500), stock size on stock rims providing a really good grip upgrade from the stock Michelins. I still have a car that wants to understeer first before the rear end feels loose which I like. It's been a very worthwhile upgrade from the way it was stock - better tyres, and a properly sorted and matched set of springs and bars. |
All-season tires and big bars can do that, especially with an unknown alignment. I would also recommend adjustable endlinks with adjustable swaybars.
Though remember they're hollow bars, so approx 22/16 if solid. Eibach has changed their wall thickness at least once but it's close to that. Either way, get some new tires, adjustable endlinks, and a good performance alignment. - Andrew |
If you are on Firehawk all seasons, a better tire would probably make a big difference. What you described in the main reason why I haven't touched my suspension on this car. First because I don't know what I'm doing much, have no desire to track, and I don't want to upset the balance. Why not just sell them and go back to stock? Stiffer sway bars and less body roll isn't necessarily better...it may make the car feel better around corners, but may also be slower.
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This is a great point. Less body roll does not automatically mean more grip. |
I know a lot of serious auto-xers go to a softer rear bar.
https://www.mann-engineering.com/col...stable-swaybar |
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Yes, the sway bars are equivalent to something like 22/16 solid. Considering tires now and may do an alignment soon. Quote:
I finally decided to commit and learn something rather than asking "what if" The entire purpose of putting on these sway bars in specific, or modifying the car in general, is to learn more about vehicle dynamics. And now I know a lot more than I did before. Even knowing ok, this is gonna be different, I should be careful, I was still caught off guard because I had no firsthand experience. I just knew, factually, it will behave differently. Now I know what it feels like, and the connection between stiffer rear --> more likely to slide out is reinforced mentally. I can also make an informed decision if I want to stay with the Eibach bars, or maybe look for something between these and stock rather than guesstimating. Running back home with my tail between my legs (throwing stock parts back on) for the sake of "not upsetting the balance" probably won't do me any favors. Quote:
It may be more likely to have sharp oversteer, but if you can ride that narrow line where you're drawing the maximum handling benefits but right before the limit of losing traction, then it would be a positive. The issue is if taking the new limit of grip is better or worse than before. Sure, it's possible that even a novice driver on the stock parts, could take a turn better than an experienced driver on these sway bars, but I'm doubtful that's the case here. Think about an F1 car. Assuming I can even get it moving, just because I spin out doesn't mean the car is poorly set up. It's an extremely fine-tuned precision instrument. Suspension designed to perfection. Me spinning it out doesn't give me any right to say "obviously the rear sway bar is too big." Now that I've had a chance to drive the car in a variety of conditions, it's been interesting. I've still been cautious, but it hasn't swung out on me at all. I pushed it through a few highway exit ramps, and it easily stayed tight to the inside even already going faster than I expected. |
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My point was ignoring driver skill... too much roll stiffness for the rest of the setup (tires especially), especially from just sway bars, can end up with less mechanical grip even with the best driver behind the wheel. |
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A good approach is, do not throw on a part unless you know what behaviour or problem you're trying to fix. If you know your issue/problem then work smart to understand what part is best suited to address said problem within the confines of your means (time, budget, etc.) It sounds like you knew a higher roll stiffness in the rear would induce oversteer and you just reinforced it by buying a stiffer bar. That is not something one would say was a good purchase. Also, just because Eibach makes stiffer bars, doesn't mean the car requires it. It's a bread and butter part for them and other aftermarket companies. Their product development usually goes something like this: New platform released>Take stock bar diameter and +1/2mm>Sell product. The simple fact is that you changed suspension parts while running on all season tires, this alone tells us you did not do adequate research prior to purchasing these parts. |
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I am guilty as well of buying parts just to learn. The knowledge can be just as valuable as an increase in performance.
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