Official F-sport Sway Bar Thread!
and ill be good. I've always throught that the front bar didn't help much, but from reading some post on here it does....
04-13-11, 02:30 PM
#574
With all the confusion and questions over how much more stiff the F-Sport is vs. stock, in 39 pages I was quite surprised I've not seen anybody give a closer look at the published stiffness values...
For the solid rear 19mm F-Sport bar, the math shows F-Sport's published data to be very close to what you'd expect from doing the math yourself. That's to say, if you plug the solid bar stiffness ratio equation into Excel, you get a ratio/solution of 2.574, or rather, a solid 19mm bar is 157.4% more torsionally stiff than a solid 15mm bar. The excel equation is simply =(0.19^4)/(0.15^4). And as validated by post-install reviews, this bar really does do some serious stiffening over stock...check!
For the front bar, this analysis gets more complicated. Hollow bars use a more complex equation and require the wall thickness for a meaningful solution. I've not been able to find a published thickness of the stock bar, though the 28.6mm aftermarket F-Sport bar is listed at 4.5mm wall thickness. If someone wants to cut their stock bar in half and measure the metal's thickness for the greater good of CL, this would answer everything!
Assuming for a moment (for simplicity) both stock and aftermarket front bars are solid, the same equation above yields a ratio of 1.223, or rather 22.3% more stiff than stock. The excel equation for this is =(0.286^4)/(0.272^4), not terribly far from what is published at 6.3%...
Until someone publishes some good data on the thickness of the front bar (or if I get bored and happen to stumble upon $300 I can't think of a better use for), I'm going to order and install only the rear bar on my new IS350. Woot!
For the solid rear 19mm F-Sport bar, the math shows F-Sport's published data to be very close to what you'd expect from doing the math yourself. That's to say, if you plug the solid bar stiffness ratio equation into Excel, you get a ratio/solution of 2.574, or rather, a solid 19mm bar is 157.4% more torsionally stiff than a solid 15mm bar. The excel equation is simply =(0.19^4)/(0.15^4). And as validated by post-install reviews, this bar really does do some serious stiffening over stock...check!
For the front bar, this analysis gets more complicated. Hollow bars use a more complex equation and require the wall thickness for a meaningful solution. I've not been able to find a published thickness of the stock bar, though the 28.6mm aftermarket F-Sport bar is listed at 4.5mm wall thickness. If someone wants to cut their stock bar in half and measure the metal's thickness for the greater good of CL, this would answer everything!
Assuming for a moment (for simplicity) both stock and aftermarket front bars are solid, the same equation above yields a ratio of 1.223, or rather 22.3% more stiff than stock. The excel equation for this is =(0.286^4)/(0.272^4), not terribly far from what is published at 6.3%...
Until someone publishes some good data on the thickness of the front bar (or if I get bored and happen to stumble upon $300 I can't think of a better use for), I'm going to order and install only the rear bar on my new IS350. Woot!
04-13-11, 02:43 PM
#575
Edit: There's some other confusion in this thread I didn't notice before had also originated from this same observation of two very similar part listings:
I have an ISF and I have the rear bar PN PTR02-53080, the old IS250 AWD rear bar kit.http://is.sewellparts.com/accessorie...rior/--90.html
and
http://is.sewellparts.com/accessorie...2009/2178.html
I've got an email to Sewell asking if the extra "bracket/bolts" listed is necessary for the IS350 install. Thx!
Last edited by Leander311; 04-13-11 at 03:30 PM.
04-13-11, 03:19 PM
#576
Absolutely. The one that cited .90g's was one of the "follow up" tests by either car and driver or road and track which I'm trying to find right now.
In the meantime, I did find a few other sources that cite a figure that is close (.89g's).
Edmunds Insideline IS250 F-sport "follow up test" -
http://www.insideline.com/lexus/is-2...w-up-test.html
"Handles Like an IS-F
And it turns.
Powerslides are impossible with the big tires and little engine, but this car scorches our track with handling numbers that exceed the performance of the mighty IS-F. No, we're not kidding. This IS runs 71 mph through our slalom, circles our skid pad at 0.89g of lateral grip and stops from 60 mph in just 109 feet."
I will try to look up the source that recorded .90g in the meantime, hang tight.
Edit:
Here is Road and Track's test for a stock IS350 where they measure .84g's -
http://www.roadandtrack.com/tests/co...7-lexus-is-350
Click on the "data panel" under downloads -
http://www.roadandtrack.com/var/ezfl...b477099096.pdf
Edit again:
I Found an edmunds insideline testing the IS350C with F-sport goodies -
http://www.insideline.com/lexus/is-3...and-video.html
Again, they measured .89g's there.
Looks like an improvement from .84g's to .89g's is the best thing to put, since I've readily found two sources that cite .89g's so far. I'll keep looking for the .90 g's though and update this post as needed.
In the meantime, I did find a few other sources that cite a figure that is close (.89g's).
Edmunds Insideline IS250 F-sport "follow up test" -
http://www.insideline.com/lexus/is-2...w-up-test.html
"Handles Like an IS-F
And it turns.
Powerslides are impossible with the big tires and little engine, but this car scorches our track with handling numbers that exceed the performance of the mighty IS-F. No, we're not kidding. This IS runs 71 mph through our slalom, circles our skid pad at 0.89g of lateral grip and stops from 60 mph in just 109 feet."
I will try to look up the source that recorded .90g in the meantime, hang tight.
Edit:
Here is Road and Track's test for a stock IS350 where they measure .84g's -
http://www.roadandtrack.com/tests/co...7-lexus-is-350
Click on the "data panel" under downloads -
http://www.roadandtrack.com/var/ezfl...b477099096.pdf
Edit again:
I Found an edmunds insideline testing the IS350C with F-sport goodies -
http://www.insideline.com/lexus/is-3...and-video.html
Again, they measured .89g's there.
Looks like an improvement from .84g's to .89g's is the best thing to put, since I've readily found two sources that cite .89g's so far. I'll keep looking for the .90 g's though and update this post as needed.
04-13-11, 03:55 PM
#577
So... PS - Those of you who bought the part linked above bought the stock IS-F bar, not the aftermarket F-Sport bar. There's about $20 difference in price, but the description is identical between the two (except for an additional line about some included bracket/bolts). Didn't think you needed any additional hardware except for the bushings?
• Includes additional sway bar brackets and bolts
Lou
04-13-11, 04:24 PM
#578
You are wrong. The ISF bar is a 17mm bar with a different bend. Both of the bars you referenced are identical, except for the added hardware. Some folks need this hardware because their old hardware (bolts) may freeze up and may need to be cut. The specifications and descriptions of both your referenced bars are the same except for the addition of:
• Includes additional sway bar brackets and bolts
Lou
• Includes additional sway bar brackets and bolts
Lou
04-14-11, 04:01 AM
#580
With all the confusion and questions over how much more stiff the F-Sport is vs. stock, in 39 pages I was quite surprised I've not seen anybody give a closer look at the published stiffness values...
For the solid rear 19mm F-Sport bar, the math shows F-Sport's published data to be very close to what you'd expect from doing the math yourself. That's to say, if you plug the solid bar stiffness ratio equation into Excel, you get a ratio/solution of 2.574, or rather, a solid 19mm bar is 157.4% more torsionally stiff than a solid 15mm bar. The excel equation is simply =(0.19^4)/(0.15^4). And as validated by post-install reviews, this bar really does do some serious stiffening over stock...check!
For the front bar, this analysis gets more complicated. Hollow bars use a more complex equation and require the wall thickness for a meaningful solution. I've not been able to find a published thickness of the stock bar, though the 28.6mm aftermarket F-Sport bar is listed at 4.5mm wall thickness. If someone wants to cut their stock bar in half and measure the metal's thickness for the greater good of CL, this would answer everything!
Assuming for a moment (for simplicity) both stock and aftermarket front bars are solid, the same equation above yields a ratio of 1.223, or rather 22.3% more stiff than stock. The excel equation for this is =(0.286^4)/(0.272^4), not terribly far from what is published at 6.3%...
Until someone publishes some good data on the thickness of the front bar (or if I get bored and happen to stumble upon $300 I can't think of a better use for), I'm going to order and install only the rear bar on my new IS350. Woot!
For the solid rear 19mm F-Sport bar, the math shows F-Sport's published data to be very close to what you'd expect from doing the math yourself. That's to say, if you plug the solid bar stiffness ratio equation into Excel, you get a ratio/solution of 2.574, or rather, a solid 19mm bar is 157.4% more torsionally stiff than a solid 15mm bar. The excel equation is simply =(0.19^4)/(0.15^4). And as validated by post-install reviews, this bar really does do some serious stiffening over stock...check!
For the front bar, this analysis gets more complicated. Hollow bars use a more complex equation and require the wall thickness for a meaningful solution. I've not been able to find a published thickness of the stock bar, though the 28.6mm aftermarket F-Sport bar is listed at 4.5mm wall thickness. If someone wants to cut their stock bar in half and measure the metal's thickness for the greater good of CL, this would answer everything!
Assuming for a moment (for simplicity) both stock and aftermarket front bars are solid, the same equation above yields a ratio of 1.223, or rather 22.3% more stiff than stock. The excel equation for this is =(0.286^4)/(0.272^4), not terribly far from what is published at 6.3%...
Until someone publishes some good data on the thickness of the front bar (or if I get bored and happen to stumble upon $300 I can't think of a better use for), I'm going to order and install only the rear bar on my new IS350. Woot!
04-14-11, 11:03 AM
#581
You're quite welcome. Thanks to all the other generous folks here, I've already learned a ton here at CL, so I might as well return the favor and try to contribute, no?
Here's a little more math to get us a step closer on the "unsolved" front bar problem. Please keep in mind I'm recalling roll bar stiffness equations from a college class on formula car engineering I had almost a decade ago, so I may not be 110% accurate here. Also, I don't really enjoy math, but since cars are more fun than work, scratched this out on the back of a meeting agenda this morning while trying to stay awake during said meeting. So I'll try to verify my math this weekend to ensure it's not wasted effort. That said, consider the following scenarios:
1. "Simplified" scenario I describe in previous post where both stock and aftermarket bars are modeled as being solid. This resulted in a 22.3% increase in stiffness, not terribly far from the published data.
2. The stock 27.2mm front bar is the same 4.5mm thickness as the aftermarket FSport bar. In this case, the equation would be:
S = (Db^4 - db^4) / (Da^4 - da^4), where:
S = Stiffness ratio
Da = outside diameter of stock bar
da = inside diameter of stock bar
Db = outside diameter of Fsport bar
db = inside diameter of Fsport bar
Since we are solving for a dimensionless ratio, units are not important, so long as you are consistent with all your numbers. This is important later for scenario 3... So for clarity, I'll give my numbers in meters for scenarios 2 and 3.
Solving for stiffness, and again assuming the Fsport bar wall thickness is 4.5mm, we get S = (.0286^4 - .0241^4) / (.0272^4 - .0227^4) = 1.177, or rather the Fsport bar is 17.7% more stiff than the stock bar... Closer, but still higher than the advertised 6.1% improvement, which begs the question, "How thick must the stock bar be to equate to the advertised 6.1% improvement advertised for the FSport front bar?"
3. We basically use the same equation given in scenario 2, solving for the unknown interior diameter (to determine wall thickness). Filling in for the known variables, our equation becomes 1.061 = (.0286^4 - .0241^4) / (.0272^4 - da^4)
Solving for "da", we get .0220. The difference Da - da is our wall thickness, thus .0272 - .0220 = .0052, or 5.2mm.
As I said before, if someone dissects their stock front bar and can measure the wall thickness at 5.2mm, we'll know Lexus has their calcs very close at least for the IS350 advertised numbers.
Thanks,
Nick
Here's a little more math to get us a step closer on the "unsolved" front bar problem. Please keep in mind I'm recalling roll bar stiffness equations from a college class on formula car engineering I had almost a decade ago, so I may not be 110% accurate here. Also, I don't really enjoy math, but since cars are more fun than work, scratched this out on the back of a meeting agenda this morning while trying to stay awake during said meeting. So I'll try to verify my math this weekend to ensure it's not wasted effort. That said, consider the following scenarios:
1. "Simplified" scenario I describe in previous post where both stock and aftermarket bars are modeled as being solid. This resulted in a 22.3% increase in stiffness, not terribly far from the published data.
2. The stock 27.2mm front bar is the same 4.5mm thickness as the aftermarket FSport bar. In this case, the equation would be:
S = (Db^4 - db^4) / (Da^4 - da^4), where:
S = Stiffness ratio
Da = outside diameter of stock bar
da = inside diameter of stock bar
Db = outside diameter of Fsport bar
db = inside diameter of Fsport bar
Since we are solving for a dimensionless ratio, units are not important, so long as you are consistent with all your numbers. This is important later for scenario 3... So for clarity, I'll give my numbers in meters for scenarios 2 and 3.
Solving for stiffness, and again assuming the Fsport bar wall thickness is 4.5mm, we get S = (.0286^4 - .0241^4) / (.0272^4 - .0227^4) = 1.177, or rather the Fsport bar is 17.7% more stiff than the stock bar... Closer, but still higher than the advertised 6.1% improvement, which begs the question, "How thick must the stock bar be to equate to the advertised 6.1% improvement advertised for the FSport front bar?"
3. We basically use the same equation given in scenario 2, solving for the unknown interior diameter (to determine wall thickness). Filling in for the known variables, our equation becomes 1.061 = (.0286^4 - .0241^4) / (.0272^4 - da^4)
Solving for "da", we get .0220. The difference Da - da is our wall thickness, thus .0272 - .0220 = .0052, or 5.2mm.
As I said before, if someone dissects their stock front bar and can measure the wall thickness at 5.2mm, we'll know Lexus has their calcs very close at least for the IS350 advertised numbers.
Thanks,
Nick
04-14-11, 06:22 PM
#582
^^
Thanks for continuing your analysis. Hopefully the mystery will soon be solved regarding the change of stiffness % for the F-Sport front sway bar (Old=6%, New=42%).
I'm also curious to know if a verdict has been reached regarding the part numbers for the IS250 and IS350 front and rear OEM sway bars (are they different P/Ns or the same?). If the OEM sway bars for the 250 & 350 are the same, why is the stiffness % different between the two?
Thanks for continuing your analysis. Hopefully the mystery will soon be solved regarding the change of stiffness % for the F-Sport front sway bar (Old=6%, New=42%).
I'm also curious to know if a verdict has been reached regarding the part numbers for the IS250 and IS350 front and rear OEM sway bars (are they different P/Ns or the same?). If the OEM sway bars for the 250 & 350 are the same, why is the stiffness % different between the two?
04-14-11, 06:30 PM
#583
I'm also curious to know if a verdict has been reached regarding the part numbers for the IS250 and IS350 front and rear OEM sway bars (are they different P/Ns or the same?). If the OEM sway bars for the 250 & 350 are the same, why is the stiffness % different between the two?
In either case, we'll know if someone measures wall thickness for us. If I grow too impatient (and can cough up another $300 before my girlfriend kills me for not proposing), I may have to do it myself. Hopefully not!
04-14-11, 08:07 PM
#584
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You're quite welcome. Thanks to all the other generous folks here, I've already learned a ton here at CL, so I might as well return the favor and try to contribute, no?
Here's a little more math to get us a step closer on the "unsolved" front bar problem. Please keep in mind I'm recalling roll bar stiffness equations from a college class on formula car engineering I had almost a decade ago, so I may not be 110% accurate here. Also, I don't really enjoy math, but since cars are more fun than work, scratched this out on the back of a meeting agenda this morning while trying to stay awake during said meeting. So I'll try to verify my math this weekend to ensure it's not wasted effort. That said, consider the following scenarios:
1. "Simplified" scenario I describe in previous post where both stock and aftermarket bars are modeled as being solid. This resulted in a 22.3% increase in stiffness, not terribly far from the published data.
2. The stock 27.2mm front bar is the same 4.5mm thickness as the aftermarket FSport bar. In this case, the equation would be:
S = (Db^4 - db^4) / (Da^4 - da^4), where:
S = Stiffness ratio
Da = outside diameter of stock bar
da = inside diameter of stock bar
Db = outside diameter of Fsport bar
db = inside diameter of Fsport bar
Since we are solving for a dimensionless ratio, units are not important, so long as you are consistent with all your numbers. This is important later for scenario 3... So for clarity, I'll give my numbers in meters for scenarios 2 and 3.
Solving for stiffness, and again assuming the Fsport bar wall thickness is 4.5mm, we get S = (.0286^4 - .0241^4) / (.0272^4 - .0227^4) = 1.177, or rather the Fsport bar is 17.7% more stiff than the stock bar... Closer, but still higher than the advertised 6.1% improvement, which begs the question, "How thick must the stock bar be to equate to the advertised 6.1% improvement advertised for the FSport front bar?"
3. We basically use the same equation given in scenario 2, solving for the unknown interior diameter (to determine wall thickness). Filling in for the known variables, our equation becomes 1.061 = (.0286^4 - .0241^4) / (.0272^4 - da^4)
Solving for "da", we get .0220. The difference Da - da is our wall thickness, thus .0272 - .0220 = .0052, or 5.2mm.
As I said before, if someone dissects their stock front bar and can measure the wall thickness at 5.2mm, we'll know Lexus has their calcs very close at least for the IS350 advertised numbers.
Thanks,
Nick
Here's a little more math to get us a step closer on the "unsolved" front bar problem. Please keep in mind I'm recalling roll bar stiffness equations from a college class on formula car engineering I had almost a decade ago, so I may not be 110% accurate here. Also, I don't really enjoy math, but since cars are more fun than work, scratched this out on the back of a meeting agenda this morning while trying to stay awake during said meeting. So I'll try to verify my math this weekend to ensure it's not wasted effort. That said, consider the following scenarios:
1. "Simplified" scenario I describe in previous post where both stock and aftermarket bars are modeled as being solid. This resulted in a 22.3% increase in stiffness, not terribly far from the published data.
2. The stock 27.2mm front bar is the same 4.5mm thickness as the aftermarket FSport bar. In this case, the equation would be:
S = (Db^4 - db^4) / (Da^4 - da^4), where:
S = Stiffness ratio
Da = outside diameter of stock bar
da = inside diameter of stock bar
Db = outside diameter of Fsport bar
db = inside diameter of Fsport bar
Since we are solving for a dimensionless ratio, units are not important, so long as you are consistent with all your numbers. This is important later for scenario 3... So for clarity, I'll give my numbers in meters for scenarios 2 and 3.
Solving for stiffness, and again assuming the Fsport bar wall thickness is 4.5mm, we get S = (.0286^4 - .0241^4) / (.0272^4 - .0227^4) = 1.177, or rather the Fsport bar is 17.7% more stiff than the stock bar... Closer, but still higher than the advertised 6.1% improvement, which begs the question, "How thick must the stock bar be to equate to the advertised 6.1% improvement advertised for the FSport front bar?"
3. We basically use the same equation given in scenario 2, solving for the unknown interior diameter (to determine wall thickness). Filling in for the known variables, our equation becomes 1.061 = (.0286^4 - .0241^4) / (.0272^4 - da^4)
Solving for "da", we get .0220. The difference Da - da is our wall thickness, thus .0272 - .0220 = .0052, or 5.2mm.
As I said before, if someone dissects their stock front bar and can measure the wall thickness at 5.2mm, we'll know Lexus has their calcs very close at least for the IS350 advertised numbers.
Thanks,
Nick
Taking a difference in outer diameter and inner diameter does not give you wall thickness, it gives you twice the wall thickness. Taking a difference in outer radius and inner radius gives you a wall thickness. Let's assume the the wall thickness of the F-sport sway bar is 4.5mm (even tho Sewell and Toyota claim it's 4.8mm) that would mean that the inner diameter of the F sport sway bar is 19.6mm. If let's say a stock IS350 bar has an outer diameter of 27.2mm and you don't know the inner diameter, you could assume the advertised rating of 6.1% (1.061) and solve for the unknown... doing this would yield an inner diameter of 15.37mm, which corresponds to a wall thickness of 5.9mm. The wall thickness of the F-sport from above is 4.5mm... hmm, reason this works out is because a larger diameter pipe doesn't need as thick of a wall relative to a smaller pipe to achieve a greater polar moment of inertia, or an moment of inertia for that matter. If you goto post #301 in this thread and download the PDF, you'll see that the stock bar for a 350 has a wall thickness of 5mm. Now whether or not this is true, I have no idea but let's assume its true. Just by visual inspection of the two wall thicknesses (5.9mm vs 5.0mm) you can see that a 5mm wall thickness for a stock outter diameter of 27.2mm bar will result in a stiffness increase (for the F sport) over 6%....to be exact it's 13.4%. Once again, I have no idea whether or not the wall thickness of the stock sway bar actually is 5mm...to me it sounds like a reasonable value but until someone measures you won't know. The best bet? assume its anywhere in between 6% and 13.4%. Either way.... a pipe will always have a lower moment of inertia than its solid rod equivalent and so, it ain't got **** on the rear sway bar.
Last edited by huch; 04-14-11 at 08:13 PM.
04-14-11, 08:35 PM
#585
Thanks for the clarification, Huch.
Like I said, I'm not a huge fan of math and realized this was not 110% checked before I had posted. Not even sure if my equations are right, just pulling them from some grey matter that hasn't been accessed for a decade plus or minus.
I'll give it a further look this weekend. The posts still served their purpose...glad to finally get some folks actually thinking about this rather than the majority of the 39 pages of "so...um...did we decide which one is better or if we need one or both or which is the right one or the wrong one" type stuff we've had to sort thru.
Like I said, I'm not a huge fan of math and realized this was not 110% checked before I had posted. Not even sure if my equations are right, just pulling them from some grey matter that hasn't been accessed for a decade plus or minus.
I'll give it a further look this weekend. The posts still served their purpose...glad to finally get some folks actually thinking about this rather than the majority of the 39 pages of "so...um...did we decide which one is better or if we need one or both or which is the right one or the wrong one" type stuff we've had to sort thru.