Front suspension problem solution

Discussion in 'Prius c Accessories and Modifications' started by mahout, Apr 23, 2013.

  1. mahout

    mahout Active Member

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    Having been hounded to solve the front suspension solutuioin to dropping 1 inch and extending front axles by 1/4" via reduced wheel offset here's the suspension changes
    .
    Fitst, a McPherson strut is a rigid attachment to the wheel hub and thus any change in angle of the axle is the same as change in camber. If the end of the axle is for all practical measurement (thanks to wheeel offset); if 600 pounds is applied to the end of the McPherson strut and the spring height is changed by one inch the angle of the wheel, or camber, changes by 1/17", 0,0588 inches; sin of .0588 is 3 degrees 23 minutes. The camber doesn't really change that much because the change in angle is countered by the change in the body roll equvilent to the change in the axle position. In this case, if the McPherson strut spring is 250 pounds per inch spring rate, when the 600 pound force (actually the force holding up the suspension and vehicle weight), is moved outward by a quarter-inch, 6mm, the force required for the
    mcPherson strut spring still at 17" to provide is 17.25x600 +17, or 609 pounds. Thats 9 additional pounds for the 250 pound spring to handle, or .036 inches in 17", which is about 20 minutes, or 1/3 degree.. To find the realistivc change is the camber subtract the 1/3 minute from the 3 and 1/3 degerees and you get 3 degrees. An actual measured 2.8 degrees more negative camber is good verification of a calculated change. Especially having to estimate the strut spring rate.and yes I did make calculations a bit easier by moving the strut support in to 8 inches but for this one I thought I'd be as accurate as I could. Believe it or not there are computer programs to do all these calculations in movement and they are really eye-opening to waching suspemnsions at work in both straight ahead and turning conditions and with varying weight transfer heights (body lean).
    cheers.
     
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  2. toyotechwv

    toyotechwv Toyota Technician

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    And the problem was........

    SPH-D710 ? 2
     
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  3. B2FiNiTY

    B2FiNiTY Active Member

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    :cautious:err what?
     
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  4. Sfcyclist

    Sfcyclist Senior Member

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    hounded.. right.. lower 1" car, what is the change in toe and camber?
     
  5. ztanos

    ztanos All-around Geek!

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    I can honestly say that I didn't read this... the bold font makes me struggle to read and the fact that this is so long doesn't help. Your horrid grammar just makes my brain hurt even further...
     
  6. mahout

    mahout Active Member

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    There were posters who thought the camber didn't change when the McPherson strut spring was shortened or the axle extended without changing the location of the strut on the axle. I changed the location of the strut to make the math more pronounced but otherwise same as taught by suspension tech service.
    A/Xers generally change wheel offset within the typical 1" track tolerance get more negative camber; racers do both that and drop the strut spring height to lower CG and camber. One of the fiurst thging competitors learn.

    Sorry about the bold; at my age (76) its a lot easier to read since I can't change font size. And my grammar, or spelling likely, is the result of aged typing; correction is hard on this site. So my apologies, don't mean to holler. Well, ok, sometimes. I'll try to italicize. That help?
     
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  7. ztanos

    ztanos All-around Geek!

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    :D
     
  8. minkus

    minkus Active Member

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    Crtl + or ctrl + mouse wheel to zoom in with your browser, assuming you're not on a phone.
     
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  9. Sfcyclist

    Sfcyclist Senior Member

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    If I am re-reading it right, is the question, what is the change in camber with 1" drop on a Prius G3 HB?

    if that is the question what's the answer? 1/3 degree?
     
  10. Conor

    Conor Junior Member

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    What on earth is going on here? The car gets a bazillion MPG. If you're buying a brand new car and about with factory suspension to gain immeasurable tenths of a MPG, you're still in the hole tens of thousands of dollars over where you would have been if you had purchased a 1989 Honda CRX HF. *shrug*
     
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  11. mahout

    mahout Active Member

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    We didn't see a change in toe but did measure 2.8 degree change to validate the change overall. Yes, increasing axle length contributed a small change but did change cornering ability considerably, helped by de-pactivating the front antisway bar that substantially reduced the massive OEM undesteer. On our test track, VIR, those simple chanfges knocxked 11 seconds from the lap times and increasing the fun factor by 200%.

    I owned two HF's, one Civic coupe and one CRX. Great mistake selling either. And yes both sported changed antisway bars, shocks, wheels, and tires to decrease lap times at Savannah and Rockingham. Some of us like to maintain speeds instead of slowing down, and believe it or not, that does result in higher mpg. We also proved with my Insight (whew!) and a couple of Honda Civic hybrids, one of which has videoed laps at VIR. (Honda Hybrid sets 1500 cc record at VIR on utube) in jest getting below 3 min. That record will fall to the Prius C soon.
    While the improved suspension and wheels do improve handling, our true purpose, we have measured 1 to 2 mpg better on trips of a hundred miles or more where steady speeds weren't involved. We did do one before changing the suspension so we did have a comparison for the second.
    Next week I have to drive across WV on secondary roads where handling is a premium and then we can comparempg and time with the Civic hybrid on the same route. Because of the enormous aftermarket for Civics we not all sure the Prius will be better. The Civic had springs, shocks,wheels and better tires (Direzzas) plus better suspension geometry.
    The bottom line is driving enjoyment, not just mpg, that we want. Our cars are not washing machines.
    The future will require high mpg and for those who want sports car like handling this the route.
    BTW 6x15/39 wheels cost $180 for the Prius, springs a$100, tires we already had, and labor was ours; thats a long way from thousands. Lawyers decide the suspensions of all cars save Vettes and Miatas shall understeer mightily so if you reach cornering limits thou shalt skid off couse nose first at as low a speed as feasible. More than a few of us prefer going sideways if necessary to make it instead of sliding off. And if push comes to shove I prefer going off backwards. And tugging at that steering wheel's no fun either. You may ask why we didn't get a CRZ; simply it was a Fit in different body,. If Honda hadn't lost their mojo, it would have had 200 hp and hybrid, a jumior Porshe 918, which is Hondas mojo. Its why CRZ';s had a 150 day supply, rivalling the Fiat 500. And you note the 500 Abarth is selling well in spite of Fiat's rep here. (I had 2, let me tell you about them if you have an afternoon)
    If driving is not your idea of enjoyment stick with the OEM.
     
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  12. toyotechwv

    toyotechwv Toyota Technician

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    Just fyi, I'm in WV and I autocross with the Blue Ridge Region SCCA. Would like to see you at an event some time.

    SPH-D710 ? 2
     
  13. gbouten

    gbouten Junior Member

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    All I can say is Wth?
     
  14. mahout

    mahout Active Member

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    I presume you're in in Charleston. Too far from me but I will check one in NC just for fun. Since you a/x the prius in your photo how're you doing? whats in your class? And I like your mods but I would have thought you needed a stiffer rear bar as it looks like your understeer is still too much for a/x. Looks like rotation isn't very easy.
    Perhaps testing with disconnected front bar might be usedful. Anyway, have at it.

    We'll let VIR be the judge if the Prius C is faster and gets better mpg on track. The Honda Hybrid got 21 mpg with 2:56 kaps. We target the Prius c at 2;50 and 22 mpg. June.

    PS we carved up the WVT at 70 mph and 48 mpg. Drove 445 miles in 7 hours to boot, laughing all the way.

    How about WTFF? Overtaking Camaros, Mustangs, and all manner of sedans on the WVT is WTFF. Maybe they were 4's.
     
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  15. toyotechwv

    toyotechwv Toyota Technician

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    I'm in Princeton, mainly autocross in Va though in Christiansburg and maybe Roanoke this year. I've been driving with one endlink off the front bar for about a week now. Very impressed with the difference. Definitely much less understeer. May add a rear bar before my first event in June.

    I'm currently running in H-stock, typically a Corolla is all that is in my class. A CRZ has been running that class locally this year, hoping he shows up for my first event this year. Thanks for the advice on the front bar. I really think with the r-comp tires last season, had I disconnected the front bar, I believe I could have dropped 2 or more seconds on my fastest run.

    SPH-D710 ? 2
     
  16. mahout

    mahout Active Member

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    Great. Go get 'em !

    The change is about 2.5 degrees total. Extending the axle adds one third degree.


    Last weekend I had the 'opportunity' to drive my Prius C2 in driving rains with and without disaconnected front antisway bar. I cannot imagine driving a stock Prius at anywhere near the limts under such conditions. The front plowed drastically while the disconnected bar made every turn easily and in fact once a couple of stragglers were passed we led every lap and until I shutdown near the end of the seesion no one caught us. PS we got 31 mpg with ECO and stability control off and a best lap of 3:05 on the full course of 3.27 miles. Damn good in rain that hard. I have video but its halting so telling much is hard. Next days in the dry is good but hemmed by all those fast Corvettes, Mustangs,BMW's, etc so didn't really get good lap time but the car is really great to drive even if the speed doesn't exceed 98 mph. got about 30 mpg both days. on track. overall tank 42 mpg. can't wait to see a Mazda2 chassis Prius C2. That should be amazing.
    PS I had a 1989 CRX HF and even tracked it. Darned good car , the best mpg next to my Geo Metro XFi that served our shop for 10 yeares totalling 200k miles at 49.6 mpg, (50+ until 180k) at a total cost of 9 cents a mile !. There'll not likely be another.

    The rest is from lowering 1 inch.

    PS the toe is adjustable so no change would be expected.
     
  17. BigWIll

    BigWIll Junior Member

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    Maybe I missed it, but do you have a rear anti-sway bar installed as well? IIRC from another discussion, installing the rear bar on a c does a significant job of neutralizing the understeer caused by the front-only bar.
     
  18. mahout

    mahout Active Member

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    I do not have a rear bar - yet. Still tracking to get good handle on just how good the OEM suspension can be with only disconnecting the front bar which is preferrable to keep the tires in better contsct with road surfaces. Unfortunately, it'll be end of July thanks to limited access at the track. Then we'll reconnect the front and add rear bar, possibilty with lowered springs, but my regular passenger masy not approve. We'll see. For now our stock recommendation is lowering by an inch or so and disconnect the front bar. Keeping the front bar and asddig a rear is certainly good route, too.
     
  19. cyclopathic

    cyclopathic Senior Member

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    Which springs? rear sway-bar or without? how much lowering, if any?
    Any changes to camber/toe in front? Is car gutted?
     
  20. kingnba6

    kingnba6 Active Member

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    some good information here. ill have to remember and add on to this
     
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