I currently have the SPL front upper control arms. With the way they are designed, they change the SAI angle and hence the scrub radius as you adjust the camber.
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11-04-2017, 12:33 AM | #1 (permalink) |
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Front Upper Control Arms...
I currently have the SPL front upper control arms.
With the way they are designed, they change the SAI angle and hence the scrub radius as you adjust the camber. As the SAI increases with the camber increase, and working with the caster, it creates more jacking of the car on the inside tire when the wheel is turned, effectively leaning the car away from corners. I tend to view this negatively. (although I do like the increased steering effort and feedback) Does anyone have any thoughts on this or comparisons to other FUCA designs for the 370 in regards to this line of thought? Last edited by ValidusVentus; 11-04-2017 at 05:55 PM. |
11-04-2017, 04:10 AM | #2 (permalink) |
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I can't personally answer these question's, but from everything i've heard about the SPL brand parts-is nothing but exceptional.
You currently have the best product on your Z...People whom track their car will chime in & give details about the (Steering Axis Inclination) & any other concern's. You may need some additional part's to achieve best result's.
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11-04-2017, 04:37 AM | #3 (permalink) |
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The situation you describe puts more weight on the inside tyre which means it contributes more grip towards turning the car rather than the alternative which places more load on the outside tyre.
remember you get lateral weight transfer when rotating the car and the problem is how to "share" the effort across both front tyres. I actually think that SPL have it "right" ....... As the car rolls onto the outside front tyre with weight transfer, the effect of the FUCA with increased lock puts more weight onto the inside tyre and so it is able to share more of the available grip rather than letting the outside tyre do "all the work". |
11-04-2017, 05:46 PM | #4 (permalink) | |
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Quote:
Admittedly though, only in the very tightest of on track corners would this effect possibly be significant I suppose. With its noticeable effect on the steering weight and self centering I was also considering if it would contribute to almost a pendulum like effect with larger quick corrections; which seems to be something I do feel a bit of. Tough to say. jchammond I would say I've tracked the car quite a bit but I still like to ponder some of these more difficult to measure things (especially while I don't have access to my car or track time) and was just looking for other's thoughts about it. I agree about SPL, have several of their products on my Z Last edited by ValidusVentus; 11-04-2017 at 05:51 PM. |
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11-05-2017, 01:08 AM | #5 (permalink) |
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What are your alignment specs?
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11-05-2017, 02:30 PM | #6 (permalink) | |
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Take a peek at the smithees website (URL) below where he goes into it in some depth. Race Car Suspension Set-Up |
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11-05-2017, 09:43 PM | #7 (permalink) |
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The SR does not change in this situation. Only the SAI. The SR would only change if you changed the angle of the upright and not the camber and caster.
The only way you'd change the SR is if you change the wheel offset, or somehow modify the upright to change inclination. Jacking would be increased during turning if you increased caster angle. In this case, don't increase caster. |
11-06-2017, 03:35 PM | #8 (permalink) | |
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And I tried to go to the link above but it doesn't seem to work on the gov computers unfortunately, they never seem to like links that end in a foreign abbreviation. |
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11-06-2017, 05:04 PM | #9 (permalink) | |
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If you increase caster along with camber you will have increased rise and fall. Adding stiffer components won't help much here. It would mostly just make steering more sensitive. |
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11-06-2017, 06:56 PM | #10 (permalink) | |
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11-06-2017, 08:47 PM | #11 (permalink) | |
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Racing tires needed additional camber, adding positive caster is another way of getting more camber with additional steering lock. The tires dont need caster, in most cases its worse for the tires as it pulls the tire away from the road. Increased negative scrub and wider tires is necessary if you increase camber and caster. |
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11-06-2017, 09:02 PM | #12 (permalink) | |
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Toyo Tires recommends the following general set-up guidelines for the Proxes R888: Operating Temperature: 160°F to 220°F Hot Inflation Pressures: 32 to 38 (psi) Camber: -1° to -3° Caster: As much positive as possible
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11-06-2017, 09:54 PM | #13 (permalink) | |
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Quote:
Hot Inflation Pressure: less than 36 psi tire will get squirrelly 36 psi or better. Camber: -2.26 front -2.00 rear Caster: 6.5 and I think 7 to 8 would be better There was another member here running -3.3 front and -1.8 rear with caster at 8 for the same tire. He was running 18x315 and I am running 18x295.
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11-06-2017, 11:59 PM | #14 (permalink) | |
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11-07-2017, 01:27 AM | #15 (permalink) | |
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This also doesn't take into account the wide variety of suspension setups these tire companies are advertising to. Cars without sway bars, cars with solid rear axles, cars with McPherson struts. None of this is a problem for the Z. So additional caster AND camber is not a necessary change, its the reason nissan knocked the Z34 down to -+5 degrees of caster. If you want more response out of the tires, properly match the SR for the given wheel/tire you are trying to use. Not an easy thing to do when dealing with clearance and fitment issues (brakes or fenders). So yes, this is the ultimate compromise. Adding caster and camber ruins your instantaneous roll center. Something that will severely compromise how the suspension balance SHOULD be setup. |
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