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 Post subject: C5 Suspension
PostPosted: December 6, 2016, 1:06 pm 
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I was looking at the C5 suspension (i also put into wishbone) and noticed a few things

1) their roll center doesn't move very much at all.
2) they have little to no toe change though out their suspension travel
3) at 3° of roll, they have a 3°/-3° of camber change. Its this one that seems odd to me.

any one else have comments on the camber change? I have attached the files for reference.


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corvette c5.zip [290.17 KiB]
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 Post subject: Re: C5 Suspension
PostPosted: December 6, 2016, 2:16 pm 
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How about a Vsusp file? Is this the rear suspension?

Quote:
3) at 3° of roll, they have a 3°/-3° of camber change. Its this one that seems odd to me.


No camber change in squat, for acceleration?

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 Post subject: Re: C5 Suspension
PostPosted: December 6, 2016, 2:21 pm 
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are you asking me? Or asking in general?

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 Post subject: Re: C5 Suspension
PostPosted: December 6, 2016, 6:47 pm 
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DIdn't they have leaf spring suspension too. Like the horse and carts had in the 1800s?

Something like this?
Attachment:
springs.jpg
springs.jpg [ 130.92 KiB | Viewed 3254 times ]

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 Post subject: Re: C5 Suspension
PostPosted: December 6, 2016, 7:28 pm 
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The new ones do too and they are carbon fiber

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 Post subject: Re: C5 Suspension
PostPosted: December 6, 2016, 9:48 pm 
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So what I was looking at is that it looks like they didn't put much effort into trying to keep the wheel upright under roll (yes I know we aren't seeing tire loading etc). Thoughts?

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 Post subject: Re: C5 Suspension
PostPosted: December 7, 2016, 12:33 pm 
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So it seems I'm able to download wishbone files from the site again, which means I'll be try getting to yours soon too mjalaly.

I'm curious where you got these C5 numbers, and whether that's front or rear? The only place I've seen it is in the Performance Trends Suspension Analyzer demo. I took a quick glance at this just before bed last night, and while it doesn't line up exactly with what I had previously seen for C5 geometry, it doesn't seem too terribly far off either. Either way it is certainly a somewhat unexpected looking geometry if you ask me. I do recall that C5 Corvettes are known for having very mild camber gain, even if I think it's at least a little more than I saw from your numbers. Of course, Porsche's and BMW's, with their MacPherson strut front suspensions, also have minimal camber gain.

Remember that you've got competing requirements between straight line bump and cornering. Under acceleration and braking, you want no camber gain. In cornering you want as much camber gain as puts the tire at the optimum lateral grip camber angle, which is non-zero in roll, and far from zero if translated back to straight line bump.

On a race car, you can largely get away with solving this by not allowing the suspension to move. On a street car you don't have that luxury to the same degree. So you must compromise.

In the front you can somewhat maximize both straight line and cornering by running lower bump camber gain, but a higher caster angle to cause the necessary camber gain when the wheels are turned. This is how Porsche and BMW get away with the MacPherson strut front suspensions in performance applications.

On the rear, it really comes down to maximizing straight line performance vs maximizing cornering performance. A problem exacerbated by the fact that the wider and lower profile a tire gets, the more sensitive it is to small changes in camber. On a street car, even one designed for cornering, they'll typically err on the side of straight line performance and even tire wear. Lowering the car some might get it to an area of the travel that has more camber gain, but beyond that you're stuck running extra static camber if you want to maximize lateral grip at the track.

If I stick with a conventional rear suspension on my car, I'll probably put 2 holes in each rear UCA bracket. One positioned more for cornering performance, and the other more for straight line performance.

And yes, implemented correctly, composite leaf springs are kind of awesome. I would love to use some, if only they were anywhere near as readily and affordably available in a wide variety of rates, as coil springs are.

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 Post subject: Re: C5 Suspension
PostPosted: December 7, 2016, 1:52 pm 
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Well I have something different for you too look at that i have spent hours trying to get "right" ; )
I will shoot you a PM.

Also I got the C5 points from a memember on our site. Do you have wishbone file for the C5 that matches the performance trees file?

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 Post subject: Re: C5 Suspension
PostPosted: December 7, 2016, 4:08 pm 
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mjalaly wrote:
Do you have wishbone file for the C5 that matches the performance trees file?
No, but the demo is free to download.

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 Post subject: Re: C5 Suspension
PostPosted: December 7, 2016, 9:13 pm 
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The demo no longer has the C5 chassis in it

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 Post subject: Re: C5 Suspension
PostPosted: December 8, 2016, 2:30 am 
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I just downloaded v2.4 to my other computer last night as well, and the "2001 Corvette" showed up as an option to open in the included vehicle library for me.

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 Post subject: Re: C5 Suspension
PostPosted: December 8, 2016, 10:22 am 
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Some thoughts specifically talking about a high torque mid-engine 80% road and 20% track. 35/65 weight distribution. (more specifically 110 wheelbase 65" Front / 64" rear Track width measuring from tire centers, relative low cg, no ARB)

Do the following statements hold up in your opinion?

In the front: You would want very little camber gain (maybe .5° per bump) as it is primarily a road car, braking not as important because of the weight distribution and camber change due to caster

In the rear: You would want very little camber change during squat due to the high torque output and weigh distribution

but if that is correct how would you keep the rear loaded tire from going very positive during hard turning since this would allow the ass end to kick out? just loads of anti-dive and more rear camber gain since the rear isn't affect by caster? I thought I read that the miata and elise had very low camber change in the front as well.

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 Post subject: Re: C5 Suspension
PostPosted: December 8, 2016, 12:05 pm 
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Quote:
In the front: You would want very little camber gain (maybe .5° per bump)


The maximum camber correction recommended in a road racing car is about %50. Which is roughly the number you are giving above. It's a compromise.

Quote:
You would want very little camber change during squat due to the high torque output and weigh distribution


Rear weight bias would reduce the need to minimize camber during squat, because it's easier to maintain forward traction with more weight on the wheels.

Quote:
very positive during hard turning since this would allow the ass end to kick out? just loads of anti-dive and more rear camber gain since the rear isn't affect by caster?


Caster in the rear will often affect toe, so you can get bump steer and roll steer. This can be intentional or not.

DId you mean anti squat in that last sentence? In the rear the terms are anti lift and anti squat.

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 Post subject: Re: C5 Suspension
PostPosted: December 8, 2016, 12:52 pm 
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A road race car? Deffinition?

I ask because comparing the camber cure to a Miata, they have .8° per 1" bump. (obviously their car is different than what i specified). The rear is .6 per 1" bump
http://www.virkki.com/jyri/miata/camber/camber_NA_F.png

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 Post subject: Re: C5 Suspension
PostPosted: December 8, 2016, 2:20 pm 
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Quote:
A road race car? Deffinition?


Guidelines for cars used in competition. I think it's from the Mark Ortiz Chassis Newsletters, recommending between %25 to %50 camber recovery in roll.

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