Torsion bar delete: rear too low
08-25-2012, 12:14 AM
#16
Drifting
Thread Starter
Charlie, I am running the same spring rate and setup (500lb rear; 400lb front, Bilstein Escort Cup shocks 380/150frt, 565/218 rear dampening, torsion bars deleted) and the ride is firmer than stock but not overly harsh and find it is a good compromise if you plan to use it for street and occasional track day (have not experienced wheel hop). I did find when I first was assembling the spring on the shock that the collar would not compress the spring enough to preload it. I had to order the helper springs and spacers from Lindsey; you may have to call Dave to see if they still stock them, as they are not listed on their website anymore. If you plan on running stiffer springs or full track car setup, you might want to look at getting the shocks dampening changed, as incorrect dampening will cause the wheel to hop with too much spring rate or you can increase the spring rate till the shocks are no longer effective and you have a rock solid ride with little suspension movement.
Stacy
Stacy
08-25-2012, 12:16 AM
#17
Three Wheelin'
Mike, 850 is too much spring for the weight of the car unless you have them set-up like the H&R coilovers with a softer tender spring in tandem. Think about it, your corner weight is lower than your spring rate, body will bounce before your damper can react. Post more about your set-up to clarify pls.
They ARE the H&R coilovers. I've posted plenty of info on these already.
Motion ratio at the rear is 0.65, so *wheel* rate is 0.4225 x 850 = 359lb/in. Rear wheel sprung weight is about 650lb so static deflection = 1.8" and suspension frequency is about 2.33Hz.
The H&R front springs are 400lb/in and the front motion ratio is about 0.94 so the wheel rate is 0.8836x400 = 353lb/in. Front wheel sprung weight is about 660lb so static deflection = 1.87" and suspension frequency is about 2.29Hz.
Front/rear suspension frequency ratio is 1.02.
Read this article and compare: http://www.rqriley.com/suspensn.htm
Cheers,
Mike
08-25-2012, 12:21 AM
#18
Three Wheelin'
Originally Posted by Karl / RacersEdge
I have not spoken with 'x', and actually don't know who he is. But believe me, my numbers correct (or close to it - see the following explanation). The info on Paragons site is stuff they got from me a few years ago. In any case, the 47% is a number that I have calculated By taking measurements. I am now pulling out one of Porsche's own Motorsport sheets that shows all the rates of their Turbo and "Cup" cars back when they ran competitively. Porsche lists the 25.5 mm bar as 31 N/mm which is 177 lbs/in. They also then give the variable rate coilover helper spring rates at 34-65 N/mm which is 194 lb/in - 371 lb/in. They then give the total Rate at the wheel(T-bar plus coilover) as 45.4 - 58.5. Back out the rate at the wheel due to torsion bar which they list as 31 and you have 14.4 - 27.5 at the wheel due to the coil over. So take your pick, 14.4 / 34 is approx 42% or 27.5/65 is 42%.
'x' is right about them being inboard but his numbers are off. Actually they are correct I think in that the motion ratio is about 65%. But when calculating wheel rates from spring rates it is the motion ratio squared that is uses. So 0.65 ^2 is , guess what,... 42.25% which is the number that Porsche's own sheet claims as I outlined above. So your torsion bar is 177 at the wheel, and your helper spring rate is a 285 which is 119.7 lb/in at the wheel. So working backwards 177 plus 119.7 is 296.7 pounds per inch at the wheel. Divide this by .42 and that is you equivalent coilover, or 706 lb/in coilover (initially I had 661 lb/in which is attributable to my measurement error - I had 47% and Porsche lists it at 42%).
So it may be a bit stiffer in the rear than I might run but with the ability to tune sway bars etc... you should be Fine. Your setup is actually much stiffer in the front than the Porsche cup setup which ran progressive front springs (200 - 371 lb/in) with the rear setup I described above which is not that far from what you have( yours is 296 at the wheel and theirs was 259 - 334 lbs/in at the wheel).
Hope this make sense, but believe me, what is above is 100% correct. I can fax you the Porsche motorsport sheet if you think it will help.
08-25-2012, 09:44 AM
#19
Nordschleife Master
I have read that before about it being 42% and maybe that is for the Escort Cups or similar coilovers that mount directly to the arm. I use the lower strengthening mount and maybe that changes the orientation and therefore the measurement.
I physically measured mine a while back. Moving the center of the tire contact patch up 1" causes an average 9/16" movement between the spring plates (springs removed). That equates to a 56% ratio on my set-up so I don't think that number is a myth.
I physically measured mine a while back. Moving the center of the tire contact patch up 1" causes an average 9/16" movement between the spring plates (springs removed). That equates to a 56% ratio on my set-up so I don't think that number is a myth.
08-25-2012, 10:09 AM
#20
Drifting
Thread Starter
I didn't mention the 56% figure on any great authority, so it's interesting to hear that it might be even lower. It's academic to me in my application since there are other greater variables, but interesting nonetheless.
I'm not quite sure that I understand how static deflection influences suspension frequency.
I'm not quite sure that I understand how static deflection influences suspension frequency.
08-25-2012, 12:41 PM
#21
Rennlist Member
There is so much discussion on rear suspension setups in these forums. Anyone reading this one is well advised to search many of the existing threads on this topic, as there are some misunderstandings and confusing statements made in this thread.
08-25-2012, 04:27 PM
#22
Three Wheelin'
I have read that before about it being 42% and maybe that is for the Escort Cups or similar coilovers that mount directly to the arm. I use the lower strengthening mount and maybe that changes the orientation and therefore the measurement.
I physically measured mine a while back. Moving the center of the tire contact patch up 1" causes an average 9/16" movement between the spring plates (springs removed). That equates to a 56% ratio on my set-up so I don't think that number is a myth.
I physically measured mine a while back. Moving the center of the tire contact patch up 1" causes an average 9/16" movement between the spring plates (springs removed). That equates to a 56% ratio on my set-up so I don't think that number is a myth.
08-25-2012, 05:31 PM
#23
Nordschleife Master
If you want the wheel rate, i.e: the rate at which the wheel moves compared to the rate of the spring then your calculation is correct.
08-25-2012, 07:39 PM
#24
Rennlist Member
Nice to see that email get another airing. 
08-26-2012, 10:03 PM
#25
Three Wheelin'
600*(0.56)^2 = 188
Cheers,
Mike
Last edited by mikey_audiogeek; 08-26-2012 at 11:17 PM.
08-26-2012, 11:16 PM
#26
Three Wheelin'
Hi Patrick, you gonna cite me for copyright infringement? How mucha I oweya? <chuckle>
08-28-2012, 08:53 PM
#28
Intermediate
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I have too running without torsion bar with a set of recently installed Intrax RSA from Lindsey Racing. The car is sitting at the right height but I run into problem not able to adjust proper camber or toe. The minimum camber the mechanic could get is -2.5 but with crazy amount of toe, but when he adjust for the correct toe, the camber with go -4.0. Tried to adjust the ride height using the eccentric in the spring plate, the axle only move for a few mm. Is this to do with the removal of the torsion bar?? Or is there something we have missed?? Thanks for your help!!
08-28-2012, 11:59 PM
#29
Drifting
Thread Starter
I have too running without torsion bar with a set of recently installed Intrax RSA from Lindsey Racing. The car is sitting at the right height but I run into problem not able to adjust proper camber or toe. The minimum camber the mechanic could get is -2.5 but with crazy amount of toe, but when he adjust for the correct toe, the camber with go -4.0. Tried to adjust the ride height using the eccentric in the spring plate, the axle only move for a few mm. Is this to do with the removal of the torsion bar?? Or is there something we have missed?? Thanks for your help!!
What is the ride height now? (It's probably easiest to measure from the ground to the top of the wheel arch on the body)
And
Do you still have rubber spring plate bushings, or have you replaced them with solid bushings?
08-29-2012, 12:04 AM
#30
Drifting
Thread Starter
Thanks to Richie's help at Hyperco, I was able to find a set of 1" spacers from another vendor that should get me into the adjustment range on the rear shocks. They should be here this week, so I'll finally be able to get the car leveled.