what pound springs are you track people running up front
05-15-2012, 11:12 AM
#61
Rennlist Member
If anyone cares, in my 944 I'm running about 2.3 Hz on the front and about 2.5 Hz in the rear*.
Car weight is 2650 lbs and I have 400 lb front springs and 31mm torsion bars*.
* note: I don't actually know the size of my torsion bars... but I think they're 31mm.
Car weight is 2650 lbs and I have 400 lb front springs and 31mm torsion bars*.
* note: I don't actually know the size of my torsion bars... but I think they're 31mm.
05-15-2012, 11:24 AM
#63
Drifting
I used 1 inch of total travel to make the math easier. If I'd used 2 inches, I'd have had to divide my strut measurement by two - and, with stiff track springs, I think 2" of suspension travel isn't very realistic.
Someone made the point earlier about suspension frequencies - and that's all very important and valid. It's been a while since I've ready my racing books, but I seem to recall that non-aero race cars are usually in the 2-4 Hz range. An F1 car is 10 Hz and Grandpa's Cadillac is about 0.5 Hz.
I see in my 944 setup spreadsheet that I'm using: 187.8 * (sqrt (wheel rate / sprung weight)) to calculate frequency at each corner in Cycles per Minute - then divide by 60 to get Hz (cycles per second).
05-15-2012, 12:02 PM
#64
Rennlist Member
Another reason for only moving the wheel 1" - my dial indicator only has 1" of travel...
05-15-2012, 02:27 PM
#66
Rennlist Junkie Forever
Just got my Escorts revalved at Bilstein for 750 front and 1200 rear :-)
TonyG
TonyG
I've been trying to say this for a while now. Ride frequency plays a huge roll in ride quality and the whole car handling any surface imperfections (bumps). You normally want a higher ride frequency in the rear to allow the rear to catch up with the front.
If I ever get around to getting these Bilsteins I've got revalved, I am going to match the rates to somewhere around 700 front, 1000 rear and yes, this will be street driven. Right now, I'll be aiming closer to what the base valvings are with 350 front, 525 (225 helper + stock t-bars) rear.
If I ever get around to getting these Bilsteins I've got revalved, I am going to match the rates to somewhere around 700 front, 1000 rear and yes, this will be street driven. Right now, I'll be aiming closer to what the base valvings are with 350 front, 525 (225 helper + stock t-bars) rear.
05-15-2012, 02:30 PM
#67
Rennlist Junkie Forever
A couple of points to make:
1) there should be several data points taken , not just 1" of wheel movement
2) The front should be done with strut at an angle using camber plates to replicate what you will see on a track car.
TonyG
1) there should be several data points taken , not just 1" of wheel movement
2) The front should be done with strut at an angle using camber plates to replicate what you will see on a track car.
TonyG
The last time you posted your measurements, you said .64 for the rear. The same thread mentioned .65 from Porsche themselves and I also measured .65.
https://rennlist.com/forums/924-931-...ive-rates.html
https://rennlist.com/forums/924-931-...ive-rates.html
05-15-2012, 03:53 PM
#69
Rennlist Member
Sure, the spring's units are rated in lbs per inch - so a 400 lb/in spring will take 360 lbs to compress 0.9". It's all linear math (since [most] race springs are not progressive [I understand that 944 Turbo Cup springs are, in fact, progressive]).
05-15-2012, 10:11 PM
#70
Three Wheelin'
All the markings on the shock and strut housings are identical to the Escorts(?) so my money is on them being unmodified. Although, don't forget that Bilstein themselves have changed the valving spec at least once, IIRC.
Cheers,
Mike
05-15-2012, 10:32 PM
#71
Drifting
FWIW, after having tested a bunch of springs on a Roehrig shock dyno/spring rater, linear Eibach springs are more consistently linear than Hypercoil and H&R in that order. Whatever they have scribed on the end is pretty much what you get through the usable travel of the spring.
And since they all are pretty much the same cost, go with Eibach.
And since they all are pretty much the same cost, go with Eibach.
05-16-2012, 12:50 PM
#72
Race Car
FWIW, after having tested a bunch of springs on a Roehrig shock dyno/spring rater, linear Eibach springs are more consistently linear than Hypercoil and H&R in that order. Whatever they have scribed on the end is pretty much what you get through the usable travel of the spring.
And since they all are pretty much the same cost, go with Eibach.
And since they all are pretty much the same cost, go with Eibach.
05-16-2012, 02:25 PM
#73
Drifting
6" to 10" lengths, 2 1/4 and 2 1/2 ID and 350lb to 1200lb rates. We basically grabbed every spring in the shop and ran it. Including some Porsche Motorsport adjustable rate springs and H&R progressive "lowering" springs for a RSA and stock M030 just for fun.
A lot of springs.
A lot of springs.
05-16-2012, 07:55 PM
#74
Rennlist Member
I think he was referring not necessarily to outright spring length but to number of coils per inch. The 'coil density' (if I may) is most often dictated by the amount of total displacement required. Also, the coil density is directly proportional to the torsion applied on the spring material. From a mechanical properties standpoint, the torsion applied should be a constant spring rate, regardless of the displacement/torsion applied. However, from a real-world material properties standpoint it is often difficult/expensive to ensure a truly homologous/uniform material. These micro defects (dislocations, grain size nonuniformity) become more noticeable at higher displacement/torsion applications. Consequently, I could see it being easier to ensure a high-quality spring if the spring had a lower coil density.
Now, it's worth noting that the big companies are excellent at ensuring material uniformity. Eibach in particular is known to be very good.
Now, it's worth noting that the big companies are excellent at ensuring material uniformity. Eibach in particular is known to be very good.