Spring rates for Bilstein Cup coilovers with torsion bar delete?
11-04-2012, 11:08 PM
#46
Seriously Rob, you just seem to descend upon some threads and just bomb away. You have issues with Tony G, Chris and a few others. I'd seriously hate to be your Cat. All it appears from the outside is that you must have some precedent with which gives cause to these caustic posts. You attack people that have had a fair bit of documented experience in these cars and yet I can't recall seeing much history of your background. Not trying to belittle you and I'm sure you're very experienced but it just doesn't seem so by your outbursts. It makes me think that there must be some backstory but I can never find anything to validate why you lash out like you do. So in the end....I just don't get it????
Rob, I'm going to re-do my suspension this winter. Got some Pohlman A-arms going on the front. Tarrett sways front and back. Removing the t bars and going the coil-over route in the rear. I do about 15 days a year of DE and I'm thinking on running some races(the classics) at Tremblant. Basically a track car not yet a race car. What suspension setup and spring rates would you suggest?
thanks
11-04-2012, 11:32 PM
#49
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It's my understanding (and please correct me if I'm wrong) that the Escort's rear coil-overs have rubber in the bushings top and bottom... which I also understand may not be the most desirable thing when running without torsion bars.
So... what's the standard approach to going to solid bushings top and bottom with these rear coilovers?
Thanks.
Karl.
So... what's the standard approach to going to solid bushings top and bottom with these rear coilovers?
Thanks.
Karl.
11-05-2012, 12:08 AM
#51
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11-05-2012, 12:15 AM
#52
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11-05-2012, 01:14 AM
#54
RL Community Team
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Karl.
11-05-2012, 04:45 AM
#57
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I thought I spied 4 intertwined circles.
Lexus (Rob wins the Chicken dinner) huh? How much fabbing needed?
Lexus (Rob wins the Chicken dinner) huh? How much fabbing needed?
11-05-2012, 11:10 AM
#58
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I need some advice. I have some Leda coilovers with 450 lb fronts & 350 lb rears. The rates were recommended by Leda (who supplied the whole kit) as suitable for a club-racer or road/track car - I'm assuming with standard t-bars.
Running the calcs the 450 lb fronts will have an effective wheel rate (EWR) of 410 lbs and the rears using standard t-bars (177 EWR) will have an effective rate of 324. This yields a F/R ratio of 1.26. The rear effective rate equates to the equivalent of 773 lb springs w/o t-bars.
I also have some 27mm t-bars (220 lb EWR) - if I run the calcs again with those I get an effective rate of 367 on the rear, which yields a F/R ratio of 1.11. The rears will equate to a 876lb coilover w/o t-bars.
Using standard t-bars gives a softer rear but a much more front-biased F/R ratio. Using 27mm t-bars gives better F/R ratio but a very stiff rear which might be too oversteery.
I also have Tarrett F & R sway bars & a Guard 50/80 ready to go on this car.
Any advice as to which set-up to go for?
Tim
Running the calcs the 450 lb fronts will have an effective wheel rate (EWR) of 410 lbs and the rears using standard t-bars (177 EWR) will have an effective rate of 324. This yields a F/R ratio of 1.26. The rear effective rate equates to the equivalent of 773 lb springs w/o t-bars.
I also have some 27mm t-bars (220 lb EWR) - if I run the calcs again with those I get an effective rate of 367 on the rear, which yields a F/R ratio of 1.11. The rears will equate to a 876lb coilover w/o t-bars.
Using standard t-bars gives a softer rear but a much more front-biased F/R ratio. Using 27mm t-bars gives better F/R ratio but a very stiff rear which might be too oversteery.
I also have Tarrett F & R sway bars & a Guard 50/80 ready to go on this car.
Any advice as to which set-up to go for?
Tim
11-05-2012, 11:58 AM
#59
Rennlist Member
Tim, some of it is going to come down to your personal preferences and specific setup. Here are some rules of thumb to remember.
Softer settings for a particular end of the car provides more grip - e.g. more grip in the rear yields understeer; more grip in the front yields oversteer.
This applies to springs, damper settings, sway bars and tire pressures. But, softer settings have other draw backs - more chassis pitch, more chassis roll, bigger alignment changes under cornering, tires heating up more, etc.
Sway bars affect over/understeer balance mid-corner - e.g. at a steady-state point after the fore-aft weight transfer has happened.
Turn-in over/understeer is affected by the front shocks' bump or compression setting and rear shocks' rebound setting - e.g. as the weight is transferring forward and the spring are storing and releasing energy, which end of the car has more grip.
Track-out over/understeer is obviously the opposite because the weight transfers back under acceleration.
For the LSD, higher lockup allows for more controlled trailbraking and corner entry, because the back wheels are turning together; but, on corner exit, higher lockup keeps those rear wheels turning together and reduces steering (understeer).
For alignment, more negative camber can make a larger contact patch between the tire and the road under hard cornering, but creates a "triangular" contact patch on the straights that increases rolling resistance (and thus uses more energy).
Toe-in/toe-out also increases rolling resistance, but it can also reduce the slip angles needed to start turning the car - meaning the car turns in quicker/more aggressively. (If you want, think of it this way: if your front wheels have toe-in, when you're going straight, they both have a little bit of slip angle going on, but the slip angles are fighting each other. When you start turning, the inside tire will always have little slip angle fighting with the outside (loaded) tire. With toe-out, by the time the outside tire has some slip angle for turning, the inside tire has even more slip angle trying to turn in the same direction.)
Hope that helps.
Softer settings for a particular end of the car provides more grip - e.g. more grip in the rear yields understeer; more grip in the front yields oversteer.
This applies to springs, damper settings, sway bars and tire pressures. But, softer settings have other draw backs - more chassis pitch, more chassis roll, bigger alignment changes under cornering, tires heating up more, etc.
Sway bars affect over/understeer balance mid-corner - e.g. at a steady-state point after the fore-aft weight transfer has happened.
Turn-in over/understeer is affected by the front shocks' bump or compression setting and rear shocks' rebound setting - e.g. as the weight is transferring forward and the spring are storing and releasing energy, which end of the car has more grip.
Track-out over/understeer is obviously the opposite because the weight transfers back under acceleration.
For the LSD, higher lockup allows for more controlled trailbraking and corner entry, because the back wheels are turning together; but, on corner exit, higher lockup keeps those rear wheels turning together and reduces steering (understeer).
For alignment, more negative camber can make a larger contact patch between the tire and the road under hard cornering, but creates a "triangular" contact patch on the straights that increases rolling resistance (and thus uses more energy).
Toe-in/toe-out also increases rolling resistance, but it can also reduce the slip angles needed to start turning the car - meaning the car turns in quicker/more aggressively. (If you want, think of it this way: if your front wheels have toe-in, when you're going straight, they both have a little bit of slip angle going on, but the slip angles are fighting each other. When you start turning, the inside tire will always have little slip angle fighting with the outside (loaded) tire. With toe-out, by the time the outside tire has some slip angle for turning, the inside tire has even more slip angle trying to turn in the same direction.)
Hope that helps.
11-05-2012, 12:29 PM
#60
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Lexus IS-F.
I would need to have more data like which model 944, budget, purpose (will this track car be driven on the street?), weight, aero adjustments done outside of factory, tire and wheel sizes and brands, rough estimate of car weight, and car ride height. Basically as much information you can give me, the better.
I'm not sure if I have posted this before or not, but here are some great tech articles for springs and dampers:
http://www.optimumg.com/technical/technical-papers/
I would need to have more data like which model 944, budget, purpose (will this track car be driven on the street?), weight, aero adjustments done outside of factory, tire and wheel sizes and brands, rough estimate of car weight, and car ride height. Basically as much information you can give me, the better.
I'm not sure if I have posted this before or not, but here are some great tech articles for springs and dampers:
http://www.optimumg.com/technical/technical-papers/
Stock weight
Stock Aero
Stock power
Stock brakes
Right height dropped approx 25mm
Sway bars are usually adjustable
Stock diameter wheels/tires
wheels allowed to be 1" wider, typically 255 section width
shocks and springs are free