Motons Arrived
08-26-2002, 12:03 AM
#16
Race Car
[quote]Originally posted by belz:
<strong>Karl @ Racers Edge was running somewhere around 50 -60% of the front wheel rate at the rear. I went to +75% and like it. Previous,I was running ~equal wheel rates fr/rear and the car was (951 race car)very tail happy (oversteer)!
Suspension set up is personal but again, IMHO 650/663 will result in an oversteer condition that even the adjustibility of MOTONs can't cure.</strong><hr></blockquote>
Excellent info [even though it's subjective], thanks for posting that.
<strong>Karl @ Racers Edge was running somewhere around 50 -60% of the front wheel rate at the rear. I went to +75% and like it. Previous,I was running ~equal wheel rates fr/rear and the car was (951 race car)very tail happy (oversteer)!
Suspension set up is personal but again, IMHO 650/663 will result in an oversteer condition that even the adjustibility of MOTONs can't cure.</strong><hr></blockquote>
Excellent info [even though it's subjective], thanks for posting that.
08-26-2002, 02:34 AM
#17
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"You could get heavier springs and do away with the torsion bars. In my case even with the new Motons I'm leaving the torsion bars in the car.
After talking with Dave Schardt of the Wheel Source and John Wright of Schumacher Racing they don't see a problem leaving the bars in the car."
As long as I'm throwing my opinions around... here's another one!:
I removed my torsion bars this season and went to a full coil-over set up from a helper spring/ torsion bar set up.
What a difference! The car is much more linear and tracks spot on. With the helper spring set up, and at the limit, I always felt like I was "chasing" my rear end. Even when I minimized the oversteer issue the helper spring / torsion bar set up was not progressive. My observation is as you increase the spring rate of the helper spring the less progressive the suspension movement. I noticed this once I went over a 100lb. helper spring.
Thus, in my opinion, if you are going to use over a 100lb. helper spring then you're better off eliminating the torsion bars altogether and going to a full coil-over set up.
(I'm not an engineer but I'm sure there is an explanation here that has to do with the difference between a "coil" spring and a "bar" spring ... i.e. load / pre-load / rate of rebound / rate of compression / etc. etc.)
After talking with Dave Schardt of the Wheel Source and John Wright of Schumacher Racing they don't see a problem leaving the bars in the car."
As long as I'm throwing my opinions around... here's another one!:
I removed my torsion bars this season and went to a full coil-over set up from a helper spring/ torsion bar set up.
What a difference! The car is much more linear and tracks spot on. With the helper spring set up, and at the limit, I always felt like I was "chasing" my rear end. Even when I minimized the oversteer issue the helper spring / torsion bar set up was not progressive. My observation is as you increase the spring rate of the helper spring the less progressive the suspension movement. I noticed this once I went over a 100lb. helper spring.
Thus, in my opinion, if you are going to use over a 100lb. helper spring then you're better off eliminating the torsion bars altogether and going to a full coil-over set up.
(I'm not an engineer but I'm sure there is an explanation here that has to do with the difference between a "coil" spring and a "bar" spring ... i.e. load / pre-load / rate of rebound / rate of compression / etc. etc.)
08-26-2002, 04:04 AM
#18
Race Car
Interesting. So did you find that the differential between front and rear wheel rates changed when you upgraded to a full rear coilover instead of the torsion bar/helper coilover setup or did the fundamental balance of the car at the limit remain the same? I can't visualize whether a car with a more progressive tendency in the rear end will require a different spring rate in the rear to balance things out. Thanks! 
Out of curiosity, what would you guess is the wheel rate conversion with a rear-mounted coilover? Somewhere between .5-.6 of the spring rate is what I've read, while torsion bars are nearly 1.
Out of curiosity, what would you guess is the wheel rate conversion with a rear-mounted coilover? Somewhere between .5-.6 of the spring rate is what I've read, while torsion bars are nearly 1.
08-26-2002, 01:05 PM
#19
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Great question! I've never thought of it that way so I don't have an answer ...
The point I was trying to make regarding a helper spring / torsion bar set-up is that (IMO) at some point the two "types" of springs (coil & torsion bar)don't work together well (i.e. synergy) and actually create a non-linear suspension movement. One that cannot be "tuned" with bars or shocks etc. I'm sure there is a mathmatical equation that takes into account the size of the bar and the strength of the coil. My "seat of the pants" method suggests that with a ~30mm bar the limit on the coil is ~100lbs.
When I chose my coil over set up I used a .6 factor to determine the wheel rate. This was based more on the rear suspension geometry than taking into account any difference between a coil spring or torsion bar.
My "seat of the paints" method for determining my set-up was to start with the desired front spring rate (wheel rate) and work backwards (literally). Then choose a rear spring weight that is ~75% of the front wheel rate (utilizing the rear "wheel rate" factor of .6)
Thus your rear "spring" rate will be higher than your front but due to the .6 "wheel rate" factor the rear wheel rate will actually be less than the front.
The point I was trying to make regarding a helper spring / torsion bar set-up is that (IMO) at some point the two "types" of springs (coil & torsion bar)don't work together well (i.e. synergy) and actually create a non-linear suspension movement. One that cannot be "tuned" with bars or shocks etc. I'm sure there is a mathmatical equation that takes into account the size of the bar and the strength of the coil. My "seat of the pants" method suggests that with a ~30mm bar the limit on the coil is ~100lbs.
When I chose my coil over set up I used a .6 factor to determine the wheel rate. This was based more on the rear suspension geometry than taking into account any difference between a coil spring or torsion bar.
My "seat of the paints" method for determining my set-up was to start with the desired front spring rate (wheel rate) and work backwards (literally). Then choose a rear spring weight that is ~75% of the front wheel rate (utilizing the rear "wheel rate" factor of .6)
Thus your rear "spring" rate will be higher than your front but due to the .6 "wheel rate" factor the rear wheel rate will actually be less than the front.
08-26-2002, 02:32 PM
#20
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I went with Penske remote canister coilovers last year and found them to be a very positve addition, but extremely expensive. Especially compared to the price for the Motons.
I removed the torsion bars primarily to reduce the complexity of corner balancing and changing ride height. Of course there is always the desire to remove additional weight also! When you are down to around 2400lbs finding additional weight to remove becomes a lot more difficult and costly!
As far as springs go, I used a less scientific method and went with what "felt" best. I started with 700lbs up front with 600lbs in the rear. That was too stiff and I ended up doing a lot of bouncing around the track so I dropped down to a 650/550 combo which has worked extremely well. Now, I also have the ability to change rebound and compression very easily (with remotes) depending on track conditions, so I only need to have my spring rate within a rate.
My car had a bad oversteer problem last year which was helped with the lower spring rate, but I also helped it with not using a larger sway bar up front.
It is hard to say what all the differences in handling were because I made so many changes, but last year I spun at every event and this year in 20 days of driving I am yet to even get a wheel off and am doing much better times.
I removed the torsion bars primarily to reduce the complexity of corner balancing and changing ride height. Of course there is always the desire to remove additional weight also! When you are down to around 2400lbs finding additional weight to remove becomes a lot more difficult and costly!
As far as springs go, I used a less scientific method and went with what "felt" best. I started with 700lbs up front with 600lbs in the rear. That was too stiff and I ended up doing a lot of bouncing around the track so I dropped down to a 650/550 combo which has worked extremely well. Now, I also have the ability to change rebound and compression very easily (with remotes) depending on track conditions, so I only need to have my spring rate within a rate.
My car had a bad oversteer problem last year which was helped with the lower spring rate, but I also helped it with not using a larger sway bar up front.
It is hard to say what all the differences in handling were because I made so many changes, but last year I spun at every event and this year in 20 days of driving I am yet to even get a wheel off and am doing much better times.
08-26-2002, 02:50 PM
#21
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951 Racer:
Your "less scientific" method seems to be pretty good!
Calculating your approximate wheel rates:
Front: ~585lbs.
Rear: ~309lbs.
You are at the "Karl @ Racers Edge" ~50% mark.
With your Penskes you can change/increase the canister pressure to effectively raise the spring rate (to a point). Sounds like a pretty good set-up to me!
What psi are you running in your Penskes? (F & R)
Your set-up seems to confirm the 50-75% rear wheel rate (vs. front wheel rate) as the appropriate set-up in reducung/eliminating oversteer etc.. (of course there are other factors as you mentioned: sway bars etc.)
Your "less scientific" method seems to be pretty good!
Calculating your approximate wheel rates:
Front: ~585lbs.
Rear: ~309lbs.
You are at the "Karl @ Racers Edge" ~50% mark.
With your Penskes you can change/increase the canister pressure to effectively raise the spring rate (to a point). Sounds like a pretty good set-up to me!
What psi are you running in your Penskes? (F & R)
Your set-up seems to confirm the 50-75% rear wheel rate (vs. front wheel rate) as the appropriate set-up in reducung/eliminating oversteer etc.. (of course there are other factors as you mentioned: sway bars etc.)