Rat.L.- While very correct, There is one point You have left out- (towards the displacement theory)- and that is how tube aggle will effect the fluid level inside the shock when combined with poor placement. Example. Not all shocks are created equal. most assume that they are "filled to the brim" with dampening fluid (or viscous fluid, Oil, earl, or whatever You want to call the liquid inside a shock.)- this is not neccecarily true. the "el cheapo" 50-50 shocks pete and Jakes wants to sell You are, because they have no gas charge. most of our pre 64 stuff is like that. it's basically a fancy butterchurn. angle on this type of shock will likely have very little effect on dampening force due to angle, because they (sorry) kinda suck like that. However. a gas charged shock has a certian percentage of compressed gas in it. what that means is, as the shock's plunger moves up and down through the fluid, in theory, the charged gas helps return the plunger to to it's "resting position" as quickly as possible for "tha next bump". now, if You tilt one of these shocks, the fluid level inside stays paralell with terra firma (ain't gravity swell?) while the plunger gets farther and farther from it. it is possible, after about 20 degrees or so, to begin to aereate the fluid inside the shock. which makes the fluid much less effective. (don't bubbles suck?) this is also why on alot of gas charged shocks, while installing, You will notice they have alot more "body" to them, and you have to move it farther into it's travel before bolting it's argumenative butt in place. (pressure is kewl until it's working against You.) so, in effect, control Your body roll with mechanical means. keep Your shocks as far to the outside of the axle and as close to straight up and down as possible.
Yes, that force is called "nose pressure" and is determined by the internal charge and shaft diameter. If you're attentive, you'll notice it takes a certain amount of force to initially compress the damper but, once it's moving, you need'nt add force. This is because the force is generated by the gas pressure pushing back against the fluid being displaced by the shaft as the damper compresses, which isn't much. As for non-gas charged dampers: they still make those things??!! Actually, a proper, non-charged shock is still built (or should be built) such that there is no air in the tube when its capped but that's whole other story in itself...
I would just like to add that while you may be able to find a shock at your local parts store that fits the parameters of your build, that doesn't necesarily make them a good choice. I have been to shock school for sprint cars, and learned alot about valving. If you are seeking to maximize the ride quality and improve handling, I highly recommend Bilstein shocks. While not accepted in this community as being traditional, Bilsteins are available tailored to your needs. They are a gas pressurized mono-tube shock, and you would be absolutely amazed if the difference you exchanged your old twin-tube shocks with a set of Bilsteins. I have sold every brand available over the years, and Bilstein is now my only recommendation. As far as shock angle is concerned, I will add that on a rear triangulated 4-link, the recommended mounting angle is 27 degrees. Again, this helps the shock to work in a larger range, and also allows for sway control as well. A sway bar on the rear is a good idea too, but only if you are running one on the front. Without a front sway bar and one on the rear, my experience was that the car was "loose" on off ramps, meaning that the rear of the car felt like it wanted to pass the front. Once I installed a front sway bar, all was good. Great thread by the way.
If it hasn't been said already, a lot of cars and trucks with rear parallel leaf springs mount one shock in front of the axle and one behind the axle. It helps a little with keeping the axle from twisting on the leaf springs when you floor it or slam on the brakes, and helps control wheel hop.
KustomF100, your anti-roll bar experiment is an excellent example of how the various components interact. Simplified, springs give you your ride, roll bars give you your handling balance, dampers control the whole mess. You're a brave man driving around with no front bar but with rear bar connected!
Rat L Can, I did that twenty years ago, and I will never forget it. Took an off ramp at a speed faster than posted and effectively had to give my best Steve Kinser impression. Installed a front bar, and all was good. I see that you are employed by the racing community..Indy cars, or sprints?
Ha! You know You're in trouble when time freezes and Waylon Jennings starts talking about How You didn't know the bridge was out....
Indy Cars, but I pay cash-money to go to Sprint car shows, especially non-winged at Eldora and do the same for any Top Fuel show I can get to!
Guys, thanks to you all for your questions and answers so far on this topic it has been invaluable reading for me and I am glad I asked you.
Is there any compromised when using coil over shocks? Say the correct angle for the shock is not so workable for the coil etc.
IN MY EXPERIENCE (which may be worth NOTHING in reguards to Your vehicle) A coil over- especially a good double adjustable- is less effected by angle than a "normal" shock. I believe this is because the coil itself changes the shock dynamic so much. HOWEVER. I may have simply gotten very lucky this far. 99 percent of the coil overs I have installed have been almost perfectly straight up and down, and only really changed angle when both the front wheel came off the ground at launch. The few I have seen at say...a 20 degree angle...seemed to vastly outperform a "basic" shock in the same application. again. Just my personal experience.
With a "coil-over", you lose effective wheel rate (the spring rate the wheel "sees") as you increase the angle. This because you're reducing the motion ratio: wheel movement versus shock movement. In other words, as you add angle you lose spring rate and damper effectiveness - 2 for the price of 1..!
What about how the shocks and springs are on a Indy car, is this a bad compromise? Would anyone build a hot rod using this set up?
You guys have the angle stuff covered but, while we're talkin' shocks here is something that I found. In a effort to get a better quaility shock I took Pete & Jakes ("designed for transverse spring") open and compressed distances and end types and cross them over. Guess what 63 -82 Corvette rear matches. Duh... buggy springs... Smokey
The problem is it is subjective as to what a good ride or good handling are. If someone thinks a Chevy Avalanche handles or rides well then a ride in a modern BMW would make their head spin. No insult meant but just making a point as to when listening to what someone is posting be clear on what your own objectives are. Most rods are just not pushed to the limits where the shortfalls are made clear. Goodguys slalom might change all of that soon. Do you really think 5 degrees of shock tilt are going to help on a straight axle car exiting a highway at 55 mph? there are bigger issues to address. Then again maybe attacking all the smaller issues would? Wasn't there an old idea to get in the ballpark to point the lower end at the inner edge of your rear tire? Great info posted but in reality we are limited to generic products sold and lack of the ability to run tests on what we install. Most cars do to packaging will mandate that the further you get out the more angle to clear frame rails and suspension components. Locating a lower shock mount on a ladder bar car is fairly easy compare to a triangulated 4 link car. Keeping in a moderate range and tune with the adjustability a good coil over offers letting a good suspension design do it's work. iNTERESTING READ!!
Interestly enough I was chatting with a guy who runs a jag rearend in his model A. He was saying that in his eyes a jag was traditionally a soft ride for the luxury end of the market and he was wondering if he moved his lower and upper coil over mounting points out board about 2 inches whether his ride would firm and improve his handling. When you look at a jag rearend from the back once the mounting points have been mentioned in these terms it looks like an obvious improvement proposal. I guess it just complies with what has been said earlier about mountintg your shocks as close to the wheel as possible.
This might be one of the best threads I've read on here, Ever! Real information and no drama. Part of the problem with our cars is an absolute lack of wheel travel, in "bump" or compression in particular. And the reality is no shock in the world is really going to help much with 2" of compression travel. I am very sensitive to suspension and shock tuning coming from a back ground of Rally and Off Road racing. I also had a room mate for a number of years that was a shock and transmission specialist on IMSA and Indy cars for a number of years. To try and improve my car I took P & J front shocks off my 32 and put on Bilsteins and there was very little perceptible difference. Just not enough travel. Spring rate is good for the amount of travel, there just isn't enough of it. On my 41 with a MII based front the Bilsteins made a world of difference over the Monroe's the kit came with. Why do late model Mercedes ride and handle at a standard everyone else tries to emulate? Soft spring rates with lots of travel and part of how they accomplish that is with quite long springs. Never going to happen in our cars. The other interesting thing is look at Formula cars that Don't use rocker arm suspension and you regularly see the coilovers at approx. 45 degrees. Hmmmm
Well said. Coincidently my daily driver is Merc CLS500 - a remarkable piece of machinery that does everything incredibly well. Thing is, it was designed at a time where knowledge about chassis stiffness, frequency, the use of a tuned-mass damper, etc., existed. Most of these concepts were just that, concepts, when our jalopies were designed. To try and get our cars to ride and handle like a current day Mercedes or BMW would be an exercise in futility not to mention incredibly expensive! As I said in one of my previous posts, we can get a decent ride out of ladder-style chassis but you'd wind up with very soft springs and dampers, to offset the chassis' lack of rigidity, and this would then force you to run ride heights far higher than desired. Again, there's a trade off between getting the "look" or stance we're after and ride quality. Personally, I like the front in the weeds and the ass in the air (who doesn't...) just like any decent '32 highboy...If yo're willing to put up with quite high ride heights, then you'd spring and dampen the car quite soft and then fit stiff anti-roll bars to give the car some stability. This is very much what current manufacturers like Audi, VW, etc., do to their road cars - along with features like active dampening, etc. Also, most current Formula cars use pushrod suspensions. The pushrod connects to a bell-crank that in turn operates the spring/damper. This is done primarily for aero reasons but it does allow for different motion ratios and rising rates to be used by simply swapping rockers. Typical motion ratios are a linear 1:1, front and rear, for oval racing. For road racing, usually we add rising rate to the front and go to a "slower" rear motion ratio, like 1.3:1, to obtain the softer wheel rates we need for low speed grip. Obviously, dampening is changed to suit as well.
Hmmm. Rat brought up one of my favorite theories that is often left out of a standard discussion on Hot Rod chassis- frequency. the idea behind it is that any spring-ANY spring has a certian amount of tremor to it -just like a guitar or piano spring- and that controlling or dampening that vibration leads to a much better perceived ride. the major point of control here is dampening force- usually held in accord by the shock. My question is twofold. on a leafspring, we look back and see the springpacks being "bound" together with straps to help with axle wrap, and to keep them from "squishing" around. I wonder if a couple straps on a transvers leaf would help, or hurt... and... Isolators help a ton. I have seen the teflon spring liners for transverse. I can't help but wonder if they do such a good job on shutting up squeaks, how to the effect dampening themselves?
^^ Isolators do reduce squeaks because they reduce friction. And friction is a biggie too. Reducing friction is important as it is far more temperature, etc., sensitive than dampening and springing. Because of that, we want to reduce friction as much as possible as friction is very difficult to quantify or model consistently. What we want to do is have minimal friction so that our quantifiable factors (springing, dampening, etc.) are repeatable. That way we can measure improvements accurately. A leaf spring is a good, inexpensive axle mounting system-it locates the rear end and suspends it at the same time - but it's also has a lot of inherent friction and "monkey motion" as its downside. Now a lot of you might say "well GM, Ford and Chrysler have used them for years" and you'd be right. That's one reason that their cars are reasonably priced but are also critized for being less civilized than their European and Japanese counterparts. (That said, I still think US autos are excellent value for money; a BMW 5 series costs twice what a Chevy Malibu does. Is the BMW twice the car..?) Also, as LUXBLUE mentioned, frequency is another important factor in ride/handling but its complexities are for another thread altogether! And that'll be a REALLY long thread.
Rat, I really am enjoying your insight. Reminding me of things I hadn't thought about in a long time and more I never really knew But man your avatar is kind of freaking me out
Some more free reading. http://books.google.com/books?id=T7...&hl=en&sa=X&oi=book_result&resnum=2&ct=result
Great thread... So about how much shock action do you really get... Say, at the rear of a 32 frame with maybe 5"-6" of total travel, the shocks mounted to the axle about 6"-8" from the end of the axle and at about the recommended 10 degree angle? Doesn't seem like they would really do a lot. Especially when only one wheel is moving. Is this a concern? Secondly, how do lever action shocks fair in this discussion? Butter churns...
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