My rear universal joint is located about 2.5 inches directly under a cross bar under the rear seat. Before I got this rig on the road I thought that would probably cause me trouble, and I was right - the two collided a couple times in the little amount of time I drove it last summer. The car has what looks to be 4.5" OD coils approximately 12" in height. I am wondering what I'm missing when I consider just increasing my spring height 2-3 inches. I would like a bit more of a rake on the body anyway. I know I would have to adjust the hairpin connections on the rear end and check my shock absorber length. But it seems like a simple fix - maybe it should have had the longer coils all along! This was all done before I got it. I would appreciate any thoughts on the subject.
Taller coils for clearance
- Thread starter Edd
- Start date
choppedtop
Well-Known Member
Ed, you are saying you have coil springs only and not coil over shocks? If so, that should work. Just make sure shock are right length so as not to let the coils escape should the rear of the car get air born. A photo or two may help. I had a setup (like what I think you have) on my coupe years ago. I started off with long coils, and adjusted to shorter as I found the correct ride height without anything bumping or hitting.
Lee
Lee
SRM1952
Member
How much downward suspension travel do you have before the driveshaft hits? If you have a lot over 3 in. you can add a snubber to limit the travel . you can add a little spring rate, a thicker wire and or less coils will stiffen up the spring rate. You can check your spring rate with someone who deals with stock car racing equipment , most street stock cars use a 5" coil spring . The great thing about coil springs or coilovers is the ease of changing spring rates . Remember a taller spring does not mean stiffer , more coils or thinner wire is softer spring rate . So a 14 in spring with more coils may end up collapsing to the same chassis height you have now and be softer . A lot to think about.
Thanks for your replies. I do have non-coil over suspension Choppedtop, however the shock happens to be mounted inside the spring. Seems odd that the shock is the only thing keeping the springs from coming out if the rear end dropped suddenly. I have been looking at what Speedway has available for non coil-over coil springs and it occurs to me that I have no idea what the spring rate is on the springs I currently have. As you say SRM1952, I could simply go up in spring rate, but with only 2.5 inches of suspension before it hits, I wouldn't mind having more travel. The spring rate must be pretty stiff right now to only deflect 2.5 inches on the largest bumps. I keep the rear tire pressure rate down to get a little softer ride. What is a common spring rate for a T-bucket coil set up like mine, where the springs are located behind the axle, inside the frame rails, standing straight up and down? Would I be able to determine the spring rate if I took them out? Does a stock car racing equipt. shop have a means to determine spring rate? A lot of questions!! I appreciate the help.
Indycars
Well-Known Member
Why not just calculate the spring rate .......
Automotive Spring Rate Calculator
Spring Rate Calculator - Spring Calculator
Compression Spring Constant Equation and Calculator | Engineers Edge
Are you sure it's not the shock that needs to be stiffer. I had a similar problem
and bought QA-1s that are adjustable.
http://www.summitracing.com/parts/qa1-ts505
Automotive Spring Rate Calculator
Spring Rate Calculator - Spring Calculator
Compression Spring Constant Equation and Calculator | Engineers Edge
Are you sure it's not the shock that needs to be stiffer. I had a similar problem
and bought QA-1s that are adjustable.
http://www.summitracing.com/parts/qa1-ts505
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Wow Indycars, I guess I'll just calculate my own spring rate then! Thanks for the tools. I'll have to get to it this weekend. I guess I could fix the problem with an adjustable shock. I always think of shocks as controlling rebound - not compression. But an adjustable shock can apparently do both. I do like the idea of having more suspension, but if I got the wrong spring rate, I would have the same problem. I guess I would definitely be getting the adjustable shocks then.
Guild - I could gain probably a little more than an inch if I were to "C' the cross bar, but the magnitude of the job, and the fact that I would never be able to get the candy apple paint redone prevents me from seriously considering it. I'm looking for that easier (lazier?) way.
Thank you for your replies
Guild - I could gain probably a little more than an inch if I were to "C' the cross bar, but the magnitude of the job, and the fact that I would never be able to get the candy apple paint redone prevents me from seriously considering it. I'm looking for that easier (lazier?) way.
Thank you for your replies
Indycars
Well-Known Member
All shocks controls both. Now there are 90/10 for the front of drag cars that
come up very fast and go down very slowly to help with weight transfer. But
most normal shocks are pretty close to 50/50, a spring doesn't care witch
direction it's going.
QA1 and others make shock of vary stiffness, but again you would have to
know what was needed, where adjustable shocks you can fine tune without
another purchase.
But why? Millions upon millions of factory cars are made that way. A Chevelle comes to mind along with all the other GM cars in that family.
Well, the main reason that comes to mind is the difference in weight. It takes a lot more to get the double or more weight of a Chevelle airborne to the point of fully extending the shocks and/or completely unloading the springs. On the other hand, the closer to T-bucket weight MGs that I spent a lot of years driving, working on, and racing; came from the factory with limiting straps.
Personally I'd rather go with the minimal expense of limiting straps (and bump stops) than the greater expense of replacing ruined potentially expensive shocks, or the more dire consequences of loosing one or more spring while at speed.
I'll have to admit Indycars, that it has been a while ago since I heard anyone talk about their new "double action" shocks. You learn something new every day. That adjustable shock route is making alot of sense to me. If I wanted to go with longer springs in the future, can I use shock extensions, or am I looking at new shocks? With the current springs and 2.5 inches of clearance, or even with longer springs, I believe a bump stop would be a good idea, as Zandos recommends, and I assume RPM would agree, since all stock I am aware of automobiles have bump stops, but good lord, what an ugly addition to the rearend on a T-bucket, which is quite often (as my 8 inch ford is) all painted up pretty and fully exposed. Anyone have a picture of a workable bump stop setup?
How close does your axle come to the frame at the top of it's travel? A lot of bumpstops require no more than pads on the underside of the frame, that extends down far enough that the axle hits it before over extension. I'd do a search over on Summit Racing's site...they have a pretty good selection of sizes, shapes, and material.
Yes, that's the thing, the axles are about a foot from a frame rail, however the pumpkin is closer (obviously). Not sure if it is directly underneath a cross member though. My T-bucket is in town and I am out here on the farm, so I can't just go look at it unfortunately. I'm going to go take a look through my Summit catalog and see what I find. Hey, it looks like I could actually post some photos now. Guess I'll try to figure that out.
fletcherson
Well-Known Member
You can get bump stops that simply slip on the Shock piston, and will work fine in a light car, as long as you aren't counting on them to be or replace a spring. imho. And for the strap, from my understanding, you have coil springs with shocks inside. There is no way the spring will escape. If you encounter a issue that causes that, the spring loss is the least of your concern, it would be very unlikely that the shock would allow the spring to expand fast enough to have the required force to break it anyways, plus gravity, friction, and the geometric limits of the other components. I think the straps were designed for cars that mounted shocks independent from the spring, or even different type shocks and are more for keeping the parts connected in the event of a catastrophic accident, ie, nascar, etc...imho. I personally wouldn't give it a second thought.
True about the inside shock keeping from completely losing a spring, but it may still end up not seated correctly. Another option to a limiting strap would be one of the coil spring retainers frequently used in off-road coil suspensions. Of course to each their own.
For my build, I'll be using air bags with internal stops, and bump stops on the frame. I'll be checking with the bag manufacturer on the need for limiting straps.
fletcherson
Well-Known Member
If I had an issue where the spring unseated, yea maybe, but that would be very unlikely if they were properly sized and installed. There are likely other issues at that point. Not to be arguementive, I just don't see it being a concern, especially in the process of initially building a bucket on a budget... Bigger fish to fry! Lol...airbags are a different topic...
No argument seen...There is a good chance that your views on the matter are more relevant than mine. As I said in my original post, "I could be wrong".
On the air bags, I'd originally planned on coil overs, but the bags addressed too many issues to be ignored. They allow the car to be "kneeled" to allow climbless getting in & out...they allow compensation for power chair trailer towing loads...they should give a smoother ride...and the initial configuration using schrader valves instead of a compressor and tank, is actually cheaper than coil overs.
Indycars
Well-Known Member
I don't know that you couldn't use a shock extension, but you may
not even need it with taller springs. Try to get a shock that has a ride
height just below the middle. For example..... total shock travel is 5
inches then ride height would be 2 inches leaving 3 inches in rebound.
That's one reason for buying an adjustable shock, so you can adjust
for such situation if they seem to happen alot.
I don't run a bump stop, just not worried about it since I can't contribute
a single failure to shock bottoming. A bump stop on the center section
does not guarantee that a right wheel shock will not bottom out. Although
it is going to help no doubt, just no guarantee unless you have a stop on
EACH wheel.
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