375lb vs. 500lb front springs

[jams]

Hi Guys,

I am going to convert to front coilover shocks in the front. The manufacturer recommends 375lb springs. I went a little heavier than recommended in the rear and I am happy with my decision.

I was thinking of going with 500lb springs instead of 375lb. As my wife says stiffer is always better.

In your experience would going with the 500lb springs be a mistake for a Small Block? I just don't want to hit bad road conditions and bottom out too easily. The QA1 shocks will have adjustable settings.

P.S. I tossed this around the B & B forum but I wanted to widen the scope a little.

[HighPlainsDrifter]

Hi,
I run 575 lbs on the dr front and 550 on the pass front ,250 in the rear.
Makes going around cloverleafs alot of fast fun.
Perry.

[Tim Brewer]

500 # front springs are going to be REAL stiff with a small block. Unless you run at the track fairly often, 500 is way on the stiff side. I have a big block with 350# fronts and it's not soft at all and has never bottomed.
Tim

[DavidNJ]

It depends on the geometry. Three different brands here.

[mj_duell]

To stiff for street driving. I have a 428FE up front of my A&C with 400# springs and it's stiff. I ran 350# out back which seems about as high as I would go.



--Mike / Turn Ten Racing, Inc.

[DavidNJ]

What shocks and geometry do you run? The ride is a function of geometry (primarily the relationship between the spring and shock rates and their rates at the wheel, tires, and unsprung weight.

A stiff shock will be harsh with a soft spring. A hard spring can be 'firm but pliable' with the right shock. Stiff tire sidewalls will be different then soft tires.

Coil overs cost around $60 each (Hypercoils or Eibach) and take about 30 minutes to change one end of the car (including set ride height and wheel weights). Why not just try out a couple?

[jams]

Don't know much about geometry. All I know is I have stock Mustang II suspension. I am going to replace it with QA1 shocks...they have 12 adjustment settings.

I know it is hard to compare apples and oranges when talking suspension but I just wanted to get a general sense. Based on what was mentions so far, I might go with the 375 pounders as suggested by the manufacturer. Worse comes to worse I can buy a new set for about $60.00.

Thanks for your input. I will check back to see if there are any new posts. QA1 shocks are out of stock from Summit until the 19th so I have time to think!

[jarendall]

I am running the QA1's front and rear, I have the 375# springs, I have adjusted them all the way up and my tire still scrapes the plastic inter fender on the frontend of my car whenever I hit a large bump, I would suggest you go with the heavier springs, you can always back them off

[Aussie Mike]

What's going to have a big impact here is where the bottom shock mount is in relation to the wheel. You have to think about your front lower arm as a lever on the shock. The further inboard the shock mount is the more leverage the wheel will have.

My shock mount is right out at the ball joint so a 500 pound spring is going to be really stiff in my car. Your shock mount may be half way along the lower control arm so a 500 pond spring might be OK. You really need to look at where the shock mounts are in relation to your pivot ponts and the point where the wheel hit the road and work out your "wheel rate". This is actual spring pressure at the wheel which is your spring rate multiplied by the ratio of your shock pivot position.

Another factor is the angle the shock sits at. In a vertical position the spring rate will be 1:1 but if coil over is mounted at an angle the spring rate is effectively reduced.

The small diameter springs for these coil overs are relatively cheap and very easy to change out. So you could run a sellection of springs. 500 pounders for the track and 400 for the street.

[DavidNJ]

As Mike said, geometry.

Also, if you bottom over a bump it is a shock issue not a spring issue. To the best of my knowledge, all race cars in every type of racing (maybe not drag racing) use mono-tube shocks. Some high end Carerra (bought by QA1). However, not the QA1 original line. Bilstein, Penske, Ohlins, Moton, some Konis are mono-tube.

[rblong]

I have FE, 350# front, 220 rear. Used to bottom on rear till I adjusted, Never bottom out front. Mine are both 10" coil overs.

[mzhun]

I swaped out the questionable Gabriel's with a coil to the QA-1's and had a an issue with the spring length that came with the Mustang II conversion. You also have to be careful that the shock lines up with the upper "cup" when lowering the car as it will bind and not allow the shock to travel. It is fairly easy but you still have to bust the two ball joints on each side which usually cuts the dust boot. Lastly, i don't know what backspace you used on the front but the B&B front tires sit pretty wide making them prone to rub the body on harsh street bumps.

[jams]

mzhun,

What spring length and weight finally worked?

[mgilbert]

greetings, i just changed MII front to QA1 w/375# springs got kit from speedway. they have kits for stock ride height-2" lowered one kit for 2"-4" lowered and a kit i got for all ride heights. the nuts on shock body are just about in middle of shock or 1/2 way. put on tube control arms also. seem much better, but i think some of that is control arm bushings shot rack&pin shot ball joints questionable. steers much easier still need to alighment. only driven about 2 miles testing. want to get alighment better before taking it somewhere to get it done right see ya Mark G

[Tom Howland]

jams,
I'm running 500# springs and like them. Using Pro Shocks and no sway bar. Have about 2" travel. It's stiff but I like it. Handles really well.

[mzhun]

they are the 7" springs that came with the Gabriel's and I don't know the spring rate, but it is too soft whatever it is so i am going to upgrade. I have the Addco sway bar so will probably go a little softer than 500#.

[quickquarter]

Quick question here.
Has anyone with QA1's or similar shocks tried changing the shock oil to a higher viscosity rating? Rather than stiffer springs?

[JCoop]

When I had the SB, I used Carrera shocks and springs. Springs were 375# all around, and I mounted the shocks upside down for less unsprung weight. Also, the fronts were 10", I went to 7" for more adjustability in ride height. Changed swaybar bushings and mounts F & B with polyurethane, greasable bushes on the mounts. The difference in handling and ride was night and day.

My current BB (but now with 17" wheels) has QA1s with 450# springs, again 10". With the shocks adjusted halfway, the ride scrambled my brains. I have bought 450# 7" Carrera springs for the fronts, still trying to find out if the shocks can be mounted upside down. With the shocks now at 2 clicks, the ride is much better; we'll see also after doing the poly swaybar bushings and mounts mod.

So I believe the current thinking for street is lighter springs, with a highly-progressive rate (not stiffer) shocks, will give a firm but smooth ride. The softer spring rate will allow the wheel assembly to move easier, with the initial compression of the shock going with it. Then, as the assembly nears maximum compression, the shock gets progressively stiffer, preventing bottoming out. Ideally, the rebound rate should be softer and more linear, so the assembly drops down to it's initial setting faster, preventing bounce. Won't work for the track, though.

[G.R.]

There are progressive rate springs available for QA shocks. I bought my shocks from Speedway and in talking with the rep he mentioned that the progressive rate springs might be a solution they are available in various spring rates though not advertised in the Speedway catalog.

If most of your driving is street you may not want/need a heavier spring rate