Front spring selection for 84-87

[pmbrunelle]

I want some stiffer springs for the front of my Fiero.

I looked at this catalog to find some Moog part numbers:
https://www.moog-suspension-parts.com/u ... prings.asp

A while back, I ordered Moog 5576, as it looked like it could be appropriate (with trimming the end off).

I often employ fast-tracking in my Fiero project, you know, to go faster. I ordered the Moog 5576 springs before I had the crossmember and LCAs apart for measurement.

I would say that I also order quickly, to avoid the risk of having a part become discontinued / unavailable in the meantime.

Moog 5576.jpg (1.03 MiB) Viewed 2569 times

Oops, they're too big! Happens sometimes with fast-tracking. The catalog dimensions appear quite close to the physical dimensions I could measure on the springs.

Another spring, Moog 2278 looks like it might be suitable for my car.

However, it appears not available, anywhere:

Summit.png (281.19 KiB) Viewed 2569 times

Interestingly, Mevotech has an "SMS2278":

Mevotech.png (54.44 KiB) Viewed 2569 times

The part numbers share a common sequence, and Mitsubishi and Dodge appear to be common applications.

I'm guessing that they're the same part, but that Moog divested (part of?) its spring business to Mevotech. When the Moog part numbers were incorporated within Mevotech, the SMS prefix was added.

Therefore, the Moog spring listing (with dimensions) still appears to be a useful resource to find springs.

[jelly2m81]

idk why anyone is still fucking wasting time with a pre 88 when A number of us are driving around on a cut pre 88 spring. The problem isn't the spring, it's your suspension as a whole.

[Shaun41178(2)]

idk why anyone is still fucking wasting time with a pre 88 when A number of us are driving around on a cut pre 88 spring. The problem isn't the spring, it's your suspension as a whole.

Bingo.

It's a fiero. Live with it or buy a kia

[pmbrunelle]

I suspect that I can get the car to where I'd like it to be, with the pre-88 architecture. That's why I'm messing with it.

[jelly2m81]

idk why anyone is still fucking wasting time with a pre 88 when A number of us are driving around on a cut pre 88 spring. The problem isn't the spring, it's your suspension as a whole.

Bingo.

It's a fiero. Live with it or buy a kia

Yep The Fiero is what it is, while I do enjoy it for what it is, I'm sure my Turbo Santa Fe is quicker, and my 3.0L Outback ain't no slouch either and sounds kinda glorious at 7K RPM and both those cars are more refined and well, they are a better car.

[neophile_17]

What is your target spring rate? Ride height? Shocks may also come into play.

The front springs from a 4th gen Camaro can be cut to fit but this will be quite stiff. A lowered ride height will require more to be cut off and increase the spring rate further. You will need either a performance shock or to adapt the G-Body shock like I did.

[The Dark Side of Will]

I suspect that I can get the car to where I'd like it to be, with the pre-88 architecture. That's why I'm messing with it.

Fabbing a suspension is the next logical step after fabbing a turbo kit

[pmbrunelle]

What is your target spring rate? Ride height? Shocks may also come into play.

The front springs from a 4th gen Camaro can be cut to fit but this will be quite stiff. A lowered ride height will require more to be cut off and increase the spring rate further. You will need either a performance shock or to adapt the G-Body shock like I did.

Initially, I decided that I wanted 400 lb/in springs on the rear. This was to just stay off the bumpstop with a combined loading of 1.25 g lateral and 2 g vertical.

Then, I decided that I wanted to try "flat ride", with rear ride frequency being 10-20% greater than front ride frequency.

With my estimations of sprung mass (measured axle weights, minus estimations of unsprung mass), I settled on the Moog 5576. When trimmed to the correct length, I think that the resulting 519 lb/in spring rate would give a 1.97 Hz ride frequency in the front, and a 1.14x R/F ride frequency split.

When choosing from a catalog like the Moog catalog, which are stock applications, not every spring diameter/length/rate combo is available. The Moog 2278 has a listed spring rate of 435 lb/in. This is less stiff than I had planned, but it's what's available... I may soften the rear a bit to to regain flat ride.

The general increase in suspension stiffness should make the response of the car quicker (in the time domain), which I think I will like.

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Planned ride height for this car is like stock. By calculation/estimation, I think an untrimmed 2278 will give me a stock ride height like I want. To be verified when actually installed on the car.

This is a low/moderate effort project car, so I'm not concerned too much with lowering the CG for less weight transfer. I'm not concerned about keeping a low profile to cut through the wind better. The only aero mod I'm planning on is a hood vent. I'm not optimizing this car for high speed.

With stock ride height, I can keep the front-view suspension roll centers up, meet my target of 1.25 g lateral / 2 g vertical without bumpstop contact (or overly high spring rates), and have ground clearance for speed bumps and light (such as a commercial campground) off-road.

This is meant to be a general purpose sports car / daily / road trip vehicle / maybe track toy.

Lowering the car does not appear make sense, given my goals with the car.

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I'm not sure what to do about damping. I figured I would take a baseline with the spring rates I like (and KYB dampers), and then address damping as required.

To work effectively without running around in circles, it seems like first the steady-state behaviour should be close, and then transients should be tuned in a second step.

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I just received the Mevotech SMS2278 springs today, and they appear to mostly fit OK. Of course, a stiffer spring is most likely going to have a larger wire diameter, so fitment with the spring perches becomes more finicky.

Rockauto is fast!

I suspect that I can get the car to where I'd like it to be, with the pre-88 architecture. That's why I'm messing with it.

Fabbing a suspension is the next logical step after fabbing a turbo kit

In my current understanding of my early Fiero's suspension, I think my main dislikes are:
High scrub radius, so steering kickback over bumps, and possibly tramlining weirdness.
Pro-dive, so dive during braking.

These two issues are to be addressed by the following measures:
Scrub radius: High offset Enkei front wheels (ET+48mm)
Pro-dive: relocation of forward LCA pivot (and steering rack)

Making a totally new front suspension is not out of the question, but I should first take a new baseline from a slightly tweaked stock suspension. If I like the tweaked stock suspension, great. If not, I can modify/redesign from there.

idk why anyone is still fucking wasting time with a pre 88 when A number of us are driving around on a cut pre 88 spring. The problem isn't the spring, it's your suspension as a whole.

Bingo.

It's a fiero. Live with it or buy a kia

Yep The Fiero is what it is, while I do enjoy it for what it is, I'm sure my Turbo Santa Fe is quicker, and my 3.0L Outback ain't no slouch either and sounds kinda glorious at 7K RPM and both those cars are more refined and well, they are a better car.

I don't think there's anything magical about a new car versus a Fiero or anything else. They're all made from more or less the same building blocks.

[neophile_17]

Fabbing a suspension is the next logical step after fabbing a turbo kit

This is the way. But beware, the rabbit hole is much deeper than it looks. On the bright side there is enough room for improvement that it's not the marginal improvement you might see on another chassis.

The '88 front doesn't have enough benefit to compensate for inadequate wheel bearings IMHO. The 84-87 bearings are also inadequate for modern performance but at 1/10 the price and 1000X the availability they are mostly tolerable.

-Also- I love your description of fast-tracking. It clearly states the goals, expectations, and accepted risks. I have a similar process with an additional constraint based on one experience in particular. I do not accept solutions that have a looming obsolescence date. That one time I found the perfect tie-rod for an Isuzu I never heard of ... didn't work out great. Insisting on parts for cars with wide acceptance and especially enthusiast support (camaros, vettes, and circle track stuff) has been well worth the extra design effort.

[neophile_17]

I just received the Mevotech SMS2278 springs today, and they appear to mostly fit OK.

This is good to know. Having another option is always better.

High scrub radius, so steering kickback over bumps, and possibly tramlining weirdness.

This is bad for feel but the way that GM minimized kickback makes it even worse. Remove the steering damper and fix the scrub and the car feels totally different.

[The Dark Side of Will]

These guys will wind whatever spring you want so that you don't have to expend effort on "catalog engineering".

https://coilsprings.com/

[eHoward]

Why not just buy them from WCF? https://westcoastfiero.com/products/1-1 ... -1984-1988

[neophile_17]

Why not just buy them from WCF? https://westcoastfiero.com/products/1-1 ... -1984-1988

Because the OP wants a higher spring rate and ride height than what WCF offers. I could also guess that price, shipping, and import taxes are a factor.

[pmbrunelle]

The 84-87 bearings are also inadequate for modern performance but at 1/10 the price and 1000X the availability they are mostly tolerable.

I like the serviceability of old-school tapered roller bearings. I have this style on the front of my daily driver 2WD truck; I love it!

Since this is not meant to be a high-performance car (built to be easy to drive, with low enough limits), I have 195/55R16 summer tires for the front. So nothing ultra-sticky. I don't think I will encounter bearing life problems. Perhaps with track driving there may be issues, but I'm not doing that just yet.

I could also guess that price, shipping, and import taxes are a factor.

Yeah... with shipping, brokerage, taxes, USD->CAD conversion, I'd probably be looking at about 400 Canukbux to get those WCF springs delivered to my doorstep. And WCF's reputation for timely delivery isn't so good...

Things can get expensive (and customs hangups) with USA vendors that are not used to selling to Canada.

However, purchases go smoothly with those who are used to selling to Canada on a regular basis. Mouser, Digi-Key, Rockauto, Summit Racing; I don't hesitate to buy from them. There are no surprises with these vendors.

The Mevotech SMS2278 springs from Rockauto were just 150 Canukbux delivered to my door.

These guys will wind whatever spring you want so that you don't have to expend effort on "catalog engineering".

https://coilsprings.com/

Thanks for the reminder!

Remove the steering damper and fix the scrub and the car feels totally different.

I tried without the steering damper many years ago (street driving), and I decided that I preferred the driving with the damper, because it helped the nose of the car dart around less with bumps, and less feeling of bumps in the steering wheel. I don't remember negative side effects with the damper.

With this iteration of the car, I can easily try with/without. It's fast and easy to try it both ways.

[neophile_17]

I like the serviceability of old-school tapered roller bearings. I have this style on the front of my daily driver 2WD truck; I love it!

I have no problem with tapered wheel bearings. The bearings on the Fiero are just too small for my use case. If you go through the exercise of looking up the suggested load for a stock bearing from a bearing manufacturer you will likely discover what I did. It was fine with 1980s tires but not with newer compounds and impulse loads from bumps etc. Empirically, I've found over a dozen years exactly how long you can run the stock wheel bearings on a road course before they fail, 30 hours. Our solution was to use a circle track knuckle with larger tapered bearings for a G-Body. Now that the bearings aren't above their rated load they'll probably last forever. If you start adding load and brake heat to stock bearings then expect to change them more often. Given your tire width and spirited street driving rather than sustained track driving I would agree that the stock bearings will offer acceptable service life. Only if you decide to make it a dedicated track car does it start to be an obnoxious maintenance concern.

I tried without the steering damper many years ago (street driving), and I decided that I preferred the driving with the damper, because it helped the nose of the car dart around less with bumps, and less feeling of bumps in the steering wheel. I don't remember negative side effects with the damper.

With this iteration of the car, I can easily try with/without. It's fast and easy to try it both ways.

I think it's worth a second look. Just a hint of toe in, enough to see a minus sign show up has always been enough to cure my complaints with darting. I will admit to being on the far side of the spectrum when it comes to wanting an 'engaged' driving experience.

[ericjon262]

idk why anyone is still fucking wasting time with a pre 88 when A number of us are driving around on a cut pre 88 spring. The problem isn't the spring, it's your suspension as a whole.

in my case, I didn't know there was a difference between any of the fiero suspensions until after I bought my car, so I'm just having fun with what I already have and trying to make the most of it because I enjoy tinkering. To me, it's no different than an engine swap. Why bother swapping the engine? it's just a crappy old fiero, can't you just buy a Camaro? a Mustang? a Vette? make it yours, have fun with it.

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eventually, I would also like to explore the idea of new front springs, this will probably happen in my next round of modifications after I get my new engine together and in the car.

[pmbrunelle]

Mevotech SMS2278 / Moog 2278 fits on the car.

The front ride height is somewhat high (1.5" higher than I'd like), but longer is better than shorter. Longer can be trimmed as required. I'll be trimming these springs.

Fiero outside.jpg (152.36 KiB) Viewed 320 times

[eHoward]

Little high but looks good