So now that I'm taking apart my front suspension to probably raise the rear LCA pivot (and maybe drop the front pivot in the crossmember), while leaving the UCA alone, I was thinking that the knuckle will rotate in the pitch axis with suspension travel.
As the suspension is compressed, mechanical trail would also increase. Should I be concerned that this change in mechanical trail might feel weird? Perhaps I need to quantify this change.
How much mechanical trail is there in a stock Fiero? If the spindle axis intersects the kingpin axis, then I can work this out from the caster angle measurement I got from my Fiero's last alignment.
What do y'all think?
[This message has been edited by pmbrunelle (edited 01-10-2023).]
I was rebuilding the front suspension on my '85 SE V6....Grabbed a front crossmember/suspension out of the junkyard, shortened the bump-stops, rebuilt it....A day or two to swap it in!!!
Yeah, most of my plans fail slightly...But this was really bad- The LAST bolt holding the crossmember to the frame snapped off (Arrrrggggggggg)
Tried to drill it out...then use a tap to clear it- did not work...
Finally installed a carriage bolt + plate inside the frame (Grade 8) and then was able to finish the project (After three weeks- including removing the front facia so I could fish the bolt/plate into the frame rail)
Worked like a charm, but I used up all of my french and had to start using russian....
So now that I'm taking apart my front suspension to probably raise the rear LCA pivot (and maybe drop the front pivot in the crossmember), while leaving the UCA alone, I was thinking that the knuckle will rotate in the pitch axis with suspension travel.
As the suspension is compressed, mechanical trail would also increase. Should I be concerned that this change in mechanical trail might feel weird? Perhaps I need to quantify this change.
How much mechanical trail is there in a stock Fiero? If the spindle axis intersects the kingpin axis, then I can work this out from the caster angle measurement I got from my Fiero's last alignment.
What do y'all think?
I don't think they are captured nuts, I think they are threaded plates in the frame. I honestly don't remember how I dealt with mine, but I think I was able to drill it out and extract the broken remnants.
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IIRC, there's not a ton of room to go up with the rear LCA mount, I'm curious about how you plan to execute this. I'm not well versed enough with suspension dynamics to comment on how your modifications specifically would feel, I can however, say that Will's anti dive setup did completely eliminate brake dive, but I also no longer have any caster, so the car doesn't have much feedback at all. I'm hoping to fix this with a custom UCA.
------------------ "I am not what you so glibly call to be a civilized man. I have broken with society for reasons which I alone am able to appreciate. I am therefore not subject to it's stupid laws, and I ask you to never allude to them in my presence again."
I invited Lou Dias to trash me in my own thread, he refused. sorry. if he trashes your thread going after me. I tried.
Originally posted by ericjon262: IIRC, there's not a ton of room to go up with the rear LCA mount, I'm curious about how you plan to execute this.
I'm not really sure yet. First I'm going to just undo everything, then put back the suspension together without the spring to measure how the knuckle moves.
Then, I'll decide what I want to do.
I might actually just want to take away the pro-dive, and not necessarily go for anti-dive. To be determined.
Highly recommend welding a nut to any remaining thread sticking out. I do a lot of prep to make sure I get a good weld, I like to put a big chamfer on the front face of the nut so I can weld as deep as possible. The extreme heat will break it free. Getting a wrench on it soon after welding is important, I make sure to have my wrench handy. I have more success when the nut is slightly oversized and fill the gap with weld material to make sure I can weld as deep as possible.
If the bolt is broken flush, welding to a washer and then welding a nut to it can also work, but not nearly as well.
I have never had an issue with drilling the bolt out after the fact in the event the welding does not work, the welded portion usually breaks off leaving the softer metal exposed.
You have probably done this before but on the off chance you haven't I figured I would share. I have done this a lot because I am addicted to rusty garbage.
Did you leave the steering rack at the in the stock position on the crossmember, or did you move it down a bit to follow the front LCA pivot?
Sorry, I've been busy racing a '95 Civic for the last few years!
The Fiero is still waiting for me to finsh up a few things and go racing again. I haven't sorted the front bumpsteer yet, the rear bumpsteer was more important and that's just about done. Nothing revolutionary there, just my take on several other approaches.
I have a WS6 Trans Am power rack on my car and that caused some of the bumpsteer that I have. It's in the same plane as the stock rack, using one of the mounts. I'm changing out the front LCAs to a set of '84s with Lemforder spherical bushings, and once those are in I'm going to use a spacer style bumpsteer kit to minimize the bumpsteer.
For me, the main issue caused by the bumpsteer was due to dive under braking, and adding anti-dive took care of most of that. The steering feels very natural and transparent, and everyone who has raced the car loves the steering so I'd have to say there is very little downside to the "mender mod".
The Trans Am rack is a very significant part of that.
[This message has been edited by mender (edited 01-16-2023).]
Originally posted by mender: I have a WS6 Trans Am power rack on my car and that caused some of the bumpsteer that I have. It's in the same plane as the stock rack, using one of the mounts.
Are you implying that front bumpsteer on your car is caused by: 1. When using the WS6 Trans Am rack, the tie-rods aren't the same length as Fiero tie-rod ends. 2. You moved the LCA pivots, but you kept the steering rack in the same plane as stock Fiero. 3. Some combination of the above two items?
It's also good to hear the general feedback.
90s Civics are nice cars, easy to work on, but they are becoming rare now!
[This message has been edited by pmbrunelle (edited 01-16-2023).]
Originally posted by ericjon262: IIRC, there's not a ton of room to go up with the rear LCA mount, I'm curious about how you plan to execute this.
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Originally posted by pmbrunelle: I'm not really sure yet. First I'm going to just undo everything, then put back the suspension together without the spring to measure how the knuckle moves.
Then, I'll decide what I want to do.
I might actually just want to take away the pro-dive, and not necessarily go for anti-dive. To be determined.
I took some measurements last weekend.
Here I hot-glued a marker to the spindle, and I traced the suspension movement on a piece of paper:
The pro-dive characteristic is confirmed, as the trace tilts towards the rear of the car with suspension compression.
I also used an angle gauge (it uses gravity) to measure the caster change with suspension compression:
Relative to full droop, the caster angle increases by 2.65° when the bumpstop is squished. This implies that the knuckle is rotating about some instant center behind the front suspension. So there is some caster change from the factory...
With the mender mod, I think that the side-view instant center of the knuckle will be closer to the front suspension, so there will be more caster change. Using the UCA washers, I should increase the static caster adjustment, so that the caster change has less of an effect percentage-wise.
I think that if I raise the rear LCA pivot by 1/4" (indeed, it cannot go up by much), and lower the front LCA pivot by 1/2", then I can take away the pro-dive. I don't think I want to go any further than that. I don't want to create any negative side-effects, plus, I have stiffer springs than stock (ready to be installed) to help control suspension movement.
Because I won't be moving the pivots very much, I think I'll have to weld the existing bolt holes shut before I can drill new holes.
There is also the idea that the suspension of a car subjected to some acceleration should react the same way, whether it is due to braking, acceleration, going up/down hills, and that consistency in this feeling feels natural. Greg Locock on eng-tips doesn't seem to be a huge fan of anti-dive/anti-squat; he cites the reduction in linearity for the driver.
I have been debating whether a coilover setup up front is a benefit or not. If you could get a standard 2.5" ID spring to work up front without being installed on a shock, then it might be better to just make new mounts for an aftermarket shock to bolt into the stock location.
Better as in less limiting with shock choice, and easier to swap/adjust shocks.
Could fab an easy ride height adjustment with a big bolt to adjust height and some slotted holes to allow the upper spring mount to move up and down with some bolts to secure it once height is set.
Do you think an appropriately sized seat at the bottom and a smaller OD cone up top (or another outer seat) could locate a spring this small in a similar fashion to stock? https://www.summitracing.com/parts/sum-72-07-350
7" may be kind of short but there are many different lengths offered.
I know this is an old thread that someone else already revived... but if we're being honest, a well-sorted 84-87 suspension with the WS6 springs and shocks... is it really going to be that much worse than a stock (good condition) 88 suspension? I've never driven an 88... and at mid-40s, I'm definitely not going to drive my 87 like I did when I was 19. But there were many times where I was doing 100+ miles an hour in a curve, with all four wheels squealing as I edged out someone else, and it felt relatively stable. Granted... I was a total idiot, and I should probably be dead, but would the 88 in that situation really be all that much better?
I have been debating whether a coilover setup up front is a benefit or not. If you could get a standard 2.5" ID spring to work up front without being installed on a shock, then it might be better to just make new mounts for an aftermarket shock to bolt into the stock location.
Better as in less limiting with shock choice, and easier to swap/adjust shocks.
Could fab an easy ride height adjustment with a big bolt to adjust height and some slotted holes to allow the upper spring mount to move up and down with some bolts to secure it once height is set.
Do you think an appropriately sized seat at the bottom and a smaller OD cone up top (or another outer seat) could locate a spring this small in a similar fashion to stock? https://www.summitracing.com/parts/sum-72-07-350
7" may be kind of short but there are many different lengths offered.
I prefer divorced shocks+springs for ease of shock replacement, and because I prefer the spring+shock load to be spread out, versus concentrated in one spot. Everyone has their own tastes though. I also don't like too much adjustability, because then it looks like a prototype and not a production car (final solution selected, and implemented with fixed parts). Personally, the stiffer springs I have are meant to drop into the stock spring seats, and I will cut the spring to fine-tune ride height.
I suppose that a smaller diameter spring could work like stock (directly acting on the LCA), but I would have a concern about the spring buckling because the angled LCA is pushing the spring outwards? To be studied I guess.
At full droop, the LCA has a lot of angle, but there is low spring force. As the suspension compresses, the LCA is straighter compared to the upper seat, but the spring force is higher. For different positions in the suspension travel, you can solve the beam differential equation using the LCA angle as one of the boundary conditions.
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Originally posted by 82-T/A [At Work]: I know this is an old thread that someone else already revived... but if we're being honest, a well-sorted 84-87 suspension with the WS6 springs and shocks... is it really going to be that much worse than a stock (good condition) 88 suspension?
The second half of this thread is about trying to sort out the 84-87 suspension, so apparently some people think it's worth trying to modify the early suspension rather than throw out the entire car and buying an 88.
I know this is an old thread that someone else already revived... but if we're being honest, a well-sorted 84-87 suspension with the WS6 springs and shocks... is it really going to be that much worse than a stock (good condition) 88 suspension? I've never driven an 88... and at mid-40s, I'm definitely not going to drive my 87 like I did when I was 19. But there were many times where I was doing 100+ miles an hour in a curve, with all four wheels squealing as I edged out someone else, and it felt relatively stable. Granted... I was a total idiot, and I should probably be dead, but would the 88 in that situation really be all that much better?
It was one of the better handling cars in the day, but keep in mind the discussion is about a 35 year old car, so if somebody wants to get the 87 to work better than the 88, its his time and money, but I wonder why the goal was set so low, IMO, the suspension, like that "highly desirable" Getrag is more easily improved by buying just about any car made in the last 20 years, certainly the last 10 (I've owned my 88 33 years and have been debating selling it for about 23 years)
