heinzboehmer's 2002 Topaz 6MT Coupe

[heinzboehmer]

Also finally finished up the side project with the seats. Made a cushion to replace the towels that can be seen in previous posts. Decided to make it have adjustable lumbar support and a removable cover.

Started with planning out the cuts:




Since I had now used a sewing machine for more than just an hour, I figured I would be able to lay everything out directly onto the fabric. Clearly that was not the case:




For the next one, I decided to go back to the trusty CAD. Came out much neater:



For the inflatable lumbar bit, I went on eBay and got some super cheap inflatable lumbar cushions:



Removed the outer fabric layer and was left with a pretty flat inflatable bladder:



Test fitting on the fabric. Smaller than the face of the cushion, but should work well:



And now for a quick prototype made with velcro and masking tape:



Here's the range of inflation for the lumbar part:




Getting everything sewn was pretty straight forward. Starting to get kinda decent at this:




Also attached the inflatable bladder to the fabric by the top corners so it wouldn't move around too much:



Here's the structural part of the cushion done:



Next came making the outer dinamica cover. Turns out dinamica is made in ~a million colors, so it was hard to find a perfect match. I did find a vendor that stocked a color that was super close, but a yard of the stuff was $120, so I decided against it. Ended up going with another vendor that had much more reasonable prices, even though they didn't stock the exact shade of black that Cobra uses.

Meh, close enough:



Laid out the cushions onto the fabric and traced around them. Used masking tape because I was afraid of the silver marker bleeding through:




Not super obvious in the pics, but one of the cushions is taller than the other. This is because my GF said that the back cushion pushed her head forward a bit too much when set at my height, so I made a slightly shorter one for her.

Here's the finished product and how it fits over the cushion with the inflatable bit:





Since the cushions were different sizes, I used the pseudo-embroidering feature on the sewing machine to label them. This one is labeled "D" for "driver":



Some more lumbar range testing:




Looks kinda lopsided in the pics, but I think that's just because I didn't fully seat it against the seat. It's much more even in real life.

And here's the finished product:



Color match is pretty good and it definitely looks less stupid than with the towels. Still not as cool looking as how the seats come from the factory, but I can make them look normal in a few seconds, so whatever. Was also able to stuff the inflating pump thing into the substrap hole on the bottom of the seat, so no weird bits sticking out from under the bottom cushions.

Honestly this whole thing turned out pretty good. Super happy with how much more comfortable they are for street driving.

[heinzboehmer]

Assuming I understand what you are doing to regain strut travel, you will extend the shaft below mount, which will unload the spring, which will result in lower ride height, a bit more camber due to further travel in the arc and some toe out in front, concurrently resulting in more + rake and some toe in in rear, even if the shaft within the cardboard cutout stays in the same place. It will also result in more droop rather than bump, unless you shift the bottom spring collar up.

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Yeah I think the front did go down slightly (since I now just barely scrape when backing into the garage), but I'm not sure by how much. I really should have measured the before and after. Nothing crazy though, still twoish fingers between tire and fender.

This thread says the ride height is 5mm lower, but the gain in bump travel is 5.5mm, so was okay with making the trade off: https://nam3forum.com/forums/forum/m...ate-comparison

Don't have adjustable height suspension, so just trying to make it as comfortable as possible. Idea is that the part of the Turner mount that the strut shaft rests on is shorter than the stock one, so strut will have a bit more travel before bottoming out on the bump stop.

[Bry5on]

If you want the travel back, we can make you a 1/4” shim for your spring perch out of delrin or something. That would net you another 1/4” of bump travel too

[mrgizmo04]

Yeah I think the front did go down slightly (since I now just barely scrape when backing into the garage), but I'm not sure by how much. I really should have measured the before and after. Nothing crazy though, still twoish fingers between tire and fender.

This thread says the ride height is 5mm lower, but the gain in bump travel is 5.5mm, so was okay with making the trade off: https://nam3forum.com/forums/forum/m...ate-comparison

Don't have adjustable height suspension, so just trying to make it as comfortable as possible. Idea is that the part of the Turner mount that the strut shaft rests on is shorter than the stock one, so strut will have a bit more travel before bottoming out on the bump stop.

I'll need to read that thread tonight to make sure it is correct, but gaining shock shaft length is only 1 piece of the puzzle. To actually benefit from the length in shaft below the mount/plate, you need to also either lengthen the spring (install longer spring), or on existing length spring move the bottom collar up (I guess in your case would be to put a spacer/shim under the bottom of the spring). Because right now sitting lower (ride height), you are actually closer to the bump stops. And your shock shaft being longer now with new plates, just compresses the shaft into the shock body more, you did not gain bump, you gained droop. I made a few videos on shocks/springs and how to "tune" bump vs droop. Latest video on suspension (few months ago) about swapping from GC to Vorshlag plates also shows the concept.

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[heinzboehmer]

If you want the travel back, we can make you a 1/4” shim for your spring perch out of delrin or something. That would net you another 1/4” of bump travel too

Ooh interesting, might take you up on that. Shouldn't be too hard to make.

I'll need to read that thread tonight to make sure it is correct, but gaining shock shaft length is only 1 piece of the puzzle. To actually benefit from the length in shaft below the mount/plate, you need to also either lengthen the spring (install longer spring), or on existing length spring move the bottom collar up (I guess in your case would be to put a spacer/shim under the bottom of the spring). Because right now sitting lower (ride height), you are actually closer to the bump stops. And your shock shaft being longer now with new plates, just compresses the shaft into the shock body more, you did not gain bump, you gained droop. I made a few videos on shocks/springs and how to "tune" bump vs droop. Latest video on suspension (few months ago) about swapping from GC to Vorshlag plates also shows the concept.

Hmm, I think I'm missing something. I'm not sure I understand how moving the surface that the strut shaft rests on upward (towards the top of the shock tower) would result in more droop rather than bump. Ride height is lower because the thrust washer sits 5mm higher, but the strut shaft sits 10.5mm higher, so net gain of 5.5mm of strut travel.

Spring should still be compressed the same amount at rest, no? Only thing that has changed is that the strut shaft is now more extended at rest, which should mean that it has more room to travel into the shock before hitting the bump stop.

[Bry5on]

Via sendcutsend,

Delrin is available in .125, .187, .270” (3.2, 4.8, 6.9mm) and UHMW HDPE is available in .375, .500” (9.5, 12.7mm)

More options if we cut something on the waterjet here.

Get some good detailed measurements of the factory upper strut bearing and I can whip something up in CAD. Looking for OD of the bearing ID, OD of the bearing seat, length of the cylindrical section where bearing ID rests.

[heinzboehmer]

Via sendcutsend,

Delrin is available in .125, .187, .270” (3.2, 4.8, 6.9mm) and UHMW HDPE is available in .375, .500” (9.5, 12.7mm)

More options if we cut something on the waterjet here.

Get some good detailed measurements of the factory upper strut bearing and I can whip something up in CAD. Looking for OD of the bearing ID, OD of the bearing seat, length of the cylindrical section where bearing ID rests.

Awesome, I'll grab those later and text you. Although from what I remember, the section where the bearing sits on the camber plate is no longer than the bearing itself, so probably can't add a spacer there.

Think it might work if the spacer goes between the bearing and the spring perch, though. Looks like there is enough room:

[heinzboehmer]

Ended up wanting to practice my CAD skills (did very little in college, so don't have much experience at all), so designed a spacer with some bogus dimensions tonight.



Not sure I want to keep those keys on the sides and bottom. I have a feeling I'll get their geometry wrong on the first try and end up going through a couple revisions before they work. I do like that they'll make it so the spacer is unable to rotate within the spring perch, though. Plan is to make it a press fit like the factory bearing is, but still.

Anyway, I'll take the car apart later and remake the part in the correct size, then send it out to get made.

[heinzboehmer]

Hmm, looks like the ios onshape app can do lidar scanning, so might try scanning the spring perch and checking interferences with the spacer. That way I can keep the keys and (hopefully) have everything fit on the first try.

[Bry5on]

You’ll want to get rid of those form keys, they’re likely for draining water so you don’t rust those bearings.

Are you planning to 3D print them? The geometry as is would be difficult to machine, but no problem if you eliminate the keys

[heinzboehmer]

Huh, never crossed my mind that those could be there for draining water. Upper rubber spring pad has them too, so I assumed they were there to clock the two parts, but I guess that doesn't really matter when they're radially symmetrical. Water drainage makes more sense. I'll remove them from the final piece then.

Wasn't planning on 3D printing these. Realized they might be a pain to machine, but decided I'd deal with that later if I got any pushback from the manufacturer

[Tbonem3]

I look at shorter stack height as a way of gaining free lowering, not so much gaining travel, but retaining travel while being able to lower the car a bit (having my cake and eating it too so to speak).

I can see why you were reluctant to not use the turner supplied bearing/washer under the poly bushing (I don't have that issue with my setup which is why I put mine up top [also to take up some of the now unnecessarily long shaft threads]). I would suggest finding a spacer that will give you the clearance you want, but is shorter than the 7mm tall turner piece.

Gizmo's right about there being the need to raise the spring or get a taller spring, but like I said at first, I look at it as "travel is fine as-is, I just want to lower the car a little more (1/4" less say) for looks and not compromise the already limited travel. This is in regards to b12 kit or similar stock style.

[heinzboehmer]

Hmm, I'm still not sure why a longer/raised spring is strictly necessary. The Turner plates change the location of the spring seat and shaft seat independently, so even with the same effective length for the spring, there is gain in shaft travel.

The idea of swapping to camber plates got into my mind because of this post: https://nam3forum.com/forums/forum/m...742#post181742. The Koni travel up front is extremely limited, so any gain in travel is welcome. I don't need more camber (as of right now) and didn't want to go any lower. Thought that 5mm would be okay but the occasional scrape if I don't get the angle into the driveway perfect is annoying me, so I'm going to get the spacer made (which is serving the same purpose of making the effective spring length longer).

I considered swapping out my suspension for something else (which will probably end up happening in the future), but everything I looked at involved also swapping top mounts, so I decided to start with that.

[Tbonem3]

Just removing stack height (thinner plates or removing the turner spacer, for example) will retain the exact same bump travel, but shorten droop aka lower ride height

You can only gain travel by raising the car i.e., putting in a taller spring or raising the bottom perch (on adjustable coilovers). If you increase travel by putting in a taller spring, or moving that bottom perch up AND you reduce stack height, only then will you have increased travel, but maintained current ride height.

[heinzboehmer]

Okay maybe I've been using the word "travel" too broadly, I'll try to be more specific. I don't care about more total wheel travel (before coil bind), I have enough of that. Goal of this is to stay out of the bump stops by gaining more shock shaft travel.

Still unclear as to why raising the car is necessary to gain shock shaft travel. Here's a cross section of the camber plate:



If the "Nickel Coated Shock Spacer" is removed, the shock shaft extends further up, moving the bump stop away from the shock body. This should not affect ride height as the top and bottom surfaces that the spring sits against have not moved, nor has the relative position of the "Camber Plate Assembley (lol)" or "Stock Spring Perch" to the body changed.

With a spacer between the "Stock Bearing" and the "Stock Spring Perch", the dimension between the top and bottom surfaces that the spring sits against will not have changed, but the "Camber Plate Assembley" will have moved up (in relation to the "Stock Spring Perch"), resulting in a higher ride height AND more extension of the shock shaft, thus moving the bump stop away from the shock body. This should result in more bump travel, right? (but only due to the extra extension of the shock shaft)