Failure

As I recall, my MSM front shock has almost exactly 4" of stroke, which comes out to 5.56" of travel at the wheel. Assuming all the stock shocks have the same amount of stroke, you'll want whatever length top hat puts the hub center about 16.6" from the fender lip. Can anyone measure the distance between the shock mounts at that height, as if a flat plate were used for the top mount? That would make the matter of top hat depth as simple as comparing shock body length to the reference length.

OptionXIII

All they do is raise the shock mounting point. If the car is hitting the bumpstops on the shock but isn't being limited by any other things touching, there is more compression travel to be had. I am trying to get as much travel as possible while still maintaining a good balance between compression and rebound travel.

Making extended top hats out of stock NB hats would give the same effects without worrying about how the shock is mounted. Based on the picture below (NB on left, NA on right), it seems that the NB mounts position the shock roughly where a flat plate would with no bushings installed. I think that would make comparisons to ISC hats much easier, as the amount of extension with no bushings on ISC hats would be directly comparable. My plan to extend them was to use a holesaw to cut out the center part of the top mount, then weld in a length of pipe, then the center part welded back on top of that.



My Vehicle Dynamics professor recommended a 60/40 split of compression/extension travel, so I might go a bit beyond that to make room for more low. Especially since I don't have helper springs right now.

Seefo

iTrader: (5)

I understand how top hats work, I just don't understand why you want to go through that trouble instead of the ISC top hats. Your first post implied that something was wrong with the ISC top hats...

OptionXIII

Because either way I'll be fabricating something, since I refuse to pay that kind of money for three pieces of steel and other-than-metric bolts. The ISC bushings have the rods directly resting on the steel hat with a bushing on top, though some have cut the bushing in two and put half on top and half on bottom. The stock bushings look more likely to articulate with a change of angle IMO.

I would guess that the 4" of travel would be close enough to go on, though I'll measure when I decide to take the rear end apart. I'm just in the planning phase right now, working on my DD in the apartment parking lot is sketchy at best and I'm not looking for extra downtime.

maxc14

I made my own extended top hats. I used stock nb hats and chucked them on a rotary table and cut a 2 inch hole. I then welded on 1.5 tube. For the top I used the piece I cut and welded it on. If I would make it again I would add spherical bushings. I also made and casted my own urethane top hat bushings because I have make various urethane and silicon cast parts.




Here is the setup I had.

95 miata with NB bilstein sports/NB top hats extended to 1.5 inch/Front 400lbs 7inch/Rear 300lbs 7inch/FCM 36mm bumpstops.

I used qa1 springs. I cut new circlip grooves 3inchs down on all the shocks. I put them on the car and set the ride height very low less than 12inch. It worked but was too low and I set the ride height to 12.5 Front/12.75 Rear. The front springs coil binded and pop the circlips off. I switched to ebiach 8inch 400lbs in the front and went back to stock NB top hats in the front.

It can be frustrating to figure out what setup works and what to buy. For me I like my eBay bilstein setup but if I did it again I would have just put the money toward xidas.

wannafbody

iTrader: (1)

ya know, the stock NA tophats rest on the shock shaft and don't even use a rubber bushing on the top side. The ISC top hats are fine, even for street driving. Even if you add a rubber bushing on the underside, you still need it resting on a metal washer.

kenzo42

iTrader: (6)

delete.

curly

iTrader: (25)

I want these. Beautifully made.

WMP

iTrader: (1)

Finally got around to installing my Allstar sleeves on my NB the other night. Don't have any good pics, but my ride height went from 12.5F/13.5R to about 11.5F/12R. HERRA FRUSH YO!

I had the car as low as it would go on the ebay sleeves before with new Bilstein NB Sports, 36mm bump stops, and oem NB tophats. 6" 550lb springs in the front and 350lb 7" in the rear.

I did trim the bump stops down to about 30mm or so, but I would say the car is still resting on the bump stops currently (my head/gut are too big to get a good look at them). I'm going to take it to my alignment guy in a couple days to get it corner balanced. Probably end up raising it about a half inch all around.

Still tossing around the idea of ISC tophats in the front, but right now I need to focus on brakes...

TL;DR - Allstar sleeves are the bee's knees.

bahurd

iTrader: (8)

Why 6" fronts?

If you're going to be that low you'll end up with extended top hats to get the shock travel back.

I'd raise them up 1/2" especially before doing the alignment.

WMP

iTrader: (1)

I got a good deal on the 6" springs used from a local guy. In hindsight 7" would have worked fine. If I go to a heavier spring one day I'll get 7".

It's definitely going to get raised up some. I'm not even sure if my track wheels and tires would fit at this height, but I'm just going to let my guy do whatever he thinks is best. He's pretty good at making miatas go around race tracks quickly.

kahvorka

I want to thank everyone for all the information on this thread and share my Bilstein coilover experiences, as well as ask a couple of questions I couldn't find solid answers to.

Last year I got a set of revalved R-package NA Bilsteins, revalve was done according to Fast Mike's numbers. However, I cannnot for the life of me find any solid data on it. The guy who I got the shocks from said he found that they have ~250% more compression and ~30% less damping. I got sleeve/spring combo Failure linked on post no. 151 along with $6/corner honda bumpstops and a set of NB tophats (I installed shocks with stock NA tophats first, resulting in stock ride height and other bad things). With NB top hats my car sits at ~12.75" front and ~13.0" back. Here's a list of parts going top to bottom of the shock if anyone wants a setup that works reasonably well and doesn't explode driving through massive potholes in Chicago.

-Stock NA nut
-body washer
-10mm of honda bumpstop
-NB tophat
~10 of honda bumpstop (I know I should have more rubber there, but I don't want to buy extended nuts)
two body washers

Now, if I reverse the sleeves to get half an inch more thread on the bottom, will it translate to half inch off the ride height? I want to get as close as possible to 949 racing dual duty alignment numbers.

I'm currently running all 4 350lb springs that came with the sleeve kit, but will be buying 500,550 or even 600lb springs, will the shocks handle that? Otherwise, should I buy softer springs for the back and keep 350lb in front? I'm only doing autox, and the car might be retired from it's DD duty soon, so ride quality isn't that big of a concern.

Lastly, with ~550/350lb combo, how big of a front swaybar should I buy? Can I get away with an NB bar or spend more money on an RB bar? I will experiment with disconnecting the rear bar for autox.

maxc14

Thank you

WMP

iTrader: (1)

See above...

OptionXIII

You could always get new grooves cut into your shock, but from this post you can most of another inch from Allstar sleeves.

Max, those are awesome and exactly what I'm looking to do. Wannafbody, I know NA hats have the shocks resting directly on the top hatl, but there's still rubber between the shock mount and the rest of the chassis. I'm looking to keep OEM function and NVH if at all possible.

maxc14

If you make them I would use the nb mounts. I can't remember what bushings I used but if the stock don't work there is plenty of other aftermarket ones you can use.

Failure

I just did some measuring, and in the rear my upper control arm contacts the shock tower at 9.5" fender lip to hub center, at which point the distance between shock mounts is 10.5". My MSM rear shock is 11.25" long fully compressed. Therefore I'd want a rear top hat 0.75" deep, plus maybe 0.25" to account for a compressed bump stop. I'd say a top hat deeper than 1" is a serious mistake, at least for my NA6. And if I recall correctly, this is also the same suspension geometry as the NA8.

I also really feel like I should get a metric tape measure. Eighths are too much math for me.

maxc14

I used nb bilstein and 1.5 top hat extension was too much I switched back to normal mounts. I would go with 1 inch also. 1.5 inch extension required me to lower the car too much if I raised it I got coil bind.

Seefo

iTrader: (5)

No clue who fast mike is, but as long as he didn't royally screw the pooch on the valving, OTS Bilsteins can take 500lb springs.

you can run 600 lb springs, I would match that with 400 in the rear, especially if you don't run a rear sway bar. you can use a suspension calculator to figure out the FRC you want with the sway bars you choose. FCM has one on their website. I have one I use on my google docs.

Honestly, if you are considering 600 lb springs and you plan to not DD the car AND it has revalved bilsteins, you might as well run the 949 suspension setup:

700/400 or 800/500 springs
RB Front sway bar
MSM rear sway bar

Failure

It would, but make sure you're not going below zero preload. If the spring is loose when you jack the car all the way up, you need helper springs. Here's the cheapest source I've found: http://www.filthymotorsports.com/PAC_RacingSprings_p/pac-tender.htm

As far as spring rates, I've been planning to go with 500/350 with a Racing Beat tubular FSB and stock RSB. Play around with the Fatcat spreadsheet a bit, it's fun.