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Old 01-01-2015, 11:00 PM   #1
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Default 1.5" DIY ISC rear top hat interference

I made a set of DIY ISC top hats with 1" offset in the front and 1.5" offset in the rear. I have been running NB top hats on NA HD Bilstein shocks and 36 mm fat cat bump stop and upper bushings. I have been running around 12.75" ride height and it feels like I am bouncing off the bump stops most of the time so I wanted to make my own top hats and see if I can improve the ride quality a little. I finally had some time this week to play with my TIG and plasma cutter!

I just mocked the top hats on the car and found that with the 1.5" hat in the rear I would barely begin compressing the bumpstop before the upper a-arm would make contact with the frame (see attached pic). I thought 1.5" was the standard ISC top hat to use in the rear? I tried the 1" top hat I was goin to use in the front on the rear and it looked much better.

The 1" top hat seemed a little tight in the front, but I didn't have any metal on metal issues. With no spring installed I could jack the wheel up high enough to compress the bump stop with the weight of the car and had about 3/4" before the tire would rub. I am considering going back to the NB hat in the front, unless it will be worth it to make a 3/4" hat for the fronts.

For the guys that run ISC hats, did you have interference issues with Bilsteins?



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1.5" DIY ISC rear top hat interference-2015-01-01-22.05.55_resized.jpg   1.5" DIY ISC rear top hat interference-2015-01-01-22.06.34_resized.jpg  

Last edited by Rallas; 01-02-2015 at 11:32 AM.
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Old 01-02-2015, 07:53 AM   #2
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what was the specific problem you were trying to solve with those tophats?
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Old 01-02-2015, 08:22 AM   #3
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Of course you're going to have to re-do your bump stop length when making extended top hats.

Whats this about 1" extended in the front of the car but then putting a 1" spacer in it, that does nothing but lower your droop travel.
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Old 01-02-2015, 11:11 AM   #4
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Quote:
Originally Posted by Leafy View Post
Of course you're going to have to re-do your bump stop length when making extended top hats.

Whats this about 1" extended in the front of the car but then putting a 1" spacer in it, that does nothing but lower your droop travel.
Do not knock it until you try it, lowered NA's do ryde on the rear bump stops all the time and makes them a handfull on bumpy autocross tracks when the spring rate goes form 350# to whatever the bump stop is when you hit a bump.
I have been using taller top hats for years on my cars and everyone that has driven my car wants a set for theirs and are happy with the results.
Droop is not really affected when you simply move your travel toards the compression side vs the shortened travel of a lowered car, the right set of helper springs will keep the inside wheel on the ground.
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Old 01-02-2015, 11:14 AM   #5
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While that might be the case, relte seemed to make it sound like he was going to make 1" taller top hats and then put a 1" spacer between the top hat and the bump stop.
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Old 01-02-2015, 11:19 AM   #6
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if you weren't using shitty shocks/springs/ride heights in the first place you wouldn't need extended tophats.
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Old 01-02-2015, 11:26 AM   #7
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Good point. Nobody ever made extended top hats for Konis.
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Old 01-02-2015, 11:28 AM   #8
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Koni shocks are too short to need tophat extenders. you add them you'll just coilbind, put the tire through the fender, or hit the a-arm on the frame.

if you're being factious, then those people don't understand how suspension works.
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Old 01-02-2015, 11:30 AM   #9
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err... The sports have basically the same size body as stock...
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Old 01-02-2015, 11:34 AM   #10
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Quote:
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err... The sports have basically the same size body as stock...
Stock NA shocks are 10" in the rear. the Koni sports are 9.25".
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Old 01-02-2015, 11:41 AM   #11
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Didn't FM make hats for Konis?
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Old 01-02-2015, 11:43 AM   #12
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No 1" spacer used sorry, should have been 1" top hat. I edited the post.

I started thinking that I could use a longer NB front bump stop or some VW stops I have laying around. I thought the whole idea is to keep the shock off the bumpstop, so why in the hell do you need to extend the top hat just to increase bump stop length?

Quote:
Originally Posted by Leafy View Post
Of course you're going to have to re-do your bump stop length when making extended top hats.

Whats this about 1" extended in the front of the car but then putting a 1" spacer in it, that does nothing but lower your droop travel.
I fully understand that these hats only trade droop travel for compression travel, but with the car being lowered I have more droop travel than I will ever need. I took some measurements of the rear at fully drooped and compressed to the point that I compressed the bump stop just enough to lift the car off the stands (no spring installed). I have to go find my measurements and will post them later.
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Old 01-02-2015, 12:41 PM   #13
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Quote:
Originally Posted by concealer404 View Post
Didn't FM make hats for Konis?
I dont believe they were specifically made for Konis. They made a verison that you could use with Konis that had a larger bearing to accept the thicker shaft.
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Old 01-02-2015, 12:52 PM   #14
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Quote:
Originally Posted by relte View Post
I started thinking that I could use a longer NB front bump stop or some VW stops I have laying around. I thought the whole idea is to keep the shock off the bumpstop, so why in the hell do you need to extend the top hat just to increase bump stop length?
the shock needs to stop on the bumpstop and nothing else.

if you extend it too far, and things like the control arm hit, then you need to readjust. Either with long stops, or you can just put spacers behind the bumpstop, so it's still short, but the shock stops travel sooner--before that control arm hits the frame or the tire would hit a fender.

the 1" on the rear is probably all you need, im sure you're fine without any in the front.
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Old 01-02-2015, 12:54 PM   #15
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Quote:
Originally Posted by Braineack View Post
if you weren't using shitty shocks/springs/ride heights in the first place you wouldn't need extended tophats.
What do you think the shocks on the photo are? Konis are not top shelf but are not **** either and eiback springs are good springs, 12" height from the center of the wheel to the top of the fender.
Is that the **** you are talking about??
Conceler, what do you think of Brian's car handles? Come over to grissom next summer and drive the car before you are an *** about it
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Old 01-02-2015, 01:00 PM   #16
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Quote:
Originally Posted by HHammerly View Post
What do you think the shocks on the photo are? Konis are not top shelf but are not **** either and eiback springs are good springs, 12" height from the center of the wheel to the top of the fender.
Is that the **** you are talking about??
Conceler, what do you think of Brian's car handles? Come over to grissom next summer and drive the car before you are an *** about it

Whoa there, i'm not talking **** about extended top hats. I have custom NB units as well. 1" front, 1.5" rear.

I think his car handles pretty well. I was pleasantly surprised after all the ****-talking i hear about Konis on the various Miata sites. I hadn't actually been in a Koni car before. I've been in a few Xidas cars, a few Vmaxx Track pack cars, Ohlins, AFCO, Ricelands, and a couple homebrew Bilstein cars.

I'd be happy with his suspension setup for my uses. I'll be ecstatic if my Bilstein setup comes close to what his car does. (Been lazy/don't have the space right now to do the install.)
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Old 01-02-2015, 01:01 PM   #17
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Konis are seriously the one of the worst shocks for the miata. they were designed around stock springs, and have compression and rebound characteristics that make them less than desirable--unless the goal is poor performance and horrible ride quality.
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Old 01-02-2015, 01:09 PM   #18
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Quote:
Originally Posted by concealer404 View Post
Whoa there, i'm not talking **** about extended top hats. I have custom NB units as well. 1" front, 1.5" rear.

I think his car handles pretty well. I was pleasantly surprised after all the ****-talking i hear about Konis on the various Miata sites. I hadn't actually been in a Koni car before. I've been in a few Xidas cars, a few Vmaxx Track pack cars, Ohlins, AFCO, Ricelands, and a couple homebrew Bilstein cars.

I'd be happy with his suspension setup for my uses. I'll be ecstatic if my Bilstein setup comes close to what his car does. (Been lazy/don't have the space right now to do the install.)
You should come and try my NB this weekend
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Old 01-02-2015, 01:12 PM   #19
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You should come and try my NB this weekend

I'd love to, but we're down to one vehicle right now, wife's jeep puked a water pump on Wednesday and it won't be fixed until Monday, so she's driving mine.

And my Miata has that piece of crap Begi Racer "Reroute" on it so it won't come up to operating temp if it's less than 50 degrees out.
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Old 01-02-2015, 01:18 PM   #20
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Quote:
Originally Posted by Braineack View Post
Konis are seriously the one of the worst shocks for the miata. they were designed around stock springs, and have compression and rebound characteristics that make them less than desirable--unless the goal is poor performance and horrible ride quality.
That is why my set was not the race shocks (that are to short and kill your droop) but a standard sport re-valved for the spring rates used.
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