jsymonds New Reader
2/14/12 10:03 p.m.

Can you believe I actually thought about "gee, what forum would appreciate my research about Miatas and cheap solutions?" Just for a second, of course.

First off, I'd like to say that a lot of this has been made possible by the good folks at Fatcat Motorsports. I hear Shaikh is a great guy and as a fellow physicist I encourage you all to give him several of your dollars. I hope to myself, one day! However, this post is about a bunch of work I did trying to save a few bucks and, more importantly, shed some light for myself on what's going on. I am not an expert and most readers should recognize this as a huge waste of time.

That said, my time's already gone, and sharing is caring so I wanted to show off my results. More credit where credit is due, I was reading a thread on dfwmiata.com which was discussing low-budget bump stop options for the Miata. One poster suggested that a particular Honda part from the rear shocks of an Integra made a good replacement for the FCM 36mm bump stops, which seemed appropriate for my application (a '91 STS/street car).

Well, I got them in and set to work.

My testing rig was one of our vehicle scales, an arbor press, and a pair of calipers. I reckon anyone could do this with a bench vice and a bathroom scale, but this setup is a convenient way to measure up to 1500lbs in 1lb and 0.001" increments. Here's a picture:

As you'll see in the photo above, I was also testing the springs that came with an eBay NB coilover kit (adjustable perches, 450/350 springs). Turns out they were pretty good--only tested one side so far, but actual rates were 445/325, and very linear. Not all that is cheap is worthless!

Here are the results:

It was interesting to me that the bump stops behaved so much differently after the first compression cycle. Fortunately they seem to settle into their final state quickly! Also worthy of note was that these bump stops started at 1.58" free length, and after the first compression were down a bit below 1.52" (38.6mm). The FCM bump stops at 36mm are shorter still.

That's about all I've got to contribute for now. I hope someone finds it useful!




jsymonds New Reader
2/14/12 10:38 p.m.

Oh, almost forgot: Happy Valentine's day!

simplecat New Reader
2/14/12 11:21 p.m.

Thanks alot for that info, I'm really interested to see the full story on those springs. I'm planning on teaching myself how to revalve bilstiens myself, when I do I'll take a bunch of pics and post it.

modernbeat Dork
2/14/12 11:39 p.m.

And........my research finds another 1000 viewers. Thanks for taking it to the next level.

Brand names don't make you fast. Figure out what you want the car to do and what it takes. There are a lot of cheap OEM parts that work as good as anything aftermarket, but because of the economies of scale are affordable, or on the used market, really-really cheap.

jsymonds New Reader
2/15/12 2:08 a.m.

My pleasure, modernbeat--thank you! Now if only I could find the same deal you got on these bump stops...I had to cough up 11 bucks a pop, plus another 12 on shipping :/

MrJoshua SuperDork
2/15/12 5:33 a.m.

Have you figured out a cheap shock absorber option for the front?

nderwater SuperDork
2/15/12 8:34 a.m.

Great info! The rear factory stops are shot on my NB. Any idea where these guys are finding the Integra stops so cheap?

jsymonds New Reader
2/15/12 9:18 a.m.

In response to MrJoshua and nderwater: nope. I'm using Koni sports up front and limiting myself to a 550lb spring in hopes that they can handle it. I'll have to set a taller ride height accordingly, and that figure is still to be determined--I'm hoping I can get away with 12.5"/13" F/R.

Despite all my searching, I couldn't find these bump stops for cheaper than I bought them. The local dealer was selling them for $22 a piece!

jsymonds New Reader
2/15/12 9:21 a.m.

I'm curious, while we're on the topic: if you're running this kind of setup (in terms of spring rate and ride height), how much travel (at the shock) do you have before your bump stops are engaged, from rest? It looks like I'm going to have about 0.5" at 12.5" front ride height, which doesn't seem like a lot of room.

Keith SuperDork
2/15/12 11:13 a.m.

A word of warning about the springs - they might be the right rate at the moment, but run them through a few hundred or thousand cycles. That's when the metallurgy starts to show. It might be interesting to test them again after some hard use.

jsymonds New Reader
2/15/12 7:26 p.m.

Keith - so I've heard! This measurement comes after a few (several?) hundred miles of city driving and a couple autocross events over the past 8 months or so. I tend to avoid really pounding them (it's a not comfortable setup the way it was!), but they're not brand new. I will be happy to do some testing much longer down the road.

Keith SuperDork
2/15/12 9:38 p.m.

Please do, that's always interesting to know. A sagging spring is basically one that's losing its spring rate. Check the free length too, it's a quick way of taking stock of a spring's health. Coil binding a spring (not something you'd do on purpose, of course) is a good way to kill 'em fast.

jsymonds Reader
6/26/17 12:30 p.m.

Sadly, I sold that car without getting a chance to retest, but they were still feeling quite good as of July 2014 (several thousand miles and many autocross days after this mod). Not yet attempted on the replacement Miata.

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