Koni sleeve kit question - Miata (NB)

So I ordered up some yellows for the Miata, going to do my own spring rates and need to get the sleeve kit.

Question is, what tops should I use? 25mm, 40mm, or, as I saw in one post on Miata.net, tops aren't needed?

Sorry if it's an idiot question, I haven't looked at the mounting config on the car, and haven't had the suspension apart since last year (and I'm old. You know, memory failure and all that...).

Are you referring to the new bumpstop support? It should come with the GC kit. IIRC the stock part won't fit inside 2.5" springs.

Be careful of internet statements about what's "needed" on suspension. There's no qualifying exam to post to the internet. You would not believe some of the stuff that's limped into our shop with "but the guys on (internet forum) suggested it" on board.

No, sorry, the top perch size (or is that the bump stop support?) - one has a little more "hat" size. I would think bigger is stronger is better, but without looking underneath the car, considering spring length and adjustability factors, etc...

I also need to start looking at spring lengths, etc... I've read (somewhere) that 6" fronts and 7" rears would be used, but is that with or without helper springs? With that, is there a down side to running a longer spring to eliminate the helper (I would think not...)?

I need to get a little more serious about it now that the yellows are on their way.

I don't know what you mean by "top perch size". That's the Miata part with a spring locater inside. 25/40mm aren't numbers that make sense in that application.

6/7 is the usual spring length, assuming you're not doing anything odd with spring rates or ride heights. Very few people use helpers with GC setups.

Longer springs do not necessarily mean you eliminate a helper. It just means your spring perch is lower (given no change in ride height), which may run in to problems with clearance to the upper control arm in the front or the rear halfshaft. They do mean there's less possibility of coil bind.

If I roll in to the shop and say "but the guys on (internet forum) suggested it" I'll understand if you beat me soundly about the head and shoulders and send me away...

This is what I refer to (and please pardon my ignorance. Which begs a whole other set of questions, but I digress...):

From this page... Koni Threaded Spring Perch Sleeves and Parts

Spring rate wise, the intent is to run 400ish/300ish (so maybe 425/300, 400/275, etc...). I don't think that's too stiff for a mostly street and sometime autocross car, but if it is, I can dial it back a little more to what appears to be the standard 375/250 combo.

I'm a bit of a slave to appearance, so my thought is rates a little higher will be better for a ~12/12.5 f/r ride height.

I know I'll probably be hitting bumpstops even at that, so everything is a bit of a compromise between appearance/performance/kidney failure. And/but I am aware that softer rates require higher rides heights, etc.

BUy better shocks and up the spring rates.

Ah, that thing looks like the upper spring perch on a coilover that bolts in via eyebolts. ie, not a Miata. You'll use the Miata upper mounts with the spring locator instead.

What you're picturing:

Your upper mounts will be more like this.

The easiest thing to do is just to buy a GC kit for a Miata with Konis. You'll get everything you need instead of trying to figure out the bits and pieces. You can specify custom rates if desired. FM carries them as do others.

You glue the spring locator to the top mount with gorilla glue. That is what the good people at Fat Cat tell you to do.

Have you seen this sleeving bilstein shocks thread?

Ah, got it. Thanks gentlemen.