guys drilling out the front upper urethane to 7/8" hows that been working out? should the drill bit be slightly under size to ensure tight fit? I'm thinking of doing it to some front uppers.

 

Pretty sure Sean drill them out on the lathe with a 7/8s bit. But wait for him to respond.

 

949 site says the ES bushings are 88A except for the front uppers which they say are 95A. Thinking I've seen that somewhere else too but don't remember where off hand. I've used Prothane and ES both and don't really recall any real difference but didn't do them both at the same time.

https://949racing.com/energy-suspens...ngs-miata.aspx

I'm also getting ready to drill out my front uppers for the bushings so am in for any tips. Think freezing them was mentioned along with using a lathe for higher speed.

 

I have yet to do any Miata bushings, but I have some universal ES bushings ive experimented with. New sharp bit, highest spindle speed you have, 1200rpm has worked ok for me. Use a 7/8" bit, since the poly deflects so much it will drill out slightly undersized anyway. And if it didn't, they crush a little when you install them since they are 0.010" oversized, so the ID will shrink anyway.

I havnt tried it yet, but I think freezing them is a good idea. You almost have to use a lathe, as there is no other good way to hold it without it distorting, like in a vise; and you need to hold it true to the drill axis.

 

You could use a drill press if you wanted to I bet.

 

You gonna hold it in a lathe chuck in a drill press? Either that or you need someone to mill you some soft jaws, maybe some steel pipe nipples...

 

I would actually suggest doing it in the control arm. Or buying some pipe. Press it in. Freeze it. Drill it.

 

Making sleeves out of pipe makes sense to me.

 

This is pure speculation and by no means a tested idea. Just how I thought about doing it.

 

Whatever I used to pull my rubbers out was a super snug fit on the rubber bushings, I think I already posted the picture a page or so ago.

I also don't think freezing it in a home fridge is going to do much of anything. You need nitrogen or dry ice at the least.

 

Someone do it for science.

 

I will when i have science time

 

More info on sleeve diameter questions. after loking at cast in part numbers on my V8r bushings comparing the font and number scheme I think they are Prothane not ES. question is does anybody know the sleeve diameters for the Prothane miata Kit? if they are like the V8r they are all 7/8"

 

Prothane kit
RUCA-O: 0.750"
FUCA: 0.813"
Everything else: 0.875"

ES is the same

 

dam. .813 how the hell did an engineer arrive at that size? Hm how much can be forced in there I wonder. Urathane is not really soft though.

off the shelf Whiteline FUCA 7/8" $63 for just the front uppers from summit. not exactly a cheap addition.

Whiteline W52208A Control arm - upper inner bushing

 

No idea who the hell came up with that, Id guess it wasn't an Enginear (lol). More than likely, it was a bushing already in existance from another platform that they reused so they didn't have to make new molds... or something.

To complicate the issue, that location happens to have the largest pivot bolt in the car at 15mm, so its also the smallest wall thickness sleeve. For the poly retrofit guys, using a 0.750" sleeve, its running on the ragged edge of wall thickness at about 0.080". Must use high tensile material there. 4130 drawn tubing has worked great so far. No need to tighten that bolt past 40lb ft.

 

I'm running Delrin in my FUCAs now (mega FSM torque specs have nothing on the nice ~9/64" thick cr-mo sleeve), so I will try enlarging my unused FUCA ES bushings this weekend with:
- freezer
- 7/8" drill bits
- size G hand reamer

I think the drill bits will work fine. I have spare SAE 863 bushings, so I'll just enlarge the hole enough to get a nice tight fit on the bronze.

 

just a little update. i installed the rest of my bronze kit and i now bottom out HARD. time to increase the springs another 100 lbs. 900/600 or just cut the bs and do 1000/700?

 

 

Part of the reason why I just made new bushings out of aluminum for that spot.