Koni Yellow Rears - Top Hat Drill size
 

So I did one side of the Koni Yellow rears yesterday. Couldn't finish the other side as it was getting late. Anyway, one of the steps required is drilling the rear top hat. Koni says we should drill a 12mm hole. I don't have a metric set and I read somewhere that a 1/2" would work, so I just went with 1/2" without thinking of trying anything different. 1/2" is 12.7mm, so pretty close, the hole will have a larger radius by .35mm over the Koni shaft.

After reading more about the Konis this morning, I realize a few folks are going with slightly smaller bits, going with 31/64ths (12.3mm) or 15/32nds (11.9mm + some slight grinding/boring). Now I'm questioning whether the 1/2" bit was too large. It didn't really occur to me that the top hat would have any side load from the strut's shaft that would require an exact fit. I figured the hole was there just to get the thicker adjuster through.

Anyway, what I did has been done and there is no turning back on this top hat, but I can certainly buy another if I had to. Need some input on whether this should be a problem or not. Also would like to hear if anyone else has done 1/2" and what their experience has been. Car seems to drive just fine, no weird noises or anything, but want to prevent any future problems.

Thanks.

Its fine

Thanks, appreciate the input.

Just don't put the front lower perch on upside down.

Thanks but I'm not sure what you mean by the front lower perch. Did you mean the circular metal ring that holds the rubber gasket that sits right on top of the spring and under the top hat? The circular thing next to the triangular top hat in this photo?

I installed it the way it came off the OEM strut with the rubber facing downward on the spring. Wider part towards the bottom.

http://i685.photobucket.com/albums/v...ws/photo13.jpg


Funny enough, I actually put the rear spring perch in upside down. I'll have to uninstall tonight and flip them over. Explains why I had such a hard time with the spring last night.

Oops, I meant rear. Too late lol.

I used a 1/2" bit as well, without issues.

31/64" would have been slightly better, but those rubber bushings are going to deflect a hell of a lot more than the 15 thou difference between 31/64" and 1/2". You'll survive.

:bellyroll::bellyroll::bellyroll: You mean how it's illustrated in the Koni drawings? (though the front perch is part of the OEM shock-body, so I assume you meant rear)

Top hat on the left, UPPER spring perch on the rear. Rubber should be facing down towards the spring - you've installed the front UPPER perch correctly.

"Why is my car 2" higher in the back!?!??!"

It didnt handle very well thats for sure.

LOL, wish I had known about it prior to the 1st install. Oh well, all is fixed now.

Thanks for your input. I appreciate it.

When I was working on the car yesterday afternoon, looking at the shock and rear suspension, I'm kind of surprised there is would be any lateral load through the shaft. Rear control arm goes up and, not laterally. Shock goes up and down, not laterally. I'm sure there are SOME lateral movements in the entire rear suspension (when braking, accelerating, etc) but with all the pieces leading up to the shock, I'd be surprised if anything meaningful actually made it up the shaft.

For me, having the top hat facing 'up' looked so obvious as most spring perches sit that way on a shock. Didn't even question it until I saw how much higher it looked, then I realized the mistake and explained why I had so much trouble putting the spring on. Oh well, easy fix.

Haha, I was actually only able to finish one side that night. So it did look a little weird. Must admit, through a quick test drive, car seemed to drive fine. Rear was a little stiffer, probably because the spring was compressed more than usual, but overall it did drive OK.

That's actually a good point, the shock moving from side to side doesn't have any meaningful effect on the rear suspension.

Well, the point isn't whether shock movement would or would not be have an effect but rather is the strut shaft getting meaningful force that would cause lateral movement?

Given how the strut sits in structured 'assembly' consisting of bushings, perches, springs, spring pressure, top hats, nuts, mounts, etc and the primary movement going up/down the control arm and strut, I'd just have to wonder how much lateral force actually leads up to the strut's shaft.

And if so, what level of movement generates a meaningful side effect? Given they're two separate pieces, even from the factory there is always going to be some level of 'play' between a top hat and strut.

Anyway, after seeing the responses here and doing a bit more research the 1/2" hole seems to be fine. Car was put together last night and went out for a test drive, felt good, no weird noises!

Off topic from the thread, but since I messed up...

Wrong way -
https://fbcdn-sphotos-h-a.akamaihd.n...40651420_n.jpg

Right way -
https://fbcdn-sphotos-c-a.akamaihd.n...72730728_n.jpg

I'm bumping this one up from the dead...do you mind re-uploading these pics? I'm doing the install this week and want to make sure I assemble the rears properly.

Thanks!

Well in case anyone ends up needing this for future reference...here is a picture of the correct way to orient the rear spring perch:

http://i.imgur.com/snpMTRWh.jpg

And I ordered a 31/64th drill bit from Amazon to drill out the rear top hats, and it worked perfectly.

If you're ordering a drill, why not just order the 12mm drill?

Find me a 12mm drill bit that can drill metal and I'd buy it. Couldn't find one easily when I was searching.

I actually get a lot of my machine tool consumables from Amazon because of the free shipping. It was a bit easier when they had Amazon Supply, but you can still find stuff on the normal site.
High Speed Steel should be all you need. I prefer screw machine length drills because they're stiffer than jobber length. I've had good luck with the brand YG-1.
Here's the screw machine length version: http://amzn.com/B009NND9JO
If 102 mm isn't long enough, here's the jobber length version: https://amzn.com/B009NNO2PY

Wow you guys are over thinking this...a Hf drill bit will work just fine for the task....hell, you can return it when you're done haha

I'm of the mind that you use the right tool for the job. If Koni specifies a 12 mm drill, there's a reason.
It helps that my shop is entirely metric.