Brake bleeder screw nipples size question

[Vintageant]

Member since September 2019, but first post. Took me a while to figure out how!

My '73 Spider has 5 mm brake bleeder nipples on the front and 7 mm on the rear. Is that normal, and if not, which is correct?

Thanks!

[18Fiatsandcounting]

Welcome! Not sure I follow your question, though. On all the earlier model spiders that I've run across, the bleed screw is an 8 mm socket both front and rear, and the nipple itself is a little larger than 6 mm. Do you think you might have aftermarket brakes installed?

-Bryan

[Vintageant]

Thanks Bryan,

Yes, the bleed screws are 8 mm socket both front and rear, but the the nipple OD sizes are different, making bleeding a pain! If a little larger than 6mm is correct, the smaller 5mm nipples on the front may be after-market/replacement. Maybe I'll order two new from Autoricambi and see which of the existing they match.

[18Fiatsandcounting]

As it happens, I was rummaging around in my box of spare brake parts this afternoon, and so I went and measured the OD of the nipples for about 6 calipers. All were between 6.0 and 6.2 mm, but more seemed to be the higher number. No correlation to front or rear that I could see, and there's no obvious damage to any of the bleed screws so I can't explain why the slight difference. I did measure with a caliper, so the measurements are accurate.

Hope that helps.

-Bryan

[SteinOnkel]

Almost every car I've ever owned had mismatched bleeders. All sorts of weird wrenches so try before you commit to loosening them. The inner threads are M10X1.0 on Fiats (and most European cars).

Take them out, bin them and buy new ones. Trust me, you don't want to strip these. If you do, you can basically bin the caliper

[Vintageant]

Thanks all. Have ordered 4 new bleeders. Owning to fairly recent bleeding, am reasonably confident the old ones will come out without issue.

[18Fiatsandcounting]

Sounds like a plan. For the last couple of decades, I've been wrapping the bleed screw with one loop of thin Teflon tape, being very careful to cover only the threads and not the sealing area. Seems to work just fine, as I haven't had a bleed screw problem in a long time. There are also anti-seize lubricants that you could try.

-Bryan

[RRoller123]

I like that PTFE tape idea! Going to try that next time.

[Vintageant]

Epilogue: Four new bleeder screws received. OD ranged from 6.08 to 6.11. The old bleeders removed (easily) from the rear measured 7.95 and 8.09

Thanks again!