10mm fittings on 3/8 brake line?

EyeMWing

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I'm almost 99% sure this is fine, but I wanted to double check. 3/8in brake tubing, flared with the 3/8ths die - is it safe and sane to use a 10mm fitting? Or do I need to go sacrifice some money to the metric gods to fix Dad's terrible Honderp?

(For the record, 3/8ths fittings will totally thread into a 10mm hole - and not seal)
 
I wouldn't either. While the line will work, the flare certainly won't (at least not long term) as Honda's metric flares are a different profile than SAE fractional ones.
 
Ah damn. Didn't know the flare profile was different. Guess I'm buying tools (or I'll just toss adapters on like I did with the ZX2 when I accidentally used SAE fittings)
 
Ah damn. Didn't know the flare profile was different. Guess I'm buying tools (or I'll just toss adapters on like I did with the ZX2 when I accidentally used SAE fittings)

They are *very* different, IIRC: http://www.fedhillusa.com/webnuts/common flares6.pdf

However, you might want to go double check - and both Honda and the aftermarket sell pre-formed ready to install hardlines for cheap, cheaper than the tools will be.

- - - Updated - - -

For that matter, what line rusted out?
 
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The long one. From the ABS to the rear of the car, over the top of the tank to the right rear. Blew out above the tank.

I was going to cut my own line to route around the tank, because screw that.
 
Factual corrections now that the job is actually done:
1) I meant 3/16 every single time I typed 3/8.
2) Honda (and apparently most Asian imports) *DO* use the 3/16 SAE flare on 10mm fittings. The fittings are distinct from 10mm bubble flare fittings that are more common on European vehicles. Retail auto parts counter folks can be made to give you the correct fittings by saying "10mm European" or "10mm Asian".
 
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