Im not confused about barb compatibility, it is just a matter of looking brake specification.
What i am confused about is visual difference. Several times i heard that BH90 has narrower channel while BH59 has wider. But in practice i mostly see opposite, bh90 has bigger channel in oem brakes that i got and this example from aliexpress.
by DeGriz_
5 Comments
Bh59 has a larger ID and uses the larger gold barb. Bh90 Has thicker walls for better brake power and thus a smaller ID. It uses the smaller silver barb
The inner diameter of bh90 hose is smaller, you’ll have a bad time if you cram in a bh59 barb.
Look up your brakeset, the hose type will be listed in the specs.
You can also see visually when you disconnect brakes if you have a gold or silver colored barb
The silver BH90 ones are smaller externally which makes the hole look bigger in comparison.
There is a list online for all/most Shimano brakes stating BH-59 or BH-90, mainly for what barbs you use:
https://epicbleedsolutions.com/blogs/articles/bh59-or-bh90-which-insert-do-i-need?srsltid=AfmBOopxRD8aiBnpdNHLH1FPb7N-3yPz9Rv6f86_xzkPeqNNlRkFvGrb
I always use a garden hose pipe analogy:
BH-59 low pressure.
BH-90 high pressure.
If you use a garden water pipe the water comes out slow. If you squeeze the end tighter it comes out further and with more power. Larger hose hole, lower pressure. Smaller hole, higher pressure. Silver barb is smaller to fit pipe with smaller hole that is a high pressure hose.
Googling pictures of BH-59, or BH-90, will show pictures of silver or gold barbs.