Does anyone know of an existing hydraulic brake lever (eg (like this)) that can clamp on a 31.8mm bar or can anyone think of a way I can hack/bodge/modify one?

I'm thinking similar to how CX bikes do it with cables except I want it not inline (separate brake) and hydraulic


  • I only have a right hand
  • I'm building a road bike with drop handlebars and a hydraulic disk brake (Shimano r8070, right-side, front brake).
  • I have been happy with a single brake for 20+ years but since having kids I feel like a second, backup, brake would be wise

Out of the box solutions welcome!

  • Here something that might be of interest singletracks.com/blog/mtb-gear/… bicycles.stackexchange.com/questions/42450/… has an answer for flat bars.
    – mattnz
    Jun 28 '19 at 22:04
  • Is a coaster brake an acceptable solution to get a second independent gear that isn't hand controlled? You'd loose your derailleur gears and have to rebuild the rear wheel onto an internally-geared hub like a shimano alfine11 or a rolhoff,
    – Criggie
    Jul 29 '19 at 0:11
  • @Criggie thanks for your input but that is a step too far for me! Aug 23 '19 at 17:29

Shimano's new GRX line include "sub-levers" that seem to fit your needs.

They are meant to be mounted on the tops of drop bars near the stem and run along the same hydraulic line as your main hydraulic lever/shifter. The product ID I believe you need would be BL-RX812-R (or -L if the left was desired)

enter image description here


  • Wow that seems almost perfect! My only reservation is that I would need to route a hose from my left-side shifter (rear brake ST-R8070) over to this on the right of the stem then back over to the left to go in to my frame, maybe the hoses can't bend that much? Maybe I could mount it upside down to help? Or is there any way this can be used standalone? Jun 28 '19 at 19:23
  • @OrganicPanda Ohhh I see. I thought you wanted this to actuate the same brake. Yes the hose routing does seem problematic. Perhaps an I-Spec mount lever could be clamped to a 31.8 mm bar.
    – Paul H
    Jun 28 '19 at 20:07
  • @OrganicPanda no that won't work. The I-Spec shifters slide into the brake levers' clamps, not the other way around.
    – Paul H
    Jun 28 '19 at 20:12
  • Thanks anyway! I ended up buying an i-spec lever, cut most of the clamp off and bolted it to a 31.8 clamp I found on eBay - it's a super hack but it works pretty well Aug 23 '19 at 17:32
  • @OrganicPanda I'd love to see photos of the final set up if you get a chance
    – Paul H
    Aug 24 '19 at 4:00

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