BL-RX812 sub levers and Aerobars, bar bag, etc.

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Posts: 36
Joined: Mon Sep 19, 2011 4:37 pm
Location: France

by Carcinogent

Hi all,

I want to install GRX BL-rx812 sub levers on a 40cm PRO Explore handlebar on an upcoming build and I wanted to know if they have clearance for aerboars for example. I know the levers take quite some real estate on the handlebars, though i am curious if someone has them currently and can give me some insight. I have PRO missile aerobars and the clamps are ~20mm wide. A measuremet of the part of the levers that attaches/touches the handlebar would be ideal... Is the middle section. on 42/44cm bars wider than the 40cm ones?

Here it seems you can shift the levers away from the stem clamp, though would 20mm be too much so that the 'foot' of the brake would be on the narrow part of the handlebar closer to 'R' in Discover (i can probably machine a shim....? Can a smallish clamp fit where the ziptie is in the middle of the lever?

Here it looks the the hose exit prevents a clamp from going in BETWEEN (where the accessory button is) Image

I can order them and return them if they don;t work though it is a hassle, so any help is appreciated. :D


by Weenie

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Joined: Sat Jul 04, 2020 5:45 pm

by satanas

There are at least 4 different Discover bars: 12°, 20° & 30° in alu, plus 20° in carbon. Of these, only the 30° alu bars have round tops, the others are flattened ("Ergo" in Pro speak). On the 40cm 12° bars I have to hand there's enough room for a 22mm aero bar clamp between the stem and where the bar starts to change shape (thinner vertically & wider fore/aft), but not a lot more - around 5mm with a 42mm wide stem clamp - so the total (round, 31.8mm) centre width is something like 42 + 22x2 + 5x2 = 96mm. You'd definitely fit satellite shifters in with either aero bars or sub brake levers, but unfortunately probably not both. I doubt the aero bar clamp can go between the sub brake lever clamp and foot, unless perhaps it's super-minimal like say a Spinaci. The order would likely have to be stem, aero bar clamp, sub brake lever clamp.

Unfortunately, Pro don't list the centre widths of their bars in their spec sheets, unlike some others. I have a set of the same bars in 42cm (and sub brake levers) elsewhere that I could measure but won't be near there before next week, however if you have the round top bars they're likely to be completely different anyway...

The front of the Ergo bars is straight, so as long as there's room for the clamp, the "foot" should be okay. The satellite shifters just need a zip tie, so no big deal there, and a longer one could easily be substituted.

I'll report back, but it'll be at least a few days.

Posts: 368
Joined: Sat Jul 04, 2020 5:45 pm

by satanas

So, the sub levers will (just) fit on a 40cm Discover 12° bar with ergo (ovalised) tops. I've got a Redshift Shockstop stem (42mm clamp width), plus Redshift Q/R aero bar clamps (22mm each), then the sub levers. There's a small gap between the foot and the bar, but tape would fix that; I've just mocked things up off the bike.

The RX-812 levers are ~42mm wide from the inside of the clamp to the outside of the foot, made up as follows:

Clamp part of lever: ~13.5mm, but note the actual steel band is ~9mm
Gap: ~18mm
Foot: ~9.5mm at base (where it touches the bar)

The gap is unlikely to be wide enough to fit aero bar clamps, but Di2 zip ties would easily fit.

FWIW, the (older) 42cm Discover 12° bars I have if anything have a slightly narrower centre section than the recent 40cm bars, but it's hard to measure non-round and tapering things precisely.

Also, I measured several stem clamp widths and most were 39-40mm wide, a couple 42mm, and one older MTB stem was 45mm, so I wouldn't expect to gain much space here by swapping stems.

Best of luck....

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