Electronic & Hydraulic Shifting (Di2, Ui2, customisations)

I’ve had mine go into partial crash recovery mode before, where it’s works part way across the cassette. It was confusing, as I hadn’t crashed, but a reset sorted it out.

But it wouldn't be changing any other gears if that was the case.

Ok, that's just odd.

Holding down the Junc A button until it moves its ass is my usual go to when anything odd happens.

Did a reset just in case, it went through the bits of the cassette it could. No change.

Did the limit screw in both directions for good measure. No change.

I guess next job is to take the mech off the hanger and take a look at that but visually it's not obviously bent and I'd imagine to lose 3 gears it'd need to be really bent.

Can you hear the servo struggle when it gets to the end of it's range, at cog 8 or whatever?

Like it's trying to change further but hits a physical limit and backs off.

No. That's the thing, it just seems to stop like that's as many gears as it has.

Edit - should say I bought the mechs and shifters 2nd hand and I know for a fact they were "lightly crashed" about 18 months ago so it's possible the rear is fucked.

Think I'll take the mech off, see if it shifts the right number of gears attached to my other bike.

Yeaaaah. So it didn't. Might run it into the LBS on Monday when they reopen or maybe I'll just use it as a weak excuse to buy an RX mech for the gravel bike and swap the 8050 to this one.

Wonder if whatever sent the rear into crash mode also broke something inside.

Yeah, sounds a bit fuxxored. What model RD is it?

Ultegra 6870

I've crashed a few of those. I don't have my spares to hand though. Could've seen if any parts were swappable. I wonder if some judicious bending will get it moving through the full range.

At least if you get one of the new Shadow ones you'll be able to run bigger cassettes (it's all the rage).

You could try a firmware update. All you need is your charger and a laptop. Download the etube app and plug the bike in. Easier to do with phone and bluetooth widget if you have it.

Also try double tapping the junction box button to ensure the bike is in the correct mode. 1 flash manual, 2 flash semi syncro, flash syncro. Could be doing something weird there.

Also try with the mech and chain removed from the bike to see if it does 10 shifts.

First and third I already did. The second can't be the issue as it won't shift into the biggest three cogs when it's in the small ring.

Does it shift into them when in the big ring?

No... as I said, it's like I've got an 8-speed groupset now. Will connect my 8050 mech to the shifters on this bike but given it doesn't shift when connected to the other di2 bike, I doubt it'll make a difference to the mech.

Anyone know if the RX805 mech will fit a 40T cassette like 8050 does?

Pretty sure it's 34t max. Get yourself a Grx mech instead.

The long cage is meant to do 34T so it might go to 40T like the 8050.

I'm running the new style Tiagra cable RD on the grrl's road bike with a 36T but I didn't try anything bigger.

That's quoted max. It's almost never actual max.

This guy has 46T with Wolftooth, so depending on your bike I'd guess 40T would work. I've run 42T on 8050 with no Wolftooth and it's the same RD shape so you should get most of the way there.

https://www.ridinggravel.com/forum/?p=%2Fpost%2F4634-1140t-di2-custom-drivetrain-10419457

Also:
https://www.youtube.com/watch?v=W7yfXJPuBus

What @hippy said... I've had a 40T on my 8050 which is also 34T. Problem with the GRX is the minimum of 40T as I have a 34T on my tripster most of the time as it's the bad-weather/spare road bike too.

I've a mechanical RX running on a 42T cassette, b screw fully maxed. With wolftooth its easily done but I lost the screw for it.

I'll give it a shot once I've tested the shifters with a different mech to make sure the whole lot isn't broken

I'm running a RX805 with an 11-42 and no wolftooth. Works fine.

I have a mate that is looking to remove the Di2 wireless transmitter from one bike he's looking to sell to move to his new bike. Only issue is, removing it will creating a gap in the wiring, how to plug this so that the di2 works? It's fitted I think between the junction box under the stem to the wire routed internally on the frame.

Doesn't he just need to have one cable from the junction box under the stem to the junction box in the frame (assuming he has a front and rear mech and battery in place)?