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I've been killing a lot of time just recently researching and theory building gravel bikes. Couple of things have been said about the GRX Di2 levers vs the mechanical levers.
One is that the GRX Di2 lever might well be the most ergonomic thing that Shimano have ever made. One tester saying they'll probably spec those shifters on every road build they do as well.
The other being that Shimano have move the brake lever pivot and added a servowave mechanism to the Di2 lever which means that it's now possible to obtain all the required braking power while riding in the hoods.
Does anyone have first hand experience of trying both GRX levers? Is the comfort and braking performace really as night and day as they suggest? If so, that makes the Di2 a bit of a no brainer (funds permitting)
As I understand it, the Shimano calipers, from the point of view of piston sizes and oil volume are the same for MTB, road and gravel. With that being the case, I've been looking at the Hope RX4 calipers. They are compatible with Shimano Road and Shimano GRX mechanical, but not GRX di2. Now, clearly that is something to do with the servowave. However, if Shimano can use the same caliper for both, why can't Hope? Any ideas?
https://bike.shimano.com/en-EU/product/component/grx-11-speed/ST-RX810-R.html
Doesn't the mechanical lever have Servo Wave too?
Interesting, I thought it was only on the Di2
In all versions of Shimano hydraulic brakes (685, 785, 7000, 9100, 815), I’ve never had any trouble achieving enough power to lock the rear and often the front wheel from the hoods.
Fair enough, but GXR has been tweaked to give better braking performance. The question remains whether this applied to just the Di2 version, or all GRX shifters.
The diagrams I've found showing the shift if 18mm for the pivot only mention the 815 di2 version.
https://bike.shimano.com/en-EU/technologies/component/details/servo-wave-action.html
This page seems to suggest that the mechanical GRX levers do have servo wave.
I can say that the mechanical levers are a noticeable step up from the RS685 levers in terms of braking power and are really very very good.
Yep, looks like they all have Servo Wave but the GRX Di2 has 18mm more leverage for increased power.
Which must be why Hope say the RX4 isn't compatible but then Shimano still spec the same caliper. Confusing
I think the GRX levers have higher pivots for better braking on the hoods too? That’s probably where the extra length comes from? Not sure whether that applies to all models.
If the Servowave gives more rotor clearance it would be a huge benefit. My RX4 callipers with Ultegra STIs are amazing in every respect, other than he clearance is wafer thin, meaning perma-noise when riding in filthy conditions.
I’ve got the new di2 levers on grx form and they are a huge improvement to the Ultegra they replaced. I’ve also got the grx brakes and they are super powerful
What ‘level’ is GRX equivalent to? It’s confusing since there are different levels within GRX but is the posh GRX ~ Ultegra?
Yes GRX 800 series is roughly Ultegra level, 600 roughly 105 and 400 Tiagra.
@superficial
I believe it's:-
GRX800 - Ultegra
GRXX600 - 105
GRX400 (10 speed) - Tiagra
@sheck
Interesting comment and makes sense. Less clearance from the rotor suggests they've increased the hydraulic advantage to get more power. I did read one review of the RX4 where the tester said they got more clearance but that didn't pass the logic test if they're getting more power.
@NZCol
Good to hear from someone running them. It seems like they all share the same caliper so the hydraulic gain is the same in all systems. If it's just extra leverage, then I guess there's more lever pill (which seems like no bad thing to me). That must be why the RX4 won't work with them. If the Hope RX4 also required more lever travel due to a change in hydraulic advantage and the GRX Di2 increases the mechanical advantage, perhaps they just end up pulling to the bar when used together.
I'm not sure there is more lever travel. I think the pivot point is just higher so your fingers are naturally further away from the pivot so you pull with less force.
Doesn't explain why Hope say their caliper won't work, though.
I have to say that the braking on the mechanical GRX 800 is sufficiently impressive that I wouldn't consider Di2 just to get better braking.
I'm also tempted by Di2 as people say the ergonomics are better as well.
If I wasn't happy with the GRX810 braking, at least that's still compatible with the RX4
I’m running GRX 815 Shifters with Hope RX4s on two bikes and they work just fine.
I couldn’t see the logic in Hope’s exclusion of the 815s and when I asked the service team, no one could give me an answer as to why they were incompatible, so I just did it anyway. 10months in on one bike and 6months on the other with a combined 4000km without any problems.
@Daffy
That's great to hear. Did you set that up from the get go or did you run the standard calipers first? Have you noticed any reduced clearance off the rotor or increased noise when it gets gritty?
No, I’ve ran the RX4s from the get go. I don’t have any calliper rubbing on either bike even in crappy conditions, but haven’t gotten the bikes truly, like winter mud fest, dirty.
Proper winter dirty will make anything sound gritty at least some part of the ride.
I can make the front rotor rub very slightly on the calliper when heaving out of the saddle on the Litespeed, but think it's more a problem with the Selcof fork, but the wheels spin forever with no rub at all.
Recently upgraded my commuting/winter bike and cx/gravel bikes to DI2. Both have the 785 lever which is really comfy for both road and offroad. Considerably cheaper if you look on ebay for them. Worth considering if you are doing a build from scratch.
In terms of calipers I have Hope RX4s on the commuting bike and Shimano flat mount on the CX bike. The Hopes are definitely more powerful but the Shimano also work fine. I did consider putting RX4s on the CX but it was half the price for the Shimano ones so just went with them. Just hope they don't start leaking like my previous 785 callipers did.
Another build tip if you want to have the bluetooth wireless connectivity. Get the XT MTB display unit. It provides a three port junction box with built in bluetooth for just slight more than you would pay for the just the junction box in the normal set up. Have them on both bikes and will probably get one for when I convert the road bike to DI2.
Was always a bit sceptical about DI2 but it is just very good. Full syncro shift on the commuter is great. Also the XT MTB rear mech is a good choice for a gravel bike.
Regards