Hope RX4 Calipers Gut Check
 

Looking for a gut check. Help me out.

I'm probably going to order the flat mount Shimano version of the Hope RX4 four piston calipers.

Reference: https://www.hopetech.com/products/br...d/rx4-caliper/

These will replace RS805 calipers and be used with existing R785 levers. I'm hoping for better feel and less lever travel. Reviews seem pretty positive.

New wheels with centerlock hubs are being built. The old wheels are six bolt and so new rotors are on order. With new wheels and rotors I feel like this is the time to also do the calipers.

Are pads readily available?
Anyone have fitment issues?
Are there any criticisms of these parts?
Is there something better?

What am I missing? What other questions should I be asking?


-Tim-

Pads can be easily had, but you're basically limited to OEM (in metallic or organic.) I haven't found an aftermarket pad. But bonus, each caliper comes with a pair of both types of pad. And they last and last.

I had absolutely no fitment issues whatsoever. I'm on the SRAM version, but install and bleed was a breeze.

Just over 7 months / 3,800 miles with them, and I haven't touched them at all.

And as I had read very little positive about SRAM calipers, I bit the bullet on the Hopes, and have not been disappointed. They are very light, too.

The RX4 calipers are something I would love to have too. Haven't heard anything really negative about them other than a few reviews that claim the pistons were frozen when they arrived new in box.

I have heard complaints of the 1st generation shimano hydro levers having the very same issues you are speaking of. Maybe a new set of sti controls is what you need instead of just the calipers? Although new controls may be about double what the calipers will cost, but will most likely solve your current issues. Since you already have Di2 the swap over would be easy. Backcountry has a decent price and they are in stock too. If you use a rebate site like Activejunky you can usually get another 8%-10% cash back on your purchase. I have used it without issue many times.

https://www.backcountry.com/shimano-...RlZ3JhIGRpMg==

The trigger has been pulled on the Shimano flat mount RX4 calipers and I'd like to get a few extra sets of pads.

Does anyone know what pads these take? Are they the E4 pads I'm seeing everywhere?

Hope’s website shows the pads as Hope part number HBSB323 for both front and rear but I can’t seem to find these online.

Front: https://www.hopetech.com/_repository...nt-Shimano.pdf
Rear: https://www.hopetech.com/_repository...nt-Shimano.pdf

Hope's reply...The RX4 shimano calipers use the same pad as the E4, the part number for sintered is HBSP323S
-Tim-

Looks like I joined the RX4 club too. Gravel roads and trails in my area mostly means steep fire roads in various states of disrepair and/or neglect. I find myself climbing and descending these roads and trails far more often than I expected. Long, steep descents with relatively skinny tires (38c) and no suspension for me means riding the brakes just about all the way down the hill.

My Sram Force brakes work OK, just not great. My shimano ultegra disc brakes on my road bike have far better stopping power and modulation. I am getting hand cramps from the amount force required to slow myself down. Aside from upgrading what is basically a brand new groupset, the RX4 brake calipers seem like the best solution. I picked up a set of the new Shimano XTR RT-MT900 rotors too. Everything should be here by next week. Will post up a review once it's all set up and the pads are broken in.

Nice. The RX4 Club. :)

Mine are sitting on the kitchen counter as a shrine to procrastination.


-Tim-

i want to be a member of this club too!
i'm getting a little tired of the piston advance and cleaning work i need to keep my rival calipers quiet and happy.

Two weeks ago Merlin had the best price.

https://bikes.merlincycles.com/search?w=hope%20rx4

Took forever to get to suburban Atlanta.

Ordered from Merlin as well. Opted for the free shipping but hopefully my order will show up quickly.

I also decided to swap out the bore caps. Inspired by this marketing photo from Hope. In for a penny, in for a pound.

https://cimg7.ibsrv.net/gimg/bikefor...3b590f1e92.jpg

A man after my heart. :)

My daughter is going to grad school @ Berkeley next year and there is surely a trip to the area in my future. I'm looking forward to you showing me the sights.


-Tim-

Sounds like fun, hit me up when you're in town.

interested to hear if this actually ends up being the case. The RX4 uses a 16/14mm piston combo and the RS805 uses a 21mm piston, which equates to 1420mm^2 vs 1385mm^2 surface area per side. Since the lever reservoir chamber piston isn't changing sizes this should increase the lever travel while increasing pad force slightly. I would have probably liked to see 14mm all around or a 15/14mm combo.
Edit: Got my dimensions wrong, the shimano caliper uses 22mm pistons for a SA of 1520mm^2, so the hopes should decrease lever travel and hopefully the decreased pad force is balanced by the better presure distribution on the larger pad.

By the by RX4's with new Shimano road is just for bling. If you want 4 pot with Shimano road you can use the MTB calipers as they are now cross compatible. Something like MT520 calipers are super cheap. For SRAM however it's your only option. Although for some reason and might be placebo my Rival hydro brakes got tons better when I bled them with Motul DOT5.1 vs the sram branded stuff.

I've thought about going with the M820 on the front just for the larger pads since I'm burning through resin pads on my RS785 calipers every 1k or so

The only other caveat is flat mount vs post mount calipers. I haven't seen any MTB bikes that use flat mount.

I was actually thinking of using the DOT 5.1 fluid. I'll give that brand a try. Thanks for the tip.

Yeah I don't mind using the post to flat mount adapters. Plus it doesn't shoehorn having to use those calipers in road only.

Anybody know if the RX4 calipers would work with TRP Hylex RS levers?

This I don't doubt.


-Tim-

Finally got my calipers on and went for a test ride today. I will say the braking performance is much improved over the Sram Force brake calipers.

My replacement purple bore caps came in the wrong size so I opted to install the calipers as is. I also had an issue with the rear caliper being shipped with only 1 set of brake pads. The blue ones, while the front caliper came with both red and blue backed pads. Anyone know the difference between the 2? The included paperwork doesn't mention anything and neither does the Hope website.

I installed both calipers with the blue colored pads and Shimano RT-MT900 XTR ice tech rotors. The bleeding process was straightforward and went quickly.

My initial impressions were very positive. Once the pads were bedded in and I got them hot they began to squeal and howl very loudly. Braking starts with the usual pad contact noise, followed by a high pitch squeal and the loud howling starts. I plan on swapping in the red pads on the front as it seems to be the worst noise offender. I am also looking into some organic swiss stop pads as I read they are extremely quiet. But, aside from the noise, the calipers do deliver the extra braking power I was looking for.

In the very last pic you can see by the wear marks the Hope pads are wider than the Shimano braking surface. I wonder if the Hope rotors would be a better match with a wider brake surface? I opted for the Shimano rotors mostly because of the lack of centerlock rotors from Hope. I may just bite the bullet and get the hope rotors and the centerlock to 6 bolt adapters once I get the pad noise issue resolved.

https://cimg4.ibsrv.net/gimg/bikefor...1afc43073c.jpg
https://cimg5.ibsrv.net/gimg/bikefor...5b3848b176.jpg
https://cimg7.ibsrv.net/gimg/bikefor...3e69a4fa0e.jpg
https://cimg6.ibsrv.net/gimg/bikefor...a21fc1eabd.jpg

My front's only came with red pads.

Makes me wonder if someone at Merlin is stealing the pads out of the boxes.

I read somewhere that blue was for road and red for off road. Not sure what exactly is different about them buy my guess is that one is organic/resin while the other is sintered/metallic.

Hope and backcountry.com both confirmed via email that E4 pads are a direct replacement.


-Tim-

I will contact Merlin tomorrow about the missing pads.

I swapped in the red pads and went for a short ride. They seem better, will know more once I get them good and hot.

I'd space the calipers out with a washer or two under each bolt.

Just an update. Contacted Merlin and they are going to send me a set of the missing pads. But they are waiting for Hope to ship to them, and then to me. Since it will be a while to get them I went ahead and ordered a set of the Hope E4 brake pads. Turns out they won't fit, too big.

I started poking around the internet and found out the Shimano version of the flat mount RX4 calipers are bigger than the Sram flat mount RX4 calipers. This explains why I got the wrong size bore caps. The Sram calipers use brake pad HBSP359 which, as mentioned, is smaller than the E4. Somehow I downloaded the wrong pdf file and ordered parts for the Shimano calipers. My fault.

So, I now have a set of purple bore caps, installation tools, and organic brake pads for calipers that I don't own. The pads I can return to Jensen. Will need to talk to the shop about exchanging the bore caps for the correct size.

I guess for now I'll just have to deal with the noisy rear brakes. I ordered another set of pads from a different source, they should be here next week.

This might have been my fault.

I've been posting that the E4 pads fit the RX4 calipers but didn't even think about SRAM vs Shimano.


-Tim-