Like this site? Help us to make it better.

r3pro Piston Release Tool



Genius tool that solves a very real problem at an affordable price
Perfect fit
Quick and easy to use
Contact: Recommends

This product has been selected to feature in recommends. That means it's not just scored well, but we think it stands out as special. Go to recommends

At every product is thoroughly tested for as long as it takes to get a proper insight into how well it works. Our reviewers are experienced cyclists that we trust to be objective. While we strive to ensure that opinions expressed are backed up by facts, reviews are by their nature an informed opinion, not a definitive verdict. We don't intentionally try to break anything (except locks) but we do try to look for weak points in any design. The overall score is not just an average of the other scores: it reflects both a product's function and value – with value determined by how a product compares with items of similar spec, quality, and price.

What the scores mean

Good scores are more common than bad, because fortunately good products are more common than bad.

  • Exceptional
  • Excellent
  • Very Good
  • Good
  • Quite good
  • Average
  • Not so good
  • Poor
  • Bad
  • Appalling

The r3pro Piston Release Tool is a genius bit of kit for servicing stuck or sticky four-piston Hope callipers. It makes an otherwise devilish job a piece of cake.

If you run a four-piston calliper like Hope's excellent V4, at some stage it's highly likely one of those pistons will get sticky and not want to advance at the same rate as the others. This leads to uneven pad wear and rubbing.

> Buy now: r3pro Piston Release Tool from r3pro for £9

On a two-piston calliper it's easy to rectify this – you hold one piston in with a dedicated tool or just a ring spanner, while squeezing the lever carefully to advance the recalcitrant piston out. Once it's at its maximum (but not so far as to eject completely), you can clean it up using a cloth, bottle brush or, my go-to, some alcohol-moistened string wrapped around the piston and sawed back and forth to wear off any caked-on muck.

But a four-piston calliper is a completely different sack of rodents. You're now trying to hold back not one but three pistons as you squeeze the lever. Even if you have a spare person and the right shaped tools to all fit into a tiny calliper entrance, there's likely to be colourful language and the real risk of going too far and popping the piston out, facilitating a huge faff reinstalling it and a full bleed.

2022 r3pro Piston Release Tool - after removal.jpg

Enter Phil Lee from r3pro (pronounced 're-pro'). Phil founded r3pro to make 3D-printed bits for mountain biking, and the tool on test here solves the above issue of freeing up or advancing a single piston at a time on a four-piston caliper. This particular one is designed for the Hope E4, V4 and RX4 callipers. If you have the Shimano version of the RX4 calliper (as I do), the pistons differ from the SRAM version, so you order the E4 version of the tool.

The concept is fiendishly difficult, the solution elegant in its simplicity. The tool is simply a block of plastic, with a cut out area that lets one piston advance while holding back the other three. The tolerances are sub-millimetre, so the piston advances exactly as far as it needs to without risking leaking fluid. Whether the piston was genuinely stuck, a bit sticky, or you just wanted to be proactive in cleaning it up during a pad change, the tool does the job perfectly.

2022 r3pro Piston Release Tool - before advancing piston.jpg

As well as this tool designed for Hope E, V and RX4 callipers, there are also versions for SRAM Code, SRAM Guide, Magura MT5 and Shimano's common four-piston callipers such as XT, XTR, Saint and Zee.

What it's not, obviously, is a bleed block. r3pro sells those too. It also sells calliper alignment tools for various brands, to help get the calliper perfectly central over the rotor.

> Everything you need to know about disc brakes

If you buy multiple tools at once, you get a £2 discount. Notably, it doesn't sell a pad or piston push-back tool, but as these are metal tools with handles it's not r3pro's 3D-printed vibe.

For £11.50 delivered, in one of nine colours, it's a bargain, and given the pretty much inevitable problem it solves both easily and quickly, a must-have for anyone running four-piston brakes.


Genius tool that solves a very real problem at an affordable price test report

Make and model: r3pro Piston Release Tool

Size tested: Hope E, V and RX4 callipers

Tell us what the product is for and who it's aimed at. What do the manufacturers say about it? How does that compare to your own feelings about it?

It's for people with 4-piston brakes who want to keep them running sweet.

r3pro says:


Tell us some more about the technical aspects of the product?

Hope E4

Hope RX4 (Shimano version select E4 tool)

Hope V4

9 colours

Rate the product for quality of construction:

3D-printed from hard plastic, looks great.

Rate the product for performance:

Fits and works perfectly.

Rate the product for durability:

Very hardwearing.

Rate the product for weight (if applicable)

It's only 10g – if you put it in a travel bag or tool case you wouldn't notice.

Rate the product for value:

It's a unique tool, so I can't say it's better or worse value than rivals as there aren't any... but for £11.50 delivered, given the huge faff and pain it solves, it's well worth it.

Tell us how the product performed overall when used for its designed purpose


Tell us what you particularly liked about the product

The precise fit.

Tell us what you particularly disliked about the product


Did you enjoy using the product? Yes

Would you consider buying the product? Yes

Would you recommend the product to a friend? Yes

Use this box to explain your overall score

As this is a unique tool that works perfectly, and doesn't cost much for the problem it solves, it's one for the 'exceptional' tag.

Overall rating: 10/10

About the tester

Age: 47  Height: 183cm  Weight: 77kg

I usually ride: Sonder Camino Gravelaxe  My best bike is: Nah bro that's it

I've been riding for: Over 20 years  I ride: A few times a week  I would class myself as: Expert

I regularly do the following types of riding: cyclo cross, general fitness riding, mtb, G-R-A-V-E-L

Living in the Highlands, Mike is constantly finding innovative and usually cold/wet ways to accelerate the degradation of cycling kit. At his happiest in a warm workshop holding an anodised tool of high repute, Mike's been taking bikes apart and (mostly) putting them back together for forty years. With a day job in global IT (he's not completely sure what that means either) and having run a boutique cycle service business on the side for a decade, bikes are his escape into the practical and life-changing for his customers.

Add new comment


mike the bike | 2 years ago

The chances of me buying 4-pot callipers are vanishingly slim but I have to recognise the inventor's genius here.  It fulfills the requirements of a top-notch solution to a problem in that it's effective, simple and cheap(ish).

I suppose someone will moan that it's made of plastic and not recycled corn cobs but some folk are never happy.

kil0ran replied to mike the bike | 2 years ago

I'm tempted to upgrade to 4 pots just so I can buy this tool.

hawkinspeter replied to kil0ran | 2 years ago
1 like
kil0ran wrote:

I'm tempted to upgrade to 4 pots just so I can buy this tool.

Pffft! I'm waiting for 6 pots and a new version of this tool (maybe you'd need two or three different types).

wtjs | 2 years ago
1 like

This is so obviously excellent that it's a pleasure to read about it- I have experience of only one disk brake bike, which I never tire of praising (with superb TRP Spyre), but if I ever get hydraulics this will be my first purchase. Can't imagine why anyone wouldn't, particularly combined with the reviewer's tip about preventive maintenance with meths-soaked string!

ktache | 2 years ago

Great tool. Need one of these, there is always one piston...

Will be buying all 3 tools for my brakes, might only really need two, but might as well.

ktache replied to ktache | 2 years ago
1 like

Phil is truly a genius.

Made bleeding my Hope Tech 3 E4s so much easier. Weirdly it was the spacer tool that I thought I might as well get that I used the most, but the other two are much more exacting, specific and difficult to do without.

I will be emailing him soon enough with my thanks.

Buy the tools for your brakes or ask him to make them for the ones you've got.

All I need now is something to hold the bars at the right angle, inner tube was alright but I could do with something much more secure.

Latest Comments