Flat Mount or Post Mount? Check Before You Order a WHEELTOP EDS Disc Groupset
Several buyers asked whether the WHEELTOP TX disc calipers come in post mount. Here is how to tell which mount your frame uses, and which WHEELTOP disc brakes fit which.
Several buyers have asked whether the WHEELTOP EDS TX disc groupset can come with post mount calipers. Another asked what "flat mount" actually means and sent photos of his own calipers and rotors so we could check them against the kit.
It is a fair thing to be unsure about. Caliper mounting is the one part of a disc groupset you can't fix with the app, a different cassette or a longer chain. This article is about getting that check right before you order.
The short answer
- WHEELTOP EDS TX hydraulic disc calipers: flat mount only.
- WHEELTOP EDS GeX (RA7800) calipers: flat mount only.
- WHEELTOP four-piston brake (BR-MA3000) sold with the OX 2.0: post mount only. It will not fit flat mount tabs.
So there is no post mount version of the TX caliper, and that was the disappointing answer for the buyers who asked. One replied that it wouldn't work for him. We would rather you hear that before ordering than after.
What flat mount and post mount look like on a frame
The buyer who sent photos described flat mount well: the calipers rest against the frame face and are clamped by screws that go into holes in that face. That is flat mount, which our GeX listing calls the standard on modern gravel frames.
Post mount is what mountain bike frames and forks use. The listing for the OX four-piston brake describes it as direct mount, with adapters that bolt straight onto the tabs. It also says plainly that the caliper does not fit flat mount tabs, and that you shouldn't order the kit if your frame uses flat mount.
A quick check at the bike
- Flat mount: the caliper rests against the frame face and is clamped by screws that go into holes in that face.
- Post mount: the caliper is direct mounted onto the tabs.
- If you are not sure which you have, photograph the mounting area and send it to us before you order. One buyer sent photos of his calipers and rotors and asked us to check them.
- Note your rotor size at the same time: 140mm or 160mm for TX and GeX.
Which WHEELTOP kit for which frame
Road and gravel, flat mount: TX or GeX
The EDS TX disc brake kit is a 2X drop-bar system with front and rear derailleurs and carbon fibre levers. Its calipers are one-piece CNC units with full ceramic pistons, shark-fin heat sinks and a one-way oil circuit, running mineral oil. A 140mm rear rotor mounts directly, while a 160mm rear needs the R160-01 adapter. At the front, a 160mm rotor uses F160-02 and a 140mm uses F140-02.
The GeX is the 1X gravel version. It has an integrated hydraulic brake-shifter lever and RA7800 flat mount calipers with 21mm dual ceramic pistons, for 140mm or 160mm rotors. The hoses are pre-cut at 900mm for the front and 1,550mm for the rear.
Mountain bike, post mount: OX 2.0 with the four-piston brake
If your frame is post mount and you ride a flat bar, the OX 2.0 with the four-piston brake is the one built for it. The BR-MA3000 caliper is a CNC one-piece four-piston unit with cooling fins, running mineral oil, and it takes 140, 160, 180 or 203mm rotors between 1.8mm and 2.2mm thick. The BL-MA3000 levers are interchangeable left to right and clamp at Φ22.2, so this is an MTB-style cockpit rather than a drop-bar one.
Two practical notes. The hoses ship separately from the calipers (90cm front, 160cm rear), so you connect and bleed them yourself, and having a bike shop do it is recommended. And the lever's hose connection is a rotating swivel joint. If it turns, that is the design working as intended, so don't tighten it with a screwdriver.
What if you ride drop bars on a post mount frame?
This is the gap the buyers ran into, and we won't dress it up. The TX and GeX calipers are flat mount only, and the post mount brake is built around flat-bar levers.
One GeX buyer did fit his kit to a post mount frame using a flat-mount-to-post-mount adapter. We can't promise it will work on every frame, and we have not confirmed any adapter combination for your bike. If you are considering it, message us with photos of your frame first. The TX rim brake version is another route, but only if your frame takes rim brakes, since the disc and rim builds are different kits.
What buyers say about the hydraulic side
A customer who fitted the TX hydraulic set on his son's bike wrote:
Install and tuning were dead simple. I do wish there was a little more flex in the brake hoses. If you have the ability swapping these with an aftermarket hose might be nice. Otherwise shifting and braking have been on par with or better than previous big name group sets he's used.
A GeX buyer mentioned a different snag:
Only slight snag was I struggled to get a standard bleed valve onto the shifter - so I bleed from the caliper instead and seems ok.
He also wrote that "Shifting is great, and brakes are sharp." If a standard bleed valve doesn't seat on the lever, bleeding from the caliper end worked for him.
Checklist before you order
- Mount type: flat mount means TX or GeX; post mount means the OX four-piston brake.
- Handlebar: drop bar (TX, GeX) or flat bar (OX).
- Rotor size: 140mm or 160mm for TX and GeX; 140 to 203mm for the OX brake.
- Chainring setup: the standalone TX kit is 2X with a front derailleur, while the TX full-groupset bundles also come as 1x11 and 1x12. GeX and OX are 1X.
- Cassette: the TX handles up to 36T, and the GeX and OX long cage handle up to 52T. Our compatibility guide goes through the details.
Aoeagle sells genuine WHEELTOP kits sourced directly from the WHEELTOP factory, as a WHEELTOP partner. If you can't tell which mount your frame has, send us a photo and we'll tell you whether the kit fits before you spend anything.