Disc brake bike build

[flat tyre]

My latest project, I've decided to venture into the dark side and build a road (gravel?) bike with hydraulic disc brakes. I've built several bikes with rim brakes so I've got a reasonable experience of bike building, but this is the first disc brake. I've gone ahead and ordered the frame and now looking at other parts to purchase. Does anyone have any advice, warning of pitfalls etc etc? Don't try to persuade me not to do it as I've already committed money on the frame build! Currently planning to go with Shimano Ultegra groupset.

[Brucey]

…. Does anyone have any advice, warning of pitfalls etc etc? Don't try to persuade me not to do it as I've already committed money on the frame build! Currently planning to go with Shimano Ultegra groupset.

Presumably Ultegra groupset means ultegra (or GRX) STIs and only matching calipers will work with them. If you have ordered a frame then you have presumably already decided between ISO, post and flat mount for the calipers and the disc sizes that will work in the frame.

There are not many choices to make beyond that, are there?

cheers

[tim-b]

Hi
Before you decide on a groupset I'd think about the gear ratios that you want. More gravel/off-road and I'd tend toward GRX 800 rather than Ultegra, and you can go 1x or 2x chainrings. I think that GRX has a slightly wider chainline to accommodate wider tyres, so that's something to discuss with your frame builder
Regards
tim-b

[willcee]

I did this late last year, mine required post mount calipers,originally had hydraulic calipers with s/steel cabling which were OK , but saw an offer of 11sp hydro calipers and flat mounts and jumped.... then I had to source post mount calipers....whose frame are you using??, and as mine is E powered and heavy I used 180mm floating front disc despite Shimano say 160mm only ..doing it again I would only consider through axle type..that said I have had zero issues just the faff of shortening long hydraulic hoses and the bleeding of same without decent bleed nipples, just the hidden shimano efforts.. will

[Redvee]

I went 11sp Shimano Hydro last year but needed post mount callipers on my frame so bought R7020 levers and callipers and kept the callipers as I knew at some point in time I'd go get a frame needing flat mount callipers. Built it all up but wasn't confident about doing the brakes so went as far as I was conficent with and took it to a LBS. During lockdown when bored I bought a new frame and utilised my flat mount callipers and did all the work myself after watching Youtube videos on brake bleed/install. I was so happy with my new skills I swapped a calliper on commute bike in an hour.
Shimano system is easier than Sram to bleed as you fill/bleed from the calliper with one syringe and bleed funnel whereas as Sram needs two syringes to eliminate air bubbles. Once you've ridden a few miles you'll need another bleed to eliminate the last of the air bubbles that have risen to the reservoir from road vibrations.

[mattsccm]

Just make sure that your wheel axles match the frame !

[Navara]

Presumably Ultegra groupset means ultegra (or GRX) STIs and only matching calipers will work with them.

Hope RX4 calipers work with Shimano STis.In fact they work better than Shimano calipers.Definitely worth thinking about.Whilst Shimano calipers are absolutely fine the RX4s offer a much better feel at the lever IMO.

Hydraulic brakes when set up correctly just work.I always said I'd never have them on a road bike but decided to go for it on my new build and am glad I did.

Purists will say don't do it.Don't listen to them!

If your budget allows go for Di2.I can't see me going back now I've got it!!

If in doubt YouTube is your friend.It's no more difficult fitting hydraulics than it is calipers.

[Brucey]

Presumably Ultegra groupset means ultegra (or GRX) STIs and only matching calipers will work with them.

Hope RX4 calipers work with Shimano STis.In fact they work better than Shimano calipers...

I'd class RX4s as 'matching calipers' by design, in that the pistons are sized so that they work with the shimano MC and (in stark contrast to other Hope systems) the caliper seals are compatible with the shimano Mineral oil fluid.

cheers

[flat tyre]

Thanks for comments and advice.

[Navara]

Presumably Ultegra groupset means ultegra (or GRX) STIs and only matching calipers will work with them.

Hope RX4 calipers work with Shimano STis.In fact they work better than Shimano calipers...

I'd class RX4s as 'matching calipers' by design, in that the pistons are sized so that they work with the shimano MC and (in stark contrast to other Hope systems) the caliper seals are compatible with the shimano Mineral oil fluid.
cheers

My bad I think I've mis-read or misinterpreted your post

[reohn2]

My latest project, I've decided to venture into the dark side and build a road (gravel?) bike with hydraulic disc brakes.....

Why specifically hydraulics?

[Brucey]

My bad I think I've mis-read or misinterpreted your post

in truth I wasn't thinking that much about the Hope calipers but maybe I should have been. Similarly I suppose that Tektro/TRP may also make (mineral oil type) calipers which may work with shimano MCs. In any 'mixed marriage' this presumably has warranty implications; if an all-shimano system spits the dummy after 18 months it is covered by warranty. However if there is a different maker's caliper attached you might have an argument instead.

OP has been keen to ask us not to put him off, but then again hasn't bothered to say to what exactly he has already committed himself to either; between caliper mounts, axle types, rear OLN sizes, cable/hose guides and workable disc sizes for the frame that has been ordered, the die has already been cast, in a way that we don't know of....

I've used hydro discs on various MTBs for decades and when they are working they are great. But that isn't always and they can be a fair to middling sized PITA to sort out even in a well-equipped workshop. Annoyingly spare parts supply is such that something as trivial as a faulty seal that ought to cost pennies often results in a scrapped component that costs £££ . And whilst problems on the road are not commonplace the chances of a roadside fix are slight vs a cable-operated system. Perhaps this is not a concern for those whose 'tool kit' for dealing with roadside problems is a telephone with which the long-suffering sag wagon driver is summoned...

cheers

[flat tyre]

A big more info on the frame. It hasn't built yet so I'm in correspondence with the builder to finalise the spec at the moment.

[tim-b]

Hi

A big more info on the frame. It hasn't built yet so I'm in correspondence with the builder to finalise the spec at the moment.

In addition to all of the above, another biggie for me would be wheel size and tyre width: majority on-road and I'd look at 700C and 35mm+ tyres, more gravel and it'd be 650B and 50mm+ tyres, or you could do both in the same frame
Mudguards?
Regards
tim-b

[bgnukem]

Consider that the fork will be stiffer than a rim-brake fork, typically, to cope with the braking forces so you may need a bigger tyre than you would normally use to restore some ride comfort / shock absorption.