Converting road bike to discs

[Rocksteadyeddie]

Has anyone had a go at converting a standard steel road frame to run discs. Assume there is a requirement to weld on some bosses and a respray?

[jamiebae]

Seems a strange thing to do, but yes, you will need disc mounts, and also to be sure the frame, and especially fork is strong enough to take the stresses from the brakes. My carbon disc roadie has an extra brace between the chainstay and seatstay to transfer forces from the caliper.

[Rocksteadyeddie]

For a winter commuting hack.

[jamiebae]

Fair enough, not sure I'd be wanting to subject an old steel fork to the stress of having caliper mounts welded onto it, then the forces of discs acting on it in a way it was never designed for.

[JPJ]

Also, most disc hubs are 135mm, not the 130mm of normal road bikes. Okay, so it wouldn't be out of the question to stretch the steel frame to get the hub in, but it's another thing to think about.

[jamiebae]

My disc roadie has 130mm hubs, wheels are available in this size so it can be done. Range is limited though, certainly you can't just use cheap MTB 29er wheels.

[TheLemming]

There was a similar thread on another forum a while back.

The verdict was it CAN be done, but the question is whether it should.

[donfisher]

jamiebae said:

Fair enough, not sure I'd be wanting to subject an old steel fork to the stress of having caliper mounts welded onto it, then the forces of discs acting on it in a way it was never designed for.

I think that the easier thing would be to replace the old fork with something off a CX bike or similar. In fact I suspect it would be easier and maybe better to make a rigid forked disc equipped hybrid or MTB more roadbike like than it would be to convert an old road bike to take discs.

I’ve just bought what Whyte call a CX bike but I would call it a drop bar flat bar road hybrid with cable operated discs. I’m aware that this might be an initial set up issue but the brakes, while strong, are not that much better than my roadbike’s rim brakes. But I’ve only used them in the dry. I went for discs on this type of bike becuase I figured that using these through winter and the daily commute would mean less rim and pad cleaning and a reduction in moments where, due to everything being soaked, the brakes basically don’t work in that initial panic brake – this may or may not be the case.

Hydraulic disc brakes are clearly what to move to. Until someone offers a reasonably priced hydraulic system at all groupset prices then I wonder if for those awful wet-through journeys you’d be better off just using a different bike.

In answer to, or to just add more to the original question though, probably getting a CX type fork would work. As above, would the gap at the back fit a hub + cassette + disc (I have no idea if that’s all wider than a standard hub + cassette) and is there anywhere you could easily mount the gubbins you need to fit the callipers?

[bakerstreet]

Wouldn't it be easier to just go and buy a disc brake fork. I'm sure I've seen separate CX forks being sold on the net.

[markoc]

Why not look to a hydraulic rim brake (though I'm guessing to get the brake itself away from the road crap) I think Magura do a CX one and having run them on a number MTB's they are both powerful (enough to flex seat stays even with brace) and good for those who are a bit lazy in the maintenance department. I found my maguras to be very good, even when covered in dirty great chunks of countryside so road grime wouldn't be a biggie.

Your frame wasn't designed for discs and the stresses they exert particularly if you are using the seatstay/chainstay to mount the caliper via an aftermarket bolt on widget.

[yellowjack]

donfisher said:

...Hydraulic disc brakes are clearly what to move to. Until someone offers a reasonably priced hydraulic system at all groupset prices then I wonder if for those awful wet-through journeys you’d be better off just using a different bike...

Shimano will have a hydraulic disc brake option on 5800 (105) groupsets next year. Some of the bike brands have 2015 105/hydraulic brake builds in their catalogues already. Integrated hydraulic road bike discs are here already.

[Kell]

For a while I had a Pro-Flex with rim hydraulic brakes. They're very good when your wheels are true, but discs certainly allow you to let the rims get a little out of shape.

[Jayfish]

You also wish to consider how deep the dropouts are, the extra breaking force could quite easily rotate a QR out of a shallow one if not done up tight enough.

[jamiebae]

I have Avid BB7 cable discs and they feel a lot more powerful than rim brakes, as well as being much easier to modulate. I'm tempted to upgrade to HY/RD callipers though, as I run SRAM Force 10 speed so I'm not sure they'll do a compatible set of hydraulic levers, and if they do I'm sure they'll cost a fortune.