Sacrilege! (Disc brake on a Bacchetta CA 2.0)

[Hotdog]

While I love almost all aspects of my CA 2.0 one thing I was never really satisfied with was the front brakes. No matter how much I fiddled with it the X-Eyed single pivot calliper brake was never better than 'OK'. Fine for speed modulation but emergency braking or stopping on steep slopes needed some serious squeezing of the lever and in the wet things could get a bit dicey. I think the main cause is the 180 degree bend in the brake cable required by the bottom (reversed) cable entry. The rear brake, which has a fairly straight cable run, has always felt better than the spongy and weak front brake despite them using identical levers, cabling and callipers. I used high quality cables and tried both a big loop (avoiding sharp bends) and a small loop (avoiding excess cable length), and also tried a variety of pads. Nothing seemed to lift the brake performance above 'meh' so finally, after over a year of thinking about it, I have ditched the front calliper brake and installed a disc brake in its place.

Old photos of the bike before the change.

Mid changeover, old wheel, fork and brake system on the left, new wheel fork and brake system on the right (click for bigger):


After (click for bigger):




For the brake system itself I could have tried something lighter but having decided to go to all this effort I wanted the most effective brakes I could get. Based on good reviews I chose Shimano XT (XC MTB) hydraulic brakes and the matching Ice-Tec 160 mm rotors. I built the wheels up from HPlusSon Archetype rims (23 mm wide like HED C2, etc.), Sapim CX-ray spokes (28 front and rear, laced 2x) and Novatec hubs (F482SB rear, D711SB front) and the fork is an Evolution A647 from SJS Cycles.

The choice of fork was in a way the easiest decision because as far as I can tell it's practically the only choice! Most 700C wheel disc brake compatible forks currently available are cyclocross/trekking forks with a significantly longer axle to crown length which would lift up the front of the bike, change the head tube angle and (very slightly) alter the handling of the bike. Some disc compatible forks with standard road bike geometry have come onto the market (e.g. Enve Road Disc) but they are only made with tapered steerer tubes and the CA 2.0 frame only accepts a straight steerer. Ah, but Bacchetta themselves make disc compatible forks don't they? Well, yes, they do, but only in steel or aluminium and the current models have unsightly V-brake studs on them, it would be shame to put one of those on a CA 2.0... The Evolution A647 is the only disc compatible road bike geometry carbon fork with 1 1/8" straight steerer that I've been able to find.

Out of curiosity I did weigh the wheel + fork + brake + cable + lever that I took off the bike and the wheel + fork + brake + hose + lever that I put on the bike and I reckon I've made it approximately 500 g heavier as a result of the change. To put that in context that's less than 1/10th of the difference in weight between my CA 2.0 and my Giro, it's 4.5% of the weight of the bike or 0.5% of the bike + rider combined weight, in other words it's not worth caring about in the slightest.

As for how well they work, well, the brake is still bedding in and I suspect I haven't quite managed to bleed all of the air out of the system yet but even so they are already way better than the calliper brake was. The braking is far more powerful but still smooth and controllable. There might be some that would regard putting a disc brake on a light weight performance bike like a CA 2.0 to be an act of sacrilege but so far I'm very pleased with the result.

[Mulger bill]

...but so far I'm very pleased with the result.

Bottom line!

Nice work Hotdog and a good choice of hardware too.

Shaun

[jaffaman]

I'm with you. Performance isn't just about weight. It's about being able to do what you want when you want it and being able to trust your ride to keep up with you - IMHO discs are a no brainier. They do tend to be noisy, but aside from that, at least you will feel confident that you will stop when you want to, wet or dry.

Besides, I think they look good. And there is some brag value, at least until everyone has hydraulic disc. What more can you ask for?

[rdp_au]

Very nice setup Hotdog. Did you build the wheels yourself? Interesting to note a weight increase of only 500 g or so - your CA is still lighter than my Corsa, though! I'm sure it could be less with some of the lightweight components if you really wanted to spend the money.

My experience of the standard bacchetta brakes is similar to yours with the X-eyes, they're good enough but nothing special. I'm running Swisstop pads which work well enough, although they make all sorts of nasty scraping noises in the rain. Seems like the X-eyes don't gain you too much.

Your CA is turning into a very nice machine indeed. I'm impressed

[william]

Disk brakes on every bike. I love em.
I had a low racer with squealing disk and it drove me nuts but… That noise also attracted a lot of attention too. So much so a little jab on the brakes behind joggers or strollers with ear buds on the bike path had them jumping into the bushes in fright. I started to like it. I also modulated the brake riding downhill to a point I could almost play tunes with it whilst everyone around me looked to see what the hell was going on. A bit like when a Harley is in the traffic, you know its there even if you cannot see it but you just look around for it.
I eventually changed the disk rotor to a different brand and design and things went quiet.
I did have fun with the squealy one though.

[MichaelB]

Nice one

[Hotdog]

Thanks guys.

David, I did build the wheels myself. I've got some experience there, when I converted my Giro 26 to 700C wheels I built those too. It's not too difficult if you read some good instructions (I mostly used Sheldon Brown's) and take your time with it, and it's pretty satisfying when you're done. It was actually issues with a factory built wheel that prompted me to finally get going on this disc brake project, the HED Kermesse rear wheel on my CA 2.0 started breaking spokes at a rate of one a month! By the time of the third broken spoke (mid April) I already knew I was going to have either fully rebuild the wheel or replace it, and with the eventual disc brake conversion in mind I decided on the latter and started buying the parts to build both a replacement rear wheel and a matching disc compatible front wheel. Wheel building might not have been new to me but there were a couple of other aspects of the conversion that were, removing a fork crown race and installing hydraulic disc brakes.

I've got a pretty good selection of bike related tools but a crown race puller is one of the few I don't have, when it came to removing the crown race from the old fork so that I could install it on the new one I had to improvise. Fortunately the crown race had a chamfer on the lower surface (not all do) which made things easier and I was eventually able to release it by working my way around with a small hammer tapping a Stanley knife into the seam, then a small flat blade screwdriver, then a larger screwdriver. Once it was off the old fork installing the crown race on the new fork was easy as I do have a crown race setting tool.

I've had a bike with disc brakes for years (my Giro) but they were cable actuated (Avid BB5s originally, BB7s later), I'd never had any experience with hydraulic brakes. The installation and set up presented no real dramas though. The Shimano disc brakes are available as 'front' or 'rear' brake kits with either left or right hand levers, the only difference between the front and rear versions are the lengths of the pre-installed brake hose, 1 m for a 'front', 1.7 m for a 'rear'. For my front brake I bought a 'rear' brake kit (with RH lever) which ensured the pre-installed hose would be more than long enough despite my tall recumbent handlebars. I also bought a Shimano bleed kit (oil and a tube) and bleed tool (the plastic funnel thing that screws into the reservoir) as I knew I was going to have to cut the hose to length and some air was bound to get in to the system while doing that. The brake kit comes with a spare olive and barb for re-terminating the hose so I didn't have to buy any additional parts for that. For the most part all I had to do was follow the instructions supplied with the brake kit and the bleed kit. Getting the new barb into the end of the hose after cutting it to length was a bit tricky but I managed to get it in with no damage by (gently) holding the end of the hose in a pair of pliers and tapping the barb down with the flat of a clean headset spanner.

Regarding the calliper brakes supplied by Bacchetta, I think the only advantage of the X-Eyed brakes over the standard Bacchetta branded dual pivot calliper is that the X-Eyed are a bit lighter. I very much doubt that they're any more effective, in fact for the single pivot type that I have I suspect the reverse is true. I notice that the standard spec for the CA 2.0 now lists double pivot X-Eyed callipers instead of the single pivot version that used to be standard, that's probably an acknowledgement that the single pivot X-Eyed callipers weren't great. At the very least getting and keeping them centred with respect to the wheel rim has always been difficult.

[RazzFazz3HT]

Hello Hotdog and all other,

I found this thread by searching for an DISC-Fork for my M5 Carbon Highracer.
First of all let me Introduce myself: My Name is René and I am from Germany. I own several recumbents and I do longdistance trips which we call Brevet or Audax.

I write here because i wasnt able to make a privat mail to Hotdog.

I am interested in the Evolution A647 Fork for my M5CHR because this fork seem to be very narrow at the area where at Standard forks a Caliper Brake takes place. It must be very narrow, because it need some clearance for the chain at my bike . A CrossCountry-Fork doesnt work.
Unfortunatley I didnt find any fotos where the fork ist displayed directly from the front.
Hotdog can you please make such a foto , so i can measure the width of the fork.

2.5cm below the lower bearing the fork hast to be smaller than 8cm.

Thank for your help!

Bye
René