CX Disc Build by a cx/road newbie

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atonik
Posts: 30
Joined: Fri Jul 18, 2014 11:46 am

by atonik

Hi,

I'm about to do a CX build on a budget and my knowledge of road/cx is non existent. Therefore I need your help.

My plan is to use the following:

  • SISL2 cranks
  • 6770 Di2 shifters
  • medium cage 6870 rd
  • 1x11 setup
  • brakes?
  • frameset?

Now, things I need help with:

Wheel set - I have a spare Tune Prince 32h QR hub and am wondering if that in conjunction with some extralite 24h front hub can be a base for a solid wheelset? Rims would probably be http://www.light-bicycle.com/wider-700c-38mm-tubular-rims-for-cyclo-cross-road-bicycle.html would these suffice?
Frame set - I'd like a frame(size 54 as I'm 175cm) that has internal cable routing and that it has BB30 as I have the cranks already. Frame set shouldn't surpass $1000 (used is ok).
Brakes - TRP HYRD or something other?

Weight - as I'm not familiar with road peripherals, weights of brakes/levers etc, I'm not sure how low I can go with this setup. I'd like to keep it in low 7kg if possible.

Thanks for your time and I appreciate any help.

wrenegade
Posts: 128
Joined: Mon Apr 28, 2014 4:36 pm
Location: Vancouver, BC

by wrenegade

With Di2 and SiSL2 cranks it would be a shame to pair that to a lower-end frame in my opinion, and most of the higher-end frames now are moving or have moved to thru-axles haven't they? Obviously a SuperX frame comes to mind with SiSL2 cranks (and they are still QR). Possibly an 2014 older Mares frame (newer ones are thru-axle only) or Specialized Crux would be another (maybe used), I'm not sure if they all 100% thru-axle now or not.

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pushstart
Posts: 461
Joined: Sat Jun 16, 2012 3:12 am

by pushstart

Generally disc wheelsets have same spoke count front & rear. Most braking forces are in front and disc brakes are hard on wheels/spokes. I would do 28/28 for CX (or 32/32 if you want more meat), you could probably get away with 24/24 though for wheels that you weren't going to ride on singletrack.

Why not do the shimano di2 hydro brifters? Shimano hydro gets rave reviews. (I am too lazy to refresh my memory on the part number.) If you must stick with mechanical, the TRP Spyre brakes are solid (and light). The Hy/Rd are apparently nice too, though heavy and pricey.

If I were building a disc-brake bike of any flavor I would definitely opt for a thru-axle fork. Less of an issue in the rear, esp with 140mm rotors, but the consistent rotor placement in front is really, really nice -- if you ever remove the front wheel. (Probably 12mm thru-axle as that seems to be the direction folks are heading? )

I have a 15mm thru-axle fork on my (disc) road bike but and a QR 9mm "thru-bolt" on my commuter/CX bike; the road bike is a lot nicer for changing wheels, but unfortunately the CX/commuter gets wheel changes the most frequently.

+1 on 1x setup. I am running 1x10 with a clutch X9 RD, 11-36t cassette and 46t X-SYNC ring up front. It is great. You should be OK without a clutch RD; I opted for that because I wanted a quieter setup in the woods and also extra insurance against dropping a chain on singletrack.

atonik
Posts: 30
Joined: Fri Jul 18, 2014 11:46 am

by atonik

@wrenegade If I'm understanding correctly both Crux and Mares are BB30 and can have SISL2 on? SuperX was my first choice to look up but as far as I've seen, it doesn't have internal cable routing.

Regarding rear hub, I'm not fixed on it. Option is to sell it and get an appropriate hub so I guess the frame set will dictate which ones I'll have to get. 28/28 seems OK so I can go with that, yeah.

@pushstart Pardon my ignorance as I'm a bit confused about shifters/brakes. I wanted to get 6770 shifters as they are compatible with 6870 RD but.. If I decide to get R785 brakes I see that levers come with it. Does that mean that I don't need 6770 shifters as I get shifters with R785 or that's completely separate thing or.. how does it work :(

About drivetrain, I was thinking of 11-32 cassette (I'm not sure if 11-36 would work with 6870) and would probably order two direct mount chainrings from garbaruk. One for climbing as there is this climbing path that I'm trying to improve my time on, and one for everything else.

To summarize; options are crux/mares

Thanks to both of you

jooo
Posts: 1510
Joined: Wed Feb 02, 2011 3:48 am

by jooo

If you do want to use the Tune hub on a thru axle frame, you shouldn't have many problems tracking down a conversion kit.

pushstart
Posts: 461
Joined: Sat Jun 16, 2012 3:12 am

by pushstart

atonik wrote:
@pushstart Pardon my ignorance as I'm a bit confused about shifters/brakes. I wanted to get 6770 shifters as they are compatible with 6870 RD but.. If I decide to get R785 brakes I see that levers come with it. Does that mean that I don't need 6770 shifters as I get shifters with R785 or that's completely separate thing or.. how does it work :(


Yes, I think you understand. The R785 replaces your levers completely (and your brakes).

That is the setup I dream of for my road bike. Di2 + hydro = perfect.

wrenegade
Posts: 128
Joined: Mon Apr 28, 2014 4:36 pm
Location: Vancouver, BC

by wrenegade

Yep, both the Mares and Crux are BB30.

If you still want to use the 6770 shiftings you'll have use canti brakes, otherwise you're going to need to replace the shifters. Nothing wrong with cantis per sea, but having moved from a 2012 Mares CX with cantis and QRs to a 2015 with hydro discs and thru-axles, I LOVE the change (even though the new bike with dics is a bit heavier).

Problem is I think a thru-axle Crux or Mares CX frame is going to be more than $1000. Perhaps a Mares AX frameset is available (the aluminum Crux is still QR).

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FIJIGabe
Posts: 2241
Joined: Tue Sep 11, 2012 6:07 pm
Location: The Lone Star State

by FIJIGabe

I was in much the same boat as you when I put together a "budget" build on my Crockett (road cyclist building a CX bike). Here are some of the things that I've learned:

Brakes: disc will definitely stop better than canti, but don't be afraid of using mechanical disc (Spyre's are GREAT). If you've got a groupset you want to use, just go with mechanical until you can build up the resources to get hydro brakes.

Wheels: if you're going to order Chinese rims, just go ahead and order the complete wheel (28h/28h). The hubs you've got are pretty pricey, and selling them might net you enough to buy two sets of wheels (which you can use for different types of terrain). You definitely want two sets of wheels, especially when the weather starts getting ugly.

QR vs. Thru-Axle: don't be scared of QR. Sure, it isn't the new technology, but QR is reliable, and can be made almost as stiff as Thru, if you buy the right gear. I originally used QR skewers on my wheels, and they worked. I'm a big guy, and would occasionally hear my rotors rubbing against the brake pad, and just chalked it up to my size and the inherent deficiencies of QR. However, after hearing some advice (and a podcast or two), I decided to give the DT Swiss RWS skewers a shot. When torqued down, I get no deflection of the wheel/rotor. No noise, whatsoever.

Good luck and let us know what you decide!

pushstart
Posts: 461
Joined: Sat Jun 16, 2012 3:12 am

by pushstart

Agreed that if you already have shifters, just get some Spyres (they are not bad at all; I use them on my road and CX bikes). I suggest replacing the TRP rotors, though; they shudder and don't stop nearly as well as other (e.g. Avid HSX) rotors.

The value in the thru-axle is really consistently wheel placement. Swapping wheels with QR is likely to result in slight misalign and rotor rub. It's an annoyance, but not really the end of the world.

I too run RWS thru-bolt on my QR (CX) bike. I don't know how much stiffer they really are, but they almost eliminate rotor rub from side-to-side flex. Seem better than QR. Not as stiff as my 15mm thru-axle, though. (The RWS thru-bolt does nothing to help with consistent rotor placement.) But nothing wrong with QR; it works fine.

Personally I would also consider a Chinese carbon thru-axle, BSA frameset if budget was a top concern.

atonik
Posts: 30
Joined: Fri Jul 18, 2014 11:46 am

by atonik

@jooo Yes, I'm aware. One option would be that and the other would be to sell and get something else. Will see what will turn out to be a better money wise option.

@pushstart Thanks, that explains a thing or two. I don't have the shifters, just direction I was going for but you guys pointed me towards hydros. Chinese frame, I was always interested in those but I'm not sure which one is the one to get and it would be considered up to par with brand name frames. The only two I know of are dengfu fm059 and this miracle. If they are good enough and can be trusted then it would fit the bill and I could get a custom paint job which is a win all around.

@wrenegade Thanks, I'm already looking at those two

@FIJIGabe Thanks. General opinion is to go with hydros so I'll just do that. Would you mind clarifying a bit two sets of wheels. What would be the difference between them and what terrain/type of drive would each be suitable for?

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FIJIGabe
Posts: 2241
Joined: Tue Sep 11, 2012 6:07 pm
Location: The Lone Star State

by FIJIGabe

I just meant that you could probably sell those hubs and buy the wheels at no cost to yourself (if you choose one), and maybe even buy two sets of wheels at little cost.

pushstart
Posts: 461
Joined: Sat Jun 16, 2012 3:12 am

by pushstart

I believe both Dengfu and Miracle are made by Flybike factory. The quality/attention to detail will probably be below that of a major brand, but obviously prices are very good. I have had two Hongfu disc road bikes (the first didn't fit as well as I hoped) and ~5k miles without issue. They are nice frames. I have always stuck with BSA to avoid creaking BBs.

Anyway, there is always a little risk there, but it is worth considering if there is a model that fits you well. My ti frame seems like it will last forever, but if it does ever break I will probably get one of those.

Good luck with the build!

atonik
Posts: 30
Joined: Fri Jul 18, 2014 11:46 am

by atonik

Thanks to everyone for suggestions.

I ended up with something rather different than I have planned. As I've had some parts from previous build I've decided to build it with the following:

X01 10-42 cassette - probaby will get Ari 39T cog and replace 42T
KMC X11SL chain
SISL2 cranks with garbaruk 42T direct mount ring
R785 shifters/brakes (comparing to MTB setup, those are HEAVY @769g w/o brake hose)
M9050 RD
LTK027 frame
I'll reuse my wheel set from previous build

I'm still debating whether to use junction A or display to connect everything. Anyhow, this is what I have at the moment and will get the rest of the parts in the upcoming month.

atonik
Posts: 30
Joined: Fri Jul 18, 2014 11:46 am

by atonik

I am a bit confused about wiring this.

I've decided to use display SC-M9050 which has 3 ports.

Two cables from R785 will occupy two slots of SC-M9050, 3rd slot will have a cable going to SM-JC41 (junction B which has 2 slots on each side) where I'll connect battery and RD.

Is that how it's supposed to be done or am I missing something?

Thanks

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FIJIGabe
Posts: 2241
Joined: Tue Sep 11, 2012 6:07 pm
Location: The Lone Star State

by FIJIGabe

No, that's the way it works.

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