Which new MonsterCross option ??? FINISHED :-)

[MichaelB]

The issue with the SRAM cranks is that the axles aren’t long enough to fit the BSA shell with outboard bearings. And not really interested in the GXP setup

Good idea though

[MichaelB]

OK, some build details and questions !!

Proposed build spec ;
Frame : GT Xizang 9r Ti frame
Cranks : see below - likely GRX600 46/30 w 11-40 cassette (11sp) - have option of s/h Rotor 3D30 compact
Wheels : Hope/Stans Crest & Mavic Crossroc wheelsets
Tyres : Initially what is already fitted (Maxxis Crossmark II 29x2.25 on one set)
Shifters : Shimano R7020
FD : Shimano FD-CX70
RD : Shimano RX800
Handlebars : Shimano Discover Med Flare


1st question is related to the cranks. The ideal would be something like the Shimano GRX600 46/30 crank which I can get from Fleabay for $220 delivered (the GRX810-2 is $360 for a 100g saving). Big advantage is there are many suppliers of rings for the Shimano cranks
Other options include the Praxis Alba (48/32), but requires their BB and tools, and the rings are proprietry and exxy. Others like Easton, Rotor etc are exxy to start with and again have proprietry mountings.
Have spotted a Rotor 3D30 crankset for reasonable price. Means though that I'd run the 34/46 setup I have now, and not get the super low gearing. BB and replacement rings are easy, as it's 5x110.

Anyone know of other affordable sub-compact crank options ?

[caneye]

FSA?

https://www.amazon.com.au/FSA-Gossamer- ... B07LBHSSLQ

https://www.this link is broken/au/ ... gJt1PD_BwE

[caneye]

which fork are you going with? still the Lefty?

[MichaelB]

FSA?

https://www.amazon.com.au/FSA-Gossamer- ... B07LBHSSLQ

https://www.this link is broken/au/ ... gJt1PD_BwE

Cheers - the FSA option is one I looked at, but the proprietary nature of the chainring bolts and inner ring mounting (keeping the 110 BCD) make them expensive. Weight is a bit less than the GRX600, but another $80. The BB required is also a bit more.

The Amazon one is 1,100g !! So whilst cheap, a bit too heavy.

One option I’m thinking about is a lightly used 3D30 Rotor crank. With a Tripeak BB, adds up to <$200, and a decent weight.

Anyway, yes, still with a Lefty - a Carbon Speed PBR with 110mm travel.

Frame arrived today

[10speedsemiracer]

How about one of the Shimano cx50 cranksets ?



Just occurred to me, haven't checked things like chainline, Q or much else.

46-36t, 800gms and around $170, but I don't know if 36t is low enough for you and also wasn't sure if you were doing 10s or 11s ?

[MichaelB]

Cheers, that and the CX70 version are options and have seen them around.

Currently running 34/46 and 11-40 gearing with the 27.5” and 42mm tyres. So thinking about it, probably need to go the 30T small on the front.


Thought though that I had last night re the Shimano options is that the BB on the GT will probably be 73mm wide (will check tonight), so will the Shimano cranks like the GRX fit ??? Or do I need to go with Shimano MTB cranks if I use the Shimano/ Outboard type ?

[baabaa]

Thought though that I had last night re the Shimano options is that the BB on the GT will probably be 73mm wide (will check tonight), so will the Shimano cranks like the GRX fit ??? Or do I need to go with Shimano MTB cranks if I use the Shimano/ Outboard type ?

Was thinking this but thought best to wait till you had the frame in paw.
Maybe 68/73mm bb shell?
Anyway you kinda need to work around this as I have run 10 speed ( yes... cx50 cranks, cx 70 FD and hope 68/73 bb with a hope rear 11 sp hub with a slx 11/34 cluster) road gear on a drop bar salsa el mari but with a EBB which allow the shift of the bb in and out to improve the chain line and to a lesser point the front shifting.
I gave up as the fiddling drove me crazy and this bike was bought to be a ss so it remains a ss. Not sure if it helps I did find running a Stylo GXP crankset seemed to work better than any of the road or cx cranks I tried. Guess it comes down to things like cs length and the space between the inner ring and frame and also the chain and the tyre width you wish to use.
My tip is try to find what other bits peoples ran at the time the frame came out and use that as a base to get yourself up and running then you can start to hack around with options.

[MichaelB]

Cheers baabaa. Bike was setup with MTB cranks previously.
Have picked up the frame, so will measure today sometime. I know the BB386 cranks will be fine (like the FSA linked above), it's just trying to understand the Shimano requirements and differences between the Road & MTB world.

Bit of Shimano Techdoc research and googling tonight !!

[MichaelB]

Bugger

Per Shimano Product info for GRX cranks, only fits 68 & 70mm BB Shells

Will measure the BB shell after this meeting

[MichaelB]

BB shell width confirmed as 73mm.

PFBB.

That makes life interesting ...

Here is Rotor's crank compatability chart which confirms Duck's feedback that even BB386 cranks don't work

[Duck!]

Maybe 68/73mm bb shell?

No such beast as a 68/73mm shell, it's one or the other. Some bottom bracket assemblies are compatible with both sizes by means of adding or removing spacers.

[MichaelB]

Who woulda thunk that all this trouble due to a lousy 5mm [sigh]

The suggested Tiagra 4703 route from Duck! Will end up costing about $340 with BB. The MTB versions may be a bit less, but the flip side is the cassettes will be smaller & cheaper.

The loss of top speed is a minor factor that I think I can live with, or may just have to !!

[baabaa]

No such beast as a 68/73mm shell, it's one or the other. Some bottom bracket assemblies are compatible with both sizes by means of adding or removing spacers.

Well I agree I should have typed 68, 73 or even better 68 or 73 shell but for good order I did check and just quoted directly from the pack that my hope bb came as which reads...
HOPE BB MTN-SILVER-68/73MM SHELL
I guessed most people know if they have 68mm or a 73mm shell width

[MichaelB]

May have reached a potential solution following confirmation from Duck!.

At SJS Cycles, have found some 40T and one 46T outer for 96PCD outer chainrings (Shimano) that may give me a palatable combination like 40/26 or 46/28 on a M8000 XT or M7000 SLX crankset.

Standby to standby.

That's then team up with a 11-34 or 11-36 cassette.

[Duck!]

18T jump on 46/28 will exceed the capacity of any 2x front derailleur, and will run awfully on a 3x model.

[MichaelB]

18T jump on 46/28 will exceed the capacity of any 2x front derailleur, and will run awfully on a 3x model.

True - was sorta hoping I could find a 30/32 inner 64PCD chainring that isn't 1x.

So will the 40T chainrings in the 'Shimano Compatibility notes' thread fit ? I presume they will.

If so, that's probably my solution, unless I can find a 42T 96PCD outer chainring

[Duck!]

If going the MTB/"Trekking" crank route I reckon you'd be better looking for a model with a 104mm BCD, you'll have a much better range of ring options; something like the T4060 Alivio for a starting reference, but there are others.

[MichaelB]

Part of the reason I'm looking at the MTB 2x setup is that I can get the crank (new) for $130 (M7000) and a 40T outer chainring for less than $100, and safe in the knowledge that there will be no frame clearance issues. If I get precioyus, I can get the XT crank for $195 or the XTR for $230, but unlikley.

I've had a look for some of the 104BCD options, and they are either more expensive or just not around. e.g., the M780 with a 42 outer just isn't around.

So whilst there are options, some aren't available

[MichaelB]

Progress update :
Ordered/On Way :
Lefty Fork (Carbon DLR PB 110mm travel) and Hope/Stans wheelset arrived
M7120 4 pot calipers and hoses ordered
XT BB ordered
FD-CX70 ordered
Handlebars from mate snaffled
M775 crank arms on way from Duck!


To order : Next pay ...
42/32 (& 28) chainrings & bolts from Gambacicli
Project 321 Steerer adaptor
31.6mm seatpost, zero setback
Saddle
105 Mid cage RD (so I can swap RX800 from Slate

[owly]

See you've already locked in some components.

Had another think about options. RaceFace spindle of the correct length, run with Easton EA90 crank arms. RaceFace 2x 104/64 spider. TA Chinook rings. Wolftooth chainring bolts. I think the Easton crank would have a narrower q-factor than Shimano MT, so could run into clearance issues there on that frame.

Putting forward a saddle option you may be able to check out in a Trek Shop. Bontrager Arvada. Quite a bit of flex in it, which may help a bit with rougher surfaces. Seem to come on some Domane models.

[MichaelB]

Cheers Owly, the Easton option was mentioned on WW Forum, and there are two axle options that would even work with the Cannondale cranks (and Wiggle had an axle for A$95), so may still be an option, but your list of goodies is probably 7 or 8x what it'll cost me compared to the option I'm currently using.
So by this Raceface compatibility chart, if I use the RF131BM spindle for the 73mm BSA, I get a 47mm chainline for a 2x104/64 spider, or with the RF134, I get a 49.5mm chainline.

As a comparison, the M7000/8000 cranks have a 48.8mm chainline.


I have no idea what that looks like with clearances (rings), Q-Factor or arm clearances would be. I'd also need a more expensive BB (extra $40 due to 30mm axle).

Cranks (thanks Duck!), chainrings and BB total $145 atm, so that'll work for me to start.

Key thing though is the ratios due to the change in tyre size mean that the 42/28 should keep the low ratio similar, but only lose a bit on the top end. Meh, it'll do.

For now

[MichaelB]

It's started

[MichaelB]

OK, so seatpost choice.

Have two good options at the moment

#1 - Thomson Elite alloy, new for $70 delivered (normally $110 off websites)

#2 - Truvativ Noir Carbon Fibre, used, can get delivered similar price


Which one ?

[caneye]

frame looks in great nick. has it even been used??

seat post .. weight?
do you have a colour scheme you are strying to stick to?
matchy matchy chrome .. or chrome-black contrast?

any thoughts on tyres?