ROTOR REX 1.1 en QX1

[Ced]

Can anyone confirm, that the QX1 rings would fit on the Sram XX1 gpx crank with swapping the spider



I would like to do this, since my new fram is a bb92 or gpx.
If i would put in the Rex1.1, 30mm axle it will leave me with a PF4130, which does not give a lot of bearing strength.........

What are your opinions ?

[Ced]

pic above comes from rotor site ........

http://www.rotorbike.com/products/mtb/qx1_49

[Ced]

this way; it should also fit on a Race Face Next SL in my opinion .......

[dwaharvey]

Rotor are certainly making a spider to attach the QX1 to a SRAM crank, but I'm not sure they're available yet. Also, it's not clear if the spider is meant to give proper chainline for the BB30 XX1 crank, or the GXP model. The photo you posted shows a BB30 drive-side arm: if designed to give 49mm chainline on the BB30 model, the chainline will be wider on the GXP model... but perhaps still functional.

What makes you say it would work on the new Raceface crank? Certainly a spider could be made, but I don't believe any is being produced (the RF has a new proprietary spline pattern)

[Ced]

so, since you seem to have some knowledge around cranks and stuff.......

What would be the best/ lightest crank with a GXP or BB92 setup, but running a QX1 ring ?

[dwaharvey]

I don't think there's a great answer sadly: all the options have downsides.

Rex crank 1.1: Claimed weight 489g without chainring or BB... also says chainline is 56mm which seems crazy wide (SRAM is 49mm) and might affect shifting if it's correct.

Sram spider: not clear if it's going to give proper chainline with the GXP crank, or wider (designed for BB30)... and given the stated chainline above... wider might really be too wide. Weight of 175mm GXP with XX1 spider (no ring or BB) is 520g (based on one I had) and I'd expect the QX1 spider to be similar to the XX1 in terms of weight. So that's a little heavier than the Rex option.

Specialized spider: Sworks crank has 30mm spindle and won't work on BB92 without you getting a custom axle Hirth spacer to widen it a little bit (hard to find and possibly expensive). It's a bit of a hack to get it to work, and again the chainline would be around 2mm wider than intended by Rotor because of the axle spacer, but this would definitely be the lightest option. I think you'd be looking at around 415g. You could also use the spider on a Lightning crank, but some people don't like the way those look, they're expensive, and the chainline would again be a little wider than Rotor

Other options would all require you to get a custom spider made. This is actually a route that I'm pursuing although my BB is different (73mm BSA):
Hollowgram SiSL/SiSL2: needs lipless spindle (available from R2-bike), plus custom spider (trying to get Experimental prototype to make one for me)
RaceFace Cinch: needs custom spider, but otherwise would work as is. But availability on these is still somewhat lacking, and since the system is so new, getting a custom spider made for it is going to be harder (Hollowgram has been around long enough to make it easier)

Either of the above is going to be pretty competitive with the Specialized weight (think they'll all be within 10g of each other). They're a hassle, but you could make sure the chainline is what you want.

Pretty much any really light weight setup is going to use a 30mm spindle which I know you said you don't want to do. But maybe it's something you should reconsider in conjunction with a new Race Face BB (should work with any 30mm crank with appropriate spacers I should think)... I read this comment on a pinkbike review of the cranks that addresses your concerns:
"Since the Next SL cranks have a 30mm spindle, in order to make them compatible with bikes that use Press Fit 92 bottom brackets a bearing with an outer lip is pressed directly into the frame. Eliminating the retaining cups allowed Race Face to use the same size bearings as are found in a 24mm spindled set up."

In that case the easiest light setup is Lightning crank (with Specialized QX1 spider) and RaceFace BB. Next is the Rotor crank itself. Anything lighter than Rotor (other than Lightning) requires you to pursue a custom spider.

[Ced]

Hey dwaharvey,

Your answer some sort blew me of my chair ;o)
Thanks for the over detailed answer ........


mmm, don't know what to do know.

Should I first find out what the Sram XX1 GXP with QX1 spider results in ?

The lightning crak for 800 eur is over the top at this moment.
The rotor crank Rex1 with the new Race Face BB

(should work with any 30mm crank with appropriate spacers.).....

I will give it a thought...........


Thanks !!!

[dwaharvey]

Last night I installed a Rotor QX1 on a friend's Sram XX1 GXP crankset (with the Rotor sram spider). I didn't get a chance to weigh it I'm afraid (though I believe it is actually ~10g lighter than the stock SRAM spider), but I can report that the chainline with the rotor ring on this crank is a wide 56mm. I'm wondering if this is Rotor hedging their bets and making a single Sram spider that could work on both the BB30 crank and the GXP (sram make one for each)? In any case, in some ways the wide chainline is good because the 34tooth ring is pretty big on it's long axis... equivalent to a 37 or so... and at the original Sram 49mm chainline I don't think it would have cleared. On the downside, the ring is pretty much aligned with the #3 (14tooth) cog in the rear, so when in the #11 (42) there's a fairly strong arc in the chain, that I fear might make a dropped chain more likely in the bigger rear cogs... will have to see how my friend fares with it. I'll report back when he has some time on it.

[Ced]

Hey a big thanks for your report !
I will go this way to start, so more than interested in your story regarding chain drops in the high gears. ?.....

[quantum_Rider]

Any idea would QX1 ring work with single speed setup? Rotor representative told the shape of QX1 ring is 2% more oval than their single speed specific Q-ring.

[Ced]

On the downside, the ring is pretty much aligned with the #3 (14tooth) cog in the rear, so when in the #11 (42) there's a fairly strong arc in the chain, that I fear might make a dropped chain more likely in the bigger rear cogs... will have to see how my friend fares with it. I'll report back when he has some time on it.

Any idea if your friends tried to mount the ring on the inner side of the spider instead of on the outer side ?
Just to get a better chainline ?
Or NO GO ?

[NS]

Just trying to fit a rex 1.1. to my C29 I have to say the Instructions are diabolical for use with their own BSA30 BB.

There is no info on what spacers to use, how many you can use on the drive side & NDS to achieve the correct q factor and chainline, where to set the ring for single chainring.

So does anyone know what spacers I should be using with the BSA BB to get a good chainline and to balance things on the NDS, I am conscious that there must be a minimum and maximum amount of spline that the crank must engage on?

I know a tape measure will solve the Q factor issue but there's only so many times I want to hammer the NDS crank on and off because the bearing/axle tolerances are that tight they are practically an interference fit.

[ben88]

NS. You'll need minimal spacers on the non drive side, perhaps just a clear washer. On the driveside try a 5mm spacer and a clear washer either side of that spacer. Pretty sure thats what we have on our Scott bikes. Good luck!

[johnnyboydotca]

I am running one on my GXP X01 crank. Running it normal widens the chainline another 6mm out. Not ideal in the lower gears but I guess it sort of works (but it is noisy and looks stressful in the lowest 3 gears). I ended up putting the ring on the inside of the spider and the chainline is back to normal. Running a 32T QX1 on a SRAM X01 Carbon crank on a Giant Trance Advanced SX bike.

[Ced]

I have the ring on the inside of the spider also now.
His vreates a much better line !!