We’ve created this fit and f.a.q. page to help you determine whether a G2-style guide will fit your bike and to address some frequently asked questions.
What kind of cranks are the G2 guides compatible with?
The G2s are compatible with a wide variety of cranks from several different brands. They work best with single-ring specific cranks and triple-cranks with the chainring mounted in the “middle” ring position. Chainline should be around 51mm for 68/73mm shells and 57mm for 83mm shells.
Are the G2s compatible with a bash guard?
The G2 guides are not designed to work with a crank mounted bashguard, the patented integrated skid serves to protect the chainring from damage. If you’d like to use a bashguard, consider our S4.
What size G2 should I get?
We offer two sizes of the G2 steel and three sizes of the G2sl. The G2 Steel and G2sl come in standard size for 36-40t chainrings and “Mini” size for 32-36t chainrings. There is an additional size for the G2sl called the “Micro”, it’s designed for 28-32t rings (but incompatible with 104mm BCD cranks without modification).
What mount (ISCG, ISCG-05, or BB) should I get?
Which mount version is appropriate depends on the frame you’re using. If your frame has three threaded holes around the drive-side of the bottom bracket shell it is likely that it features ISCG or ISCG-05 tabs. Information about the ISCG standard (including dimensions) can be found here. If your farme features ISCG or ISCG-05 tabs we highly recommend you choose a matching G2 instead of the BB mount. Guides that mount to tabs are superior in functionality to BB mounted guides in that they resist rotation better when struck and offer more adjustability/fine tuning for fit. If your frame has no ISCG or ISCG-05 tabs and features a traditional thread-in bottom bracket shell you can use our BB mount versions (G2sl only). Our BB mount versions work best with external style bottom brackets (Shimano Hollowtech 2, Race Face X-Type, SRAM/Truvativ GXP, FSA/Gravity MegaEXO, etc.), while they can be used with cartridge-style BB’s you’ll need one that’s E-Type front derailleur compatible and potentially a different spindle length. Do not use ISCG adapter rings with the G2 series of guides (you technically can, but it’ll be very difficult to setup).
Does the BB-mount work on SRAM/Truvativ GXP cranks?
Yes. Even if there are no spacers installed on your BB. On a 68mm shell the BB mount guide should be installed between the drive-side spacer and the BB cup. On a 73mm shell the guide should be installed between the BB shell and BB cup.
I have a pressed-in style BB, can I use the a G2?
Only if your frame features ISCG or ISCG-05 tabs, the BB mounted version requires a thread-in style BB. Some popular frames from Giant and Trek unfortunately have no way of mounting a G2 guide.
My frame has ISCG03 (or ISCG-OLD) tabs, what are those?
ISCG03 and ISCG-OLD are both unofficial names for standard ISCG (ie not ISCG-05) tabs.
Will the G2 fit my Niner full-suspension frame?
No. The CVA suspension design interferes with the clocking of the guide and the skid. However, the Lopes guide usually works.
Will the G2 guides fit my VPP bike?
The standard G2 guides (36-40t versions) fit most VPP frame designs just fine. We make a special version of the Mini G2sl called the “Medium-angle” that is better suited to the chainstay positioning of VPP (and similar) frames. The Medium-angle is offered in BB and ISCG-05 mounting only.
How much drag does the guide add to the drivetrain?
It’s hard to quantify given so many variables in setups. But, we can wholeheartedly say “not much”. The pulley rolls on sealed bearings and there is reduced surface area contact between the chain and pulley vs. a roller design, so the setup moves pretty freely. It’s infinitely more efficient than a dropped chain, that’s for sure.
