Hi all,

i have a fat fat bike that I’m converting to singlespeed, standard threaded bb cups with a 100mm Sram gxp 1400 crankset.

The problem I’ve ran in to is the 30t chain ring is fouling on the chain stay. I’ve put a temporary plastic 2.5mm spacer on the spindle to see if it clears and it does with about 2mm gap.

My question is this, if I remove the spider and fit a standard non boost direct mount ring will it sit further away from the chainstay? I assume so as I’m ditching the thickness of the spider right?

thanks

Spacer on the BB cup to space the chainring out a bit?

My question is this, if I remove the spider and fit a standard non boost direct mount ring will it sit further away from the chainstay? I assume so as I’m ditching the thickness of the spider right?

The direct mounts will match the spider so a Boost Direct will be the same as a Boost Spider mount – otherwise you are into a compatibility nightmare

What was the crank on previously and what ring size?

Is the axel width correct for the Fat Bike – 177 vs 197 rear end

A GXP crank cannot be spaced outwards (assuming no spacers under the NDS BB cup), because the alignment is determined only by the NDS bearing position.

If you already have a Boost spider, then there isn’t much to do; if it is a regular spider, you could either get a Boost one or a Boost chainring. Another option would be to use a 2x spider or crank (i.e. NSB one) that allows the chainring to be mounted on the outside of the tabs, maybe with some additional spacers underneath.

Another option might be to mount th ering backwards – you can do that with Raceface rings… I suspect it might not work with SRAM

Damn it! Thanks guys for all the responses, the cranks are brand new and are non boost 170 rear specific which is what my frame is.

i think I may have to go 2x spider and fit it on the outside?

Hi guys, would this work?

https://rover.ebay.com/rover/0/0/0?mpre=https%3A%2F%2Fwww.ebay.co.uk%2Fulk%2Fitm%2F292739461560

Yes, but the BCD is different, so you will also need another chainring.

The simplest option would be a direct mount Boost chainring (e.g. cheaper steelie for testing https://www.amazon.co.uk/Sram-Direct-Offset-11-6218-027-020-Chain-Standard/dp/B073GVSW42 ), which will be 3mm further outboard than your current setup.

^ As above get a DM boost steel ring, cheap as chips, last forever. Job Jobbed.

Thanks, now I’m seriously confused! I thought a boost 3mm offset pushed the ring further towards the bike?

These are the cranks I have.

Cranks/BB's/Chainrings

Boost pulls the ring 3mm outwards to match the wider rear end.

Standard offset is 6mm, so the 3mm moves it out. Unless of course you have a 0 offset mount. That would be written somewhere on the spider.

I’m pretty sure it’s a zero offset, it’s not stamped anywhere on the ring, so assuming it’s a zero offset do I get a 6mm or a 3mm offset dm ring? Aaaaaaaah!

The offset is by the spider not the ring, so you need to look on the spider for any markings that say boost/3mm/6mm/etc.

Assuming for a second its a standard 6 mm non boost offset spider then your best bet is a 3mm boost DM ring.

Righty then Ben, no markings on the spider whatsoever! To me it looks completely flat so am I right to assume the spider is non boost and zero offset?

if so then I simply need a boost dm ring that will bring it 3mm closer to the drive side crank arm?

If the spider is indeed zero offset, it would be already as further outboard as it can be (another 3mm over Boost). Apparently there are also 0 offset DM chainrings, which I didn’t know about until a few minutes ago: https://www.bike24.com/p2122530.html