996

Building up my gravel bike with the Deore XT M8000 cranks for the lower 1x gearing options. The bottom bracket recommended with this crankset is the Shimano XT M800 BB which will need some spacers (included in BB package) with my 68MM BB shell.


How reliable are these spacers? They are plastic. Are there any metal options? Has anyone had any experience?


Thanks!

DorkDisk

The spacers are fine, the cups themselves have deeper threaded sections to compensate for the lack of shell. I think some were Al; some of mine in my pile of parts appear to be metallic and not steel.

Many, many people have run those on 68mm shells with the spacers for years, its normal. As you say, they come in the box just for this purpose.

996

Got it appreciate the response. I was thinking for reliability purposes finding metal versions of these spacers. We are torquing them down a decent amount - found that thought a bit weird with plastic spacers.

996

Also - another question I have... are these spacers mandatory when running a 1x setup with this crank? Thanks! DorkDisk

mack_turtle

the spacers are mandatory no matter what kind of drivetrain you are using to space the ends of the spindle correctly between the bearings. if you don't use spacers, you'll probably end up with play in the spindle.

theoretically, you could put all the spacers on one side or the other of the BB shell, so long as the effective width of the shell is corrected by the spacers. you probably would not want to do that because it would make the pedals laterally off-center and might make the clearance between the frame and the ends of the arms uneven, but it's possible.

the plastic spacers are fine. I've installed a lot of threaded external BB cups and the plastic spacers have never been known to break. if you put enough torque on the bearing cups to damage the plastic spacers, you've gone way overboard with the torque. Shimano's instructions are to grease the threads and then torque the cups to 35-50Nm. 50 is a lot. my experience, based on instructions from the Barnet's DX manual, is to use Loctite 242 and stop at 35Nm. that's more than enough, with the Loctite, to keep everything sealed up, and it won't come loose until you ask it to.

scubaman

As others have written, if you have a 68mm BSA threaded bottom bracket shell, you need to use spacers with the external bottom bracket cups to fit a Shimano MTB crank designed for a 73mm bottom bracket. If you got such spacers from Shimano with your bottom bracket, I’d think they’re fine to use. You should also be able to buy aluminum 2.5mm spacers separately for use with a BSA bottom bracket, like these: https://wheelsmfg.com/bottom-bracket...ack-alloy.html

Wattsup

Hmmm. I've had mine in for about 4500 miles with no problems yet. I'm about to winterize my bike and will be removing and regreasing the BB, so I'll be getting a closer look at the spacers soon. I didn't realize they were plastic to tell you the truth.

996

Wattsup wow that's awesome. Great news. Plz keep us updated (if you can). I went ahead with the M800 BB. Excited for the build.

DarKris

I have installed that crankset and bb on my Toughroad with a 68mm BB with metal spacers. I personally think the plastic spacers would deal with corrosion better IMO.

Toadmeister

Your LBS probably has spare metal spacers, just ask. That’s how I got mine.

shelbyfv

Definitely something to consider!