Unique to Shimano M8000 crank, and going 1x11

[Sidmouth]

I bought a 2x M8000 crank, after 5 months bought a specific shimano single 30T and did the fit.

 

One issue the chainline is too much towards the small or 11 tooth, I need it to be lined up like 3-4mm towards the rear 40 Tooth, took all the spacers of the drive side crank axle and got it as close as possible to the BB without touching, it pedals but there is stress on the chain and freewheel when in the lowest gear.

 

I would think the Shimano single chainring would be designed to lean inwards shorting the chain line, I could put in spacers but then it would not be flush with the crank arm and chainring, any ideas or is this just 1x11

[robsc]

You should be able to add spacers between your spider and chainring . See http://www.kalbo.co.za/productsCS.html

[Sidmouth]

This works ok with any other cranks, the M8000 is different if you add a  spacer the chainring will sit off the crank, the crank be supported only by the bolts, I will send a photo in the AM

[JXV]

If you remove drive-side BB spacers to adjust chainline then they must be fitted under the non-drive side crank to keep correct BB width.

 

You can also use spacer washers between the crank spider and chainring but then your chainring will not sit flush.

 

The real problem is that Shimano has different chainlines on their 3x, 2x and 1x cranks.

FC-M8000-3 : 50mm

FC-M8000-2 : 48.8mm

FC-M8000-1 : 50.4mm

 

Chainline is measured to the centre of the middle ring on a 3x, centre of single ring on a 1x and midway between tooth centrelines of inner and outer rings on a 2x. This may help you to measure if you are in the ballpark. It also explains why you might need a spacer when fitting a 1x ring to 2x crank.

 

The fixing bolt lengths are also different for 3x,2x and 1x systems (M8x8.5mm, M8x9mm and M8x11.4mm respectively). If you fit spacers under your new 1x ring in order to correct chainline on a 2x crank then you might need longer bolts to ensure enough thread is engaged for durability .

[raptor-22]

Shoulda boughta SRAMa

[Mongoose!]

Shoulda boughta SRAMa

Jip, and it is comming with a 10 also...

[Sidmouth]

If you remove drive-side BB spacers to adjust chainline then they must be fitted under the non-drive side crank to keep correct BB width.

 

You can also use spacer washers between the crank spider and chainring but then your chainring will not sit flush.

 

The real problem is that Shimano has different chainlines on their 3x, 2x and 1x cranks.

FC-M8000-3 : 50mm

FC-M8000-2 : 48.8mm

FC-M8000-1 : 50.4mm

 

Chainline is measured to the centre of the middle ring on a 3x, centre of single ring on a 1x and midway between tooth centrelines of inner and outer rings on a 2x. This may help you to measure if you are in the ballpark. It also explains why you might need a spacer when fitting a 1x ring to 2x crank.

 

The fixing bolt lengths are also different for 3x,2x and 1x systems (M8x8.5mm, M8x9mm and M8x11.4mm respectively). If you fit spacers under your new 1x ring in order to correct chainline on a 2x crank then you might need longer bolts to ensure enough thread is engaged for durability .

Thanks JXV.

I have looked at the 2x and 1x M8000 crank, they look identical, what you do notice is that the 2x chainring, the 36, that those teeth are further out extending the chain-line, when you buy the Shimano 1x ring you do see that the ring has been engineered that the teeth fall further to the non drive side.

 

From a production point of view tooling up to make three different cranks would be expensive,i think the same happens with crank lengths, the cranks are all the same length ,they just drill the pedal hole further or lower down the arms.

So they just design the chain-rings differently on 1x 2x and 3x

 

I also think the rear wheel and the dishing can make a massive difference if they could build the spokes 3mm 4mm towards drive side it will help.

The spacers seems to be my only solution, but there will be a gap between the crank and chainring 

[Captain Fastbastard Mayhem]

Thanks JXV.

I have looked at the 2x and 1x M8000 crank, they look identical, what you do notice is that the 2x chainring, the 36, that those teeth are further out extending the chain-line, when you buy the Shimano 1x ring you do see that the ring has been engineered that the teeth fall further to the non drive side.

 

From a production point of view tooling up to make three different cranks would be expensive,i think the same happens with crank lengths, the cranks are all the same length ,they just drill the pedal hole further or lower down the arms.

So they just design the chain-rings differently on 1x 2x and 3x

 

I also think the rear wheel and the dishing can make a massive difference if they could build the spokes 3mm 4mm towards drive side it will help.

The spacers seems to be my only solution, but there will be a gap between the crank and chainring 

er, no. 

 

They are already tooled up to make at minimum 3 different cranks in each heirarchy, with different dimensions and mounting points. 3x crank has a different spider to the 2x crank, which has an entirely different spider to the 1x crank.

 

Only time they would tool-up for 2 cranks only is if they were Direct Mount cranks, which Shimano doesn't make.

 

They also tool up for different BB widths (68/73mm vs 83mm).

 

Shorter cranks are exactly that - shorter. Otherwise there wouldn't be any additional clearance at the cranks, which is the primary reason for choosing a shorter crank arm. "Just drilling lower" would also be a problem in all of the hollow cranks, as you would need to make the reinforced section far larger to accommodate a larger range of drilling positions.

 

The dishing has sweet FA to do with the chainline - it's entirely dependent on the position of the freehub, and your crank type. Every single hub will have the same chainline, if it is the same axle standard. Likewise, the chainline at the front is entirely dependent on the amount of rings at the front, and the axle width at the back. That's why BOOST standard bikes have cranks with a different chainline measurement than non-BOOST bikes. 

[Captain Fastbastard Mayhem]

As for the spacers, it's the best option. No lack of integrity in the system, as long as you torque to the correct level. A gap between the ring and the crank is not a deal-breaker. In fact, the 30t 104bcd rings have spacers machined into them in order to provide clearance from the crank spider, otherwise the chain would foul on the spider itself. 

[Sidmouth]

Thanks Guys

great info I'm narrowing it down.

 

Myles, I looked at the M8000 2x and 1x Cranks, I could not tell the difference, the 1x crank even have the holes for the second ring, you sure they different

[Captain Fastbastard Mayhem]

Thanks Guys

great info I'm narrowing it down.

 

Myles, I looked at the M8000 2x and 1x Cranks, I could not tell the difference, the 1x crank even have the holes for the second ring, you sure they different

No, sorry - on XT m8000 the 1x / 2x cranks are the same ie they share the same spider. 3x crank is a separate item entirely. 

 

So ito XT M8000, you're correct. But incorrect in that it doesn't apply to the triple, and the lengths are completely different - not just placement of the threads. 

[Sidmouth]

No, sorry - on XT m8000 the 1x / 2x cranks are the same ie they share the same spider. 3x crank is a separate item entirely. 

 

So ito XT M8000, you're correct. But incorrect in that it doesn't apply to the triple, and the lengths are completely different - not just placement of the threads. 

yip

[Sidmouth]

I found some 8mm washers at my local hardware, they are a bit big so I filed them down and will insert, they are only 1mm Thick, Im thinking maybe up two together to shorten the chain-line, but this sounds messy.

On the first photo without washers you can see that the washer will expose a gap

[Captain Fastbastard Mayhem]

Do it, it'll be fine as long as your bolts have enough purchase on the crank spider tabs. 

 

If they don't have enough purchase, you'll have to get longer bolts from your LBS. 

[raptor-22]

The cranks will just be shifter over to the non drive side to accommodate the chain line.

[Bobbo_SA]

Thanks JXV.

I have looked at the 2x and 1x M8000 crank, they look identical, what you do notice is that the 2x chainring, the 36, that those teeth are further out extending the chain-line, when you buy the Shimano 1x ring you do see that the ring has been engineered that the teeth fall further to the non drive side.

 

From a production point of view tooling up to make three different cranks would be expensive,i think the same happens with crank lengths, the cranks are all the same length ,they just drill the pedal hole further or lower down the arms.

So they just design the chain-rings differently on 1x 2x and 3x

 

I also think the rear wheel and the dishing can make a massive difference if they could build the spokes 3mm 4mm towards drive side it will help.

The spacers seems to be my only solution, but there will be a gap between the crank and chainring 

 

with a 30T on the 104BCD side you will most likely need the spacer / gap anyway else your chain will ride on the top of the crank spider anyway.

 

Edit: Too slow, that's what Myles said.