Boost crank or not boost crank?

[GrahamS2]

OMG, dont go buy a new "Boost" crank.

You can use your old crank and merely change the chainring to one with a 3mm offset rather than the standard 6mm offset.

And save a lot too...

Who makes these for a 96BCD crank? Boost crank has a different spider to get the offset, not a different chainring...

[splat]

Who makes these for a 96BCD crank? Boost crank has a different spider to get the offset, not a different chainring...

 

Do you mean Shimano ?

I see that the XT M8000 cranks are different for Boost. Same chainring though.

 

https://bike.shimano.com/en-EU/product/component/deorext-m8000/FC-M8000-B1.html

 

https://bike.shimano.com/en-EU/product/component/deorext-m8000/FC-M8000-1.html

[WIPEOUT 1000]

I understand the theory, but in reality, unless you're on a correctly setup single speed the chain is normally not straight anyway. I.e. if a chain can manage on a 1x12 system, 3mm should not be a problem. 

[GrahamS2]

Do you mean Shimano ?

I see that the XT M8000 cranks are different for Boost. Same chainring though.

 

https://bike.shimano.com/en-EU/product/component/deorext-m8000/FC-M8000-B1.html

 

https://bike.shimano.com/en-EU/product/component/deorext-m8000/FC-M8000-1.html

I do mean Shimano. He said you get chainrings with 3mm offset. I couldn't find those when I bought my boost crankset  

[Li Mu Bai]

Who makes these for a 96BCD crank? Boost crank has a different spider to get the offset, not a different chainring...

All depends on your crank. Each has its own spider configuration specific to that manufacturer.

I recently put an Absolute Black 110bcd oval chainring on my old XT 783 crank and works great.

Chainrings are either made "boost" or standard by various aftermarket companies

You need to shop around.

try this: https://absoluteblack.cc/chainrings.html

 

If you have no crank at the moment then buying a new boost crank if that works with your frame that has a 12x148 rear wheel hub is fine. It may set you back a fair bit if going for a XX1 or X01 - R9k? A few years ago the XX1 sold for R3.5k so the eagle bandwagon is rolling...

[GrahamS2]

I understand the theory, but in reality, unless you're on a correctly setup single speed the chain is normally not straight anyway. I.e. if a chain can manage on a 1x12 system, 3mm should not be a problem. 

Chainline is only half the issue, frame clearance is the other half. Particularly if you want to run a bigger front ring.

[GrahamS2]

All depends on your crank. Each has its own spider configuration specific to that manufacturer.

I recently put an Absolute Black 110bcd oval chainring on my old XT 783 crank and works great.

Chainrings are either made "boost" or standard by various aftermarket companies

You need to shop around.

try this: https://absoluteblack.cc/chainrings.html

 

If you have no crank at the moment then buying a new boost crank if that works with your frame that has a 12x148 rear wheel hub is fine. It may set you back a fair bit if going for a XX1 or X01 - R9k? A few years ago the XX1 sold for R3.5k so the eagle bandwagon is rolling...

Not seeing any boost chainrings on that site?

[DieselnDust]

A boost crank has a Q factor of 165mm or greater running a chainring of 3mm offset

[Captain Fastbastard Mayhem]

Chainline is only half the issue, frame clearance is the other half. Particularly if you want to run a bigger front ring.

Ah yes. Forgot about that

[Li Mu Bai]

Not seeing any boost chainrings on that

Clearly says boost in several of the chainring headings

[Eddy Gordo]

Non boost is a 6mm offset towards the bb. 

Boost is 3mm or 0mm offset.on a direct Mount  sram crank. The spider is not used.

 

Shimano has  this https://www.bikeinn.com/bike/shimano-slx-11s-boost/136627443/p?utm_source=google_products&utm_medium=merchant&id_producte=5852184&country=za&gclsrc=aw.ds&&gclid=EAIaIQobChMI1pqn97aE4AIVbgDTCh0N9w-0EAQYAyABEgLY0vD_BwE

[Me rida my bicycle]

The 3mm or zero offset is more to do with frame clearance I think than chain line.

a boost frame is obviously 5mm wider (on each side) so something has to make space. Because running a 12spd that chain is going to what looks like it's limits only when running middle to lower gears does my chain look good to me and that's running the correct offset.

I actually think if the offset was more the chain line would look better but hey who am I to argue with a manufacturer there has obviously been extensive testing done.

[Captain Fastbastard Mayhem]

The 3mm or zero offset is more to do with frame clearance I think than chain line.

a boost frame is obviously 5mm wider (on each side) so something has to make space. Because running a 12spd that chain is going to what looks like it's limits only when running middle to lower gears does my chain look good to me and that's running the correct offset.

I actually think if the offset was more the chain line would look better but hey who am I to argue with a manufacturer there has obviously been extensive testing done.

3mm (142mm - 148mm = 6mm diff overall, divide by 2) and you're right, but also wrong. It's for clearance of chainstays AND chainline. 

[Me rida my bicycle]

3mm (142mm - 148mm = 6mm diff overall, divide by 2) and you're right, but also wrong. It's for clearance of chainstays AND chainline.

 

sorry I forgot the rear is only 6mm it's the front that's 10mm.

[MORNE]

Thought i'll post this here because i'm seeing way too many "i bought the 'wrong' crank - need Boost adverts in the classifieds.  

Non boost crank (Saint m820,CL=50mm), boost 148mm frame...10 speed cassette. 11 speed chain....perfect shifting, can back pedal for days without chain dropping. 4mm frame clearance (this frame can take 27,5 x3.25" tires) on normal 32T N/W 104 BCD chainring using 2,5mm drive side spacer on a 73mm BB as per usual. 

 

IMO..Just More proof that the bike industry is selling you crap that you don't always  need. Yes i know it will be crank/frame specific in some cases. But i wasn't going to let that stop me anyway...