SRAM crankarm spider cross compatibilty

[macaroon]

SRAM 11 speed carbon road cranks such as Force/Rival/S9XX series: are the spiders compatible between BB30 and GXP axle cranks?
Are the spiders from the mountain bike cranks of the same vintage compatible with the above road cranks?
The crank arms all look very similar, so I'm guessing they are, but I'd like to know from someone who's swapped between them.
Thanks.

[prototoast]

Sram has used a mix of 3 bolt and 8 bolt attachments throughout the years. Generally speaking, you can mix and match within a bolt number, though potentially with some ancillary compatibility issues (e.g., a 3 bolt road spider will fit on 3 bolt mountain crank arms, but you might not necessarily have clearance on your frame for the chainrings to fit).

[Mark McM]

Originally Posted by macaroon

SRAM 11 speed carbon road cranks such as Force/Rival/S9XX series: are the spiders compatible between BB30 and GXP axle cranks?

Yes, all the interchangeable 3-bolt road spiders are interchangeable, between all the models of 3-bolt cranks, and between the GXP and BB30 versions of the cranks.

Originally Posted by macaroon

Are the spiders from the mountain bike cranks of the same vintage compatible with the above road cranks?

Almost:

1. GXP and BB30 MTB cranks with 3-bolt spiders use different spindle lengths (GXP spindles are longer than BB30 spindles), so there are different spiders for GXP and BB30 MTB cranks. Mounting a GXP spider on a BB30 crank will result in a chainline too far inboard, and mounting a BB30 crank will result in a chainline that is too far outboard. Well, the 2nd part is only partially true - mounting standard GXP spider on a GXP crank will result in a standard chainline, and mounting a BB30 spider on a GXP crank will result in a "Boost" chainline.

2. MTB spiders have some nubs and ridges that stick out a bit under the crank arm. MTB crank arms splay outward at more of an angle than road cranks, so the MTB cranks bend outward enough to avoid contact with the nubs and ridges. These nubs and ridges will press against the back of the road arms, preventing the spider from sitting flat on the spider mounting face. However, some judicious use a file should be able to flatten out the nubs and ridges so that the spider sits flat on the crank.

3. The chainring offsets of a GXP MTB spider are the same as on a road spider, so mounting a GXP MTB spider on a road crank will result in a standard road chainline.


Several companies make 3-bolt SRAM compatible spiders in a variety of BCDs (130, 110, 110/74, 104, 104/64), including some that make power meter spiders. These include non-power meter spiders from North Shore, Cane Creek/EE Wings, Praxis, and Engin cycles; and power meter spiders from Power2Max, Segeyi, Magene, and XCadey.

[macaroon]

Great post, thanks very much.
I'd like a sub compact setup (46/30), so I think the 104/64 spider is my best bet due to availability of chainrings.
It seems the 104/64 SRAM spiders are hard to come by, so I'll checkout some of the manufacturers you've listed.

[kppolich]

2 important threads to read through, a the crank arms are not all the same shape and there are 2 spider shapes as well between Red/Force and the lower Rival/Apex.

https://forums.thepaceline.net/showthread.php?t=309974

https://forums.thepaceline.net/showthread.php?t=216403

[macaroon]

Originally Posted by kppolich

2 important threads to read through, a the crank arms are not all the same shape and there are 2 spider shapes as well between Red/Force and the lower Rival/Apex.

https://forums.thepaceline.net/showthread.php?t=309974

https://forums.thepaceline.net/showthread.php?t=216403

Affirmative. I'm expecting a Rival chainset in the post, so I can double check when it arrives.
I'm only interested in the spider swap between carbon crank arms (which all look the same to me).

[Mark McM]

Originally Posted by kppolich

2 important threads to read through, a the crank arms are not all the same shape and there are 2 spider shapes as well between Red/Force and the lower Rival/Apex.

With 3rd party manufacturers getting involved, there's actually more than just 2 - there's more like 3 or 4.

What kppolich is talking about is that some spiders are shaped with a recess to blend with specific crank arm shapes. There is no functional need for these recesses to exist, they are mostly cosmetic. Some 3rd part spiders have no recess at all, so they will fit any crankarm shape.

Of the spiders with recesses for specific crankarm shapes, SRAM has two shapes: One for carbon cranks (both road and MTB cranks have the same shape), and one for alloy cranks (both road and MTB cranks have the same shape). SRAM alloy cranks have a slimmer profile, so they will fit within the recess of a "carbon" spider, but SRAM carbon cranks have a wider profile, so they will not fit the recess in a "alloy" spiders. North Shore makes 3 bolt spiders in different varieties with recesses to match carbon or alloy SRAM spiders.

Praxis spiders have their own recess shape to fit fit their own cranks. I believe that a SRAM crank is two wide to fit in a Praxis recess, but that SRAM alloy cranks will fit.

Cane Creek/EEWings and most power meter spiders have no recess, and will fit any crank arm shapes.

Engin makes their 3 bolt spiders in two slightly different shapes. Their "standard" spider have raised areas that interfere with SRAM road cranks, and they have a separate "SRAM" spider that has reliefs machined in so that they fit SRAM cranks (the reliefs are nearly invisible, so that the "SRAM" spider will work with just about any other 3-bolt crank).

[Mark McM]

Originally Posted by macaroon

Great post, thanks very much.
I'd like a sub compact setup (46/30), so I think the 104/64 spider is my best bet due to availability of chainrings.
It seems the 104/64 SRAM spiders are hard to come by, so I'll checkout some of the manufacturers you've listed.

I think you'll have a hard time finding 46/30 chainrings with a 104/64 BCD. There are 46 tooth 104 BCD chainrings, but there are meant to fit the outer position on a triple crank. When using a a 140/64 BCD spider as a double, you'll need to fit the "outer" chainring in the middle spider position. The bolt recesses on an "outer" chainring are on the wrong face of the chainring, so the chainring bolt heads will stick out of the chainring, and can interfere with the chain when using the inside chainring.

A 30 tooth 64 BCD chainring will also be difficult to find.

A better bet for 46/30 chainrings is to use a 110/74 3-spider. These are made by Engin Cycles. Chainrings for this BCD are available in a wide range of sizes by several manufacturers.

Another option is to use a SRAM 120/80 spider. Stronglight makes 45/30 chainrings for this spider, which is pretty close to a 46/30.

Originally Posted by macaroon

Affirmative. I'm expecting a Rival chainset in the post, so I can double check when it arrives.
I'm only interested in the spider swap between carbon crank arms (which all look the same to me).

If these are Rival 11spd cranks, then I'm pretty sure they are alloy, not carbon.

[robt57]

I can say BB30 and GPX spider in my case was a no go.

I had bought a few GPX 3 bolt CX1 chainsets that came with 110 spiders.

I got a GPX 80/120 spider with 28/42 rings and loved it. Sold that bike and went to reproduce the chainset. The next one [spider/rings] was BB30 and the CX1 arms did not fit into the machining in the spider. I had to get a GPX spider and move the rings over.

I should mention the 80/120 ring spider combos were Truativ, not sure if that makes a difference.

[Mark McM]

Originally Posted by robt57

I got a GPX 80/120 spider with 28/42 rings and loved it. Sold that bike and went to reproduce the chainset. The next one [spider/rings] was BB30 and the CX1 arms did not fit into the machining in the spider. I had to get a GPX spider and move the rings over.

Not only do the BB30 MTB spiders have a differently shaped crank recess, but they have a different offset than the GXP MTB spiders. When installing an MTB spider on a road crank, you want to use the GXP MTB spider.

If I recall, the 120/80 SRAM MTB spider will fit road cranks without modification, but the 104/64 SRAM MTB spiders will need to be slightly modified to fit a road crank, by filing down some nubs and ridges that interfere with the back of the crank. However, North Shore 104/64 MTB spiders will fit road cranks without modification. As with the SRAM spiders, the North Shore spiders are available in separate models with recesses for either carbon or alloy cranks, and also in separate GXP and BB30 models with different chainring offsets.

[macaroon]

Originally Posted by Mark McM

I think you'll have a hard time finding 46/30 chainrings with a 104/64 BCD. There are 46 tooth 104 BCD chainrings, but there are meant to fit the outer position on a triple crank. When using a a 140/64 BCD spider as a double, you'll need to fit the "outer" chainring in the middle spider position. The bolt recesses on an "outer" chainring are on the wrong face of the chainring, so the chainring bolt heads will stick out of the chainring, and can interfere with the chain when using the inside chainring.

A 30 tooth 64 BCD chainring will also be difficult to find.

A better bet for 46/30 chainrings is to use a 110/74 3-spider. These are made by Engin Cycles. Chainrings for this BCD are available in a wide range of sizes by several manufacturers.

Another option is to use a SRAM 120/80 spider. Stronglight makes 45/30 chainrings for this spider, which is pretty close to a 46/30.

Also, yes, the Rival cranks are for another project, I'll be using either Force BB30 or S950 GXP cranks for the spider swap.



If these are Rival 11spd cranks, then I'm pretty sure they are alloy, not carbon.

I looked at the Engin 110/74 and figured I'd run into the problem with the chainring bolts as you described. I've several 46t 110 BCD chainrings and realised I wouldn't be able to use them with this setup.
I hadn't considered 46t 104 BCD chainrings would suffer from the same problem, but thinking about it, you're right. I've just looked at one and the recess is on the outside.
Seems like the 120/80 spider might be my best bet then since ooking at Engin social media, it appears like they're no longer in business.
Thanks for the tip on the Stronglight rings, they're usually fairly cheap (this is an experiment of sorts, so trying to avoid spending a fortune).

Also ,the Rival cranks are for another project, I'll be using either Force BB30 or S950 GXP cranks for the spide rswap.

[macaroon]

For posterity's sake, FSA appear to do 46t 120BCD outer chainrings.

[Mark McM]

There's another other option for a 46/30 on a 3-bolt SRAM crank: TA has their "Super Compact" chainrings. This consists of an outer chainring that mounts directly to the 3 bolt crankarm (available in 48 and 46), and an inner chainring that bolts to the outer chainring (available in 32 and 30). In the US, these are available from Peter White Cycles:

https://www.peterwhitecycles.com/tach.php#scdm

[macaroon]

Unforntunatley I'm not in the US......and I'm struggling to find a 30t 80BCD chainring
I did manage to buy the spider though!

[eddief]

https://www.google.com/search?q=blac...WmQNywos4,st:0