Creo Chainring Limitation

[andydale]

The Specialized Support Center webpage states - “All models use a 1x drivetrain using a 110bcd spider. A 46T chainring is standard. 1x 42-50T chainrings are compatible.”

Does that imply that the smallest chainring allowable is a 42T, although a 110bcd can support a 38T. Can anyone enlighten me as to why a 38T chainring cannot be fitted.

 

[andydale]

I don't think the issue is chain slack, you would expect to change the chain length if moving from 46T to 42T or 50T also.

 

[Stefan Mikes]

The Specialized Support Center webpage states - “All models use a 1x drivetrain using a 110bcd spider. A 46T chainring is standard. 1x 42-50T chainrings are compatible.”

Does that imply that the smallest chainring allowable is a 42T, although a 110bcd can support a 38T. Can anyone enlighten me as to why a 38T chainring cannot be fitted.

Why not take the risk Andy. Not the same e-bike but I and @Marcela successfuly replaced 48T chainrings with the 38T and 36T ones on our Vados, respectively. The only difference is our rings were 104 BCD.

 

[andydale]

Have had a response to this question from Specialised Support - apparently they have not validated a chainring below 42T, so do not advise it.
Also they expressed concern that the chain would not clear the chainstay with the smallest cassette cog.
Any Creo users have thoughts about a 10T to 38T combination with a strong clutched rear mech, do you think there would be a chainstay clearance issue or a chain slap issue.

 

[mschwett]

here’s a photo from an XL creo with a 42t up front, shifted to the 10t cog of an SRAM 10-42 cassette. it clears by a bit under .3”, and the top segment of the chain doesn’t move vertically much since it’s in tension when driven.

there is 17” horizontally between the two points which define the chain line, with the tightest point 2.5” from the rear. so downward movement in the top arrival point of the chain at the front should result in about 1/7 the movement at that pinch point.

a 4t smaller chainring would be .32” smaller in radius (4 teeth = 2” less circumference / pi = .64” less diameter) so the chain at the choke point ought to only move down by .05 inches. that said …. you can see from the pic that it’s close, less than .5” to the centerline of the chain and around .3” to the outer surface. .3 goes to .25… maybe somewhere between .2" and .25" of clerance. ought to work give how little the chain moves down from that point.

 

[e-levity]

I've been running this narrow-wide 40t chainring with a 11-45 cassette for over 1,000 miles without any issues:

 

[mschwett]

I've been running this narrow-wide 40t chainring with a 11-45 cassette for over 1,000 miles without any issues:

Nice! Note that going from 11t to 10t in the back has a much bigger impact on chain proximity to the chainstay than going from 42 to 40 or 38 would up front, since it’s so much closer.

 

[andydale]

Thanks guys for your input - love the maths. Looks as though 10T/38T is doable, but maybe a 9T is a step too far (or a cog too small).

 

[mschwett]

Thanks guys for your input - love the maths. Looks as though 10T/38T is doable, but maybe a 9T is a step too far (or a cog too small).

i might try a 9t someday, expecting that it might not work … there are some interesting choices by e13 (9-46 ) and others. great for combo road / gravel rides around here where you’ve got long flat and downhill road segments and then 20% grades in the “gravel…”

 

[Dazmanturbo]

I swapped mine for 38T Absolute Black front chain ring, narrow wide. On the back, I swapped to E-Thirteen 11 speed 9 to 34. I have done nearly 3000 miles with this set up and not had a single issue. This set up saved a ton of weight over the stock set up. The chain ring was half the weight and the cassette also lopped off over 250g. I don't use the 9 cog that often, but it works fine when I do

 

[andydale]

I swapped mine for 38T Absolute Black front chain ring, narrow wide. On the back, I swapped to E-Thirteen 11 speed 9 to 34. I have done nearly 3000 miles with this set up and not had a single issue. This set up saved a ton of weight over the stock set up. The chain ring was half the weight and the cassette also lopped off over 250g. I don't use the 9 cog that often, but it works fine when I do

Wow, music to my ears - way to go.

 

[kahn]

I swapped mine for 38T Absolute Black front chain ring, narrow wide. On the back, I swapped to E-Thirteen 11 speed 9 to 34. I have done nearly 3000 miles with this set up and not had a single issue. This set up saved a ton of weight over the stock set up. The chain ring was half the weight and the cassette also lopped off over 250g. I don't use the 9 cog that often, but it works fine when I do

I guess while the bike was in the shop a few days ago, I should have had them put on the smaller front chain ring. But with all of the chain popping on last week's ride, I wanted to bike working again and not introduce yet potentially additional problems. Maybe next time. They did put on the little chain guard that Specialized offers. As I look at it, I'm not sure how one could move the chain around since that guard is very close to the chain. I should grab a photo of it. But I also thought that a smaller chaingring would immediately make the chain guard obsolete.

 

[Dazmanturbo]

I guess while the bike was in the shop a few days ago, I should have had them put on the smaller front chain ring. But with all of the chain popping on last week's ride, I wanted to bike working again and not introduce yet potentially additional problems. Maybe next time. They did put on the little chain guard that Specialized offers. As I look at it, I'm not sure how one could move the chain around since that guard is very close to the chain. I should grab a photo of it. But I also thought that a smaller chaingring would immediately make the chain guard obsolete.


View attachment 110121

My chain has never come off. The Absolute Black chain ring is a quality bit of kit and dead easy to swap. Make sure to get narrow / wide.

 

[mschwett]

i haven’t had a single chain drop with the current setup, thousands of miles ranging from smooth fast road to singletrack! i don’t think the little catcher is too important …