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So, these new thicker chainring tabs...

big-ted

Danced with A, attacked by C, fired by D.
Sep 27, 2005
1,401
45
Vancouver, BC
Seems like most modern 'DH' cranks are going over to 4.5mm thick chainring tabs. Educate me RideMonkey:

1) Is it possible to run a middle ring and big ring on such cranks? Seems like you'd need a special big ring for it to sit the correct distance away from the middle ring, but I don't see these advertised.

2) What is the standard chainring tab thickness? Is the position of the middle ring the same (measured relative to frame centreline I guess)?

3) I need to modify my existing bashguard to fit a set of these new cranks. Hence my asking 2) I guess if the position of the middle ring isn't quite the same it's not going to make a significant difference to chainline, and I can just tweak the position of the chainguide backplate (Straitline Silent Guide). So I can just machine off the difference in tab thickness from the inside of the bashguard...


I can't say I really see a need for thicker tabs. The only tabs I've ever wrecked were a set of the old, non-radiused Race Face ones. Thanks bike industry for giving me yet another standard I needed like a kick in the teeth...
 
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big-ted

Danced with A, attacked by C, fired by D.
Sep 27, 2005
1,401
45
Vancouver, BC
Er, now that I've had a coffee, I realise there's nothing stopping from just measuring the thickness of the tabs on my old cranks...
 

HAB

Chelsea from Seattle
Apr 28, 2007
10,489
839
Seattle
Er, now that I've had a coffee, I realise there's nothing stopping from just measuring the thickness of the tabs on my old cranks...
:rofl:


Shimano, Gamut, e.13, and some others have made bashguards specifically for this purpose. I'm not aware of a big chainring that does the same, but I've never looked particularly either.
 

- seb

Turbo Monkey
Apr 10, 2002
2,924
0
UK
I did think "I'm sure Rob isn't the kind of guy who's too lazy to measure his own cranks" :D

Moving to thicker tabs seems like a good idea to me. I've never VISIBLY bent mine, yet after a few bashguard hits I always end up with oscillating chainrings, even when I take a ring off and put a new one on, so I can only assume that I am managing to bend the tabs, somewhere.
 

HAB

Chelsea from Seattle
Apr 28, 2007
10,489
839
Seattle
Moving to thicker tabs seems like a good idea to me. I've never VISIBLY bent mine, yet after a few bashguard hits I always end up with oscillating chainrings, even when I take a ring off and put a new one on, so I can only assume that I am managing to bend the tabs, somewhere.
I've bent the chainring tabs on a Saint 800 crank badly enough I had to scrap it. Especially with the proliferation of taco style guides it seems like a good idea to me.
 

big-ted

Danced with A, attacked by C, fired by D.
Sep 27, 2005
1,401
45
Vancouver, BC
I did think "I'm sure Rob isn't the kind of guy who's too lazy to measure his own cranks" :D

Moving to thicker tabs seems like a good idea to me. I've never VISIBLY bent mine, yet after a few bashguard hits I always end up with oscillating chainrings, even when I take a ring off and put a new one on, so I can only assume that I am managing to bend the tabs, somewhere.
I am a little apprehensive about machining out my bashguard, as I'm sure I wont be able to get it 100% perfect so that I'll be stuck with a wobbly bash guard for ever after...
 

big-ted

Danced with A, attacked by C, fired by D.
Sep 27, 2005
1,401
45
Vancouver, BC
I've bent the chainring tabs on a Saint 800 crank badly enough I had to scrap it. Especially with the proliferation of taco style guides it seems like a good idea to me.
Wouldn't the thicker tabs be more applicable to bashguard style chain guides, where the force of an impact is going into the crank spider?
 

HAB

Chelsea from Seattle
Apr 28, 2007
10,489
839
Seattle
It probably matters more on a normal bashguard style guide, but I actually meant what I said, because with a taco it doesn't really matter how thick the chainring tabs are. That Saint crank I trashed was actually with a taco guide, but it probably was a 1 in a million hit.
 

HAB

Chelsea from Seattle
Apr 28, 2007
10,489
839
Seattle
I am a little apprehensive about machining out my bashguard, as I'm sure I wont be able to get it 100% perfect so that I'll be stuck with a wobbly bash guard for ever after...
What do you have to work with? It would be easy as to get it flat with a mill.
 

big-ted

Danced with A, attacked by C, fired by D.
Sep 27, 2005
1,401
45
Vancouver, BC
Clearly, you haven't seen my mill... ;)


Seems to have worked though. My old Atlas crank tabs were 3.3mm thick. I took 1.1mm off the 4.5mm tabs of my new Atlas cranks. Seems good. Shakedown of the new bike in Whistler tomorrow. Giddy.
 

big-ted

Danced with A, attacked by C, fired by D.
Sep 27, 2005
1,401
45
Vancouver, BC
aurum1.jpg

Crappy phone pic.

No mill pics I'm afraid. I was in too much of a rush to finish and get home to fit my parts!