Specialised Sirrus X Chainring change

Orfeus67

New Member
Hi
I have a Sirrus X with a 40T chainring. I want to change this for something like a 50T to get a bit more speed. Can this be done - and can anyone recommend a chain ring that will fit?
thanks
 

Cycleops

Legendary Member
Location
Accra, Ghana
You need to post a pic with some dimensions. Specialized use an unbranded crankset so finding alternative rings might be difficult. If it's a square taper you might find 50t crankset out there somewhere something like this:

View: https://www.amazon.com/CYSKY-Single-Crankset-Crankarms-Bicycle/dp/B071769J15

You'll also need a longer chain.

:welcome: to the forum.
 
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Orfeus67

New Member
thanks for the replies so far.
So, the Sirrus X comes standard as one on the front (40T) and eight on the back (11-42).
If I fit a 50 on the front, looking at a Gear Calculator I reckon this will mean I lose the 42 on the back, with the 34 then becoming the lowest gear (currently second lowest gear). Given it is fairly flat round here and I rarely go lower than 3rd gear, this should be a reasonable pay-off to get a bit more speed.
Anything I can source in the UK to go on the front?
 

Sharky

Guru
Location
Kent
A 50t chainring won't necessarily give you more speed. It will just make you pedal more slowly. Presume your smallest sprocket is a 12t? It will only help if you are continuously riding on the 12t and running out of revs. But at this point on an 87" gear, you should be riding at 25mph plus, which is not bad.

If you do opt for a 50t ring, then as said above, a longer chain will be needed and possibly a new cassette as a new chain on an old cassette may not work together.

An alternative would be to consider a different cassette first, with an 11t and if you don't need the bigger sprockets, go for a more compact cassette with closer gaps.

Edit: miss read your earlier post. Notice you already have an 11t cassette. Bt a more compact cassette might help
 
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Cycleops

Legendary Member
Location
Accra, Ghana
Don't think that's a common size but the good news is that looks like a square taper BB so you can simply buy another chainset as I suggested above and swap it over.
The other thing you need to check is the clearance between the chainring and the frame chainstay. Will it take a much bigger chainring or will it foul?
If you're not sure post a pic from above.
 
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Sharky

Guru
Location
Kent
This might help in determining your BCD, if you can't see it marked on the ring:-
Wolf Tooth - How to measure Bolt Circle Diameter (BCD) – Wolf Tooth Components
 
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Orfeus67

New Member
Thanks everyone for your advice on this query. You might have guessed that I'm a newbie at bike upgrades. The downside of being in lockdown is that riding every day has made me more critical of my bike! (Well, not riding today, too cold/wet.)
Cycleops - do these photos resolve your question?
 

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Sharky

Guru
Location
Kent
If a 50t is what you really want and need to replace the crankset, you may need to go for the 5 arm 110 bcd ones.

For my TT setup, I did get a 50t n/w chainring, so I know they are out there.

Good luck
 
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