Mountain bike drivetrain advice...

6
Posted 13th AprEdited by:"yadiyada"
I have a 27 speed bike. I want to change to just a single 9 speed set up as doing so will give me better rear tire clearance for big tires (no front derailleur getting in the way) and a cleaner setup.

My current rear derailleur is a 9 speed long cage Shimano Altus (which needs changing as it's damaged). I bought a Deore 592 9 speed long cage derailleur to replace it. However, I'm now wondering if I can/should use a short or medium cage derailleur (quicker shifts and less chance of damaging it on trail obstacles).

My rear cassette is a Shimano HG400 12-36, and front chain ring is an SR Suntour XCR6, 48/36/26T. I tend to always be on the 48 tooth chainring, and 36 on occasion. So am thinking maybe a 42 tooth chainring up front?

The bike is a Marin Muirwoods 2018 - which I want to convert into a chunky tire bikepacking setup.

Sorry for the long winded post. The HUKD community seem to know the answer to most things, so I figured I'd put this question out there
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6 Comments
It's been a while but as you're not changing the rear mech speed you just need to remove the slack from the chain. Don't they still make guards for you chain set? Used to be able to get an aluminium plate that bolted onto you top ring and a rear mech guard as well.
How does the front mech get in the way of the tyres? The most likely issue with moving to fat tyres is clearance arounfd the rear chainstay and the brakes.

If you drop to a single front ring you may need more range on your rears - look at the spec on most stock bikes with only rear gears.

A short mech probably wont have the range to cover what you need. The long mechs are needed to give clearance on the gear rings themselves and to take up the slack from the difference in circumference of the lowest and highest gears.
mas994 h, 7 m ago

How does the front mech get in the way of the tyres? The most likely …How does the front mech get in the way of the tyres? The most likely issue with moving to fat tyres is clearance arounfd the rear chainstay and the brakes.If you drop to a single front ring you may need more range on your rears - look at the spec on most stock bikes with only rear gears. A short mech probably wont have the range to cover what you need. The long mechs are needed to give clearance on the gear rings themselves and to take up the slack from the difference in circumference of the lowest and highest gears.


37457482-dVf8a.jpg
(Excuse the dirt ).

I'm not moving to 'fat' tires as such... but certainly planning for some 2.5" tires up front (or as big as I can get) and probably around 2.3 in the back (again, as big as I can get). There would certainly be some extra space for tire clearance with the front derailleur removed.

I could of course just upgrade to a different bike - but I really like the balance and feel of this bike (and the steel frame)...plus, it is the bike that has helped earn me my money over the last 6 months as a cycle courier - so it would be quite nice to carry on using it.

Given the advice about gear circumference, it looks like I'm as well to keep the long mech Deore rear derailleur. And thinking about it, I'm guessing there must be a more sleek and low profile front derailleur that I could change to. Maybe a double rather than triple chainring.
thats a really unusual front mech if it sticks sbetween the wheel and frame like that. All my bikes have had it sitting on the side - minimal intrusion. Can you alter the cable run and move the mech higher? It looks like it is sitting below the height of the ring
If you've got the YouTube installed on your computer, I'd ask on this channel:
GMBN Tech
youtube.com/cha…eos
Look for the "Ask GMBN Tech" videos to find out how to ask your question.
L
mas996 h, 55 m ago

thats a really unusual front mech if it sticks sbetween the wheel and …thats a really unusual front mech if it sticks sbetween the wheel and frame like that. All my bikes have had it sitting on the side - minimal intrusion. Can you alter the cable run and move the mech higher? It looks like it is sitting below the height of the ring


I kind of just assumed that was how all mechs operate...but I'm now seeing that mine is just an oddity! So I'm going to replace that front mech for something low profile - and either retain the triple, or drop to double chainrings.

Thanks for the comments - it's set me on a better track for my bikepacking modifications
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