MTB Gears Question

Ghuraba

Ghuraba

Ghuraba

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Hi there

I have a very simple and noobish questions as follows.

If a MTB has 27 gears, 3 large cogs at the front and 9 at the back should you be able to go into all 9 gears at the back on each of the three cogs at the front? Which would result in 3 x 9 = 27 gears? I have noticed if you try this the chain is not aligned straight and rubs agains some of the other parts. I presume you shouldn't do this. But just wanted some expert advice on how to use the gear ratios as I have no clue. I have figured out uphill you use the small cog and flat seems to be the larger cog.

Thanks

Michael
 
"Cross-chaining" will wear your chain and rings much faster than normal. They aren't designed to have 27 gears, more gears just gives your more usable options. You should try to keep your chain as straight as possible :)
 
Not all 27 combinations actually give distinct gear ratios, so some are redundant. Using a large cog at the front and at the back (or small cogs for both) is pointless because they'll cancel each other out and you might as well just have it on the middle cogs.

When you're on the small chainring (front cog) you should probably use the 4-5 largest rear cogs, while on the large chainring you should use the 4-5 smallest. Generally speaking you'll want to use the middle chainring 80% of the time and only go down to the smaller one for steep hill climbs. The big chainring is only needed when you're going really fast.

Like MoratJG says, try to keep your chain straight :)
 
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As an extension to this question: on a normal road bike where you're just going to be doing gentle riding without many hills, is there any real need to have more than one chainring & a set of 7-9 sprockets?
 
WillyNelson said:
As an extension to this question: on a normal road bike where you're just going to be doing gentle riding without many hills, is there any real need to have more than one chainring & a set of 7-9 sprockets?
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no real need. theres a lot of prebuilt road bikes that just come with 9/10 on the back
 
Also remember to keep your cadence (how fast you're pedalling) at about 80-90 rpm, which is the optimal speed. You should be "spinning" the cranks rather than "pushing" them, and if you find yourself pedalling too hard and too slow then you're in too high a gear.
 
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6thElement said:
So my feet are going too fast with my cadence at 105+? :p
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Fixed :p


A double chainset will allow you to keep a straighter chain line over a single chainring setup. The front derallieur will also help to stop the chain falling off.
 
I'll spin at 95-100 for normal riding on the road, but can happily spin at 120 if required.

It's down to the individual, but spinning is much better for the knees than trying to mash too high a gear at a low cadence while seated.
 
6thElement said:
It's down to the individual, but spinning is much better for the knees than trying to mash too high a gear at a low cadence while seated.
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I have this problem (cadence, not knees) :(
100rpm is pretty much my maximum, anything over that and i start bouncing about on the seat and it feels very inefficient.
Im trying hard to mend my ways but cruising along at ~50 rpm feels like so much less effort than doing the same speed at ~90 rpm. I havnt got a cadence sensor but im sure i'v raised my average rpm by about 10-15 over the past few months, so i am getting there. Slowly.
High rpm feels very unnatural to me tho - as if i'm pushing hard just to maintain a speed that i could happily keep up all day with a bigger ratio gear.
 
touch said:
I have this problem (cadence, not knees) :(
100rpm is pretty much my maximum, anything over that and i start bouncing about on the seat and it feels very inefficient.
Im trying hard to mend my ways but cruising along at ~50 rpm feels like so much less effort than doing the same speed at ~90 rpm. I havnt got a cadence sensor but im sure i'v raised my average rpm by about 10-15 over the past few months, so i am getting there. Slowly.
High rpm feels very unnatural to me tho - as if i'm pushing hard just to maintain a speed that i could happily keep up all day with a bigger ratio gear.
Click to expand...

Lower cadence is OK if you're just cruising and not putting too much effort in I think. It's when you're putting more effort in that you should be spinning at a higher cadence. That said, 50 is quite low.
 
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