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Discussion Starter · #1 ·
I was wondering if there are particular situations when you're better off switching the front or rear gears to change speed? I normally change the front gear speed when I want a big speed change rapidly such as if I'm on flat pavement and a sudden steep hill appears, and change the rear gear for more subtle changes like a slight change in the path's inclination.

Am I using them right?

Thanks
 

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Not necessarily right. Every chainring is supposed to work with 5 rear cogs - the big chainring with 5 smallest cogs and so on (provided, you have 9 gears in the rear). Chain crossing is not a good idea.
 

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Discussion Starter · #3 ·
What's chain crossing? And this is the first time I hear of this, you mean if I'm on a certain gear on the front I shouldn't use certain gears on the back? Is that why my chain sometimes rubs against the front derailleur?

So which gears work with which?
 

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I mean, using, say, the big chainring with big rear cog. Then the chain may rub against the FD cage.
Yes, the more straight the chain line is, the better. That is, you will be better off, using the middle ring with 4-5 middle cogs, big ring with 4-5 smaller cogs and the small ring with 4-5 larger cogs in the rear. Otherwise, you may have problems with shifting, and the rings get worn out much faster.
Edit: I am sorry, I forgot the right English term - it is rather "cross-chaining", or "cross-gearing", but I hope, you got the idea anyway. My bad.
 

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each chainring uses a proportion of the rear cassette. the large chainring will use the smallest 3rd of the cassette, the middle chainring the middle 3rd and the smallest chainring the largest 3rd, this way you will avoid stressing the chain by bending it laterally or against the links, this is "chain crossing".
you may find there are situations where you will need to change, say, to a smaller chainring while simultanoeusly changing to a larger cog on the cassette.
 

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Discussion Starter · #6 ·
Thanks I had no idea. So when a bike is advertised as 24 or 27 speeds it's not really true?
 

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ch2s said:
Thanks I had no idea. So when a bike is advertised as 24 or 27 speeds it's not really true?
In terms of pure maths it is true, 3 in the front multiplied by 9 in the rear makes 27 in theory. But actually, some combinations give you the same ratio, and others are not desirable - I mean, the cross-chaining. I actually use some 10-12 combinations out of 24 available.
 

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Discussion Starter · #8 ·
I always thought that some combinations would be the same or very similar. Which two combinations would give the same ratio for example if you don't mind? I guess I could figure it out but I don't feel like doing maths right now and don't know by hart the number of teeth on each gear.
 

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I didn't know about the large ring using the smallest rear & so on. I stick to the smallest ring in the front with cog 2-4 on the rear when I'm on trails. 1:2 on most climbs, 1:4 when I'm on the bottom trail.

Not too long ago I found out you have to hold the shifter in when you upshift for the front. That isn't mentioned in the bike manual or anywhere else! I thought my gears were out of whack. Obviously this is my first geared bike...

What riding conditions would you use the largest front ring for?!? Seems totally unnecessary to me as far as mountain bikes are concerned.

thanks!
 

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Discussion Starter · #10 ·
What do you mean by hold the shifter in when you upshift? What kind of shifters do you use?

And about the large chanring when I'm on road I'm always on the largest chainring and almost always on the smallest rear gear (hardest possible combination) or just 1-2 up on the rear gears if I'm getting tired (I often even go up hills on road on the hardest possible combination).
 

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I have Sram shifters. When I upshift from smallest to middle ring, I have to hold the shifter in until chain makes it up. It isn't near-instant like the rear. It was just me being a newbie learning that..
 

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Discussion Starter · #12 ·
Someone correct me if I'm wrong but it sounds like your shifter needs to be adjusted, the cable may have stretched which is normal and can cause exactly that type of shifting problem. Your LBS normally offers free tune ups for a while after you buy the bike, maybe you should get them checked or adjust them yourself if you know how because it really sounds like it's out of alignment to me.
 

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I have the same problem as bitewerks but with Shamino Deore. I think my problem is I am trying to shift from the small sproket to the middle while in 1st gear. I did notice that it does shift better when I shift the front while in 3 or 4 gear. I had taken the bike back twice to the bike shop and still felt it wasn't right. At what point on the hill do you make the shift from the Granny to the middle chainring?

Millman
 

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this is an awesome subject... i didn't know this either but it makes sense... i always thought that there is something wrong with the bike when i used to do cross-chaining and i would hear the chain touch w/e metal part
 

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Another website I read advises using only the biggest three cogs (ie lowest gears) with the granny gear, any cog with the middle chainring, and only the smallest three cogs with the big chainring. That seems to work just fine. I rarely used the largest 3 cogs before but now I use the whole range when I'm on the middle ring, rather than changing gear using the front derailleur.

Bear in mind also that big cogs spread force more evenly as they're engaging the chain with more teeth, so using the full range of your cassette rather than just the smallest ones helps to even out and reduce the wear and prolong the useful life of your cassette.
 

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ch2s said:
Someone correct me if I'm wrong but it sounds like your shifter needs to be adjusted, the cable may have stretched which is normal and can cause exactly that type of shifting problem. Your LBS normally offers free tune ups for a while after you buy the bike, maybe you should get them checked or adjust them yourself if you know how because it really sounds like it's out of alignment to me.
Generally speaking, it is right, the gears should shift seamlessly, if tuned up properly, In reality, there may be other problems, like derailleur hanger bent a bit (yet not enough to justify replacement), or sprockets of cassette not in ideal condition. So it is not always possible to get it perfectly right. Then you usually can tune the cable tension so, that shifting up will be very good, but shifting down won't, or vice versa.
Also, cables may rub against housings. The housings may be damaged, particularly if you have the cables routed under the downtube and full length housings. I lube the points, where the cables enter housings, with some dry lube (like Pedro's Ice Wax, but any dry lube will do, I think).
 

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ch2s said:
I was wondering if there are particular situations when you're better off switching the front or rear gears to change speed? I normally change the front gear speed when I want a big speed change rapidly such as if I'm on flat pavement and a sudden steep hill appears, and change the rear gear for more subtle changes like a slight change in the path's inclination.

Am I using them right?

Thanks
I don't know where some of the info in this thread is coming from, but you can use all the gears in the rear with the center ring. Otherwise, 1x9 and 2x9 would not work.
 

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I had all the gears adjusted a few days ago. I broke the front shifter in a crash & the LBS replaced it. Still shifts the same way but I keep it on the small ring all the time for trail riding. It's just easier that way. I rarely ride in the streets. If I ever need a new crank, I'm going w/2 rings & bashguard.

Anyone know if some shifters are built stronger to withstand abuse & crashes? Seems like that's a pretty likely component to get damaged... Thankfully, it was a free replacement for me!
 
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