Roger said:David Martin wrote:
Never heard of 10 speed XT, mine is 9 speed. As the bike with the Altus
has its chain off at the moment, I just tried it for size on the 9
speed XT block. It fits....just. I think this would give a lot of
hassle in real use as it is likely to touch and catch on adjacent cogs.
OK, it is a whatever the largest number is XT rear mech that I have
been using with a 7/8 speed chain on an 8 speed cassette.
Quoted message said:Quoted message said:Quoted message said:You can also use a standard 22/34/44 chainwheel (again, 6 and 7 speed
types).
Any sort will do as long as the gap between chainrings is sufficiently
small to not drop a narrow chain down there. A 10-speed chainset will
be fine with a 7 speed chain.
Quoted message said:
I have no road bikes so no nothing about 10 speeds, but as far as MTB
stuff is concerned I think mixing 9 speed and 7 speed parts will always
lead to grief. The gap between cogs on the 6 the and 7 speed blocks is
around 5.5mm, on the 9 speed blocks it is around 4.5mm. Chains are
narrower as a result, and hence so are cog teeth.
Working is one thing, working well is another.
I was probably not careful enough to point out that it was in the
context of a 9/10speed *mech* with a 7 speed chain. 7 speed chain with
10 speed cassette is not sensible under normal circumstances.
My recommendation is to match the chain to the cassette/freewheel.
Everythign else will look after itself (except for very narrow chains
and old chainsets where the narrow chains could get between the
chainrings.)
Quoted message said:Quoted message said:If by that you mean the bikes normally sold with such rear mechs tend
to have freewheels rather than cassettes then you would be right. It
may require a new wheel to upgrade the number of sprockets at the rear.
I mean you will not find replacement freewheel+cog units with 11 teeth
(leastways I could not find any).
You are correct there. 11 is too small to fit on.
Quoted message said:Quoted message said:there are two things that have to change at the same time in an indexed
system:
the shift levers and the rear cluster of sprockets. They must both be
rated for the same number of gears or it will not work (apart from a
couple of exceptions). Everythign else is compatible.
Strongly disagree. Firstly you can use shifters with more speeds, in
particular a 7 speed shifter on a 6 speed block, just make sure the end
screw is set right and you will not be able to go into 7th.
That is one of the exceptions.
Quoted message said:Secondly,
in the Shimano systems the distance that the shifter cable moves is
equal to the distance between the cogs, i.e. it is different for 9
speed and 6/7 speeds. As for being 'compatible', see above, it will
never work perfectly because everything is slightly missized.
?? A rear mech moves the same amount for a given amount of cable pull.
It is the indexing that determines the spacing between the gear
positions. Mechs are compatible across all SIS ranges.
Quoted message said:Of course the rear mech itself does not actually know how many cogs
there are, it may well be that e.g. 9 speed shifters on a 7 speed Altus
would work fine because the shifters would move the mech by the correct
distance, but of course the sprockets are still dimensioned for 7 speed
chains so once agin, it would never be quite right.
Nope. It works perfectly. The difference between 7 and 9 speed chains
is in the outside, ie how much of the rivet protrudes. The derailelur
spacing between positions will still be just right. You can use the
same sprockets all the way up to 9. I think 10 may be slightly narrower
so a 10 speed chain will not work on 9 or fewer. But a 10 speed
compatible rear mech works fine on 7 speed uniglide and 7 speed
hyperglide with an 8 speed chain.
Quoted message said:Quoted message said:The other thing to watch out for is the range of tooth sizes at the
back. FOr a triple front chainset and a large range at the back (more
than 28t largest rear sprocket) you will need a long cage rear
derailleur to take up the slack in the chain.
What counts is the difference in the number of teeth. Most MTB rear
mechanisms are made for 21t difference as standard, with 22/44 triple
on the front. They do shorter versions of the mechanisms but you will
rarely find these in the shops as MTB'ers nearly alwys go for maximum
range. Most serious MTB bikes (Deore and up) use 11/32 cassestes
(typically 11,12,14,16,18,21,24,28,32), but as cheap axles/freewheels
can't take the 11 tooth wheel supermarket types with large range gears
go from 13 to 34. That means you get higher top gear, but it is so high
it is virtually useless.
Lower top gear, and it is quite useful when taking big loads up hills.
I was using my 28x32 in serious anger when touring. OK, you aren't
going fast but you are going. I also used the 48/11 coming down the
other side ;-)
Quoted message said:Don't be confused by the length of the cage, the size of the sprocket
wheels is just as relevant, so you can have mechs with noticably
shorter cages (but larger sprockets) which are able to cover the same
21t range.
And the ranges given are quite conservative. You can normally get a few
more t difference if you need to. Broadly speaking they are classified
as long cage, medium cage and short cage. For the range the OP
described, a long cage will be ideal.
Quoted message said:Quoted message said:Quoted message said:At the end of the day a 21 speed Altus setup gives you the same range
as a 27 speed, but of course with bigger gaps between ratios! On the
plus side, 7 speed systems are heavier and clunkier......read more
resilient to misuse like cross-chaining!
That is more a function of the chain. 7 speed chains are chunkier than
10 speed.
No doubt that the chain is the biggest issue, but also the teeth are
wider.
10 speed are narrower, everythign else is the same tooth width. The
spacing between the teeth gets smaller though.
...d
