Suntour GPX freewheel and gearing question

[R. Srinivas]

I am an absolute newbie and would like to use my bike for
commuting 5mi each way to work. I have acquired an old used
Specialized Allez road bike with Suntour GPX drivetrain
components. In my two days of biking to work, I am finding
that climbing bridge overpasses is a chore. (Didn't I say I
was badly out of shape?) Anyway, I think my gearing is not
in my favor. The chainrings are 52t and 38t Suntour GPX, but
the freewheel is a 7 speed with 19t to 13t. So the lowest
gearing I have is 54" which is tough going for me and would
like to make that better.

The questions I have are:
1. Can I replace the 13-19 freewheel with one that has 30+
teeth as the largest gear? I see a Suntour 13-30t 7spd
freewheel on Ebay and am wondering if there is something
with higher number of teeth on the largest gear.
2. Should I be thinking of adding a smaller ring, if
possible, to the two rings that I have.
3. How difficult is it to do these things by myself? I like
mucking things around by myself, but have no idea how
good I am doing it. I managed to reverse my drop bar to
allow me to sit more upright.

If I am able to keep it up for a while, then I will probably
have more questions.

Srinivas

 

[Russell Seaton]

[email protected] (R. Srinivas) wrote in message news:<[email protected]>...
> I am an absolute newbie and would like to use my bike for
> commuting 5mi each way to work. I have acquired an old
> used Specialized Allez road bike with Suntour GPX
> drivetrain components. In my two days of biking to work, I
> am finding that climbing bridge overpasses is a chore.
> (Didn't I say I was badly out of shape?) Anyway, I think
> my gearing is not in my favor. The chainrings are 52t and
> 38t Suntour GPX, but the freewheel is a 7 speed with 19t
> to 13t. So the lowest gearing I have is 54" which is tough
> going for me and would like to make that better.
>
> The questions I have are:
> 1. Can I replace the 13-19 freewheel with one that has 30+
> teeth as the largest gear? I see a Suntour 13-30t 7spd
> freewheel on Ebay and am wondering if there is
> something with higher number of teeth on the largest
> gear.

Nashbar has 7 speed freewheels that have 32 or 34 teeth for
the big cog. They should replace your current freewheel. But
freewheels require special tools to take on and off so you
would probably have to have your local shop do it or buy the
freewheel and then go ask the shop to sell you the
particular freewheel removal tool required. Probably a
unique one for each freewheel.

You would also have to replace your chain with a longer
chain to fit over the big chainring and new big cog in back.
$8 for a new cheap 7 speed chain. $25 for the freewheel. $10-
20 for the freewheel removal tools. And $7 for a chain whip.
Pretty sure you will need a chain whip too for removal.

Your current rear derailleur will work just fine as long as
you stay out of certain combinations like small chainring
and small rear cogs.

http://www.nashbar.com/profile.cfm?category=87&subcategory=-
1109&brand=&sku=11696&storetype=&estoreid=&pagename=

http://www.performancebike.com/shop/profile.cfm?SKU=15981&s-
ubcategory_ID=5130

> 2. Should I be thinking of adding a smaller ring, if
> possible, to the two rings that I have.

You may not be able to. And it would not be as good of an
improvement as the new freewheel.

 

[Leo Lichtman]

"Russell Seaton" wrote: (clip) Your current rear derailleur
will work just fine as long as you stay out of certain
combinations like small chainring and small rear cogs.
^^^^^^^^^^^^^ I am currently struggling with this situation
on one of my mountain bikes. I went from a 28 tooth to a 34
tooth rear cog. The deraileur jockey pulley was so close to
the 34 tooth cog, that it would not shift out of that
position. I eventually got it to work by adjusting the screw
that controls the position of that pulley. It is working
now, but the added distance from jockey to cogset has made
the shifting less precise. The shifting is sometimes delayed
by a couple of pedal strokes.

My chain was then too short, creating the possibility of
breaking something in the big-big position. I know enough
not to use this, but I was afraid I might make a mistake and
end up walking the bike back to the car, so I just added a
couple of links (rather than a whole new chain.). This
creates a very slack chain condition in the small-small
position, but that's less dangerous.

Whether you can gain anything by decreasing the size of your
granny chain ring depends on what you have now. In my
efforts, I had trouble finding anything smaller than 22
tooth. There are ways of going smaller, but I have not
worked out the details yet. An adapter called Mountain
Tamer, which I have tried, interferes with some of the rear
suspension hardware.

 

[R. Srinivas]

[email protected] (Russell Seaton) wrote in message news:<[email protected]>...
> [email protected] (R. Srinivas) wrote in
> message
> news:<[email protected]>...
> > The questions I have are:
> > 1. Can I replace the 13-19 freewheel with one that has
> > 30+ teeth as the largest gear? I see a Suntour 13-30t
> > 7spd freewheel on Ebay and am wondering if there is
> > something with higher number of teeth on the largest
> > gear.
>
> Nashbar has 7 speed freewheels that have 32 or 34 teeth
> for the big cog. They should replace your current
> freewheel. But freewheels require special tools to take on
> and off so you would probably have to have your local shop
> do it or buy the freewheel and then go ask the shop to
> sell you the particular freewheel removal tool required.
> Probably a unique one for each freewheel.
>
> You would also have to replace your chain with a longer
> chain to fit over the big chainring and new big cog in
> back. $8 for a new cheap 7 speed chain. $25 for the
> freewheel. $10-20 for the freewheel removal tools. And $7
> for a chain whip. Pretty sure you will need a chain whip
> too for removal.
>
> Your current rear derailleur will work just fine as long
> as you stay out of certain combinations like small
> chainring and small rear cogs.
>
> http://www.nashbar.com/profile.cfm?category=87&subcategor-
> y=1109&brand=&sku=11696&storetype=&estoreid=&pagename=
>
> http://www.performancebike.com/shop/profile.cfm?SKU=15981-
> &subcategory_ID=5130
> > 2. Should I be thinking of adding a smaller ring, if
> > possible, to the two rings that I have.
>
> You may not be able to. And it would not be as good of an
> improvement as the new freewheel.

Thank you for the response. I will go with the freewheel
first. Upon reading some more about Suntour GPX, I came to
know that it has variable spacing between its freewheel
cogs. Will this Nashbar freewheel, which claims to be "SIS
compatible", be compatible with the Suntour GPX rear
derailleur's variably spaced index shifting? Or will I
have to forgo index shifting and deal with the friction
shifting mode?

Thanks, Srinivas

 

[dsr]

On 9 Jul 2004 15:33:47 -0700, [email protected] (R.
Srinivas) wrote:

>Suntour GPX

You did not mention whether your Suntour GPX is long cage or
short cage der? The short cage GPX der can handle a maximum
of 30 tooth freewheel cog. I am running a 52/39 chain ring
combination with a 28 tooth granny gear. I can't imagine
needing anything lower than a
38/28 gear combo for hills on a 5 mile ride, if you get that
tired get off and walk.

 

[R. Srinivas]

[email protected] wrote in message news:<[email protected]>...
> On 9 Jul 2004 15:33:47 -0700,
> [email protected] (R. Srinivas) wrote:
>
> >Suntour GPX
>
> You did not mention whether your Suntour GPX is long cage
> or short cage der?

As I am a newbie, I don't really know. How do I find out?
Both the rear hub and the rear derailleur say just
"Suntour GPX".

> The short cage GPX der can handle a maximum of 30
> tooth freewheel cog. I am running a 52/39 chain
> ring combination with a 28 tooth granny gear. I
> can't imagine needing anything lower than a
> 38/28 gear combo for hills on a 5 mile ride, if you get
> that tired get off and walk.

I do a lot of embarrassing things like tying a rubberband on
the ankles around my pants to prevent the ends from getting
stuck in the chainrings etc. But walking a couple of short
but steepish bridges is too embarrassing even for me.

Srinivas

 

[R. Srinivas]

[email protected] (R. Srinivas) wrote in message news:<[email protected]>...
> [email protected] wrote in message
> news:<[email protected]>...
> > On 9 Jul 2004 15:33:47 -0700,
> > [email protected] (R. Srinivas) wrote:
> >
> > >Suntour GPX
> >
> > You did not mention whether your Suntour GPX is long
> > cage or short cage der?
>
> As I am a newbie, I don't really know. How do I find out?
> Both the rear hub and the rear derailleur say just
> "Suntour GPX".

My rear derailleur has both the mechanism that moves the
chain from cog to cog as well as a small wheel whose purpose
seems to be to maintain some level of tension in the chain.
A picture of it can be found here:
http://andysbikes.com/articles/GPX/index.html Look for the
rear derailleur pictures.

Srinivas

 

[dsr]

On 10 Jul 2004 09:33:38 -0700, [email protected] (R.
Srinivas) wrote:

>[email protected] (R. Srinivas) wrote in
>message
>news:<[email protected]>...
>> [email protected] wrote in message
>> news:<[email protected]>...
>> > On 9 Jul 2004 15:33:47 -0700,
>> > [email protected] (R. Srinivas) wrote:
>> >
>> > >Suntour GPX
>> >
>> > You did not mention whether your Suntour GPX is long
>> > cage or short cage der?
>>
>> As I am a newbie, I don't really know. How do I find out?
>> Both the rear hub and the rear derailleur say just
>> "Suntour GPX".
>
>My rear derailleur has both the mechanism that moves the
>chain from cog to cog as well as a small wheel whose
>purpose seems to be to maintain some level of tension in
>the chain. A picture of it can be found here:
>http://andysbikes.com/articles/GPX/index.html Look for the
>rear derailleur pictures.
>
>Srinivas

The photo does not look like a long cage der. With a long
cage der the jockey wheels are farther apart so that more
chain length can be adjusted for. That way you don't get a
slack chain in the high gears. If worst comes to worst you
can adjust the rear der so that it stops before the 34 tooth
megarange gear. You would then have a quite useable 6 speed
bike even with the existing chain.

 

[Ted Bennett]

In article <[email protected]>,
[email protected] (R. Srinivas) wrote:

> [email protected] (R. Srinivas) wrote in
> message
> news:<[email protected]>...
> > [email protected] wrote in message
> > news:<[email protected]>...
> > > On 9 Jul 2004 15:33:47 -0700,
> > > [email protected] (R. Srinivas) wrote:
> > >
> > > >Suntour GPX
> > >
> > > You did not mention whether your Suntour GPX is long
> > > cage or short cage der?
> >
> > As I am a newbie, I don't really know. How do I find
> > out? Both the rear hub and the rear derailleur say just
> > "Suntour GPX".
>
> My rear derailleur has both the mechanism that moves the
> chain from cog to cog as well as a small wheel whose
> purpose seems to be to maintain some level of tension in
> the chain. A picture of it can be found here:
> http://andysbikes.com/articles/GPX/index.html Look for the
> rear derailleur pictures.
>
> Srinivas

You have a nice quality, short cage derailleur. "Short"
refers to the distance between the two cogs. The longer that
distance, the more chain the derailleur can wrap, and the
greater the gearing range it can manage. Sheldon brown has
lots of good info on this:
http://www.sheldonbrown.com/gloss_d.html and scroll down to
"derailer", Sheldon's preferred spelling.

--
Ted Bennett Portland OR

 

[Russell Seaton]

> Thank you for the response. I will go with the freewheel
> first. Upon reading some more about Suntour GPX, I came to
> know that it has variable spacing between its freewheel
> cogs. Will this Nashbar freewheel, which claims to be "SIS
> compatible", be compatible with the Suntour GPX rear
> derailleur's variably spaced index shifting? Or will I
> have to forgo index shifting and deal with the friction
> shifting mode?

Based on a recent thread about other brand freewheels
working with Shimano index shifters, I doubt if your
Suntour shifters and derailleur would index too well with a
Shimano compatible freewheel. It might work sort of OK
though. Nashbar is pretty good about returning stuff, so
you could try the new freewheel and see if the indexing is
good enough. If not then go friction or decide if its worth
the expense and effort to change rear derailleur and
shifters to Shimano.

As mentioned in another post, the rear derailleur top pulley
will be closer to the big cog. So you will have to screw the
B screw in all the way. And/or buy a longer B screw. And/or
have your brother build up the rear derailleur hangar tab
with a welder so the B screw can push the top pulley away
from the big cog. I did this with my Trek 520 when I put on
a 34 rear cog.

 

[David Johnson]

On Thu, 08 Jul 2004 16:59:19 -0700, R. Srinivas wrote:

> The questions I have are:
> 1. Can I replace the 13-19 freewheel with one that has 30+
> teeth as the largest gear? I see a Suntour 13-30t 7spd
> freewheel on Ebay and am wondering if there is
> something with higher number of teeth on the largest
> gear.

Probably can't go that far with a standard road bike
derailleur. Not sure what the max teeth on that
derailleur is, but my guess would be 26-28. A 26 will be
a lot better than a 19, although you might miss some of
the inbetween gears. If you switch to a Suntour MTB
derailleur, you'll have more options. You will probably
need a new (longer) chain as well, about 1 pin per extra
tooth of your biggest gear.

Another thing is that you need to learn how to stand. When
you run out if gears and have to stand, you'll want to shift
2-3 gears higher just before you stand. You can't easily
keep a sitting cadence while standing.

> 2. Should I be thinking of adding a smaller ring, if
> possible, to the two rings that I have.

Maybe, but the rear derailleur might not have enough
capacity to take all that chain slack up. This may involve a
new crank, which may in turn require a new bottom bracket
and front derailleur. I don't think a typical road crank can
take much less than a 38 tooth small ring.

Rather than buying all this stuff piecemeal, look for a used
MTB or hybrid with Suntour index parts. Keep your shifters,
move the crank, derailleurs and freewheel to your bike.

> 3. How difficult is it to do these things by myself? I
> like mucking things around by myself, but have no idea
> how good I am doing it. I managed to reverse my drop
> bar to allow me to sit more upright.

If you're going to leave it that way, you aren't allowed to
read the rest of my message....

To remove a freewheel, you'll need a tool for that
particular type of freewheel and a 1" wrench or vise. Yours
is probably a 4 prong Suntour. Shimano uses internal
splines, older Suntour is 2 prong. No special tools needed
to install a freewheel. That tool should be about $10 or
so. If it's a cassette, you'll need a similar tool and a
chain whip.

To remove a crank, you'll need a crank puller. Yours will be
the standard square taper. $15 or so, I think. Again, no
special tools to install.

> If I am able to keep it up for a while, then I will
> probably have more questions.
>
> Srinivas