Cost effective way to increase some or all gear ratios on old 21 speed EXAGE Shimano?

[Big Dummy]

Have an old rigid MOTIV Groundpounder mountain bike with 21 speed EXAGE
Shimano gears, crank and those 1 click/gear thumb shifters. Bought the bike
at the price club for maybe $250 about 15 years ago. Rode the heck out of
it in the hills off road but now live in the flats near J'ville Fla. I do
the maintenance so it remains a one click per 21 gear bike.

Gear ratios are great for steep climbs off road, sand/mud and such but not
so good on the hard surface flat. Today I ride about 50/50 on flat hard
roads or off road trails.

Is there a cost effective way to increase the gear ratio to maybe 30% fewer
crank rotations per mph?

BD

 

[Dave Thompson]

Big Dummy wrote:
> Have an old rigid MOTIV Groundpounder mountain bike with 21 speed
> EXAGE Shimano gears, crank and those 1 click/gear thumb shifters.
> Bought the bike at the price club for maybe $250 about 15 years ago.
> Rode the heck out of it in the hills off road but now live in the
> flats near J'ville Fla. I do the maintenance so it remains a one
> click per 21 gear bike.
>
> Gear ratios are great for steep climbs off road, sand/mud and such
> but not so good on the hard surface flat. Today I ride about 50/50
> on flat hard roads or off road trails.
>
> Is there a cost effective way to increase the gear ratio to maybe 30%
> fewer crank rotations per mph?
>
> BD
Several different ways, depending on your definition of 'cost effective'.
Some might say you've received more than fair value for the last 15 years,
you could throw the bike away and buy a new one, which in a sense could be
considered cost effective.

Otherwise, a larger rear tire and/or a freewheel with smaller cogs and/or
smaller chain rings are pretty much the ways to change your gear ratios.
Chainrings and freewheels are probably less expensive than a rear tire, and
would do more for you.

 

[[email protected]]

Big Dummy wrote:
> Have an old rigid MOTIV Groundpounder mountain bike with 21 speed
EXAGE
> Shimano gears, crank and those 1 click/gear thumb shifters. Bought
the bike
> at the price club for maybe $250 about 15 years ago. Rode the heck
out of
> it in the hills off road but now live in the flats near J'ville Fla.
I do
> the maintenance so it remains a one click per 21 gear bike.
>
> Gear ratios are great for steep climbs off road, sand/mud and such
but not
> so good on the hard surface flat. Today I ride about 50/50 on flat
hard
> roads or off road trails.
>
> Is there a cost effective way to increase the gear ratio to maybe 30%
fewer
> crank rotations per mph?
>
> BD

As already stated, you can get harder gears by getting smaller cogs on
your 7 speed freewheel or cassette, OR getting bigger chainrings on
your crankset. Check Nashbar for 7 speed freewheels and cassettes.
They come with 12 or 13 tooth small cogs. A freewheel might be limited
to 13 small cog. But a 13 small cog in the back will provide you a
hard enough gear unless you are pedaling down a mountain. Other way is
to install larger chainrings on your current crankset if this is
possible. A 15 year old low cost bike may have come with non
replaceable chainrings. Not sure. If you can replace chainrings, then
consider just putting a bigger ring on the outside only. Or put a new
larger outer ring on and move your current outer ring to the middle and
keep the very small inner ring. If chainrings are not replaceable,
then consider a new crank and bottom bracket. You can watch for sales
at Nashbar and pick up crank and bottom bracket for $70 total at most.
Probably less if you are diligent. Not super cheap but it will solve
your problem. Just make sure the new crank has a larger outer ring.

 

[Conniebiker]

Changing to something like a newer casette hub instead of a freewheel is about the most effective. decreasing the number of teeth on the rear gears has roughly double the effect of adding teeth on the chainrings.