Rear axle and spacers

Need advice from anyone used to workign with wheels. I snapped an axle
and did some other damage to a rear wheel on my MTB. I swapped my
casette ( a 5 speed about 8 years old) onto a spare wheel donated to me
but when I went to put the wheel on the bike it wouldn't fit. There was
a big spacer on the axle on the new wheel so I removed that and the
wheel would now fit into the frame. But I can't shift down to the
smallest sprocket, I'm about one sprocket out for the SDI change. Does
that mean I need a spacer just a smaller one. I don't understand the
purpose of the spacer but it seems to do something vital??

DaveB

On Sat, 07 Aug 2004 17:26:08 +1000, DaveB wrote:

Need advice from anyone used to workign with wheels. I snapped an axle
and did some other damage to a rear wheel on my MTB. I swapped my
casette ( a 5 speed about 8 years old) onto a spare wheel donated to me
but when I went to put the wheel on the bike it wouldn't fit. There was
a big spacer on the axle on the new wheel so I removed that and the
wheel would now fit into the frame. But I can't shift down to the
smallest sprocket, I'm about one sprocket out for the SDI change. Does
that mean I need a spacer just a smaller one. I don't understand the
purpose of the spacer but it seems to do something vital??

OK, there are several issues here. The donated wheel, meant for a newer
bike, was set up for wider spacing in the back. But the wheel was built
with the center of the rim exactly at the midpoint between the ends of the
frame. Taking the spacer out will let the axle fit, but the rim will be
way too far to the right.

I am also guessing that the wheel must attach with nuts, rather than a
quick-release, or you would not be able to tighten it down after removing
the spacer.

You can remove spacers from both sides (if there are any on the left) to
make it skinny enough to fit but still centered. Or, you can re-dish the
wheel, which takes some work.

--

David L. Johnson

__o | The lottery is a tax on those who fail to understand
_`\(,_ | mathematics.
(_)/ (_) |

David L. Johnson wrote:

OK, there are several issues here. The donated wheel, meant for a newer
bike, was set up for wider spacing in the back. But the wheel was built
with the center of the rim exactly at the midpoint between the ends of the
frame. Taking the spacer out will let the axle fit, but the rim will be
way too far to the right.

Yep that's what I'm seeing.


I am also guessing that the wheel must attach with nuts, rather than a
quick-release, or you would not be able to tighten it down after removing
the spacer.

No it's got a quick release (the old one didn't) and I can tighten it
down (with the spacer removed).


You can remove spacers from both sides (if there are any on the left) to
make it skinny enough to fit but still centered. Or, you can re-dish the
wheel, which takes some work.


Unfortunately no spacers on the left to remove. Doesn't make sense to
me. I end up with about 3 times as much axle out the right side as the
left. Would it make a difference if I removed the axle and loosened the
cone on the right side and tightened on the left to end up with similar
amounts of "overhang"?

DaveB

DaveB wrote:

Need advice from anyone used to workign with wheels. I snapped an axle
and did some other damage to a rear wheel on my MTB. I swapped my
casette ( a 5 speed about 8 years old) onto a spare wheel donated to me
but when I went to put the wheel on the bike it wouldn't fit. There was
a big spacer on the axle on the new wheel so I removed that and the
wheel would now fit into the frame. But I can't shift down to the
smallest sprocket, I'm about one sprocket out for the SDI change. Does
that mean I need a spacer just a smaller one. I don't understand the
purpose of the spacer but it seems to do something vital??

DaveB

OK You get style points for being intrepid.

The thing you moved was a freewheel, not a cassette. There
are various formats for freewheel hubs to accommodate
various freewheels. A five speed system such as your
original should be 120mm overall and 30mm from the inside of
your frame on the right side to the bottom of the freewheel
thread.

Your modern XMart type wheel is 135mm overall and usually
40mm from the thread base to the frame for an 8speed
freewheel. That's why it was hard to jam into your 120mm frame.

When you overreacted and removed the axle spacer, there
wasn't anything keeping the freewheel from grinding against
the frame so you lost chain clearance in high gear. Axle
spacer(s) come in various lengths to adjust that.

Ideally you could rearrange the spacing on both sides to
give 120mm/30mm and then recenter the rim over the locknuts .
Alternately, if you just pull your frame apart the requisite
amount, reassemble the new wheel's axle set the way you
found it and adjust from there, you'll avoid a lot of
complexities.

Grease the freewheel thread. Add grease to the axle
bearings. Adjust such that the axle spins freely with no
sideplay. Shift the derailleur with your thumb and set the
stops ( screws marked H and L) before connecting the gear wire.

--
Andrew Muzi
www.yellowjersey.org
Open every day since 1 April, 1971

see the local bike rebuilder/junkman-at the flea market?-he has a box
filled with freewheel spacers.