Replacement bottom bracket for a Dawes Horizon (2005)

D.M. Procida said:

I've worn out my bottom bracket. I have no idea what a suitable
replacement might be - any suggestions?

Thanks,

Daniele

Shimano UN52 of the same length you currently have fitted or if not
square taper, then maybe the next grade up on what is fitted

Pete Whelan said:

Quoted message said:

I've worn out my bottom bracket. I have no idea what a suitable
replacement might be - any suggestions?

Quoted message said:

Shimano UN52 of the same length you currently have fitted or if not
square taper, then maybe the next grade up on what is fitted

Right... so how would I find out what length it is without taking it
out? Or indeed whether it has a square taper?

Daniele

D.M. Procida said:

Pete Whelan said:

Quoted message said:

I've worn out my bottom bracket. I have no idea what a suitable
replacement might be - any suggestions?

Quoted message said:

Shimano UN52

or UN53 or UN72 or UN73

Quoted message said:

Quoted message said:

of the same length you currently have fitted or if not
square taper, then maybe the next grade up on what is fitted

Right... so how would I find out what length it is without taking it
out? Or indeed whether it has a square taper?

Length of axle can be measured by taking the cranks off (which you will
probably need a special tool for). Hopefully someone will save you doing
that by knowing what is fitted to your bike (which would be possible as you
have mentioned the model and year). Sorry I don't know.

Make or model of cranks will indicate whether it's a square taper type.

~PB

On Tue, 6 May 2008 21:29:35 +0100,

(D.M. Procida) said:

Pete Whelan said:

Quoted message said:

I've worn out my bottom bracket. I have no idea what a suitable
replacement might be - any suggestions?

Quoted message said:

Shimano UN52 of the same length you currently have fitted or if not
square taper, then maybe the next grade up on what is fitted

Right... so how would I find out what length it is without taking it
out?

umm, measure it. Which is a bit tricky, as the bike frame gets in the
way. Remove the cranks (crank extractor needed), and then put a set
of calipers over the axle ends.

Quoted message said:

Or indeed whether it has a square taper?

The axle will be square section when viewed end on. Unfortunatly
thereare two standards (same taper angle, different start dimensions).
Most are JIS (Japanee Industrial Standard) some are ISO.

TLGSHTA: <http://www.sheldonbrown.com/bbtaper.html>

--

Tim

I understand very little of what's being discussed
but for some reason it's fascinating.

(Jon Thompson, urs)

D.M. Procida said:

Quoted message said:

Quoted message said:

I've worn out my bottom bracket. I have no idea what a suitable
replacement might be - any suggestions?

Quoted message said:

Shimano UN52 of the same length you currently have fitted or if not
square taper, then maybe the next grade up on what is fitted

Right... so how would I find out what length it is without taking it
out? Or indeed whether it has a square taper?

OK, I've done a bit more investigating.

First, I can see something that looks as though this tool:

<http://www.parktool.com/products/detail.asp?cat=25&item=BBT-22>

will fit into. Does that give any useful information about what kind of
bottom bracket it is?

I have one of those tools in my toolset.

Unfortunately, I can't tell for certain whether it will fit, because I
can't get the cranks off. I have a crank-pulling tool, but having
tightened it as tight as it will go, nothing has budged.

Second, the axle is square - is this what is meant by a square taper? It
looks somewhat like this:

<http://www.parktool.com/images_inc/repair_help/crank04.jpg>

Finally, according to the Dawes website, newer versions of the same bike
are listed as having Shimano bottom brackets.

I don't know if this is useful in identifying what's likely to be on
there.

Daniele

D.M. Procida said:

OK, I've done a bit more investigating.

First, I can see something that looks as though this tool:

<http://www.parktool.com/products/detail.asp?cat=25&item=BBT-22>

will fit into. Does that give any useful information about what kind
of bottom bracket it is?

Not unless sure that is the exact tool that would fit.

Quoted message said:

I have one of those tools in my toolset.

Unfortunately, I can't tell for certain whether it will fit, because I
can't get the cranks off. I have a crank-pulling tool, but having
tightened it as tight as it will go, nothing has budged.

It's a two-part process. See the instructions on Park Tools.

Quoted message said:

Second, the axle is square - is this what is meant by a square taper?

Yes, so we're getting there.

We can find out what the axle length /probably/ is just from the model of
cranks. Are they marked with a name or number? Look on the back as well as
front.

~PB

On Tue, 6 May 2008 23:36:14 +0100,

(D.M. Procida) said:

OK, I've done a bit more investigating.

First, I can see something that looks as though this tool:

<http://www.parktool.com/products/detail.asp?cat=25&item=BBT-22>

will fit into. Does that give any useful information about what kind of
bottom bracket it is?

A little. It's not some fancy off the wall make.

Quoted message said:

I have one of those tools in my toolset.

And you have the tool with which to remove it.

Quoted message said:

Unfortunately, I can't tell for certain whether it will fit, because I
can't get the cranks off. I have a crank-pulling tool, but having
tightened it as tight as it will go, nothing has budged.

(Grandmother, eggs etc.)

There are two bits to tighten: the first attaches the tool very firmly
to the crank, the second then pushes the crank off the end of the
axle. If you've done that bit right and it still doesn't shift, try a
bit of Plus Gas and waiting overnight. Or a bit of gentle heat.

And make sure you've removed the crank bolt (or in some cases, nut)
first.

Quoted message said:

Second, the axle is square - is this what is meant by a square taper? It
looks somewhat like this:

<http://www.parktool.com/images_inc/repair_help/crank04.jpg>

Yes.

Quoted message said:

Finally, according to the Dawes website, newer versions of the same bike
are listed as having Shimano bottom brackets.

So it's likely to be JIS.

Quoted message said:

I don't know if this is useful in identifying what's likely to be on
there.

Still need to measure it.

--

Tim

I understand very little of what's being discussed
but for some reason it's fascinating.

(Jon Thompson, urs)

On May 6, 11:36 pm, [email hidden] (D.M.

Procida) said:

Unfortunately, I can't tell for certain whether it will fit, because I
can't get the cranks off. I have a crank-pulling tool, but having
tightened it as tight as it will go, nothing has budged.

Be careful here as you have the potential to destroy your cranks. The
pulling tool has two parts, a body that screws into the crank, and an
inner part that screws into the tool.

Make sure the inner part is unscrewed almost all the way out before
you screw the tool into the crank. Then make sure the body of the tool
is all the way into the crank. Only then should you screw in the inner
part. There will be some temporary resistance then the crank should
come off easily. If the body if the tool is only a few threads in it
will strip the threads from the crank then you will be in for a torrid
time.

--
Dave...

Tim Hall said:

There are two bits to tighten: the first attaches the tool very firmly
to the crank, the second then pushes the crank off the end of the
axle. If you've done that bit right and it still doesn't shift, try a
bit of Plus Gas and waiting overnight. Or a bit of gentle heat.

Having left it overnight with penetrating oil, still nothing has budged.

I've tried again, as hard as I dare. I'll try heating up the crank with
a hot air gun next.

Daniele

D.M. Procida said:

Quoted message said:

There are two bits to tighten: the first attaches the tool very firmly
to the crank, the second then pushes the crank off the end of the
axle. If you've done that bit right and it still doesn't shift, try a
bit of Plus Gas and waiting overnight. Or a bit of gentle heat.

Having left it overnight with penetrating oil, still nothing has budged.

I've tried again, as hard as I dare. I'll try heating up the crank with
a hot air gun next.

Nothing. I'm either going to damage the bike, the tool or myself if I
try any harder.

Should I try a blowtorch instead of a hot air gun?

Daniele

D.M. Procida writtificated

Quoted message said:

Nothing. I'm either going to damage the bike, the tool or myself if I
try any harder.

Should I try a blowtorch instead of a hot air gun?

Speaking as someone who does as much of his own mechanicing as possible,
I'd throw it at the bike shop to do if it reached this point.

Mark T said:

D.M. Procida writtificated

Quoted message said:

Nothing. I'm either going to damage the bike, the tool or myself if I
try any harder.

Should I try a blowtorch instead of a hot air gun?

It would be more effective.

Quoted message said:

Speaking as someone who does as much of his own mechanicing as
possible, I'd throw it at the bike shop to do if it reached this
point.

I'd try a hammer first, seriously. Bash end of spanner with club hammer.

~PB

Daniele, What is the model of crank?

Once this is known you could just buy the BB length that is normally
recommended for the crankset.

~PB

D.M. Procida said:

Phew. I gave it one more try, using all my strength (looking at other
tools for the same purpose I saw they had much longer levers. So I
took a chance, and piled it on) and off it came.

Now, the bottom bracket is a PowerPro Components BB-7420 BCI.37x24T.

Underneath it says:

L < 68 > R

so I presume that means it's 68mm wide.

68mm is the shell width. You still need to know the axle length, which will
be a hundred and something mm.

Quoted message said:

I guess I can find soomething suitable now - which of the numbers
above are the important ones to look out for?

68mm. The 37x24 means it is a "British" thread.

~PB

Pete Biggs said:

Quoted message said:

Now, the bottom bracket is a PowerPro Components BB-7420 BCI.37x24T.

Underneath it says:

L < 68 > R

so I presume that means it's 68mm wide.

68mm is the shell width. You still need to know the axle length, which will
be a hundred and something mm.

It's 113mm.

The chainset is a triple.

As far as I can tell, this is the bracket (though it's under a different
brand name):

<http://www.allproducts.com/manufacture6/th/01bb-7420.html>

"BB-7420 is compatible with Shixxxo UN-40"

Even in 68/113mm, there are two choices at:

<http://wiggle.co.uk/ProductDetail.aspx?Cat=cycle&ProdID=5360027179&N=Sh
imano%20UN54%20Tapered%20Bottom%20Bracket>

but only one at:

<http://www.chainreactioncycles.com/Models.aspx?ModelID=17473>

So complicated!

Daniele

D.M. Procida said:

It's 113mm.

Hooray, you now have all the info you need.

Quoted message said:

The chainset is a triple.

As far as I can tell, this is the bracket (though it's under a
different brand name):

<http://www.allproducts.com/manufacture6/th/01bb-7420.html>

"BB-7420 is compatible with Shixxxo UN-40"

Even in 68/113mm, there are two choices at:

<http://wiggle.co.uk/ProductDetail.aspx?Cat=cycle&ProdID=5360027179&N=Sh
imano%20UN54%20Tapered%20Bottom%20Bracket>

"BB Mount" is to do with a fixing for the front derailleur. So you don't
need a "BB Mount" version if your front derailleur is attached to the bike
frame or a bracket on the frame - *unlike* this:
http://www.cyclesuk.com/0-447934

Quoted message said:

but only one at:

<http://www.chainreactioncycles.com/Models.aspx?ModelID=17473>

That's bound to be OK.

~PB

Pete Biggs said:

Quoted message said:

<http://www.chainreactioncycles.com/Models.aspx?ModelID=17473>

That's bound to be OK.

Fantastic, many thanks.

Daniele