Fork Measurement

Rob <[email hidden]> typed:

Quoted message said:

http://patchoulian.googlepages.com/bike

Is it something at/around AC and BC?

AC is the steerer tube length you need to buy.

IMHO I'd get one that length or longer, they are easy to cut with a hacksaw
down to size, but are a pain if you get one too short.

Dry fit it to get the stack size, (No of washers needed to hold stem on) and
make sure all is OK. Cut steerer tube to correct length, which should be a
couple mm under AC so that there's room for the system to clamp down.

Re-fit it all with grease, washers, stem as required.

I would always recommend using a brand new Star-Fangled nut, it's not worth
the cost to re-use an old one.

--
Paul - [censored]

"Rob" <[email hidden]> a écrit:

Quoted message said:

Following from the fork replacement thread, and the decision
to fit some rigid forks, I'm trying to figure out the size required
without removing the existing gubbins. The reason is that there's
quite a few on ebay that have been cut to size, and I wouldn't mind
picking a set up and still keep my bike on the road until they
arrive.

I've put a pic at the bottom of this page:

http://patchoulian.googlepages.com/bike

Is it something at/around AC and BC?

AC gives you (roughly) the steerer length. The steerer stops just short of
the top of the stem. You can take out the headset top-cap (it's not doing
anything as long as the stem remains clamped) and have a look inside. At the
bottom of the steerer, the measurement is taken from the bearing seat of the
fork crown. You can get away with a slightly shorter steerer (with a lower
handlebar, obviously) by taking out the two black spacers under the stem.

You also need to consider the length of the fork blades. Most older
"suspension corrected" frames need a fork with an axle-to-crown measurement
of around 410mm, give or take. Newer frames are often made for longer forks.

James Thomson

"Rob" <[email hidden]> a écrit:

Quoted message said:

Following from the fork replacement thread, and the decision
to fit some rigid forks, I'm trying to figure out the size required
without removing the existing gubbins. The reason is that there's
quite a few on ebay that have been cut to size, and I wouldn't mind
picking a set up and still keep my bike on the road until they
arrive.

I've put a pic at the bottom of this page:

http://patchoulian.googlepages.com/bike

Is it something at/around AC and BC?

AC gives you (roughly) the steerer length. The steerer stops just short of
the top of the stem. You can take out the headset top-cap (it's not doing
anything as long as the stem remains clamped) and have a look inside. At the
bottom of the steerer, the measurement is taken from the bearing seat of the
fork crown. You can get away with a slightly shorter steerer (with a lower
handlebar, obviously) by taking out the two black spacers under the stem.

You also need to consider the length of the fork blades. Most older
"suspension corrected" frames need a fork with an axle-to-crown measurement
of around 410mm, give or take. Newer frames are often made for longer forks.

James Thomson

James Thomson said:

"Rob" <[email hidden]> a écrit:

Quoted message said:

Following from the fork replacement thread, and the decision
to fit some rigid forks, I'm trying to figure out the size required
without removing the existing gubbins. The reason is that there's
quite a few on ebay that have been cut to size, and I wouldn't mind
picking a set up and still keep my bike on the road until they
arrive.

I've put a pic at the bottom of this page:

http://patchoulian.googlepages.com/bike

Is it something at/around AC and BC?

AC gives you (roughly) the steerer length. The steerer stops just short of
the top of the stem. You can take out the headset top-cap (it's not doing
anything as long as the stem remains clamped) and have a look inside. At the
bottom of the steerer, the measurement is taken from the bearing seat of the
fork crown. You can get away with a slightly shorter steerer (with a lower
handlebar, obviously) by taking out the two black spacers under the stem.

You also need to consider the length of the fork blades. Most older
"suspension corrected" frames need a fork with an axle-to-crown measurement
of around 410mm, give or take. Newer frames are often made for longer forks.

James Thomson

Thanks very much both - got it now. AC is 205mm - most of the ebay
offerings are around 170mm - probably why they're on ebay ;-)

40UKP from Wiggle won't break the bank so I'll go with that - the only
ones in stock are:

http://www.wiggle.co.uk/Productdetail.aspx?W=0&Cat=cycle&UberCat=0&ProdID=5360008401

The 100mm is a reference to suspension travel I'd guess, and a longer
fork (if it proves to be) can be compensated for by removing the spacers.

Cheers, Rob

"Rob" <[email hidden]> a écrit:

Quoted message said:

40UKP from Wiggle won't break the bank so I'll go with that -
the only ones in stock are:

http://www.wiggle.co.uk/Productdetail.aspx?W=0&Cat=cycle&UberCat=0&ProdID=5360008401

Quoted message said:

The 100mm is a reference to suspension travel I'd guess, and
a longer fork (if it proves to be) can be compensated for by
removing the spacers.

That's not the whole story. A longer fork also changes the head and seat
angles, which will change your riding position and affect the handling of
the bike.

The fork on your Giant looks more like an 80mm fork than a 100mm fork. I'd
have a look around and see if you can find something a touch shorter.

James Thomson

Rob <[email hidden]> typed:

Quoted message said:

James Thomson said:

"Rob" <[email hidden]> a écrit:

Quoted message said:

Following from the fork replacement thread, and the decision
to fit some rigid forks, I'm trying to figure out the size required
without removing the existing gubbins. The reason is that there's
quite a few on ebay that have been cut to size, and I wouldn't mind
picking a set up and still keep my bike on the road until they
arrive.

I've put a pic at the bottom of this page:

http://patchoulian.googlepages.com/bike

Is it something at/around AC and BC?

AC gives you (roughly) the steerer length. The steerer stops just short
of the top of the stem. You can take out the headset top-cap (it's not
doing anything as long as the stem remains clamped) and have a look
inside. At the bottom of the steerer, the measurement is taken from the
bearing seat of the fork crown. You can get away with a slightly shorter
steerer (with a lower handlebar, obviously) by taking out the two black
spacers under the stem. You also need to consider the length of the fork
blades. Most older
"suspension corrected" frames need a fork with an axle-to-crown
measurement of around 410mm, give or take. Newer frames are often made
for longer forks. James Thomson

Thanks very much both - got it now. AC is 205mm - most of the ebay
offerings are around 170mm - probably why they're on ebay ;-)

40UKP from Wiggle won't break the bank so I'll go with that - the only
ones in stock are:

http://www.wiggle.co.uk/Productdetail.aspx?W=0&Cat=cycle&UberCat=0&ProdID=5360008401

The 100mm is a reference to suspension travel I'd guess, and a longer
fork (if it proves to be) can be compensated for by removing the spacers.

I agree totally with what JT replied but would add that adding longer forks
_will_ change the characteristics of the ride. Some might like it, YMMV. I
did like it. It made the ride on my bike more 'relaxed', slightly harder to
turn, but also less likely to get knocked off course by a stone or tree
root. The differences on my bike (Old-school steel hard-tail, Dyna-Tech
Cro-Mo comp) when I went with a 100 instead of 80mm fork turned my bike from
being a tad skittish to one that was much easier to control. In fact I also
lost a bit of weight too .. well, the bike lost a few grammes .. 😉

One other thing to consider is the axle placement. If your current forks
have the axle in-line with the fork leg centre-line and you change to a fork
that has the axle slightly in front of the leg centre-line then the above
effect can also be heightened.

Trouble is, the only way you'll know is by doing it ... 😉

--
Paul - [censored]

Paul - censored said:

Rob <[email hidden]> typed:

Quoted message said:

James Thomson said:

"Rob" <[email hidden]> a écrit:

> Following from the fork replacement thread, and the decision
> to fit some rigid forks, I'm trying to figure out the size required
> without removing the existing gubbins. The reason is that there's
> quite a few on ebay that have been cut to size, and I wouldn't mind
> picking a set up and still keep my bike on the road until they
> arrive.
>
> I've put a pic at the bottom of this page:
>
> http://patchoulian.googlepages.com/bike
>
> Is it something at/around AC and BC?
AC gives you (roughly) the steerer length. The steerer stops just short
of the top of the stem. You can take out the headset top-cap (it's not
doing anything as long as the stem remains clamped) and have a look
inside. At the bottom of the steerer, the measurement is taken from the
bearing seat of the fork crown. You can get away with a slightly shorter
steerer (with a lower handlebar, obviously) by taking out the two black
spacers under the stem. You also need to consider the length of the fork
blades. Most older
"suspension corrected" frames need a fork with an axle-to-crown
measurement of around 410mm, give or take. Newer frames are often made
for longer forks. James Thomson

Thanks very much both - got it now. AC is 205mm - most of the ebay
offerings are around 170mm - probably why they're on ebay ;-)

40UKP from Wiggle won't break the bank so I'll go with that - the only
ones in stock are:

http://www.wiggle.co.uk/Productdetail.aspx?W=0&Cat=cycle&UberCat=0&ProdID=5360008401

The 100mm is a reference to suspension travel I'd guess, and a longer
fork (if it proves to be) can be compensated for by removing the spacers.

I agree totally with what JT replied but would add that adding longer forks
_will_ change the characteristics of the ride. Some might like it, YMMV. I
did like it. It made the ride on my bike more 'relaxed', slightly harder to
turn, but also less likely to get knocked off course by a stone or tree
root. The differences on my bike (Old-school steel hard-tail, Dyna-Tech
Cro-Mo comp) when I went with a 100 instead of 80mm fork turned my bike from
being a tad skittish to one that was much easier to control. In fact I also
lost a bit of weight too .. well, the bike lost a few grammes .. 😉

One other thing to consider is the axle placement. If your current forks
have the axle in-line with the fork leg centre-line and you change to a fork
that has the axle slightly in front of the leg centre-line then the above
effect can also be heightened.

Trouble is, the only way you'll know is by doing it ... 😉

Blimey, the plot thickens :-)

Thanks everso for the advice. I'm going to have a proper measure of all
the bits and pieces and get what seems similar geometry/size-wise.

Rob