Front Suspension Advice

This is a post from alt.mountain-bike that I thought to post here also.

I was reading an earlier post on front suspension advice and have a related question. My bike is a
'97 Diamondback Zetec 2.1 with a 97 Judy C Rockshox fork. I replaced the spring and spacer to tune
the fork to my weight and taste but don't like it anyway.

The question is if I could find something to upgrade the front suspension without altering the
geometry of the bike.The current forks have only 63mm of travel.Would a fork with 85mm or 105mm like
on a Marzocchi I was looking at be incompatible with the geometry of the bike.

Any advice would be greatly appreciated.

Fredzep

 

> Would a fork with 85mm or 105mm like on a Marzocchi I was looking at be incompatible with the
> geometry of the bike.

Think you would do fine with an airshock set with proper sag, i.e., some 20-25 percent.

Per http://user.tninet.se/~ipg289h/fu99/MTB.html

 

> The question is if I could find something to upgrade the front suspension without altering the
> geometry of the bike.The current forks have only 63mm of travel.Would a fork with 85mm or 105mm
> like on a Marzocchi I was looking at be incompatible with the geometry of the bike.
>
It depends entirely on what the axle to crown of your Judy C compared to the axle to crown
measurement of the fork you're looking at. If for example, they are the same then the geometry
wouldn't change one bit regardless of travel. Different fork manufacturers have different a-c
measurements for the same travel. So you will have a good idea of which fork is going to affect the
handling of your bike the least by comparing a-c measurements.

Each 10mm difference is roughly 1 degree. Hence if your new fork's a-c measurement is 20mm more, it
would result in a 2 degree slacker head angle. This would effectively slow the steering, when you go
up hills there will be a greater tendency for wheel flop or wander.

An 80mm travel fork probably wouldn't be so bad on your bike, a 105mm travel fork however will
make it feel like a chopper. You can always get a Rock Shox SID that can adjust between 63 mm and
80 mm and pick the one that suits you the best. There are also forks that will go from
80-100-120mm and back.

alan

 

"Per Löwdin" <[email protected]> wrote:

>> Would a fork with 85mm or 105mm like on a Marzocchi I was looking at be incompatible with the
>> geometry of the bike.
>
>Think you would do fine with an airshock set with proper sag, i.e., some 20-25 percent.

Remember that the geometry of his bike assumes that the 63mm shock is sagging the same
percentage as well.

A shock with more height will affect the handling of the bike, but whether that's a good or bad
thing depends on your "mission statement" for the bike. The slacker resultant head tube angle and
slightly higher bottom bracket height are both good things when bombing down a high speed rock
garden. They both hurt desparate, out of the saddle twisty climbing. Like everything about an MTB,
it's a compromise that all depends on what you're doing with the bike.

In the end, lots of people have made the change and have done just fine. I'd suggest looking for a
fork with no more than ~85mm of travel though just to minimize the change in handling you'll
experience.

Mark Hickey Habanero Cycles http://www.habcycles.com Home of the $695 ti frame

 

> Remember that the geometry of his bike assumes that the 63mm shock is sagging the same percentage
> as well.

I took into account that it was a Judy from 97 which probably does not have much sag. On the other
hand Marzocchis are know to be longlegged, ride on myself, i.e., have a long distance between the
axle and the crown, a Manitou 100 mm may be a better choice. I exchanged an 80 mm Manitou for a 100
mm on my Fisher and can´t say I noticed any drawbacks.

Per http://user.tninet.se/~ipg289h/English.html

 

[email protected] (Alan) wrote:

> An 80mm travel fork probably wouldn't be so bad on your bike, a 105mm travel fork however will
> make it feel like a chopper.

Ha! Yours is the idle speculation of a layman (lame-man?) who has never ridden a chopper!

Choppers have no peers among civilian bicycles! The OP's bike might need a 105mm travel fork,
affixed to the top of a 27" road bike fork, sporting a 12" kid bike wheel, to exhibit handling
characteristics that could accurately be called "chopperific".

"A little iffy" does not describe the ride of a true chopper. Say "treacherous", "mystical",
"re-educational" or "backwards", and you begin to enter the playing field. Some mighty choppers can
only be ridden by the brave souls who built them, such is their power!

For a comprehensive online sampler, consult http://www.dclxvi.org/chunk/meet/index.html

Chalo Colina full color member Dead Baby Bikes Seattle WA

 

"Per Löwdin" <[email protected]> wrote in message news:nAx%[email protected]...

> > Remember that the geometry of his bike assumes that the
63mm shock is
> > sagging the same percentage as well.
>
> I took into account that it was a Judy from 97 which
probably does not have
> much sag. On the other hand Marzocchis are know to be
longlegged, ride on
> myself, i.e., have a long distance between the axle and
the crown, a Manitou
> 100 mm may be a better choice. I exchanged an 80 mm
Manitou for a 100 mm on
> my Fisher and can´t say I noticed any drawbacks.

All the Marzocchis I've checked are about half an inch taller for the same amount of travel vs.
Rockshox or Manitou.

Matt O.

 

Thanks for the advice.

 

Thanks to everyone who replied.

 

> Ha! Yours is the idle speculation of a layman (lame-man?) who has never ridden a chopper!
>
That's true, I've never ridden a chopper but have seen them and admit I don't quite understand the
whole point.

I just wanted to warn him that riding a bike not designed for such a long travel fork is not going
to be much fun unless the bike is pointing downhill all the time.

>
> Some mighty choppers can only be ridden by the brave souls who built them, such is their power!
>
To each his own I suppose. The only chopper I'd ride is one that has Harley Davidson stamped
on the side!

alan