Fork length question

[wolfman]

Hi everybody.

I have a Canyon Evolution bike from '95, that came out with STX cantilever brakes and with an RST 460 fork. The MCU elastomers in the fork are dead now, i had to replace them with regular springs. :? :cry:

As i started to use it, i realized, that the old STX brakes are weak, so i upgraded them to LX cantilever brakes. It's better now, but they still aren't effective enough.... So i bought a Shimano XT brakeset (BR-M739, ST-M739). Now i dont't need the brake cable support, so have to upgrade my fork too...

My RST 460's length is about 42 cm from the top of the crown to the bottom of the slider. The question is: can i buy a longer fork without causing any damage to the semi-carbon frame, or not? My headtube is made of carbon, as i can see....

I have a Marzocchi Bomber Z1 in my sight. That fork's length is 47 cm. I don't know if i can install it without damaging the frame... :shock:

Thanks for any help.




Ps.: please forgive me, if i've made some grammar mistakes, i just learn the english... :roll:

 

[wolfman]

That's my Canyon

 

[PurpleFrog]

Hi everybody.

I have a Canyon Evolution bike from '95, that came out with STX cantilever brakes and with an RST 460 fork. The MCU elastomers in the fork are dead now, i had to replace them with regular springs. :? :cry:

As i started to use it, i realized, that the old STX brakes are weak, so i upgraded them to LX cantilever brakes.

Cantis are the one part of a bike I know much about. It's hard to see that any sort of canti can be inherently weak - they're just simple levers. They ARE hard to setup however and most people do it wrong. Go the cyclocross subform at idiot.net - I mean, bikeforums - and read the canti faq there. (The cross forum is one of the few non brain damaged parts of the site.)

The big things about cantis are that you can tune them by adjusting straddle length, and most people do it wrong if they do it at al - they think that a hard definite feel is powerful, but it is really a sign of a weak brake. Powerful feel soft, because you feel the pads deforming against the rims.

You might as well as fit cheap brake boosters as well, and install a canti hanger at the front - this removes brake squeal/judder and gives finer modulation (and sometimes, perhaps, greater power.)

Superb paint job!

 

[wolfman]

Yes, they are hard to setup. That's why i changed my STX-s to LX canti brakeset. Now the setup is easier, but the good setup is still a science fiction - for me, specially since i read the articles You mentioned....

Besides that i have now the Shimano XT V-brakeset, and i'd like to try it.

 

[NeilM]

Re:

You won't damage the frame by changing the forks, provided the new forks have the same diameter steerer tube, so if your current forks are 1 1/8", then you new fork must be the same.

Steerer length is adjusted (cut) to suit your stem and riding position.

You will also need to take the crown race from the old forks and install it on the new ones.

 

[wolfman]

Thanks.

I'm afraid the angle of the fork (and so the angle of the headtuba) is changing with a 5 cm longer fork, so with the changing of the frame's geometry the longer forks increases the teadtube's load. :S

 

[KermitGKona88]

Re:

Hi Wolfman

Your grammar is very good if you have just learned

From looking at your picture of the bike the original fork seems to give a very slight negative angle, and you seem to be compensating for it with the very upright stem so I would say the extra length in the fork would probably improve the angles for you. Also remember that Marzocchi use 'negative air' so the fork will compress slightly and take up some of the slack before any suspension travel is used

 

[wolfman]

Re:

Ok, thar's right, the longer fork is good for me. The questioin is: is it good for the frame/headtube (or at least not bad)?

 

[NeilM]

Re:

I agree with what Kermit has said, and I think you will find the bike very slightly less twitchy, so, longer forks will be good for handling.

 

[xerxes]

Re:

I agree with what Kermit has said, and I think you will find the bike very slightly less twitchy, so, longer forks will be good for handling.

I'd be careful with that assumption, longer doesn't always mean less twitchy. Too long and you increase the trail and you can get issues with wheel flop, which makes the steering feel very peculiar. :?

http://en.wikipedia.org/wiki/Bicycle_an ... e_geometry

I put some rigid forks on a bicycle that were 15mm longer than the originals, thinking it wouldn't make much difference, but I was wrong and the steering felt terrible, especially at low speeds where the bicycle sort of fell into the corners. Suspension corrected frames may be more tolerant of slight differences than frames designed for rigid forks as the geometry varies as the fork extends compresses in use anyway, but I'd be inclined to fit forks with travel as close as possible to the originals as possible.