Let´s say I want a new frame and fit it with a 100 mm fork.But the manufacturer says is designed for 80 mm forks. Well, let´s say then that i adjust the fork with about a 20% sag(which is recomended anyway) and..voilà ! 80 mm when me on the bike.Is this correct?

Let´s say I want a new frame and fit it with a 100 mm fork.But the manufacturer says is designed for 80 mm forks. Well, let´s say then that i adjust the fork with about a 20% sag(which is recomended anyway) and..voilà ! 80 mm when me on the bike.Is this correct?

No. If the frame was designed for an 80mm fork, then the sag was also taken into consideration. Many manufacturers will allow a 100mm fork on a bike designed for 80mm.

I have a FS bike designed for an 80mm fork. I currently run a 105mm Marzocchi fork....with the bike mfgr. blessing. I prefer the less twitchy ride I get with the longer fork.

WarrGuru: why do you get a less twitchy ride? Seems like added height to front end (I think fork recommendations have to do with axle to crown distance as much or more than travel) would move weight to rear making bike more twitchy on climbs anyway. Your thoughts appreciated. Thanks

WarrGuru: why do you get a less twitchy ride? Seems like added height to front end (I think fork recommendations have to do with axle to crown distance as much or more than travel) would move weight to rear making bike more twitchy on climbs anyway. Your thoughts appreciated. Thanks

taller fork = slacker angles = less twitchy-ness

I see the light. Thanks.

I would not worry about 20mm. Ten+ years ago most bike came with rigid forks and were in no way compensated for taller suspension forks. Adding a suspension fork to most frames from that time easily raised the front of the bike an inch or more (1"=25.4mm). I did that with several bikes and never had any poor handling problems. And as Warrguru said, most newer frames are ok with 100mm forks. My 2001 Ibis Ripley is designed for an 80mm fork but it says right in the manual that 100mm is also fine.