How much will changing forks change geometri?

[HappyCamper]

Hi.

Have a 1996 fs m2 with " stock' Judy Xc and I bought a donor bike for parts.( yeti asl) Question is how much will the travel length from the Reba with 10cm change the ride quality?

 

[joglo]

The axis to top of crown height of the Reba will be approx. 4cm higher compared to the Judy.
That's to me a bit too much as not just front height but also bottom braket height and angles are slightly changing too.
Also the center of gravity is moving slightly up and back.

Others may say it's still OK, you may not notice a negative impact.
End of day you have to try it and decide on your own...

Newer Rockshox forks do have so-called all-travel spacer, maybe this one too, but you have to check.
If so, by adding additional spacer the travel could be adjusted to 80mm too.

 

[Splatter Paint]

Personally, I think it’ll ride like a chopper. I’ve tried 100mm forks on my retros and it just doesn’t feel right. I go for 80mm travel Fox Forx and run a fair amount of static sag, this worked on my ‘95 DBR titanium and also my HeiHei.

 

[M-Power]

+\- 10mm A-C change = ~ 1deg change in geometry from ‘std set up’. Too much ^ in A-C = more Chopper like handling or increased steering/handling ‘Twitchiness’ if vice versa. As member above, I have experimented and geometry has a huge effect on how a bike rides/handles.

 

[joglo]

indeed if you want to use a more modern suspension fork in an old bike I would recommend to first of all look for one with very low A-C height, like SID before ~ 2000 with 63mm travel, which is depending on exact model just 455mm, or Skareb/R7 with 80mm which are also just 45-46cm.
Than also run those with as max as possible SAG, that the A-C difference compared to old fork is <2cm.

But some users may say that by having a higher fork you get not just more comfort by the better performing fork, but also better comfort as the front comes higher and even a bit more modern geometry with more rake, better for higher speeds and downhill.
Also objectivly our bikes from the 90ties had a rather race and uphill oriented geometry, which isn't fitting every rider (any longer).

Still, as other said above already, too extreme changes may lead to an negative impact on riding handle.

 

[HappyCamper]

I was afraid of the chopper feeling so at least I have got that confirmed.... Guess it will hang on the wall with the Yeti

 

[M-Power]

Manitou 1 forks had very little travel maybe 20-25mm ( after a bit of sag depending on elastomer hardness and rider weight) so wont change the geometry too much.

 

[Takingabreak]

I was afraid of the chopper feeling so at least I have got that confirmed.... Guess it will hang on the wall with the Yeti

You may as well try it and see if you like it.

 

[ishaw]

I'm no rider in the sense that others are I'm sure, but have had the same conundrum, wanting a better, more modern fork for an old frame. I've tended to go with Reba or Sid 32mm forks, dual air, as you can adjust the travel down to 80mm if it isn't already using travel spacers internally (or if Reba U-turn, at the twist of a dial). You can even adjust lower than 80mm travel of using internal spacers.

As I'm no rider, I haven't really noticed any difference when riding such old bikes as a GT team RTS or a dbr axis TT with such forks mounted.

 

[Frankenorange]

+\- 10mm A-C change = ~ 1deg change in geometry from ‘std set up’. Too much ^ in A-C = more Chopper like handling or increased steering/handling ‘Twitchiness’ if vice versa. As member above, I have experimented and geometry has a huge effect on how a bike rides/handles.

10mm is 0.5 degrees not 1.