How much will changing forks change geometri?

[M-Power]

10mm is 0.5 degrees not 1.

Closer to 0.6 actually. I think the effect would be enhanced on smaller mountainbike frames with small head tubes and shorter top tubes and less so on larger frames with longer TTs. I experimented with CK base plate spacers and its 100% is noticeable and affects handling. Big fan of Sheldon but I dont agree 100% with everything he says, just my 2p

https://www.sheldonbrown.com/rinard/forklengths.htm?utm_content=cmp-true

 

[novocaine]

Closer to 0.6 actually

https://www.sheldonbrown.com/rinard/forklengths.htm?utm_content=cmp-true

rule of thumb on a typical length wheel base from the 90's through the 2000's is 1" is 1 degree. shorter frames mean more change, longer frames less. a modernish geometry will be around 1/2" to 1 degree because of the length of wheel base.

similarly, 1" is about 1/4" at the BB.

put it on, the worst is it's wrong and you put the old fork back on.

 

[M-Power]

rule of thumb on a typical length wheel base from the 90's through the 2000's is 1" is 1 degree. shorter frames mean more change, longer frames less. a modernish geometry will be around 1/2" to 1 degree because of the length of wheel base.

similarly, 1" is about 1/4" at the BB.

put it on, the worst is it's wrong and you put the old fork back on.

Lots of Trigonometry at play and it defo varies with wheel base and frame size. Good point about modern bike geometry. My experience is with retro frame geo.

 

[novocaine]

Lots of Trigonometry at play and it defo varies with wheel base and frame size. Good point about modern bike geometry. My experience is with retro frame geo.

yer, and once upon a time you could get free access to bikeCAD online to play around with numbers and see what happened. not so easy anymore.

 

[M-Power]

I defo notice it more on rigid bikes. The effects feel more subtle to me with sus forks.

 

[novocaine]

I defo notice it more on rigid bikes. The effects feel more subtle to me with sus forks.

100mm fork should have 25mm of sag. so the ATC in practice is considerably shorter than stated.

 

[brocklanders023]

OP, do you mean 10cm or 10mm difference? I regularly run modern bikes 10 to 20mm over recommended with no trouble at all. Infact, my Pace hard tail is rated for 130 to 150mm travel. 10cm? That might feel off!

 

[kaydee]

I would agree with brocklander,If you are worried just set the sag so they are the same length when you are sitting on the bike.A couple of inches makes little difference with suspension forks since they are changing length the whole time,extending into trail holes and compressing over bumps.I started with a 1993 rigid steel stumpjumper and over the next 10 years went up to 150mm fox through axles and it still rode brilliantly,if anything the increased rake improved the stability going downhill and the 150mm made control easier by a massive margin.
This topic is very polarising and heavily debated,with one side saying it will make a huge difference and the other side saying “no difference whatsoever”
I recently sold a pair of 130mm Fox forks to a guy on this forum who was going from rigids and had exactly the same concerns as you,so increased the length by at least 20mm He set the forks up and was blown away by the difference.
If increased rake was such a big deal new generation bikes wouldn’t exist.
It is very subjective,and you should try both options to see which side of the debate you come out on .
All the best

 

[Rebikecumbria]

It will definitely explode into a ball of flames opening a rip in the space time continuum and sucking the whole of the known universe through it !!!

 

[Stressed]

It will definitely explode into a ball of flames opening a rip in the space time continuum and sucking the whole of the known universe through it !!!

He's right- which is why you should do it