Author Topic: 100mm to 140mm- what would it affect? (Read 4539 times)

RiskEverything · « **on:** March 06, 2007, 12:36:25 PM »

Out of curiosity, what would it affect if I changed my fork from a 100mm to a 140mm?

Gregg · « **Reply #1 on:** March 06, 2007, 01:12:45 PM »

It would change your head tube angle, which would change the handling of your bike.

Homer 2-Niner · « **Reply #2 on:** March 06, 2007, 02:05:44 PM »

i dont think the travel of the fork makes the head tube any higher.... i went from a 100mm fork to an 80mm fork and there is no difference.. i had the bike shop measure the angle (cause i did not believe it) but the angle is exactly the same....

who knew..

=Bob

Garry · « **Reply #3 on:** March 06, 2007, 06:00:03 PM »

Quote from: Trek8500 on March 06, 2007, 02:05:44 PM

i dont think the travel of the fork makes the head tube any higher.... i went from a 100mm fork to an 80mm fork and there is no difference.. i had the bike shop measure the angle (cause i did not believe it) but the angle is exactly the same....

who knew..

=Bob

Going down 20 mm might not be a measurable amount, but going up 40 mm just may. I went from 74 to 80 and could feel a slight difference on my hardtail.

RiskEverything · « **Reply #4 on:** March 06, 2007, 06:09:38 PM »

How would it affect the handling of the bike? More responsive turning, less responsive turning, or...?

Gregg · « **Reply #5 on:** March 06, 2007, 06:10:27 PM »

I actually remember reading about this topic in Mountain bike Action or Dirt Rag sometime over the last 6 weeks, I will see if I can find the article.

Couch Rider

Gregg · « **Reply #6 on:** March 06, 2007, 06:12:41 PM »

It would probably slow the steering down some. This could be good or bad depending on your bike and preference. I am pretty sure this was in one of the letters in MBA. I will try to find it.

EllsRider · « **Reply #7 on:** March 06, 2007, 06:50:13 PM »

You could also void the warranty on the frame if there is any. But then again if you take the front fork off and send it in .... who would know? What type of bike is it on? That is raising it up quite a bit. You could compensate the rise by going with flat bars and maybe changing or flipping the stem. Do you have a free 140mm fork to play with? Might be worth exploring the possibilties compared to laying out the moolah for another fork!!

Vélo · « **Reply #8 on:** March 06, 2007, 09:47:12 PM »

Quote from: Gregg on March 06, 2007, 06:12:41 PM

It would probably slow the steering down some. This could be good or bad depending on your bike and preference. I am pretty sure this was in one of the letters in MBA. I will try to find it.

Hey Couch Potato,

Will you share this with everyone when you find it? Thanks.

~Nikki =)

p.s. i found a team for squiggy, so i'll be riding. i'll be looking for you on saturday.

Gregg · « **Reply #9 on:** March 06, 2007, 09:54:31 PM »

Cool, I will be there. I will be the one with the cane instead of a bike. Who will you be riding with?

Sloth

RiskEverything · « **Reply #10 on:** March 06, 2007, 10:50:43 PM »

I was just thinking that down the road I may want to swap a Lefty Max onto the Rush to replace the Lefty Speed. Downhills still make me nervous, and slower steering there might be a blessing! We'll just see how I like the bike when/if it ever shows up. Tomorrow marks 1 week since the end of the auction and I haven't gotten so much as a tracking number yet. I figured I'd give him a week before bugging him about it- I know how hectic and busy life can get and what a pain it can be to ship large items.

Homer 2-Niner · « **Reply #11 on:** March 07, 2007, 07:55:26 AM »

Quote from: Garry on March 06, 2007, 06:00:03 PM

Going down 20 mm might not be a measurable amount, but going up 40 mm just may. I went from 74 to 80 and could feel a slight difference on my hardtail.

Garry,

Was the steerer tube cut to the same length after you installed the new fork???

The ride height should not change.. I can see your point about going up 40mm and that probably will adjust the ride height alittle...

=Bob

Gregg · « **Reply #12 on:** March 07, 2007, 11:30:15 AM »

Bob,

The steering angle has to change some. In your case it was only 20 mm, so it may have been slight, assuming that you are running the fork with the same amount of stiffness than you steering would have gotten quicker.
Your bike probably feels more responsive than it did before.

Gimpster

Homer 2-Niner · « **Reply #13 on:** March 07, 2007, 11:32:47 AM »

the angle is no different..

heres why

the stantions are the same length on both forks.. the only difference is the travel of those stantions.....

=bob

CrazyWhiteGuy · « **Reply #14 on:** March 07, 2007, 08:06:21 PM »

I changed my fork from 80mm to 120mm and it works nicely. When I started ridding the fork was a cheap pogo that dove down on every downhill, but when I swapped it out, the new fork slowed the steering down so it just eats hills now. One of the advantages I noticed was that it was also easier to balance on the bike. I still lower it down to about 100 when I wanna go really fast. Plus it totally improved to fit of the bike.

Gregg · « **Reply #15 on:** March 07, 2007, 10:30:32 PM »

Quote from: Trek8500 on March 07, 2007, 11:32:47 AM

the angle is no different..

heres why

the stantions are the same length on both forks.. the only difference is the travel of those stantions.....

=bob

I hear what you are saying, but..... Do you still have your old fork? I would be curious to compare them side by side. I am not an engineer, but the very fact that the travel is different would mean that the head tube angle would be different.Under compression they must be different, right? There would have to be something to offset the difference in travel. I know I have been taking alot of [Spam Word] and I am not so sure that I would bet my right leg (the good one) but I am not sure how that can be.
I mean I definitely think it can work fine. I think it can even be beneficial, but it is like changing the aspect ratio on the tires of your car, everything from speed calibration, to cornering grip, to ride and braking can be affected.

Comfortably numb in Wesley Chapel

Homer 2-Niner · « **Reply #16 on:** March 07, 2007, 10:38:29 PM »

your killing me.. lol..

yep i got the old fork and we'll look at it if ya want to.. but i'm telling you.. the stantions on the SID are the same length as the other fork, and when the sag is set properly

there aint a diff... but we'll check er out daddy..

oh btw my kid brother is going to be in town from thursday night to sunday sometime... wouldn't mind getting together off a trail with everyone if thats entirely possible..

-Bob

Gregg · « **Reply #17 on:** March 07, 2007, 10:39:36 PM »

That would be great call me now, I am wide awake

Homer 2-Niner · « **Reply #18 on:** March 07, 2007, 10:40:49 PM »

gimme a minute.. im chatting with the wife.. i'll call you in about 5

BeerCan · « **Reply #19 on:** March 07, 2007, 10:49:58 PM »

I think the difference would be caused by the axle to crown height not the travel. A 25mm difference in axle to crown will cause approximately a 1 degree head tube angle change. So theoretically if a 80mm and 100mm fork have the same axle to crown height then the head tube angle would remain the same.

Homer 2-Niner · « **Reply #20 on:** March 07, 2007, 10:51:40 PM »

look at the big brain on sean!!!

getting all weird with the geometry theories over here..

=Bob

BeerCan · « **Reply #21 on:** March 07, 2007, 10:53:48 PM »

I had a lot of time to think about it while sitting in the locker room today

CrazyWhiteGuy · « **Reply #22 on:** March 08, 2007, 04:23:13 PM »

I think Sean hit the nail on the head, 25mm is probably just the difference in where the quick release clamps are placed. Which isn't an issue if he is using a Lefty fork.

News:

Author Topic: 100mm to 140mm- what would it affect? (Read 4539 times)