140 mm fork on a hardtail?

BikGer2 · Jun 19, 2022

Hi there,
I'm looking at putting a 140mm fork on my GT Avalanche, that comes stock with 120mm.

+20mm seems like quite a lot to me, and I'm not sure if that would overfork it. I've seen a guy who's put a 140mm Fox 34 on the same bike, and he says he overforked it, but doesn't seem to have any issues riding.

What do you think about this? I'd like to hear your opinion.

Thanks

Sparticus · Jun 19, 2022

Do it -- won't be a problem.
Run the longer fork plush.
=sParty

Sir kayakalot · Jun 19, 2022

Do it. I bet you’ll love it. I put a 150 DVO on my DiamondBack hardtail two years ago and it’s the best upgrade ever for that bike. Like Sparticus said, run it plush

theMISSIONARY · Jun 19, 2022

Most of the GT Avalanche's have 100mm forks, so I would say it's going to feel like crap with the change to the geometry.

cmg · Jun 19, 2022

run it plush, and send it

mack_turtle · Jun 19, 2022

What year is the Avalanche? The current Elite model has a 120mm fork on it. putting a 20mm longer fork is going to significantly:

jack the front end (stack) up in the air
raise the BB quite a bit
slacken the seat tube and head tube angles
shorten the reach
raise the standover height

Whether these are things you want is up to do. personally, it sounds like it will make the bike handle like an unbalanced monster truck. it will be rear-heavy and probably difficult to keep the front end down.

additionally, there's a chance that the bike was not designed to safely withstand the forces put on the head tube with a front-center that long. I probably sound like a big nerd, but I'll err on the side of caution when it comes to mitigating the potential of the front of my bike snapping off because I value the structural integrity of my face.

I'm looking at the current Elite geo and it already has a short reach and a tall stack. it's balanced but conservative.

Sir kayakalot · Jun 19, 2022

GT underforks their bikes. Make it right with a 140. Everyone knows this

maynard4130 · Jun 19, 2022

I put a 140mm fork on my old school geometry timberjack hardtail. It did raise the BB (which is good since I changed from 27.5 3.0 to 27.5 2.6), It did shorten reach slightly (so I left the 60mm stem on instead of going shorter like most bikes now), slacked the head tube (which is good because it was old school 67), and I ride a lot of gnat here in Colorado so the plushness is welcome. Like my bb height , stand over was a wash with the smaller tires. It worked out well for me, but I wouldn’t go much higher than 140 personally

cookieMonster · Jun 20, 2022

I run a 160mm fork on my hardtail — however, it’s designed for it.

If your Avalanche came with a 120mm fork I don’t think 140 would be out of line. 20mm of increase isn’t even an inch. Your bottom bracket will not rise by 20mm; it’ll be less. As others have said, run it with a little more sag than normal and it will improve your ride quality as well as still improve your downhill geometry.

noapathy · Jun 20, 2022

Don't do it. You'll die. Guaranteed.
(eventually)

BikGer2 · Jun 20, 2022

Thanks for the help guys!
I think a 140mm fork is a pretty safe bet. The leverage increase is small, so it shouldn't make compromising the head tube easier (not significantly enough). When it comes to the feel of the bike, it's got a pretty low BB and I grind my cranks on everything, so I'm looking forward to slightly raising it.

I know the entire build is going to be a little bit ghetto when I swap the fork for a 140mm, but I think it would suit the trails I ride.
Also, I'm looking at forks like the Rockshox 35 or Revelation.
Any suggestions on those?

fuzz_muffin · Jun 20, 2022

Contrary to what seems to be the popular opinion, I found that my diy hard tail was better to ride with a 130 fork with a stiff and progressive fork setup vs. more travel and softer. I liked matching the stiff and responsive rear end feel hard tails give. Riding a stapler sucks, to me anyway.

Donkeeboy · Jun 20, 2022

cookieMonster said:
I run a 160mm fork on my hardtail — however, it’s designed for it.

If your Avalanche came with a 120mm fork I don’t think 140 would be out of line. 20mm of increase isn’t even an inch. Your bottom bracket will not rise by 20mm; it’ll be less. As others have said, run it with a little more sag than normal and it will improve your ride quality as well as still improve your downhill geometry.

This ^

it’s not a problem if the bike is designed for a long travel fork, I run a 160mm fork on my Argon, but it’s designed for it.

Try it, but if you really want that kind of bike, get a different frame.

Buffalo Soldier · Jun 20, 2022

I’ve over forked bikes for years with varying results, most good. All I can say is try it if you can afford the cost of failure.

Sent from my iPad using Tapatalk Pro

theMISSIONARY · Jun 21, 2022

BikGer2 said:
Thanks for the help guys!
I think a 140mm fork is a pretty safe bet. The leverage increase is small, so it shouldn't make compromising the head tube easier (not significantly enough). When it comes to the feel of the bike, it's got a pretty low BB and I grind my cranks on everything, so I'm looking forward to slightly raising it.

I know the entire build is going to be a little bit ghetto when I swap the fork for a 140mm, but I think it would suit the trails I ride.
Also, I'm looking at forks like the Rockshox 35 or Revelation.
Any suggestions on those?

Revelation hands down over the 35

justwan naride · Jun 21, 2022

I'd say getting a better fork with the same travel will be more of an upgrade. More travel doesn't equal a better ride. 20mm increase may be doable, but not sure if it's really desireable.

Why do you want to change the fork anyway? The answer to this will help you make the right choice.

BikGer2 · Jun 21, 2022

justwan naride said:
Why do you want to change the fork anyway? The answer to this will help you make the right choice.

The Suntour fork I'm currently running is just really harsh and not so adjustible. It has the rebound of a pogo stick and bucks me around on anything techincal, while also causing pain in my hands.

dietz31684 · Jun 21, 2022

Look at A2C instead of comparing travel. Also, do you have any spacer under you stem currently, so you could drop the bars?

I'd not stress at all going from 120mm to 140mm.

BikGer2 · Jun 22, 2022

dietz31684 said:
Also, do you have any spacer under you stem currently, so you could drop the bars?

Yeah, do you think I should drop the bars a little bit if I put a 140mm fork on it? I know that's heavily based on feeling and personal preference, I ride 20mm rise bars and the entire front end of the bike is kinda low, sometimes I have hand numbness on long rides and need to rest my hands.
Might pick up a set of better grips too.

HollyBoni · Jun 22, 2022

BikGer2 said:
Yeah, do you think I should drop the bars a little bit if I put a 140mm fork on it? I know that's heavily based on feeling and personal preference, I ride 20mm rise bars and the entire front end of the bike is kinda low, sometimes I have hand numbness on long rides and need to rest my hands.
Might pick up a set of better grips too.

Just test it and see how it feels. Takes 5 minutes to change the bar height.

140 mm fork on a hardtail?

BikGer2

Sparticus

Sir kayakalot

theMISSIONARY

cmg

mack_turtle

Sir kayakalot

maynard4130

cookieMonster

noapathy

BikGer2

fuzz_muffin

Donkeeboy

Buffalo Soldier

theMISSIONARY

justwan naride

BikGer2

dietz31684

BikGer2

HollyBoni

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