kdsola

anyone know the gear sizes that would work for a mountain bike frame with vertical dropouts... its an older GT with the triple triangle. thanks.

bonechilling

You'll have to figure this out yourself. This is impossible to
know without having the exact measurements of the frame,
and even then, there are only a few people I'm aware of
who could calculate that kind of thing.

Tadashi

FlatFender

Yep, My solution was to weld in some track dropouts.

threeoneseven

i have a later 90's gt avalanche frame, with surly 36t ring, 18t rear, and sram 8spd chain. also, mine measures 16-13/16 inch (sixteen and thirteen sixteenth inch) from center of crank bolt to center of skewer (rough stay length). it has perfect chain tension and alignment, but i have to take the back wheel off to get the chain on/off. not sure if this helps or if this setup would work for your bike though...

MrCjolsen

https://www.eehouse.org/fixin/formfmu.php

This calculator should give you an idea of what combos might work. The problem is that fixed gear chain tension has to be just right, so you will need to be lucky. I tried converting my wife's hybrid to a singlespeed and I ended up having to choose between a rather loose chain or 53-17 combo. The loose chain was fine for a singlespeed, but I would not ride it like that fixed.

Ken Cox

I wouldn't even try to make a fixed gear mountain bike out of a frame with vertical drop outs.

It makes more sense to put a "singleator" on it and ride it as a single-speed.

Yesterday, I commissioned Webcyclery to build a fixed gear mountain bike for me, using a Surly Karate Monkey frame as the starting point, with the intent of creating a winter ice commuter that will really work for me.

A person on a more severe budget than mine could probably do better with a Redline Monocog 29'er, and transer most of his bike parts to the Redline frame.
This would require only a new rear wheel and a Redline frame.
One can find a new Redline frameset for under $250 without much searching.
A new rear wheel with low cost as the priority?
I don't know.

How much would it cost to change the dropouts on an existing, owned mountain bike frame?
And then, wouldn't one still need a new rear wheel?

To me, for safety, the proper chain tension made possible by horizontal dropouts justifies the expense.

Safety doesn't seem all that important until one picks himself up off the pavement and realizes he has several broken ribs and a collapsed lung.

mander

Sounds like fun Coxy. The bike I mean, not the injuries.

AfterThisNap

a ghetto solution is to use a singelator under the chain, so the arm puts pressure upwards. It works, works well, but is noisy and looks funky.

SSSasky

That's no safer for fixed gear than the 'push down' mode ... well, it probably won't rip the tensioner off, but you'll lose all chain tension when you backpedal ... singlators really are for SS only.

You could try the ENO eccentric hub. I have one, and it works pretty well, although it's definitely more of a hassle to deal with than track ends.

DDYTDY

White Industries Eccentric Eno hub.
https://www.sheldonbrown.com/harris/white-hubs.html

doofo

do you work on commission
?

wearyourtruth

word.


but i started out with an eccentric hub, it's a little pricey, but with MTB it's really the only way if you really want to go fixed and really don't want to buy a new frame. have you ridden fixed on the trails before? it's nuts. i hope you've at least ridden SS, not because i'm saying anything about being able to handle it, but when you only got one gear, the one you get needs to be dialed in, it can't be based on what you can figure out works on your frame.

good luck!

Bushman

Its very possible to make a fixed mountain bike using vertical dropouts.

First off is cog choice - you want THICK cogs, without ramps, or precut shifting cutouts. Tall teeth are your frined here.

Cog size, go a little bigger, for more tooth contact. I use a 20 - 26 range.

Chainring size: again, no ramps or shifting cutouts. I use a 30 - 36 range for my offroad setup.

Chain. use a KMC BMX or track chain., They is beefy! Or best of all is a FULL "halflink chain".Really easy to setup chain tension with a halflink chain.

now the tricky part, chain tension.......install the wheel/cog on the rear and snug up the skewer or nuts. add the chain and wrap it around the cog and chainring, until your holding one end in each hand. Figure out how much cahin you need and remove links accordingly. To join the chain, you may need to use a couple of halflinks. Tension should be "snug", just enough so that when you turn the wheel backwards you can feel a bit of tension.

Good Luck.

Fixed offroad bikes are freeaking incredibly fun, you can POWER thru mud and snow without bogging down, its like positraction.

my next project project is a Surly Pugsley with their 4" wide tires, 26 x 24 fixed gear, disc brakes. Hopefully they will have their 4" wide tires in 29" too.....

DDYTDY

Naw, just happy with the product.

yonderboy

Glad to hear you got your winter commuter figured out. Hopefully Mean Todd and the boys really set you up nice.

I wouldn't personally run a MTB as a fixed gear. So much of the riding experience on trails depends on the "flow", which really gets derailed by running a fixed gear. There's also the odd occasion that you get into a rhythm section and the cadence of the cranks are synced with the bumps, which equals double ejection over the handlebars.

Gurgus

I've got an ATB sitting in the garage waiting for a fixed conversion. I got this bike from my father in law and it's got forward facing dropouts. Should be fun.

PanPanX

Where can you get a FULL "half link" chain? Also.. doesnt two half links just make one regular link? so.. wouldnt you just need to have a regular chain and one half link? Also it depends on the length of your chainstay.. for my mtn bike, if i remember correctly, i had a 16.1in chainstay length.. and the only way i could run a fg/ss without a tensioner is if i had some crazy combo like 22/9 or something..

mrsalty

https://www.bikemannetwork.com/biking/p/COMPCHSS/CH1009

mathletics

Depending on how much room you have in the dropouts, it may be possible to file the opening a little wider. You don't need a lot of space to fix your chain tension, just a few mm on each side if you get the chain right. I've never done it, but I know it can be done.

Unless I am mistaken about the identity, the BF member chimblysweep (or some variation of that) is a woman named Julie. Her brother, Scott, used to ride a Fetish Cycles frame that had been filed in this manner.

DDYTDY

Lots of off road fixed info here.

https://www.63xc.com/index.htm