Okay, I've already got three other bikes, why do I need a fixed gear? Because I'm gluttonous and want to try one out. I"ve got a roadie, a mountain bike, and a commuter. (all which get plenty of use in denver) My question to those with fixed experience is: Mountain bike with slicks or road bike? Especially if I want to use it in Denver AND Denver can be pretty hilly with my destinations what is a good gear ratio to use?

Thanks mucho,

Dave

Road bike, at least that's what I'd do.

As for gearing, try to find a combo on your bike that's comfortable for you to ride around in without shifting, then gear your bike a couple of inches higher (you'll get more power on the fixie for the same gearing.)

You could try asking over in the SS/Fix forum, too. There's a few people that ride them over there

Depends what's most comfortable for you... Since you already have a stable of bikes, experiment with different gear ratios climbing different hills and decide what you would like the most.

I've ridden a mountain bike with slicks (my current ride) and also a road bike. Either one is OK, of course the handling will be different but I like them both just the same. The road bike had a more "sporty" feel to it whereas the mountain bike has a more "tank" like feel to it. Either one will be fine though and you'll have tons of fun. I would say pick the bike that fits you best!

As for gearing, go a tad bit higher than you normally would for single speed or geared. Climbing hills fixed will be quite an adjustment anyway....

Your road bike should have horizontal dropouts and 126 rear spacing;
MTB dimensions and geometry make things a bit more difficult to set up as a fixed gear.
I say go for gearing in the high 60s/low 70s, like a 42x16 or 42x17.

$0.02 - I'd roll with the road bike. The easiest way to determine the gearing is ride around without shifting for a week. Pick the biggest gear you can ride up the biggest hill without having your kneecaps pop off your legs. Also, are you a seated or standing climber? If you sit, go with an easier gear. Actually, that's not a bad idea overall. A bigger gear will mean more speed on the flats, but slowing down without using a brake will give your legs a major workout at first. I'd ease into it. You can always switch to a 53x11 down the road...

I've seen this repeated a few places now. There's nothing about an MTB frame that makes it somehow more difficult to set up as fixed gear.

Fixed MTB frames are fun as hell, too.

Heh im doing the same project as you. A fixed gear as a summer commuter. I've so far settled on a Milwaukee frameset. Lets see what happens...

Most mtbs have vertical dropouts making it hard to find the magic gear combo so your other option is an Eno Eccentric hub which costs a lot. If you do the mtb and take it to the trails, ummmm....have fun.

Go with a road bike and keep the brakes (or at least the front).

Here's a magic gear calculator: https://eehouse.org/fixin/ You have to get a very accurate measurement of your chainstay length, and you're limited in the gearing choices, obviously.

But I've done it and it works great.

definitely go road frame-- you'll love it. THe 'standard' gearing for a fixie starts at 3x1. In other words, if you have a 48 tooth chainring, use a 16 tooth cog. If you have a 42 tooth chainring, use a 14 tooth cog. That's a good starting point. Try it and see how it does. Realize that you will be able to climb in a higher gear on a fixie than you would on a road bike.

My personal experience was to start with a 48x18, whch I could do almost everything around here (Washinton DC area), but I found I wasn't spinning. I was limiting myself to around 80 rpm. I changed the rear cog to an 18 tooth, and now I spin much better. I also haven't hit a hill I couldn't climb in it (knock on wood). I did a hilly century on it last year, and came really close to walking, but made it up--it wasn't pretty, but I didn't walk.

Keep the front brake-- you will use it to slow down on the downhills. You can stop without it, but it will be taxing on your knees. And once those go, it's hard to get a replacement

At any rate, enjoy the challenge (it will take a few rides to get the hang of it--and to remember not to coast-- the bike reminds you really quickly).

train safe-

I'll vote for the road bike as well unless you can find a steel MTB frame with horizontal dropouts (steel can easily be respaced to match a narrower fixed hub) in which case it's a toss-up.

Gear ratios are all relative to tire size. Gear inches are a much better measurement, but they technically will be relative to crank length if you are really anal. Gain ratios are the answer, but I find them to be a bit of a weird measurement to work with. I talk in gear inches for this reason.

If it's just kind of hilly, like 6% grades or less in most places that aren't too long overall, aim for the low 70s. If you have more hills and more steep ones, aim for the high 60s. I wouldn't go much lower than about 65 gear inches or you will be spinning hardcore. 68 or 70 would be a good ballpark to start with. Here's how to do the math: https://www.basementfreaks.com/members/karl/gearing/

Have fun with it and don't fall for the idea that brakeless is a good idea (especially in hilly areas). If you want to run brakeless, ride with a brake for at least a few months beforehand so you have a safety net while learning what it takes to control the bike with your feet. I ride a fixed gear road bike conversion almost everywhere I ride these days, and I run a front brake. I'm running 74.2 gear inches (48/17) with 700x23 tires and 165mm cranks, for the record. I can hit 38mph on good downhills, but it means spinning 172rpm of cadence (this happened yesterday, and twice recently I hit my previous record of 37mph/167rpm).

David, PM me if you like, I'm up north of you a ways and have three conversions ready to ride I'm trying to sell. I'm heading down to Pueblo either the 22nd or the 29th and could meet up with you somewhere.
I'm no dealer or anything, just like to see more fixed around. And letting a couple go gives me room to build up a couple more, so holler back if you like...