Singlespeed & Fixed Gear - Wanna do a road to fixie conversion with CAAD3 bike; any issues?
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01-27-04, 10:49 AM
So I got a new roadie bike and thought I'd turn my old Cannondale into a time trial bike until I realized that there would be absolutely no point in doing that since I won't be trying to race for a year or more. Then I thought about converting it to a fixie. Way I see it, it'll be hella fun to ride and help my spin while giving me a different perspective on riding.
There's the idealism. The reality is that I'm not real sure that this frameset is alright for doing a conversion with. It has vertical dropouts, of course, but I found a rear hub that addresses chain tensioning issues that this brings up. I've been reading about doing a conversion over on sheldonbrown.com and it looks like I can use my Dura Ace stuff everywhere except the rear hub. They've got spacers to move the front chainring over to get the chainline straight.
So, here's my list of what I need to do this conversion. I'd appreciate anyone's additions or help. I already have the complete bike, so bars, etc. are taken care of. I also have some old 105 brakesets hanging around and I'll put the front one on the bike at least for a while. And I need a set of pedals, but I'll probably get something Look compatable since that's what I have on the roadie bike.
Chainwheel spacers (again, to center the front chainring)
I'm not sure about gearing yet, actually, and could use some help in getting that narrowed down. The terrain around here is rolling with some kind of steep hills. I don't see myself riding to the top of any mesas for a while, but still, there are some good climbs of 2-3 miles that would be a goal eventually. I tend to spin if I can, but recognize that I won't spin when I climb and will spin like crazy on the way down. That in mind, would you suggest running a shorter crank than what I have on the roadie bike (175's)?
I've been searching around here, too, for threads about doing this and most point to sheldonbrown.com, which I trust. I just want to make sure that someone that's done this or knows more about it than I takes a look at my goodie list. Thanks in advance!
01-27-04, 11:18 AM
Most people run shorter cranks for the reduced pedal strike risk, I run 175's on my road and 170's on my fix, I haven't heard of anyone running longer than 170's on a fix. However if you're not doing aggresive cornering and your BB isn't too low then it should be ok. If you're using it as a training bike then may be some good points to keeping the crank lengths the same as you may use slightly different muscles for each, however i'd still go with the 170's.
As for gear ratios, try out various gears on your normal road bike for a while whilst refusing to change. Most people run about a 3:1 ratio on the road, or about 65-75 gear inches. The steeper your hills the lower ratio you're going to need. Personally I run 60" on my commuter fixie and 76" on my winter training fixie. If you're new to fixie riding it's best to start at a lower ratio and build up, if you start too high you may do damage to your knees.
Sounds like you're pretty much all set to go, by the way you can always set it up as a fixie time trial bike, plenty of TT riders use fixed gear.
Good luck with the conversion
01-27-04, 11:28 AM
Yeah, but I'd want to buy TT bars if I did that and something to get the saddle more over the bottom bracket. Maybe this is phase one of a fixie TT bike. I might have some old 105 cranks setting around, too, but I'm not sure how long they are. I'll check tonight. Thanks for the tip; if anyone else has anything, it'd be much appreciated.
01-28-04, 06:08 AM
I run 180mm cranks on my free wheel road bike and 172-175mm (172 now and spring, 175 in the summer) cranks on my fixed. I use my fixed like a regular bike on open roads so cornering isn't much of a problem. I slow down on tight corners .
I like the longer cranks for climbing and I am 6'4" so longer cranks feel more natural for me.
It is interesting to run the same gear with different length crank arms. You lose some of your spin but climbing is easier. For spinning though shorter crank arms are the way to go.
You should experiment, especially with a TT setup. I think for TT a longer crank arm may suit you.
01-28-04, 08:38 AM
Glad to hear that someone is running longer than a 170 on a fixie. I'm 6'1" with relatively long legs, and I'm pretty sure that anything under 170 will feel to strange. I ran 172.5's on my first road bike and got to where I was comfortable spinning, so I'm thinking 172's or 170's on this bike, depending on what I have sitting around or can get relatively cheap.
01-28-04, 01:00 PM
I was kind of curious about this subject and went back to Sheldons site.
I think what he says is that torque does not matter. So if I were to run shorter crank arms with a slightly bigger gear I could get the ratio/gain????
Is this correct??
Do I just think that longer crank arms climb better?
01-28-04, 02:23 PM
I think a lot of it depends on riding style. I used to be a spinner, but I had 172's then. I moved up to 175, since I'm a bigger guy with more power than finesse. I climb pretty well, but sometimes wonder what it would be like with 172's again.
To more directly answer your "is this correct?" question, I don't know. It stands to reason in terms of the gearing, and I suppose that gearing could offset any benefits one way or the other with regards to torque. It's been many moons since I thought much about physics, so someone that gets more about gear ratios will have to chime in.
01-28-04, 03:16 PM
You'll get more torque with longer cranks for the same gear ratio. There will be a situation where by using different gear ratios they will mechanically provide the same torque. However it will still feel different to your legs because you have to turn a larger circle with your feet. If you have this same effective torque with each set up you will still be more inclined to mash with one and spin with the other. So theoretically if you want to go faster you should spin, but there is a limit where spinning becomes less efficient. So you should choose your crank length in this situation to let you pedal at an optimum cadence. However this all assumes you have a set gear ratio which you never will anyway, so in the end is kinda silly.
Captsven how do you find the 180mm cranks? I was thinking of getting some (6'5") but I could only find them in dura-ace. In the end I settled for some more 175's. If I had got 180's I'd definitely feel like i'd have to replace my 170 cranks, and replacing two sets of cranks is too much for my budget.
01-29-04, 07:03 AM
Well since everyone else has covered the crank situation, I'm going to talk about hubs. I'd recommend the White ENO eccentric hub. It has an oversized axle with bolts offset from the centre so you can effectively change the rear end length while using vertical drops. I think it has fixed threads on both sides, so you could run a bigger gear or even a bigger freewheel on one side for the hilly bits.
As for the TT thing I think it's a great idea. Just stick on some cowhorns for now, get used to them, then get some tri extensions when you start racing again. If you keep the gearing under 72 inches you can run in a special Medium Gear catagory (if there is one in your area). This is for fixies only, and I think it's brilliant (if I ever race TTs I'll probably race Medium Gear).
01-29-04, 08:28 AM
My road bike cranks are Dura Ace 180mm. I have riden on them for two years now and love them. I still spin at around 100 rpm on them. I have never been much of a gear masher. They just feel right on my road bike and I have tried most sizes.
01-29-04, 09:13 AM
Jonny, I actually got the idea of doing this conversion because my LBS had a couple of those eccentric hubs in a couple of months ago. I'm going to rebuild my rear wheel with that hub. I've actually got a 170 RX100 crankset, so I just need a new bottom bracket and can get one pretty cheap. For a while I'm just going to use the bars that came with the bike, but maybe I'll move to a cowhorn bar later on. I'm trying to do this as well as I can without spending a ton, just to see if I really dig it. Good suggestion with the hub, though. It looks like a great piece and I've read a lot of good about it.
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