Singlespeed & Fixed Gear - 2 Questions(biopace,chain tension)

Finally added a SS to my stable. A lovely white Surly 1x1. I was going to convert the old C30 until I saw the Surly on eBay. Great bike,but I need to do 2 things;swap the fat knobs for some smoother tires,and raise the gearing. It has a 33 on the front(14 rear I think,26"wheels) and I want something taller. When I was thinking of converting the C30,I rode it in 38/14 on 700cc's and it felt pretty good. My Dad has an old 42 Biopace ring from a Miyata,and after reading a Sheldon Brown article,I'm considering putting it on. I was wondering if anyone here has run a Biopace(elliptical) ring on their SS,and how they liked it.

Also,how should I check for proper chain tension? I've done it for years on motorcycles,but they all had rear suspension. Right now I've got the adjusters on the marks left by the previous owner and it feels ok,but I'd like to know the right way. Thanks in advance.

I had a friend who used a biopace ring on his SS. His only complaint was that he couldn't reach high rpms without bouncing. If I remember right they were designed for low rpm usage. Although I could be talking out of my arse, it has been known to happen from time to time.

The chain should be as tight as it can be without affecting the mechanical efficiency. When your chain is too tight, you can feel it 'grind', and the pedals seem to drag as you turn them upside down. The chain shouldn't sag on its own, but you should be able to move the middle of the chain run up and down about 1/2".

As for the biopace ring, I'd say throw it on and see how you like it. Its honestly not that much different from a round ring, and its a free way of trying out a new gear ratio. If you don't like the ratio, you can try something different, and if you do like it, but you don't like the biopace ring you can buy a round ring, and if you do like it, and you do like the biopace, then well, you are sittin' pretty. :)

Your bike is at 60 gear inches right now, and you said you liked a bike that was at about 71 gear inches, and going to a 42 front would push you to about 73 gear inches, a little over what you said you liked. But you might as well give it a try anyway, to see if you like it. 2 inches isn't much. Also, narrower tires will have the effect of lowering your gear, so if you end up using something like a 26 x 1 1/4", like the Specialized Nimbus, you'll be almost dead on with your gearing.

peace,
sam

I ride with biopace on my geared bike, and have no problem with 90-100 rpm. It does allow more efficient (muscularly) peddling at lower rpm, but doesn't hold you back at high rpm (and seems to make my knees happier).

I'm putting a biopace ring on my SS CX project. If that works, a biopace ring for my fixie may be in the stars.

When I lived in Seattle my mtb commuter had biopace. Sure helped me get the hills. That's my only experience with biopace personally and back the I was less concerned with cadence.

Finally added a SS to my stable. A lovely white Surly 1x1. I was going to convert the old C30 until I saw the Surly on eBay. Great bike,but I need to do 2 things;swap the fat knobs for some smoother tires,and raise the gearing.

As for the smoother tires, you wanting to stick to 26inch wheels? If so, there are plenty of semi slicks to slicks that would work. I just built up a 1X1 myself. Given that frame is designed to accept 26x2.7's you can fit 700's. I have plans on a second wheelset that are 700's runing like a 700x25 tire. MTBR's 29er section has guys running 29x2.1's on the 1x1.

As for the gearing, I agree with phidauex and throw it.

Thanks for the replies. I checked and the rear sprocket is actually a 16,but I'll still try the Biopace. I'm sticking with the 26's for quick handling and strength,this bike is mostly going to be an urban toy like my Buzz. For tires,I'm split. I'm thinking either WTB Slickasaurus 1.5's like my Dew,or Vittoria Randonneaurs(sp?) in 1.75 like my Buzz. I like the speed of the WTB's on the Dew,but the VR's would do better on the Canal trails,and I think have better puncture protection.

SpiderMike: I'd hate to see what would happen if I put 2.7's on this. I've got 2.35 Maxxis on it now and the rubber cable cover between the rear brake blocks is almost touching the tire!

SpiderMike: I'd hate to see what would happen if I put 2.7's on this. I've got 2.35 Maxxis on it now and the rubber cable cover between the rear brake blocks is almost touching the tire!

Thanks for the input on the tire fit. Makes me wonder how far back in the drops I'll need to go for the 2.4's I have ordered.

This is wierd. I just bought a Shimano EXAGE crank from a bike store that was closing down. I planned on putting a bike together with all the parts I bought but tonight when went to put the crank on it looked a little odd. The rings were all egg shaped and I was pi**ed, I kept thinking what a piece of ****, and planned on using it as meat tenderizer. What do you know, I get on the forum and there is a thread on the biopace rings, which are marked on the rings that I bought. I saw the marking when I bought it but wasn't sure what it meant. Will this still work for a fixed bike? I know it probably will but I don't want to take a chance eating the pavement when the chain falls off.

Biopace will work on a fix. The argument seems to stem from whether or not "working" equates to "feeling exactly the same as a round ring." In my own limited experience, it feels different but it works fine. My first conversion had Exage cranks with Biopace; I used ye olde elliptical ring for a while before switching ratios and going to a round ring.

One big bonus - if you find you like the feel of Biopace, then you can score rings for nothing and have lots of really inexpensive gearing options. People can't give them away.

As with most things, Sheldon Brown has lots to say on the subject. Check out the Biopace info on his site.

m.

I had Biopace on my SS and they worked ok. As Cynikal noted, at really high rpm (>100) I could not spin smoothly with them. You could feel the biopace thing as resistance on the cranks increased and decreased with the ellipse. Solved this when Cynikal gave me a round chainring.

There were two models of the Biopace, one was less elliptical and was designed for higher spinning and road gearing, the other was more pronounced and used on MTB setups. The breakpoint between the two was a cadence of 90rpm.