Bike: late 80's Specials Rock Hopper
Main use: Commuting
Tires: 26x1.5 slicks
Problem: Can't go fast enough!
Description:
48T biopace chainring, would like to swap out to 52 or 53T chainring without re-engineering the whole bike. Can it be done? I don't care it it doesn't shift quite as smooth, as when I get in that gearing I usually stay there for quite a while.

Would also like to know if it is a stupid idea, even just to try out, to put drop handlebars on it, for aero efficiency and power output.

Thank you very much!

Late 80's is most likely 6 or 7 speed rear cluster. The chainring swap is doable, but would require a longer chain. I would try to scare up a smaller range cassette instead, along with a slightly shorter chain, which should make the shifting little crisper. As for the drop bar, it would require the purchase of the bar and tape, new brake/shift levers, cables/housing and possibly a new stem to fit the diameter of the road bar. You would be better off trying to get your positioning on the MTB a little more streamlined- try moving the stem down in very small increments over a period of weeks and see if that makes you faster through aerodynamics. Getting a higher set of gears (smaller cogs) will be much more successful in terms of boosting you top speed. But definitely get rid of those @#*$! Biopace rings anyway. They were a stupid idea in the first place, and they do nothing to help the smoothness of a good pedal truck.

Thanks alot man. I'll try to find a parts bike or something that has different chainrings on it that might be compatible. The handlebar idea sounds like an expen$ive one, I'll just stick with what I've got, for now anyway. I've got some ideas about using my current one and making aero bars for it LOL. Who knows! I'm creative and not worried about it being ugly.

Thanks for that info!!

OH BTW its a 6spd rear cassette, and the LBS said 14 was the lowest they could get. Its got a 13 on it now... I'll just get another chainring, a 52 probably that should really help!

Try putting some bar ends on your bars. This may put you in (or at least make you feel like you're in) a more aerodynamic position. I've found the bar ends make road riding/commuting a lot more comfortable and I can stretch out a little more over the front end of the bike. They come in a whole range of sizes and shapes. Almost makes it feel like riding on the brake hoods on a road bike.

And hang on to that old Specialized, that thing will last forever!

Assuming it's a freewheel, you might be able to put in a 7-speed 11-34 shimano megarange freewheel without swapping axles. keep in mind you might loose that 34 if you don't use a more modern derailleur (you probably won't need it anyhow on a MTB commuter, but a wasted gear is a wasted gear...).

The der should handle a 7-speed freewheel just as well as a 6-speed. It's more the tooth range (largest cog minus smallest) that's the issue. The more obvious issue is that you have a 6-speed shifter. The pressing question is whether the stops on the 6-speed shifter would correspond with the positions of the smallest 6 cogs on a 7-speed freewheel.

Those biopace chainrings are elliptical. Would changing the ring to a modern round one be a problem?

I'll second the suggestion for bar-ends. You might also want to consider a different handlebar... one with less sweep, width and rise. A straight bar in the 22"-24" width range with a maximum of a 5-deg sweep should bring you in better in terms of aerodynamics. You might also want to consider something like the old Zoom Brahma bars which will give you many hand positions towards the middle as well as the ends. Additionally, getting a new quill stem with a lower rise will help get your position lower to make you less of a billboard into the wind. It looks like you have a fairly long and high-rise stem there. Make sure that your total reach isn't effected too much. This conversion will require no change to your handlebar equipment other than moving it off one bar and mounting it back onto another.

No. The two issues, chain length and capacity of the front der, both come down to number of teeth. If anything, a fully round chainring should shift a bit better. Some wildly ovalized/elliptical chainrings used to create shifting difficulties, because of the changing relative position of the receiving teeth and the der. But biopace rings are neither elliptical nor oval, but merely off-round in some supposedly geometrically meaningful way. Still, they're pretty close to round.

My 2cents,

Usually most people can get going faster by concentrating on thier cadence. The frequency of your pedalling will get you going faster than brute force in a super high gear. If my calculations are correct, you are running a top of 96 gear inches (48/13)*26=96. I most of the time cruise around at gear inches of 67.5 or 72 on my fixed gear commuters, and I have no problem maintaining 20+ mph average speed.

If you have a computer on your bike, do a little test. On a flat stretch, sprint as fast as you can in the 48/13, check your speed out, then down shift to the next easier gear, continue sprinting, I will almost bet your speed will increase by at least 2 MPH. I didn't believe this to be true, till the last time I went out on my road bike, spinning out like crazy got me going about 5mph faster. What else, is that you will be giving your heart a better workout, opposed to just powering with legs which cannot be as strong as your heart is.

Just a suggestion, you might not even need to get the 52 tooth.

Phil

Fitting aerobars rather than bar ends will make you more aerodynamic. Bar ends enhance the parchute effect, but with aerobars, the air goes on the outside of your arms. You wont loose any efficiency over drop bars, just the variety of positions.
The limiting factor for the big ring is the curvature of the outside of the front mech. MTB mechs have a smaller radius, but yours may just cut it.
When you are comparing ratios, use gear inches for measuring the gear, and factor in the size of your wheels (inc tyres). A 53 ring is std on road bikes, but is too high for most riders. You have smaller wheels (which give a lower overall gear for a given cog combo) so it may be OK.
Swapping from biopace to round will enable you to spin at a higher cadence, so you may not need a really big ring.

Please don't be one of those dorks who put aerobars on a MTB. You won't gain more than a ridiculous position as the "aero" effect will be negated by your high stem. i

I wouldn't say that aerobars are the best but I know that on my old bike that had a flat bar on it, I could put my hands in the middle and crouch down, and go significantly(sp?) faster than if I didn't. I think I am going to try putting my bar-ends near the middle of the handlebar, to give me a good point to hold on to.

I just want to say THANK YOU to everyone who's answered here, I am much better informed and I think I will just get a slightly bigger chainring in the front, a 52 probably, and make it work that way.

Thanks SO MUCH guys!

I really would consider replacing the stem and handlebars with a lower stem and narrower bar if I were you. From your previous pictures, it looks as if that bike has the handlebar setup of a beach cruiser.

That is true! I have another stem/handlebar I'll set up tonight and see how I like it.

If you do end up replacing the stem, you'll probably want to go with one that has an open-face design (you should be able to find a few open-face quill stems still) and you'll probably also need to invest in a headset mounted cablestop for your front brake as most modern stems don't have builtin cablestops anymore. The added advantage is that you won't have to worry about readjusting your brakes everytime you move your stem height.

Good advice, that is. I'm doing it on the ultra-cheap though. I have a stem/bar from a parts bike that should do the trick

Well I took a little time and swapped the stem and flat bar from my parts bike, and it works perfectly. Puts me a little lower, which I like, and should be better to let me tuck down and go fast. Next: Gears....