New to the Forum

[Champ1FC]

Greetings! 275# mountain bike enthusiast here.
I did a Bo Bikes Bama ride on my converted old rigid mountain bike. Thanks to Bike Nashbar and their Kevlar 1.5" road tires. But, I seem to be lacking in top end speed. My old mountain crankset is a 48/38/28. I thought more teeth might help. Unfortunately from what I have found, most road set ups are only 50t anyway. Does 2 teeth really make a bigger gear? Besides the fact that I am running an antique tapered BB. Would it be worth it for me to keep my old clunker to I can hot rod around town?
Maybe my bigger body type and heavier pedal stomp make the gears seem low, even my new mountain bike seems under geared for my riding style. I guess I also need a cyclometer to see what my tempo is, maybe I just need to quicken my step.
Any advice? I plan to comb the forums here to try to learn from what has already been posted.
Thanks for any links and or advice ya'll can give me.
John
Opelika, AL
'90's rigid convert
2012 Motobecane 29 Fantom 29

 

[alfeng]

FYI. I believe that you have been unintentionally misled by whatever you have read in the past ...

• Many bicycle chainrings have many more than 50t. There are even chainrings with more than 50t fo the so-called "Compact" (110BCD) cranksets which have become popular in the past 10 years.

Regardless, if you want a chainring with more teeth, the easiest (?) and possibly the least expensive (THAT may be counter-intuitive at first) way is to replace your MTB's current crankset with one which is typically installed on a ROAD bike. Although Shimano & Campagnolo are currently trying to establish NEW standards, the current "standard" BCD (bolt circle diameter) sizes are 130mm (almost universal) & 135mm (essentially, only Campagnolo) ...

• 130BCD & 135BCD cranks are typically sold with a 52t or 53t outer chainring + 39t inner chainring

FWIW. Here is is one of my MTB frames which was set up with Road cranks + 700c wheels + Drop handlebars ...

Because of the width of the chainstays on the particular MTB frame, the Road crank needed a BB whose spindle is typically used for a "Triple" Road crank (e.g., 118mm Octalink or ISIS OR a Hollowtech II or MegaExo or Ultra Torque crank which actually is a Triple crankset (the Granny can be omitted to make it a Double)). BTW. Somewhat to my surprise, on one MTB frame which I have, the stays allowed me to install a normal[COLOR=FF00AA]/[/COLOR]"Double" Road crankset & BB combination.

 

[Champ1FC]

Thanks for the info Alfeng.
Another part of my story is that it is an old bike. I don't know how to upgrade the old tapered axle BB to a accept a more modern crankset. My misled info came from the only discount parts connection I have, Bike Nashbar. I only browsed their selection of road cranksets, All of them seemed to be labeled as 50t. I'll do more research to find a bigger gear. Like I suggested in the original post, maybe I need to pedal faster... how about shorter crank arms? I'm only able to average just over 15MPH on a flat ride.
J

 

[alfeng]

Originally Posted by Champ1FC
Another part of my story is that it is an old bike. I don't know how to upgrade the old tapered axle BB to a accept a more modern crankset. My misled info came from the only discount parts connection I have, Bike Nashbar. I only browsed their selection of road cranksets, All of them seemed to be labeled as 50t. I'll do more research to find a bigger gear. Like I suggested in the original post, maybe I need to pedal faster... how about shorter crank arms? I'm only able to average just over 15MPH on a flat ride.

FYI. Bottom Bracket 'technology' has changed over the decades ...

And, while a square taper BB spindle was state-of-the-art for several decades, it has since been superseded in most riding venues (the exception is some-or-all sanctioned TRACK racking).

So, while the square tapered spindle is still used on some inexpensive bikes, THAT is probably only a consequence of licensing-or-the-lack-of vs. more recent BB spindle types which may require royalties.

There is a lot of variability in square taper cranks & BB spindle lengths, IMO ...

And, I still have several bikes which have square taper Campagnolo BBs and although I remain a big fan of the obsolete Shimano Octalink BB, if YOU want to install a Road crank with a 52t/53t outer chainring then your best bet is probably to install a HOLLOWTECH II or FSA MEGAEXO BB & crankset on your bike (that is, you would remove the current BB and replace it with whatever suits your budget & aesthetic sensibilities) ...

• Hollowtech II & FSA MegaExo BBs are interchangeable with one another some people have found FSA's BBs to be less reliable than Shimano's Hollowtech II BBs
• so, if you opt for an FSA crankset (which are less expensive than Shimano's cranks AND are generally a pretty good value, IMO) then unless you get the BB in a "package" with the crankset that you may want to pair the FSA crankset with some Shimano Hollowtech II BB cups

But, WAIT!!! Before you buy a new crankset, you need to look at the number of teeth on the smallest Cog on your bike's Cassette-or-Freewheel. The smallest Cog on many older bikes often had 13t. If THAT is the case for your bike, then before you change your crankset, YOU may want to consider simply changing the hub-or-freehub on your rear wheel -- that is, re-lacing the current rim onto a contemporary hub AND then getting an 11-32/34 Cassette for the bike -- or, buying a new wheel off of eBay which has a Shimano/-compatible Freehub ...

• you will need to check the rear dropout spacing on your bike's frame to limit the amount of fiddling you will be doing

BTW. A 48t chainwheel + 11t Cog is a tall enough gear for most people.

As far as shorter cranks ... I would not recommend them for anyone taller than 4'10" tall.

If you aren't counting the time when you may not be moving when you are at a stop light then a 15mph average IS a speed which you should be able to improve on ...

 

[Champ1FC]

Zoinks, that's a lot to swallow! Thanks again for the info. I will continue to see what is compatible with my current frame setup.
My concern with replacing the BB is that I can get one that fits. I like the square tapered crank, it is bomb proof (I've abused it in the last 20+ years) but it is also outdated for modern components. I guess I'm just weighing the benefits of re-outfitting my old bike for thrift, or if the $ would be better spent on a completely new rig. I have to whisper when I say that so "Ed" doesn't hear me. I really love that bike.
My cassette seems to be a standard 7 speed with either 11 or 12 tooth small gear (I tried to count the teeth since it is still on the bike)
More updates as I comb through the parts stored!
Thanks again!
John

 

[Champ1FC]

Ok. Did I mention my current crank-set is a Shimano BioPace? Ancient, I know.
I found a tapered axle, 52/42/30 crank-set on e-bay! I hope it is compatible with my 7 speed chain and cassette.

 

[alfeng]

Originally Posted by Champ1FC
Ok. Did I mention my current crank-set is a Shimano BioPace? Ancient, I know.
I found a tapered axle, 52/42/30 crank-set on e-bay! I hope it is compatible with my 7 speed chain and cassette.

BioPace!?!

Presuming the wheels are original, I'm going to guess that the Freewheel's/Cassette's smallest Cog has 13t ...

And, a new rear hub/wheel + 11-32 Cassette (or, whatever Cassette size you find which has an 11t smallest Cog ... you can buy an 8-speed Cassette & simply lock out the derailleur so that it doesn't reach the 8th Cog, BTW) should probably be high on your shopping list.

BTW. Whether-or-not you need a new BB spindle depends on which brand-and-model crank/BB is currently on your bike.