Trek Al

I looking to modify my Trek 520 touring bike to use for randonneuring. It is geared low with a Sugino crank at 26-36-46 and using the Cyclotouriste 13 cassette from Harris Cyclery that goes from 13 to 34. It computes at 95.5 to 36.5 gear inches with a 170 mm crank. This works great for pulling loads up hills but is lacking in speed on level or downhill.
I looking at changing the cassette to a 12-25 which would give me a gear inch range of 49 to 103 or a 11-23 cassette yielding 54 to 112 gear inches.

I've not done any randonneuring before, but don't think my current set up has enough in big gears. Don't want to try a 200k event and suffer because of the gearing. The cassette swap is a fairly cheap and easy change.

Anyone have an idea on what would be the best?

Al

bmike

You'd suffer if you can't push big gears?
Most of these choices will be personal - and reflect the local terrain, your fitness, etc.
And how you'll feel @ mile 90 and 100 and 110 and 125.


I run a 30/46 double with 13/29 on the rear.
This gives me 27.7 to 94.7 with 700x28 - which is lower than your touring setup overall.
Most of my riding is in the 46...

For me a wiser expenditure of energy is fighting terrain rather than trying to overpower the wind.

I used to swap stuff around all the time, tuning my gearing per the event.

Now I just generally leave the 30/46 on and switch wheels. Not that I gain anything by that - but I go to a 13/26 instead of the 29.


YMMV

LWaB

26t chainring to 23t cog doesn't give a 54" gear.

StephenH

Well, to each his own. My Raleigh Sojourn has 50/39/30 up front and 11-34 in the rear. I almost never use the big ring. I have to be going about 30 mph before I need it, and unless I'm going downhill, that just isn't happening. With the 39-11 combination, I can only use that with a tailwind and that'll be pretty comfortable cruising at 21 or 22 mph (and my average for a ride normally won't be over around 16 mph or so). Maybe you're just faster and stronger than I am and need bigger gears, but I suspect I could get along with your gearing just fine on a brevet. I'm more apt to run out on the low end.

Barrettscv 

You will need to change two of three of your speed factors to increase your speed range more than 30%. You can change your crankset to one with larger chainrings. You can change your cassette to one that includes a 12t cog. ...Or you can pedal faster. You will need to select two.

I'm assuming your pedaling at 80 rpm most of the time, and your gearing will begin to limit you above 22 mph. That's still faster than most long distance cyclist will travel on the flat. Downhill travel is another situation, and I assume you have some sustained downhill sections near Knoxville. Keep in mind that your average will be in the 14 to 19 mph range for any distance greater than 100k. Slower if long hills are involved.

I stop pedaling at 30 mph with a fast cadence of 100 rpm on downhill sections. Faster than that and gravity is going to have to do the work. How fast do you want to be assisting gravity?

I would consider a 12-27 nine speed cassette. However, that will only add a little less than 2 mph to the speed range while on a 44t chainring and very steep climbs will be difficult.

Another idea is to install a Shimano Tiagra 50-39-30 triple and keep your 13-34 cassette. The 50t chainwheel will add 3 mph over the 44t.

These cranksets can be found on ebay for about $95 with the BB adding about $25 to your costs.

Changing both the cassette and the crankset will add 5 mph at 80 rpm.

...Or you can pedal faster. Select two.

Trek Al

Barrett - Thanks for the detailed reply.

You are correct in getting sustained downhill in this area. I quickly max out the gears on any downhill and lose the ability to pick up some speed. Still thinking about various things to try as I can buy just the large chainring. They are available in 50, 52 or 53 on ebay in the $50 and less range.

Think I'll buy a 50t to swap out and see what it does.

Al

Barrettscv 

That would be a good test. Just be aware that the front derailleur would need to be repositioned higher on the seat-tube and that downshifts might cause problems. The derailleur is designed for a certain change in chainwheel diameter with each shift and increasing the diameter of a chainwheel will impact the shift quality.

Having said that, it just might shift perfectly.

Michael

slide23

What Mike said (hey Mike, long time no see, Burlington repruhZENT!)( ). I find gear range to be far more important for randonneuring, rather than being able to dial cadence. I am currently running a triple crankset and 11-32 cassette for 21 to 108 gear inches. This serves me well when the hours go long, the winds run high, and the hills get severe, and when all three factors come together. An added bonus is that I can haul a trailer on other errands.

I wouldn't really sweat about running out of top end when it comes to randonneuring. But to make this relevant to you: are you really running out of top end on your descents? How much speed would you estimate that you're missing? I ask because I recently switched from a road triple to a mountain triple. I have actually not been able to hit the same top speeds on the road crank that I was getting on the mountain crank.

shelbyfv

If you are using 9 speed, why not just a standard 11-32 for about $30?

10 Wheels

or a 11-34 $19
https://www.jensonusa.com/store/produ...ssette+Oe.aspx

Richard Cranium

Whew - I'm glad that problem is solved. Its tough to find good gearing in modern bicycles. I have no idea how those old guy do it with those worthless 52-39 crank mated to a 13x28 freewheel. What cavemen -sheesh!

Barrettscv 

Ahhh... the good old days;



But this is better;

Hydrated

Al,

In concentrating on gearing, you are overlooking a crucial factor in the equation: your frame.

I have been riding a Trek 520 for the last 27 years (I bought her new in 1983) so you could say that I have a few miles of saddle time with that frame. And your newer 520 is basically unchanged from my older one... the frame is the same according to the boys at Trek. Only the components have changed over the years.

If you attempt to push big gears on that frame to any real degree, you will discover that the 520's frame will bend and wrap like a wet noodle. The very properties that make the 520 ride like a Cadillac also make it accelerate and climb like a slug. All that frame flex represents wasted energy... so you tire yourself out for nothing. The only efficient way to ride that frame is to spin smaller gears and avoid inducing the frame flex that mashing produces.

I love my 520 and she still rides like your Granddaddy's Buick. I commute on her 20 miles daily, but it's not the best brevet frame in the world. If I ride the 520 for a few days and then jump on my Surly Pacer it's like the Pacer is an anti-gravity bike on the hills! The 520 slogs up the inclines... the Pacer accelerates up them.

Now all of that begs the big question:

Would I ride that 520 on a brevet?

Yes. I would. But I would ride that bike with the knowledge that you have to ride it a certain way in order to take advantage of the bike's strengths and avoid its weaknesses. As long as you're smart about it, you'll be fine on your 520 for long long distances.

zzzwillzzz

you mean 52-42, them were the good old days, a 39 is practically modern

Barrettscv 

Or, the 52 & 49 half step with a 13-24 five speed freewheel as shown above. That was OE 35 years ago.

Captain Blight

Okay, give this a try:



26/45/48 gives pretty close to true half-step gearing, less gear duplication, you don't lose anything on the low end and gain a bit up top.


By the way, I think Sheldon's gearcalc is crap, the "visual drivetrain comparison tool" at Kstoerz.com is VASTLY superior, though it still needs more tire-size choices. Still and all, it's a fun tool to play around with.

StephenH

Gears schmears, back in my day, I didn't need no stinkin' gears, I just jumped on the ol' Worksman and rode 132 miles.

Carbonfiberboy 

No, no, 52-48 was the good old days, half step gearing. Did my first century on a half-step bike.

badamsjr

I have 24/34/52 11-34 9spd on a couple of my road bikes, and have no problem with the shifts. Low gears are presently a requirement for me, but I hope to be able to put in a LOT more saddle time in the near future. Retirement is looming large!

Hydrated

Is that a motorcycle helmet hanging on the handlebars?

shorthanded

do you need to fly down hills pushing the big ring?

i dunno.. i use a 44 big ring and don't run out with a 12, i just coast when i run out of gearing, and we have some good hills around here, routinely hitting 30+. never seemed a problem to me, really- and i know i push from about 36 to 99 inches with that setup.

i'd certainly worry about having a good range for comfortable spinning and climbing over speedwork FIRST. i honestly almost never use 44 12- but i think i might sping around 100-120 for cadence before i consider it 'spinning out'- so maybe that explains the discrepancy.

clasher

Try some longer rides with your current setup so you can have a better idea of where you need to make changes. I spend hours dicking around with gearing calculators but I'm fine with my current hybrid setup on 100k rides... 11-32 with a 52-39 up front. I'm going to try and do some randonneuring on my bike, and when I swap out my cassette I'm going to get a 12-36 29er cassette so I can get some lower bailout gears. Starting over I'd get a compact double too. I did set the bike up with a long-cage deore so I could run the bigger cassettes.

Richard Cranium

Chances are - if you're dicking around with a calculator, you'll be dicking around when you shift.

My point, at least my original point was that modern bicycles often offer at least 16 or 18 or 20 drive train combinations -meaning you have to be a bit dim to not be able to find a usable gear.

Ok OK, I know some skinny-ass pimple face geek is going to say he usually rides a straight-block but now he needs a 28 for the San Fran crit he's going to win.

But c'mon, can't we all agree that if you have a newer bike with 18 or 20 gears, the problem isn't the gearing - its you?

PS there is no such thing as "distance this" or "distance that" - either you use equipment that works, or doesn't - and it isn't a case of 10, 50, or 500 miles to argue over.

proceed to hate mail below.........

MileHighMark

Think of it this way:

What happens on a 200K when you don't have low enough gears?
What happens on a 200K when you don't have high enough gears?

I'd venture to guess that the former would be worse than the latter.

On my commuter (SOMA Saga) I run 24/36/46 and 11-32. I rarely use the granny ring, but I use the big ring quite a bit. Downhills aside, I've never found myself yearning for a taller top-end. On the flats, my speed is limited by my lungs, legs, and how much crud I'm carrying in my panniers.

StephenH

I do find myself using lower gears farther into a ride, so yes, distance does make a difference.