Bike Gremlin

Hello,

I've got a bike with 700 (28") wheels. It is used for commuting (main/only transport actually), but I occasionally take it into mountains on dirt walking paths. The problem is climbing really steep hills - it forces me to walk sometimes. I'd like to put some lower gears (since I practically never use the highest two gears).

The bike has Shimano Acera shifters, derailleurs etc.
Gears are front: 48 - 38 - 28, and 11-13-15-18-21-24-28-32 (8 sprockets) rear.

It would be nice is if there was a 24 front, or a 38 or something like that rear sprocket. Or both. Everything is fine, I just lack that ultra-slow gear for really steep climbs. Perfect would be to switch the rear 11 with a bigger than 32 (like 38) sprocket.

Are there compatible front or/and rear sprocket sets to change this?
What do you suggest?

biknbrian

34 seems to be the biggest commonly available cassette gear. I thought Harris cyclery actually sold individual cassete cogs if you don't want to change the whole thing, but realistiaclly you can probably pick up a whole cassette from Nashbar, Pricepoint or another discount place for minimally more money. If you knew the BCD values of your crank you could also probably buy a smaller ring, but you have to know what the BCD is in order to know what sizes you can run.

zukahn1 

+1 If you know your chainrings BCD and type 4 or 5 hole. You can shop around on line and find chainrings from the low 20's to high 50's for most cranks at fairly cheap prices. I have bought good chainrings for as little as $6.

strock 

+2. If your inner chainring has a BCD of 74mm, you can just swap out the 28t ring in favor of a 24t ring. If the BCD is 64mm or 58mm, the other relatively common sizes, you can go even smaller. Since you've already got a 32t large cog, you'll get more bang for your buck by changing the inner chainring than by changing the large cog. As biknbrian notes, 34t is the largest commonly available large cog. You can get 36t, but I don't think you can get 36t on an 8-speed cassette. (If wrong, I'd be happy to be corrected.)

fietsbob

yup, 24/34, a 0.7:1 ratio is about it.. the next step would be an electric assist motor..

bud16415

Take a look around the Touring forum. There are a lot of good threads on gearing changes there. Touring riders are very gear conscious as they mostly have 700 wheels and carry quite heavy loads on the bike. Many switch out to a mtn bike crank set. 44,32,22 is common.

My bike I run a 12-36 rear cassette but it is a 9 sp, not sure about 8. In the front my lowest chain ring is a 26 t and the 26 / 36 combo will get me up most everything.

cycle_maven

Yeah, much smaller than 24 in front and 34 in the rear has you spinning like mad to stay upright, and inadvertently popping wheelies on steep pitches.

dscheidt

Most acera chainrings are riveted. If yours are, you're stuck needing a new crank. (and maybe a bottom bracket and a derailleur and a chain). 8 speed cassettes with a 34 toot hbig ring are common, and probably don't require any new parts. (a chain might be a good idea, if yours is worn, but 8 speed chains are cheap). That's about a 6% reduction in gear ratio, which isn't a whole lot, but it's better than nothing. If that's not enough, then look at a new crank.

Jeff Wills

Ditto to all the above. My low gear on my recumbent is 24 teeth on the chainring, 34 teeth on the big cog. I rarely use it, but when I do, I need it. I can crank along at barely above walking pace.

dbc

If your front chainrings are not replaceable, I recommend swapping out the crank for an Alivio 42-32-22. Check your LBS for other options and advice. Some other minor work may also be necessary for the swap.

Bike Gremlin

Thanks all for good advice.

I'll ask about 11-34 rear for a start. If it is available, I'll mount it in the spring (not riding forrests much when it's cold and wet).
I'll also look for the above mentioned Alivio 42-32-22. Sounds just perfect, just will see about cost.

Bike Gremlin

Having calculated gear ratios, 42-34-24 crank is best solution at the cost of some 20 - 25 euros. Will put it in the spring when I start riding mountain trails more often again.

noglider 

I just stumbled upon this thread. I don't agree that changing the bike is the answer. You already have an extremely low gear. Have someone look at you while you climb hills on your bike. You can probably learn how to do it better. Unless you're old or disabled, you should be able to improve your climbing ability.

The trouble is, you've come to a mechanics' forum, so everyone provides a mechanical solution to your problem. But I think your problem is more of riding technique, not mechanics.

Bike Gremlin

Gears are just fine for 99% of paved roads. What gives me trouble are mountain paths that are too steep. On old mountain bike I had an extra, ultra low gear for such situations. Since I'm almost never using the top 2 gears now (48 + 13, or 11), thought it would be OK to use smaller front sprockets.

But your point is still very good - never thought of that! Compared to my friends I'm quite fast uphill, but none of them is a "pro". Must ask a co worker who is a cycle official to have a look once. I'm not disabled, nor too old, maybe just ugly to look at, but he'll have to cope with it somehow.

bud16415

I agree with your first assessment of what you want. Sure we all can improve both technique and strength. We all bring something different into the equation. But if you are looking for lower gearing and feel you have unused gearing at the other end why not lower your overall gearing. If you can now handle a 10% climb and new gears let you do a 15% when you get better or stronger you might want to go after a 20%. It is in no way cheating using lower gears because what you gain in torque you make up for by spinning more revs. The work in the end is the same. Your body will tell you when you are spinning to fast and burning out on the spin end, just like it does when you just can't exert any more force mashing.

IMHO its always better to take a climb in a lower gear if you have to than walking and pushing.

noglider 

Perhaps your slopes are beyond my imagination, but I climbed some hills that I thought were steep with a fully loaded touring bike and without modern gears. It's kinda like I'm saying, in a scratchy voice, "Why, in my day, we rode to school in the snow uphill both ways with bare feet, and we liked it that way!"

I hope I'm not coming off that way.

Bike Gremlin

No, it is very reasonable. Everything needs to be done right. Training athletics, I learned how to run correctly which improved my speed. Same goes to cycling - I took it for granted, but never read a book on technique or practiced with someone experienced.

noglider 

Another thought: it's only relatively recent that walking a bike up a hill is considered unacceptable, and there's really nothing wrong with it. At a certain steepness, it uses less energy to walk than to ride, because wheels want to roll backwards, but feet don't, and you spend energy on preventing backward movement on the bike.

bud16415

Hey Tom

I might have heard just a little of that scratchy voice in your first reply, J You and I might have went to the same school, mine was up hill both ways also, but we used cardboard in our shoes to keep the snow from coming thru the holes. Barefoot ! You guys were tough. Kidding aside your points were well taken.

I ride the same roads and hills as I did as a kid 45 years ago. Only back then the bike was a single speed coaster brake Schwinn that weighed a ton. The age and weight thing I'm sure plays a part in my gearing now. I remember back then we called it pumping (standing to peddle) and you would hit the base of the hill with all you had and pump till your speed hit zero and then a row of kids would jump off and push the rest. No one thought less of the kid that pushed but the kid that made the top was legendary.

About a month ago I did a 40 mile charity ride with a lady I know and it was her first time on a bike this summer and about the 30 mile mark there is a mile plus fairly steep incline. Her bike had a triple but was geared pretty high still and I had my tour bike and could have rode it out. She ran out of gas after a couple hundred yards and stopped so I did also. And we walked the rest. Riding was maybe 5MPH and walking and pushing was about half that. So when you really look at the time difference it was at most 5 to 10 minutes. The walk was actually very refreshing and as you mentioned not fighting the roll back factor was quite easy. Giving the legs a stretch at that point compared to burning them out on the climb I'm positive we made back that 10 minutes plus some on the last 10 miles. I totally agree there is no shame in walking your bike and in some cases it could be the wise move.

Actually I feel both answers are correct for the OP. More gears can't hurt you having them and for sure the most efficient riding style should be everyone's goal. For my own practical low gear I have tried gearing as low as 17 gear inch and that was just too low. I'm at 19 gear inch now on a loaded tour bike and anything lower I think would be counterproductive for me.

Bike Gremlin

Local mountain has some lovely tracks for hiking (and riding). I hate when I stop on a part that is ultra steep, since it is harder to go on riding through the rest of the climb that is not that steep after walking and pushing the bike. It seems much easier when I put it in ultra-low gear for 50 meters, then go back to normal low gears for the rest of the climb, than dismounting/mounting on the bike and starting from 0 km/h in the middle of a climb.

But lower gearing will wait for the spring, now the mountain is perfect for hiking - bike is better for hot weather.

rwortman

I remember back in the day when race bikes had 5 gear rear clusters, the advice was to gear the bike for "normal riding" and walk the damn thing up the hills that were too steep. Maybe the SOTA clipless pedals/shoes have done away with that thinking. I would think it is still perfectly OK off road where you will be wearing at worst a pair of SPD shoes.