Take the 2-minute tour ×
Bicycles Stack Exchange is a question and answer site for people who build and repair bicycles, people who train cycling, or commute on bicycles. It's 100% free, no registration required.

I have a stock 2009 Jamis Aurora.

2009 jamis aurora

I'm looking to modify my gear set-up to make climbing hills with large loads a little easier on my knees, as I constantly find myself wishing I had one or more low gears. The specs say the crankset is an FSA Vero Forged 50/39/30 with a length of 175mm. The casette is a 9-speed SRAM Powerglide 950 (11-32). I read on a couple forums that some people had switched out their 30 tooth front sprocket for a 26 or 24, to help out with steep climbs and heavy loads. However, when I called a couple bike shops, they expressed concern that it wouldn't be possible and compatible with the front derailleur.

So I had a couple questions for bike experts since this is my first time really looking at gear systems -

1) Would changing from a 30T to 24 or 26T make a tangible difference on climbs?

2) How do I figure out whether the rest of the bike components will tolerate a 24 or 26t sprocket in the front?

3) Finally, any other solutions for this problem that one might try?

Thank you!

UPDATE 6/19

After incredibly helpful advice from folks in this thread, as well as consulting a number of LBS, I have successfully swapped out the 30 for a 26, without losing my STI levers and without any other problems. The secret lies in adding a 'chain watcher' to help guide the chain back onto the granny if it comes off. Some other adjustments to the front derailleur are also necessary. But with a competent bike shop, it's doable. I haven't climbed with a load yet (this weekend), but from use so far, it shifts smoothly into the granny (but you have to take care you're somewhere in the middle of the rear cassette when doing so), and shifting back up to the middle is also not an issue, though it takes a little longer than before and must be done delicately. With the granny, you shouldn't use the smallest 3 or 4 cogs in the back. Otherwise it works like a charm. Bike shop said it'd probably work just fine to switch the cassette to a 12-34 instead of 11-32 if I wanted lower gearing, too.

share|improve this question
    
Those brake levers are up very high by road bike standards - braking while on the drops does not look as though it'd be very easy. I wonder if that's intentional? –  Mσᶎ Jun 16 at 0:15
    
Thanks for the helpful edits! I don't have a point of comparison, but I haven't had a lot of difficulty braking on the way down. –  user1145886 Jun 16 at 3:22

3 Answers 3

You can easily put a 26t chainwheel on the front crank. I've done that on a couple bikes, because 30/39/52 makes for a stupidly redundant set of gears with anything like a wide range cassette on the back.

It will likely take some tweaking of the front derailler setup to get it working properly, switching to a 50 from a 52 can help with that.

It isn't an out of the box recommendation since you are slightly exceeding the manufacturers specifications for both front and total ranges, but in practice it works just fine. I would recommend installing some kind of chain keeper like the Deda Dog fang. This will help avoid dropped chains when shifting from the middle to small chainring.

As far as changing the rear cassette goes, you should be able to use a Shimano 9speed HG 12-36 and it's generally just cheaper to buy the whole cassette than individual rings. If your current cassette isn't worn, you can mix and match rings to build a custom cassette. However, switching cassettes doesn't really solve the problem as well as a smaller chainring would IMHO. A good granny will give you a few choices in climbing. If you go to just the 36t in the back, you've only added one lower gear and you'll be "stuck" there.

If you are doing a lot of loaded touring, I would recommend replacing the entire front crank altogether. Standard road triples 130/74 BCD don't make a lot of sense for touring. A 110/74 or even a 9 speed MTB crank 22/32/44 will give a more useable set of gears. Personally, I would take a long look at the Surly Mr Whirly crank for touring. It uses modern bearings and you can get a replaceable spider to allow for whatever front gears you like.

IMHO, the old MTB standard 58/94 is ideal for loaded touring. 20/30/42 allows you to use a relatively close range on the back and still get all the gears you need. If you do go this route, you might need to replace the front derailuer as well.

Keep poking around on Sheldon Brown's pages, there is lot's of good info there.

share|improve this answer
    
Thank you! The crankset is already a 50/39/30, so I wouldn't need to swap out a 52 - only the 30 (which I take it is also called 'the granny'). Are you recommending changing both the rear cassette and the granny, or do you think the granny is a sufficient start? I'm not doing a lot of loaded touring yet, so I will likely defer a major overhaul like that until down the line. –  user1145886 Jun 16 at 20:55
1  
I would only switch one thing at a time and the first would be to a 26t in the front. If that's still not low enough, then the bigger cassette. I really think all you need is the 26t on the front, it makes a big difference. –  Fred the Magic Wonder Dog Jun 17 at 0:50
    
Just stopped by an LBS to ask them to swap the 30t for a 26t, but after much hesitation, they politely recommended against (read: refused) going out of the specs for the rear and front derailleurs and recommend a different rear cassette instead. I stopped by another LBS afterward to get a second opinion - they said it wouldn't be an issue without a second glance (or a close look at the bike, really), so it kind of worried me. I might try a 3rd one later this week to see what they say. I'm not against going out of specifications if folks who have tried think it would work with minimal hazards. –  user1145886 Jun 17 at 2:23
1  
Perhaps the second shop didn't look closely at the bike because they've done the same for many others. It's a very common modification and there's nothing very unique about your bike. –  Fred the Magic Wonder Dog Jun 17 at 15:05
    
Went to LBS #3 today and they were much more helpful and clearly informed. The person I spoke with was confident a 26t would work, but recommended adding a chain watcher (is this the same as a Deda dog fang?). He said 24t might work too but would be pushing it. Either way he said 3 or 4 cogs in the back wouldn't be useable with the granny, but they're redundant with the middle ring anyway so no biggie as long as I'm careful. Now I just have to figure out where to find a steel 24t or 26t chainring... –  user1145886 Jun 18 at 5:49

Swapping chainrings would definitely help on climbs. Your current 30-32 bottom gear is reasonably low by touring standards, with a development of 30/32*π*0.68 = 2.0m, where the 24T chainring will give you ... 1.6m (20% reduction). You'll really notice that. 26T will shift easier and still be significantly lower.

Really the only reliable way to find out whether the rest of the components will work with it is to try. At worst you'll find that the front derailleur isn't really long enough to cope with the small chainring and the chain runs on the bottom of it for some of the smaller cogs on the cassette. Which is workable for many people - you end up with the granny ring only working with the biggest 3 or 4 cogs on the rear cassette. Shifting will likely be more difficult than you expect, especially getting out of that chainring back into the middle.

Doing that shift while climbing will be tricky, and that's what kills it for many people. You only get one chance, and if you don't make the shift you have to drop back, recover the bike, speed up and try again. Which is annoying.

To mitigate that it can help to change front derailleurs (basically buy the front triple derailleur with the widest range you can find), and drop a few teeth on the middle chainring to make the shift easier. That is at the cost, obviously, of harder shifts from the middle to big chainring since you've increased that gap.

If you can afford it, I think it's well worth buying a 26T cog and seeing what happens.

Other options

You can get some benefit from a bigger cog on the cassette, but the jump from 32T to 36T is not particularly large and you will probably struggle to shift that with your current rear derailleur. The obvious fix is a Rohloff hub :)

share|improve this answer
    
The current RD is a deore - it shouldn't struggle. –  Batman Jun 15 at 23:47
    
I kind of agree that it shouldn't struggle, but I've also spent time trying to get one working after my housemate swapped to a 12-36 on a similar bike. It worked, but it was a PITA to get it there (extra links the in the chain, lots of adjustment)... and a month later he decided it wasn't enough. –  Mσᶎ Jun 16 at 0:13
    
I think futzing with the rear derailleur is a lot easier than futzing with the front, especially if you dont set the jumps properly. Also, a Rohloff wouldn't work in an Aurora - it has vertical dropouts ;) –  Batman Jun 16 at 6:12
    
@Batman 32-36T suggests two extra links needed. And don't make me explain how chain tensioners work again or I'll put you in the slow class (max 44T chainring) :P I suspect no futzing would be needed, but ... there's only one way to be sure! –  Mσᶎ Jun 16 at 7:23
    
Most of the time, I ride an old Giant boulder with a 42T chainring, so bring it on >:) [Its my commuter/around town/nobody's going to steal it bike]. But yes, you may need an extra link or two, but you could probably get the bike shop to do the whole thing for a few bucks anyway (given you need the cassette tool and stuff). –  Batman Jun 17 at 3:30

I'd start by swapping the rear cassette so that you have lower gearing (i.e. bigger gears in the back). The rear derailleur is what determines the biggest cassette (set of gears in the back) you can put on the bike (since they have to have enough tensioning ability to regulate the chain change for big gears). There are wide range (SGS), medium range (GS) and narrow range (SS). In this case, its a Shimano Deore derailleur, which is SGS. Thus, you can stick on a bigger rear cassette if you can't handle the climbs as is. Maybe a 12-36t or something.

I don't think I'd swap the chainrings out - 30t and 39t are already pretty low for most applications, and you need to swap the other chainrings out to smaller things in that case, since the front derailleur can approximately only do jumps of 10t reliably at a time. This is also pricey. That being said, the Surly LHT ships with a 26/36/48, so it might be worth a shot. But I'd start with a bigger cassette.

share|improve this answer
    
Thanks for this helpful comment. Would I have to switch out the whole cassette or is it possible to switch out only the 32t sprocket for a 36t? I've been using Sheldon Brown's gear calculator to try to quantify the difference and it looks like keeping everything else the same, but switching out a 32 for a 36, would give me a gain ratio of 1.6 on the 30/36 gear -- which is identical to what you get at 32/26, and only slightly higher than the ratio on the 32/24 combo (1.5) (or respectively, 22.5 gear inches v 21.9). –  user1145886 Jun 16 at 3:37
    
@user1145886 it's the whole cassette. It is about $US50 online... Harris Cyclery was the first google result –  Mσᶎ Jun 16 at 3:53
    
Harris Cyclery is a bit pricey. Chain Reaction Cycles sells the Deore HG61 cassette for around 28 dollars. –  Batman Jun 16 at 5:07

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.