coddy

Greetings to all,

I'm looking for a bit of advise please.

I have recently bought my first touring bike (Dawes Ultra Galaxy 2005) and I am a bit concerned about the gearing with regard to hill climbing. I've tested the unloaded bike out over the English Lake District mountain passes (Honister/Newlands) and managed to get over them without having to leave the saddle (just - bleedin steep hills..!! ). This would not have been the case if I was fully loaded and would like to improve the lower end gears.

My current transmission set up is:

Chainset: Shimano 105, 30-42-52T, 170.0mm
Freewheel: Shimano HG70 (Hyperglide 12-34)
Derailleurs: Shimano XT rear; Tiagra front
Gear levers: Shimano 105 STI

Looking around t'internet a chainset of 48 38 28 seems popular. There is a good article on peterwhitecycles site suggesting a 48 38 26 or 24 set up : "most popular chainrings are 48 - 38 - 26 and 24 tooth replacements for Shimano's Ultegra and 105 triple cranks"

The high gearing on the bike is great and I wouldn't like to lose the high gears but I could well do with more gearing lower down for any Alpine type touring. My touring will be based on camping rather than use of the credit card.

Is it possible just to change the 30 tooth inner ring on the chainset to a 26 or 24 tooth or would it cause problems?

All advise welcome, mon amigo's.

Cheers
from

Dave - clueless in the UK.

moxfyre

It's probably possible to replace the 30 tooth inner ring with a 26 or 24, assuming the bolt circle diameter is smallest to fit one (do you know what the BCD of the inner ring is?)

The problems you're likely to encounter have to do with the derailers:

• Your front derailer cage may not be "deep" enough to deal with the 26 or 24 tooth ring. The difference between your large and small chainrings would then be 52-26=26 teeth, which is very large. I don't know if there is any front derailer made that can accomodate this, but I could be wrong. Anyone know what the Shimano LX/XT derailers can do?
• The rear derailer needs to be able to "wrap up" the extra loose chain when using the smallest ring. This is called the capacity of the rear derailer. If you have a 52T big ring and a 32T big cog, and a 26T small ring and a 12T small cog, then in theory you need a rear derailer capacity of (52-32)+(26-12)=34T. In practice, this isn't necessary since you would only use the small chainring with the largest cogs!!! But you still need a large-capacity rear derailer such as the Shimano Deore XT.

I hope this helps. Try looking on SheldonBrown.com for exact numbers. Or maybe someone else knows more information about derailer models off the top of their head!

fsor

I believe that the bolt circle diameter of your current crank will prevent meaningful reductions in the small chainring. As moxfyre pointed out, even if you could drop that ring to a 24 or a 26, you would have such a gap betwen rings that it is hard to get a front derailleur to shift well. Buying a smaller big ring gets you into the money spent catagory. I have run two bikes using Sugino 24,36,48 fronts using a 105 triple front and an Ultegra triple front. They both work well....not as smooth as 30-53 triples but they are reliable. With a 32 or 34 ring on back, you can just about climb trees. The Sugino triple is about 80$ US and has higher Q but is a quality part in my opinion. It does not work with mountain bike front derailleurs.....the 105 triple seems to work the best, your Tiagra should be fine. ymmv

HardyWeinberg

Re preserving the highest gear, it's worth pointing out that 48/11 (if you can find an 11/34 cassette) is a bigger gear than 52/12 (barely), so a 48/38/28 set of chainrings doesn't have to cost you your highest gear. Also, might be worth looking into the price of individual chainrings vs the price of a whole crankset.

Al1943

I replaced my wife's Ultegra 52-42-30 with 49-39-28 chainrings. It required a bit of fine tuning to make it shift smoothly but no problems now. If you replace the middle or big chainring it would be best to use chainrings with ramps and pins designed to run in a triple crankset, like TA Alize, FSA, or IRD. It will also be necessary to lower the front derailleur and if you have a "braze-on" type it may require some creative engineering to get it low enough. No problem if it is a "clamp-on". If you plan to replace only the 30t you probably won't be lowering the derailleur. A 26 or 28 would be an inexpensive and easy expriment so you might as well try it.

Al

HiYoSilver

You should be able to put a 26 ring on front without too many problems. That would drop you down to 20GI, from your current 24 GI low. It's about 2 gears. If that is not enough then you'll have to swap to a 24-38-48. I don't think touring riders go lower than a 24 ring.

wagathon

You have a low 30x34 now, so, if you want lower, my suggestion is to replace the road crank with a mtb crank. That will give you many more closely spaced and commonly usable gears.

You may even wish to tighten up the freewheel to e.g., max 27T cog. For a 24x27 combination, for example, you are about equal to your current 30x34 but going with a mtb with a 22 lower chain ring, a cluster to 27T might be good.

The only downside to switching cranks is that you lose the 52-12 high gear. Even so, an e.g., max 48 or 46T chainring still provides a big range.

If you like the idea of a mtb crank and still want a high gear, you could always put on a 11T small cog on the cluster. A 48x11 gear ratio is barely any different from a 52x12.

cyccommute 

His front derailer won't have a problem. I have a 46/34/22 that shifts just fine with a Tiagra front derailer. I'm not convinced that the Tiagra isn't a better derailer than an Ultegra.

For Coddy: Go to Sheldon's gear calculator
and run some numbers. Your 52/12 high gear combination is higher than what is commonly used for touring...now. It used to be the standard. Try a 26 or 24. I've done that kind of combination in the past (52/40/26 with a 12-34) and had very little problem. The XT will handle the chain wrap just fine.

coddy

Wow...thanks for all the useful advise everyone.

The tip to go to an 11-34 cassette to compensate for losing the 52T sounds like a good idea. Could I just remove the 12T from my existing cassette with an 11 or would I have to replace the whole cassette?

The Dawes Ultra Galaxy 2006 comes with a Sugino XD3000T with 48 38 and 28 tooth chainrings so Dawes seem to have recognised the need for lower gearing. This was highlighted in a review by one of the cycling mags. As Dawes have opted for the Sugino and seeing that it works well for you fsor, this is probably the best direction for me to take. I've just had a look around for a Sugino replacement without any success as yet. I don't mind splashing out on a complete Sugino 24,36,48 if I can find one over here.

There is a brand new one on Ebay at the moment but it's a 48/38/28...... Ebay : Sugino 48/38/28


muchas grathias.

Dave.

coddy

Thanks Mad bike riding scientist.

The smaller 26 or 24 ring might just be worth a try then before going down the Sugino route.

ps. I can't make head nor tail of Sheldon's calculators. I'll have to try and get my head around it.

fsor

I have been convinced that 24 or 26 chainrings would not fit the bcd on your current crank but it seems that others have done it and that I am incorrect. If that is the case, I would say give it a try. The Sugino triple cranks that I have seen use a square taper bottom bracket and that might not be the same type bb that you currently have. Replacing the BB adds to the cost of going to the Sugino. Sugino are pinned and ramped and shift fine with Shimano btw. I would not worry about the difference between 11 or 12 on the high end......if you spin out of a 12, touring, it is time to coast.

Shaman

Shimano states that the 105 derailler is made as follow:
small gear to middle gear: 12 tooth max offset
middle gear to large gear: 10 tooth offset

This does not mean you cannot push the limits a little, but Shimano has warned you about possible performance hits in spec'ing it this way. That is why the 52/42/30 is so common.

An 11-34 cluster is common. I've also seen some with an exagerated large sprocket in the rear. This might be easier and cheaper to do than changing the front sprockets.

coddy

Hmmhh. Food for thought.

Dawes Ultra Galaxy 2006 uses a Shimano UN53 sealed cartridge BB. Mine has a Shimano 105 splined Octalink ......Aye it's starting to look a wee bit costly although the UN53 is pretty cheap at 15 pounds stirling, fsor.


I'll do a search on the exagerated large sprocket's, Shaman. The Shimano guidelines given might make the 26 a safer option than the 24. Thanks for the advise.

cyccommute 

The calculator is really pretty simple. I like to work in gear inches because that's the way I learned how to figure the gears. For example a gear combination of 52 on the front and 12 on the back would be the same as riding a wheel with a 117 inch diameter. This means that for each revolution of the wheel you would travel 117 inch *3.1418 (the circumfence of the wheel). What this means is that when you are moving the crank just a little bit, you are making the wheel (and your distance) move a lot! This makes going downhill really easy because you don't have to put a lot of effort into pedaling to make the bike go really far.

On the other hand, if you are in a 24 on the front and a 34 on the back, it would be the same as riding on a wheel that is 19" in diameter. Now you have the opposite effect. When you move the crank a whole lot, the rear wheel moves just a little. Now you don't have to put as much effort in moving up the hill.

Everything inbetween the top gear and the bottom gear is to make the transition from top to bottom smoother. You could just do a two speed bike but what's the fun in that?

coddy

A whole lot clearer.

So the calculator makes it clear the effect of any intended changes (either to front/rear or both) and helps to determine which changes are most suitable to achieve the gear range required. The bigger the increase in gear inch range, the less likely any change would be likely to work depending on the parts fitted.

I've gotta find the right parts now. What do you reckon? A 26 inner ring and an 11-34 cassette? The 11 at the cassette bumps the gear inches to 127 from 117. The 26 inner reduces the GI to 20.6 from 23.8. Quite a big difference

Do Shimano do a 26 chainring that I can just replace one for one with the existing 30 or do I need to look at other manufacturers?

coddy

Here's a bit more input on the subject.

Front and rear derailleur capacity

Manufacturers are cautious with their specs and you may be able to push mechs further than they say. Maximise your rear mech's capacity by minimising the length of your chain - see Modern gears and chains.

To check if you can fit a smaller inner chainring, put the chain on the smallest rear sprocket and measure the gap between it and the bottom of the front mech cage. You can reduce the size by one tooth for every 2mm.

https://www.highpath.co.uk/cycles/notes/07.html

https://www.highpath.co.uk/cycles/index.html

Inner chainring size

If you've followed the development of front mechs described above, you'll realise that inner chainrings can be made almost as small as you like. It hardly matters.

There are limits, but don’t be too bothered by what it says in the catalogue about mech capacity, i.e. inner–outer difference. Manufacturers must allow for variations in chainstay angle (see below) which has a significant effect on capacity, as does your choice of outer ring. If these factors are well within limits (seat angle not so steep, chainstay not so horizontal, outer ring not so big) you can generally get at least 24T out of a 22T capacity mech, sometimes 26T. Remember: if your outer ring is on the small side for your mech, the inner can be even smaller still, but if the outer is big, the inner must be bigger.

If you’re wondering if you can fit something smaller to an existing setup, select inner ring and the smallest rear sprocket you actually want to use it on (probably near the middle of the cluster). Measure the clearance between the underside of the chain and the bottom of the cage. Divide the millimetres by two and that’s how many teeth you can reduce by. The 2mm per tooth rule is also useful to see if you can make the whole chainset smaller – without the tail end of the mech fouling the chainstay (or a cable running the old-fashioned way, just above it).

Provided you keep to the guidelines above it’s okay to fit another brand of chainset (but avoid really old designs), or alter the chainring sizes from standard issue. You can go as small as 24,38,48 on a Shimano road chainset. For more on that see www.highpath.co.uk.

https://www.ctc.org.uk/DesktopDefault.aspx?TabID=%204068

HillRider

Shimano road triples have a 74 mm bolt circle for the granny and will accept down to a 24T granny ring. I've substituted 26T granny rings for the stock 30T on at least a dozen Shimano cranks including 7, 8 and 9-speed versions and they all worked fine. I expect a 24T would work but I've never done it.

If you do the substitution you will probably not be able to use the granny with the smallest two or three rear cogs as the chain will be too slack. This is no loss as at that point a 42 x something will give the same gear ratio.

Any makers granny ring will work and you don't have to use Shimano's. All granny rings are flat and don't have the shaped teeth and pins the larger rings do.

moxfyre

Coddy: I imagine a dealer could get you a 26T Shimano chainring, but I've never seen one sold by itself on a shelf. I'm guessing you're in the UK, but anyway Nashbar sells 24T and 26T chainrings cheap... https://www.nashbar.com/profile.cfm?c...eid=&pagename=

I've never bought a Nashbar chainring but have had excellent luck with their other drivetrain products, including chains (rebadged KMC), brakes (rebadged Tektro), and fixed gear hubs (who knows...).

coddy

Thanks a lot, Hillrider.

Everything I needed to know.

coddy

I'm from up north in the UK, moxfyre.

Very good of you to help out. Hopefully I'll be able to source one in the UK but I've bookmarked Nashbar and will order it from them if I have no joy.

cheers
Dave.

mechBgon

I like 7075 T6 aluminum chainrings. It's a relatively hard alloy that wears well and is generally less prone to gouging and chainsuck than 6000-series, and runs quieter than steel. So if you anticipate using the granny ring a lot, then it could be worth hunting down a 7075 one.

If you can find a 5-bolt 74mm Shimano XTR inner chainring, they're a good choice, not only 7075 aluminum but nickel-plated as well. Example: https://www.cambriabike.com/shopexd.asp?id=24916 for a 26-tooth.

I just replaced my classic DeoreXT crank (48-38-26) with an Ultegra Octalink-type 52-42-30 a couple days ago (the driveside XT arm was finally beginning to crack). If I were going for a loaded tour, I'd certainly want the 11-34 in back as well. Keep in mind that you could also slap a 38- or 39-tooth middle ring on there to even things out a bit, too.

2manybikes

In case it comes up the 9 speed Dura Ace triple is different than Ultegra and 105 it has a 90 mm bolt circle. This is because the small ring bolts to the middle ring. The only way to go smaller is to go to an Ultegra or other crank.

grolby

What is the deal with manufacturers spec'ing full-size road cranksets on touring bikes? It's enough to make me want to pull my hair out. Anyway, you can go down to a 24T chainring. Most importantly, there is no need to buy a new front derailer! A big jump from the little to the middle ring is generally not a problem for triple FD's. It's definitely not as smooth or fast, but it can manage it. No, where triple fronts usually choke is trying to jump too big a gap between the middle and large rings. This is part of the reason why a lot of old touring bikes had a big and middle chainring with only a 6-tooth difference, with a big drop to the granny. Back when I had 28-44-50 crankset, the derailer handled the 16-tooth difference between the granny and middle rings like a champ, even cranking up a hill. It wasn't fast, but it worked. Now that same derailer is shifting a 28-36-48 crankset. It completely chokes on the 12 teeth between the middle and big ring if I try to upshift under any kind of load. I'm sure it would happily shift from a 24 to the 36 all day though, so maybe that'll be my next change.

grolby

The (mind-blowingly stupid) DA triple crank is not an issue here, since the cranks in question are 105.

acorn_user

Give spa cycles a ring on 01423 887003 (Harrogate)
They are excellent. You might also try sjs cycles in Bridgewater a try. Small rings made by stronglight or ta should be around. Spa may well recommend the stronglight impact triple in 46/36/26 or 48/38/28. With a 12 or 11 cog at the back, 48 or 46t rings will give you a lot of speed. One of my friends managed over 50 down Hartside on his Galaxy with a similar set-up.
The new Deore 530 rear mech will cope with 45t chain wrapping. I have an older LX on my Dawes, and it copes very well with my 52/42/30 11/34 set-up. However, I wish that I had bought the Impact instead of the sora. They cost about the same, but the impact is half the weight and much more nicely finished.
Also, 30t/34 is a very long gear. You might well be able to get up things in that. Before you splash out, why not ride up a big bad hill with bricks in the panniers?
tara!
Dave