Hesso

I'm going from a Giant 26" MTB - 9-sp /11-34 cassette & 22/32/42 triple chainrings, that I've been using as a hybrid in the Rockies (primarily paved trails - lots of hills) to a >>

Specialized Sequoia - Rear: 9-sp / 11-28t cassette / Shimano 105. Front: 30/39/50 / Tiagra Triple derailleur / Tiagra crank - 5 bolt 130 BCD.

In just a few rides on the Specialized I've notice I'll not even come close to utilizing the full range of gears, especially that big honkin' 50t outer chainring. I want to bring the gear ratios somewhat more inline with the Giant's (understanding that the final ratios are different on a 26" wheel compared to the 700c), but lower will be better in my case.

The rear looks easy enough to modify with new cassette and probably a derailleur (to handle something like a 32t cog - or maybe only the chainring mod will be necessary) but I'm stuck on the front aspect and what would need to happen to get closer to the Giant's setup. Question: Is it going to be impossible to simply buy the smaller middle and outer rings for the 5 bolt crank - or maybe just replace the 50t outer ring? Even the 39t center ring is a little tall for my riding ability (60+ age group at 7,000 ft.). Is the that 5 bolt crank the issue in finding smaller chainrings to work on this project?

Welcome any suggestions or if there's another thread already covering this in detail.

Soody

Yeah so get a wider cassette, say, 9spd 11-34 or 12-36 and 9spd mtb derailer (easy enough, the pull ratio between 9spd road and 9spd mtb is the same).
You could also possibly get a smaller granny (small chainring), 28, or 26. That might work well.

As for having too many tall gears, who cares? Just don't use them.
You can't go smaller than 39 (well 38) in the middle. You could go smaller than 50 but like, why. You could get a different crank entirely, again, why.

Soody

a small note on 9spd mtb derailers. Basically all of them will suit your purpose. The newer style ones with 'shadow' are quite good. However, you probably want to avoid derailers that do not have a barrell adjuster. Many of them now do not. You likely do not have a barrell adjuster anywhere else, like the mtbs they're designed for have. So you can add one later but it's very annoying.

Hesso

Thanks for the heads up on the barrel adjuster. I hadn't noticed that in searching for the RD. This Specialized does have a built in barrel adjuster (cable housing stop) welded on the frame just behind the steering tube, so that may be helpful if I end up with the derailleur that doesn't have one.

Soody

Yeah you're all good then. It's still preferable imo to have one at the derailer, but not a big deal.

Hesso

Agreed Soody. Thanks!

breadfreak

The gearing on your mountain bike sounds great. In your position, I would first replace the cassette with a 12-36 and see how it feels. If you find yourself still wishing for lower gears, I'd swap the 30 inner ring for a 24 (I think the smallest available for a 74mm BCD) and either swap the 50 outer for a 44 or 46 or just remove it. The possible limitations here is the rear derailer's max sprocket, its capacity to take up the extra chain when using the 24 inner ring, and the total length of chain available if you wind up trying to shift into 50f/36r. What model derailer have you got?

Hesso

The rear derailleur is a Shimano 105 and my recollection (maybe from Shimano's website) is that it won't handle the larger MTB cogs. But it's appears to be fairly simple to buy other derailleurs that will work (for MTB's).

I'm leaning towards what you're saying, just the cassette and rear derailleur (and chain), and see how it feels. I'm betting it's still going to be pretty tall gears. I compared the teeth from my Shimano 11-28 cassette to a Shimano 11-32 cassette. There's a 4 tooth difference between the top larger cogs, then a 2 tooth difference between the middle cogs, and the exact same number of teeth on the last couple of smaller cogs. So I would only get benefit from the middle upwards. It's something, but maybe not allowing the use of the whole range.

Bill Kapaun

What's the most useful smallest cog size? 12, 13, 14T? Assuming 8th gear is a 13T, do you ever use it enough to justify it?
Combine TWO 9 speed cassettes.
One with a smallest cog that's actually useful for you such as a 13-?? or 14-?? and a ??-32/4.
You'll have the ability to set the increase between cogs to your taste. Maybe you want rather wide gaps between your 2-3 largest cogs and then smaller between the rest?
Some of the old 7 speed14-34T FW's had a 10T gap between 1 & 2.

breadfreak

I would say going to an 11-32 from 11-28 will be disappointing, it's not much of a jump.

And I might need to revise my initial advice... I think your derailer is likely an RD-5501-GS. These are rated by Shimano (always conservatively) to be good up to a 28 rear sprocket, and I'd be surprised if it works well with a 36. You will need something like an RD-M591-SGS, so you're looking at about €60 for the cassette + derailer. Conversely, a 24 inner ring can be had for €10 or less and a smaller outer ring shouldn't cost you more than €20 either. Strictly speaking, if you wish to lower the entire range of the system the crankset is the right place to do it anyway.

For what it's worth, my bike is set up 10-speed 11-36 rear and 40/24 front; similarly I built my girlfriend's bike 9-speed 12-36 rear and 39/24 front. It's a good combination for hilly country, I can cruise in the larger chainring 90% of the time but I still have grandpa gears when I need them, and I've never wished I had a taller gear. You're lucky to have a 9-speed system as 'mountain' and 'road' components are compatible, and to have a triple crankset with a simple 5-bolt pattern. It would get expensive if you had to replace shifters, crankset and possibly bottom bracket and front derailer too just to get the gears you need... a position many with newer 2x and 1x road bikes wanting lower gears find themselves in.

Hesso

Man, the price of Shimano components has skyrocketed since Covid. Availability too, stuff is hard to find right now in the US. My derailleur is the Shimano 105, is that the same as the RD-5501?

The RD=M591 is the exact derailleur I've been eyeing. The mid-level cassettes are getting hard to find but I can wait. I think the 32t lowest cog 'could' work for my ability, but I agree that the 11-32 isn't a big reduction over the 11-28. And I was initially thinking about how to change that big 50t outer ring but honestly, I haven't been able to get out of the 39t center chainring.

Isn't the final drive ratio effected by wheel diameter too? An older 26" MTB in the same gear ratio as the 700c roadbike, the MTB would be a lower effective ratio yes? So to come close to the MTB ratios, maybe I'm going to need an even lower drivetrain on the roadbike?

Hesso

I realize that many people say just bail on the large chainring etc., but aging legs in high altitude mountains. . . having a few more gear ratios makes it a bit easier to navigate the terrain.

alcjphil

Your road triple crank has a 130mm BCD for the middle and large rings. Smallest size you can fit for the middle ring is 38 teeth, not much different than the 39 tooth ring you have now. Additionally, it is hard to find big rings smaller than 50 teeth, not many manufacturers make anything other than 50, 52, and 53 teeth big rings. The rings on your crank are matched to facilitate shifting, using rings other than the ones that were made for that crank may result in poor shifts. Your front derailleur was also designed for the gaps between the rings on your current crank. How much have you ridden the bike so far? Have you done many hills with the current setup?
In a perfect world, component manufacturers would produce cassettes with a lot more combinations , but in this world, 9 speed cassettes are becoming more and more rare. Cassettes with 32, 34, or 36 teeth all seem to have 11 tooth small cogs, not so great if you don't need a gear that high. Cassettes are designed with shift gates that improve shifting. It might be possible to combine cassettes so that you have a 13 or 14 tooth small cog, but that would also put the shift gates in the wrong place for some shifts. If you need a lower lowest gear you should be able to get that with an 11-32 or 11-34 cassette and a mountain bike 9 speed derailleur but you will end up with high gears that you won't use much

Hesso

Thanks alcjphil, I think I'm getting my arms around where I'm at with this bike. And maybe at least modifying the rear only for now and see how I like the overall feel for the bike itself after the mod, is the way to go. I'd be willing to replace the crank at some point (along with derailleur etc.) and I suppose the bottom bracket may come with that?

Given that my MTB's 39t center chainring is only 3 teeth away from the 42t roadbike outer ring, it's like riding in the MTB's largest chainring most of the time, which I rarely do in this environment.

Appreciate all the pointers from this group to 're-calibrate' my mind on where I'm at on this.

Thanks!

Bill Kapaun

Of course. However, you tend to have heavier tires/wheels/bike which negates "some" of the benefit.

My hybrid came with 28-38-48 which causes a similar problem for me. (I did build a set of "road" wheels w/25mm tires for it)
I switched to a 22-32-44. I then switched the 44 to a 38. (I'm old & have medical issues) I ride mostly on level terrain and seldom use the 22. However, there's been a few times when I ran into a severe headwind and had to use it. It was beautiful because I still had closely spaced gears and could pick one that worked near perfectly. I typically run a 12-23T for summer & a 13-25T for colder weather.
The problem that you have is that you have a "road" bike and "mountain" FDER's use a slightly different cable pull than "road". So a simple swap to a mountain crank isn't so simple.
I honestly don't know how much of a effect it'll have mismatching things. I simply don't do road since back issues keep me from using the drops anyway.
maybe somebody that's put a mountain crank on a road bike can chip in?

Hesso

Yes, the "closely spaced gears" is what I've come to appreciate on the triple chainrings. Rather than rifling through the rear cogs to find the right gear, I almost always leave the rear in 4, 5 & 6 and then simply move between my middle and outer chainrings and then the granny gear when necessary. Probably an 80/20 rule in there somewhere.

I've already swapped out the drop bars and replaced them with a slight riser flat bar and Shimano MTB shifters, which work fantastic. So the bike is fitting my riding style very well.

alcjphil

I have a mountain bike crank on my touring bike. However, to match the chainrings I had to use a mountain bike front derailleur which of course will not work with road shifters. In my case it was possible because I am using bar end shifters and the front shifter is friction, not indexed. This is a very common setup on touring bikes

breadfreak

Yes, but the 74mm BCD of the Tiagra crankset will only accept a ring as small as 24 teeth, and I suppose if you are riding a road bike you do intend to ride at least a little bit faster than on the mountain bike?

Bill Kapaun

So just get a 22-32-4x and a "mountain" FDER. A 42/4-11 is still pretty high for most of us.
My 22-32-44 is just a cheap FSA I got on ebay for about $35. It had bolted (not riveted) rings. I'm more into "serviceable" for the lowest price instead of "curb appeal".
It was the only thing I could find with 165mm arms for my bad knees. 170mm and I have somewhat chronic knee pain.

djb

I get the reasons you want to change, and a different crankset is probably the best thing to do, but can you move the fd down? Plus you're starting to get into domino effect territory, ie more changes, so hopefully you get proper advice.

cyccommute 

You rang? Both of these are using mountain bike cranks with road front derailers and STI shifters. It all works perfectly...including the 20 tooth inner on the Cannondale.

XT external bearing bottom bracket modified to run a 20 tooth inner ring.


46/34/20 with an 11-36 9 speed cassette. You can see the STI shifters which have about 10,000 miles and nearly 20 years on them.



A 48/36/22 with road front derailer and an 11-34 9 speed cassette with STI shifters.



One thing to make it work is to not use Shimano’s expensive front derailers. Both of these are Tiagra or below. The Salsa has a Microshift on it. Shimano’s expensive derailers are difficult to work with. Their cheaper versions are much more forgiving.

Hesso

Sorry for the delay, newbies only get to post 5 times in a 24 hr period. Lots of good ideas here. DJB's remark about having enough room to move the FD downward is well taken. The rear most part of the FD cage is only about 5/8" (18mm) above the chainstay. Doing the math to calculate the difference in a smaller outer chainring (going from a 50t to say a 42t) I have some concern that lowering the FD for the new chainring will bring it very close to that chainstay and it could be that the cage will come in contact with the chainstay.

I already put Shimano Sora flatbar road shifters on the Specialized (converted it to a flatbar), and I noticed that they will probably not be able to move the FD out far enough for the mountain bike crankset (backed out the limit screw and the Sora's won't move the derailleur out any further). Just comparing the chainline distance to my Giant mountain bike, it appears the chainrings on mountain bikes are perhaps an 1/8" (3mm) further out than roadbikes, so that would necessitate MTB shifters, which I'm okay with.

I think what I gather from the comments is that this is all possible, what I'm finding right now is that in the US, actually finding the parts in stock is difficult (worldwide shortages and some price gouging going on). Rows and rows of "Notify When In Stock," messages in all the major vendor websites. Also, the 3x9 makes the only mid-level groupsets available such as the Shimano Alivio range, which is probably okay, just reduces my options.

So thanks for the comments and suggestions. I still like the idea of a wide range of gear options in the 3x9 setup (maybe I should switch to 3x10 - many more shifters out there). I'm in a holding pattern until stock comes available. I'll keep riding it though and see if I'm simply balking at what 'feels' different.

HillRider

Shimano's most recent but discontinued 10-speed FC-5703 105 triple crank was the last one to have a separate 74mm BCD for the granny chainring and that gives you the ability to replace the 30T with as small as a 24T which will make a big difference. A 24x28 combination is a 23 gear-inch low gear which is usually low enough for all but loaded touring. I have FC-5703 cranks on two bikes and have replaced their granny chainrings with 26T rings. Shifting remains good and the lower gears are very appreciated.

More recent Tiagra triples (FC-4603 and later) have the 30T granny chainring bolted to the middle 39T chainring with a 92mm BCD and 30T is the smallest that will fit. 105 and above triples vanished with the move to 11-speed groups.

cyccommute 

I assure you that the cranks on my both my bikes are mountain bike cranks and I’m using road front derailers. I’ve even used internal bearing cranks on the touring bike in the past

IMG_1444 (1) by Stuart Black, on Flickr

If the chain line doesn’t work, move it! With external bottom brackets, you just move the spacers from one side to the other. You can get various thickness of spacers to fine tune the position of the crank. For 3 piece cranks, you need a different width bottom bracket. It’s more of a guessing game but just remember that 3mm is about 1/8”. If the crank used a 113mm bottom bracket on a mountain bike, a 108mm bottom bracket should work on a road bike.

The crank makes less difference when it comes to “speed”. A 9 speed crank will work just fine with a 10 speed cassette. I’m running a Race Face Turbine with a 94/58mm BCD which is from the 8 speed days on a mountain bike with a 10 speed cassette and 10 speed chain. I have zero issues with it.

I agree with you that an Alivio triple isn’t a good choice. It uses riveted chainrings which makes changing rings impossible. But Fleabay has lots and lots of good quality used units. You can also find some knockoff triples on Fleabay. IXF cranks are cheap and durable. Finish is a little rough but they are cheap.

alcjphil

The flat bar conversion means that you could have used mountain bike shifters which would have worked perfectly with a mountain bike front derailleur and crank. a 9 speed mountain bike shifter would have worked with your current rear derailleur and you could have kept your current cassette. I have a mountain bike crank(Raceface Turbo) on my touring bike with a 12-28 8 speed cassette and that gives me low enough gearing for any hill. I think that many of the suggestions that were offered were based on the assumption that your bike had drop bars. The flat bars you have now open up several other options