djohannsen

First, I've searched the forum and found some answers, but not everything that I would like to know. Since I really want to understand if there will be any issues that I haven't forseen, I will ask something that may be a bit tedious to those here and offer my apologies in advance.

So, in 2003 I bought a bike that was set-up with Shimano 105 triple (it was my first serious bike and I thought "more gears must be better"). I'm now a reasonably strong rider (about 310 watts at threshold), so I never use the small chainring. Thus, I want to change to a double.

I hope that I can get away with buying an Ultegra double crankset (I assume 6500 SS, since my old 105 is 9-speed) and an Ultegra 6500 SS front derailleur, and then adjust the settings on my front shifter. Do I have this right? From reading through past postings, I am a bit worried about spindle length in the bottom bracket. I don't have deep pockets, so I don't want to undertake the conversion if it's going to be some sort of slippery slope of having to buy more and more components to make things work. I will, of course, have my LBS do the work, I just hope to have a good grasp on the hardware required to make the switch.

I apologize for being such an idiot aobut the basic mechanicals of my bike. I hope that someone can let me know if I have it right about what components will be necessary to make the switch. Thank you for any help.



Dave

Garthr

You don't need a new crankset, just take off the small ring of the 105 and get a shorter BB. But, Octalink is going bye bye quickly. The BB's are overpriced,under engineered, and you have only one choice of vendor, Shimano.

In all honesty I'd try to get rid of the crank and get a design that has been around awhile, like a tapered design. The BB's last longer, and will be available forever. Double cranks are available by the bucketload on ebay. I saw this one for instance for $50 and free shipping. https://cgi.ebay.com/Shimano-Ultegra-...A1%7C294%3A100

Buying a new Octalink BB and taking off the small ring is your cheapest option in the short run. Getting a square taper crank and BB may cost a little more now, but will save you in the long run with longer lasting, and less expensive BB's. That's my biased opinion about it.

djohannsen

This is essentially what my bike shop recommended a couple of months ago. To go this route, I would also want to buy a 39 tooth chainring as well (I don't know that I'm quite man enough to have nothing lower than a 42/23 - that 39 up front would be nice if I were riding somewhere other than around my area). This would wipe out some of the cost savings as lightly used Ultegra double cranksets are a dime a dozen at eBay, but it seems like chainrings seldom turn up at anything than full MSRP. If I have to buy a bottom bracket either way that I go, then the cost may be more or less a wash.


Thanks for helping me out. I've been riding off and on since the late '80s (and very passionately the last several years), but I just don't know anything about equipment. I had never considered anything other than Shimano cranksets, so I didn't know that I had other options (the whole issue of compatability is more than a bit bewildering to an idiot like me). I really don't want to take the time of people at my LBS if I am not planning to buy the components from them (and a new crankset from any maker is a damn expensive piece of gear), so that's why I'm appealing for help here. Maybe I will get a copy of the Park tools "Blue Book" and see if it helps me make more sense of all this.

Again, thank you.


Dave

bikebloggers.co

I completed this same kind of transformation on my trek madone 5.0. I went from triple ultegra to double ultegra.

Change the right shifter for a double. Change the crankset for a double. I kept the same bb. Change the FD for a small one. The last thing is I could've keep my long rear-derailleur, but for the fun of it, I changed it for a small rear-derailleur. I bought used parts on ebay, except for the new cables.

Now I'm really happy with the new setting a plus I've learned more about bike mechanics, since I've done all the modifications.

bikebloggers.co

oups !!! I meant left shifter

hernick

There's one other option for making the best use of your triple crankset while reducing the weight of your bike and improving shifting performance.

You can switch to a narrower cassette like an 11-19 or a 11-21. That gives you nothing but single-tooth jumps with the 11-19, and just a missing 18 and 20 on the 11-21.

Nothing to buy other than a cassette and a new chain.

Double are overrated. Very-close-ratio cassettes with triples are great.

djohannsen

Thanks for letting me know that it can be done. From what I read seatching the history here, it seems like 105 uses the same left shifter for both double and triple (Ultegra and DA have different shifters). So, it sounds like my original opinion about what I would need to do might not have been too far off the mark.

Doing a bit of Googling, it seems like the shorter spindle length on the BB made for doubles claims to position the chain optimally (i.e., bottom brackets can be bought with one of two spindle lengths). Since you are happy with the shifting performance of your set-up, swapping the BB seems like something that could be done down the road.

I really do hate that I am so intimidated about the maintenance. I am starting to at least figure out what the basic parts are, so maybe I'll gradually upgrade the components on my bike and do some of the work myself. Again, thanks for helping out.


Dave

djohannsen

Would this make more of the cassette usable on a given chain ring? I hate with the triple that cross gears (ie, 52/23'ish or 30/11'ish) are unusable, necessitating a shift to a different chainring (with the resulting loss of momemtum as I soft pedal for a revolution or two). One other reason to change is that the outer chainring on the triple is only a 52. I really wish that it were a 53 or 54 for a bit more punch on longer descents.


Dave

Garthr

I like the idea of using the 11-21 or 11-23 for you Dave. You never want to use the 30/smallest cog or 52/largest cog anyways, it really stretches the chain. Use this gear chart and you can see how it works for you. Put in any rings you want . https://home.earthlink.net/~mike.sherman/shift.html

From a 52 to a 54 is only 5 gear inches Dave, it doesn't seem worth the expense to me, and barely noticeable. You could learn to pedal faster and smoother instead. If you need a 39t ring or whatever, remember you do not need to buy a Shimano ring, Vuelta is just one brand that's good and about $25.

Shifting is a part of life on the bike. I know crossovers are not great, but unless you go to a half-step plus granny type gearing, lots of cross overs are inevitable.

djohannsen

I'm on an 11-23 now. I didn't know (until now) that Shimano made an 11-21. Since I've got the option of the really small ring with a triple (i.e., the 30), this might be a nice route to go. As for the crossed gearings, It's really the two or three crossed gears that cause the chain to rub on the front derailleur (not just the smallest and largest cogs). I thought that with a double that this problem would be mitigated allowing me a wider range of shifts without having to jump between chain rings. To be honest, I'm sure that part of my desire to get off the triple is the fact that I've got my first race coming up in a couple of weeks. There's certainly a bit vanity and insecurity on my part in not wanting to be the only dude in the field on a triple.

Thank you also for the pointer to the calculator; it allowed me to see for myself that you're absolutely right that the change from a 52 to a 54 doesn't amount to much of a difference at the top end. I was hoping that adding a couple of more teeth on the big chainring would make more of a difference.

Finally, thank you for all the time that you've generously taken to help me. It sounds like maybe I should scrap the plan of changing to a double. Instead, I can move to an 11-21 the next time I do a chain and cassette replacment (I've got a lot of miles on my current ones, so this will be pretty soon). I can then start squirrelling away money for the probably not too distant grouppo purchase (since my 105 components are now approaching seven years of service).


Dave