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Crankset swap out/bottom bracket issue

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Crankset swap out/bottom bracket issue

Old 01-07-08, 11:26 PM
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hodadmike
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Crankset swap out/bottom bracket issue

To get some hill gearing I'm changing my stock Truvative 50-40-30 crank to a Sugino XD300 46-36-26. My chainline was 46mm on the old BB, and because of the offset in the new crank spider casting, chain line with the new crank is 51mm.
When I removed the stock bottom bracket, I found it was backward from every other one I've seen: fixed on the left and adjustable on the right with standard threading.


Spindle length is 116mm, so if my chainline has grown 5mm, I should be looking for a new 111mm bottom bracket? I see Shimano has sq. taper BBs in 110mm and 113mm, so go with the 110mm?
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Old 01-08-08, 01:29 PM
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http://www.sheldonbrown.com/chainline.html

Are you using a 130mm road rear hub? Are you sure the spindle isn't 118mm or 115mm instead of 116mm? Are you measuring with a ruler or calipers? Sugino XD300 crank should provide the proper road chainline with a 113mm BB spindle so 51mm sounds way high. Swapping a crank intended for a 113mm spindle onto a 116mm spindle should only change the chainline by 1.5mm and not by 5.0mm.
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Old 01-11-08, 08:52 AM
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The spindle length was 116mm, the left side cup was fixed to the BB and the right side cup had a taper on the inside like a normal left side.



Next problem: spacing between old chainrings and new. The old set was about 7mm center to center, the new Sugino has about 5mm c to c on the 46t and 36t, then 10mm c to c between the 36 and the 26. This will work for my bar end shifters, but my other Sora (no trim) shifters won't work. Options? I thought about changing the gap with shim washers to balance things out. I'd need to find some 10mm washers with a small O.D. so as not to interfere with shifting.




Last edited by hodadmike; 01-11-08 at 10:12 AM.
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Old 01-11-08, 08:53 AM
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Sorry, goofed the pics. Will fix this afternoon after work.
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Old 01-11-08, 08:58 AM
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It's a bit late to suggest this but you could have saved much time and money by just changing the 30T granny ring on you original Truvativ crank for a 26T ring. I've done this on a bunch of Shimano 52/42/30 road cranks and it works just fine.
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Old 01-11-08, 09:18 AM
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Originally Posted by HillRider View Post
It's a bit late to suggest this but you could have saved much time and money by just changing the 30T granny ring on you original Truvativ crank for a 26T ring. I've done this on a bunch of Shimano 52/42/30 road cranks and it works just fine.

Sorry to hijack but it still on the same subject.... What FD are you using to go 52/42/26 all of them I can find are only good for 1 20 tooth difference so I thought I was stuck on my 52/42/32 setup, the 26 would be great for the hills in my area..

Chief
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Old 01-11-08, 09:57 AM
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I went through the same thing, and wrote Sugino. To their credit, they wrote back pretty quickly, and in english to boot.

The XD300 and 600 are designed for either a 113 or a 118 bb.

A 113mm bb will get you a chainline of 47.5

A 118mm bb will get you a chainline of 50.
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Old 01-11-08, 07:24 PM
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Originally Posted by cachehiker View Post
http://www.sheldonbrown.com/chainline.html

Are you using a 130mm road rear hub? Are you sure the spindle isn't 118mm or 115mm instead of 116mm? Are you measuring with a ruler or calipers? Sugino XD300 crank should provide the proper road chainline with a 113mm BB spindle so 51mm sounds way high. Swapping a crank intended for a 113mm spindle onto a 116mm spindle should only change the chainline by 1.5mm and not by 5.0mm.
I took Sheldon Brown's advice and went with the 113mm, and it worked out fine.

It's a bit late to suggest this but you could have saved much time and money by just changing the 30T granny ring on you original Truvativ crank for a 26T ring. I've done this on a bunch of Shimano 52/42/30 road cranks and it works just fine.
True, but after searching the archived threads on the subject, the consensus was a 16 tooth difference between the middle and granny (I'm going with a 24t on the wife's bike) would be too great. The shifting capacity of the FD, the extra chain take-up at the RD, and overshifting down past the granny and onto the BB had me thinking of just scaling everything down about 4 notches.

I also wanted to try 170mm crankarms instead of the 175mm on the wife's bike.

Last edited by hodadmike; 01-11-08 at 11:21 PM.
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Old 01-11-08, 08:30 PM
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Originally Posted by Navy_Chief View Post
Sorry to hijack but it still on the same subject.... What FD are you using to go 52/42/26 all of them I can find are only good for 1 20 tooth difference so I thought I was stuck on my 52/42/32 setup, the 26 would be great for the hills in my area..

Chief
I keep the same Shimano triple front derailleur that came with the bike or the build kit. I've used 8-speed 105 triples, 8-speed RX100 triples, 105 9-speed triples and Ultegra 9-speed triple fd's with good results. The shifts from the 42 to 26 and 26 to the 42 aren't super fast but they are plenty good enough even under moderate loads.

Shimano's "tooth ratings" are both conservative and assume you insist on perfect shifting for each shift. If you will compromise slightly, the regular triples work fine.
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Old 01-12-08, 11:22 AM
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I'm coming late to this thread, in response to an email from the O.P.

I too would have initially recommended keeping the original cranks and just swapping out the silly 30 tooth ring for something more useful, such as a 26.

I have a canned section on this popular upgrade at: http://harriscyclery.com/74

However, I see a later post that this also involved going from 175 to 170 mm cranks, and that it's for a woman, so that probably makes a lot of sense...175 is too long for most men and for almost all women. See: http://sheldonbrown.com/cranks

I think the shifting problem is mainly due to the mismatch between the 46 tooth big ring and a front derailer optimized for a 52 big ring. I address this issue in detail at: http://sheldonbrown.com/front-derailers

The XD300 is the bottom of the line for the XD series. The XD cranks are all the same, but the 300 has the cheapest chainrings. I was going to suggest moving the larger two chainrings over from the Truvativ crank, but maybe it's 130 mm BCD, vs the 110 of the Sugino.

For the 46-36-26 setup, my advice would be to go with one of the new IRD front derailers made for this. This is the ONLY currently available front derailer compatible with BOTH a 46-big-ring triple AND "road" STI front shifter.

Sheldon "Isn't Indexed Front Shifting Fun!" Brown

P.S. There was some confusing misuse of the terms "fixed cup" and "adjustable cup" in this thread. The "fixed cup" is the one that has a shoulder that butts up against the right-hand (right-foot?) edge of the BB shell. It does not refer to how the threaded part connects to the bottom bracket unit.

The term "adjustable cup" is actually a bit of an atavism, since cartridge bottom brackets aren't adjustable. For that matter, they don't even have "cups" per se! ;-)

Last edited by Sheldon Brown; 01-12-08 at 11:25 AM. Reason: L'espirt d'escalier
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Old 01-13-08, 12:54 AM
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Sheldon "Isn't Indexed Front Shifting Fun!" Brown
Indeed!

Thanks to all for your help.

I just finished putting a 26t granny on my Truvative road triple and the front gear changing is just fine. Picks it right up and sets it back down with my bar end friction shifter.

My wife's bike however, may need some more tweaking. I put a 1.5mm shim (made out of a stainless washer) between the middle ring and the spider mounting tabs and was able to get even spacing (7mm C to C) between the chain rings. The Sora brifter is now able to put the chain on all the rings, but a little trimming would help. I could change to a Tiagra (or another trimable STI brifter), but she's sold on those little thumb buttons/mouse ears. So what about using a ratcheting Campy?
Or...
I saw pictures online last summer of the new 9 speed Sora group, it looked sweet and I believe had trim too. Any one heard of a release date yet?
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Old 01-13-08, 04:09 AM
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Originally Posted by hodadmike View Post
I saw pictures online last summer of the new 9 speed Sora group, it looked sweet and I believe had trim too. Any one heard of a release date yet?
That sounds like the Ultimate recreational cyclist group. Being a Campy guy, I love those thumb shifters.

Tim
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Old 01-13-08, 12:53 PM
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Originally Posted by cs1 View Post
That sounds like the Ultimate recreational cyclist group. Being a Campy guy, I love those thumb shifters.

Tim
Agreed!
Sounds like a topic for a new thread.
I'm pretty much done with this one.

Thanks
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Old 01-13-08, 08:26 PM
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Too bad Shimano does not address the market with a dedicated road bike solution for a good Tour/comfort/loaded/older spinner/big hill sitdown rider/ triple-gearing option for those of us that would like the option of low gears, with a wide range of relatively evenly spaced gears. I for one would be perfectly willing to give up the option of 54x11 gearing, although with just a little double shifing, I easily had it all in the friction-shifting era of a 5-spd cog/Avocet triple

The ubiquitous 5X-to-30T triples are not condusive to low gearing: for example, a 30T chainring with a 32 rear cog (not even available on a 10-spd freewheel) is not an ideal tour solution (and, for older riders that may be a little overweight, every ride is like touring). The mfg needs to provide a solution that the rider can select--it's not possible to leave it to the imagination of mechanics at usual bike shop; the current crop of bike mechanics just do not have the knowledge to give riders what they want.

For marketing purposes, the drivetrain probably should not be called the Earl Grey; I'd call it the Pacific Coast. I'd say, an inner ring of about 24 and a 10-spd cog set from 12-27 with a top ring of about 46-48T, and an inner ring that depends on if the rider wants to do a lot of double shifting for the maximum amount of gears.


Last edited by wagathon; 01-13-08 at 08:54 PM.
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