Bike Forums - First fixie build

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- - First fixie build (https://www.bikeforums.net/singlespeed-fixed-gear/1156290-first-fixie-build.html)

j_e_r_e_m_y

10-11-18 07:08 AM

Quote:

Originally Posted by vailskier3 (Post 20610200)

gotcha, it didn't even occur to me that the crankset would matter with the BB. Is it safe to go a couple milimeters wider?

Well, every mm you deviate from that recommendation will theoretically move your chainline farther from being perfectly straight. That said, a deviation of 2-3mm probably wouldn't be that big a of a deal.

vailskier3

10-13-18 05:46 AM

Ok, so I just measured my bottom bracket shell and it looks like its 70mm. That means it is italian thread, correct?

seamuis

10-14-18 09:00 AM

Quote:

Originally Posted by vailskier3 (Post 20614167)

Ok, so I just measured my bottom bracket shell and it looks like its 70mm. That means it is italian thread, correct?

typically yes, if the shell is 70mm it’s ITL threaded.

JohnDThompson

10-14-18 04:24 PM

Quote:

Originally Posted by vailskier3 (Post 20614167)

Ok, so I just measured my bottom bracket shell and it looks like its 70mm. That means it is italian thread, correct?

Not necessarily. Shell width is only loosely correlated with thread spec. While many Italian road bikes have 70mm wide shells and Italian thread, some Japanese road bikes from the 70s and early 80s have 70mm wide shells and English thread. And some Italian track bikes from the 60s and 70s have 65mm wide shells and Italian thread. And some frames start out with 68mm shells and English thread, then get cross-theaded and stripped so an English thread bottom bracket is not secure, so the frame gets reamed and re-tapped to Italian thread.

The only way to be sure what thread your bottom bracket shell uses is to check it directly. If it's Italian thread, a known English thread cup will fall into the shell without engaging any threads.

vailskier3

10-15-18 05:20 AM

Thanks for the info guys. I ordered an italian thread BB, so I guess we will see if it works!

vailskier3

10-16-18 09:49 AM

Quote:

Originally Posted by j_e_r_e_m_y (Post 20610935)

also, couldn't you just add spacers to the hub to correct the chainline? So my thought was it would be better to go a few mm wider and just add spacers if needed...

j_e_r_e_m_y

10-16-18 09:51 AM

Quote:

Originally Posted by vailskier3 (Post 20619012)

also, couldn't you just add spacers to the hub to correct the chainline? So my thought was it would be better to go a few mm wider and just add spacers if needed...

No, because spacers sit outside of where the cog or freewheel threads on. You'd essentially make the axle wider, necessitating wider dropouts, without changing the position of the cog/freewheel or the overall chain line.

vailskier3

01-07-19 12:19 PM

Is that true? You can only add spacers after the cog? Is there no way to move the cog out? Am I better off buying wheels and having a shop dish them to correct the chainline?

seamuis

01-07-19 07:57 PM

Quote:

Originally Posted by vailskier3 (Post 20736470)

Is that true? You can only add spacers after the cog? Is there no way to move the cog out? Am I better off buying wheels and having a shop dish them to correct the chainline?

i think there might be a misunderstanding here. Yes you can move a sprocket out (toward the drive side) by putting spacers to the inside of the sprocket, to adjust your rear chainline outward. Spacing the sprocket is different from dishing a wheel, which involves moving the axle alignment and adjusting the spoke tensions (and possibly needing to modify the spoke lengths on one side of the wheel, which can necessitate replacing spokes). If you want to adjust axle alignment on a multispeed wheel, the wheel will then require redishing. If you simply want your sprocket further outboard, all you need is spacers. Of course, you only have a very limited amount of threading to utilise for spacers, so the amount of outboard adjustment you can achieve is rather limited.

if you buy a new set of wheels that are ‘track’ wheels, they will already have a centered axle and will require no dishing. If you can’t achieve a good chainline by moving the sprocket outboard a few multimeters, then you need to move your chainring or entire crankset inboard.

vailskier3

03-25-19 12:22 PM

thanks for clarifying. sorry it took so long for me to get back on here. been busy working on the old house. starting to look at wheelsets now. i think i'll be good to just get a track wheelset and space the cog out a bit.

ThermionicScott

03-25-19 01:25 PM

Quote:

Originally Posted by vailskier3 (Post 20854287)

Umm, you're not going to be able to space out the cog very much on a track wheelset. Why are you committed to using a crank and bottom bracket that give you the wrong chainline?

vailskier3

03-25-19 01:27 PM

i'm not, just never done this before and i'm having a hard time understanding the mechanisms involved. i guess i need more learning.

ThermionicScott

03-25-19 01:32 PM

Quote:

Originally Posted by vailskier3 (Post 20854388)

i'm not, just never done this before and i'm having a hard time understanding the mechanisms involved. i guess i need more learning.

Did you find out whether your bottom bracket shell is Italian or English yet?

vailskier3

03-25-19 01:35 PM

Yes, it was italian. I got a Shimano Bottom Bracket BB-UN55, Square Taper 70x110mm and paired it with a ofmega crank and 46T chainring.

ThermionicScott

03-25-19 02:01 PM

Quote:

Originally Posted by vailskier3 (Post 20854400)

Yes, it was italian. I got a Shimano Bottom Bracket BB-UN55, Square Taper 70x110mm and paired it with a ofmega crank and 46T chainring.

Progress. What does your chainline measure with that? :)

79pmooney

03-25-19 02:43 PM

Quote:

Originally Posted by vailskier3 (Post 20854287)

Don't space out the cog with a washer/spacer. It will cost you thread engagement for the cog and probably the lockring. Stripped threads will cost you the hub and the wheel build and won't get you home. If you have get that cog out, do it by moving a washer in the nut/cone assembly from the right side to the left side, then re-dish the wheel. This will work just fine. Only drawback is that you now have a bastard wheel unlike any other wheel out there.

For my Peter Mooney fix gear project, I built up a wheel around a double sided track hub, spacing it from 120 to 126 with 4mm of dish. Had made for me a double cog "dingle" that I screwed onto the dished in side. Made up a triple crankset. Now I had a wheel with 3 cogs, each one lining up with one specific chainring, giving me three very different gears with the rear wheel moving in the dropout very little. This wheel rides rock solidly in all three gears. Yes, a true bastard, but a very happy one.

Ben

vailskier3

03-26-19 05:58 AM

Quote:

Originally Posted by ThermionicScott (Post 20854441)

Progress. What does your chainline measure with that? :)

pardon my ignorance...how do i measure chainline? is that the distance from the frame to the chainring in mm?

ThermionicScott

03-26-19 07:50 AM

Quote:

Originally Posted by vailskier3 (Post 20855401)

pardon my ignorance...how do i measure chainline? is that the distance from the frame to the chainring in mm?

Close! The distance from the centerline of the frame to the chainring. On a fixed-gear, you want the distance to the chainring and from the centerline of the rear hub to the cog to be as close to the same as possible. As mentioned earlier in the thread, it's okay to be a couple millimeters off, but I would try measuring what you have and possibly order a shorter bottom bracket if you're much over 42mm:

https://sheldonbrown.com/chainline.html

vailskier3

03-26-19 09:29 AM

i'll have to measure that when i get home from work. thanks for the info! i'm guessing i'll need this info before i purchase my wheelset.

ThermionicScott

03-26-19 09:34 AM

Quote:

Originally Posted by vailskier3 (Post 20855714)

i'll have to measure that when i get home from work. thanks for the info! i'm guessing i'll need this info before i purchase my wheelset.

Track hubs are almost always designed for a chainline of 42mm, that's why I try really hard to get 42mm at the chainring. :thumb:

vailskier3

03-26-19 09:45 AM

Quote:

Originally Posted by ThermionicScott (Post 20855725)

Track hubs are almost always designed for a chainline of 42mm, that's why I try really hard to get 42mm at the chainring. :thumb:

good to know. i am also realizing that most hubs are around 120mm, and my rear dropout spacing is 126mm. i guess i may have to do something different, but i don't know what that is yet, lol.

seau grateau

03-26-19 09:46 AM

You can add a couple 3mm spacers on either side of the axle or cold set the rear triangle to 120mm. Easy breezy beautiful.

ThermionicScott

03-26-19 10:17 AM

^ This. My FG conversion is the same way, it has 126mm dropout spacing. I added a 3mm spacer behind each locknut. :thumb:

vailskier3

03-26-19 03:05 PM

Quote:

Originally Posted by ThermionicScott (Post 20855803)

^ This. My FG conversion is the same way, it has 126mm dropout spacing. I added a 3mm spacer behind each locknut. :thumb:

great info, thanks all! okay, so chainline is looking like 44mm. next! haha. so my next question is are track wheels in play, or no?

seamuis

03-26-19 03:23 PM

Quote:

Originally Posted by vailskier3 (Post 20855745)

good to know. i am also realizing that most hubs are around 120mm, and my rear dropout spacing is 126mm. i guess i may have to do something different, but i don't know what that is yet, lol.

you wouldn’t actually need to do anything if you use a 120mm hub. I have a 126 conversion and it takes literally no extra effort to simply hand tighten the nuts down and take in the 3mm per side. I mean, there’s nothing wrong with dropping some cash on a couple of spacers, but it’s completely unnecessary.

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