Tapered crank spindles; what fits what?

[mikes105]

[attachment=3502][attachment=3503]The wife asked me to convert her ten spd to a single speed. The project was moving right along. I found a Shimano coaster brake hub to replace the freewheel rear hub. It comes with an 18T cog. Up front there's a problem. I wanted to set up a 42-18 gearing so a new chainring is needed. But the Takagi crankset does not have a spider on the drive crankarm. The outer ring mates directly on the spindle and the inner ring bolts to it. Searching for a Takagi compatable chainring has been fruitless. So change the drive side crankarm to one with a spider? OK, but what fits what in the world of cranksets? This spindle is 16.5 mm diameter and has a square taper. Is the taper on all crank spindles the same?

[xerxes]

It's almost certainly a JIS square taper and pretty much any new square taper chainset/crankset will fit.

Everything you ever wanted to know about square taper bottom brackets: http://sheldonbrown.com/bbtaper.html

[mikes105]

(09-13-2012, 07:27 AM)xerxes Wrote:  It's almost certainly a JIS square taper and pretty much any new square taper chainset/crankset will fit.

Everything you ever wanted to know about square taper bottom brackets: http://sheldonbrown.com/bbtaper.html

Xeres, thanks once again for the enlightening link.

One other consideration; I was going to dish the rear hub to align the chainline. Shelton Brown's article mentions selecting an axle length to align the chainring with the cog. Is one method preferable vs. the other?

[nfmisso]

"dish the rear hub" ?????

typically the rear hub defines the location of the cog, and there is not any flexibility.

Is the OLD of the new wheel the same as the old? Things need to be fairly close for things to work. If the new hub is narrower, there is a potential to use washers if the axle is long enough.

At the front, the chain line is set by the BB axle length.

[xerxes]

Quote:One other consideration; I was going to dish the rear hub to align the chainline. Shelton Brown's article mentions selecting an axle length to align the chainring with the cog. Is one method preferable vs. the other?

There's already a rear brake, can I ask why you want to replace the rear hub with one with a coaster brake?

If you have a cassette and freehub you can replace it with a single speed sprocket and spacers using the existing freehub like this: http://www.ebay.co.uk/itm/Single-Speed-bicycle-freehub-conversion-kit-18T-210-005-/370468393952?_trksid=p3284.m263&_trkparms=algo%3DSIC%26its%3DI%26itu%3DUCI%252BIA%252BUA%252BFICS%252BUFI%26​otn%3D21%26pmod%3D330787814236%26ps%3D54. The use of the spacers will allow you to adjust the chainline so that it works with the new chainset on your existing bottom bracket axle.

If you have a freewheel, you can use a single speed freewheel: http://www.ebay.co.uk/itm/Shimano-MX-18-Tooth-Single-Speed-Freewheel-1-2-x-3-32-Compatible-/350592289994?pt=Cycling_Parts_Accessories&hash=item51a0edccca

You can then use a different bottom bracket axle length to adjust the chain line. The Shimano UN55 is good quality and available in a wide range of lengths: http://www.chainreactioncycles.com/Models.aspx?ModelID=71369

[DaveM]

(09-13-2012, 09:52 AM)nfmisso Wrote:  "dish the rear hub" ?????

typically the rear hub defines the location of the cog, and there is not any flexibility.

Is the OLD of the new wheel the same as the old? Things need to be fairly close for things to work. If the new hub is narrower, there is a potential to use washers if the axle is long enough.

At the front, the chain line is set by the BB axle length.

Well, on many hubs, you can move spacers around on the axle to help get the cog lined up where you want it. Then you would re-dish the <i>wheel (spokes)</i> to get the rim centered over the axle.

A secondary method to get a straight chainline is to swap out the BB spindle to move the front chainring in or out. If needed, you can sometimes just reverse the existing spindle. This will often bring the chainring in closer to the frame. (Spindles are often slightly longer on the drive side.) On the new crank, you may also be able to move the chainring from the outside of the mounting plates that hold it to the inner side.

There's a few ways to tinker with the chainline when converting to single. You may have to put it together, test, and redo a few times. Unlikely you'll just get all the parts and throw it together perfectly. But mostly fun and straightforward stuff.

[mikes105]

Thanks y'all for the great advice. I'm thinking that nfmisso is right on; this is going to take some tinkering (with crank spindle lengths and rear hub spacers).

Xerxes asked, "why a coaster hub"? The wife's specification was for a single speed like the (cruiser) bike of her pre-college era. And, those existing brakes are the dual pivot type with the arms joined by a cable yoke. Not enough leverage to slow a runaway hamster.

[xerxes]

Quote:The wife's specification was for a single speed like the (cruiser) bike of her pre-college era. And, those existing brakes are the dual pivot type with the arms joined by a cable yoke. Not enough leverage to slow a runaway hamster.

Can't see them very clearly in the picture, but they look like centre pull brakes. Have you tried some new brake blocks? Brake blocks seem to go "off" if left sitting around for a few years, try something like Koolstops: http://www.koolstop.com/english/road_pad.html you might be surprised by how much better than the old brake blocks they are.

[nfmisso]

I would scrap the center pulls, and get some Tektro dual pivot side pulls - MUCH more effective. Measure the reach carefully, see Sheldon's webpage on the subject.

Coaster brakes are not very good compared with modern dual pivot side pulls or linear pull brakes. The bike in the picture does not have provision for linear pull (aka V-) brakes. Dual pivot side pulls are the next best thing - unfortunately they are considerably more expensive.

[mikes105]

nfmisso, thanks for the direction to Shelton Brown/Harris Cycle webpage on brakes. Lots of good info' of how things have changed since the late ' 70's.

I've noticed that center pull brakes are back, but a much more robust construction, on some MTB models.

I do have a set of Shimano 600 side pull brakes that I could contribute to this project. The front bolts right on but a custom bracket would be needed to mount the rear. Of course if I did this then new brake levers would have to be sourced.

No, guys, I'm stickin' to the original spec' and building a new rear wheel around a Shimano coaster hub. I have the rim.... the mate to front in the photo. I'll add a new crankset sized on the gearing that suits the wife. Maybe incorporate that Shimano 600 front brake with a new lever.

[DaveM]

Can't be sure from the picture, but I think you have a steel rim on the back at least. No brakes work very well on steel rims. Going to alloy with any brake will work better.

That said, coaster brakes are very powerful. If your wife liked them before, I see no huge reason not to do that. Note though that a strong rear brake only does so much. The front brake can give twice as much stopping power as the rear. If you have a better brake caliper, I'd put that on the front even if you don't change the lever. Or at least good new brake pads.

[Bill]

Just wanted to say thats a pretty bike .