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-   -   Why does a wheel taco + need new rim (https://www.bikeforums.net/bicycle-mechanics/1084283-why-does-wheel-taco-need-new-rim.html)

Carbonfiberboy 10-15-16 02:03 PM

Why does a wheel taco + need new rim
 
My wife has a rather interesting short person's bike. MTB frame, MTB crankset, road bars, STI shifters, MTB wheels, road tires. It got knocked of its wall mounts, fell, and the rear wheel tacoed, of all the crazy things. The rear wheel is about 15 years old, never had a problem. Shimano RSX hub, 36H Mavic 221 rim, straight 2.0 spokes. I backed off the nipples 2 turns and saw that the wheel had tacoed so bad that the rim is all bent. In all my decades of riding, I've never had a wheel taco. I pulled it back to sort of reasonable, but it has a lot of loose spokes, wobble and runout.

2 questions:
1) Why do wheels taco?
2) What rim can I replace it with? Rim brakes, 36H, 17mm inside width, 22mm outside. A little wider would be OK, but not much. I've looked around but haven't seen anything except used vintage or expensive NOS on ebay. With stuff like this I don't enjoy hanging around for a week trying to snag something. I don't want to buy a new wheel because this older machine is 7 speed so that's probably an ever worse PITA.

Thanks!

Bill Kapaun 10-15-16 02:15 PM

Did you back off all the nipples so ALL the spokes were loose?

Also covered in this thread from a couple days ago-
http://www.bikeforums.net/bicycle-me...heel-warp.html

fietsbob 10-15-16 02:18 PM

Dish.. the spokes on the drive side get nearly Vertical, to pull the hubshell over to make room for all those "speeds" ..

and that is not a stable balance, side to side..

IGH build stronger rear wheels because they only need 1 cog ..and are not dished

Want a walk in and carry it out Machine assembled wheel Check one of the Seattle LBS'




'/,

dabac 10-15-16 02:39 PM

Wheels taco b/c they have two balanced states. Either flat or taco. A strong sideways nudge can flip them from one to the other.
Don't worry about the bike needing 7-speed.
A 4.5 mm spacer (and sometimes a 1 mm too) is all it takes to fit a 7-speed cassette on a 8/9/10-speed hub.

sch 10-15-16 03:05 PM

It is unfortunate you loosened the spokes. A tacoed wheel can be un-tacoed fairly easily by placing it horizontally
with the low spots on a couple of lengths of 2x4 or 4x4 and pushing forcefully down on the high spots. It will pop
back into its original flat configuration, generally with no truing or further adjustment needed. Have done this several
times.

Edit: looks like this was sort of covered in the prior post referenced above.

Carbonfiberboy 10-15-16 03:12 PM


Originally Posted by Bill Kapaun (Post 19124917)
Did you back off all the nipples so ALL the spokes were loose?

Also covered in this thread from a couple days ago-
http://www.bikeforums.net/bicycle-me...heel-warp.html

I searched for "taco" but that thread didn't come up. Yes, I backed the spokes off until all were loose. The wheel didn't look like the one in that thread. With spokes backed all the way off, it had several sharper and more local bends in it. Some of the bends are only ~6-8" long. Rim is trashed. Hub looks fine.

Carbonfiberboy 10-15-16 03:39 PM


Originally Posted by dabac (Post 19124957)
Wheels taco b/c they have two balanced states. Either flat or taco. A strong sideways nudge can flip them from one to the other.
Don't worry about the bike needing 7-speed.
A 4.5 mm spacer (and sometimes a 1 mm too) is all it takes to fit a 7-speed cassette on a 8/9/10-speed hub.

OK. It is a cassette, not a freewheel, so I have the cassette. Looks like the cheapest thing is to buy a whole wheel! Then I don't even have to build anything.

fietsbob 10-15-16 04:32 PM

yup, Distributor to bike shop built wheels are well priced .. ..

taping same rim , flat to its pringled mate & you just move the spokes over 1 by 1 never breaking the lace pattern, is simple.

Carbonfiberboy 10-15-16 06:13 PM


Originally Posted by fietsbob (Post 19125199)
yup, Distributor to bike shop built wheels are well priced .. ..

taping same rim , flat to its pringled mate & you just move the spokes over 1 by 1 never breaking the lace pattern, is simple.

Yep. So far when I've worn out a rim I've never replaced spokes or nipples. Those things seem to last forever.

This wheel I ordered from Amazon. $50 w/shipping. Probably NOS from a distributor.


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