Bicycle Mechanics - spindle length question
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06-18-12, 12:55 AM
Hey guys, quick question. I have a 89 Miyata roadie that ive recently put a new BB and crankset in. It had the old square taper and i put a newer style english bracket in it with a RaceFace Cadence crankset that i found at a steal. The problem now is that when i tighten the crank arms all the way up they dont spin freely like they should. I hoped they would loosen up over time but after about 10 miles on it the crank arm just keeps coming loose and im afraid its going to strip out on me. So whats the deal? Is the spindle too short on this particular crankset because the BB is a tad wider on this older bike? Will i have to find another BB or may another crankset? Thanks for any help,
06-18-12, 08:29 AM
they dont spin freely like they should. Do you mean that the bottom bracket bearings are not spinning freely, or the cranks are dragging on something? Sorry if I'm being obtuse :o
You want to be careful with the cranks - if they keep coming loose, it's possible that the taper in the crank has becoming deformed, especially if it has been ridden when loose, or over-tightened onto the spindle a few times. If that is the case, a new crankset might be in order, unfortunately... The BB spindle is usually harder than crank, so might still be ok.
06-18-12, 08:42 AM
Are you saying you switched to an external bottom bracket and now installing the left crankarm locks up bottom bracket?
06-18-12, 08:59 AM
A crankset using an external bottom bracket (what I *think* you're referring to when you say English) uses bearings with bigger seals, and therefore has more friction. This is because the bearings are more exposed, and need to be sealed better in order not to be compromised. You are getting a stiffer crankset and spindle, but that is the unfortunate price you have to pay -- it is the same from Raceface Cadence to Shimano Dura-Ace. The Raceface Cadence crank basically just needs to be tightened down really tight. (I think the instructions say "firmly" but it comes to the same thing) If you like torque wrenches then around 35-50 Nm.
One thing to look out for on older bike frames is that the sides of the bottom bracket need to be faced and the threads inside need to be chased before installing an external type bottom bracket. This is because with a square taper bottom bracket, the relation of the bearings to one another functions independently of the accuracy of the threading of the BB -- everything is just pressed onto the BB spindle. However, with an external bottom bracket, the two cups screw on separately, and if they aren't perfectly parallel, they will wear out really fast, leading to people who didn't do this complaining on the internet about how quickly that type of BB wears out.
06-18-12, 10:22 PM
thanks for the quick replys, yes External BB was the word i was trying to remember. Torque, i finally just wrenched the crank down as tight as i could(i thought it to be a little too much torque for a crank but i just wanted to see if it would hold without backing out). So far so good, if it comes loose again ill take it all back apart and check to see if the BB needs to be faced per the suggestions
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