A few questions about the crank and bottom bracket

humbert · 23-07-2008 06:18PM #1

I'm pretty clueless about bicycle maintenance so you'll have to excuse me if I get the names of different parts wrong

The problem I'm having is that there is an awful clicking coming from the bottom bracket or pedal, it only occurs when I'm putting a fair amount of pressure on the left pedal but I cant for the life of me determine whether it's the bearings at the bracket or at the pedal. I can't put enough force on it with my hand to reproduce it.

I've taken the chain off and spun the crank and it spins freely and quietly. I'm not sure if it's having an effect on the freeness while it's happening, sometimes I think it is but I could just be a little tired or the road might be sightly uphill.

The disk that the cogs are on at the front(it prob has a name) is a bit warped, it's east to see when it's spinning so I'm thinking of replacing it anyway. I took a look on chainreactioncycles.com and was a little shocked by the number of different options!

What does "Super Narrow HG" mean wrt a chain, might that mean it wont be compatible with the cassette at the pack

There are two numbers e.g., 170mm 39.53, I know what the 170mm is but what is the other??

Will all types of crank sets work with the fitting on the bottom bracket or is that another possible pitfall?

Any help would be muchly appreciated!

Oh, I know it's likely to be easier to take it to a shop but I'd like to lear to do it myself if possible.

Al Wright · 23-07-2008 07:45PM

Hi Humbert,
Check if there is any play in the bottom bracket, by attempting to move the cranks sideways. If thats ok, I'd guess that the clicking sound is more likely to be pedal related.
The disk with cogs at the front is the chainset, there are different combinations used on different bikes. A common hybrid bike is likely to have a tripe chainset, the larger cog wheel (chainwheel) having typically 48 teeth, the middle 38 and the smaller inner chainwheel about 28. Road (sports)bikes more often than not are fitted with double chainset, typically 50 + teeth outer, 40 teeth inner. Crank lengths on off the peg gents road bicycles are typically 170mm between centres of bottom bracket and pedal spindle. Hence 170mm 39.53 probably means 170mm cranks, 39 teeth on inner and 53 on outer chainwheels (definately for a fit cyclists road bike). The designation HG-- on the chain is I think a Shimano part no, super narrow probably means 10 speed, Sram use letters PC to describe their chains.
There are different types of fitting on the bottom bracket, most common now on everyday bikes is a tapered square fitting.

For information, search Harris Cyclery for the late Sheldon Brown's web pages, another is CTC(UK) site, Bikes & Bits at bottom of page or go to Forums, technical, bikes & bits etc. Park Tool also have a good site.
After that, the best of luck.

blorg · 23-07-2008 08:18PM

HG stands for HyperGlide which is Shimano's name for its system of ramps cut into the cassette and chainrings to ease shifting. Not really relevant for you.

You need to be careful if getting a new chain to get one for the right number of speeds as the width is different; it's the number of cogs on your cassette at the back that is the determining factor here. "Super Narrow" could mean 9 speed or 10 speed.

Chains are compatible across brands BTW, you don't need to get a Shimano chain as long as you get one that is the right number of speeds (SRAM or KMC could be a good alternative, I tend to use SRAM myself.)

humbert · 27-07-2008 04:59PM

I'm a bit slow to reply but thanks a lot. Much more info than I expected!

I checked for 'play' and there was none so I focused on the pedals and found out that it is the left pedal that's the culprit. Think I'm going to replace the chainset as well as the pedals as it's a bit warped(dunno how it happened).

What exactly does 9 and 10 speed mean? 2 sets of cogs at the front and five at the back and 3 at the front and three at the back(That doesn't really sound correct to me!)?

The two chainsets I'm looking at are this one and this one simply because they are popular and in the right price range, so other suggestions are very welcome! and these pedals, just went for cheap ones.

Once again, any tips or suggestions much appreciated!

penexpers · 27-07-2008 05:26PM

9 speed or 10 speed refers to the number of cogs on the cassette at the back.

humbert · 27-07-2008 06:08PM

Do you mean literally 9 or 10 rings of cogs on the cassette? My bike only has six!

blorg · 27-07-2008 06:14PM

As penexpers says- the number of cogs on the back is what determines chain width, number of cogs on the front is not an issue.

You should be able to bend a warped chainring back with a pliers if it is not too bad- I'd give that a go before replacing your chainset. Also bear in mind that you can get the chainrings on their own, you don't have to replace the whole thing.

If you do replace you will have to make sure you get a chainset that is compatible with your bottom bracket, there are a fair few different interface designs.

blorg · 27-07-2008 06:21PM

10 is standard on most modern road bikes with 9 at the entry level.

6 means your bike must be a bit on the old side. In that case it won't be using an Octalink bottom bracket so those chainsets you linked to won't work (unless you also replace the bottom bracket.) Bear in mind that Octalink itself has been superseded.

On a bike of that vintage I think I'd try bending/replacing the chainrings before you try anything else.

Regarding the chain to get- you should be OK with an 8 speed chain.

humbert · 27-07-2008 06:55PM

It is a pretty basic bike, my thinking generally when buying any part for it is that in the future when I have the budget to upgrade I'll prob buy the frame and use wheels, crankset, etc from the existing bike. I don't know if that's feasible, I haven't really upgraded the current bike so if it is it'd prob be better to learn now!

Al Wright · 27-07-2008 09:29PM

Humbert,
my approach would be not to worry much about transferring parts to a future new frame. I 'lost' a 'good' bike a few years ago and since then have been using a standard production carbon steel framed 1980s sports bike, of course wheels and brakes have been upgraded. I considered buying a new audax style bike many times in the meantime, the main advantage of new bike being lightweight. I've checked out frame geometry, no difference there so handling would be expected to be similar.
I would recommend the use durable (and not top of range) components on the existing bike. When you upgrade in future the older components might not suit or just not look well on a spanking new frame.

zzzzzzzz · 28-07-2008 12:24PM

I'm having a similar problem. Clicking coming from somewhere when I'm putting any amount of power through the pedals - mainly when climbing.

It started happening every so often about 2 months ago. I was using SPDs and I recently switched to Time RXS pedals and the problem persists.

Can't see any play in my BB - besides only got the bike last January. I had the cranks arms off and greased it all up the other day when I was changing the pedals- still no joy... There is a slight buckle in my chain ring but I don't think that's related... Maybe I'll try changing that though.

TinyExplosions · 28-07-2008 12:57PM

It could be that you need to tighten the bottom bracket... I have a similar noise myself and it's either the bottom bracket or coming from the pedals -putting in a sray of lube in both places eases the sound for a while, but I've not fixed it yet!

zzzzzzzz · 28-07-2008 01:01PM

TinyExplosions wrote: »

It could be that you need to tighten the bottom bracket... I have a similar noise myself and it's either the bottom bracket or coming from the pedals -putting in a sray of lube in both places eases the sound for a while, but I've not fixed it yet!

I'll give that a go later on...

humbert · 28-07-2008 09:05PM

Sounds very similar. Unfortunately it looks like my problems are only beginning. Took the pedals off with the intention of putting crap only pair on to see if the sound would go away but when I took them off and looked at the threads they are in a mess. It looks like whoever or what ever put them on in the first place didn't pay too much attention to the thread and the softer aluminium gave way

Andrewf20 · 28-07-2008 09:21PM

Heres a spanner in the works. I got a clicking from what sounded like my XT cranks when under load. No slack, so took apart everything, and regreased everywhere including the pedals, but the clicking was still there. The cycle superstore couldnt fix problem either. In the end it was the axle for the rear wheel clicking off the frame. All it needed was a quick release and some grease. What a rudy run around.

chris85 · 28-07-2008 09:21PM

The clicking or creaking noise as is common could be from the chain gently hitting the deraileur. If its happens when pressure is put on it then body weight is probably tilting the bike and the chain might give a slight slap off the deraileur.

Only an idea, Got a similar noise due to this. Slight adjustment of deraileur and you are rolling

A few questions about the crank and bottom bracket

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