gt id 5 crank noise

mick_brett

Hi
Have had my my GT id 5 in with halfords a number of times for a knocking in the crank when under pressure. Has anyone else experiened this problem. The head mechanic has told me he's dismanteled the whole bottom bracket one the two occasions that i have returned the bike and that everything looks perfect, yet the noise remains when I'm pushing uphill. Any wise words out there for me?
Cheers
Mick

Si.Ozzy

My commuter bike and a colleagues bike had exactly the same problem, its so annoying.
I know they have said its not the bottom bracket but i would have a look yourself, its sounds like its either that or possibly the crankset isnt sat on the bottom bracket properly.

First thing is to see what bottom bracket it is, some of the halfords own use a solid axle with a bearing cage on either end of the axle, if this is the type you have you will need a square taper crank extractor, it will have a silver plate on the crankset with little notches cut out in about three places around the outside. I doubt Halfords gave it a really good clean, all it takes is a small piece of grit to be on the bearing cage to give you the noise. Take it out and give it a complete clean and it will fix it.

GT may have put a sealed bottom braket, this wont have a silver lockring, instead it will have a circular cup which screws into the bottom bracket shell, it will have teeth all round the outside, if this is the case you will need a bottom bracket tool and a crank extractor (unscrew the crank bolt on the outside of the brank arm and see whether the spindle inside is square or round, this will depend on what crank extractor you'll need. You cant clean this and will have to buy a new bottom bracket which you can buy a basic one for about £12.

supersonic

Check the Idrive mechanosm - the dog bone and bearings.

Skonk

Pretty much everyone I've seen posting on this forum who own GT I-Drive bikes have the same creaking problem, myself included.

Seems it's just what the I-Drive bikes do.

It's not the bottom bracket causing it, but rather the two pivots above it.

The system is a little odd really and if you dismantled it and had a good look at how it's put together, it's pretty clear why it creaks.

The system is held together with a large aluminium cylinder (pivot) which pulls all the components together, but this cylinder is actually smaller by a mm or two then the hole it goes through.

It works because of some tapered elements which when compressed together hold it all in place. If it's too loose, then there is play (because the pivot doesn't fit snug in the holes) but if you over-tighten it, you damage it because the metal is very soft.

End result is you get a little bit of play in each pivot, which add together to cause the creak and in some cases you can feel the slight bit of play in teh system as you put pressure on the crank.

I did the red xc trail at Dalby Forest yesterday and while I enjoyed the ride, the creaking really started to bug me to the point where I'm now considering replacing the bike.

supersonic

Mine never creaked, not in the slightest.

gregmorris234

Mine creaks i really do think its just and I-Drive thing!

Anonymous

it does seem to be common these days unless you strip the pivots and pack them with something like marine grease or summat. even then it may well need to be done pretty often.

Skonk

When I can be arsed I strip it down and re-grease it with copper grease (as recommended by GT), this clears up the problem for 2 or 3 rides but it always comes back.

Anonymous

theres a load of folk having trouble with theirs over on mtbr.com

gregmorris234

I emailed Gt and they told me to take it back to the shop and tell them to dismantle all the pivots, clean em, and put anti seize on it. Not grease because it's not thick enough!

Skonk

gregmorris234 wrote:

I emailed Gt and they told me to take it back to the shop and tell them to dismantle all the pivots, clean em, and put anti seize on it. Not grease because it's not thick enough!

It will clear up the noise for 2 or 3 good long rides but then it'l come back imo.

gregmorris234

I thought it would!