Crankset replacement or ignore missing tooth?

d3matt

(Beginners question, but more workshop....)

My Boardman FS Team is nearly 9 months old. Just noticed that there is a broken tooth on the crankset (Truvativ Firex 3.2 GXP 44/32/22T)


Now, do I just file away the damage at the sides and continue to use this with a missing tooth? Or should I replace it?
If I have to replace it, can you replace just the largest ring or do you have to buy the whole lot?

cooldad

Unless you notice it riding I would just leave it unless you use the big ring loads. Not as big a problem as one missing off one of the smaller rings.

d3matt

After some searching I've now seen you can buy a new outer chainring. There's a few cheap ones on eBay, but retail prices very greatly and with many around £50, you might as well buy a complete new chainset. Just seen another thread discussing this [ur=http://www.chainreactioncycles.com/Models.aspx?ModelID=28020]Shimano SLX Chainset[/url]. Anyway, if I've got to spend £20-£50 for an outring, then I think I'd prefer to spend a little bit more and have a complete new set as it also comes with a new bottom bracket.
If I was to go down that route, what should I be looking for as for size, spec etc. I don't want to end up with something that doesn't fit - I've made that mistake too many times now!

Mine is:
Chainset = Truvativ Firex 3.2 GXP 44/32/22T
Bottom Bracket = Truvativ GXP

I see my out chain ring has 104BCD. What does this refer too?
Also chainsets are listed at 170mm or 175mm. What's this referring too?

And one final question...I seem to remember reading in a magazine about elliptical chainsets. Did these catch on?

jimexbox

I wouldn't spend any money unless it was causing a problem.

ride_whenever

Shifting gate, not a broken tooth.

As per usual, it helps the chain move up when shifting to the big ring. Any new triple specific ring will be the same.

cooldad

BCD is the bolt spacing, 107 or 175 the crank length.

nicklouse

lookes fine to me.

not all teeth are present.

d3matt

ride_whenever wrote:

Shifting gate, not a broken tooth. As per usual, it helps the chain move up when shifting to the big ring. Any new triple specific ring will be the same.

Ahh. Is that why its hidden behind the crank?

Thanks to everyone for their answers. I learn a lot from this forum!

nicklouse

actually it does look worse than I remembered.

it does look like the tooth has been removed but there are some Truvativ rings out there with a similar profile to that.

If it works fine then dont worry.

02gf74

there may be a similar cut out on the same chain ring - see if the tooth is present there,

as has been said, some chain wheels are made with missing or what appear to be malformed teeth.

MattJWL

Yep, I also think it's a shift gate. Looks as though the bike's had some good use in 9 months - good stuff!

If I had to pick an area to worry about, it does look like the middle ring has started to wear a bit - but has a lot of life left.

I'm not a big expert on Truvativ stuff, but I know when you buy a new Shimano crankset & BB, you get spacers so that it fits most common frames (the critical dimension is the width of the shell that holds the BB).

Other than that, as CDad said, 170/175 refers to the crank length; which is correct for you depends on your inseam (leg length). If you're doing big, long rides it's worth figuring the correct one, but even if you get it wrong, it's highly unlikely that your legs will burst into flames because of it.

d3matt

MattJWL wrote:

Yep, I also think it's a shift gate. Looks as though the bike's had some good use in 9 months - good stuff!

I haven't actually. Only go out once at weekends and probably over the period, it's averaged once every fortnight. All rides are offroad 100% of the time. I luckily live only a field away from the Ridgeway on the Berkshire downs.

MattJWL wrote:

Other than that, as CDad said, 170/175 refers to the crank length; which is correct for you depends on your inseam (leg length). If you're doing big, long rides it's worth figuring the correct one, but even if you get it wrong, it's highly unlikely that your legs will burst into flames because of it.

I'm very surprised that 5mm is enough to make difference.

MattJWL

I'm very surprised that 5mm is enough to make difference.

Apparently, according to all of the people that research bike fitting it is. However, like I said, my legs never burst into flames when I used someone else's bike with shorter cranks than mine. Check out one of the online bike fit calculators if you want to work out what it's "supposed" to be.