Replacing the cranks/chainrings.

Questions about purchasing bicycles and parts

Replacing the cranks/chainrings.

Postby tuco » Wed Feb 21, 2007 10:20 am

My daughter's bike has 2 chain rings. She's 13 so for racing the roll out is 6m which means the larger chain ring is locked out.

In June we have a time trial up a nasty, nasty steep hill and since there's no restriction in smaller chain rings and the large one is redundant for another 18 months, then I was thinking of replacing the large chain with one the same size as her current small one and then putting on a smaller chain ring for the hill climb. We also have quite a few races on a circuit with a nasty hill in it.

I haven't taken her up the hill yet because I feel bad that I have a third chain ring and she doesn't. I'm trying to protect her knees. If they're anything like mine and my brothers (we've both torn both ACLs) then they need protecting.

I had a look at the set up last night and the large chain ring appears to be part of the cranks. The light isn't that good down stairs so I'll take it outside after work today and have a better look.

I haven't done any serious work on bikes since I was a kid.
I'll have to remove the entire crank set, what tools will I need? Will I need a swear jar?

I'm hoping I can get something second hand because realistically she'll be too big for the this size bike in about 18 months (or less if she doesn't stop growing) The bike is a ladies sized bike with 650 wheels and with small cranks (162mm ?)

I'll have to put a WTB in the market place after I've made a few measurements tonight.

Can anyone see a flaw in my argument for performing this surgery?
User avatar
tuco
 
Posts: 2016
Joined: Wed Oct 11, 2006 3:36 pm

by BNA » Wed Feb 21, 2007 10:28 am

BNA
 

Postby LuckyPierre » Wed Feb 21, 2007 10:28 am

You'll have to tell us what cranks and chain rings your daughter's bike has got, Tuco.
I know that you've explained it somewhere, but how does the 'rollout' and the 'large chain ring is locked out' interact? Are you be able to fit a larger chain ring that stays within her age-group's limits? That is, I was thinking that you could work out what the largest chain ring you could fit was, then fit that and a smaller one that effectivley 'straddle' the existing smaller chain ring. Does that make sense?
User avatar
LuckyPierre
 
Posts: 1432
Joined: Fri Jul 14, 2006 4:37 pm
Location: Canberra, ACT

Re: Replacing the cranks/chainrings.

Postby heavymetal » Wed Feb 21, 2007 10:29 am

tuco wrote:I had a look at the set up last night and the large chain ring appears to be part of the cranks. The light isn't that good down stairs so I'll take it outside after work today and have a better look.

I haven't done any serious work on bikes since I was a kid.
I'll have to remove the entire crank set, what tools will I need? Will I need a swear jar?


If the cranks are removable from the bottom bracket, you will need a crank puller. Looks like this http://www.bicyclewa.com/reviews/crankremover.html

Some chain rings unbolt from the cranks, but you'll still need to pull the crank off of the bottom bracket.

If the cranks are not removable from the Bottom bracket, you'll need the swear jar and another tool to remove the left hand side Bottom bracket bearing and pedals to remove the entire unit.

Depending on the current crank set up, you'll need to buy new chain rings or an entire crank and chain ring set.

Have you thought of fitting 4 chain rings? :D
heavymetal
Super Mod
Super Mod
 
Posts: 1381
Joined: Tue Sep 27, 2005 5:32 pm

Postby mikesbytes » Wed Feb 21, 2007 10:51 am

Whats the BCD? It may limit the size of the chainring you were thinking of using.

Have a nice day
training log
ImageImageImage
A helmet saved my life
User avatar
mikesbytes
Super Mod
Super Mod
 
Posts: 14536
Joined: Thu Dec 01, 2005 10:42 pm
Location: Tempe, Sydney

Postby tuco » Wed Feb 21, 2007 11:10 am

LuckyPierre wrote:You'll have to tell us what cranks and chain rings your daughter's bike has got, Tuco.
I know that you've explained it somewhere, but how does the 'rollout' and the 'large chain ring is locked out' interact? Are you be able to fit a larger chain ring that stays within her age-group's limits? That is, I was thinking that you could work out what the largest chain ring you could fit was, then fit that and a smaller one that effectivley 'straddle' the existing smaller chain ring. Does that make sense?


I know that you've explained it somewhere, but how does the 'rollout' and the 'large chain ring is locked out' interact?


If she goes on to the large chain ring her roll out will be well over 6m which results in disqualification from races.

I'll get the details posted tonight or tomorrow morning.
It does make sense.
She's close to the 6m limit (about 5.90m) so I couldn't go much bigger than than the current smaller chain ring but I was considering your suggestion also. Actually, I suppose I could by locking out another cog on the cassette.
I had a file somewhere which has all the teeth numbers to get up to 5.98m roll out. I'll have to dig it out and study it thoroughly.

I don't remember it needing special tools when I was a kid but then we probably used the multi purpose tool back then - a hammer.
User avatar
tuco
 
Posts: 2016
Joined: Wed Oct 11, 2006 3:36 pm

Postby Mulger bill » Wed Feb 21, 2007 11:38 am

Tuco wrote:I don't remember it needing special tools when I was a kid but then we probably used the multi purpose tool back then - a hammer.


Ah yes, remember it well :) Cotter pins on the cranks. Still got the scars on the ankles. :lol:

Seriously mate, there's quite a few specific tools needed these days. to do this job, you'll need at least allen keys, a crank puller and maybe a BB tool as well. The first two are universal, the BB tool can be maker/design specific :roll: especially if it's one of those newfangled external types.

Does your LBS have any racers on staff? I'm sure one of them could suggest a cost effective workaround.

Hang on, Gururug was talking about shorter cranks here. Maybe you could look at swapping?

Shaun
User avatar
Mulger bill
Super Mod
Super Mod
 
Posts: 25271
Joined: Sun Sep 24, 2006 2:41 pm
Location: Sunbury Vic

Postby gururug » Wed Feb 21, 2007 11:46 am

Go to shelton brown to anlayse what rings and compatibility you might require.

Hopefully they are 130mm-BCD or 110-BCD as these parts will be easier to find / source.

While your at it write down/find out the specs for the bottom bracket (BB) aswell. These may be required down the track

i.e. english or italian, i think there are two other variations with the BB.

:wink:


Some one recommended some token rings to me available from torpedo7.com but this is just one option and i'm pretty sure they would only be 130-BCD.


Have fun Tucster, what you think is a simple unscrew then rescrew actually turns out to be a standards minefield, thank god for bicycles.net.au forums and all the peple who offer assistance in this area.
User avatar
gururug
 
Posts: 1499
Joined: Thu Jan 25, 2007 11:05 pm

Postby amattinson » Wed Feb 21, 2007 8:01 pm

Just in case you need tools Torpedo 7 has a special on a toolkit this week.
amattinson
 
Posts: 34
Joined: Thu Jul 27, 2006 8:57 pm
Location: Hornsby, Sydney

Postby tuco » Wed Feb 21, 2007 10:17 pm

Okay, it's not looking easy.

They're 110mm BCD. 5 arm. 162mm cranks.
The brand seems to be Truvativ touro.
The large chain ring is 52 and the small one is 39.
Cassette 12-13-14-15-16-18-21-24
To make her race legal I've locked out the 52 chain ring and 12-13 on the cassette.

I can see where the problem is going to be. The bolt holes are so close to the outside of the 39 ring that a smaller ring can't be fitted. A smaller ring would have to be fitted where the third ring normally goes but sadly there are no bolt holes in the 5 arms for it to attach to.

So far I would need a new crank arm suitable for a triple and a smaller chain ring.

Would it be too easy for the right crank arm to come off and be replaced with a triple without having to remove the bottom bracket or is the cycling world just as twisted as the rest of the world?

Looks like I might have to give it a miss.
User avatar
tuco
 
Posts: 2016
Joined: Wed Oct 11, 2006 3:36 pm

Postby Mulger bill » Wed Feb 21, 2007 10:23 pm

If it's a sorta standard sealed BB, you won't have to touch it, undo crank bolt, use puller as directed, crank falls into your hand (hopefully) Reverse procedure to install.

Question... greasing the tapers on the spindle, yes or no?
User avatar
Mulger bill
Super Mod
Super Mod
 
Posts: 25271
Joined: Sun Sep 24, 2006 2:41 pm
Location: Sunbury Vic

Postby europa » Wed Feb 21, 2007 10:25 pm

Yes, grease it.

Tuco, you may be able to fit an mtb crankset onto that bb - and considering the 'short' expected life, second hand springs to mind.

Richard
User avatar
europa
 
Posts: 7327
Joined: Sun Jul 16, 2006 10:51 am
Location: southern end of Adelaide - home of hills, fixies and drop bears

Postby heavymetal » Wed Feb 21, 2007 10:33 pm

tuco wrote:Would it be too easy for the right crank arm to come off and be replaced with a triple without having to remove the bottom bracket or is the cycling world just as twisted as the rest of the world?


Usually, but, the bottom bracket's spindle may not be long enough to accept a triple :shock:

The final resting place of the triple's rings may be out of alignment with the rear cluster.

They usually do swap over without these problems. I've just gone through something similiar in fitting an MTB triple in lieu of my road triple to my touring bike.

I went from 30-42-52 down to 22-32-42 and didn't have any problems.
heavymetal
Super Mod
Super Mod
 
Posts: 1381
Joined: Tue Sep 27, 2005 5:32 pm

Postby Mulger bill » Wed Feb 21, 2007 10:37 pm

europa wrote:Yes, grease it.


Thanks Richard, I do already. 8) :lol:

This is another one like the chain cleaning thing, sure to start a post ride fight between greasers and dryboys.
User avatar
Mulger bill
Super Mod
Super Mod
 
Posts: 25271
Joined: Sun Sep 24, 2006 2:41 pm
Location: Sunbury Vic

Postby mikesbytes » Thu Feb 22, 2007 8:01 am

110 BCD should be able to fit a 36 or even a 34?

Have a nice day
training log
ImageImageImage
A helmet saved my life
User avatar
mikesbytes
Super Mod
Super Mod
 
Posts: 14536
Joined: Thu Dec 01, 2005 10:42 pm
Location: Tempe, Sydney

Postby tuco » Thu Feb 22, 2007 11:46 am

I'm thinking it might be best to drop the bike around to the lbs and have a chat to them - not that you people haven't been useful.

It's very frustrating being handy with tools but the tools required are so bloody expensive and I'll probably only use them once.

For the short live of the conversion I'd rather go used parts. I looked at some new crank sets and they were half the cost of the bike which is only second hand anyway.

I like the good old days when a hammer, 2 spanners and a screw driver would fix anything on a bike.
User avatar
tuco
 
Posts: 2016
Joined: Wed Oct 11, 2006 3:36 pm

Postby europa » Thu Feb 22, 2007 12:24 pm

tuco wrote:I like the good old days when a hammer, 2 spanners and a screw driver would fix anything on a bike.


They still can ... but it depends on whether you're interested in maintaining the factory finish :twisted:

I've always had the theory that you buy good tools as you need them. Expensive tools (like my table saw), you borrow or take the job to a mate's or pay the lbs to do the job, until that becomes a real pain in the neck, the theory being that if you only use it once, it's not a problem. If you find yourself at the lbs every three weeks to get a crank pulled, it's time to buy a crank puller. The pay off isn't so much in what you save in paying for labour, but in the number of times you'll actually do the job properly yourself now that you have the tools rather than 'let it go' until 'it really needs it' - in other words, having the right tools usually results in better maintenance ... or more visits to the lbs shop after you've broken something ... again :roll:

Mate, you and your daughter are into racing and look like you'll stay there for a bit. Buying tools as you need them now will probably pay off in the long term. The only danger is buying a specialist tool that will be useless on the next groupset you buy ... but there'll always be someone in the club who can use it or might be interested in buying it.

Richard
User avatar
europa
 
Posts: 7327
Joined: Sun Jul 16, 2006 10:51 am
Location: southern end of Adelaide - home of hills, fixies and drop bears

Postby tuco » Thu Feb 22, 2007 12:48 pm

europa wrote: ... but there'll always be someone in the club who can use it or might be interested in buying it.

Richard


THE CLUB! I didn't think of that. They have a some what messy tool kit IE the tools are spread all over the floor.

They may have the right tools. But then it still comes down to the bike only costing $450 and new crank sets are a few hundred.

I'll see what the club has then make a decision.
User avatar
tuco
 
Posts: 2016
Joined: Wed Oct 11, 2006 3:36 pm

Postby LuckyPierre » Thu Feb 22, 2007 5:31 pm

Here's one way to get 5-arm 110mm BCD chain rings. Sadly, a look on the Shimano website showed that all of their mtb cranks have now moved to 4 arms.
Given that the cranks are Truvativ, you should be able to chain rings, even if your local shop has to order them in. As far as I could tell from thecompatability chart, if the rest of the groupset is 8-speed Shimano, then any HG chain ring will be compatible, as long as it has the right BCD / arms. That's one of the good things about Shimano's HG stuff - you can mix and match all sorts of thengs between road and mtb. Richard's Black Beauty is a good example, isn't she Richard?
User avatar
LuckyPierre
 
Posts: 1432
Joined: Fri Jul 14, 2006 4:37 pm
Location: Canberra, ACT

Postby tuco » Thu Feb 22, 2007 5:50 pm

LuckyPierre wrote:Here's one way to get 5-arm 110mm BCD chain rings. Sadly, a look on the Shimano website showed that all of their mtb cranks have now moved to 4 arms.
Given that the cranks are Truvativ, you should be able to chain rings, even if your local shop has to order them in. As far as I could tell from thecompatability chart, if the rest of the groupset is 8-speed Shimano, then any HG chain ring will be compatible, as long as it has the right BCD / arms. That's one of the good things about Shimano's HG stuff - you can mix and match all sorts of thengs between road and mtb. Richard's Black Beauty is a good example, isn't she Richard?


Sadly the cranks are 175. She needs 162 since it's a smaller ladies size bike.

I was going to ride around to the lbs tonight but it rained. Wait a minute, today's Thursday. I think they're open late. I'll see if I can get out there later.
I was going to relate the saga to them and see if they could help with some used parts.

The rest of the set is 8 speed shimano. I've been thinking of mixing and matching. Problem is everything new is half the original cost of the bike. If she wasn't going to grow over the next 12 months then I'd be happy with that but she'll need a larger frame next year.

Actually, just getting back to that auction, that crank would come off the chain rings and I could attach the 162 cranks she currently has on her bike.
Can anyone suggest the wording of a question to the seller to find out about the compatibility of the auction item to the Truvativ?
Sorry, I'm still new to all the terminology. It's been over 20 years since I had bikes in pieces.
User avatar
tuco
 
Posts: 2016
Joined: Wed Oct 11, 2006 3:36 pm

Postby LuckyPierre » Thu Feb 22, 2007 6:37 pm

tuco wrote:
Sadly the cranks are 175. She needs 162 since it's a smaller ladies size bike.

I almost got caught doing what Richard accuses you of - only reading the first paragraph, so I was just about to fire off a "you only need the rings, silly!" post - but read on a bit (admittedly while I was deleting some of your message in the quote) and you saved yourself.
I don't think that you need to ask the seller - if your daughter's chain is an HG one, they will be compatible. If they aren't, sell them to me, because they'll fit my mtb. :wink:
User avatar
LuckyPierre
 
Posts: 1432
Joined: Fri Jul 14, 2006 4:37 pm
Location: Canberra, ACT

Postby tuco » Thu Feb 22, 2007 7:54 pm

There goes that plan down the crapper.
My daughter's 165 cranks don't have the holes in them for the third chain ring.

However I will have a look at ebay.com. So far I've only looked at ebay.com.au
User avatar
tuco
 
Posts: 2016
Joined: Wed Oct 11, 2006 3:36 pm

Postby LuckyPierre » Thu Feb 22, 2007 8:19 pm

B*gger! I think that you're right.
I was going to say: "No, we're only after a double chain ring, you just need a smaller ring than a 39" - ie. the middle ring from the cranks on eBay. But that is bad thinking, because the ramps et. al. on what is normally an inner ring probably mean it can't act as an outer ring (ie. promoting the current inner ring to the outer ring) and what is normally a middle ring probably won't work the best as an inner one.
Fun, isn't it!
I just pulled an HG compatible mtb triple apart (a Deore one) and the spider (drive-side crank arm) has castings for the inner chain ring that are separate from those for the middle / outer rings (which share the same ones). Given that most mtb cranks are longer than road ones, this grand idea is probably dead! :?
User avatar
LuckyPierre
 
Posts: 1432
Joined: Fri Jul 14, 2006 4:37 pm
Location: Canberra, ACT

Postby mikesbytes » Thu Feb 22, 2007 8:53 pm

With all the trouble you seem to be having with getting the right chain ring, have you considered changing the cassette ?

Have a nice day
training log
ImageImageImage
A helmet saved my life
User avatar
mikesbytes
Super Mod
Super Mod
 
Posts: 14536
Joined: Thu Dec 01, 2005 10:42 pm
Location: Tempe, Sydney

Postby Bnej » Thu Feb 22, 2007 9:13 pm

Three Words:

Schlumpf Mountain Drive...

or is $700 + too much? ;)
User avatar
Bnej
 
Posts: 2880
Joined: Fri Jun 30, 2006 11:43 pm
Location: Katoomba, NSW

Postby LuckyPierre » Fri Feb 23, 2007 7:44 am

mikesbytes wrote:With all the trouble you seem to be having with getting the right chain ring, have you considered changing the cassette ?

Given that your daughter's effectivley using a 12-13-14-15-16-18-21-24 cassette it would be worth experimenting with Mike's idea. It shouldn't be too hard to find an 8-speed mtb cassette to play with. I realise that the rear derailleur will have a 'maximum number of teeth' it can handle, but I don't know what the impact of 'locking out' some ratios will be. Any HG cassette is a potential candidate for experimenting. It could be interesting to see whether a 7-speed would work, given that not all of the cassette is being used - I can send you a couple of them to play with. Extending this line of thinking, a 12-27 9-speed is also a candidate (because most 8-speed hubs are 7/8/9-speed compatible), but I need my granny gear more than your daughter does! :)
User avatar
LuckyPierre
 
Posts: 1432
Joined: Fri Jul 14, 2006 4:37 pm
Location: Canberra, ACT

Next

Return to Buying a bike / parts

Who is online

Users browsing this forum: Exabot [Bot]



Support BNA
Click for online shops
Torpedo 7 Torpedo7 AU
Ground Effect Ground Effect NZ
Chain Reaction Cycles CRC UK
Wiggle Wiggle UK
Cycling Express Cycling Express
Ebay Ebay AU
ProBikeKit ProBikeKit UK
Evans Cycles Evans Cycles UK
JensonUSA Jenson USA
JensonUSA Competitive Cyclist