Replacement Chainset Required

christrinder

Hi all. I've got a couple of road bikes, one of which is a Carrera TDF that I use for commuting. Both bikes were due a cable change, so I took the opportunity to upgrade the TDF from 8spd to Tiagra/105 10spd using donor parts from my Boardman bike which was lavished with Ultegra. All was looking great, but because the chain is slightly narrower now, it sometimes falls between the chain rings at the front. I've got a 100 mile sportive at the weekend that I was planning to do on the TDF so I need to get it sorted ASAP (including buying any new parts today). My question is, what chainsets are compatible with what is on there? I immediately searched for Tiagra chainset (also looking at 105 but the price difference is probably too much) but they look like they use a different fitting. The current chainset has an allen-key hole on both sides, visible on the crank arms. Looking at the Tiagra/105 chainsets, they don't. So is it a special sort of fitting I need to buy? Any help would be much appreciated as I'm up against the clock on this one. And just for the astute amongst you wondering why I can't just use the Boardman for the Sportive... well that because it looks like it's going to be wet at the weekend and the Boardman stays clean and dry But also because it's been set-up as a TT bike and I'd feel a bit of a plonker turning-up at a sportive on a TT bike. Thanks again!

dgunthor

christrinder wrote:

All was looking great, but because the chain is slightly narrower now, it sometimes falls between the chain rings at the front

do you mean between the frame and the chainset? if so, adjust the front mech limit screw.
if you mean between the two chainrings then that shouldnt happen.

christrinder wrote:

I immediately searched for Tiagra chainset but they look like they use a different fitting. The current chainset has an allen-key hole on both sides, visible on the crank arms. Looking at the Tiagra/105 chainsets, they don't. So is it a special sort of fitting I need to buy?

sounds like you have a square taper chainset. the modern shimano ones are hollowtech II which use a different bottom bracket

christrinder

Thanks so much for your reply. I've got the limiter screws set-up OK, but the chain sometimes gets stuck between the two rings at the front. I assume because it is a 10spd chain (and thus narrower than the 8spd set-up that the bike came with) that I need a 10spd specific chainset so that gap between the two rings is closer?

Hollowtech - is that a bit like the BB30 on the Boardman where the bit that goes through the bottom of the frame is attached to the crank itself rather than the crank bolting onto a BB.

So what options are there for a replacement then?

keef66

christrinder wrote:

Thanks so much for your reply. I've got the limiter screws set-up OK, but the chain sometimes gets stuck between the two rings at the front. I assume because it is a 10spd chain (and thus narrower than the 8spd set-up that the bike came with) that I need a 10spd specific chainset so that gap between the two rings is closer?

Hollowtech - is that a bit like the BB30 on the Boardman where the bit that goes through the bottom of the frame is attached to the crank itself rather than the crank bolting onto a BB.

Correct; the Shimano chainsets have the axle attached to the drive side crank.

So what options are there for a replacement then?

Buy a 10 speed Shimano chainset and a Hollowtech 2 bottom bracket. You may need a crank puller to remove your current cranks from the square taper BB, alternatively they could be self-extracting and just need a hex key or bit and a bit of leverage. Then you'll need a cartridge BB tool to remove the square taper BB you have in there at the moment. Then a different tool to screw in the outboard HT2 cups. The new chainset should then just slide in, you pop the non drive side crank on, do up the little plastic cap in the end of the axle just finger tight to preload the bearings (you should get the little plastic tool to do this) then progressively tighten the 2 pinch bolts to secure the crank onto the axle

christrinder

Changing the bottom bracket all sounded like a bit of nightmare and I don't have time on my side. So I've just ordered a: FSA Vero Compact N10-11 Chainset (http://www.chainreactioncycles.com/fsa- ... prod129455) - I'm hoping that's going to just bolt straight on?! :?

keef66

christrinder wrote:

Changing the bottom bracket all sounded like a bit of nightmare and I don't have time on my side. So I've just ordered a: FSA Vero Compact N10-11 Chainset (http://www.chainreactioncycles.com/fsa- ... prod129455) - I'm hoping that's going to just bolt straight on?! :?

Well that looks like a square taper chainset so it should. Only possible fly in the ointment is if it doesn't come with any bolts and your current bolts (the hex things you can see in the ends of the axle) don't fit. Have you taken the old chainset off yet?

christrinder

No, not taken it off yet. What started as a gear cable change has got rather expensive. I should have just flogged the bike and bought a new one! :roll:

dgunthor

christrinder wrote:

Changing the bottom bracket all sounded like a bit of nightmare and I don't have time on my side. So I've just ordered a: FSA Vero Compact N10-11 Chainset (http://www.chainreactioncycles.com/fsa- ... prod129455) - I'm hoping that's going to just bolt straight on?! :?

that should be fine

(only issue that sometimes happens is the width of the bottom bracket axle is wider/narrower than intended for the new chainset. this just affects the chain line)

doug5_10

Do you have a crank puller though to remove the current chainset?

christrinder

Crank Puller?! :shock: What's that? I thought I'd undo the bolt and just pull the crank arm off. I assume from your comment it (like everything else) isn't as simple as that?

keef66

christrinder wrote:

Crank Puller?! :shock: What's that? I thought I'd undo the bolt and just pull the crank arm off. I assume from your comment it (like everything else) isn't as simple as that?

I refer the honourable gentleman to my earlier reply:

" You may need a crank puller to remove your current cranks from the square taper BB, alternatively they could be self-extracting and just need a hex key or bit and a bit of leverage."

So it depends. If you undo the bolt, it comes out and leaves the crank stuck on the axle you'll need a crank puller. You'll see threads in the crank which you screw the extractor into. Make sure you've fished out any washers first
If they are self extracting cranks, the bolts will initially loosen then come into contact with a cap screwed into the crank. As you continue to unscrew them against this resistance, the crank will be pulled free of the axle. (unless you've already, mistakenly, managed to remove the cap before tackling the bolt)

A photo of your current crank would help...

doug5_10

Its the tool you will require to remove the cranks from the axle. The cap bolt you describe 'squeezes' the cranks onto the axle with tension. You may be very lucky and be able to pull the cranks off under your own steam after removing the cap bolts, but it is unlikely. There are other methods such as cycling them off or hammering the axle out with a drift, but a puller is the best tool for the job.

dgunthor

e.g. crank puller here:
http://www.parktool.com/product/univers ... anks-cwp-7

apreading

I know you have gone a different way and not switched to Hollowtech as suggested, with good reason I think but if you decide to do that in the future there is another step that was missed - you would probably need the frame 'faced' which means a machine/tool grinding out any imperfections and making sure left/right side faces are perfectly aligned. Bikes with sealed BBs like square taper/octalink often wont have been prepped like this for an external cup and there will be paint and other imperfections that need sorting first.

I think you took the right choice given the urgent need to sort something!

apreading

christrinder wrote:

Crank Puller?! :shock: What's that? I thought I'd undo the bolt and just pull the crank arm off. I assume from your comment it (like everything else) isn't as simple as that?

The bolt you can see is actually just the securing & dust cap. Remove it and the crank will still be wedged quite firmly onto the bottom bracket - you probably couldnt just pull it off by hand. The crank puller screws in and pushes it off the bottom bracket as you wind the screws in. They are cheap and in most 'all in one' bike mechanic sets, even the ones aldi/lidl sell, so you may have one if you have something like that?

See https://www.youtube.com/watch?v=60wtyyXvtOs