fitting new cranks

coltmanneil

My son made a mess of his crank arms on his mountain bike.Its a specialized Hardtail 2015 model 650B.
Is there any special tools i would need to change the crank arms for the pedals.Was going to re-tap them but dont know the thread size and looks like hes stripped the threads off anyway.
Is there anygood "how to change crank arms anywhere",I ve tried youtube but didnt really find what I want.
Help appreciated.

NeilC
PS Ive also lectured him what left hand thread means.lol

cooldad

Depends whether they are HT2, square taper or splined. HT2 needs a small tool to remove the nut that tightens them, the others need a crank puller.

coltmanneil

Cheers ,I got the crank puller and it worked a treat.Now for putting the new ones on.Is it best to use a torque wrench and what is the force i would use.I went on youtube and they quoted 35/50NM however I would rather get it right????

cooldad

Tight. Very tight.

The Rookie

As CD says, do them up tight, then tighten them some more.

Short of going stupid you won't do it to tight.

Hopefully you made sure that the new arms need the same axle width as the old ones?

coltmanneil

Got the new cranks yesterday from the original supplier of the Specialized hardtail 650B model 2015 bike.I put them on but wrecked the 8mm allan key trying to put them back on.Ive got them on,but they both need to move 5mm inwards and i am 12 stone and I used a long arm 8mm and a small bar.
Again they say they should be torqued on ,but where would you get the correct NM from???Wonder why they are so tight.Both square taper and they look the same spindle width.???
I ll double check this again,but surely the supplier should of given me like/like,are they usually tight to put on.
NeilC

cooldad

Sounds like the new cranks need a different axle length. Docs should say which one.

coltmanneil

Just been having a look on ebay tonight as a reference.When buying cranks it mentions Crank arm lengths ,teeth gauge and speed (how many chain wheels) oh and thread size which is standard.Nothing about spindle gap sizes,so one would imagine this should be standard.
I ll take them off tomorrow and check the internal size where the square taper hole is against the old cranks to be on the safe side.
They look the same but as you say worth checking.
Got no "docs" with the bike apart fro general up keep of it unfortunately nothing technical.
thanks
NeilC

The Rookie

Go to the crank arm manufacturers website and find the documents for those particular cranks, see what BB axle length it's meant for, different arms need different length axles.

JBA

What make is the original crankset and what make are you fitting?

SRAM and Shimano have different tapers so you cannot fit a shimano crankset on to a sram bb.

coltmanneil

This this is the original type for a specialized hardtail 650B 2015 model mountail bike

https://www.google.co.uk/search?q=stout ... cIy003M%3A

I am getting a 8mm drive tomorrow and I will pull the set back off,if your right maybe the taper a 1mm difference of something like that.However this is main reason I went to original bike supplier ,so they could advise me on getting the correct crankset??

cooldad

That brought up a page of loads of totally different cranksets.

coltmanneil

Sorry it should have brought up a selection of cranksets with my original in the center of the screen.
My original one is made by "STOUT" for specialized mountain bike.
I have found the problem as ive just pulled the new ones back off.
Yes you guys were correct.The actual square taper is very slightly different.When I looled at the corners of the new ones the actual taper of the square is slightly(and I mean slightly)smaller than the original.
Whether i could get a small file in and file the 1mm out will be another story,or ask the supplier if he will take these back which I very doubt he will as i ve scratched the new ones.Thankfully with the advice i got from you guys ,ive not damged the spindle which is a positive.
The ones i bought from the orignal cycle supplier were not expensive.
Or try and find a supplier that does STOUT cranksets for specialized mountain bikes.Theres not a lot on ebay ,so i ll go back to the supplier of the cycle and try.
Thanks and help appreciated.
NeilC

cooldad

Stout is a Specialised 'brand'. Probably made by Suntour or something and rebadged.

coltmanneil

Also as you said ,the actual taper where the spindle goes into is deeper on the old crankset,compared to the new one Ive received.Nightmare.When I received it it looked lik/like.I only looked for the square.This probably why i couldnt get it to go all the way on.
cheers again.
Ive wrote to the supplier and see what they can do for me.They dont look easy to source at all.

JBA

Just buy a new bb to match the new chainset you have.

The Rookie

JBA wrote:

SRAM and Shimano have different tapers so you cannot fit a shimano crankset on to a sram bb.

Both use JIS, so yes you can, but there are a few non JIS square taper out there.

BUT Suntour SRAM and Shimano all put the taper in a different place meaning the axle widths are usually wrong with a different brand of crankset.

coltmanneil

This is the reply from the supplier of the cranksets.
"Hello Neil, if it is rubbing on the derailleur then it most likely just requires a gear alignment. This is usually recommended after fitting a new derailleur, cassette, chain, chainset etc. "
Is he right??
I suppose if the derailleur was catching when the chain is moving I wouldnt have much of a problem with the cranks being the incorrect thinkness.
Ive not adjusted the gears before is it much of a job.Or should I still look at fitting the correct cranks.

Cheers guys for the help again.

coltmanneil

Latest info from Specialized was -
Your bike uses a VP-BC73T bottom bracket. These have a crank interface type known as a JIS taper. This makes them compatible with most modern chainsets but not all (some chainsets use an ISO taper which are slightly longer and taper down to a smaller point).



In theory both tapers are interchangeable, although in practise some combinations won’t work due to chainline or clearance issues. Unfortunately, I can’t find any technical details on the ETC chainset regarding taper types. Your best option would be to contact the seller and ask for a suitable square taper bottom bracket to suit a 68mm shell (approx. 118mm length would be appropriate).

Ive got the cranks on anyway but when the gears are moved most of the hit the chain derailleur ,so i might try and adjust the gears (which i dont at present know how to do it),and see how it goes.
NeilC

The Rookie

That reply doesn't address that for a nominal 47.5mm/50mm chainline the cranks may need anything between a 112mm axle and a 123mm axle.

So what cranks have you actually fitted?