Giant Defy - chainset/chainstay clearance

leighz

Anyone with one of these can have a look at the non-drive side crank clearance (by the pedal) - just put my hollowtech sora compact 175mm cranks on mine and it's minimal - like about 1mm......was quite tight on my old frame but this seems ridiculous which makes me think I'm either doing something wrong or the crank arm is bent.

ta

topdude

Hi, on mine with an FSA chainset there is about 10 to 12mm clearance between both cranks and chainstays.
Yours does not sound right, try fitting the chainset the wrong way round and see if the tight clearance swaps sides :?:

leighz

intruiging - what fsa chainset/BB combo is it? Mine uses external BB cups with no spacers between them and the cranks

(will try fitting them the other way round as you suggest - fwiw the drive side spacing is about 6-7mm from crank arm to chainstay)

Monty Dog

Careful fitting cranks wrong-way around - some frames are manipulated on the RH chainstay to give chainring clearances, so it might not work. A bent crank is often visually quite obvious - rotate the crank by hand and track the end of the arm by eye to see if it changes track. Another option is that the whole frame is mis-aligned.

leighz

fitted them on the wrong way round and gained a mm clearance on the non drive arm (now on the drive side) and lost a mm on the drive arm on the non drive side. Confused?

Put it all back as it should be and tightened the plastic 'snugging up' cap or whatever you call it quite gently and possibly gained as much as ooooo half a mm on the non drive side. It's not striking the chainstay but with a bit of flex it will. Maybe I should go ride the thing and not worry about it.

topdude

That just sounds wrong :?
Post some photos of cranks, chainstays and bottom bracket.

gmacz

I had problems with an old BB having a different profile square drive. I had about 0.5mm clearance on the middle ring and frame. It just sat further into the crank arm, with a modern new square drive it was back to normal. I also went wider than the standard 116mm and have found it has improved my feet position and is more comfortable.

leighz

pics:









whilst in lbs buying a brake cable chatted to the guy in there about it and he kindly gave me a couple of shims to try out - a 1mm, and 2 x 0.5mm so I could space out the non-drive side if I wanted. Would prefer not to do this since shimano say road BB's don't need shims (if they're a double/compact double). Sticking a feeler gauge between crank and stay and it's only 0.6mm - although I put a bit of helicopter tape there to try and prevent scuffing so that will have reduced it slightly.

Originally, the frame would have had a triple on it and hence wider spacing - but not sure I believe Giant would design the chainstays differently just to accomodate this.

Monty Dog

Your non-drive crank arm looks bent?

lef

that looks wrong, I personally wouldn't ride it. I'd have a good LBS take a look and see what their reaction is.

topdude

Good photos, always better than trying to describe a problem.
That non drive side crank is either bent or badly machined and not sitting on the axle correctly.
I would not be riding that in case of damaging the chainstay.
Suggest having a different chainset fitted as that one looks so wrong :shock:

stokey1964

hard to say but it looks like the hole for the spindle spline has been drilled cocked eyed.

I think it would be hard to bend an hollow tech crankarm, Either way see if you can borrow a NDS crank arm off a mate and try that. This should prove that its the arm a fault


Simon

rolf_f

stokey1964 wrote:

hard to say but it looks like the hole for the spindle spline has been drilled cocked eyed.

I think it would be hard to bend an hollow tech crankarm, Either way see if you can borrow a NDS crank arm off a mate and try that. This should prove that its the arm a fault

Possibly so! To me, the crank arm looks as straight as a die. What looks miles out in the 3rd pic is the angle between the hub of the crankarm and the bottom bracket axis.

slowondefy2

Dont know if this helps but here's some comparable photos from my stock (double) Defy 2 2010 (Linky for specification):







The minimum clearance is equal both sides at (about) 5mm.

Sorry about the toe :oops:

stokey1964

If you hold a straightedge to the outside face of both yours and slowondefy2's crank arm they both tie up to the centre of the pedal axle.

based on this I dont believe you crank arm is bent but it seems to confirm my original theory that the hole for the spline on the crankarm has been drilled off centre.

If you let us know where you are based Im sure someone locally would try a crankarm for you to confirm 100% or you try yours on their bike. should only take about 10mins

Simon

leighz

slowondefy - pics are just what was needed

still doesn't explain why clearance is virtually the same if I put the cranks on the wrong way round

will see if I can part my riding buddy's nds crank from him and give that a go

Monty Dog

If the cranks are out when inserted either way, then shows they are true. This would suggest that the BB shell is misaligned. May be worth asking you LBS to check the frame alignment.

leighz

did the sheldon trick of running a bit of string from dropout round headtube and back to the opposite dropout to check alignment. Frame is indeed not straight. NDS 33mm/30mm DS. Also measured an alternative way to double check and got NDS 48mm/44 DS. So frame is between 1.5mm and 2mm out on each stay.

Double checked spacing at end of crank
with cranks on wrong way:
NDS 2.2mm
DS ~4mm

with cranks on right way:
NDS 0.8mm (more like 1mm with helicopter tape removed)
DS 5.5mm

this suggests cranks are bent also. wtf?!? Also that the mis-alignment of frame favours the cranks not hitting the chainstay - if I tried to correct it surely they would definitely hit the NDS. Not that you can cold-set an alloy frame according to sheldon

not had chance to try another pair of cranks yet

Twostage

In the third picture it definitely looks like the crank is not square to the BB. So could be badly drilled crank as suggested or could the BB spindle be bent ?

thescouselander

Looks to me that the crank arm is not installed squarely on the BB spindle. I'm not sure how this could have happened but I'm guessing the tightening bolts on the crank are were very loose when it was mounted on the spindle allowing some play between the arm and the spindle.

Try tightening the bolts up on the crank arm a touch before installation so it will just slide over the spindle to make sure the splines are aligned correctly within the crank arm.

leighz

thescouselander wrote:

Looks to me that the crank arm is not installed squarely on the BB spindle. I'm not sure how this could have happened but I'm guessing the tightening bolts on the crank are were very loose when it was mounted on the spindle allowing some play between the arm and the spindle.

Try tightening the bolts up on the crank arm a touch before installation so it will just slide over the spindle to make sure the splines are aligned correctly within the crank arm.

tried your suggestion - no difference

thescouselander

Strange. Could you take both halves of the crank off the bike and reassemble on its own - that way you can check if the crank arms are square with the spindle.

rolf_f

Just a thought. Ignoring the frame, the obvious theory is that the nds crank isn't aligned perpendicular to the bottom bracket - hence it is angled in thus causing it to nearly foul the chainstay.

Now, the first few cm of the inside face of the crank have little curvature to them (and not much compared to the misalignment issue).

So, you could mount the crank arm on so that it is has the same orientation as the drive side crank arm. Then measure the distance between the inner faces of the crank arm right at the tip and again nearer the axle before the arm starts to curve in noticeably. There should be a small difference if any (depends on how long they remain parallel) - but if the nds crank arm isn't aligned correctly, the difference should be very obvious. I think!

It may provide the answer or it may not but it's only a moment or two to try!

rolf_f

slowondefy2 wrote:

Dont know if this helps but here's some comparable photos from my stock (double) Defy 2 2010 (Linky for specification):

Do you often come back to your bike to find members of Greenpeace pulling half dead cormorants off your chain and trying to clean them?

leighz

with mates cranks on....



which is about 1mm better.

topdude

Sorry but it looks like the frame / BB is the problem !!

slowondefy2

Rolf F wrote:

slowondefy2 wrote:

Dont know if this helps but here's some comparable photos from my stock (double) Defy 2 2010 (Linky for specification):

Do you often come back to your bike to find members of Greenpeace pulling half dead cormorants off your chain and trying to clean them?

It's not quite as bad as it looks, the finishline ceramic wet lube seems to go like this within only a few miles. Although I do admit it does need some TLC :oops:

rolf_f

topdude wrote:

Sorry but it looks like the frame / BB is the problem !!

If the frame is the problem then it's likely that if the crank is too close on the non-drive side, it will be too far away on the drive side. Th BB I'd guess is more likely to give a problem on one side only.

So we need to see a drive side pic to compare with SlowonDefys.

leighz

such as....



?

tried yet another way of measuring with string through fork dropouts and then rear dropouts which shows seat tube to be near equidistant closer to the BB.

the chainstays are clearly asymmetric, with the NDS having a decreased radius curve next to the straighter DS.

There's no signs of any cracked paint/tubes/welds. The crank doesn't actually hit (I rode it the other night with no probs) and the frame in it's original incarnation would have had a triple where you simply wouldn't notice this. I'm tempted to just go ride the thing.