External BBs

[bigjim]

Hi
I'm fitting [or trying to fit] a Tiagra Triple Road chainset to a Harry Hall frame using a Hollow tech BB. The spindle does not protude far enough into the left side cup to enable the l/h crank to be tightened up correctly. The cups are 11mm wide. One spacer on the drive side and no spacer on l/h side. Also the inner ring is not that close to the chainstay so chainline would not be great. I assume 68mm BB as it is a late 80s 531 frame. Am I missing something? Looking on ebay cannot see a cup size on BBs.
Jim.

[Erudin]

There should be no spacers between the cups and frame with a road chainset, a standard road bottom bracket should be 68mm wide and not require any additional spacers (the 2.5mm spacers are generally only required on MTB setups where the effective width of 73mm needs to be created on a 68mm shell).

Below is a pic of my Thorn with a Tiagra triple chainset (68mm bb).

[cycleruk]

Easy enough to measure the shell width to verify if 68mm.
Measure from centre of downtube to middle ring to check chainline. Tech' doc's say 43.5mm (checked mine and yes they are.)
Although mine are 105's.
http://bike.shimano.com/content/sac-bik ... -4703.html

The three BBs I have all are the same cup size. 11mm
Tech' Doc's show spacer on the drive side spindle but mine came without. So fitted and working O.K.
If you have fitted a spacer on the drive side spindle then try it without. Keep the large "washer" on the non-drive as it keeps the dirt out of the bearing.

[AndyA]

You might be missing the spacers that fit on the crank axle. Parts 11 and 6 on this diagram. Very often go AWOL on Shimano HT-II road triples
http://www.sjscycles.com/Drawings/Shima ... ch_Doc.pdf

EDIT - probably not as you have too little axle

You only need the spacers if you're using a MTB bottom bracket - 1 on the drive side if it's a 73mm shell. 2 on the drive side and 1 on the non-drive if it's 68mm. I'm not sure if you can make up a functional road BB from MTB BB parts or vice versa.

EDIT - check you've got a road BB, not mountain. Get rid of the spacer if you've got a road BB, get a road BB if you've got a mountain BB.

[keyboardmonkey]

Hi
I'm fitting [or trying to fit] a Tiagra Triple Road chainset to a Harry Hall frame using a Hollow tech BB...
Jim.

As mentioned it's worth double checking on the external BB that you have. IIRC I had to buy the BB separately from the chain set. (My Deore chainset came complete with a BB.)

[Brucey]

in Shimano HT-II BBs, the 'Mountain' cups each protrude ~1mm less than the 'Road' cups from the frame, making an assembly that is up to 2mm narrower and/or allows a 2mm adjustment range of chainline. Whilst a Tiagra chainset should fit to a road frame with a 68mm shell with a 'road' BB (with no spacers), it can be prudent to use a 'Mountain' BB and a few spacers to get the chainline spot on.

'Mountain' cups are ~10.3mm thickness and 'Road' cups are ~11.3mm thickness

Also be sure that there is not an unnecessary/wrongly placed spacer on the RH end of spindle before the chainset is fitted. This could be your issue as it might explain both things you are seeing, i.e. that the chainline is hopeless and the LH crank won't fit.

cheers

[AndyA]

Maybe there's some corrosion or damage on the axle preventing you getting the axle in fully. Check for a gap at the axle - sometimes you have to hit the crank with a rubber mallet to get it home.

[bigjim]

Maybe there's some corrosion or damage on the axle preventing you getting the axle in fully. Check for a gap at the axle - sometimes you have to hit the crank with a rubber mallet to get it home.

Just a note to thank everybody and say I have appeared to fix it. My poor eyesight stopped me from seeing the rough edges on the face of the BB where the LBS had damaged the frame. My finger felt the protuding steel though so I got a broad file plus spirit level and spent some time gently smoothing the area down to a flat surface on the drive side. I then reinstalled the cup, needed a bit of force to get it snug to the frame, but with the help of some grease and a rubber mallet the spindle went through and enabled me to install the crank properly.

[Spinners]

Note to self: Must buy a rubber mallet.