Hollowtech II pre tension bolt...badly worn!!!

John D · Post by **John D** » 21 Aug 2014 09:45

Need to change my bottom bracket. Have got the bottom bracket tool and a shimano pre tension bolt tool (the one that has a small plastic thumb wheel to tighten hand tight). However the plastic bolt has been installed by the previous owner of the bike far too tight, in effect virtually stripping the bolt head meaning the special tool will not engage. Before I start completely butchering the bolt (thinking of fine drilling a couple of off centre holes to enable screwdrivers or similar to create some torque to a turning motion or creating a "slot" in the centre ), was wondering if I'm going to make a bad situation worse ( guess I only run the risk of damaging crank arms or the crank arm spindle ) or has anyone else encountered a similar problem and how was it was resolved. Had a quick "google" without much success.

Pedlo Mudguardo · Post by **Pedlo Mudguardo** » 21 Aug 2014 11:12

As far as I'm aware the plastic bolt should only be finger tight. Make sure you've completely removed the two crank bolts and the safety washer before attempting removal of the plastic part. If you still can't remove it once you've done that perhaps try a sharp flat edge screw driver or small chisel and gently tap the plastic bolt anti-clockwise.

You could also try heating it with a hair dryer which can sometimes help to free it up.

Replacement parts are easily obtainable from the usual websites or your friendly bike shop for less than £5.

Good luck, hope that helps.

petemarshall · Post by **petemarshall** » 21 Aug 2014 11:19

It's only a soft plastic bolt, designed so it can't be tightened up too much! Unfortunately this doesn't seem to stop people trying. They usually do this, crushing the bearings and then complain about the poor quality of Shimano manufacturing. Your is a classic case. I would check that the same hasn't been done with the headset as well as he sort of person who overtightened the crank pre load is going to do the same to the headset bolt. Didn't have a chance to check it when you came round.

By the way I did remember the book I would recommend, it is Zinn & the Art of Road Bike Maintenance, not as entertaining as my copy of Richards bicycle book, but does cover stuff made in this century.

I would remove the two retaining bolt from the crank and then just try a couple of hammer blows (plastic hammer) on the crank to get it off then drill into the plastic bolt to make a couple of small holes so I could get purchase to remove it, but however you do it you are going to have to get a new one and a new bottom bracket.

When replacing, put the crank on and snug it up to the BB, then tighten it by hand and then back it off and re-tighten to it is snug. Then tighten the retaining bolts to about 14ftlbs. Check that these bolts are still tight after a couple of hundred kms and that's about it. The preload should not really ever need tightening again unless you remove the cranks. Shimano external BB's are not serviceable. Ridden in all weathers an Ultegra one will last 10,000 + kms at least, but you can get Hope ones that cost about twice as much, are serviceable and will last for ever.

John D · Post by **John D** » 21 Aug 2014 12:26

Pedlo Mudguardo wrote:As far as I'm aware the plastic bolt should only be finger tight. Make sure you've completely removed the two crank bolts and the safety washer before attempting removal of the plastic part. If you still can't remove it once you've done that perhaps try a sharp flat edge screw driver or small chisel and gently tap the plastic bolt anti-clockwise.

You could also try heating it with a hair dryer which can sometimes help to free it up.

Replacement parts are easily obtainable from the usual websites or your friendly bike shop for less than £5.

Good luck, hope that helps.

Nic, thanks for your comments and advice. will source a replacement bolt before passing the point of no return.

John D · Post by **John D** » 21 Aug 2014 12:48

petemarshall wrote:It's only a soft plastic bolt, designed so it can't be tightened up too much! Unfortunately this doesn't seem to stop people trying. They usually do this, crushing the bearings and then complain about the poor quality of Shimano manufacturing. Your is a classic case. I would check that the same hasn't been done with the headset as well as he sort of person who overtightened the crank pre load is going to do the same to the headset bolt. Didn't have a chance to check it when you came round.

By the way I did remember the book I would recommend, it is Zinn & the Art of Road Bike Maintenance, not as entertaining as my copy of Richards bicycle book, but does cover stuff made in this century.

I would remove the two retaining bolt from the crank and then just try a couple of hammer blows (plastic hammer) on the crank to get it off then drill into the plastic bolt to make a couple of small holes so I could get purchase to remove it, but however you do it you are going to have to get a new one and a new bottom bracket.

When replacing, put the crank on and snug it up to the BB, then tighten it by hand and then back it off and re-tighten to it is snug. Then tighten the retaining bolts to about 14ftlbs. Check that these bolts are still tight after a couple of hundred kms and that's about it. The preload should not really ever need tightening again unless you remove the cranks. Shimano external BB's are not serviceable. Ridden in all weathers an Ultegra one will last 10,000 + kms at least, but you can get Hope ones that cost about twice as much, are serviceable and will last for ever.

Pete, cheers, note the comments re the headset which will be addressed when I replace the stem. ultegra bottom bracket sourced via planet x for £12.99. other comments appreciated. copy of Zinn ordered through Amazon!!

regards

JD