Difficulty getting GRX chainset into Ultegra BB

Doesn’t sound right - they sometimes need a tap, but not really a whack. Is it a new frame as you might need to consider bearing alignment? Otherwise, check the diameter of the crank spindle - should be at least 0.1mm smaller than the bearing ID

Hi yes it is a new bike (jamis renegade steel gravel bike) it came factory fitted with an fsa chainset and I have removed the bb and chainset and swapped it over for GRX 600 to match the groupset.

When you say bearing alignment it is a hollowtech bbr60 bottom bracket which I though you just screw into the frame as I did to install, the bb went in fine. Could there be an issue with the alignment of the frame itself then causing this difficultly with getting the Axle through the bb shell successfully?

Could there be an issue with the alignment of the frame itself then causing this difficultly with getting the Axle through the bb shell successfully?

It's a possibility. Might be worth having it checked by a competent bike shop.

The one in previously from the factory build was 19mm axle, I guess the tolerances are different between this shimano ultegra bb hollowtech set up and the previous fsa mega exo? Very surprised about this as never had this issue before? Could the bb need facing then? Not sure whether to try and knock the chainset that is 90% through the axle back out now or leave it and see what a bike mechanic says then as if the frame may be a problem I'd rather not risk damage.

I’ve previously found FSA crank spindles to be a snug fit in Shimano HT2 BBs, but never experienced issues with Shimano crank and BB fit. I’d seek a second opinion of an experienced mechanic.

Remove the crank and the NDS (LH) cup. Push that cup onto the axle and see if it fits where it should

Remove that cup, leave it out of the frame and reinstall the crank. If the axle gets stuck in the same place then it isn't alignment, if it doesn't get stuck then get a second opinion as suggested ^^

The one in previously from the factory build was 19mm axle

But you replaced the BB yeah?

Thanks for the advice so far, I noticed the part where it is very tight is on the drive side as when going to insert the axle initially it wouldn't go through any further and when I took the chainset out it had pulled the grey bearing cover from the drove side of the bottom bracket. Now I have tapped the chainset back out but it's got 90% back out and stuck there so it seems to me there is an issue with the axle getting through the first section of the bb bearing which seems strange. Any advice on what to regarding that is it may not be alignment based on it being so tight to come in and out on the drive side entrance before it gets to even go through to the other side?

Yes I did replace the fsa bb with an ultegra bbr60 and using a grx600 hollowtech chainset. Out of ideas with it being so right at the entrance though now? 

Pictures will make it easier

Have you put the central sleeve in on the wonk

It was lined up correctly. I have now managed to remove the chainset and took the bottom bracket cups off the frame. The non drive cups fit over the axle after a decent amount of force but the drive side is the stubborn one. As soon as I went to put the chainset in when I first started the installation it felt extremely right and as result when I pulled the chainset back out it had the grey bearing cover attached to the chainset still stuck over at the point where it would slide now further down the axle. It seems the tolerance on this is too severe possibly. I am not labouring or hammering it on like it was starting to need to get it 90% of the way through so I will have to let the store know and get a replacement sorted. I have tried another bb sleeve and the chainset slid on with minimal fuss so it's definitely the bb on the drive side. A lot of labour and effort, my back isn't great now. Has anyone experienced this issue before with ultegra on grx maybe   or even other similar type set ups? I am surprised as usually my previous 20 off chainset installations have been a piece of cake. Ashame about this one. Would the facing be worth considering. I am thinking as the problem was even getting the axle started on moving tbrough suggests it's too tight there. I know it needs to be very tight but this was beyond that in my opinion.

Never experienced that with many Shimano chainsets and bbs

Me neither before. I did have a dura ace chainset that had to be lightly tapped out to remove on a cx bike a few years ago but overall I have always hand fitted them 20-30odd times with no fuss. This one felt wrong from the start but I have to establish if it is the bb or the chainset that is causing this issue.

Push the top hats out and swap over

You can then see if it's that or the axle

The XT  chaminset and BB  behaves a bit like that on my fargo.

I have assumed that there is a misalignment in the threads or it needs facing.

I underrstand that Shimanio  mount  the bearing in plaastic cups inside  metal thread in part,  and  this allow for a bit of  bending of the plaastic when one bangs then axel through. When i have taken the chainset off to  change a chain ring, it has gone back in much easier.

BB seems to last  a reasonable time.  But I woudl not fit a non Shimanio BB with out the teh pastic cups.

Had to tap in my GRX cranket in to On-one Freeranger but with  with less force.

But on my Saracen road bike the  crank set just needs a  shove with a hand to go in.

I tend to put a small smear of grease on thre axel before instaling.

are you confident that the parts are all genuine ?
I'd be fishing out the vernier caliper and checking dimensions (and hoping it's just the top-hats that are a bit thick)

Yes, thanks for the advice. I will try this again in the morning, my back and legs are done after the 2-3 hours crouched down earlier doing this. I would have used a stand but with all the heavier work it became difficult to get the chainset in (albeit only 90%) and then back out again. I will try switching the top hats also. I have tried the non drive side cup over the chainset axle and it does go on much easier than the drive side which points to that as being the culprit. I guess then it's just a case of getting a new bottom bracket and hopefully that will work easier this time but one step at a time. I will try that chainset in another bb first on another bike also to check that is fitting through ok but definitely won't be forcing it on after today's troubles.

are you confident that the parts are all genuine ?

I’d be fishing out the vernier caliper and checking dimensions (and hoping it’s just the top-hats that are a bit thick

If it is genuine then it's rare for shimano to be that far out.

How hard was if to install the bb?

Is your bb on the frame undersized? Is it possible that the steel frame has deformed the shimano bb?

I guess you won't know until you try a new bb. Make sure you put it over the cranks off the bike first to make sure it fits. If it doesn't fit when installed, remove the bb snd see if it still fits over the cranks.

Personally I'd be visiting my LBS and asking them to measure bits.

<p style="text-align: left;">Yes, i am pretty sure the components are genuine as they were bought from big reputable uk based retailers. The bb was very easy to install and the frame had previously come factory fitted with a fsa mega exo bb and chainset which came off very easily and slid out fine with minimal fuss. I did try sliding the left hand cup onto the axle with them off the frame and it went over fine. I had issues from the beginning with the right hand drive side cup, with the grey cover cap straight away getting stuck over the axle at the opening as I discovered this shortly after inserting the chainset and it not progressing through the bb.</p>
I was thinking of trying the chainset in another bike I have to see if that slides in OK as I need to confirm whether it is the bb or chainset that is causing issue. I find it hard to believe with these genuine Shimano components there would be an issue like this. I had though about the frame facing also but the fact that it was struggling to let the chainset get through the driveside axle it has made me think the grey top hat and chainset axle could be the issue in sizing?

I will try the above mentioned with another bb and also try the chainset on another bb and see if things become any clearer and as you say I may also check with a local bike shop regarding the grey top hat sleeve sizing as a final check after the ones I can do myself.

I have just tried another bottom bracket over the chainset and both cups slid over fine with a little force but not too much by hand with the bb out of the frame.

I guess this ultegra one I have I will have to contact the retailer now to explain the situation and see what they can do to resolve it. At least it appears the bottom bracket was where the issue seems to be and not with the chainset.

Update on the bb, I tried a different hollowtech 2 bottom bracket and the chainset slid on pretty easily, still had to push it in with force but by hand and was very quick. The effort yesterday was too much so at least I know there is no issue with the frame or chainset and that the bb was the issue.