Hi Richard, I have a drawing here in the garage will show it to you at easter time, basically you throw away the centre spacer between the bearings and make a new spacer which incorporates a shoulder each end to take the 50mm inside i.d. of the bearing, 27mm long. I cant see any reason for removing the shields and just fitting the bearigs and forget about greasing them. If later you want to remove the bearing just get a set of bearing internal pullers, pop the shield and pull one side out.
The cost save is on the price of the bearings, the down side is you need a machinist to make the spacer, If you can get the machine steel and cut it to the correct length, then supply the machinist with six of these ready to turn, It will be cheaper. I havent changed the front idler on my carriers yet but it maybe worth fitting the £5.00 50x27x110 and getting two 40x27x110 bearing and keeping the idler as original, luck would have it my work place has a couple of these sitting on the shelf waiting for a new home.
