@[mention=9180]JohnCade[/mention] Mystery solved! I emailed the Holland Bike Shop and described your observation. They replied thusly:

 

"Thank you for your e-mail. This is a new model, and this is normal. You can adjust it with a hexagonal wrench on the bolt head."

 

Which is pretty much what my bike mechanic observed when he took the part from me. By the way, the other three versions I ordered did have the adjustment bolt, as you can see from the picture.

Right, so the bolt is the same as the old type but has an Allen key recess so it can be fitted with the nut head against the frame? Or there is no nut head at all on this new one? If it's the former I suppose there would be more contact area. But the bolt dia is about the same as the dropout width so as long as it lines up maybe not.

 

Think I prefer adjusting with a nut. But I did think about finding a way to make the frame contact end a bit bigger to spread the load at first. Then I thought it wasn't really necessary.

 

Anyway as long as it does the job and there is some way of adjusting it that's all the matters. I'm having to adjust for chain wear every few hundred miles. So I don't suppose you are going to get the bike shop to do it every time.

@[mention=9180]JohnCade[/mention] It's the latter. There is no nut head/adjustment bolt on the bolt/screw, so none that that is tightened against the dropout to spread the load. However, the bolt is nowhere near as wide as the dropout. I'm attaching some pictures of how the bolt is contacting the dropout - on each side. You can also see the indentation for the Allen key.

 

This issue of the bolt thickness is part of why I wondered whether the larger chain tensioners might be a better solution, as their bolts might be more substantial. However, from a quick look, all the sizes seem to use a common bolt thickness.

 

On the issue of future adjustments, I have no experience doing this. When do you tighten the tensioners and by how much? No, I don't suppose I'd want to get the bike shop to do it every time, but I'd like to know what I'm doing, given my history of problems with Kalkhoff e-bikes.

 

On an earlier point, yes, I agree, the P&P was extortionate (9 euros 50 as I recall) if you were only ordering something small. But you could save by ordering more.

 

@[mention=9180]JohnCade[/mention]

 

On the issue of future adjustments, I have no experience doing this. When do you tighten the tensioners and by how much? No, I don't suppose I'd want to get the bike shop to do it every time, but I'd like to know what I'm doing, given my history of problems with Kalkhoff e-bikes.

 

On an earlier point, yes, I agree, the P&P was extortionate (9 euros 50 as I recall) if you were only ordering something small. But you could save by ordering more.

 

[ATTACH=full]10108[/ATTACH] [ATTACH=full]10109[/ATTACH]

 

You just need to slacken off the wheel nuts and turn both the adjusters clockwise an eighth of a turn at a time to move the axle backwards evenly until the chain is at the right tension. 1 to 1.5 cm vertical movement in the middle of the bottom run at the chain's tightest position on the sprockets. Then tighten the wheel nuts.

 

Since the wheel is also being held by the tensioners as well as the nuts the torque is not so crucial. So as you don't have a torque wrench just pull them up tight but not as hard as you can. I tighten to 25 ft/lbs and the way I always used to judge torque years ago before I bought a T/W was to estimate the length of the spanner, and if its say 6" and you want 25 ft/lbs then imagine you are pulling 50 lbs. Ideally you want a foot long one and can then imagine 25 lbs. If you pick something weighing that up you can judge it fairly well.

 

But as long as you pinch them up well and don't over tighten it will be fine.