Right, those of you who will have worked on braking systems will recognise the picture.
The Calliper is held to the sliding pins in the mounting bracket using, typically, bolts with a 13mm head (sometimes less sometimes more)
The Sliding pins, again typically, have a hex machined into them such that a 15mm (Again, sometimes another size) open ended spanner can be used to stop them from rotating when you are undoing the calliper bolts.
With me so far?
Now, Here's the thing.
Firstly, The 13mm bolts...
The 13mm bolts sometimes (not always) have bolt heads that are "Half Height".
This means, that when the chamfer on the inside of the typical ring spanner is taken into consideration, the actual ring spanner part ends up engaging with only about a mm or two of bolt head right near the top!
As a result of this, if the bolt is at all tight (Due to either corrosion or an overenthusiastic use of thread locking compound) there is a very real risk of rounding the corners off!
So, Question #1. Why do they do that?? I have never seen "Half height" bolt heads anywhere else! I cannot think of any engineering reason why something like this should be used (Especially since it isn't always used) and I have only ever come across one example where clearance issues might actually be a problem (In the vast majority of cases there are no clearance issues at all!)
Secondly, the hexes on the sliding pins.
The width of the hex (Bounded by the calliper itself and the shoulder up against which the rubber boot is retained) is frequently slightly narrower than the thickness of the standard spanner head. (Which can make the job somewhat awkward if the bolts are tight on the way out (Threadlocker again) until they have been unwound enough to get a spanner in)
So, Question #2) Why do they do that, there is typically only a mm or so in it. What is the engineering reason for making these hexes slightly narrower than the standard spanner
In both cases it is of course possible to modify existing tools with a grinder to improve the fit of the ring spanner onto the bolt heads by removing the chamfered section and to grind down the spanner head to make it narrower so it will fit on the sliding pins hexes.
But I have never seen tools sold like this as "Special tools for brake work"? and it seems bizarre to have to modify standard tools in order to make routine jobs possible.
So is there anybody in the motor manufacturing/design business here that can explain the reasoning behind all this??
.
The Calliper is held to the sliding pins in the mounting bracket using, typically, bolts with a 13mm head (sometimes less sometimes more)
The Sliding pins, again typically, have a hex machined into them such that a 15mm (Again, sometimes another size) open ended spanner can be used to stop them from rotating when you are undoing the calliper bolts.
With me so far?
Now, Here's the thing.
Firstly, The 13mm bolts...
The 13mm bolts sometimes (not always) have bolt heads that are "Half Height".
This means, that when the chamfer on the inside of the typical ring spanner is taken into consideration, the actual ring spanner part ends up engaging with only about a mm or two of bolt head right near the top!
As a result of this, if the bolt is at all tight (Due to either corrosion or an overenthusiastic use of thread locking compound) there is a very real risk of rounding the corners off!
So, Question #1. Why do they do that?? I have never seen "Half height" bolt heads anywhere else! I cannot think of any engineering reason why something like this should be used (Especially since it isn't always used) and I have only ever come across one example where clearance issues might actually be a problem (In the vast majority of cases there are no clearance issues at all!)
Secondly, the hexes on the sliding pins.
The width of the hex (Bounded by the calliper itself and the shoulder up against which the rubber boot is retained) is frequently slightly narrower than the thickness of the standard spanner head. (Which can make the job somewhat awkward if the bolts are tight on the way out (Threadlocker again) until they have been unwound enough to get a spanner in)
So, Question #2) Why do they do that, there is typically only a mm or so in it. What is the engineering reason for making these hexes slightly narrower than the standard spanner
In both cases it is of course possible to modify existing tools with a grinder to improve the fit of the ring spanner onto the bolt heads by removing the chamfered section and to grind down the spanner head to make it narrower so it will fit on the sliding pins hexes.
But I have never seen tools sold like this as "Special tools for brake work"? and it seems bizarre to have to modify standard tools in order to make routine jobs possible.
So is there anybody in the motor manufacturing/design business here that can explain the reasoning behind all this??
.
