Classic cars forum & vehicle restoration.
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ka
Joined: 03 Dec 2007 Posts: 600 Location: Orkney.
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Posted: Wed Sep 25, 2013 7:56 am Post subject: Twin Leading Shoes |
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To cut a long story short, I am upgrading from SLS to TLS. I have looked at many pictures of TLS set-ups, but they all seem to differ.
The shoes I am using have an 'offset' lining, ie, it is nearer one end of the shoe than the other. I have looked at the logic of mounting shoes both ways round, lining closer to end of shoe nearer the wheel cylinder, and vice-versa.
Any one any advice? _________________ KA
Better three than four. |
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V8 Nutter
Joined: 27 Aug 2012 Posts: 587
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Posted: Thu Sep 26, 2013 8:26 pm Post subject: |
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I don't know but I would have thought there was a lot more to it than just changing the shoes. |
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Roger-hatchy
Joined: 07 Dec 2007 Posts: 2135 Location: Tiptree, Essex
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Posted: Thu Sep 26, 2013 9:31 pm Post subject: |
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Twin leading shoes should have a moving piston at the leading end of each shoe, IE A single pistong either side of the set up, one for each lead.
As to the lining further back from the leading edge, I think it is to do with leverage and travel.
All brake shoes I have ever seen, Both SLS and TLS, have the lining toward the rear of the shoe away from the rotation.
Someone with a bit more technical knowledge should have a better answer |
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Jim.Walker
Joined: 27 Dec 2008 Posts: 1229 Location: Chesterfield
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Posted: Wed Oct 02, 2013 8:55 am Post subject: |
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Over years I have thought long and hard about lining position relative to actuating pistons and have even, without success, searched technical literature for the answer.
It does not help that Manuals illustrations differ from car to car.
However. In my mind it stands to reason that the lining will wear most on the end closest to the pivot and moving the lining closer to the cylinder will even out the wear pattern.
Also, the closer the lining contact with the drum is to the cylinder the greater will be the servo (leading shoe) action.
Very simply, the greatest "leading shoe" effect will occur where the greatest (tangential) friction is furthest away from the pivot. Like pushing on a longer lever.
I realise this does not answer your question and I might have completely overlooked other arguments.
I have never been very happy with this topic.
Jim. _________________ Quote from my late Dad:- You only need a woman and a car and you have all the problems you
are ever likely to want". Computers had not been invented then! |
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Jim.Walker
Joined: 27 Dec 2008 Posts: 1229 Location: Chesterfield
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Posted: Wed Oct 02, 2013 8:56 am Post subject: |
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Over years I have thought long and hard about lining position relative to actuating pistons and have even, without success, searched technical literature for the answer.
It does not help that Manuals illustrations differ from car to car.
However. In my mind it stands to reason that the lining will wear most on the end closest to the pivot and moving the lining closer to the cylinder will even out the wear pattern.
Also, the closer the lining contact with the drum is to the cylinder the greater will be the servo (leading shoe) action.
Very simply, the greatest "leading shoe" effect will occur where the greatest (tangential) friction is furthest away from the pivot. Like pushing on a longer lever.
I realise this does not answer your question and I might have completely overlooked other arguments.
I have never been very happy with this topic.
Jim. _________________ Quote from my late Dad:- You only need a woman and a car and you have all the problems you
are ever likely to want". Computers had not been invented then! |
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ka
Joined: 03 Dec 2007 Posts: 600 Location: Orkney.
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Posted: Thu Oct 03, 2013 7:31 am Post subject: TLS |
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The more you think about the logic of the leading edge, trailing edge, the more you get confused.
I have looked on web sites, and handbooks and they all differ. To try and get a definitive answer I have done two things,
Took the TLS brake to bits on my motorbike, looked at a Minor 1000 brakes with the drum off.
These both at least agreed.
The shoe has an metal base, and a lining (mine are the devil word 'asbestos') riveted together. The lining is mounted off centre, ie it is nearer the end of the metal base to one end than the other. Both the examples I have looked at have the gap between the metal base, and the lining at the wheel cylinder piston end, with the shoe/metal base/no gap at the pivot end.
I will find out soon as I have one 99% complete, ready to start on the other. _________________ KA
Better three than four. |
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jessejazza
Joined: 18 Mar 2009 Posts: 75
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Posted: Fri Dec 20, 2013 11:02 pm Post subject: |
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Roger-hatchy wrote: | Twin leading shoes should have a moving piston at the leading end of each shoe, IE A single pistong either side of the set up, one for each lead.
As to the lining further back from the leading edge, I think it is to do with leverage and travel.
All brake shoes I have ever seen, Both SLS and TLS, have the lining toward the rear of the shoe away from the rotation.
Someone with a bit more technical knowledge should have a better answer |
I agree... and like yourself I have not found an answer over twenty years or so of working on cars. However, if you have the lining to the front with rotation the shoes tend to bind... it just isn't right somehow. |
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jessejazza
Joined: 18 Mar 2009 Posts: 75
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Posted: Fri Dec 20, 2013 11:12 pm Post subject: Re: Twin Leading Shoes |
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ka wrote: | To cut a long story short, I am upgrading from SLS to TLS... |
What vehicle is this for? I'm wondering if it's a series landrover. There aren't that many vehicles that can facilitate such an upgrade. It is common on landrover SWB to do this mod which has 10" SLS on the front. The backplate for a LWB is used for 11" SLS or straight swap front 11" TLS from LWB. The servo effect that one will gain with TLS is marginal I am told.
I have a SWB and a LWB for restoration. The SWB is to be used as a tow vehicle and so I am removing the 10" and replacing with 11" SLS and servo. Reason for my decision is that the SLS are easier to adjust. The adjusters on TLS vary and on landrovers are not so good as say a Herald (imho). The choice of lining material is key to good braking. Mintex are best and I have heard EBC be spoken well of. |
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ka
Joined: 03 Dec 2007 Posts: 600 Location: Orkney.
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Posted: Sat Dec 21, 2013 9:06 am Post subject: |
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The brakes are for a Three-wheeled Morgan, a later one where the front wheels only are braked (hand-lever only for the back wheel)
I upgraded the brakes from rod to SLS hydraulic 10 years ago (TLS was not an option at the time, for reasons too long to go into), but now these reasons are not prevalent, so TLS beckoned.
I have now completed the work, and placed the shoes as shown in the Morris handbook, ie, the lining is biased towards the fixed pivot point giving the necessary servo effect when the brakes are applied.
All is well in the Morgan camp, smooth, light progressive brakes, they are still limited by the grip that the skinny motorcycle tyres provide, but at least I can now feel that point.
I can explain how to do it if there are any other obsessives out there!! _________________ KA
Better three than four. |
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ka
Joined: 03 Dec 2007 Posts: 600 Location: Orkney.
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Posted: Sat Dec 21, 2013 9:16 am Post subject: |
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Twin leading shoes should have a moving piston at the leading end of each shoe, IE A single pistong either side of the set up, one for each lead.
As to the lining further back from the leading edge, I think it is to do with leverage and travel.
All brake shoes I have ever seen, Both SLS and TLS, have the lining toward the rear of the shoe away from the rotation.
The leading edge (the end of the shoe where the lining has a space) should be next to the wheel cylinder, even for SLS where both chamfered edged (leading edges) should surround the wheel cylinder. This gives braking when reversing due to reversed shoe and the servo effect.[/i] _________________ KA
Better three than four. |
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jessejazza
Joined: 18 Mar 2009 Posts: 75
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Posted: Sat Dec 21, 2013 11:56 am Post subject: |
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I would be interested to hear how much better it is than SLS when you've been out on the road. I was thinking of SLS for the landrover simply because it is easier to adjust - TLS on a landy is a more lengthy exercise adjusting due to the weight of the vehicle and the poor design on the adjusters compared with say a Herald design. |
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ka
Joined: 03 Dec 2007 Posts: 600 Location: Orkney.
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Posted: Sun Dec 22, 2013 7:17 pm Post subject: |
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Instead of a left foot assisted braking, the brakes are light and progressive, with far more pedal movement. _________________ KA
Better three than four. |
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