Volvo Servo Upgrade

[Z320]

Hi Tony,

btw a noticable improvement is already to use a 0.625" master for the cluch.

I did this before on my 4A, a friend of mine does this on his TR6 on my recommendation, also another mate here at the forum.

The TR6 clutch sometimes has some problems, to get the 0.625" master work you have to make shure to have the max way of travel and only a minimum play.

An adjustable push rod could be needed (my TR6 friend uses one, simple to make).

Ciao, Marco 

Edited November 17, 2021 by Z320
my poor english writing

[harrytr5]

3 hours ago, Tony M said:

Hi Harry. Thanks.  I agree that the picture shown on the advert doesn't show a threaded rod for the clevis pin clamp, but I ordered that and it came with the threaded end. At the point of ordering I didn't really consider that there might be a problem with the length or adjustment. I was looking for the part number 9157699 and took a chance.

 In the pictures I show a closeup of the clevis bracket held in the vice before I used a junior hacksaw to cut along the 2 welds that held the silver nut on. I then adjusted the thinner bronze lock nut by filing 2 edges, so that it would slide inside the bracket and the two nuts could then be set anywhere to alter the length and rotational position of the bracket. I had to shorten the shaft a bit to get the position I needed.

Regards

Tony

Many thanks Tony and now it is a lot clearer. A picture paints a thousand words!

Regards Harry

[Tim D.]

I'm the guy who changed to a 0.625" master to the clutch. Works Nicely.. but you have to add an adjustable pushrod to the master and it means the clutch pedal is a little higher.. but we used it for the 2000 miles of the RBRR with no issues. Has the advantage of much improved clutch control when crawling in traffic!

Tim

[harrytr5]

Now ordered and will copy your's Tony.

Great article I must say. Due to EFI and airbox  being in very close approximity I hope I get away with it (the tape measure says yes but it is tight) we will see. Nothing ventured nothing gained and all that. If it does not fit then will be up for sale(the servo that is).

Regards Harry

Edited November 18, 2021 by harrytr5

[Rob Y]

I was talking with some guys at my local group yesterday and there was a feeling that changing the break calliper to a 2 pot (or is it 4 pot) was a better upgrade compared to changing the servo.

What are the opinions on this forum?

Maybe an easier mod, less modification required but only improves the front brakes.

I look forward to hearing your thoughts. I’m really interested in this servo mod, but I wouldn’t be able to do the machining if the spacer myself.

Cheers, Rob

[Z320]

It is very hard to find caliper with more piston surface than the original Girlings!

I know only one model out there slightly with more surface, new on the market a „short time“.

With less piston surface the force and braking is less, independent from the number of pistons.

Please allow me to say there is a „sadisfaction“ called „cognitive dissonance reduction“,

not easy to realize it on yourself because not to realize it is part of the „disease“.

Ciao, Marco

Edited November 18, 2021 by Z320

[RobH]

As Marco says, 4-pots  are not really an upgrade if the pad area isn't increased also, and 4-pots and servos are really addressing different requirements.  4-pots with a smaller piston area and larger pads will actually increase the required pedal pressure whereas a servo is used to decrease it. 

 These cars do not 'need' 4-pots for effective braking on the road, but decent pads can make all the difference. 

 

 

[FatJon]

3 minutes ago, Z320 said:

It is very hard to find caliper with more piston surface than the original Girlings!

I know only one model out there, new on the market a „short time“.

With less piston surface the force and braking is less, independent from the number of pistons.

Please allow me to say there is a „sadisfaction“ called „cognitive dissonance reduction“, not easy to realize by yourself.

Ciao, Marco

Correct. The purpose of 4 (or more) pistons in a caliper is to reduce the heat loading per unit area on the pad surface. You are correct that the braking force is the same if the total piston area is the same but a larger PAD contact area is useful to prevent fade and aid heat dissipation. With the AP 4 pots I calculated the piston area was around 24% larger so only a marginal increase in braking force but the pad area increase is very much more than that, which is more important for track use. I think you would need to be driving very badly to benefit from that extra heat capacity on the public road but extra brake force both from the calipers and a more modern servo is very welcome. My car has AP 4 pot calipers and bigger drums. The AP brakes with the original servo were very marginally more powerful than original but still rubbish by modern standards. Yes it was possible to lock the wheels with a hefty push of the pedal but I don't want to push the pedal through the floor to make an emergency stop and my wife couldn't even if she tried. She's accustomed to a modern Maserati which has a very light pedal and to go from that car to a TR6 is quite frightening in many ways. To go from a 1.8T cruiser with an automatic gearbox, power steering, active suspension and feather light brakes to a TR6 is a big ask. The lightness and instant bite of this servo update is the real beauty. I guess it's a little like power steering. Yes, you can still turn a corner without it but why bother when it exists? Even without he PAS and automatic box I have removed at least one barrier to my getting home from the pub without a belly full of lemonade.

[Tim D.]

Again this is all to do with how you use your car and to a certain extent your driving style.

If you drive at 10 10ths all the time using full "anchors" in all situations then more cooling or harder pads would probably help. You may also want to look at your tyre technology as well.

If you are more of a cruiser and like more sensitivity or a lighter pedal then either increase the friction of the pads or increase servo assistance.

In my ten years with the TR I have only worried about my brakes twice.. driving down from the Gross-Glockner pass in a "spirited" fasion and noticing smoking brakes when I stopped for fuel at the bottom (no fade on the mintex 1144 pads I had) and after 5 track laps around Spa (greenstuff pads) and no brakes at the end... Mind the two TR4s in front of me, which were in much better condition than my car at the time, also had no brakes, and one had no oil pressure on a newly rebuilt engine..

Cheers

Tim

 

[stuart]

6 minutes ago, Tim D. said:

Again this is all to do with how you use your car and to a certain extent your driving style.

If you drive at 10 10ths all the time using full "anchors" in all situations then more cooling or harder pads would probably help. You may also want to look at your tyre technology as well.

If you are more of a cruiser and like more sensitivity or a lighter pedal then either increase the friction of the pads or increase servo assistance.

In my ten years with the TR I have only worried about my brakes twice.. driving down from the Gross-Glockner pass in a "spirited" fasion and noticing smoking brakes when I stopped for fuel at the bottom (no fade on the mintex 1144 pads I had) and after 5 track laps around Spa (greenstuff pads) and no brakes at the end... Mind the two TR4s in front of me, which were in much better condition than my car at the time, also had no brakes, and one had no oil pressure on a newly rebuilt engine..

Cheers

Tim

 

Also for those of us of a certain age who grew up with cars (and lorries) that never had any decent brakes anyway and tend to use the engine braking by using the gearbox should pass that knowledge on

Stuart.

[Tim D.]

13 minutes ago, stuart said:

Also for those of us of a certain age who grew up with cars (and lorries) that never had any decent brakes anyway and tend to use the engine braking by using the gearbox should pass that knowledge on

Stuart.

:-).. Yes, Absolutely Stuart.. My smoking brakes on the Gross-Glokner were partly due to forgetting this, whoops !

[Waldi]

Is there objective data (tests) available for comparison of different brake pads?

Cheers,

Waldi

[Tim D.]

2 hours ago, Waldi said:

Is there objective data (tests) available for comparison of different brake pads?

Cheers,

Waldi

You can find some tests online of friction vs brake temp. but generally these do not compare the pads we mostly use against each other.

There is an interesting graph showing Hawk pad performance

 

 

and another separate one showing Greenstuff 

 

similar data for ferodo

[Z320]

Hi,

I use a pair of the cheapest brake pads from a common supplier on my TR4A and I'm pleased with the result, not impressive, but well pleased.

But this post reminded me I have a set of Mintex 1144 brake pads in my workshop (!) to test and compare - 5 times more expensive for me at Germany than the standard ones!

So I just hurried in my workshp to look for them and have them ready to fit! And - in the box - I found the already used standard ones!!!!

@§$"!!9?@ the Mintex 1144 are already on the car!

Edited November 18, 2021 by Z320

[Waldi]

Thanks Tim for collecting the data!

The graphs show (to me, far far from an expert) there is not a "huge" (like 50%) difference between the 3 suppliers for similar types of pads.

But selecting the wrong type of pad is. Like using EBC's Greenstuff for race track days; here the difference becomes more pronounced, "Green" being up to a factor 2 lower than the "Yellow", just as an example.

My TR6 is mainly used for normal touring (but I like some spirited driving every now and then, but never long), so I guess my pads will not reach temperatures beyond 300 degr.C for most of their use. I have measured my front disk temperatures in summer conditions after some driving/braking, they never exceeded 300 C. I realize that pad temperatures may be higher but these are difficult to measure for the hobbyist.
So "standard grade" pads are the obvious choice for me.

Assuming the vendor data are correct and comparable (friction also depends on the disk material and surface profile):
EBC shows some 20% difference in their range for my use (I have Greenstuff in the front side, rear shoes are "standard, not specified".
Ferrodo shows a spread of only 15% in coëfficiënt of friction between their listed pads.

Hawk green and black apperar to be slightly better (black only after being warmed up).

I hope other more seasoned TR-ers can provide a better insight than my simple analysis above.
I stand to be corrected.

Cheers,
Waldi
 

[Tony M]

22 hours ago, Rob Y said:

I was talking with some guys at my local group yesterday and there was a feeling that changing the break calliper to a 2 pot (or is it 4 pot) was a better upgrade compared to changing the servo.

What are the opinions on this forum?

Maybe an easier mod, less modification required but only improves the front brakes.

I look forward to hearing your thoughts. I’m really interested in this servo mod, but I wouldn’t be able to do the machining if the spacer myself.

Cheers, Rob

Hi Rob. Last year I changed mine from original 2 pot to the BCC 4 pot with new drilled discs. Yes it did improve things but I still wanted more gain from the servo. I cant tell you what improvement this servo upgrade will give on standard brakes though. Front end upgrade was approx £800 and took me quite a while . This servo was easy in comparison and much cheaper.

[KiwiTR6]

Mintex 1144 

[harrytr5]

I have followed the instructions and about to install my Volvo servo. Looking forward to feeling it in action.

Regards Harry

[harrytr5]

I fully endorse those that have converted to the Volvo servo. Just love it.

Thanks to the initialiser.

Regards Harry

[Rob Y]

I’ve finally got my servo after the on-line order got lost in their system and I’ve also got the spacer made, so I’m ready to make the installation.

 I notice from the thread that the rod from the servo that goes into the master cylinder needs shortening slightly. Can the same thing be achieved by putting a spacer between the master cylinder and the servo or am I missing something?

(by the way I have a 3D cad file available for the spacer if needed, this can be used to machine the part on a cnc  machine) I used the file to 3D print a part to check the fit on the servo, and for a bit of fun.

Cheers Rob

[FatJon]

18 hours ago, Rob Y said:

I’ve finally got my servo after the on-line order got lost in their system and I’ve also got the spacer made, so I’m ready to make the installation.

 I notice from the thread that the rod from the servo that goes into the master cylinder needs shortening slightly. Can the same thing be achieved by putting a spacer between the master cylinder and the servo or am I missing something?

(by the way I have a 3D cad file available for the spacer if needed, this can be used to machine the part on a cnc  machine) I used the file to 3D print a part to check the fit on the servo, and for a bit of fun.

Cheers Rob

You can thin the lock washer a little or shorten the rod or use a spacer. All will work just fine. We are talking <3mm.

[Rob Y]

On 2/11/2022 at 9:21 AM, FatJon said:

You can thin the lock washer a little or shorten the rod or use a spacer. All will work just fine. We are talking <3mm.

Sorry to sound stupid but how do you thin the lock washer? I see on this rod there is a small nut halfway along it. What does this actually do? If I unscrew it does half the rod come off so it can be shortened on a bench, out of the servo or………? I’m a bit worried that the other half will somehow disappear inside the servo.

[FatJon]

It's a locknut so you can adjust the shaft sticking out of the servo a little then tighten the nut to lock it in position. In our case the shaft is a little too long even when fully shortened. If you thin the locknut by filing it a little you can screw the rod in a bit further and just make the required length. You don't really need the fancy tool but the video shows the theory. In this case you can see that the pintle sticks out of the servo a long way, not the case on a TR6. On the TR6 the stick out is very small.

 

By pushing the pedal down a little you can make the rod poke out more to make access to the adjustment easier. Not required in the application in the video but necessary on the TR6 or you can't get access to the locknut as it's slightly inside the servo in the at rest position. A spacer may be an easier option though.

 

 

[Rob Y]

Finally installed the new Volvo servo on my TR6. Installation was pretty straightforward after following the advice from this thread. Only problem was the bonnet came into contact with the master cylinder reservoir cap. Judging by the state of the paint in this area on the bonnet it looks as if this was very close before. A small bit of “adjustment” to this reinforcing part of the bonnet and now it closes fine without contact.

My god, what a transformation though!!! The braking is awesome now and I’m having to re-learn how to brake in my car again! I can’t believe any other brake mod like different pad material or 4 pot callipers can make such a dramatic improvement.

Nearly put mine and my passenger/technical assistants face through the windscreen a few times before I got the new feel for it.

I’m so happy with this.

Thank you Forum!

Cheers Rob

[FatJon]

Yup, M1144 or EBC or whatever pads will help a bit but this mod is a whole different league. I wasn’t joking when I mentioned faceprints on the windscreen. I now get in my Audi or Mrs Fatjons Ghibli and think the brakes are a bit ****.