Steady but then FIERCE braking TR3A

[Martin V]

My TR3A came to me with “strong” brakes and the elderly owned said “watch out as they are a bit fierce”.

They are disc front / drum rear. All brake pads etc look excellent and have done only 1500 since restoration 10 years ago.

They do have a servo added to the system which is a common addition and routine for the restorer.

The brakes are great with good feel initially and better than my GT6 but if I get the pressure just a tad too much with the right foot it will stop on the spot! This is harder to avoid coming to a roundabout from above 50mph when changing down and moderating braking.

The brakes are on the shared clutch/brake (Girling) reservoir system.

I’m thinking to drain the fluid (Dot 4) blow it all through, rinse and fill with Dot 5 Silicone fluid as is in my GT6. I’ve read chats on this topic on TSSC and it seems there is much myth. Everything is most likely 10 years old although the dot4 may have been replaced a couple of years ago when it was last recommissioned by the restorer.

Anything I should check? / do?

[johny]

I would check the boost ratio of the servo thats been fitted and if the recommended one suspect that it has a problem...

[Martin V]

35 minutes ago, johny said:

I would check the boost ratio of the servo thats been fitted and if the recommended one suspect that it has a problem...

Is it easy to identify the ratio?

[johny]

Unless its labelled probably not, maybe its dimensions might give a clue or a serial number that could be checked with the manufacturer.

Boosts seem to go 1 to 1.65, 1.9 or 3 with the last being too much for your car...

[Martin V]

16 minutes ago, johny said:

Unless its labelled probably not, maybe its dimensions might give a clue or a serial number that could be checked with the manufacturer.

Boosts seem to go 1 to 1.65, 1.9 or 3 with the last being too much for your car...

Thanks Johny. I’ll see what I can see.

[johny]

Im leaning more to a servo problem though, as whichever boost you have it should be proportional....

[Pete Lewis]

sounds like it is over servo'd    and Dot4 absorbs  moisture like a sponge regardless of usage  its the reservoir breathing changes in atmospheric pressure  and the rise and  fall in levels as you use it  ,that the culprit  and the normal to stay safe is replace every 2 years 

Pete

[johny]

Looks like a 1.9 boost servo is recommended for your car (and most others as well) but the level is determined by the bore of its hydraulic piston so difficult to know. If you do have the correct unit you could, with the engine running, listen for a leak at the air valve. You might need a pipe in your ear but any hissing from it could explain too much braking force as the air valve is operated...

[Martin V]

On 14/10/2024 at 08:35, johny said:

Looks like a 1.9 boost servo is recommended for your car (and most others as well) but the level is determined by the bore of its hydraulic piston so difficult to know. If you do have the correct unit you could, with the engine running, listen for a leak at the air valve. You might need a pipe in your ear but any hissing from it could explain too much braking force as the air valve is operated...

I’ll try this as I’m quite sure that the restorer most likely used the right servo. He’s a serial restorer and apparently well known restoring TR sidescreen cars.

There is no ID on the servo body of any kind.

I think I’ll recruit my friend for a fluid change and most likely switch to silicone Dot 5 based fluid after a blow through and see how it feels then.

[RedRooster]

Send it to these guys, I've used them a few times now. 

http://jlspares.com/companyprofile.htm