Brakes questions

[pupinabox]

My conversion is about 95% done, WooHoo!!! I will be posting some pictures this weekend. Anyway, I have a couple questions about the brakes.

I replaced the shoes, pads, cylinders, and lines. When I went on a short shakedown cruise yesterday, I noticed that the brakes might be a little spongy. I bled the brakes, but maybe with everything being replaced, it may need bled again after it sat awhile?

The other question is, are the vacuum assist units the same in the 7 as in the 8? just wondering if this may have something to do with it. Also, I remember somebody posting a simple way to test if the vacuum assist is working but the search function does not find anything. Anybody remember or familiar with this?

[IMG=left]http://i160.photobucket.com/albums/t194/pupinabox/353.jpg[/IMG=left][IMG=right]http://i160.photobucket.com/albums/t194/pupinabox/tr7005.jpg?t=1271517043[/IMG=right]

[Hasbeen]

Hi Pup, I have always found the 7 brakes take 2 or 3 bleedings, with the car driven between each bleeding, to get them up nice & hard.

This is the case with my 7, & 8. The 7s are stock, with good pads, the 8s are uprated with a big booster, & master cylinder, 4 pot front, & single pot discs on the back, so not much stock. I think it must have something to do with how the lines are run, & the distribution/proportioning valve.

To test your booster, get in the car, with the engine off, & apply the brakes firmly in the normal way, but NOT pumped up. Now start the engine.

If the booster is working you will feel the pedal sink towards the floor, quite a reasonable distance.

Hasbeen

[busheytrader]

Hi Pup,

Did you fit bigger front brake calipers to your conversion? If so, are you experiencing spongey brakes or longer pedal travel? Bigger calipers provide more braking but require more fluid to apply them = more pedal travel with the same master brake cylinder. The amount will depend on the brakes you fitted.

I fitted the S&S uprated front brake kit as used on the UK Ford Capri but was never comfortable with the slightly extended pedal travel. I fitted an uprated master cylinder / servo combo (which has greater fluid capacity in the pedal stroke) and the pedal travel reduced to a more comfortable level.

Hope this helps,

Adam



TR7 V8 DHC Jaguar Solent Blue. 9.35cr Range Rover V8, Holley 390cfm, JWR Dual Port, 214 Cam, Lumention, Tubular Manifolds, S/S Single Pipe Exh, 3.08 Rear, 200lb Spax & PolyBushes all round, Anti- Dive, Strut-Top Roller Bearings, Capri Vented Discs & Calipers, Braided Hoses, 4 Speed Rear Cylinders, Uprated Master Cylinder & Servo, AT 14" 5 Spokes or Maestro Turbo 15" Alloys, Cruise Lights, S/S Heater Pipes, Replacement Fuel Tank. No Door Stickers. Mine since July 1986, V8 from 1991

[TR Tony]

<blockquote id="quote"><font size="1" face="Century Gothic, Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by pupinabox</i>


The other question is, are the vacuum assist units the same in the 7 as in the 8? just wondering if this may have something to do with it.<hr height="1" noshade id="quote"></font id="quote"></blockquote id="quote">

The genuine TR8 servo vacuum unit is different to the 7 unit i.e. bigger! It looks remarkably like the Rover SD1 unit in fact. I think the master cylinder is different too. Not many of them about though, but servo/master cylinder rebuild kits are available.

Or as mentioned there are alternative servo/master cylinder set ups available from the specialists which do the same job.

Tony

<font size="1">1981 2L FHC Cavalry Blue
1980 3.5L V8 DHC Jaguar Regency Red - sadly sold!
1977 TR8 FHC EFI Factory development car Inca Yellow</font id="size1">

[andyf]

It could also be that the new brakes need a few hundred miles to bed in. It`s not unusual for the brakes to feel less sharp initially after replacements have been fitted.


1980 Persian Aqua DHC

[pupinabox]

I am pretty sure that the 7 had uprated calipers that the PO put on. The servo unit and master cylinder look the same, so I left the one in the 7 that I am converting because it looks much nicer as the PO of the 8 re-sprayed the car at some point and decided that alot of stuff could be painted along with the body, i.e. the servo and master cylinder[xx(].

Thwe reason I asked about this was that I was moving along pretty good and was about to miss my turn off so I pushed the brakes pretty hard and they did not seem to respond real "crisp". I assume that it is possible to lock the brakes up if you tromp on them hard enough since this is not a modern anti-lock system. I don't think I could have locked them up. There was stopping power, but it was weaker than I thought it should be.

I don't have much time until the weekend, but I will check the servo to see if it is working, and maybe re-bleed a little, and report back. Thanks.

[IMG=left]http://i160.photobucket.com/albums/t194/pupinabox/353.jpg[/IMG=left][IMG=right]http://i160.photobucket.com/albums/t194/pupinabox/tr7005.jpg?t=1271517043[/IMG=right]

[saabfast]

My cars brakes would lock up all 4 wheels with a heavy application of the standard setup. As above they take a little bedding in, especially if the discs are a little grooved,and the standard setup needs several bleeds to get the air out of the rear as there is only one nipple. I use a pressure bleeder and it still takes a couple of goes.
The other thing is did you replace the rear wheel cylinders? Mine were a little soft and inefficient at the last test (just passed). Although it all looked OK superficially I found that there was a slight leakage visible when the rubber boots were pulled back on the wheel cylinders. I assume that this might have let a little air in. Changed the cylinders and it is all OK again.

Alan
Saab 9000 Stg 1
Saab 9000 2.3 FPT Auto
'81 TR7 DHC

[bmcecosse]

You would know right away if the servo wasn't working - the brakes would be impossibly heavy! If you want to try - switch off and coast down a hill - then try braking. Be ready to start up quickly - so you get the servo action back!!