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Hot!Fun Fix.

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Falcon
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2019/05/02 07:39:18 (permalink)
0

Fun Fix.

Early SW20 with the small discs, calipers and 7/8" master cylinder. Flush, bleed, flush, bleed. Still rubbish. Long spongy pedal with no bite and extremely poor stopping power. Can't buy 15/16" master so I get a brand new 1". Purchase second hand late model reconditioned calipers and new RDA discs front and rear. New braided hoses and blow compressed air through all existing hard lines while they are all open. Install all this and also a second hand late model proportioning valve. Flush, bleed. Much better but still no initial bite and a disconcerting hard non yielding (Wooden) feel on the pedal. Crap !!!??? Why.
At the track it appears to have glazed the rear discs. Slight blueing tinge. This is with stock Toyota pads all round. Purchase a second hand late model booster and install it with a new metal check valve at the inlet manifold.
Each second hand component was checked by professionals before fitting. Booster, proportioning valve.
I pumped each caliper piston out a long way and was able to push them all back in with my thumbs.
Caliper sliders are all clean and slimy. Brakes have never dragged.
This car has never had ABS fitted.
After all this gnashing of teeth and many new swear words the brakes were still horrible.
Still with no initial bite and the wooden pedal feel.
#1


13 Replies Related Threads

    Fast Eddie
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    Re: Fun Fix. 2019/05/02 08:21:10 (permalink)
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    Maybe time for a big brake upgrade if you intend/enjoy tracking your SW20, then stopping will be the last thing on your mind.

           1990-GT-Turbo
     
    #2
    Carmikey
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    Re: Fun Fix. 2019/05/02 09:59:21 (permalink)
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    Doug, unfortunately the early sw20s 89-91 have a very crap brake pedal feel compared to the later 92+ mr2's. Even the 92s if compared to post 95 feel crap, but nothing like the pre 91s.
    One of my track cars (black 90 model) you have been in it, has nothing but racing pads and Willwood 600 fluid in it, still original solid rotors, yet pulls up perfectly every time without fade.
    In saying that, other than yes a crap woody feel & alot more additional pressure required to the pedal, they still pull up as intended.

    Sent from my SM-J320ZN using Tapatalk

    #3

    Falcon
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    Re: Fun Fix. 2019/05/03 07:48:05 (permalink)
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    Thanks Eddie but I need to get standard stuff working properly first.
    Appreciate the information Mike. Which race pads do you use ? I have basically converted this car to the later model brake system and the result is very poor.
    I will continue with the saga. (There's more).
    Had the rear discs bead blasted to remove the glazing. Fitted several different new sets of different types of pads over many months and many track day sessions. Still lacking in brake performance. Lots of advice most of which did not make logical sense to me.
    Installed pretty fancy race pads and had Paddy come up to drive it on track to get a valued assessment of it's overall performance. New tyres too so he could really try it. He was not impressed with the brakes. They slow and stop the car and are sufferable BUT are not confidence building. They don't lock up front or rear particularly unless one is unloaded so bias seems about right. We also noticed that day at the track that the fluid level altered by about 6 or 8mm in the reservoir at different times. Very strange ? So that really got me thinking.
    Removed the race pads and showed them to a number of knowledgeable blokes. Conflicting opinions ranging from cooked, crumbled, rubbish material, over heated, not hot enough. et bloody cetra. More new swear words thought up by me.
    I get hold of a second hand 15/16" master cylinder. Flush it out and then empty it's rear chamber and prevent fluid entering the rear chamber. Yeah I am getting bloody desperate for an answer now. Remove the proportioning valve from the system and couple direct from front of master cylinder to front brakes. Rear brakes not connected hydraulically at all. Test drive off road. Can lock front tyres on concrete pavement.
    Reinstall proportioning valve into front circuit only. Rear still disconnected. Can lock front tyres with exactly the same effort as before. So no mysterious things happening in the front part of the proportioning valve.
    This is progress. I'm starting to get definitive answers for myself. I'm also getting very bloody sick of bleeding brakes.
    #4
    Carmikey
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    Re: Fun Fix. 2019/05/03 08:40:37 (permalink)
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    Doug, I've used numerous types of different pads on this car, including QFM AR1m's, TRW, Lucas & currently Project MU HC800. All to be honest haven't given me any issues, from memory the QFM on removal were full of hair line cracks & evidence of overheating in my opinion, but still performed well for what they were put through.
    Please keep in mind, this car I'm referring to is a stripped out NA track car.
     
    #5
    92 Hard Top
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    Re: Fun Fix. 2019/05/03 11:12:22 (permalink)
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    Doug, I put Mike onto Project MUHC800 theses pads are made in japan. I used theses on my 340rwkw beast I had. It could lock the wheels. Hotter they get the better they work. Up 800 degrees. Need to run them in on new rotors. I would say two laps of heavy braking to get them to the right temp once they are run in. There are two version One has a harder compound will last longer, but eats your rotors the other softer one will not last as long, but save your rotors.
    #6
    Reddtarga
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    Re: Fun Fix. 2019/05/03 17:05:48 (permalink)
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    Doug, I don't know if this may help, but are you sure which booster you got?
    You probably know the post '92 boosters (thin body) are apparently more powerful than the earlier ones, (pre '92 either thin body or fat body) and the post '94 thin body ones are more powerful still.
     
    Some time ago I bought and fitted a booster from Hong Kong that was supposed to have come from a '97 turbo, replacing the original OEM ADM '90 model one.
    I also run the early small brakes with stock Toyota pads along with a 1" Supra M/C, along with OEM NA prop valve.
    I also have plain RDA rotors.
    FWIW, although my car is mostly for normal road use, the brakes seem great with plenty of bite, good firm pedal feel, easy to modulate, and dramatically better compared to the OEM long travel springy feel. I also have ABS.
     
    I have also tried a 15/16 M/C with the new booster, but it was too easy to lock the brakes so I went to the 1" M/C.
     
    My '97 booster seemed to be dramatically more powerful that the one it replaced.
    Who knows why?  Because the booster body on it has the same dimensions and shape as my '90 model ADM 'thin body' booster, apart from the check valve, so there is definitely something different inside.
     
    I also could not find any part number on either of my boosters, there was no sticker or anything stamped on them  
    I don't know if your new booster has any P/N on it.
    If not, it could make it hard to pick which model booster you have - just saying.
     
     
     
     
     

    1990 ADM NA
    Any advice you get from me may only be worth what you paid for it.
     
     
     
     
     
    #7
    Falcon
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    Re: Fun Fix. 2019/05/04 07:08:58 (permalink)
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    Really appreciate the replies fellas. Thanks. During all this time I also spent a lot of time faffing about with vacuum reservoirs, gauges, check valves etc. Comparing between this turbo car and the 1998 Bathurst which has brilliant brakes with great initial bite and just beautiful pedal feel. I even swapped front discs and pads from one car to the other. Absolutely no difference. Bathurst remained perfect and turbo remained awful. Couple more answers.
    Rechecked front calipers and sliders. No different to last inspection. Perfectly fine.
    Noticed that when on loose gravel at say 15kph press pedal quite hard for a complete stop and inspect result.
    Rear tyres would skid up a pile of gravel but fronts would barely mark the surface. Another answer.
    Had the 15/16" master cylinder reconditioned with a stainless steel sleeve etc. Rechecked the clearance on the booster rod to master cylinder again. Still spot on. Same as before. Installed. I now reversed the connections so that the rear of the master activates the front brakes via the proportioning valve and the front of master operates the rear brakes via proportioning valve. Remember this car has no ABS. Some other manufacturers vehicles have this setup.
    Bleed the b@#^*d thing again and over to the gravel pit. Hard stop and all four bite and nice pile of gravel in front of each. Fronts have skidded a little earlier than rears. Great. This is approximating the performance of the Bathurst though it has ABS so have to take that into account too.
    Car on the slightest slope and just barely starts to roll maybe 50mm and apply tiniest brake pressure. Car stops instantly. In other words booster is activating brakes correctly.
    Car rolling at say 15kph on bitumen. Little touch on pedal and car dips it's nose instantly.
    Round town it just feels perfect at long last. High speed heavy braking it pulls the speed down really well and eventually locks up. Not sure yet but I suspect a rear. Have AD08s back there so probably not up to the job.
    Need to choose new pads for track. Will be interesting to drive it on track with proper rubber.
    Car is such a pleasure to drive on the road now. Extremely happy bloke.
    #8
    Carmikey
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    Re: Fun Fix. 2019/05/04 08:35:25 (permalink)
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    Good work Doug. I wonder how many others out there have just accepted the braking issue....and either put up with it, or spend thousands upgrading to big brake kits which sometimes other than looks, results are no different to initial problem.

    Sent from my SM-J320ZN using Tapatalk

    #9
    kojab
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    Re: Fun Fix. 2019/05/04 09:31:28 (permalink)
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    Falcon I now reversed the connections so that the rear of the master activates the front brakes via the proportioning valve and the front of master operates the rear brakes via proportioning valve. Remember this car has no ABS. Some other manufacturers vehicles have this setup.



    Could I do the same thing with my SW20 1992 GT hardtop.  I too would like my brakes to have some more bite.

    92' SW20 3SGTE   GEN2 GT Hardtop
    87' AW11 3SGTE   Now Delco EFI ecu & 21 psi boost
    71' KE25 3TGTE    Delco EFI ecu. Unopened std engine 24 psi boost
    78' KE55 L67        Delco EFI ecu
    #10
    5SGTE
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    Re: Fun Fix. 2019/05/04 10:35:39 (permalink)
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    What's different about front and rear of the master? Are the ports similarly sized? Or was the issue with the prop valve/ratios?
    #11
    Falcon
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    Re: Fun Fix. 2019/05/05 06:33:41 (permalink)
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    Yep Mike, I see some BBKs that never get near a track and when I ask a couple of very basic questions the answers tell me quite a lot. I have never understood how tandem duel master cylinders work. I've asked a few different "sperts" an the smart ones say good question. The dumb b#^&##s very quickly demonstrate they don't know either by their answers. One mob when asked what sort of psi might be generated in a cars hydraulic brake system suggested possibly around 100 psi. I didn't bother with any other questions.
    kojab. Be mindful that I haven't yet taken it to the track with proper rubber on the ground. The front to rear bias may very well need more thought. It is certainly very nice as is just on road tyres. Pedal feel, feed back, initial bite etc. is excellent and very close to my 1998 Bathurst brake performance. Happy to have a yarn by phone. So far I've resisted pulling the hydraulics from the Bathurst and have given a lot of thought to that fluid level fluctuation that Paddy produced at the track. Does your car have the little baby brakes? ABS? What size master?
     Kris. Have a bit of a think about what happens with incipient pedal movement. Remember I don't have the faintest bloody idea what happens inside a tandem system. It's taken nearly 2 years of farting about testing and I've only a few days ago achieved a positive result.
    The bright blokes "in the know" on track will never let me follow them. They wave me past, they pull off the track or dive into the pits. Tells yer sompin bout me brakes abilities up ter now.
    #12
    Lumix
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    Re: Fun Fix. 2019/05/06 19:35:57 (permalink)
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    Glad to hear that you are making progress with the brakes. Will you be heading out to Morgan Park any time soon?
    #13
    Falcon
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    Re: Fun Fix. 2019/05/08 06:29:30 (permalink)
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    Just driving it on the road and very much enjoying it at the moment.
    But yes, Morgan Park Raceway probably in about a months time.
    Do you have an approximate date in mind?
    #14
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