996 TT Caliper Woes!
Discussion
cyrus1971 said:
If you rip one brake fluid hose does that mean the fluid will drain from the whole system and you looses all 4 brakes ? Or is there some kind of safety valve ?
No, the rears will be on a different (tandem) circuit, but you will lose the other front calliper!...not that the rears are much good on their own!...Jeezus!!...
Has it definitely sheared the bolt rather than it falling out?....Glad you got it stopped and are OK.
With a split system they are normally linked nearside front/offside rear and the other circuit offside front/nearside rear to maintain a balanced system in the event of a hydraulic failure.
Have you had new discs on?, if so the calipers have to be removed which may account for the fact that the bolts came loose.
Have you had new discs on?, if so the calipers have to be removed which may account for the fact that the bolts came loose.
Lost all brakes altogether - Pedal went down to the floor!
I had just been doing speeds in excess of 160mph around Donnington and came into the pit area because my car was vibrating on braking. As i moved into a parking space at about walking speed, the pedal went to the floor and there was an almighty clatter.
When I got out the car there was a pool of Castrol SRF and on closer inspection you could see where the caliper had been rubbing on the inside of the wheel.
The car has gone to OPC, but would this be a warranty claim??
I had just been doing speeds in excess of 160mph around Donnington and came into the pit area because my car was vibrating on braking. As i moved into a parking space at about walking speed, the pedal went to the floor and there was an almighty clatter.
When I got out the car there was a pool of Castrol SRF and on closer inspection you could see where the caliper had been rubbing on the inside of the wheel.
The car has gone to OPC, but would this be a warranty claim??
The shear strength of a single M10 8.8 bolt is 15kN, which means you could hang an entire 996TT from one bolt.
Calipers are held on with two such bolts and there are 4 calipers on the car.
This could be a stress related failure, but its unlikely that the contact patch of the tyre could deliver anywhere near 10% of the forces needed to shear a pair of these bolts. It sounds more like a torque wrench problem.
Calipers are held on with two such bolts and there are 4 calipers on the car.
This could be a stress related failure, but its unlikely that the contact patch of the tyre could deliver anywhere near 10% of the forces needed to shear a pair of these bolts. It sounds more like a torque wrench problem.
I seem to recall that the bolts actually stretch when they are torqued up. Porsche recommend using new one's every time discs are changed - expensive habit as they cost c £5 each. Could be that old bolts were put back on and they have finally let go??? Would find that surprising though as I used same set of caliper bolts for about 3 disc changes on my old 968. Never had any problems
Did the bolts shear off or did they pull out of the aluminium hub casting??
If they sheared it would suggest they were loose, and if your callipers were rubbing on the wheel it would also suggest this.
New bolts are reccomended by Porsche as they have an anti-corrosion treatment on the thread to prevent bi metallic corroion. Most people use a spot of Loctite and reuse them.
Whilst the bolts are a good and meaty 12mm, think of the forces you exert with 6 pots and a 350mm disc - the pad has the surface area of errr errr Somerset????? fer Krist sake!!
I bet this has got a few of us worried now..... count me as one! Now where did I put my torque wrench????
If they sheared it would suggest they were loose, and if your callipers were rubbing on the wheel it would also suggest this.
New bolts are reccomended by Porsche as they have an anti-corrosion treatment on the thread to prevent bi metallic corroion. Most people use a spot of Loctite and reuse them.
Whilst the bolts are a good and meaty 12mm, think of the forces you exert with 6 pots and a 350mm disc - the pad has the surface area of errr errr Somerset????? fer Krist sake!!
I bet this has got a few of us worried now..... count me as one! Now where did I put my torque wrench????
I don't know what the full failure is yet, the car is on its way to OPC to be checked out.
The car has had new pads fitted a few months ago, but I understand that the caliper does not need to be removed to do this.
My car has the 330mm discs and the 4 Pot big reds on it, and has been serviced by OPC - The last one being in May 2005 (30,000 mile with spark plug change £1200!!!)
The car has had new pads fitted a few months ago, but I understand that the caliper does not need to be removed to do this.
My car has the 330mm discs and the 4 Pot big reds on it, and has been serviced by OPC - The last one being in May 2005 (30,000 mile with spark plug change £1200!!!)
jj996 said:
Lost all brakes altogether - Pedal went down to the floor!
I had just been doing speeds in excess of 160mph around Donnington and came into the pit area because my car was vibrating on braking. As i moved into a parking space at about walking speed, the pedal went to the floor and there was an almighty clatter.
When I got out the car there was a pool of Castrol SRF and on closer inspection you could see where the caliper had been rubbing on the inside of the wheel.
The car has gone to OPC, but would this be a warranty claim??
BEJESUS!!! I thought I had had a lucky escape with my problems, someone must have been looking down on you!!!
Stretch bolts are a myth - someones guess as to why they should be replaced each time, that has somehow grown into 'fact'.
Overtighten tese babies and the first thing to fail would be the soft aluminium.
And as I have just bought a set from OPC they are certainly not cheap - a whopping £18.41 each even with yer PCGB discount! Yes that's £73.65 for a set of four - now you know why they dont get changed.....
Overtighten tese babies and the first thing to fail would be the soft aluminium.
And as I have just bought a set from OPC they are certainly not cheap - a whopping £18.41 each even with yer PCGB discount! Yes that's £73.65 for a set of four - now you know why they dont get changed.....
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