Weekend disaster
Discussion
Disaster struck our race team this weekend @ Snetterton. We were running 7/8th quickest in practice, got drawn 6th on the rolling grid out of 25 cars, it was decided for me to start the race, 6 hours with 1/2 hr pit window change over/refuelling. Off we went, made a reasonable start and kept out the way of traffic, 2nd lap and coming out of Riches right hander, the field were bunching, I took evasive action and took to the curb on the left hand side. Unfortunately the curb gave me brake knock, next corner is a 2nd gear hair-pin, I applied the brakes, foot straight to the floor, desperately tried to pump the brake, but to no avail and hit the car infront at about 60-70mph!!! Recovered the car back onto the race track, but new I had done some damage, engine temp light came on and got to the pits as quickly as I could. Rad and outrigger's that held the rad and bonnet in place were un-repairable, we had to cut these off and replace. 28 laps down and we re-joined the race, but for us now, all it was about was having fun, our race was done. Gutted for my team mates and crew, 325 miles to Snetterton and to kill our chance with something so silly as brake knock is a disappointment on my own driving skills. I have experienced brake knock before @ Anglesey where the curbs are big and @ Brands, so I know what to look for and how to overcome, but had had no problems since having stronger return springs fitted to avoid this, so it wasn't in my mind as I rattled over the curb.
That's racing, hoping for better luck @ Brands, hope Graham had better luck then me this weekend @ Brands.
That's racing, hoping for better luck @ Brands, hope Graham had better luck then me this weekend @ Brands.
Lets hope our luck changes!! Next race is @ Brands Hatch on the 13th/14th June:
http://www.funcup.co.uk/home/2014-calendar/
http://www.funcup.co.uk/home/2014-calendar/
StreetDragster said:
What is brake knock?
Matt
Brake knock or knock back is were the wheel and hub flexes (in my case running over the high curbs) and pushes the calliper pistons back. This can be overcome with some slight left foot braking and , as with our car, stronger return springs. Unfortunately I didn't test my brakes after running the curb, schoolboy error!!! This explains it better:Matt
http://stoptech.com/technical-support/technical-wh...
Hollowpockets said:
gutted for you matey, I had a reasonably good weekend, 2 x 12th place finishes then had to retire from 11th in the last race a couple laps from the end when my car conked out for no apparent reason. Gutted as I was beating the Lambo and the top Challenge spec cars at that point.
Graham, with that level of competition, that's great results. Any reason yet for the failure??This is brake knock back!! See how I run the curb without really realisizing how much vibration I'd put the car through. The click when I hit the brake pedal was the pedal hitting the floor!! Then up the back of my mates Holden Racing, at least I didn't take them out aswell!! This kind of curb required small left foot braking to get the brakes back, didnt do it and paid the price 
I hit them at about 74mph!!
https://m.youtube.com/watch?v=JOE4wI8inVc
I hit them at about 74mph!! https://m.youtube.com/watch?v=JOE4wI8inVc
You need to look at stronger return springs or the reason the calipers are pushing the pads back, riding a kerb like that shouldn't push the pads back to the point you lose the brakes.
What brakes does it use? I wouldn't be happy using my track car if I had any question my brakes wouldn't work after riding a kerb....
What brakes does it use? I wouldn't be happy using my track car if I had any question my brakes wouldn't work after riding a kerb....
We have the strongest return spring available. We have an uprated AP brake system, we will be sending this to JPR who run the car. We uprated the springs after experiencing knock-back @ Anglesey and have had no issues since. Normally with knock-back the brakes come back after a few pumps, for some reason they took alot more pumping to come back after running this curb. For the rest of the race I was left foot checking the brakes, every time they were fine, very strange. Next race is @ Brands, high serrated curbs there, we will have to be careful!!
Every other pit stop we check the hub nuts, through testing and qualifying. Before a race they are checked again, it would seem the vibration pushed both pistons on both sides back in. In a normal situation that I've had before,, the first push of the brake will see it to the floor (scary the first time!!), next will start to get them back, not this time. This is what makes me think both brakes must have been effected due to the number of times I had to pump the brakes!!
wessexrfc said:
Max_Torque said:
Can i suggest a carefully aimed bullet cam (or cheapo web cam) and some testing? That way you can see when it flexes and how!
I understand your thinking, but if its down to vibration I'm not sure we would see anything but a blur due to vibrate?? Might be worth a go!!Gassing Station | Noble | Top of Page | What's New | My Stuff