whats best to too look at? I currently run 295 bremsports with yellow stuff but I think I am at the limit of both the pads and the heat the discs can take, so I think I need BIGGER... both disc area and pad area specs are: willwood dynalite pads used 295 x 28mm discs on seperate alloy bellls 25.7mm master cylinder mk4 rears and yellow stuff rears dot 5.1 fluid car weight is 1100 kg with driver and tank of fuel + passenger on trackdays... speed reached at bedford was 135+mph on back straight!!! Im currently thinking either Ibiza 305 Bremos with DS2500 pads or the Highspec 300mm conversion depending on the pad size, or can anyone reccomend anything else bearing in mind the pad sizing? (pad sizes http://www.wilwood.com/BrakePads/BrakePadsList.aspx?padtype=71 - area is 4103.2 square milimteres cheers Karl.
I have been doing some digging and it appears that the hi-spec 300mm conversion uses a smaller pad.. so thats out I fear Pads I have already over heated http://www.camskill.co.uk/products.php?plid=m31b0s3086p18077 hi-spec pads http://www.camskill.co.uk/products.php?plid=m31b141s3041p15965&rs=gb from what I can see the ibiza brembo pads are 109.7mm x 69.3mm so quite a bit bigger area
Brakes are a real headache Karl. Nothing we see is ever a definite answer, can only try it etc. The Seat set up might be worth a go if you can lay your hands on some.
When you say dynalite pads, do you mean the Polymatrix ones, if so I know they're not so well rated. I'd try some DS3000's before you condemn the brakes. Change the fluid too! Maybe upgrade that too (if you're like me and using Halfords)?
Chris - Im hoping I can work out roughly the energy per square mm of pad area to see how much is too much...also any one elses views and R and D would be helpful, but I know from my job that brakes can be a mine field. Benny - I was using EBC yellow stuff pads, which some rate and some dont, previously I had been fine with them but the new set up uses a smallerl pad area al be it on a slightly larger diameter disc but on a car that is heavier and ALOT faster, I feel I have reached the energy limit of the system as the brakes were getting hot, and the wheels VERY hot, changing the pads for something like DS3000 will just mask the problem and cause more I fear with the discs then overheating or the bearings over heating. I can sort some of the problems with better cooling but not all...
does it come down to physical size, the need to go bigger? or better, more suited, compound of pads on discs? had you found the braking to be as bad on other circuits? Bedford is a long fast, hard braking track. I don't think any of the cars there this weekend got away with suffering from brake issues. The hot smell of cooked brakes lingered in the pits all day
this is their first real bashing other than road use, but I do plan a few more outtings for the car next year, I have found the braking to be ok on the road but not always brill, so bigger should be better, and if I can find a bremo kit I should have a slightly cheaper choice of pads and discs as I plan on doing some proper millage next year in the car
Bigger brakes = more weight for the brakes to deal with! That's the limit of my engineering prowess!! I wouldn't be looking at Hi-Spec, they have issues too! The 280mm Wilwoods have always had a good rap, beyond that I'd be looking at well known reliable systems, AP etc, or... whatever Maurice is running on his Mk2 say? I think there could be time, effort and cash wasted on a bespoke (home made?) system to find similar fading results. That said we are all on a budget! Also, what works for oner person may not work for all. Some of us are heavy brakers (I am), some are not...
more weight isnt too much of an issue in a roundabout way... its unsprung mass so harder for the suspension to deal with but it copes ok with the current 4 pot set up so should be ok.. also bigger discs = more interia to stop and accelerate but again bigger brakes = more leaverage so that over comes the stopping interia and the accelration is no issue. 280s wont be anywhere near enough thats for sure! my mk2 isnt that light and im not stripping it any more... I like my home comforts, plus its not exactly slow!! (as most at Bedford found out!) for now I think Ill just fit a new bell to the set up and some new pads so I can move the car around and keep digging over winter
How much power have you got? This might sound a bit cheeky, but have you considered that the brake issues might be down to driving style too? Also, if you're worrying about the brakes, you're probably using them more just to be sure - it can be a bit of a vicious circle. I'd have thought 300ish degree discs on a car of that weight should be enough.
your brakes you have on there should be more than ok for it. I would look at upgrading the brake fluid. dot 5.1 just isnt good enough for track cars.
The engines pushing 275bhp and 275lbft torque, I wasnt that hard on the brakes tbh I was braking early-ish and smoothly, and for some of the complexes I was engine braking and crusing rather than coming out of a corner racing up one gear and then jumping staright on the brakes again. I knew they were not as brill as they should be and what I have been used to on previous cars so I adjusted my driving style, ie more engine braking, braking earlier and not just mashing the pedal to the floor in the hope it will stop faster, as I know from experiance and testing at work that once they have started to go off pressing harder just kills them quicker Champo - its not the fluid, its the pads went off due to too much heat, which is down to lack of pad area and disk area for the amount of energy I was putting in, The equation for working out the energy per square mm of pad that is used for testing R90 approved pads is: 1/2 x Mass x Top speed squared, so for mine its 0.5 * 1200kg * 220kmh (top speed I reached at Bedford but the car will go faster!) then devide that by the pad area to get the energy per mm squared. so for the current set up its : pad area 6262mm squared... so the energy per mm = 4637.5 for the ibia the pad area is 7383mm, so the energy is 3933.4 Ill see if I can find the testing for the yellow stuff on file and see what it was tested up to and I have exceeded the energy per mm or just the overal temp spec
There is a huge range of brake pad materials out there now. A lot of new stuff puts old fashioned materials to shame. Trying a pukka pad at 100 a set and see how you get on. You get what you pay for. The trouble is if you run the car on the road you will just glaze a serious race compound pad as it is never going to see the conditions it was designed to operate in.
I think I may have to go to 2 sets of pads... ones for track days and one for road use.. but this makes things more complicated, as you can't just "pop" pads in and out... to do it properly you need to clean the discs very well between pads to remove all traces of the old pads, other wise you get contamination between the 2 whcih takes a while to remove. on a side note I have been digging in the files on works servers and it appears that the yellow were tested with a higher energy imput that I used, 1785kg stopped from 271khm on a pad area of 9360mm2 which gives an energy of 7039! so 1.5 times the energyof me, BUT this is on a brembo 8 pot system with 2 pads of 4608mm2 per side, and larger discs and way better cooling! plus its only 1 stop not repeated.. But it does sort of confirm that I over heated the pads due to a number of factors, smaller caliper area, not enough forced cooling and smaller disc area so a smaller heat sink effect,... Ill send the results off to my contacts and see what they have to say too...
Seat(Brembo) calipers are always well rated, took me 12months to find some and they are in dire condition. Disc's are not cheap, 2 peice ones are really. expensive(As always) From experience with other cars, including indurance racing, I would consider Pagid RS pads, the only bad thing about them is the squeel(OK and cost). RS19's and 29's hold up fine on 6hrs of Spa, discs are dead at the end though. RS15's would be the best bet, ceramic based, so lots of noise. Thats a large MC you use?
I'm still going to stand by it being the fluid. I've used 5.1 in my cars in the past. It doesn't cope too well with the extra heat of track use. After a few large stops the fluid gets too hot. Boiling it and decreasing the pressure applied. The brake pads are rubbing the disc chattering on the surface rather than gripping it for a better stop.
brembo 305mm oe discs are ALOT cheaper than the discs I just got for my set up.. 160 a disc! heres the pics of the pads when I removed them back at home, they have overheated, this could be blamed on pad material... but the overal problem if you chase it back is the speed and weight. ie problem pads over heating > why have they over heated? > heat range exceeded of the pad material - why? > due to too much energy imput from the speed and weight of vehcile being stopped, not enough cooling and heat capacity of the calipers and discs not being high enough. fixes - higher heat pads - trade off less cold bite and feel and only 50/50 it might work. - extra cooling - brake ducting will help reduce temps a bit but the wheels I have are very open so gain might not be enough to fix all the problem. - bigger pad, discs and caioer area - bigger pad will lower the enegery per area of pad, and lower the temps slightly, also bigger discs and calipers will have larger area so bigger heat capacity and act as a bigger heat sink. using the brembos with forced cooling should mean I can run a all round pad like the yellows or ds2500s with out too many issues on track, a belt and braces approach. these pads are very small compared to a oe pad, like a girling 54 one as used in the 256/280 oe set up, even the 239mm pads will have a bigger surface area
A better pad (Performance friction, DS3000 etc) will stop your car quicker and stop the brakes from fading so quick. But this will make the discs hotter (Glow ) which could cause you other issues. Going bigger, as you have already said, should help you out. However, get rid of weight from your car on the whole, and your setup will be fine as it is . I got away with 256mm discs on Girling 54s using DS2500 due to less mass to stop. They still had more to give but my T1-Rs were at their limit. Gurds
I have been tempted to ditch some weight, but I don't want another buzz box like my old mk1, the mk2 is nice to use in the summer everyday as its queit-ish and comfortable-ish... if I strip out more weight ie no carpets, door cards, half the dash, I will just end up back like with the mk1, a car that very fast on track, but no good on the road. I might fit polly windows next year to save some weight, but other than that and the sun room theres not that much to lose! carpets and sound deadening is 20kg tops, lower dash is not much at all 10kg tops? rear wiper motor 5kg... It already has a carbon bonnet thats saved a fair few kg! plus theres a cage going in over winter so that will offet the polly windows! hi-spec say their set up thats very close and uses pads that are within a few mm the same size is only good for 1200kg, which would suggest again I am at the top end on the system.
