pads

[lazeruspete]

my head is getting fuzzy.

[soe8m]

The actual maximum brake power is to the friction material and area. Not vented, not dia.

Actually the brake force from a disc is about the diameter of the piston and the diameter of the rotor and the hydraulic pressure. Oddly, pad area isn't part of the equation - you need to look at Amontons' laws of friction to see why pad area isn't a term. As I remember, that rotor speed isn't part of it either is one of Coulombs'' laws (no "charge" for that last bit of info).

To have as much pressure on the front wheels during braking you need as much weight transferred to the front so as much dive you can get.

Two of the problems with getting as much weight transferred to the front as possible, are that this takes as much off the back wheels as it adds to the front, which leads to the rear end breaking away; and it means putting the CofG as high up as possible, which is not fun on corners. The other issue I have is that this confuses dive with transfer, implying that weak front springs will improve the braking, which is simply not true once the car's stopped tipping up, and probably not true while it is still tipping. Also, as a TR7 driver, all that dive at the front they do is not nice.

Ah, you're too wise for me, i give up.

Jeroen

[AndyJ]

Poor old Marko,
I'd like to apologise for widening the debate when I plugged the case for vented discs to be made again for members. If you go to the EBC website http://ebcbrakes.com/products/brake-pads/ they clearly state which pads in their range are for which use and you can take your pick. Many swear by them and others choose Mintex or other makes but the main thing I would advise is to visit manufacturers web sites and pick according to their guidance and your use of the vehicle. Personally I have found high quality discs grooved but not drilled to be best although I have only experience on the road and none of competition.
I hope this helps!
Happy Xmas,
Andy.

[Jon Tilson]

I'm not going to take any braking lessons from someone who never drives on a motorway in England and has nothing more to cope with as a driving hazard than a kamikaze sheep.

Accusing me of being a dangerous driver because I drove my dolomite on continental motorways would have been also out of order.

I'll leave space here for an apology in due course, especially from someone who is supposed to set a better example.

It may also be that someone who doesnt drive on motorways regularly is also unaware that 80-90 is the typical cruising speed of most of the Audi A4's and 6's BM 5's and 3's Mondeos focusses and Golfs that I regualrly share road space with on the morning commutes on the M3 M4 and M25 and M40.

Funny how it seemed to be much the same on the A90 up here too....

Some people need to get out more.....

Jonners

[Jon Tilson]

Appologies to Jod as I've been driving about for a few days and leaving him to expound the laws of physics on his own.

Brake fade is as he has so correctly explained a consequence of excess heat build up to the extent that pads and discs can no longer dissipate heat and loose their ability to slow the car down.

As I have explained and will repeat here one more time, standard Dolomite brakes are quite capable of slowing the car in a continuos emergency stop from 90 mph to zero maybe twice in relatively quck succession, ergo they are demonstrably adequet for normal road use. Brakes used to be engineered so that lock up on a dry road could bve achieved with peddal pressures ranging from 60 to 100 lbf at the peddle. This is the sort of effort that a normal woman driver can just about achieve in emergency at the top end of the range.

The problems come or are compounded because of bad maintenance allowing partially siezed callipers and discs to go thin, or even fitting el cheapo brake pads from Moprod etc. I have personally transformed the brakes of numerous dolomites (some of them owned by forum members) by servicing calipers and fitting decent pads. I sometimes shudder to think what people are actually driving about with and wonder if a lot of the bad press and hot air generated about dolomite brakes on various forums is down to ignorance of what the barkes really should be like.

Now when on track or rallying or regularly needing to whiz up and down mountain passes with a full load of passengers I quite accept that the standard setup will cause some fade. In these cases by all means upgrade if you want to.

But please dont subject normal users to wrong advice and make them spend money they dont need to and will see little benefit from when a 20 quid set of caliper seals and some proper pads will see them stop as they should.

Jonners

[Carledo]

Jonners is perfectly right. My Carledo, which goes pretty well, has only slightly uprated Sprint brakes (Greenstuff pads and Goodridge hoses) For road work, fast road work or dragstrip (where brakes are almost optional its true) the brakes are perfectly adequate and have given me no cause for concern whatsoever.
However the first time I exposed them to proper trackday conditions, 3 hot laps of the short Prodrive circuit was more than enough to highlight their shortcomings, squirelly braking and a rapidly disappearing pedal was NOT conducive to fast lap times. Since I had so much fun then (despite the awful brakes) and plan to repeat the experience, the car is getting a Trackerjack kit pronto! But if it was purely for road use, I wouldn't bother!

Steve

[GrahamFountain]

I think, from my experiences with 7 sprints, I'd still add to what Jon wrote that the servo is always worth a coat of looking at. But that's not to detract from what he did say.

Graham

[GrahamFountain]

the car is getting a Trackerjack kit pronto!

What're your plans to bring the brake balance bias back forward of perfect at the limit of traction; assuming these front brakes will give higher brake force, e.g. by virtue of greater leverage from the hub centre or larger/more pistons?

[Carledo]

the car is getting a Trackerjack kit pronto!

What're your plans to bring the brake balance bias back forward of perfect at the limit of traction; assuming these front brakes will give higher brake force, e.g. by virtue of greater leverage from the hub centre or larger/more pistons?

I'm gonna suck it and see! I'm sorry Graham but all the theoretical physics just makes my head spin!
I've already encountered premature rear lockup in spades from my car which is a) an already light 2 door, b) has Sprint rear brakes which are too big for a Sprint let alone a Toledo and c) has been considerably lightened from standard (at both ends)
My solution to this has been to fit a line mounted pressure limiter valve to the rear brakes which has worked so far. I CAN still lock the rears first, but not at anything over 5mph and only by severe stomping on the pedal. Should the problem resurface once the TJ kit is fitted, all I really need to do is fit a lower value limiter valve - simples!
Others have suggested that using the TJ kit with Sprint rears actually IMPROVES the front/rear balance to the point where a Sprint can do without its factory fit load sensing valve (something I don't have anyway).
I'm reserving judgement on that, although my car looks similar to a Sprint, I have changed so much that a lot of stuff like shocker settings and spring rates that work on a Sprint make my car undriveable. I've also used a much lighter engine /gearbox combo set further back than a Sprints which will have moved the CofG back a bit which can only help me in the long term but in the short term, makes life tricky cos theres no "established wisdom" for my car that I can refer to. To a "rule of thumb" pragmatic engineer like me, this just adds to the fun and the sense of achievement when it actually WORKS!!!

Steve

[marko]

What's the mintexs code? I'm trying to cross reference them with some others...

[AndyJ]

I couldn't see them on the Mintex online catalogue but I did find an old reference on here: part number MGB535 M1144. There's a bedding in routine with these which you have to follow the instructions.

[xvivalve]

...but, to reiterate, a waste of money if your discs are aged and thin...

[marko]

I'll be using group n discs from rally design along with either the mintex pads or the Maxtorq version which both combined using princess calipers in my v8 Spitfire is fantastic. Thanks for the help and theories though chaps. The best post I think was the one about crap tyres.