Brakes Lock too easily

[Tellso]

Hi Guys,

The brakes on my MK1 N/A lock up fairly easily. I have a set of 17's on there at the mo, which isnt ideal. I will be swapping for a set of 15's shortly but would putting a set of ST202 or ST185 brakes on there help? Im not sure how it all works and would think that would give me more stopping power therefore be even easier to lock up?

My mechanical knowledge (and theory) isnt great! So apologies if im talking rubbish!

Cheers

[Bender Unit]

You have 1 of the following:

1) Really good brake pads
2) Really rubbish tyres
3) A heavy foot

Unless you have swapped the brake pads for decent track compound, or your approach to braking is to stamp the pedal through the firewall - I would put my money on crap / worn tyres.

[Tellso]

Theyre only budgets i think, so hopefully that. I must admit this mk1 has a lot better brake feel than my old one and that had drilled and grooved discs on it. I just found it weird it went in the dry when i wasnt going particularly fast. Just slowing down for a speed bump! Grr!!

[aw11rally]

Have you checked that the rears work, I only found that my rears were knackered when the fronts locked or faded very easily.

Worth a look.

Also.... Putting more fricticious (not actually a word) pads on the rear my help even out the balance some what.

[Lauren]

Hi Guys,

The brakes on my MK1 N/A lock up fairly easily. would putting a set of ST202 or ST185 brakes on there help? Im not sure how it all works and would think that would give me more stopping power therefore be even easier to lock up?

That would make it worse. Best bet is to find out how well your rear brakes are working, because on a mid-engined car they do a lot more than they would on a front engined car.

If the rears are not working properly you'll experience more lock up. Rear calipers are a crap design and prone to seizing up. Check them first. Obviously get some decent tyres for your 15's.

[Keri-WMS]

Check you don't have a duff front shock - people don't realise how much grip you lose when the wheel starts to lose damping...

[PW@Woodsport]

Hi Guys,

The brakes on my MK1 N/A lock up fairly easily. would putting a set of ST202 or ST185 brakes on there help? Im not sure how it all works and would think that would give me more stopping power therefore be even easier to lock up?

That would make it worse.

Um no it really doesn't work like that Lauren, we have first hand experience of this as well... think about it, a larger volume of piston but the same MC supplying them, so less lock up but overall better brakes.

Celica brakes vastly improve a Mk1

[cartledge_uk]

You have 1 of the following:

1) Really good brake pads
2) Really rubbish tyres
3) A heavy foot

Unless you have swapped the brake pads for decent track compound, or your approach to braking is to stamp the pedal through the firewall - I would put my money on crap / worn tyres.

I completely agree.

I would also like to add, rubbish brakes. if you your discs are pitted, cracked, your brakes can snatch and lock up.

[alfiembra]

I'll stick my 2p worth in and say sticking sliders, my fronts locked up all the time until I freed them off.

Alan

[Lauren]

Um no it really doesn't work like that Lauren, we have first hand experience of this as well... think about it, a larger volume of piston but the same MC supplying them, so less lock up but overall better brakes.

Celica brakes vastly improve a Mk1

Hmm I tried feamy with Willwood brakes on the front and it seemed to lock up way too easily on track. It really seemed to mess the balance up.

Actually though stock brakes are absolutely fine and up to the job for any NA or SC as long as they are in perfect working order. Brake bias is still too much to the front though as standard.

[MartG]

... think about it, a larger volume of piston but the same MC supplying them, so less lock up but overall better brakes.

Just means that there will be more pedal travel before the pads hit the disk, due to the need to shift more fluid to fill the cylinders on the caliper, but once the pads aren't moving anymore then any increase in pressure at the master cylinder is transmitted to the entire area of the brake pistons - simple hydrodynamics.

[kaiowas]

Um no it really doesn't work like that Lauren, we have first hand experience of this as well... think about it, a larger volume of piston but the same MC supplying them, so less lock up but overall better brakes.

Celica brakes vastly improve a Mk1

Hmm I tried feamy with Willwood brakes on the front and it seemed to lock up way too easily on track. It really seemed to mess the balance up.

Actually though stock brakes are absolutely fine and up to the job for any NA or SC as long as they are in perfect working order. Brake bias is still too much to the front though as standard.

Not driven a car with Celica brakes but I've also driven FEAM and found the brake balance to be similarly horrible (It had Hi-Specs at the time, not sure if these are brakes you've driven or if they were changed). Those brakes were stupidly over specced though considering there was nothing special on the back. I think the current owner has since fitted something else to make it a bit more driveable.

[PW@Woodsport]

Well i've been speaking to Keri about this, and we both agree there is something odd going on with the physics involved because it should be seeing more lock up using bigger pistons, but honestly folks i've done hundreds of big brake upgrades on Mk1's (we invented most of them!) and to date we can't see this lock up problem.

I have Porsche 996 4 pot calipers on the front of my Mk1 and i just have amazing brakes with no lock up, similar to the ST205 upgrade i did years ago, again no extra/earlier lock up going on.

Keri and myself are in agreement that there must be something weird going on with a Mk1 bias valve to account for this because in the real world i'm just not seeing any increased lock up with bigger brakes, neither have any of my customers a lot of whom do track work.... all very odd.

[Keri-WMS]

That's pretty much it - if there are bigger pistons and bigger discs going on the Woodsport cars and the front is locking up less......something odd must be going on because brake system physics says the opposite (force = pressure x area, so increase the area and you increase the force!).

I wonder if the typically wider front tyres on engine swapped cars are the reason? (more grip means you can brake harder = more weight transfer to the front = an increase in grip at the front and a decrease at the rear).

This is largely speculation of course, in terms of actual numbers/facts I can only speak about standard bits vs WMS bits.

[PW@Woodsport]

Keri perhaps even the heavier engined swapped cars are themselves playing a part? More weight=more inertia=brakes needing to work harder, tyres having more weight on them too= less lock up?

Feasible?

[Keri-WMS]

I don't think so to be honest, if anything it would be the other way round as the extra weight is all at the back?

[PW@Woodsport]

Possibly, but doesn't that weight transfer forward under braking? Or at least the inertia caused by it?

[Keri-WMS]

To an extent, but for adding weight to the rear to allow an increase in the % of grip at the front under braking due to weight transfer I would have thought you'd need to be stopping at several G's.

To think about weight transfer...

- Constant speed (or no speeed!) is like a car on flat ground.
- Decellerating gently is like the car is on a slight slope, nose first.
- Decellerating at 1G is like the car is glued to a 45-degree slope, nose first. This is because the 1G forwards and the 1G down (gravity) results in a net force forwards+down at 45-degrees.

...and so on. So our car is on it's 1G (45 degree slope), you can see what amount of the car is over the front wheels and the rear wheels....and the engine is still over the rear wheels!

To put the engine over the front wheels the slope has to be made much steeper by adding extra G's of braking!

To get a feel for G's under braking, the best road cars manage about 1G, and F1 cars manage about 4G (5-6G at really fast circuits).

---------------------------

Odd fact of the day (O.T.!!!), an F1 car has so much drag due to the wings and open wheels, that it you come off the throttle at full chat (and knock it out of gear) it will decelate at 1G from wind resistance alone!

[Lauren]

So nobody knows why MK1s with over-sized brakes apparently defy the laws of physics?

[PW@Woodsport]

All very interesting! I'm just offering possible reasons as to why we aren't seeing lock up issues with our big brake upgrades, i thought maybe the extra engine weights might be playing a role...

Interesting topic though!