Princess 4 Pots

[Guest hodgie]

Another minor niggle.

Having fitted braided hoses, uprated master cylinder etc and princess 4 pots, the brakes to be honest are not that hot!

I am tempted to exchnage it for a wilwood set up and larger discs! I have 15" wheels (anyone done this? - Easy fit?)

Aternatively am I being let down by my pads? Are Mintex C-tech or EBC Greenstuff pads really that much better?

 

Also is it worth uprating the rear wheel cylinders?

[john.r.davies]

Hodgie,

"Uprated" master cylinder? How?

If you change now to a smaller diameter cylinder, you will get more pedal travel, but the force at the calipers will be greater. That should help.

 

And which Mintex C-Tech compound are you on? 1155 and 1166 need too high a temperature to work well on a road car. If you have these, go for 1144.

 

John

[anthonyt]

I run green stuff for road driving and club level track events seems to be up to the task.

 

Never bothered to uprate master cylinder from the standard 8 one.

 

I went for rear discs rather than uprate the wheel cylinders, worth it for a track car but probably not for a road car, stops every time though and very quickly (you will need to fit a proportioner).

 

Remember the brakes will never be as good as a modern car unless you put modern brakes on.

[Cinnobar]

Mine runs uprated m/cyl, prinny 4 pots on solids & standard whatever rimmer supply with the kit pads. Braided all round. It's OK but doesn't really have any bite, so I lack confidence braking that late!

Have a set of EBC greens here which I was going to fit but not got round to it yet. The main reason is to reduce the 'orrible brake dust on the wheels.

 

Hodgie,

"Uprated" master cylinder? How?

If you change now to a smaller diameter cylinder, you will get more pedal travel, but the force at the calipers will be greater. That should help.

 

And which Mintex C-Tech compound are you on? 1155 and 1166 need too high a temperature to work well on a road car. If you have these, go for 1144.

 

John

A smaller diameter would be lethal, the standard one lacks enough volume for the 4 pots as it is. The uprated one is a larger M/cyl with a larger servo. Both SD1 or Sherpa.

[DaveR]

For what it is worth I have fitted Green pads on our 2.5 Litre Gitfire and 2 Litre Vitesse. Both cars have the standard 9.75" discs and no servo. In my case the Green pads gave a lighter pedal feel and more bit. The pads appeared to wear down more quickly and seemed to create more dust than the standard type. I guess more friction. In both cars the discs are in very good condition.

 

I have bought some for the TR7 but have yet to try them.

[Guest hodgie]

Mmmm, I know what we're saying about modern brakes, but 4 pots, vented front discs, uprated servo and master cylinder and not a very heavy car!

Surely it shoud stop better and more decisively than it does?? The pedal is very firm, but the car just doesn't stop well. It's lock up or mediocre.

 

My girfriends Fiesta brakes better!!

 

It's a quick car. It needs to stop quickly too.

 

I was tempted to uprate the pads and see what that does (£55+)and perhaps the rear wheel cylinders to change the bias a bit, but if it's not going to work, i am just not happy with the set up and will spend the money on Wilwoods and bigger discs.

 

Could it be any thing to do with the 'pressure reducing valve'(?) mounted on the turret?

 

What d'you say chaps?

[malcolm]

Uprated pads don't do much to stop you faster. They help prevent brake fade under high temperatures and are a must for any car that has occasional track use. Same goes for 'vented' disks. I'm a big fan of the 4-pot Princess conversion, which is a hell of a lot better than the standard brakes, but I'm not sure they are much different to the 2-pot 2.8 Capri brakes I had on a previous V8....

 

And the PRV? When mine siezed up it was directing excess pressure to the rear brakes reducing braking performance and even allowing me to lock-up a standard drum under heavy braking(!). You can get NOS PRVs so I'd say replace it if it's likely to be the 20+year old original. You can also replace it with a proper adjustable bias valve but I've not gone there!

 

Malcolm.

[john.r.davies]

Hang on, Cinnie.

Hodgie hasn't told us how big his M/c is.

 

It's hydraulics, remember those?

A smaller master demands longer travel, but exerts a greater pressure at the slave.

Force1/Area1=Force2/Area2 so F1xA2/A1=F2.

See for example: http://www.grc.nasa.gov/WWW/K-12/WindTunne..._principle.html and lots of other educational sites.

 

In practice, of course you are right that too small a master will demand to great a travel.

But until Hodgie tells us the size of his M/c, my advice still stands.

Physics, the theory of everything!

 

John

[DaveR]

One of the reason I fitting the Green pads was the need for more responsive brakes. The pedal was very firm but just needed a lot of shove. All the components in the braking system are in good condition or new. With these pads it now needs less shove. Fade was not a problem on the original type pads and I have not experienced any so far on the Green type.

 

I put it down to the two moderns we have being equipped with disc all round, a servo and ABS. Thought it could just be I am getting old!

 

The improvement on the Gitfire was very worth while and as it is a zero to 60 mph in 7 sec car you do need good stopping power and a lot of common sense!

 

As John quite rightly has pointed out the bore of the master cylinder will have a large effect on the pedal pressure. The gearing up or down of the force required to operate the brakes. So you could change the master cylinder bore diameter to make the brakes more responsive, though the knock on effect would be more pedal travel and a loss of some of the firmness.

 

The other way to improve things would be to build up your leg muscles and may be fit a very strong throttle return spring!!!!

 

Just my thoughts.

[anthonyt]

Just go down to the gym and do some leg work Hodgie. The bonus being the fitter i get the more beer i can drink without the bad aftereffects.

[MikeyTT]

Probably doesn't help a great deal but the pads to use on a fast road/race car are the Ferodo pads (not 100% sure which model till I get the box out from home). A few have tried the EBC Greenstuff but they lack feel and don't like hard use.

 

I have the Greenstuff pads in both my road going MR2 and my BMW 540, and they are much better than the stock items. I've never run them on a 7 tho. The Ferodos when warm are superb, bit scary if your brakes are still cold tho. On second thoughts not such a good idea for the road ;-)

 

In the class D specification in the championship they have to run on pincess calipers and solid disks. Although towards the end of the race they do start to fade you don't get this for a good few laps. This setup should be more than adequate for a road car, and you shouldn't need to jump on the pedal to get it to work either.

 

For the best setup then a set of hi-spec calipers will give you brakes that you can lock up at over a ton if you're not careful. They're not cheap but you can't get better for your money.

 

Mike...