AP Racing Master Cylinder
Discussion
If you've already got the AP calipers and 10 inch discs on the front, it is well worth changing to the AP master cylinder as the standard it is a bit small in capacity for the four pots caliper. It will reduce travel, be better matched, and give a better feel. They are also shimmed to reduce dead travel which the standard master cylinder isn't.
downsman said:
I found the standard brakes a bit lacking, and found changing the pads made a huge difference for very little outlay. So if you have standard pads try changing them first, you may save a lot of money.
There are some good threads on here and Blatchat on this subject.
Thanks. Front pads changed to Mintex 1144. Made a bit of a difference but now with 220 bhp upgrade I want a bit more slowing and stopping confidence. Might be asking for the impossible but looking at what others have tried. There are some good threads on here and Blatchat on this subject.
Bing64 said:
Thanks. Front pads changed to Mintex 1144. Made a bit of a difference but now with 220 bhp upgrade I want a bit more slowing and stopping confidence. Might be asking for the impossible but looking at what others have tried.
In that case, I think going for the Caterham big front brakes as well as the uprated master cylinder sounds like the way forward 
Bing64 said:
Megaflow said:
I fitted one to a Westfield, it made a huge difference to brake pedal feel and travel
Thanks. Did you make any other changes? My car came with the AP 4 pot brakes and standard master cylinder. Wasn't hugely impressed with the brakes so upgraded to the AP master cylinder. To be honest I was a little underwhelmed with the difference. It certainly did improve the brakes but wasn't the transforming affect I was expecting.
When you say you want more feel and grab, those two things sound more like properties of the pads you're using. So perhaps look into some different pads.
If you're lacking grab then switching to the bigger AP cylinder will have the effect of reducing the leverage ratio. This will subjectively make the brakes feel less powerful as you will need to press harder on the pedal for the same output force. This may not be the result you're looking for.
When you say you want more feel and grab, those two things sound more like properties of the pads you're using. So perhaps look into some different pads.
If you're lacking grab then switching to the bigger AP cylinder will have the effect of reducing the leverage ratio. This will subjectively make the brakes feel less powerful as you will need to press harder on the pedal for the same output force. This may not be the result you're looking for.
As Harris says; the AP master brake cylinder actually reduces the leverage you have on your brakes, ie. the brake pedal requires more force to create the same wheel piston pressure. I did the math and it might have been as much as 200 psi difference at the pads - can't remember. The bore is a bit larger than stock, so you push less to move the wheel pistons the same length, which equates to less leverage.
What the racing master does for you is reduce brake pedal travel as a result, and that gives more feel and better heel/toe action. Plus as another mentioned, it also has less free play in the actuating system. It's also a very nicely made unit.
I switched to one, and then adjusted the leverage ratio on my brake pedal to get some middle ground. My feet have over 30 yrs of rock climbing, ski instructing, and downhill mtn. biking on them, and they don't like much abuse these days. lol.
If you want more grab, you need more caliper pressure, or larger discs, and brake pads with a higher coefficient of friction. That means new calipers and discs, or at least new mounts and bigger discs. Might as well go for the AP racing upgrade to the front brakes. I have it, and it has not only given no trouble, it doesn't even let my racing brake pads squeal. As to higher Mu brake pads that are fine on the road and easy to use; Pagid RS14 seem to be the easiest available and best fit for high Mu and decent enough cold friction/road use, as well as working for track use.
HiSpec also make upgrade front brake kits for the caterham, and will even do a nice rear kit. Some people feel they flex a bit more and are noisier, but they are lighter if you get the unvented large front discs.
If you want to get even stickier, and perhaps better pads than pagid, the CL Brakes RC6 compound has been mentioned before as being about the best track/road pad tried by some (Mu ~0.5). The CL RC5 (Mu 0.41) is a high performance road compound and supposed track day pad for lighter cars. Better cold friction and less noise/dust, but less overall friction than RC6. It might be worth a try if you're not interested in hot laps and huge friction.
I'm liking carbotech on my Subie, though the friction curve is a bit aggressive as they heat up. They make an autocross compound that may work well for caterhams - AX6, works cold, high Mu. The XP8 would be good for track use and pretty good for road. I'm running XP10 in front and XP8 in back on the Subaru. I'm starting to really like them. Cold they are better than stock brembo pads, hot they try to tear chunks out of the tires. I don't know the Mu, but compared to some I've tried, they feel like 0.55. You almost need slicks to make full use of the XP10. They don't seem to be bothered by rain, which is cool. I live in a temperate rain forest, so I like that.
On the caterham I've run mintex 1142(?) obsolete and horrid, performance friction PF01 - very predictable and consistent, though a bit less sticky than I'd like dead cold. Now I'm trying ferodo DSN 1.11, and once used on a track and bedded in, they are pretty good on the street, quite consistent on track, but their release is a bit sticky at times, cold. They also smeared a bit on a track that is hard on brakes, which was a surprise. The performance friction might do better on track and with release, but the ferodos didn't let me down at all and I've never had a car slow down that fast before on a track. (I haven't run the PF01 on a track - but bedding them in the release and friction curve stayed more consistent.)
My next brake experiment might be carbotech XP8 all round, or CL RC6 all round. I've used Pagid RS14 on my Subaru, and they were great, and had a more linear friction/heat curve than carbotech, which might be easier to live with on a caterham. So I may end up with them - a known good solution, but I'd like to try something I haven't used before.
Anyway, I have found that the newer ceramic style race compounds can do a wide range of heat, and give a very high Mu. They perform way beyond the old organic pads, and the sintered metal stuff I've tried. I like pads with a fairly high initial Mu, and good bite, some people don't. With various cars I've played with over the last 30 yrs, brake pads and sway bars have been the most cost effective and obvious ways to change a cars behaviour. Pagid and carbotech have been the best for my heavy cars, and a different universe from most high performance or "fast road" style pads.
What the racing master does for you is reduce brake pedal travel as a result, and that gives more feel and better heel/toe action. Plus as another mentioned, it also has less free play in the actuating system. It's also a very nicely made unit.
I switched to one, and then adjusted the leverage ratio on my brake pedal to get some middle ground. My feet have over 30 yrs of rock climbing, ski instructing, and downhill mtn. biking on them, and they don't like much abuse these days. lol.
If you want more grab, you need more caliper pressure, or larger discs, and brake pads with a higher coefficient of friction. That means new calipers and discs, or at least new mounts and bigger discs. Might as well go for the AP racing upgrade to the front brakes. I have it, and it has not only given no trouble, it doesn't even let my racing brake pads squeal. As to higher Mu brake pads that are fine on the road and easy to use; Pagid RS14 seem to be the easiest available and best fit for high Mu and decent enough cold friction/road use, as well as working for track use.
HiSpec also make upgrade front brake kits for the caterham, and will even do a nice rear kit. Some people feel they flex a bit more and are noisier, but they are lighter if you get the unvented large front discs.
If you want to get even stickier, and perhaps better pads than pagid, the CL Brakes RC6 compound has been mentioned before as being about the best track/road pad tried by some (Mu ~0.5). The CL RC5 (Mu 0.41) is a high performance road compound and supposed track day pad for lighter cars. Better cold friction and less noise/dust, but less overall friction than RC6. It might be worth a try if you're not interested in hot laps and huge friction.
I'm liking carbotech on my Subie, though the friction curve is a bit aggressive as they heat up. They make an autocross compound that may work well for caterhams - AX6, works cold, high Mu. The XP8 would be good for track use and pretty good for road. I'm running XP10 in front and XP8 in back on the Subaru. I'm starting to really like them. Cold they are better than stock brembo pads, hot they try to tear chunks out of the tires. I don't know the Mu, but compared to some I've tried, they feel like 0.55. You almost need slicks to make full use of the XP10. They don't seem to be bothered by rain, which is cool. I live in a temperate rain forest, so I like that.
On the caterham I've run mintex 1142(?) obsolete and horrid, performance friction PF01 - very predictable and consistent, though a bit less sticky than I'd like dead cold. Now I'm trying ferodo DSN 1.11, and once used on a track and bedded in, they are pretty good on the street, quite consistent on track, but their release is a bit sticky at times, cold. They also smeared a bit on a track that is hard on brakes, which was a surprise. The performance friction might do better on track and with release, but the ferodos didn't let me down at all and I've never had a car slow down that fast before on a track. (I haven't run the PF01 on a track - but bedding them in the release and friction curve stayed more consistent.)
My next brake experiment might be carbotech XP8 all round, or CL RC6 all round. I've used Pagid RS14 on my Subaru, and they were great, and had a more linear friction/heat curve than carbotech, which might be easier to live with on a caterham. So I may end up with them - a known good solution, but I'd like to try something I haven't used before.
Anyway, I have found that the newer ceramic style race compounds can do a wide range of heat, and give a very high Mu. They perform way beyond the old organic pads, and the sintered metal stuff I've tried. I like pads with a fairly high initial Mu, and good bite, some people don't. With various cars I've played with over the last 30 yrs, brake pads and sway bars have been the most cost effective and obvious ways to change a cars behaviour. Pagid and carbotech have been the best for my heavy cars, and a different universe from most high performance or "fast road" style pads.
Thanks for your pretty comprehensive reply. Really appreciated. I changed to mintex up front and they were slight better but agree with you they still do not give me that slowing or stopping confidence that I would like. Will explore the front AP upgrade in terms of calliper and disc. Next upgrade is the suspension.
I nearly posted earlier but I think the last couple of responses in particular cover far more detail than I could add. What stil puzzles me slightly is that the caterham stops far better than any 'modern' car, or indeed any car I've driven this side of a proper racecar.
Granted the pedal can feel a bit 'dead' for road use, and lacks 'bite' on light application (IME it feels better when used on track), but that's all down to feel and preference. Bottom line if you tread on the pedal hard, it stops damn fast, will do so repeatedly, and can lock the wheels without too much problem.
So is it an issue of feel, are the brakes not stopping the wheels, or is there an issue with grip (oh, and are you hitting the pedal hard enough!)? That would indicate where to focus attention.
Granted the pedal can feel a bit 'dead' for road use, and lacks 'bite' on light application (IME it feels better when used on track), but that's all down to feel and preference. Bottom line if you tread on the pedal hard, it stops damn fast, will do so repeatedly, and can lock the wheels without too much problem.
So is it an issue of feel, are the brakes not stopping the wheels, or is there an issue with grip (oh, and are you hitting the pedal hard enough!)? That would indicate where to focus attention.
Edited by upsidedownmark on Thursday 21st September 09:31
All good points. :-)
I feel that there is a definite technique to braking on the seven, someone once said it was like smacking the pedal. You do have to get used to the lack of a brake booster, and with trying to actuate the brakes with authority and in a timely fashion.
One thing the AP master does is help with time lag, and feel, so it is easier to get a precise and immediate initiation, even with the lower leverage.
I agree that the brakes on track are amazing, and never changed feel for me on a very hot day on a track that eats brakes, and boiled the fluid in my big brembos on a subie. A pad that can handle a bit of heat is all that is needed. They stopped so quickly, and when the R888s got hot, it was almost unreal. And the car just kept doing it lap after lap.
On the road the brakes are good, but don't feel as good as when hot. I think even normal brake pads are a bit too cold in everyday cruising for such a light car - plus I almost never need the brakes on the highways and twisties. So they never get warmed and stay warm.
Despite a cold brake and a bit of time to get that extra leg force into them, the car is so small and light that it still stops better than most cars for distance, it just feels a bit dead cold and when using moderate pressure. That's why I'm trying to find a fairly high Mu pad with decent bite cold, that still works on a track. The high Mu pads seem to give it a feel more like what I'm used to with power brakes and decent pads on a big car.
It is an odd dichotomy that the brakes stop in short distances hot or cold, but feel longer going slow and cold than going fast and hot. The AP calipers are sure good on a track. No squeal, clatter, vibration or cooked fluid.
I feel that there is a definite technique to braking on the seven, someone once said it was like smacking the pedal. You do have to get used to the lack of a brake booster, and with trying to actuate the brakes with authority and in a timely fashion.
One thing the AP master does is help with time lag, and feel, so it is easier to get a precise and immediate initiation, even with the lower leverage.
I agree that the brakes on track are amazing, and never changed feel for me on a very hot day on a track that eats brakes, and boiled the fluid in my big brembos on a subie. A pad that can handle a bit of heat is all that is needed. They stopped so quickly, and when the R888s got hot, it was almost unreal. And the car just kept doing it lap after lap.
On the road the brakes are good, but don't feel as good as when hot. I think even normal brake pads are a bit too cold in everyday cruising for such a light car - plus I almost never need the brakes on the highways and twisties. So they never get warmed and stay warm.
Despite a cold brake and a bit of time to get that extra leg force into them, the car is so small and light that it still stops better than most cars for distance, it just feels a bit dead cold and when using moderate pressure. That's why I'm trying to find a fairly high Mu pad with decent bite cold, that still works on a track. The high Mu pads seem to give it a feel more like what I'm used to with power brakes and decent pads on a big car.
It is an odd dichotomy that the brakes stop in short distances hot or cold, but feel longer going slow and cold than going fast and hot. The AP calipers are sure good on a track. No squeal, clatter, vibration or cooked fluid.
Poopaconk - Imho, it's a bit of a case of 'they all do that sir'. Don't want to appear patronising, but I know you're fairly new to the caterham and unless you're used to / comparing with cars without servo brakes I'd genuinely suggest you live with it for a while and see if you don't get used to it. They just don't have (and will never have) that effortless bite on light application, you need to push a lot harder - and that's really a good thing for controllability.
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