Brake Upgrades

[Pat Cash]

Hi All,

Has anyone done, or got any suggestions for braking system upgrades for an SR1 (or SR4)?

The car lives at a circuit (Zhuhai Circuit in South China) that is made up of mainly fast straights with heavy braking zones, I feel that braking feel and stability have never been particularly confidence inspiring, being very snatchy at the rear even with heavy forward bias.

The car is running in a hot climate, so ambient air temperature will regularly be well above 30-35 deg C and is fitted with brake cooling kits front and rear, and suffers from fade/soft pedal after 4-5 flying laps

I know that there is a floating upgrade kit available for SR4 from Rad, but I'm not sure that this will provide a total solution and I'd be interested in alternative suggestions!

Cheers!

[fatboy247]

What brake fluid are you running?

I would be running the best/ highest temp fluid to start with then move on to pads/caliper upgrades

I run in 40+ degree temps regularly here in Australia and have never had a problem, i run the floating rotors but standard calipers (but with the best fluid i can lay my hands on)

[Gc285]

Sr1 doesn't need upgrade in my opinion. Set up right it will stop on a sixpence.

Have you checked the brake bias bar is not stopping on the peddle bracket when wound fully forward. Common problem. If it snags ,it means you cannot adjust it forward enough. Mine was touching hard up against bracket after I changed the pads last time. With the previous set of pads, they were fine. I cut 10mm off and solved my problem. I then had enough space between the end of the bias bar and bracket so it didn't act as a stop.

Check which pads you have. Radical seem to be giving out 008s now, which is an endurance pad, rather than the 01s. I found initial bite on 08s wasn't confidence inspiring, ie you stamp the peddle and nothing happens for a second. A second isn't much but when you are flat out and you hit the brakes at last minute, a second is the difference between the corner or the gravel. Go on performance frictions website, It explains the pad compounds

I also found that I glazed the pads once which seemed to lower performance. I found that the way you warm them up on out lap effects performance for a few laps.

Have you got break pressure sensors? I have mine set up so that the pressures front and rear are always up on the dash and I always check them when I first go out. It is how I realised I didn't have enough front bias.

The way you bed new pads in can make a difference.

I also found that the brakes overheat with multi laps of heavy braking, especially on a hot day. I put in ducting to front brake disks which seems to be working.

Last resort, Give Performance Friction a call. They have a tech helpline and found they were very helpful.

ps try changing the brake fluid.

[radical78]

radical used to sell a big brake kit for sr4

[Pat Cash]

Gc285 said:

Sr1 doesn't need upgrade in my opinion. Set up right it will stop on a sixpence.

Have you checked the brake bias bar is not stopping on the peddle bracket when wound fully forward. Common problem. If it snags ,it means you cannot adjust it forward enough. Mine was touching hard up against bracket after I changed the pads last time. With the previous set of pads, they were fine. I cut 10mm off and solved my problem. I then had enough space between the end of the bias bar and bracket so it didn't act as a stop.

Check which pads you have. Radical seem to be giving out 008s now, which is an endurance pad, rather than the 01s. I found initial bite on 08s wasn't confidence inspiring, ie you stamp the peddle and nothing happens for a second. A second isn't much but when you are flat out and you hit the brakes at last minute, a second is the difference between the corner or the gravel. Go on performance frictions website, It explains the pad compounds

I also found that I glazed the pads once which seemed to lower performance. I found that the way you warm them up on out lap effects performance for a few laps.

Have you got break pressure sensors? I have mine set up so that the pressures front and rear are always up on the dash and I always check them when I first go out. It is how I realised I didn't have enough front bias.

The way you bed new pads in can make a difference.

I also found that the brakes overheat with multi laps of heavy braking, especially on a hot day. I put in ducting to front brake disks which seems to be working.

Last resort, Give Performance Friction a call. They have a tech helpline and found they were very helpful.

ps try changing the brake fluid.

Thanks everyone for the responses - Sorry for the late reply, I've been travelling for the last few weeks.

As suggested we played around with brake fluids initially and got better fade resistance/pedal firmness over longer runs, although did not solve the soft pedal completely.

GC285 - Thanks for the experience sharing - We also found that the bias bar catches on the bracket, which is a little disconcerting and somthing to be conscious of. We found that the bar could be wound so far out that it would be blocked by the bracket.

We also fitted brake pressure sensors to be able to monitor bias and it was certainly a good investment, also learning a lot by reviewing braking technique and application.

Its interesting that you mention a compound variation - I need to double check that, as I have certainly felt more comfortable on some pads than others.

Zhuhai Circuit has 4-5 decent braking zones in 14 turns and in the SR1 you're braking from between 130-145mph to below 40-50mph in at least 3 of those. I'm finding that in these zones I'm having to be very consicous of pedal application to prevent the rears starting to lock and thus instability, even with the bias adjusted heavily forwards. Its certainly not possible to just leap on the pedal. The car balance is set up quite soft at the rear, to help with traction to combat exit oversteer, so I don't think that it is an issue with forward weight transfer.

I'm racing against some big, powerful GT cars and braking is really where my advantage should be, but currently I'm sure I'm losing out at least 5-10m in braking zones just down to confidence on the brakes.
And, of course, through not having big enough balls...

[BertBert]

Speaking from SR3 experience, generally getting enough braking at the front is often a problem (often discussed with Phil A with much debate). So in many cases if you hit the brakes hard the rears lock and round you go. I also remember when debating it with Phil he said that poor corner weighting contributes to the problem.

In the dry we were often running with the bias as far forwards as it would go. We were going to experiment with different size master cylinders but never got there.

What brakes are you running at the moment?

If you are getting rears locking at high speed heavy braking, what aero are you running?

Bert

[ndr1]

I'd be interested in what brake fluids are being used. I've tried lots of different brands and have settled on two. Motul RBF600 and ATE superblue racing fluids.

Cheers
Neil.

[splitpin]

BertBert said:

We were going to experiment with different size master cylinders but never got there.

Bert

As they are (as one would expect) different bore sizes front and rear as standard, if that was the solution wouldn't that mean Radical would have got it substantially wrong? I'd say the chances of that were about the same as a pig sprouting wings.

[BertBert]

splitpin said:

BertBert said:

We were going to experiment with different size master cylinders but never got there.

Bert

As they are (as one would expect) different bore sizes front and rear as standard, if that was the solution wouldn't that mean Radical would have got it substantially wrong? I'd say the chances of that were about the same as a pig sprouting wings.

That's partly why we didn't rush to try things out. I'm not sure I quite have the same faith in Radical's papal like infallibility as you Trev! On the basis that Phil said they had improved matters on the RSX, I can happily conclude there was something to improve!

To the OP's question, if what his issue is the rears locking (or one rear lockinng) and not being able to get the bias right, then he needs a way to get more braking at the front and less at the back. Or more grip at the back and less at the front. Or better corner balance at the rear.

Bert

[Pat Cash]

BertBert said:

Speaking from SR3 experience, generally getting enough braking at the front is often a problem (often discussed with Phil A with much debate). So in many cases if you hit the brakes hard the rears lock and round you go. I also remember when debating it with Phil he said that poor corner weighting contributes to the problem.

In the dry we were often running with the bias as far forwards as it would go. We were going to experiment with different size master cylinders but never got there.

What brakes are you running at the moment?

If you are getting rears locking at high speed heavy braking, what aero are you running?

Bert

Interesting info, thanks Bert.

Currently, brakes are completely factory standard discs/pads/calipers, barring additional brake cooling kits front and rear.

Of course, I also have faith in Radical and their ability to design something that works appropriately. But based on the effects that we're getting, my Race Engineer had also been considering recalculating master cylinder requirements to change the intial bias setup.

Aero was also where I was interested. I am not certain and happy to be corrected, but my feeling is that the standard brake components were also carried across from SR4. Which of course is fitted with a rear diffuser, and a more areodynamically effective rear wing.

We run quite high attack on the SR1 rear wing - honestly, looking at the data, the affect on top end speed is so insignificant that it makes almost no difference when trimming the wing out. Without load sensors on the chassis, its difficult to really quantify the affect, but in order to try to reduce the oversteer and increase rear end load for braking we've kept it there.

I would be really interested to see the effects of adding the available SR4 rear diffuser (or similar) on rear end stability, which was certainly an alternative/additional route that I have been considering.
I assume that this is not something that any other SR1 owners have played with?

Edited by Pat Cash on Friday 4th December 03:40

[BertBert]

Also, do you have the single plane or biplane rear wing? I presume the single plane.

So against the (full-fat, not clubsport class spec) SR4, rear (aero) grip is reduced quite a lot to the tune of the wing and no diffuser. So if the problem is at aero speeds (70mph+???) it's not surprising that the brake balance is wrong.

So if you are able to, I'd get the rear working better with the biplane wing and diffuser.

But I could be waaaaay off as I is an amateur!

BErt

[Pat Cash]

BertBert said:

Also, do you have the single plane or biplane rear wing? I presume the single plane.

So against the (full-fat, not clubsport class spec) SR4, rear (aero) grip is reduced quite a lot to the tune of the wing and no diffuser. So if the problem is at aero speeds (70mph+???) it's not surprising that the brake balance is wrong.

So if you are able to, I'd get the rear working better with the biplane wing and diffuser.

But I could be waaaaay off as I is an amateur!

BErt

Yep, still running the SR1 single plane aluminium wing.
I certainly like your thinking. Aero has been on my mind too...

[jpivey]

I might just happen to have a bi plane Carbon Wing that I might want to sell. Perfect fit on a SR1.

[Pat Cash]

jpivey said:

I might just happen to have a bi plane Carbon Wing that I might want to sell. Perfect fit on a SR1.

You have PM!