Racing Brakes / wet setup? (video in thread)

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Racing Brakes / wet setup? (video in thread)

Post by knutspeed » Mon Aug 30, 2010 9:14 am

I tried carbon metallic pads along with a 625 master, and this works fabulously in the dry - but in the wet...well, a feather touch on the pedal made the fronts lock, and I'm having newbie issues with "reading" input from the Imp chassis, so ended up driving like a sissy. Yoko 048s for the wet at the moment. Used CM pads in my Mini, and loved the car in the wet, but the Imp is a proper car which I have to drive rather than wrestle/slam/toss :D

What do other racers do? Use standard pads, more rear bias? I'd really like more feel/feedback from the front of the car.
We unhooked the front ARB, softened the dampers and lowered pressures, so the car handled well, but brakes were useless and very scary.
Last edited by knutspeed on Tue Aug 31, 2010 8:33 am, edited 1 time in total.
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Re: Racing Brakes / wet setup?

Post by james » Mon Aug 30, 2010 9:44 am

I think it needs more rear brake bias in the wet, since you don't get the weight transfer to the front, and the front of the Imp is light. TBH, I can lock my front wheels more easily in the wet with standard brakes.

You can increase the bias by changing the lining compounds (reduce the braking at the front, or increase at the rear) or using a bias pedal box. I'm guessing that you still have drums at the back - what compound shoes are you using?
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Re: Racing Brakes / wet setup?

Post by Grumpyoldmen » Mon Aug 30, 2010 10:25 am

Birger
When are we allowed to see that "sissy-driving" on YouTube from the Classic & Sportscar Meeting in Våler this weekend?? :D

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Re: Racing Brakes / wet setup?

Post by knutspeed » Mon Aug 30, 2010 10:35 am

I think the rear liners are standard, and we have a bias box (which is a pain to adjust though...). Kristian: arrived a tad late home yesterday, I may have something up tomorrow I guess. Some interesting fighting between the Imp going fast around and out of bends, and a 1300cc Fiat & Mini having brakes :lol: Was actually super fun, though I should have been tons quicker with brakes. Was actually thinking about trying the parking brake at points!
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Re: Racing Brakes / wet setup?

Post by SimonBenoy » Mon Aug 30, 2010 9:08 pm

Hi

I don't think that the setup I use would be legal for your regs. I have discs all round with Ferodo racing pads. I have dual circuit brakes with bias adjustment on the pedal box and a reduction valve to allow me to adjust the pressure to the rear brakes.

If any of the above is of interest, I can supply more details.

Regards - Simon
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Re: Racing Brakes / wet setup?

Post by knutspeed » Tue Aug 31, 2010 8:32 am

Simon; yes please, all advice appreciated!

Thinking about it I am also used to feedback from the engine when braking since I've only raced front-wheel drive cars, so I need to learn to "read" the Imp. I think I can use a reduction valve as long as it's not adjustable while driving. Which Ferodo pads specifically? Do you swap between wet/dry? Which tires are you running, CR65s?
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Re: Racing Brakes / wet setup?

Post by knutspeed » Tue Aug 31, 2010 8:33 am

..and to share the skating experience:

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Re: Racing Brakes / wet setup? (video in thread)

Post by benwick3 » Tue Aug 31, 2010 10:13 am

I think that the Carbon Metallic pads may be too hard and efficient for the standard rear shoes. I've only used them once and that was a set of Mini pads welded to Fiat backplates but that's a long story.

On my current Clan I have discs allround taken from an Fiat X1/9 and have no problems even without bias adjustment. On my original Clan the set up was nearer to yours with Viva discs and calipers at the front and drums on the rear. Whilst the car weights are somewhat different may people tend to dismiss the Imp/Clan/Ginetta rear brakes as doing very little. This is not so. I found the best rear shoes to use with this setup to be VG95 with a set currently on the car an a spare set safely stored in the garage. At the front I used Mintex pads, 1155 I believe, but I think they may have changed the numbers now. These along with the VG95 rear shoes worked very well in both the wet and dry, again with no bias adjustment.

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Re: Racing Brakes / wet setup? (video in thread)

Post by ImpManiac » Tue Aug 31, 2010 10:56 am

My Chamois uses Fiesta front discs and standard Imp rear drums on standard linings, I think. I've not been in there since I got the car back from its partial body restoration in 2007.

Mine locks the fronts too easily in the dry. I have a bias pedal box but it wants removing and sorting out. I think I could use a restrictor valve in mine but for the fronts, if anything.

For the above reasons, I shall investigate rear discs. :wink:

IM 8)
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Re: Racing Brakes / wet setup? (video in thread)

Post by Grumpyoldmen » Tue Aug 31, 2010 12:30 pm

It would be natural to have rear disk brakes on the Imp for reasons motioned above. Reason for not having rear disk it's so hard to modify.....I am told. True??
How many of you smart kids 8) has rear disk brakes??


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Re: Racing Brakes / wet setup? (video in thread)

Post by knutspeed » Tue Aug 31, 2010 1:10 pm

Rear discs not homologated for Historic Appendix K racing...but seems we need better rear liners + a bias valve that can be changed quickly. The pedal box version is ankward to get at, to see exactly where it's set etc. We'll go with that plus some gentler front pads that will need a stronger brake foot :) Some brake dive would be desirable as well.

At least we we'll be busy this winter! Hopefully we can get another test day in before the snow.
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Re: Racing Brakes / wet setup? (video in thread)

Post by Grumpyoldmen » Tue Aug 31, 2010 3:23 pm

knutspeed wrote:Rear discs not homologated for Historic Appendix K racing....
No, I was thinking about these British fellows.
Anyway, engine sounded like a sweetie on the video clip, and car appeared to have potential.

BUT the second heat........the official track info said DNF??
And the other car....?
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Re: Racing Brakes / wet setup? (video in thread)

Post by knutspeed » Tue Aug 31, 2010 5:59 pm

Grumpyoldmen wrote:
knutspeed wrote:Rear discs not homologated for Historic Appendix K racing....
No, I was thinking about these British fellows.
Anyway, engine sounded like a sweetie on the video clip, and car appeared to have potential.

BUT the second heat........the official track info said DNF??
And the other car....?
Kristian - see shag.no for full story :)
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Re: Racing Brakes / wet setup? (video in thread)

Post by impmann » Tue Aug 31, 2010 8:24 pm

Hi there,

If you are locking the brakes up too easily, then I would tend to agree with Pete that your current linings are too hard/harsh. Perhaps some softer "fast road" rather than race linings would sort things out.

I'd also agree with Pete about the rear linings - modern asbestos free linings are IMHO rubbish compared to the 'full fat' variety. I don't know about the regs/environmental b*llsh*t applicable where you are but perhaps trying to locate some better rears would make the rears bite better. Then in conjunction with a tweek on your bias box (and the softer fronts) you'd get a better balance.

Hope you get it sorted.
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Re: Racing Brakes / wet setup? (video in thread)

Post by knutspeed » Wed Sep 01, 2010 6:53 am

Thanks all! Will try softer pads + more aggressive rear linings and see how it all works out!
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Re: Racing Brakes / wet setup? (video in thread)

Post by Grumpyoldmen » Sun Sep 05, 2010 5:51 pm

This discussion is confusing. Does softer pads have lower friction coefficient? Hard pads = racing pads are supposed to stand heat better and last longer and the effect of this, they need harder brake pressure.

That's the main reason to have soft pads in a standard car because the average driver don't brake that hard and if he does, he obviously are unable to press the brake pedal hard.

Front disk brake front - rear drum brake are no problem in a front heavy car. Rear brakes don't do much work. In the light front Imp it is another matter. You always lock up the front brake on the Imp. And if you transfer to much brake effect to the rear wheels, you will spin :evil: !!
It's a balance in wet.
Soo...maybe it's not a matter of front, but the rear brakes!!
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Re: Racing Brakes / wet setup? (video in thread)

Post by ImpManiac » Sun Sep 05, 2010 7:46 pm

The relationship between friction coefficient and pad 'hardness' is not a simple one. Standard 'soft' pads give good initial 'bite' and reasonable feel but are not optimised to be able to withstand serious heat buildup. As they get hot, the coefficient of friction is altered and the pads lose their effectiveness - often dramatically.

Race pads, though, need heat in them to offer good feel, so can be perceived as 'wooden' under road use. As they get hot, they get more effective and feel improves.

Most modern Original Equipment (OE) pads are of much higher quality these days. Fade still happens but most modern cars, in my experience, have decent brakes. Imps do too but are not in the same league. Drums retain more heat, it seems and heat is the enemy of good braking under road conditions.

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Re: Racing Brakes / wet setup? (video in thread)

Post by knutspeed » Sun Sep 05, 2010 7:48 pm

It's a matter of having a pad that doesn't bite as quickly (I probably used the word "soft" wrong). The front lockup also happens in the dry, but of course requires more effort. When I tried Doc's other Imp last autumn, I was horrified of the brakes; I could absolutely stand on them, but the car didn't appear to slow. No chance in hell of locking anything. So, for confidence's sake, and a chance of passing people under breaking, I asked him if we could try Carbon Metallic pads - which transformed my Mini - and a different master cylinder. We did, so I'm to blame :)

However, the other master-cylinder gave a much firmer pedal with less travel - like I'm used to from other racecars. I cannot stand a soft/long pedal, as I wouldn't get any warning if there was something wrong.

After discussing with people in the know, on this board, and through other channels, we will likely use a different compound pads at the front for wet sessions, along with more rear brake. When braking in the wet, you are much smoother, so you don't get the sudden weight transfer forwards. If you stay off trail braking, you should have more total braking power with some more rear bias. For the dry, we will simply do a test run and get the front/rear bias right, and that won't be much trouble. We'll keep the CM pads, and use a different fluid. The brakes were excellent (apart from the locking up of the RF tire which was due to setup issues - now cured), but I did boil the fluid :)

I come from Minis, and all the weight is on the front, nearly always. However, I ran CM pads and standard setup rear brakes *without ever* having problems with the rears locking - neither in the wet or dry, which most people have, so I think I'm smooth enough. But with the Mini - as mentioned - everything happens at the front, so I'm used to totally different signals from the car when on the brakes. For instance, you can feel it in your bum as well as hear it when you are on the edge of traction, as locking or semi-locking the front will affect the engine/box and give a ton of feedback. I'll just have to drive the Imp some more.

Here's yours truly racing a Mini at the same track in even worse conditions, doing a bit better:
(2009)
And in 2008 it was more or less the same :)



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Re: Racing Brakes / wet setup? (video in thread)

Post by Grumpyoldmen » Sun Sep 05, 2010 7:59 pm

So.........heavy rain, cold brakes and not working in their right mood ! 8)
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Re: Racing Brakes / wet setup? (video in thread)

Post by bks974c » Sun Sep 05, 2010 8:17 pm

2009 race - excellent driving particularly liked the pass on the porche passing on the outside, the long way round.

Well done.

Have you considered the tyres as part of the locking fronts problem? Suspension set up, negative camber good when grip available maybe not so
good in the wet. Tyre pressures?

Scott
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Re: Racing Brakes / wet setup? (video in thread)

Post by knutspeed » Mon Sep 06, 2010 6:09 am

bks974c wrote:
Well done.

Have you considered the tyres as part of the locking fronts problem? Suspension set up, negative camber good when grip available maybe not so
good in the wet. Tyre pressures?

Scott
Thanks :)
Yes, we tried the ACB10s first just to see, and then ran the 048s as these we are comfortable with (doc was very fast in the wet on these with the other Imp). We also started with pressures too high, and have gone lower for each session. Currently at 17/20 psi cold. Some negative camber has been added.
We also found that the car is fitted with too soft rear springs (legacy of previous life haphazardly ignored by us in good faith!); these are next on the list, as the car also was quite understeered unless given a hard bootfull of go-pedal at the right revs..
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Re: Racing Brakes / wet setup? (video in thread)

Post by ImpManiac » Mon Sep 06, 2010 11:33 am

This is interesting reading for someone, like me, that is interested in developing his race car. Well, actually, mine is not yet a race car because I haven't raced it! :) But it will be.

Amazing video, once again, by the way. Your car sounds fantastic!

Carry on... :wink:

IM 8)
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Re: Racing Brakes / wet setup? (video in thread)

Post by Grumpyoldmen » Mon Sep 06, 2010 12:23 pm

Knutspeed give us a lot: car developing, racing videos and other interesting information. 8)
These Norwegian guys are clever!!! :mrgreen:

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Re: Racing Brakes / wet setup? (video in thread)

Post by knutspeed » Mon Sep 06, 2010 1:29 pm

Thanks all! :D
This is the great thing about the net; the possibility of sharing information and enthusiasm. We like to be transparent - to tell more or less everything, because we get so much help from places like this. Playing mother Duck in super secrecy is not our style. Better to find out your'e way off/dumb and learn from it quickly than hide in a cave with your guns :wink:

I'd like to know, in miles, how far it is to the next Imp enthusiast from where I live...
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Re: Racing Brakes / wet setup? (video in thread)

Post by Grumpyoldmen » Mon Sep 06, 2010 5:45 pm

knutspeed wrote:.....I'd like to know, in miles, how far it is to the next Imp enthusiast from where I live...
less then 341 miles! (549 km) (yes, there must be someone closer?)
That's the distance I have to go, to be able to look inside your engines and gearboxes!! :D
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Re: Racing Brakes / wet setup? (video in thread)

Post by big J » Mon Sep 06, 2010 7:12 pm

knutspeed wrote:
bks974c wrote:
Well done.

Have you considered the tyres as part of the locking fronts problem? Suspension set up, negative camber good when grip available maybe not so
good in the wet. Tyre pressures?

Scott
Thanks :)
Yes, we tried the ACB10s first just to see, and then ran the 048s as these we are comfortable with (doc was very fast in the wet on these with the other Imp). We also started with pressures too high, and have gone lower for each session. Currently at 17/20 psi cold. Some negative camber has been added.
We also found that the car is fitted with too soft rear springs (legacy of previous life haphazardly ignored by us in good faith!); these are next on the list, as the car also was quite understeered unless given a hard bootfull of go-pedal at the right revs..
Maybe have less negative camber when it's wet might work?-
Not cornering so fast,so-
Less leaning in the corner,so-
Tyre more vertical would be better?
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Re: Racing Brakes / wet setup? (video in thread)

Post by moose » Tue Sep 07, 2010 8:28 am

Knutspeed did you get my PM regarding rer uprted shoes?
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Re: Racing Brakes / wet setup? (video in thread)

Post by knutspeed » Tue Sep 07, 2010 8:36 am

Ah, I most certainly did! Didn't see it until now...Answered!Thanks :)
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Re: Racing Brakes / wet setup? (video in thread)

Post by IMPerative » Thu Feb 02, 2012 6:42 am

A bit late - If you cant get it right by playing with your balance bar go up a size in your front m/c or down a size in the rear m/c.
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Re: Racing Brakes / wet setup? (video in thread)

Post by knutspeed » Thu Feb 02, 2012 8:30 am

ImpErative - what size m/cyls are you running?
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Re: Racing Brakes / wet setup? (video in thread)

Post by IMPerative » Sat Jul 14, 2012 9:29 am

Sorry, just saw your request some 5 months later..... My car is yet to turn a wheel but it is set up with a bias box and two .625's with an increased pedal ratio as Pimpdrivers suggestion.
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