RC8 Pads/ abs Delete On Track Car Locking Up

[getikte]

So, ive just finished an ABS delete with bias valve on my ph1 172 and fitted a set of RC8 pads.
i can get the bias adjusted so the rears lock before the front however the front passenger side caliper locks up under braking every time.

the pedal also feels strange, the top section of travel feels fine however it gets to a point where half way down its travel the brakes will lock. is this just the nature of an ABS delete that i can go and stamp on the brakes like i used too or are the pads too grabby or possible issue with the caliper?

little bit lost to be honest! ive only tested on the street with AD08 tyres in cold ish but dry conditions, will be running full slicks on track.

 

[JB21]

Not got the ABS deleted but my 182 locks the NSF first with RC8s. Does it drag you left as well? The pads are mega spec TBH and not sure they suit such a light car.

 

[getikte]

yea they pull me quite badly to the left under heavy braking its not fun lol. first track day on these pads and sicne the abs delete is next monday at croft. some high speed braking zones there so really want confidence in them

 

[JB21]

Maybe due to less weight on the NS of the car with stripped interior? Dunno but it's scary braking at 100+

 

[JamesBryan]

They do have a friction coefficient of 0.6 which is quite a lot compared to RC5/6 and DS1.11's.

 

[getikte]

im hoping that when everything gets hot on track it will kind of come together.....might be able to dial it out a bit with the shocks, was running full soft on the road when testing yesterday, maybe a stiffer set up will help....maybe not im kind of clutching at straws.

ive got a spare caliper im going to try incase that one is sticking for whatever reason.

 

[White16valver]

Aren't there MOT centres or similar that can tell you brake efficiency at each corner, or is it just on each axle?

I'd be tempted to think the same as already mentioned, though - it's a lot of pad for not a lot of car, so it may just be overspecification at work lol

 

[bob the builder]

I run rc8 on my race car and don't have a problem. have you bled the calipers to eliminate any air in the system.
also it could just be cold tyres.

 

[getikte]

My next plan was to pop it on the brake rollers at my work and see what the forces are. Even if I set the bias valve so it's just the rears locking up the front left will still lock. Does anyone have a diagram as tI which masyercylinder port goes to which caliper?

 

[shiftspark]

Think there was one knocking about in the last week or so. I think @Pauleds put a picture up.
HTH

 

[Pauleds]

Cup m/c

Although my rear lines are into a T because of the bios valve and hydraulic handbrake inside the car.

 

[getikte]

okay so after checking all the lines everything is 100% piped up correctly. The passenger side front caliper still locks up regardless of bias setting and tries to throw me off the road to the left.....any ideas before i have a huge crash at croft on monday lol?

considering buying some DS3000 as ive had them before and used them at donny on a mates DC5 last month and they were fantastic but not too grabby which i think might be an issue with the RC8s

 

[bashracing]

If you have coilovers try putting more preload on the n/s/f or have it professionally corner weighted.
Also on a static rolling road brake test you can't factor in for load transfer under braking so it will only tell you the brakes efficiency up until the lock point, where as you need to find out the efficiencies above that point (a couple of fat f***s sat on the front slam panel will help).

 

[...]

Just got to the bottom of the post and the above is spot on ,

some people corner weight across the diagonals with the driver in the car and some across axles .......obviously the diagonal weighting and coros axel weighting is difficult to get the same , but the weight on each front wheel being equal will help .

however this only stops locking if you brake in a straight line as any change to the steering being dead straight will unbalance weight .


Welcome to the world of driving fast and the techniques to go with it re weight transfer and modulation of the brake pedal .

 

[getikte]

My next plan was to swap over the discs and pads side to side just incase for whatever reason something was causing them to catch so if the problem transferred to the OSF then i know theres an issue with that..... ive even got a spare NS caliper so i can rule out it being any issue at all with the brake hardware as such.

i did think about the weight transfer being an issue and it loading up the wheel heavily, driving with having to factor that in is new to me so may also be the case, not sure if theres anywhere in the north east that can corner weight the car especially by Monday.

 

[bashracing]

Try AK Automotive, It's a few years since I dealt with Antony (don't even know if he still owns it) but if he can't help he will point you in the direction of someone that will.
https://www.facebook.com/pg/AK-Auto...ists-270698682956729/about/?ref=page_internal

 

[JB21]

Stick with the RC8's and have a play with your pre-loads on the day mate, don't let them defeat you :up:

I'm gonna give them another blast at Aintree in May, I've just got wider front tyres to throw on to aid traction under braking, hopefully this will help and it'll come together nicely.

 

[getikte]

i have messaged AK automotive to see if they can help in time at all. and yea i think i will battle on with them as they work for some people they just seem to be causing more harm than good for me ATM. see if it comes together on the day.

 

[JB21]

i have messaged AK automotive to see if they can help in time at all. and yea i think i will battle on with them as they work for some people they just seem to be causing more harm than good for me ATM. see if it comes together on the day.

I think you'll be OK on the day with hot slicks and a bit of pre-load adjustment, if rain is forecast then maybe take a set of pre-bedded in OE pads with you just in-case.

 

[getikte]

i hope so! and yea ive got some standard pads so could be a good shout if its raining

 

[mikekean]

Sounds like a dodgy caliper or you have you lines connected to the wrong ports on the M/C to me.

 

[bashracing]

The pressure is equal from all ports on the cup mc, the rear compensator valve is the only place of pressure reduction

 

[getikte]

ive checked the lines are correct with a mates 172 cup which has the engine removed so you can clearly see the routing. i did think the caliper might be an issue so i have a spare to try if it comes to it.

 

[DCELEC 182]

When I first fitted rc6 pads so not at the same level as the 8's even....the first session and certainly few laps the brakes felt ridiculously grabby and kept locking up/couldn't seem to brake progressively but once they needed in they were absolutely fine with good initial bite but not the grabbiness and no fade whatsoever!
You need to try them on track where they can get properly hot, you'll never replicate that on the road.
They don't seem to last too long before crumbling round the edges though.

 

[cpaterson76]

I had similar issues with 8s..... but more to do with temperatures of the day. Warmer days and stickier tyres the 8s worked perfectly, on a cold day or wet day I had to switch to ds1.11s.

To be fair that was with a 197 / 200 brembo conversion up front, so that with the initial bite of the 8s meant a cooler day was a fun time!

 

[Tony Hunter]

Corner weight first, you wouldn't believe how important this is when aids start getting removed.

 

[getikte]

Spoken with AK automotive and although they couldnt do the corner weighting before Monday (I'm not surprised my fault for leaving it late) they are there setting up a car on Monday so I have said I will have a chat with them about it. Hopefully it's dry, forecast said it should be and with my slicks on and descent temps they will come alive.

In the mean time is there any way I can set my suspension to send a bit more weight to the rear. I suspect this is most of the issue now as the front weights must be massive compared to rears. As the car sits it probably has a bit of rear rake. I'm heading up to work this after noon to get it on the 4 poster and level it out. Maybe run slightly higher fuel on the day?

Any further advice? I'm well acustom to track days....just never gone this advance with car set up before.

 

[getikte]

P's it's the passenger side every time be it front or rear.

 

[Tony Hunter]

In your op, you said it was the front n/s locking, not both front and rear?
The car should be nose heavy, mine is about 326 on front corners, and about 180 on the rear corners, impossible to get it perfect, but without the front being heavy and even, you will get locking, so I doubt you would want to get more weight on the rear.

 

[JB21]

Don't do anything until the day then have a mess about with pre load and brake bias if your still locking up. It'll come together on the day with hot rubber and a bit of fettling.

 

[getikte]

Front suspension was all over the shop to be honest, different amounts of pre load on the springs and massivly unequal length on the front struts. So that's all equalled out and the brake rollers don't suggest there is anything wrong! Time up. I'll mess about on Monday.

 

[JB21]

Car looks ace mate, are they full slicks yeah? What compound?

 

[getikte]

They are mate yes and S9C which is a hard compound. Can be difficult to get temp into rears but once warm they were another level of grip and turn in feel at knockhil. I've got road wheels and tyres too....ad08r

 

[JB21]

Full or rear cage?

 

[AdamCup]

What suspension are you running and have you stiffened the rear beam ?

 

[getikte]

Just the rear cage at the moment will be full before long. Its the safety devices rear cage with double X bars, harness bars, B pillar mounts and exhaust tunnel brace.

And suspension wise running BC coilovers with a stiffer spring set up than normal. Rear beam isn't strengthend no

 

[getikte]

Car was mega at croft, brakes came together in the end, i was still locking up and wasnt able to lean on the brakes as heavily as id have liked but i think with the corner weighting done and some more practice without the ABS i will have it sorted.

 

[...]

It becomes natural eventually , i am used to caterhams etc with light front ends and narrow ish tyres
Your modulation becomes better though it's easier without servo assistance

 

[Tony Hunter]

I had twin servos on my old rally car, I ended up removing them, much better feel, especially on gravel.

 

[Inequality Street]

This is probably a good thread to semi-hijack (sorry) about my track car build in progress. So I'm not overly mechanical, however have a Clio that I'm slowly trying to work on doing things myself and with friends. One of my friends got a bit trigger happy with removing wires, and now I have no ABS module or wires etc..

I've been told this will now mean my brakes are 50% front 50% rear which is not right, and I'll need some kind of BIAS Valve to correct this. But tbh, this is all beyond my capabilities/knowledge. What would you do? Continue with this method, or try to re-install ABS?