Car unstable on hard braking????


J

JamesSSB

Ek9SSB
Joined
Feb 21, 2008
Messages
316
Hello,
Im James, from Civic-life,
I am asking for help from the Experts, that may know what my problem could be.
At high speeds if I step on the brakes very hard the whole car wobles and the car sways from side to side??
Too me it feels like maybe the fronts are working harder than the rears?
Now I have installed all this myself but I only bled the system out with pumping the breaks with a non return type system, but have not yet had the system vacuume bled and am thinking this could be a problem with air in the ABS valve?? The only other thing that im not sure about is the fact that the front and rear Pads are off different heat ranges and also the rear calipers are Ek9 and the fronts are standard EK4 calipers as they are mached with the Tenzo-R big break kit.

If anyone could sugest a new setup or a quick answer to my problem then this would be great.

Running Gear:
Advan RG2 alloys,
Goodyear Eagle F1 GSD3 Tyres
Tenzo R Big brake kit 300mm (12"),
EK4 front callipers,
EK9 master brake cylinder,
EK9 rear callipers,
EBC rear grooved disks,
EBC red stuff rear,
EBC green stuff front,
Goodridge braided Stainless Break hoses,
Skunk2 Pro camber kit front,
Skunk2 Pro camber kit rear,
Skunk2 Pro-C Coilovers,
Skunk2 Pro rear lower control arms,
ASR rear brace and sway bar with DC2 rear anti-roll bar,
DC Sport Front double upper top Brace,
EK9 RX rear Chassis braces,
Full Hyper-Flex Polyurethane Bush kit,

DSCF0103.jpg


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DSCF0035.jpg


Thanks,
James.
 
nothing much to do with the brake, your alignment is out. When was the last time you had your alignment done?

If you can bring the car down to my workshop then we can check it out for you.

cheers

Dixon
 
Hi Dixon,
Really??

Well i had a local garage who specialise in TVR's to align the car for me last year when i put the new parts on. What makes it do this then?

Also were are you and how much would you charge to set up the car for handeling?

James.
 
Dixcel is it not possible that he has pad material unevenly distributed along the rotors surface causing a wobble? People often refer to it as "warped rotors" but its usually just deposits from the pads unevenly building up on the rotor...
 
No im sure its not that blinx, just looked and the pads are fine, 100% the disks are not warped either.

But i do see your point.
James.
 
im guessing you put bunch of used calipers on ?

ek4 front and ek9 rare isnt best balance either and why choose to run more aggresive pad on rear than front ?

please tell me you didnt fit used pads or discs ?
 
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No they dont make red stuff pads for the front and i used to have prelude calipers on front with Red stuff in them but they were not making full contact with the Tenzo-r Disks so i swaped them back to standard Calipers.
I re-furbished all the calipers with new seals and the disks/pads were all new.

James.
 
if you feel alignment is fine take each caliper apart and checking funtioning properly and equally, replacing just seals will do nothing if caliper is sticking/starting to seize

i have almost identical problem at the rear on mine as you describe, 1 of my rear calipers is brand new (been on car about year maybe little more now) and 1 is oem that has been on from day of production, took both of, cleaned up, greased slider pins etc and put back on, 1 felt ever so slightly stiffer than the other but no clear indication of problem about week ago although when braking hard from speed clearly problem somewhere

back end improved but problem still there so over weekend just gone i took both of again and checked and 1 is now much stiffer than the other so ordered brand new caliper

will be fitting weekend so will report back and gonna get vacuum bled (i normally manually bleed every 6 months and never had problem with pedal feel etc or brakin in general, i doubt your problem will be bleeding but to be safe and systematically eliminta epossible causes you may as well bleed again)
 
Is your car driving straight or pulling when you put your gas down? What alignment machine did the TVR specialist used? When you put new camber kit, they will usually move a little in the first few months. this might be the reason that cause the problem. It might be bushes problem as well we can check it all over when the car is here.

Yes my place is in DA8 1QL, come down anyday we are open 7 days a week.
 
Yea its posible that the calipers are sticking but unlikely, as they were neew pistons and were compleatly refurbed....?

Dixon, Im out off work at the mo, so low on cash. Your not far from me about an hours drive with no traffic so i will come too you soon. How much would you charge to look at it?

James.
 
JamesSSB said:
No im sure its not that blinx, just looked and the pads are fine, 100% the disks are not warped either.

But i do see your point.
James.
Click to expand...

These are not things you can see with your eyes, furthermore the tenzo kit is not exactly quality...
 
blinx9900 said:
Dixcel is it not possible that he has pad material unevenly distributed along the rotors surface causing a wobble? People often refer to it as "warped rotors" but its usually just deposits from the pads unevenly building up on the rotor...
Click to expand...
If he had an uneven pad transfer layer the vibrations would be felt during all braking and he wouldn't be complaining about instability from the whole car.

JamesSSB, since you are sure all your calipers are in working order, rule that out as a problem for now. Looking at the front and back of all discs (with light) to see if they all look the same. That would show any irregularities in pad pressure.

It sounds like the rear is unstable during at the limit braking.
You should try setting your rear shocks to a slower rebound.
Make sure you don't have excessive negative camber. Later on try a less aggressive camber.
Make sure your rear trailing arm bushings are in great shape.
And a primary reason could be too much rear brake bias. I don't feel like doing the math right now, but you may well have too much. Don't assume that your front bias is more than stock because of the tenzo kit, you're using a smaller piston diameter coupled with a wider rotor. Also, keep in mind that your pads could be changing your front/rear bias on the fly. The fronts do worse with heat, the rears do better.
So to test this I would find a long, empty road. With the car just going and the brakes cold, brake hard from the speed where the car becomes unstable. Then speed up and brake hard again. Then do this another 7 or 8 times to build serious heat to see if the instability gets worse or better. (I'm guessing worse) Don't be afraid of the pads smelling, and don't make any complete stops after this until the brakes cool.
If it gets worse then your rears are outperforming your front's when there's heat in them, causing high speed instability. If the instability problem is the same throughout the test then different pads causing different rear bias is not the problem.

Then if alignment from Dixon, different pads, and what we've covered here doesn't work, and front/rear bias is your problem, you can get an aftermarket proportioning valve to fine tune the bias. It's used only to adjust the pressure going to the rear brakes, but for a street car you shouldn't have to resort to this method as the stock prop valve is best for the street.
 
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Thanks Dino-Spumoni!!!

Ill try that when i get some time. If i were to change the front brake setup from the tenzo disk, what would you recomend for caliper and disk/ pads?

Just another idea in the pipeline :)

James.
 
what condition are your rear Trailing Arm bushings in?

I don`t reccomend poly bushes at this location as they only locate the arm in 2 planes,,
(up and down and forwards and backwards) they do not support teh Arm in side to side motion...

The original rubber bushings or Hardrace / mugen bushings still retain the horizontal side to side support of the original design, as the bushing is bonded to the pin that goes through it ,


probably about to open a can of worms here, but i can explain further if required,

Our integra SI has these bushings on the rear Trailing Arm and the Trailing Arm moves from side to side between geometry setting sessions...

this is the bush i am talking about

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trbolt1.jpg


here is a proper bush!!

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hmm...

The swaying (side to side at the rear??) under braking sounds classicly like RTA bushes- so thats a good start as Olly says..

The "wobbling" sounds like warped discs to me.....was the big brake kit fitted new, or the discs/hubs checked for run out prior to fitting ?? My old Golf had 305mm brakes fitted & suffered from what felt like warped discs....turned out to be the hubs in the end. With big brakes the caliper acts further from the cenre of rotation of the wheel, thus putting more force on the hubs

Did your car have any of these issues prior to fitting the kit also?

The other issue you may have is one of brake balance....the fronts should do the majority of the work anyhow, but with big brakes you may be going light at the rear causing instability...

we need more info & answers to the above to be of further help really...:)
 
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Hi all,
Right the disks were new and no they have allways done this.
I have got the rear RTA Poly bushes that are in that picture by the way and this does seem to make sence that they are moving arround...... Iv had the disks on for arround a year and a half, they are not warped....

Im thinking its a case of suspension and alignment not set up correctly..
James.
 
i was wandering this with my ek4....whe in press on the brakes hard the rear goes light and ends up going mental almost spins me out:shocked:
i wad thinking if a anti roll bar waould fix this as i dont have one at them moment? mabe a nice 24mm one from asr? and then uprate the front lower control arm bushes?
 
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