Car Wants To Lock One Wheel.

[No Crust Racing]

Have just rebuilt all my calipers after one (rear left) was leaking. Completely flushed the system with all new fluid, but the car did this prior to all that work anyway.

S13 with the following.

BM50

4pot s14 front calipers on slotted, ventilatted rotors with QFM A1RM pads

Stock rear calipers, solid slotted rotors with the same pads

Stock lines.

Super dot 4 fluid (was running TWF600 - but same behaviour before).

Black caliper paint - aww yeah.

Car wants to lock up the front right first(driver side), doesn't pull to one side so I'm thinking the brake force is even but the right side has more camber or something and less tyre contact so wants to lock sooner.

Tyres are super shit Wan Li 215s at the moment, but did the same when it had R-Comps on it, and does the same with the 235 RS-Rs on it, but you can go alot deeper/harder on the RS-Rs.

Any other things I can consider? I know the driver side front has the shortest line, but I though the 2 fronts should have even power in terms of BMC valving.

If it had uneven power or one caliper wasn't bled well enough and had poor grab it would pull to one side?

After the first drive I went ahead and bled it again.

Some more air came out after re-bleeding, but after bleeding each caliper another 5-6 times with no more air coming out I put it all back together.

Pedal still has a bit of travel and still wants to lock the front right first but this time it also locked the rear left a few times depending on the slope of the road and it locked the passenger front once also. still using shit tyres.

Under brakes, hands off the wheel it's pretty straight but will wander slightly left or right.

FYI this is a non abs car, do they have any brake force distribution control?

[pf.]

There may be air in the system still, yes it should have a prop valve. My guess is that there is air somewhere up high in the system near the master or prop valve.

Also what is the camber difference it would have to be huge to make a difference to rule it out let the front right tyre down then test again.

Edited April 1, 2013 by pf.

[No Crust Racing]

Camber diff would be minimal. .1-.2 of a degree tops.

The car has always favored locking that side with heavy braking despite multiple bleeds, fluid changes, and now fully rebuilt calipers.

I know a car will always lock one wheel first but does not having abs make that more pronounced?

I'm thinkin of getting one of those hand pumps you connect to the bmc, anyone had experience with those?

Do they push air through or suck it into the bmc?

[Roy]

If you have combed over the brake calipers and done a rebuild on them and cleared/flushed the lines etc and you are still pinching brakes then 75% chance its nto brakes and its actually suspension. About the last brake related thing I would try is swapping the pads over from left to right and right to left. Doubt it will do anything but pad thickness and rotor thickness is about the last variable to consider

What shocks are you running? Are they adjustable? Are the dampening settings the same on the front and rear? Are your ride heights correct? Lastly is your swaybar adjusted correctly, is it fouling on sump etc when the car pitches forward?

Are your tyres actually round or does your front right have a bit of a flat spot?

Ultimately its not overly unusual for one corner to lock up before others. The thing to ask is it prematurely locking when you feel there should be more in the stopping? Some pads are easier to modulate then others...will be interesting to see if you resolve it and what was causing it. Very hard thing to diagnose on the net

[No Crust Racing]

That was the suggestion on NS also Troy, corner weights. The car has always had this behaviour some I'm confident it's in the setup and not the brakes. I might buy one of those hand pumps to directly suck from the caliper nipple and go one more time for good measure, but I'll probably forget about doing that and leave the brakes as in bleeding wise.

To answer your questions.

- BC BRs

- Yes, height and damper.

- Generally they are set to softest setting all round for street testing (8/6kg springs f/r) but I usually have the fronts a touch harder on the track than the rear to compensate for the nose heavy weight distribution. This behaviour is less evident with better tyres and the shocks adjusted but I wanted to rule out any mistakes I might have made with the brakes.

- The ride heights are all within a few mm tops from wheel centre to guard lip and from wheel centre to ground, they are not even front to back though, back is a touch lower (I think it's 10mm?) if I recall as the car (stock) sits a bit bum high.

- Swaybar is stock, no fouling.

[Roy]

Do you have a strut brace?

[No Crust Racing]

Yes, front non adjustable.

[Roy]

If you put the car on even ground and remove the strut brace does it bind or align when you free up the bolts?

Other thing would be to jack the car and inspect all the joints for wear or flogged out bushes, bearings etc. Anything different side to side.

[No Crust Racing]

You mean the strut brace catching on the bolts as I try to remove it? It comes off pretty easily I think, you can't pull it up perfectly evenly though as the bolts angle in a touch so they are closer at the top of the bolt than at the bottom.

Ball joint rubbers are looking sad, could probably use some new ones.

[Roy]

Yeh, I only ask about strut brace as if the thing binds and you need to jack the car up to get the droop in the chassis right to bolt it up then you know the strut brace splays the chassis a little. If it aligns ok then it isnt doing anything unusual.

I suppose the earlier questions do you feel there is more in the braking but you cant access it because this corner pinches or is it simply always the wheel that locks?

A simple test could be to run the front right damper 3-4 clicks softer then the front left and see if it changes the tendency

[No Crust Racing]

At the moment they are on max soft, so I'd have to turn the passenger side up to have the driver side lower than the pass side.

I'm using a fair bit of pedal travel so there wouldn't be "heaps" more in it I guess. I can use a touch more with the better tyres but that balances out by having the shocks stiffer for track work so it loads up the tyre faster.

It's more a case of not wanting to flat spot a tyre over bumps etc.

[No Crust Racing]

To add something extra to the mix.

I pulled the BMC and could see no signs of any fluid behind it. I have read that they can leak internally back into the BMC so you get the long pedal but no fluid lose so not sure why the long pedal, I can live with that though.

I did some very rough eight measurements and found that there's a 7-10mm difference between the two fronts, no idea why and I'd have to set the car up properly to get proper measurements.

The side that wants to lock up, driver side front, is the lower side, and I thought more weight on that corner would make it harder to lock it up or do I have it backwards?

[GTSBoy]

The higher corner has more "weight" on it. Think about it. The suspension on that side is propped up. That is the essence of corner weighting. That corner and the diagonal opposite corner will carry a greater % of the weight.

[No Crust Racing]

That makes sense, should be an easy enough fix then.

The rest of the cars ride heights are where I thought they should be so it seems that the front passenger side is the odd one.

Shocks haven't been out since they were adjusted and point in either, and they had even ride height then and even shock length etc.

I'll take a look.

[No Crust Racing]

OK I went out and dropped the passenger left side down the 10mm that was the difference.

Went or a drive and once the pads were fully warmed it would alternate locking each front wheel depending on road camber so the ride height definitely made a difference.

It still feels every so slightly biased to the driver side wheel but the road tends to slope to the passenger side so I assume a touch more weight would be on the side if the ride heights are even.

[GTSBoy]

Good stuff.