Brakes locking up

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rob234
Posts: 16
Joined: 22 Oct 2011 09:04 pm

Brakes locking up

Post by rob234 » 08 Dec 2011 08:52 pm

Just wondered is it common for 340 brakes to lock up really easily??

any sort of slightly exagerated braking i lock up and the back end steps out is this common?

any suggestions to stop this but still have good brakes let me know

cheers rob

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Speedy88
Posts: 4057
Joined: 04 May 2009 11:52 pm
Location: Bristol

Re: Brakes locking up

Post by Speedy88 » 09 Dec 2011 12:24 am

Nope, the 340's rear brakes are ornamental at the best of times :shock:

I would guess that either the brake bias valve is shot (do 340s have them?) or the rear brakes are binding. Either way, hummm. Doesn't sound like things are working correctly :?
'88 340 Williams (Sold)
'85 360 GLS - Drift project (Sold)
'77 Colt Sigma
'96 940 Drift project

macplaxton
Posts: 3283
Joined: 09 Feb 2008 02:29 am

Re: Brakes locking up

Post by macplaxton » 09 Dec 2011 11:17 pm

Could also be Teflon tyres. :lol:
72 DAF 44 Estate 78 Volvo 343DL Black BeautyImageImage
82 Volvo 343DL CVTImageImage 88 Volvo 340DL Diesel

Ride_on
Posts: 2262
Joined: 26 May 2009 05:34 pm
Location: Belfast, N. Ireland

Re: Brakes locking up

Post by Ride_on » 10 Dec 2011 01:03 pm

Hmm yes, in a straight line the back should not not lock up before the front. You could have a problem with your fronts, they do most of the stopping, brake bias valve is pretty reliable. In the dry your face should fall off and the front lock up (ignoring what the back does), if not then you have weak front braking.

The Rear axle radius arm adjustment is also important to eliminate rear toe-in, which can cause rear grip problems. The bushes gradually wear, or if the arm has been off and not properly adjusted after could contribute.

If braking force seems otherwise normal just the backs are locking up too early, the adjusters could be stuck (very common but usually causes weak rear braking) or over correcting, or something else like incorrect assembly. And yes the brake bias valve should reduce pressure to the rears. And yes you need decent tyres.

The prevailing opinion is the 340/360 brakes are perfectly adequate even in race if you have new fluid and they are in generally good condition. The 360 and 340 brakes are the same except the 360 has quite different rear drums (larger and different mechanism).
1980 345 DL_______1987 360 GLE (project car restored to GLT spec and B230FT'd)
1984 360 GLT______1987 360 GLT
1983 360 GLS______1989 360 GLE
1985 340 GL_______1986 340 1.4
1985 360 GLS______1995 940 SE 2.3 Turbo Estate (daily)
1987 340 GL 1.7

rob234
Posts: 16
Joined: 22 Oct 2011 09:04 pm

Re: Brakes locking up

Post by rob234 » 11 Dec 2011 12:18 pm

cheers for the responses but it is all 4 wheels locking up. does have shody tyres on atm but it did the same with decent tyres on 15's. got some new wheels an tyres to fit once ive got pcd adaptors if braking is still dodgy ill take a look. does the 340 have a biasvalve as standard on will i need to fit one?

i did read on another thread if a 360 rear axel has been fitted and not the vale it can cause rear bias and lively braking is there an easy way to tell the difference?

cheers rob

Ride_on
Posts: 2262
Joined: 26 May 2009 05:34 pm
Location: Belfast, N. Ireland

Re: Brakes locking up

Post by Ride_on » 11 Dec 2011 06:09 pm

Clearly the brakes are working well then. Methinks the interface between the road and tyres is the problem. Have you got the right pressures? Don't rely on garage gauges.

Brake bias is fitted to all 300s. Its called 'pressure concious reducing valve' and is bolted to the front left chassis leg beside the engine. It should never need attention.

My 360 would tend to kick the back out when cornering and braking, generally brake pedal should be applied gingerly when cornering, its not really recommended together. Brake before the corner then use the corner to slow the rest of the way down.

The Haynes manual will explain, if you don't have one try the resources section, or internet car manuals (£1.70 for most car manufacturers workshop manuals on CD).
1980 345 DL_______1987 360 GLE (project car restored to GLT spec and B230FT'd)
1984 360 GLT______1987 360 GLT
1983 360 GLS______1989 360 GLE
1985 340 GL_______1986 340 1.4
1985 360 GLS______1995 940 SE 2.3 Turbo Estate (daily)
1987 340 GL 1.7

rob234
Posts: 16
Joined: 22 Oct 2011 09:04 pm

Re: Brakes locking up

Post by rob234 » 18 Dec 2011 12:55 pm

haha cheers but i know how to drive. It steps out in a straight line. I am running silly pressures in the rears for drifting which probably also doesn't help ill just live with it for now

Ride_on
Posts: 2262
Joined: 26 May 2009 05:34 pm
Location: Belfast, N. Ireland

Re: Brakes locking up

Post by Ride_on » 19 Dec 2011 01:41 am

rear alignment then, unless the brakes are unequal, but check your rear radius arm adjustment. With 50kg in the boot, I think the box sections of the rear axle should be horizontal. Thats the adjustment procedure anyway, loosen off the adjustment bolt then retighten with the load, but your bushes could be worn out aswell meaning its not maintaining the correct geometry.

Radius arm problems cause the rear wheels to toe-in usually, which will cause problems under braking or if you hit puddles. The camber turns into toe-in as the axle rotates, the radius arm is there to keep it all in check as the suspension goes up and down.

Alternatively the axle could be bent.
1980 345 DL_______1987 360 GLE (project car restored to GLT spec and B230FT'd)
1984 360 GLT______1987 360 GLT
1983 360 GLS______1989 360 GLE
1985 340 GL_______1986 340 1.4
1985 360 GLS______1995 940 SE 2.3 Turbo Estate (daily)
1987 340 GL 1.7

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