BLUEMOMENT

First two apologies: 1. this isn't very (well at all) boaty, and 2. I posted this in TOP in the Lounge - with no replies, so I thought I would see if the more erudite clientèle of BM might be able to assist.

I have an irritating problem with my car (a Volvo V70, but I don't think the problem is necessarily model specific).

The handbrake works perfectly going forward, i.e. it easily holds the car facing downhill, but does not work in reverse, i.e. it will not stop the car rolling back when facing uphill.

I've taken the drums off, and everything looks fine and correctly positioned. I took the shoes off and checked that the expander (if that's the right term) is working properly. All OK. Reassembled, set the shoe adjusters and the cable adjuster - and no change. Both rear wheels are doing it: when jacked up with the handbrake on the wheel can easily be turned backwards by hand but locks when turned forwards.

All helpful suggestions gratefully received.

I am not mechanically inclined and so my suggestion would be that you trade the wretched vehicle in.....

Stormy is offering 2 bricks. if you accept I will pay postage.

It's a weird one, I can't see why it would be a directional problem. Modern trailer brakes have some jigeripokery to allow reversing but that shouldn't be on cars.

Some suggestions here
http://www.volvoforums.org.uk/showthread.php?t=64540
which are to use genuine volvo parts & if not use the hand brake whilst driving (moulds the shoes if new)....

I can't believe I'm going to offer engineering advice to DaveS but what the heck - I've never previously been afraid of making a laughing-stock of myself...

AFAIK a typical car rear drum brake set-up involves both shoes being pushed against the drum from adjacent ends making one a leading shoe and one a trailing shoe and each is only really effective at resisting one direction of travel of the wheel. I would suggest therefore that those which oppose the car rolling backwards require adjustment (or replacement) independent of the leading shoes if that is possible. They needn't have become simultaneously useless since one alone would probably make a decent handbrake. Conceivably the leading shoes only have been replaced at some time in the past since they are the ones which wear most in normal braking? Possibly the trailing shoes have become glazed? Or...

All the foregoing IMHO of course.

Dont IKEA do a wooden door stop that could be adapted?

Thanks very much for all replies. I also got some replies on TOP late last night. These mostly pointed to the linings de-laminating from the shoes: expensive, since they then jam between the drum and the hub and cause all sorts of damage. However, I have looked at the shoes and can see no sign of de-lamination. The easy route I suppose is to just buy new shoes and probably springs too while I'm at it, but it goes against the grain to swap out parts when there's no obvious fault. I noted with interest the suggestion that some after market shoes don't fit properly, and with even more interest the (in retrospect obvious) point that handbrake linings do not bed in with use since they're only normally applied when stationary, and the suggested cure of occasionally gently applying the handbrake while driving (which is also recommended by Haynes).

On the asymmetrical nature of drum brake function, I am sure this is correct since there has to be something physically different happening to account for the difference in directional behaviour. The problem is that there is no way of adjusting the shoes independently: the "expander" pushes them apart at the bottom when the cable is pulled and the adjuster holds them apart at the top, with the whole assembly free to position itself to match the drum. Incidentally, in delving through lots of forums on this (mostly Merkin) I have discovered that the Septics call drums "rotors" and handbrakes are "emergency brakes", shortened to "e-brakes". They also use a term "lug nut" which I have yet to decipher.

I'm tempted to try just giving the linings a good going over with emery cloth and then bedding them in while driving. The counter argument is that there is benefit in putting in new shoes to avoid the potentially serious consequences of losing a lining which, according to various forum reports, does occasionally happen. One poster recommended that shoes over 4 years old should be changed as a precautionary measure (mine are, if original, 15), but did not give any reason for this choice. (I was immediately reminded of 7 year Volvo sail drive seal replacements.) I'm coming round to the view that putting in new shoes might be better (the seeds of doubt having been sown). Thanks again to all who replied.

I had delaminating problems with the handbrake shoes on my old Volvo 940 Estate.
Basically, the handbrake is only put on while stationary, so the shoes don't wear. Mine started delaminating at about 15 years old, and they were hardly worn at all. Fitted new shoes which sorted the problem, and they were still on the car when I sold it at 20 years old.

Never had the "work forward, but not backward" problem though.

Just to add my twa pence worth here.
I used to be a mechanic up until aprox 15yrs ago and at one time worked for JM group at Murray Volvo London rd and Charring x.
Remember that the shoes are not just for the handbrake but also work with the foot brake.
Car brakes normally work on a 60/40 effort, the latter been the rear brakes.
The correct way of adjusting the rear shoe brakes is to first remove the lip/ridge which forms on the inner edge of the drum due to the shoes wearing down the friction surface but missing this ridge.
Using a small hand grinder remove the ridge flush. clean the drum with 40# and take the glaze off the shoe linners.
adjust out the shoes until the drum fits neatly, then adjust externally while ocassionally pulling the hand brake to move out shoes to drum.
The handbrake cable usually connects to a lever which is attached to the top end of the rearmost shoe via a pivot pin and forces the shoes apart using a fore/aft lever when the handbrake is applied.

Check the aforementioned ridge and remove.
Check that the cable pivot lever is free to move when hand brake applied.
The hand brake cable adjustment at the incar lever should be slackened off when setting up show/drum adjustment to ensure the aforementioned pivot lever is fully back against its relevent shoe (rear shoe)
Apologies if I am teaching to suck eggs etc.
C_W

Clyde_Wanderer wrote:Just to add my twa pence worth here.

Remember that the shoes are not just for the handbrake but also work with the foot brake.
C_W

My old Volvo didn't. The foot brake was discs all round, but the rear discs were shaped to make a drum in the middle where the shoes for the handbrake fitted.

I had a Peugeot once that had combined disc/drum brakes at the rear, (drum for the handbrake) and the hand brake was generally useless except for a short time after new disc/drums/pads/shoes/handbrake cable etc were fitted.

With the "shoe expander" at the bottom, the rearmost shoe becomes the leading shoe if trying to stop a car-going-forward-revolving drum, and the forward shoe is the trailing shoe. For a given expanding force the leading shoe is more efficient and does most of the work. (hence in drum brakes the leading shoes wears out more- assuming that braking whilst going forward is the norm!). However when used to stop the drum from revolving at all (as in a handbrake - not an i-brake..er e-brake), the leading and trailing shoes should be just as effective to prevent initiation of either forward or backward rotation.

My guess is that some imbalance or wear is causing the shoe expanding actuator to move the forward shoe out less forcefully than the rearward shoe. So the rearward shoe is working as a leading shoe if the drum rotates forward and is thus efficient, but if the wheel goes backwards the leading shoe becomes the trailing shoe and is less efficient, and so if the other shoe isn't working the wheel has no resistance going backwards. (If you got this far you must have very little else to do...)

Roger

Clyde_Wanderer wrote:Just to add my twa pence worth here.
I used to be a mechanic up until aprox 15yrs ago and at one time worked for JM group at Murray Volvo London rd and Charring x.
Remember that the shoes are not just for the handbrake but also work with the foot brake.
Car brakes normally work on a 60/40 effort, the latter been the rear brakes.
The correct way of adjusting the rear shoe brakes is to first remove the lip/ridge which forms on the inner edge of the drum due to the shoes wearing down the friction surface but missing this ridge.
Using a small hand grinder remove the ridge flush. clean the drum with 40# and take the glaze off the shoe linners.
adjust out the shoes until the drum fits neatly, then adjust externally while ocassionally pulling the hand brake to move out shoes to drum.
The handbrake cable usually connects to a lever which is attached to the top end of the rearmost shoe via a pivot pin and forces the shoes apart using a fore/aft lever when the handbrake is applied.

Check the aforementioned ridge and remove.
Check that the cable pivot lever is free to move when hand brake applied.
The hand brake cable adjustment at the incar lever should be slackened off when setting up show/drum adjustment to ensure the aforementioned pivot lever is fully back against its relevent shoe (rear shoe)
Apologies if I am teaching to suck eggs etc.
C_W

Apologies, I should have replied to this earlier. As Rowana pointed out the Volvo's rear brakes are combined discs / drums with the drum only used by the handbrake. The "expander" is at the bottom and the adjuster at the top. On my previous volvo (740) there was no adjuster, just a fixed bar.

There was a ridge (as I've found with every drum I've ever removed) which can make getting the drum off difficult. It's largely rust and can be removed by scraping with the side of a big screwdriver, though a grinder would undoubtedly be faster. Quite why it develops is less clear to me, given that the shoes are normally only used for parking and don't normally rub on the drum to wear that bit.

Anyway, new shoes are ordered and should arrive in a day or two. Meanwhile I'm off to de-scale the engine then hopefully get a little bit of sailing in before the weather packs in.

Ghillie wrote:I had a Peugeot once that had combined disc/drum brakes at the rear, (drum for the handbrake) and the hand brake was generally useless except for a short time after new disc/drums/pads/shoes/handbrake cable etc were fitted.

With the "shoe expander" at the bottom, the rearmost shoe becomes the leading shoe if trying to stop a car-going-forward-revolving drum, and the forward shoe is the trailing shoe. For a given expanding force the leading shoe is more efficient and does most of the work. (hence in drum brakes the leading shoes wears out more- assuming that braking whilst going forward is the norm!). However when used to stop the drum from revolving at all (as in a handbrake - not an i-brake..er e-brake), the leading and trailing shoes should be just as effective to prevent initiation of either forward or backward rotation.

My guess is that some imbalance or wear is causing the shoe expanding actuator to move the forward shoe out less forcefully than the rearward shoe. So the rearward shoe is working as a leading shoe if the drum rotates forward and is thus efficient, but if the wheel goes backwards the leading shoe becomes the trailing shoe and is less efficient, and so if the other shoe isn't working the wheel has no resistance going backwards. (If you got this far you must have very little else to do...)

Roger

I'm sure you're right, but I can't see what's causing the problem. We'll see what effect fitting new shoes has, although playing "what if" by swapping parts is fundamentally dissatisfying. (Memories of the old TV repairers or "valve jockeys" as they were often called...)

Well I collected new shoes from the post office this morning (£17 on eBay as against £32 in Halfrauds) and fitted them this afternoon. The handbrake now works in both directions, but I'm still totally mystified as to what the problem was. The old shoes aren't de-laminating and don't appear worn, and all the other bits are as before.

On a more satisfactory topic the HCl in the boat engine jacket was very effective: 10 minutes of vigorous fizzing then lots of crud came out as it drained off. Overheating appears to be cured. I think it might be worth doing this as a precautionary measure every few years.

To round off the thread, a lug nut is american for a wheel nut.