Rear End Lift

Post by **Tim Leech** » Tue Feb 28, 2012 1:21 pm

Apologies if this has been covered a million times afore, noticed yesterday driving the TZI that the rear end has a tendency to lift up slightly when braking.

Since Ive had it ive replaced rear arm bearings and spheres all round etc.

adamskibx · Post by **adamskibx** » Tue Feb 28, 2012 1:32 pm

I would imagine it's because the spheres are very soft, or that the rear brakes are not biting hard enough. The rotational force created by the rear brakes should compensate for the weight transfer due to the trailing arm arrangement.

Post by **Tim Leech** » Tue Feb 28, 2012 1:45 pm

The rear end is nice and soft, but then again the GT is but that doesnt so it, wonder if its the rear brakes that arent working properly and may need bleeding?

Dollywobbler · Post by **Dollywobbler** » Tue Feb 28, 2012 2:18 pm

It is an auto isn't it? I wonder if it's because an auto is always trying to power the front wheels. Doing so will tend to push down on the rear suspension if the wheel cannot rotate because it is being braked. For a really good demonstration of this, note how the back of most front-wheel drive cars will sink to a huge degree if you've still got the handbrake on. I know the BX is slightly different as it has a front handbrake, but I suspect the physics is the same. If the back end is being pushed down, the car will compensate by raising the rear suspension. When the braking effort goes, the back end could then bounce up until it settles back down to normal. Just my theory!

Post by **Tim Leech** » Tue Feb 28, 2012 2:31 pm

Could be, yes it is Auto, also it seems like the brakes have a tiny bit of travel before they bite, and then they bite hard.

Cheers.

saintjamesy89 · Post by **saintjamesy89** » Tue Feb 28, 2012 2:54 pm

Lol, I started to write something really smutty and innapropriate about 'rear end lift', but then I made myself blush and decided not to

Mickey taker · Post by **Mickey taker** » Tue Feb 28, 2012 2:57 pm

I thought about having my rear end lifted once but gravity decided otherwise

is there not a brake bias valve on bx's that balances out front/rear braking ?

saintjamesy89 · Post by **saintjamesy89** » Tue Feb 28, 2012 3:12 pm

Bugger it, smut alert! One could apply the technique of 'rear end lift' to many things...

Post by **Tim Leech** » Tue Feb 28, 2012 3:30 pm

saintjamesy89 wrote:Bugger it, smut alert! One could apply the technique of 'rear end lift' to many things...

Can we keep a post on topic, just this once!

Mickey taker · Post by **Mickey taker** » Tue Feb 28, 2012 3:32 pm

Roverman wrote: Can we keep a post on topic, just this once!

thats a bit hopeful Tim

Post by **Tim Leech** » Tue Feb 28, 2012 3:43 pm

Mickey taker wrote:
Roverman wrote: Can we keep a post on topic, just this once!
thats a bit hopeful Tim

True but no doubt the topic of conversation will divert to something else and I will still be none the wiser!.

saintjamesy89 · Post by **saintjamesy89** » Tue Feb 28, 2012 3:48 pm

Sorry Tim, I'll try and make a concerted effort. But, sometimes, I just can't help it.

Post by **Defender110** » Tue Feb 28, 2012 4:23 pm

Although you have replaced the spheres you probably still have trapped gas in the system that has escaped from the old spheres and you need to re-bleed your brakes to get it out. When mine did this it was a definate lift after stopping as though I had deliberately raised the rear end suspension?

Post by **Tim Leech** » Tue Feb 28, 2012 4:28 pm

Defender110 wrote:Although you have replaced the spheres you probably still have trapped gas in the system that has escaped from the old spheres and you need to re-bleed your brakes to get it out. When mine did this it was a definate lift after stopping as though I had deliberately raised the rear end suspension?

Thats what this does, the rear end lifts up by a couple of inches then settles down again when I lift of the brakes. If I brake gently it doesnt do it. How easy is to bleed the brakes? I confess I havent ever changed the LHM on it.

Post by **Defender110** » Tue Feb 28, 2012 4:41 pm

Roverman wrote: How easy is to bleed the brakes? I confess I havent ever changed the LHM on it.

Depends if your bleed nipples undo easily, mine did but they hadn't been tampered with or overtightened in the past. Use a six pont spanner or socket to initially free them off to prevent rounding them off. You need to take your rear wheels off to get to the nipples and put the hubs on blocks to simulate the wheels being on the ground. Once you've cracked the nipple put a little rubber tube on the nipple and bleed it into a bottle.