37 replies to this topic

[1968andyf]

No the're longer so can be trimmed by about 3/4" and still be effective.But mine is quite low and i have just trimmed the top to the angle as it hits the subframe and find it works well spax 12points set at 7 clicks recomend you start at 5 andfind what suits you best what size wheels are you using. The other stops i havent used but look just like dry ones mounted an the arm instead on the subframe

[nicklouse]

Be very careful trimming bumpstops, they are the length supplied for a reason.  If you let the suspension travel further than intended you can snap the ball joints when they reach the end of travel.  Poly bumpstops are shorter, but also harder.

You will not beable to go that far on a standard frame. The arm will contact the sub frame before you get to boll joint popping point.

[Spider]

 

Be very careful trimming bump stops, they are the length supplied for a reason.  If you let the suspension travel further than intended you can snap the ball joints when they reach the end of travel.  Poly bump stops are shorter, but also harder.

You will not be able to go that far on a standard frame. The arm will contact the sub frame before you get to boll joint popping point.

 

 

 

Only a couple of weeks ago I had a front subframe on the bench to explore it's limits and what it's limitations were in terms of travel (and what I can do about that).

 

Yes, ball joints are an issue for sure and something that really should be kept in check for sure. What I found when I looked at them surprised me and it may go some way towards explaining some of the broken ball joints we've all seen.

 

Just so we are all on the same page here Rebound is when the hub is at full droop, like say you've jacked the car up. Compression is when the Hub rises, say you've just hit a speed bump.

 

So, I got one fairly straight dry subframe and cleaned it up a little, here, I've got just the top arm in it, but I did fit the lower are and a hub, no Trumpet, Rubber cone, Rebound Stop or Bump Stop.

 

 

 

Rebound

 

So, after fitting the Hub (and lower arm), the very first thing I noticed was that the top arm lifted.

 

 

This was with the hub in a more or less straight ahead position.

 

What I found that was making it rise was in fact the the top ball joint, you can (just) see it binding here

 

 

The lower ball joint was just clear (no binding)

 

 

 

 

HOWEVER,,,,

 

 

 

When turning a corner, it's a whole other story,,,,,,

 

 

This did cause the whole hub to rise, as can be best seen on the top arm here

 

 

The lower ball joint had bound up pretty bad, and this was at not that much of a steering angle

 

Lower Ball Joint binding

 

 

As the hub was 'steered' the suspension rode up the lower ball joint and I have to say, I found it rather alarming just how far it did ride up.

 

This is with stock lower arms. If you've fitted Negative Camber (or adjustable) Lower Arms, this becomes much worse and I can see now very clearly how this would cause lower Ball Joints to snap off.

 

This to me, was surprise No.1.

 

 

Compression

 

In Compression, things are different.

 

This is full Compression (without any bump stop)

 

 

and I found that there was no Ball Joint Binding at all

 

 

Even when steered, there wasn't any ball joint binding.

 

This was surprise No. 2 to me as I had heard a few times that driving with broken bumps stops can cause the ball joints to break. From what I found here, this is not the case, however, if you've fitted different suspension arms (eg, Negative Camber Lower Arms, Adjustable Caster Rods etc) then I'd strongly suggest you thoroughly check for ball joint binding, just to be on the safe side, and it really shouldn't take too long.

 

I'd also suggest we all keep a very close eye on those Rebound Stops.

 

<Edit: Special Tuning gave the advice, in fact, when fitting Negative Camber Lower Arms to fit a piece of 1/8" (3.2 mm) sheet metal under the Rebound Stop, however, they never gave a reason for this, but from what I found here, I suspect it's to help reduce Ball Joint Binding on full Rebound. >

 

Hope this is help to some of you guys.

Edited by Moke Spider, 21 December 2014 - 07:08 AM.

[petey81]

That lower ball joint looks odd.
Good write up though.

[jt19]

WoUldale ball joint spacers on the lower ball joint help this issue do you think?

[racingbob]

 

 

Be very careful trimming bump stops, they are the length supplied for a reason.  If you let the suspension travel further than intended you can snap the ball joints when they reach the end of travel.  Poly bump stops are shorter, but also harder.

You will not be able to go that far on a standard frame. The arm will contact the sub frame before you get to boll joint popping point.

 

 

 

Only a couple of weeks ago I had a front subframe on the bench to explore it's limits and what it's limitations were in terms of travel (and what I can do about that).

 

Yes, ball joints are an issue for sure and something that really should be kept in check for sure. What I found when I looked at them surprised me and it may go some way towards explaining some of the broken ball joints we've all seen.

 

Just so we are all on the same page here Rebound is when the hub is at full droop, like say you've jacked the car up. Compression is when the Hub rises, say you've just hit a speed bump.

 

So, I got one fairly straight dry subframe and cleaned it up a little, here, I've got just the top arm in it, but I did fit the lower are and a hub, no Trumpet, Rubber cone, Rebound Stop or Bump Stop.

 

 

 

Rebound

 

So, after fitting the Hub (and lower arm), the very first thing I noticed was that the top arm lifted.

 

 

This was with the hub in a more or less straight ahead position.

 

What I found that was making it rise was in fact the the top ball joint, you can (just) see it binding here

 

 

The lower ball joint was just clear (no binding)

 

 

 

 

HOWEVER,,,,

 

 

 

When turning a corner, it's a whole other story,,,,,,

 

 

This did cause the whole hub to rise, as can be best seen on the top arm here

 

 

The lower ball joint had bound up pretty bad, and this was at not that much of a steering angle

 

Lower Ball Joint binding

 

 

As the hub was 'steered' the suspension rode up the lower ball joint and I have to say, I found it rather alarming just how far it did ride up.

 

This is with stock lower arms. If you've fitted Negative Camber (or adjustable) Lower Arms, this becomes much worse and I can see now very clearly how this would cause lower Ball Joints to snap off.

 

This to me, was surprise No.1.

 

 

Compression

 

In Compression, things are different.

 

This is full Compression (without any bump stop)

 

 

and I found that there was no Ball Joint Binding at all

 

 

Even when steered, there wasn't any ball joint binding.

 

This was surprise No. 2 to me as I had heard a few times that driving with broken bumps stops can cause the ball joints to break. From what I found here, this is not the case, however, if you've fitted different suspension arms (eg, Negative Camber Lower Arms, Adjustable Caster Rods etc) then I'd strongly suggest you thoroughly check for ball joint binding, just to be on the safe side, and it really shouldn't take too long.

 

I'd also suggest we all keep a very close eye on those Rebound Stops.

 

<Edit: Special Tuning gave the advice, in fact, when fitting Negative Camber Lower Arms to fit a piece of 1/8" (3.2 mm) sheet metal under the Rebound Stop, however, they never gave a reason for this, but from what I found here, I suspect it's to help reduce Ball Joint Binding on full Rebound. >

 

Hope this is help to some of you guys.

 

good stuff

 

so would it be best to fit the poly rebound bushes

 

 

I raced mini 7 in the 70's and car was realy low on the front and historic in AUS

 

frightening eh probably not so bad as car was stiff

[Spider]

That lower ball joint looks odd.
Good write up though.

 

Yeah, that lower one was a bit worn, bit did the job here that I was after.

 

 

WoUldale ball joint spacers on the lower ball joint help this issue do you think?

 

I have been giving this some thought, while I haven't tried them, I actually tend to think it may make the situation of ball joint bind worse.

 

 

 

 

so would it be best to fit the poly rebound bushes

 

 

 

I was actually involved with a Manufacturer of Poly Bushes back in the 80's. I helped them develop a range of bushes & bump stops for the Mini, in design and testing. We even tried a Suspension Cone which was a dismal failure, didn't even make it out of the test area.

 

While those are still very much on the market these days,  I've tried in recent times others that are currently on the market and I've found all these Poly Bushes much the same.

 

So, having said all that, I gotta say, i don't actually like Poly Bushes and Bump Stops at all. They deform quite easily and once deformed, don't 'bounce back' like rubber does. They also crumble fairly easy, especially if the Sun gets on them (probably not a problem in the UK!). I'll also add the while the rubber ones I feel are better, they don't last as long as they should.

[nicklouse]

Now that is interesting. But also shows why I moded my subframe.


Clearance subframe to ground is 100mm woth 20" diameter tyres.

[racingbob]

Yes the minispares ones. The mounting bracket fits on the shock pin i've used them for years.Give about1/2" clearance when adjusting ride height which is about 3/4" lowered using standard cones

so you got standard hydro ones not modified and gives half inch clearance

 

even tho car is lowered 3/4", you have a photo and just check still got that half inch clearnce

[Steve G]

Some really interesting stuff here. I found this diagram which I have used to work out a few things on the Scamp.

 

 

What I don't know is if it takes into account how much the rubber bump stops compress.

[yeti21586]

And where do hydro bumpstops attach? A pic would be great

[nicklouse]

They fit to the top arm over the shock pin.

[1968andyf]

I'll try to get some picturesbut it will be tomorrow night now. Can say i've ever had any ball joint issues though always use the rebound buffer under the arm and keep them well greased

[Steve G]

To make sure you never get any ball joint problems it looks lime it would be a good idea to limit the downward travel with a thicker stop and lower the suspension a bit. 

I suspect that in normal use the suspension rarely goes to full droop can see that you might have a problem when cornering at speed. 

[Spider]

And where do hydro bumpstops attach? A pic would be great

 

This any help?

 

 

 

You will need to drill out the hole in the bump stop, however the holes don't seem to be on the same centres, well, none that I have drilled at least.

 

I now only fit the subframe mounted bump stop if doing a restoration, otherwise, always a Hydro one. I only do this as it makes them much easier to change if one gets broken. On the Off road Mokes, I fit the Competition ones, they are really good.