23 replies to this topic

[Richard_]

Hi.

I recently had a new rear subframe fitted and at the same time I invested in some new Hilos, new rubber springs and adjustable dampers.

The guy who fitted all this was very good and explained that the Hilos had been adjusted as far 'as he dared go' to get the car level when I picked it up.

This was about 2 months ago.

Driving the car this weekend with three passengers and two dogs on some very potholed lanes I was getting an occasional bang from somewhere under the rear of the car.

 

I have a theory that what is happening is that the rubbers have now settled, causing some free play to the spring/trumpet unit as the wheel fully drops. The system then bangs when it closes up again. - on hitting a bump or the exit side of a pothole.

So I plan to adjust the ride height up an inch or so or as required.

I haven't yet measured to see where the ride height is at the moment - but it may well be low. Certainly not high from visual inspection. I want to keep it standard.

 

Excuse my ignorance but is this the likely cause?

- also is there a bump stop to limit downward travel of the hub? or is the damper length controlling this? I see lots of lowered minis around - why don't they have this problem??

Possibly I am totally wrong...any advice appreciated.

 

[GraemeC]

Damper length controls ultimate droop of the suspension.  There are different spec dampers for lowered cars.

 

I suspect your dampers are standard length and they are bottoming out.  Raising the suspension will help.

[slidehammer]

With all those new component fitted I think all that has happened is the suspension has settled and is probably lower now than originally set. on the Hi Lows. It would probably be either the suspension hitting the rear bump stops or the wheels rubbing on the wheel arch lip. You could raise the back slightly or take less weight in the car, if it is fine with only you in it.

[mab01uk]

Also check the rear damper mountings are tight top and bottom and all the rubber bushes look ok, many 'new' rubber bushes supplied for Minis are poor quality these days.....a loose top damper mount can cause banging from metal to metal contact and be hidden behind the fuel tank on one side. (or both sides if you have RH twin tank!)

Edited by mab01uk, 13 June 2022 - 03:11 PM.

[MatthewsDad]

Is it possible that the banging is the exhaust silencer knocking against the subframe, especially if new rubber exhaust hangers have been used? This was the case when I installed a new rear subframe last year. Just a suggestion.

[sonscar]

Best to have a look,if the trumpet or cone falls out the results may not be desirable.Checking beats guessing in my experience,Steve..

[nicklouse]

Lowered car. Needs shocks for a lowered car or a strap to stop the suspension moving too far.

 

it is currently dangerous.

[Spider]

This again highlights another reason why I don't like fitting Hilos on the Rear Suspension - you need to keep careful track of how long they are set compared to a stock Trumpet.

There is a Bump Stop in the Rear Suspension in Dry setups. It's not obvious and frankly, I feel it's a super poor design. I actually cut them out. The Raised pressing in the Subframe that the Rubber Cone sits over is the Bump Stop. When the Cone is compressed far enough, it contacts the Subframe here and it's only the thickness of the solid piece of rubber that the Cone has here that gives any coff coff, cushioning. With stock Rear Shocks, it's just after that point that they will bottom out. After a few hits on these Bump Stops, the inner stub of the Rear Trailing Arm Pin shears off. Keep in mind here, that there's 5 times the weight of the back of the Mini (including what ever you have in it) coming down as force on that Pin (and the stub).

When running Hilos in the back, you can extend the total length here about 1/8" longer than stock in a saloon and that's about it. Any longer and you'll be hitting this Bump Stop often.

I would suggest removing the Hilos from the back, extend them on the bench to match the lengths of stock units, then count the turns or number of threads exposed or some other way of marking them, so when fitted, you know where you are at with them.If they are a type that uses a Bolt, measure how far out of the main body the bolt is hanging out.

[imack]

There is a Bump Stop in the Rear Suspension in Dry setups. It's not obvious and frankly, I feel it's a super poor design. I actually cut them out. The Raised pressing in the Subframe that the Rubber Cone sits over is the Bump Stop. When the Cone is compressed far enough, it contacts the Subframe here

When I bought a genuine Mini Special wheel arch kit from Austin Rover in the 1980's it came with a mushroom shaped bump stop extension piece that was to be fitted into the subfame bumpstop hole used by hilo adjusting Allen key an was retained in the subframe by pressing a starlock washer over the shaft of the bumpstop.

[GraemeC]

 

There is a Bump Stop in the Rear Suspension in Dry setups. It's not obvious and frankly, I feel it's a super poor design. I actually cut them out. The Raised pressing in the Subframe that the Rubber Cone sits over is the Bump Stop. When the Cone is compressed far enough, it contacts the Subframe here

When I bought a genuine Mini Special wheel arch kit from Austin Rover in the 1980's it came with a mushroom shaped bump stop extension piece that was to be fitted into the subfame bumpstop hole used by hilo adjusting Allen key an was retained in the subframe by pressing a starlock washer over the shaft of the bumpstop.

 

 

Same as these?

http://www.minispare...|Back to search

[Spider]

 

 

There is a Bump Stop in the Rear Suspension in Dry setups. It's not obvious and frankly, I feel it's a super poor design. I actually cut them out. The Raised pressing in the Subframe that the Rubber Cone sits over is the Bump Stop. When the Cone is compressed far enough, it contacts the Subframe here

When I bought a genuine Mini Special wheel arch kit from Austin Rover in the 1980's it came with a mushroom shaped bump stop extension piece that was to be fitted into the subfame bumpstop hole used by hilo adjusting Allen key an was retained in the subframe by pressing a starlock washer over the shaft of the bumpstop.

 

 

Same as these?

http://www.minispare...|Back to search

 

 

They were factory fitted in the Mokes from about 1969;-

 

They seriously got this quite mixed up. Fitting the Stop causes Major Damage;-

 

 

[imack]

Same as these?
http://www.minispare...|Back to search[/quote]

They're the ones

Edited by imack, 14 June 2022 - 08:43 AM.

[Richard_]

Damper length controls ultimate droop of the suspension.  There are different spec dampers for lowered cars.

 

I suspect your dampers are standard length and they are bottoming out.  Raising the suspension will help.

Thanks everyone for the advice.

Yes so the car has effectively been lowered and I am using standard length dampers. With all those passengers it seems possible that the dampers are bottoming-out when I hit a bump.

I will check and reset the car to standard height at the weekend. Hopefully that will do the trick but I'll monitor the situation.

[nicklouse]

 

Damper length controls ultimate droop of the suspension.  There are different spec dampers for lowered cars.

 

I suspect your dampers are standard length and they are bottoming out.  Raising the suspension will help.

Thanks everyone for the advice.

Yes so the car has effectively been lowered and I am using standard length dampers. With all those passengers it seems possible that the dampers are bottoming-out when I hit a bump.

I will check and reset the car to standard height at the weekend. Hopefully that will do the trick but I'll monitor the situation.

 

If bottoming out then changing shocks will not change a thing. Changing your ride height would be the fix.

 

I don’t think bottoming out is your issue .

[Spider]

 

Damper length controls ultimate droop of the suspension.  There are different spec dampers for lowered cars.

 

I suspect your dampers are standard length and they are bottoming out.  Raising the suspension will help.

 

Thanks everyone for the advice.

Yes so the car has effectively been lowered and I am using standard length dampers. With all those passengers it seems possible that the dampers are bottoming-out when I hit a bump.

I will check and reset the car to standard height at the weekend. Hopefully that will do the trick but I'll monitor the situation.

 

Ah, since it has been lowered, then it would more than likely be the dampers bottoming out.

Some will take this OK and others it can damage them internally.

Shorter shocks should sort it.