Lowering - have I gone too far? (Geometry wise)

[pardonthewait]

Hi all,

I've been rebuilding the front end of my Super Minx lately and it's all gone back together - it's the same as it was previously, but I have fitted bump stops that were missing, and also have replaced the top spring pads with Mustang II items that are considerably (15mm or so) thinner than original.

I haven't driven the car yet as I still need to bleed my brakes, but the bottom wishbone is as good as horizontal - maybe ever so slightly over horizontal - and the bottom bump stops are maybe 15mm from touching. The bump stops are on the wishbones themselves (I'll get pictures tomorrow).

I have two questions basically:

1) Because the bump stops are new, I'm unsure how much closer they are now due to the spring pads, but what's the deal with cutting down bump stops or replacing with smaller polybush types? I am not after great handling, I like the look of low cars, and I don't mind driving 'around' the lowness of it, but I don't want a dangerous car. Also is that sort of clearance even an issue? (I presume it is but I'm not knowledgable about this).


2) Geometry wise, are horizontal or over-horizontal wishbones at rest an issue? I like how the car sits at the moment, but I'm prepared to replace the spring pads with the originals if I've gone past a point where I'm going to cause myself an issue here.

The setup, if it helps is as follows:

Super Minx - same front suspension setup as some Sunbeam Alpines, Sunbeam Tigers, Hillman Minx 6/7 I think, and obviously vogue/sceptre

Gaz shocks made slightly shorter than original

-2" springs - made to spec, not cut

2" blocks on rear.

Just after any knowledge from people more experienced than myself really. Should I just bleed my brakes and give it a drive?

[Darkspeed]

It will look sporty and low and long as you drive it with a mind that this is form over function it will do its job admirably.

If you have not actually stiffened the suspension up in any way and have just lowered it all outside of its design operating geometry then I would suggest leaving the bump stops as they are at least you will have a progressive spring to stiffen things up rather than just crashing into a hard stop at every dip in the road. I would almost say get longer bump stops not a shorter ones.

[foxye28]

Anything above horizontal, as in hub higher than inner mount isnt ideal. Id just chop the bumpstops in half to get more travel. If springs are stiffer to go alongside lower then you probably wont hit them anyway

[pardonthewait]

Just took her out for a test drive (re-taxed it to get MOT exemption, still want to get a ticket though as I've sorted everything it failed on) and it's very bumpy. Not at all sure if it's because the shocks are adjusted too stiff, or if it's bouncing off the stops. It does feel like it's doing it at the rear as well though, so I will soften the shocks up and do a few tests, see where that takes me.

Question about bump stops, I've read a few different things. In normal driving, is the car supposed to hit the bump stops, and it be the last part of the travel, or are they a safety thing? Or does it vary with design?

[foxye28]

They are supposed to stop the suspension bottoming out on full compression. I don't think any suspension system is designed to hit them under normal conditions, but they cushion the impact on full compression so you don't potentially lose control by having the suspension suddenly lose all movement with metal to metal contact.

[pardonthewait]

Only reason I asked was that when I started googling I found quite a few BMW E30 I think forum posts, where they mentioned it's actually described as an auxiliary shock absorber on that car, and is kind of designed in as part of the travel. I wondered if this was unique to those cars or common because I'd always assumed it was as you say, designed to actually stop the suspension bottoming out.

Here's the pics and stuff from my build thread:

Jun 10, 2018 10:40:06 GMT pardonthewait said:

After a short test drive settled it in, I could see that the suspension is actually sitting on the bump stops:



So I got them off and went at them with a hacksaw:





Much more room now. I softened up the fronts half a turn, and took two clicks off the rears also, and it drives considerably better now.

Only concern really is the wishbones have settled to over horizontal as you can see in the first picture, however it seems to drive ok so I will see how I go. I'm going to keep hold of the original, thicker spring pads in case I want to raise it in future.

It's much better, probably not ideal but for now I will see how I go.

[foxye28]

that is pretty much identical to how my current 1950 ford looks, and also how close my old aircooled VW ran to the bumpstops, as long as the suspension is stiff enough you'll be fine

[colnerov]

Hi, On modern cars they are part of the suspension system as you say. Back in the 50s for example they are more for a softer contact than a harsh metal to metal. As you have found adjusting the damper setting has changed its drivability so carry on playing with the setting so it compliments the springs.

Colin

[pardonthewait]

Cheers guys I will see how I go and keep making small adjustments.