2005 R53, with KW v1 coilovers.

My back end, rear shocks bottom out on bumps, not even very large bumps. I'm thinking I need springs with a higher spring rate.

Any suggestions on rate and vendor for proper springs from the forum?

 

Your coilovers are adjustable. Sounds like they're too short.

 

+1 this is what happens when coilovers are all the way down or "slammed" look on MINIs. You hit a bump on the fronts and they can bottom out easy. The factory shocks on MINIs dont have much travel compared to other Makes.
Also when you dampen out the rear all the way and go over huge bumps it will do the same and i have seen people rub the wheel arches and knock them off. Some people even shave the arches in the rear. Its that low life. lol Ask a VW owner.

 

gents, lowering the coilovers does not compress the spring, the travel is the same. The car is lower but the travel is the same.

I'm going to get it up on stands and look more closely.

maybe the shock is bottoming out, not the spring?

I'm also communicating with KW to get ideas and the spring rate for this kit.

Note: I don't have any tire rubbing issues. Stock mini 17inch rims

 

Anyone know the rear spring rate on the stock S suspension?

 

I did some digging before I bought my coil overs.

Basic Numbers: (from what I've found please correct me where I'm off)
Stock R53 spring rates are in the 4k front & 2.5-3k rear range but PROGRESSIVE
Rear motion ratio is around 0.87
Curb weight of 2,853 (with driver) and 62.7/37.3 weight distribution.

 

Yes, this is what we're saying. It's a direct result of the ride height being too low.

 

3k translates to 168 lbs/in. so that seems in line. thank you sir

https://eibach.com/spring-rate-conve...ZqI1vkptY5smHZ

 

roger that. they are set low. going to try and lift them a bit and see what result that yields

 

Part of my install on the Fortune coil overs was to remove the springs completely, take my floor jack and push the wheel/tire up into the wheel well and see what hit first: bump stop or the tire hitting something.... a simulation of what's going to happen when the tire hits a bump and goes to full compression.
The other benefit of this is you can actually see what the full travel is. From full droop to full compression... and you can measure it. Then you can drop the car (with the spring back in) and see where your ride height sits relative to your full droop and full compression.

What I should have done is pulled my springs from my Koni struts and measured that BEFORE I replaced them with the Fortune Coil overs. My gut tells me I have less when it comes to full travel because the FA coil overs are designed to be lower. The adjustable lower perch means the actual strut is shorter etc... There's no real way to avoid it when lowering the car.... you need to hit the bump stop before the tire hits the car... the tire is closer to the car when it's lower. Can't have your cake and eat it too.

I went with 6K front and 6K rear Swift springs. You can read more here.
https://www.northamericanmotoring.co...nd-review.html


Here's some links that I found very interesting.
https://www.northamericanmotoring.co...nd-tuning.html
R56 but still applicable.
https://www.northamericanmotoring.co...on-travel.html

Track setup:

 

that sounds spot on @bump32

im going to do some reading / watching

 

A note: the KW v1 set does not have an adjustable shock housing / body. It allows for the springe to be raised or lowered. that is it.

so i basically have two options, (1) raise the spring, and if that does not do it, (2) get a spring with higher spring rate.

Planning to take a closer look this weekend, hopefully

 

That is how the Bilstein B14 coilovers on my car are. I do not have any bottoming issues since installing this suspension, however.

 

^^^+1
Same here - I also ride on B14's. Not that is of any help.
Notwithstanding:
I've recently traveled cross country/over 4,000mi, my Mini loaded down w/800+ lbs of parts, tools, etc, B14's set lowered 1"- 1.5" just above top of the tires. Squatting the Rear camber but never bottomed out the springs.
Although I did eventually have to dial up the rear ride height in effort to curtail wearing out the inside edge of the rear tires...until I could finally offload all that stuff into storage.
But I still, often, wonder how much all that weight may have had a negative impact on the dampers/shocks.

 

over the weekend I lifted the springs. I'm at 16 threads from the bottom of the shock to the bottom of the adjuster. as a reference to anyone with kw v1's. the springs just start to compress there. so I stopped.

the wheel arch is right at the top of the tire now.

tested it and no more bottoming out.

while I had the wheels off I discovered the source of the banging sound. the trailing arm was hitting the frame. I'll post some pics. the bump stops are smashed.

Also found what is think is the spring rate on this kw kit, 40-200 lbs/in progressive, I think. post a pic of that also. so very close to stock if that is right.

 

 

so the question remains. what's the right spring rate?

these calculations:
I'm sure someone has these numbers for the r53

 

Is the spring rate comparison apples-to-apples given that the stock suspension has huge progressive bump stops? I’ve never really thought about it that hard since I’ve never entertained swapping to coilovers.

 

two separate things. Spring rate can be compared apples or oranges. bump stops can be compared apple or oranges.

ideally you would want a spring rate that would not allow the bump stop to be used (except for maybe in extreme circumstances)?

the bump stops on this kit dont seem to have held up very well. is that a poor quality bump stop or an incorrect spring rate?

ive read somewhere that you would want a lower spring rate in the rear. that helps the car not turn into a seesaw.

 

Welcome to the rabbit hole.... Spring rates are a very interesting topic and there are a ton of different opinions.... start mixing in sway bars and you're going to have goooooood time.

I found this video pretty interesting as starting point.

 

My understanding is that the factory bump stops were actually intended to, in effect, alter the spring rate (the car basically corners on the bump stops). In contrast to say, my van, where the bump stops are a hard rubber limit, and hitting them would lead to a very dramatic (and rather exciting) rapid increase in effective spring rate. The bump stops on your coilovers look like the more hard-limiting kind. Hence my question. Not sure I follow what you mean about apples or oranges.

Edit: This explains essentially what I was thinking of.

 

thank you, sir. I'll watch this tonight

 

i think we are basically saying the same thing. although ive never heard that about the stock bump stops.

I'm looking for a spring rate that will not allow bottom out and a stop that will not fall apart.

KW says they will send me new ones for $9 each. But i'm hoping i can do better. I'm hoping someone has found a better way

 

that was very informative. thank you again for posting.

basically if we know;

-car weight
-frequency (1.5 to 2 hz for a sporty suspension)
-motion ratio (in front and rear)

we can calculate spring rate.

 

Rear motion ratio is around 0.87. Not sure if the front has a motion ratio.
Curb weight of 2,853 (with driver) and 62.7/37.3 % weight distribution.
I started to do the math on this but never finished. Let me know what you figure out.