whatever they are, they are too soft! But I think I got it right. That's what Tx Spd Wrks does as well. These are early ones out of Webb, bought second hand....

Matt

 

I see!! thanks. Now, what would you say is worst. Bumpstopping or having your springs bind? and Why? They both have the same effect.

 

There's more than one way to answer that, but here's one measure. How did your bumpstops look when you took your fronts apart? One of mine was literally beat to death.....I found 4 or 5 large chunks and a few dozen small bits and pieces under the dust boot. If the bumpstops take only an occasional shot they'll probably be fine, but if they take a regular beating they're going to eventually fail.

 

My bumpstops and dust covers were shredded! Spring bind will not occur if the spring is long enough, and, if it is not super pre-loaded; basically turning an 8" spring into a 6" spring before the weight of the car is on the spring. But if I think about this, and it's late for old folk like me , a 6" spring uncompressed and an 8"spring with 2" of preload do not have the same spring rate, hence the reference to block rates. I will add here that Phil, the guru at TrueChoice, was an absolute as!@#$%#%le when I presented this question to him a while back. He said, "I don't have time for a debate, go ask Eibach!" The point I was trying to pound into his thick skull was yes, all linear rate springs of the same rate posses the same rate at every inch of travel. However, if for some reason we begin with an 8" spring pre-loaded to a 6" spring, its rate has changed, gone up by some amount. so if we compare two struts of identical spring rate, but one is a 6" spring and the other an 8" spring compressed to a 6" spring, the struts are no longer the same rate. If I've performed my calculations correctly, block rate is simple the rate of the spring x the number of inches in travel that spring has. So an 8" spring pre-compressed by 2" is now a 1,125# spring. If you go waaay back and read some of my posts about how to set up the Megans, I was critical about zero pre-load on the springs. And remember, these spring compress by 2" when the weight of the car is placed on them. add another 2" for preload/compressed and it gets worse.
Actually, that's it for an 8" spring; two inches of pre-load and two inches for the weight of the car and there is no more travel left. block height and block rate are important!

So Brownflyer, your question is interesting...I'll check this stuff tomorrow. And palease keep in mind, I'm not an engineer. That's why it reads like it does below; Damn it Jim! I'm a doctor, not a scientist! On the other hand, this is more than likely a lot more simple than it seems...not rocket science just common sense.

 

strictly speaking, the spring rate in a linear rate spring should be a constant. At bind it skyrockets, though.... A rate should be expressed in force per distance.

The numbers you're quoting as "block rates" are really "block forces" ie the force it takes to compress the spring to the point where it locks up.

So the rates in the 6" and 8" would then be the same, but the force required to lock the spring would be different because the 8" can compress more distance before locking than the 6".

But what do I know... That's physics and we're talking cars!

Matt

 

Damn guys!!! if I had your brains and my time...I would be somebody.

So in essence, system permitting, you would be better off having a longer spring than a shorter, higher rate one. Right? Ofcourse this is dependant on the type of setup you're trying to put together, say street/track. If I'm reading the info correctly, a longer spring will provide for a softer ride at initial compression but the rate will shoot up as it reaches "block force".

Now on the issue of bumpstopping, constant bumpstopping will have the consequences of prematurely blowing the dampers and, is there also a lose of dampening capabilities at close to full compression and full extension? Are there any negatives with spring binding (other than the binding itself)?

 

No Doc, you are correct. I've had little sleep, went to check 20 year old notes and everything I wrote above about a spring rate being cumulative is wrong. See, a scientist wouldn't just print something without first verifying it

As Doc wrote, and one can see on charts, the block rate describes the amount of force required to achieve block height - a fully compressed spring. But if we compress a 375#x8" spring to 6" and then install it in the car, it still acts as a 375# spring...in fact it now has the properties of a 6" spring. The rate does not change, only the length of the spring and therefore its available travel.

I apparently posses the thick skull Sorry! But spring length is still important.

 

Thanks for all of the great information. Since Kurvhugr hasn't been bottoming out with a 6" 375# 4mm pre-loaded GC-spec spring, the damper travel is within limits. Excess spring length may not help if travel isn't there.

Following the Dr.'s earlier f/r weight ratio suggestion, I will be trialing rates of 375# GC-spec front/335# rear. I'll post results as soon as possible. Thanks again for the conversation.

 

Those will be my exact rates as well.

As an aside here, after I installed the 469# springs on the front of my Mini, I had a day at Lime Rock. I can tell you that this rate combined with the 335# springs in the rear cost me at least a half second in the uphill alone. The front end of the car nearly left the ground every lap. When this happens, the steering does not work nor does power. I never had a problem here with the original rates. And let me add, this is a very fast group. When you have a radical or various other super cars up your butt going into the uphill, a loss of steering and traction is not a wonderfull thing. Twas another miserable day at LRP.

 

Wow, I hope this works for you guys. I still say there's no one-size-fits-all solution, but a bit of thought and common sense (and maybe even a little math) can go a long way. The thing that puzzles me most isn't the affects of differences between our cars and their diverse setups -- those are known factors -- but the seeming disparity among the coilovers themselves. I still wonder why Michael (meb) has such severe bump stopping that his front bump stops and dust boots are destroyed, while others with the same kit report zero problems and even ask what it feels like when you hit the bump stops.

Oh well, just assume there's no single perfect solution. Warm up those little gray cells, think about your current configuration and the way your Megans work on your car, and try something that seems appropriate. Use my numbers only as a reference point in that process please.

By the way, we all have our "moments" -- you're not alone Michael. I wrote that I have my fronts set at 16 clicks from full hard.....WRONG! I checked again this afternoon and they're at 13 from full hard. Sorry 'bout that brownflyer.

 

So'k, kurvhugr. I've been running my fronts at 16 as you suggested and I'm liking it a lot!!

 

From what I've read, linear rate springs are generally linear between 20-80% of travel. The actual rate will be less for the first 20% and more for the last 20%.

 

I just thought it made sense trying the weight ratio factor, and the fact that only one set of new springs would be required. If I can't reach a happy place with dampening and anti-sway, I can always fall back on stiffer rear springs. I second the hats off to Kurvhugr for finding these springs!

 

kurvhuger and all,

How we drive and where we drive are factors. I drive very hard and the roads in the NE are not great. My 05 also has 81K miles on it...I drive a lot so my exposure to poor road conditions is higher than most.

chuckt,

Never heard that before. Can you comment more?

All,

Apologies again for my comments about compounding rates above. I simply mixed up dual/variable rate characterisitcs...the red wine was especially good that night.

 

Measured my Megan's today. A max of 2.5" piston travel without cutting the bumpstops. Maybe a gain of 3/4" by cutting them and this doesn't leave much of a bumpstop left. Assuming I use a 400# spring, the weight of the car will compress the spring approx. 2" . This would leave a max of 1 1/4" of suspension travel. This seems like a very, very short travel.

 

yup!

 

If you can pre-compress the spring before you set the car on them with the pre-load, you can set the amount the car compresses the piston at rest... This means the amount that the car settles and the stroke are independant.

Also, the 3/4" difference from cutting the bump stops SEEMS like a little bit, but as a percentage of available travel, it's a very, very large change. Go for it!

Matt

 

Like Dr O said, the change in travel from cutting the bumpstops is pretty significant. I had less than 3/4" of piston travel left on the fronts when loaded with the weight of the car, so another 3/4" more than doubles it.

Also, the new bumpstops Megan supplies for the retrofit aren't precut versions of the same bumpstops you already have, they're a different shape/profile, and might even be a different consistency.....not sure about that. Even if you don't want to use their 8kg (469 lb/in) springs, I would still email Steve at Megan and ask for the bumpstops. Then you'll have choices - use the new, cut down the old.....or even cut down the new ones.....whatever.

 

I adjusted my front springs to sit on the very top of the damper, reserving as much spring travel as possible.

 

it's a custom Leda bee-hive. Scribed on it is "MINI 250 lbs Fr". It wouldn't fit on the rear, as it would bump into the chassis (which is a bummer, you'd gotten me thinking I'd screwed up or I could just swap ends....).

I just ordered some stiffer ones for the front. Karl at Racers Edge (does lots of Leda work) set me up with some 6" 325 lb/in beehives. We'll see how that goes and work from there!

Matt

 

does anyone know how the 375 front 375 rear setup works on an MCS? i know there was talk on weight issue.

 

...that is fairly close to stock balance, but quite a bit stiffer.

 

FWIW, I have the 325s on the front of my car now (325 front 350 rear). The suspensions is very streetable, but I'm still working on dampener settings and the like.....

Bottoming happens occationally, but is very rare. The combo of the Hotchkiss camber plates and the stronger front spring is much improved all around.

Matt

 

Do you like the balance Matt? Not sure where you are, but pushing a car in the North East has been a bit difficult - salt/sand and now snow.

 

overall I like it better, but I have to work on dampener settings that are good for both me and my pregnant wife (she's more sensitive to bounces than am I). I think the rear spring/bar combo needs more work as well. Maybe a lighter spring and a heavier bar.... Not sure there.

Overall, the direction the changes are going are ones that I like, but suspension sorting is somewhat new in practice to me, and boy, trying things aint cheap! So I'm going pretty slow here.

Also, my front bushings are shot, and I'm getting all the parts togethter to do the work. I'm just waiting for the front ball joints to show up to do all that. Then it's off for a good allignment and ANOTHER corner balance (I screwed that all up when I changed the springs) and then I'll really know more about the set up.

Short answer is that it's better, but I think I can get it better still...

Matt