has anyone (who doesnt have a bad back) tried buying custom spring rates? I know alot of autox people run Ground Control springs here. I was told by my friend that they give you any spring rate for $200. I am not sure how much truth there is to this, i'll have to look it up. But couldnt you just order some 650lb fronts and 700lb rear with some re-valved koni yellows and be done with it? (cutting the bump stops if needed)

I was thinking about doing koni yellows/ground control springs. But im still not sure what route im going yet.

Anyone tried this, any info?

 

Call Truechoice. They are the only authorized Koni custom builder or re-builder in the country. They offer Eibach springs in just about any rate. http://www.truechoice.com/

Of course, there are lots of questions to ask them and you need to know what you are looking for as well. I went this route with my last car. A custom valved, double adjustable set of Konis with Eibachs will set you back about $2,500.00. I went thru this exercise about 5 months ago. Unfortunately, I waited too long to pull the trigger...the wait was too long at that time. They are typically very busy during the winter getting full race teams ready.

 

wow thats alot of money. I wonder if standard koni yellows will work then. If they will i'll just buy custom spring rates. Although i'd have to find out length/diameter and all that jazz...

I want to lower my car, because i'll have 16's and the gap between the tire and fender is more then i like to see, even with the stardard 1-1.5 inch drop. So the standard aftermarket "sport" springs wont work as they dont drop it enough for my taste. I also want it stiff, my friend has 750lb spring rates in his Civic Si that he autox's and i would assume this would be stiff enough to keep the car from bottoming out?

Only poblem is, im not sure what to tell the spring manufacturers, I guess i'd have to find the dimentions of a spring for the mini and base the modifacations off of it? when telling them how short i want the spring?

This is why i havent picked which route i wanna go, Coilovers make this alot easier but cost more. This requires more thinking and costs less. (i think )

 

Standard single adjustable Konis are at their limit with a 400# spring. A 750# spring is a no go! These will work, but for a very short period of time.

My last set was custom valved with a shortened body, nearly $600.00 per damper. These were mated to 400# springs up front and 600# springs in the rear. I also drove this on the street for a while

 

My friend with the Si drives his on the street also, tweeters in front A pillers have poped out, CD player jamed (wouldnt release the CD) took out CD player replaced it with a flat black aluminum piece, steering column plastic poped off, all due to bumps.

He said hes waiting for the rear subframe to rip out.

calls it a "wear item"



Edit: So would the 400lb spring rates help keep the car from bottoming out? or would it take more?

 

give Dinan a call. They re-valve the koni yellows, and have some linear rate springs. Very nice set up.

$1300....

Matt

 

Doc, is Dinan authorized to perform revalving work? I'm under the impression Trueshoice is the only authorized rebuilder in the USA?

Preventing bottoming is the product of good suspension design. You do not necessarily need a heavy spring to prevent this, just lots of suspension travel. And if your car does touch the bumpstops on the track or during hard cornering, the car will begin to slide at the corner that has lost travel. This will also cause some very weird braking problems; if both front struts make strong contact with the bumpstops during threshold braking, watch out. This happend to me at LRP a few weeks ago while passing a friend deep into turn 1 from the straight

 

glad to hear you made it out of the turn in one piece

 

In a word, no. 400lb/in springs are rated to compress 1 inch when 400lbs are applied, and you can imagine that a 2700lb car can apply a LOT more than that, especially if it catches some air. And that doesn't even take into account leverage because the springs are mounted inboard on lever arms...

This has been discussed before in the spring rate thread: https://www.northamericanmotoring.co...ad.php?t=42546 Bottom line is the bump stops actually function as steeply progressive rate springs--and go to 1000lb/in so you can't expect to ever have springs stiff enough to not need them. The better bumpstops are more progressive in nature.

 

Exactly where I went with the Megan discussion.

A 1000# spring will allow contact if all else is not prperly thought out.

Interesting that you point out leverage BFG9000. The motion ratio will influence how a spring and damper work. Why bring this up? The range of wheel offsets here is from 50mm to25mm - approximately. Since offset affects the motion ratio, it also affects the operation of the suspension and therefore bumpstops. The differences in offset, in otherwise similar setups, can make the difference betwen bumpstop contact or not...rather poor english but you get the notion.

H&R bumpstop link - check it out

http://www.hrsprings.com/site/technical/bumpstop.html


Michael

 

but it's not for end user stuff (unless you have mega bucks, then anything is possible). They do it for customizing the tune of the shocks they use in the suspension packages they sell. Interestingly, they have a "shock dyno" as well to measure damping vs velocity.

so when you buy a Koni from Dinan for the Mini, it has different valving than from Koni. But there is no "price list" for doing one-off shock valving.

Matt

 

I assume they are trying to match the springs they use? I'm actually surprise, enlightened, and, glad to read someone out there cares about this.

 

they modeled the cars suspension geometry, and went from there. That lead to the amount of lowering that can be done. The springs and shock valving come from the ride height.

Really, after having the Dinan car to flog for a weekend, the two best things were how smooth the ECU tune was, and the suspension.

Matt

 

...reads like Dinan's answer to the JCW suspension??? Not too aggressive but more buttoned down?

What do you mean by "not for the end user"? They list Konis on theor web site. Not the revalved type you mention?

 

I think if you order Konis for a Mini from them, you get the revalved units. When I say they don't do end user work, what I mean is that they don't just valve to any spec that someone wants..... So I guess it's an "internal service". But I may be wrong there. Give 'em a call and ask!

Matt

 

Given the subject matter of this thread:

https://www.northamericanmotoring.co...ad.php?t=76049

I'd sure like to get my hands on all those suspension coordinates Dinan determined in order to model the suspension...

Regarding bump-stopping, I will be very curious to see what the kinematics/weight transfer calculations, etc., say about this. I suspect that we will be able to at least get a ball-park idea of the forces involved in making it occur. As mentioned, we can cut the bump stop to gain travel, but those who, in lieu of or in addition to bump stop shortening, want to fashion a gradually rising rate front suspension via the use of an aftermarket bumpstop, determining a desired rate of that "helper spring" should be within grasp.

Or perhaps not -- I'm not THAT far into my reading.

Jeff

 

You get a tape measure, a plumb bob and some stuff like that, and find some flat spot.... Since the car is so low you may want to put it up on ramps.....

Get in touch with John Petrich. He did some analysis with home made measurements and butcher paper....

Matt

 

Powerflex will custom build these for you. Dunno the cost or timing. This is an interesting prospect, but one that is fraught with time and failure - a great teacher, however. And, I suspect, like tuning dampers, that the fanny dyno is still a big part of the process despite the inclusion of proper formulas and calculations.

Check here

http://www.powerflex.co.uk/products....5&submit1.y=13


Doc, how's your math?


Michael

 

but lets face it, if you're hitting the bumpstops a lot, then there a lot to do in the suspension before you worry about the bump-stop itself.... Hitting bump stops should be something that is very, very rare, and also involves surface imperfections (read pot-holes or frost heaves) in the road....

Matt

 

Agreed if we are discussing traditional bumpstops. The purpose of the others - which escaped my attention until fairly recently - is to work directly with the spring. And from what I've been told, they make contact with the top of the dampers while the car is at rest.

 

Why? Isn't that just like having a stiffer spring? sure you can make it so that you get a progressive spring without the hard, sudden shift in spring rates, but I think its a bad idea. The stuff will be lossy as well, so it will interact with the shock function. Seems to me to be a solution to a problem that doesn't exist.

But I've been wrong before...

I'm of the opinion that bump stops should only come into play in the very rare times that needed suspension travel is beyond the design limits of the car. Maybe I'm just old fashioned....

In thinking about this more, the suspension seems like it would be a real pain to sort...

Matt

 

Doc,

This is a relatively new application. The purpose behind these is really quite interesting. When I first heard about these I was very skeptical, but after lots of reading and looking at a few, I'm fairly impressed. Needless to say, er write, these complicate setups because the spring and dampers are tethered together literally.

Check out the H&R link I provided above. When I have time I'll start playing with these.

Up sides:

. Potential dual rate without tender springs and another perch
. Increased suspension travel
. Increased comfort; instead of slamming a bumpstop - not great for dampers - resistence builds gradually ( a relative term here).

 

mostly because of the fact that the instantaneous spring rate and dissipation rates are dependant on displacement. Since all four corners can act independantly, how do you match the action from one wheel to the other? Easy when the car is flat, but challenging when there are lateral loads. Also, unless the are installed partially compressed, as the shock goes to extension, the stop may disengage and you have an assymetric spring design.

Also, the Powerfles site is claiming good benefits on long travel suspensions, something that surely doesn't fit the Mini. But what the hey, if they reduce lap times......

I guess on this one I'll let others be the guinnea pigs! But if they really work, I'll probably be a follow on lemming. I may be stubborn, but I'm not stupid!

Matt

 

Being stuborn is better than stupid

If you read H&R's link, they say these are indeed compressed...or they make that somewhat apparent if not literal.

Regarding all else...understanding how these work is like catching a guy in a race, sort of easy. Getting these to work is like trying to pass the guy you just caught...not so easy.

 

There's always trial and error... I have a far larger selection of bump stops than springs, because I believe they make a bigger difference in handling when travel is limited. If you think about it, you could even do a "corner balancing" by shimming/trimming the bumpstops... when the car is sitting on the bumpstops with no springs installed. That would better approximate conditions under dynamic cornering loads.

The 1st gen Miata at stock height, which used plain old rubber bumpstops rather than the fancy microcellular urethane type, was apparently designed to corner on the bumpstops. Check out the Jan/Feb 1998 issue of GRM for more details.