The thicker sidewalls on 15" tires absorbes the bumps a lot better then 17" tires. Iv'e driven both and there is a big difference.

 

i did lower the back a little more in the rear as i wasnt worried about rubbing back there as much. Maybe that does help??

In terms of sidewall....that my be true for most 15s, but with the tire size i selected i only have .2 inches more sidewall than the average 17 inch wheel setup

 

Your sidewall height should be about 102.5 mm. The sidewall height on a 205/45x17 should be about 92.25 mm. Thats a pretty big difference in terms of the tires absortion ability.

 

fair enough...i was using 215/45/17 which is .2 inches

but with 205/45/17, you're right its a .4 inch difference

 

I like the look of the flatter ride height. If these things ever get the bottoming problem solved, I plan on setting the ride hieght flat like yours (RallyMINI) and running an H-sport Comp rear bar on the middle setting to improve the cornering traction in the front.

 

All the little things starte to add up! I am guessing its the set up that makes the difference on bottoming or not bottoming.

 

but wait

Sid -17 inch- doesnt bottom out
Steve-16 inch- bottoms out
Me- 15inch- doesnt bottom out

 

I'm not so much intrested in the height of the tire but the amount of sidewall. The more sidewall, the more the tire will absorb and the less violent the impact.

 

The angle of attack of the car will have a pretty noticable effect on the way the energy is transfered through the suspension... so that might be one aspect.

Right now I'm using two different size rims... lame, I know. But the OEM Mini wheels are sooooo weak. Went for a drift session at Irwindale Speedway while we were setting up the course and after that, one of my front rims was warped. I didn't even hit anything!

The rear of my car is a little lower than my front.. sucks for acceleration, but I believe it's also making bottoming out a little less violent. Here and there, even with 160-8kg springs, I still get a good smack once in a good while.

 

Geez, this is a fast moving thread lately!

With regard to bottoming: I'm at the track a lot and so the suspension is being pushed thru every turn. The combination of speed acting with braking, turning and accelerating bring out the best and worst in any suspension setup. I simply looked for other solutions for most of the summer because I did not suspect suspension travel. In the past while working with Truechoice and Koni for example, I invested a fair amount of time working with spring rates and valving, and, stroke length. Koni's Phase Four kit provides custom valving with double adjustable dampers. The difference here is that the springs are made by Eibach, the coiloversleeves by Ground Control and the Dampers by Koni. So I had to make sure that all these components worked well together. And they did - the custom valving was a big part.

But I digress . If you are running these at the track only, go with the 8kg/mm springs front and rear. The next rate unfortunately is 6kg/mm - no 7kg/mm springs. however, you can call Eibach or Truechoice and order a pair of 7kg/mm springs in the same length and diameter. 6kg/mm, in my opinion is a fine rate for street/mild track. 7kg/mm gets a bit more track oriented as does the 8kg/mm.

Just make sure that your springs are adjusted as high as possible on the front cylinders in an effort to retain as much travel as possible. If your car is a track only car, you might be able to order springs that are a bit shorter; remember that when a spring is compressed, its rate changes.

Also, with regard to ride height: ride height determines weight transfer. Roll centers (RC) and the centers of gravity (CG) form a relationship known as roll couple. Some setups will cause more weight transfer onto the front wheels during a manuver, some cause less. A typical track setup technique for many cars is to lower the front more so that roll couple is incresed - the greater energy acting on a lowered RC in turn acts with a greater force on CG and therefore causes more roll. This is a valuable tuning technique, but one that may also explain why a few of us have bottoming complaints while others do not, in addition to the driving venue noted above. This technique, by the way, reduces understeer by helping the car to rotate.

 

I think I'm going to try 375lb/in front and back (that's ~6.7kg/mm if I'm converting correctly).

 

...so you're going with an Eibach then? If I remember, there are some limitations but the incriments are 25#. So a 350 or a 375 will work...which basically feels like a nice set up - 350#front and 375# rear.

There are a few folks who like really big front rates, but you must look at their setup - almost wrote package...coulda been scary . In particular, as a track setup, I know a few guys who run with a 23mm offset on the front wheels and 33 on the rear. This is achieved with wheels and spacers. The point here is that the spring rates are no longer 500# for example because cantilevering the wheels is really the same as changing motion ratio - the springs and dampers become less effective. But, they NEED those rates to retain the roll and weight transfer characterisitics they desire with a 23mm offset. This is a great way of lowering the center of gravity...it changes role centers a litte because the instantaneous centers move with the tire's centerline. But, spring and damping rates change.

 

H&R lists the best range of 6x2.5" springs that I've found, including 7kg/mm(400lb/in).

http://www.hrsprings.com/site/motorsport/250.html

I haven't called to check stock though.

 

Yah, i was just making the assumption that a 17 would have the least sidewall and the 15 would have the most sidewall...

 

Yup, Eibach. The fronts are actually a Ground Control spec version.....as far as I can tell the only difference besides color is that they're slightly barrel shaped.

With my 16x7.5 +42mm offset wheels and 225-45 tires, there isn't much room for spacers, but I have a set of 5mm I'm going to try.

 

yeah, im not sure what im going to do just yet. i do have to keep the slammed look for shows so, i may run into some problems there but, i also may be upgrading to 19s' so we will see what happens.



ps. thanx steve for gettin those out to me.

 

19's ouch. I'm quite content with my 18s... And with the current commute in DC (though it will be loads better in Guam), I couldn't imagine motoring with 19s.

 

Camber angles and ride height can help or hurt. I can tell you that I have zero clearance problems with 33mm offset with barely a 1" drop and 2 deg. neg camber. Lots of room. But those 225s may present a problem. You may find a smaller tire/wheel combo works better with a smaller offset than a wider tire and larger offset. When the center of gravity is lowered, less damping is required and I would all suspect, that less tire is need for a given level of grip. The balance here is a decrease in aero with a narrow tire - not insiginificant at high speeds.

 

I've started the retrofit on my own - this isn't difficult at all! I don't know what I was so worried about and I can't believe I paid someone else to install them in the first place!

Anyway, I need a bit of advice. When reassembling the struts, should I lube or otherwise coat the threads on the outside of the strut body? It looks like my installer greased them with something to keep things mobile, but it attracted a lot of grit so I had to clean the threads before adjusting the perches, etc. The grease (or whatever it was) is gone now and I'm just wondering whether there's any benefit to adding a thin coat of antiseize or something before putting them back on the car.

tia

 

When I originally installed the coilovers, I used a bit of WD40 to make it easier to adjust but after a while the dirt stuck to it and it made it more difficult to make any adjustments. This time around, I just cleaned them out really nice and left them as is. So I would suggest not to put anything on there. BTW, I haven't had any issues with the adjusting nuts loosening up.

 

Yah, you don't really want the suspensions to be "mobile". It'll cause the rings to come loose and that gets annoying cause they rattle.

If you have a hard time rotating the strut body, then one tip I can give you is lock the two Pre-Load rings together and then if you need to raise the suspension then use one of the wrenches on the bottom of those two rings. And if you need to lower the suspension then use a spanner wrench on the top of those two rings for a good grasp.

WD-40 is cool, but wipe it down after everything is done. That'll usually help prevent too much dust build-up on exposed parts.

 

...and lubricating these just causes dirt to cling to them. I agree with Steve, WD40 or Rust buster, but wipe it all off after.

While on this subject of lubricating, do not lubricate nuts/bolts that are torques sensitive; most lubricants allow the nuts/bolts to be torqued to higher values causing over-stretching and failure. There are protective lubricants that work specifically for torque sensitive components available.

Just thought I would throw that in.

 

I figured as long as I didn't NEED to do it I wouldn't. Aside from the grit attraction biz, those locking rings tend to loosen up all by themselves - don't need to give them any help.

Thanks guys.

 

There are some good bicycle chain lubes that don't attract dirt.

 

...Pedro's...nice stuff. They also make one that is so tacky it attracts asteroids