oop my mistake!

 

The shocks and struts arrvied today:



We're thinking we'll get them fitted in a couple of weeks, after autocross round 1 and MINI Thunder. Then we'll get a Laguna track day and two autocross before we head off to the San Diego tour event.

I'm also convinced that the rattling was the links. No matter what I did they rattled until I put the rubber washers back. Now its quiet again, most of the time. Now its quiet I can hear the other side rattling. I'm going to have to pack that one now.

 

very sweet. please post how they feel once you get them on. they should be far and away an improvement over stock. I actually contacted FCM, and am going with these struts myself

 

Jealous.... VERY jealous!
This is what I wanted. Let us know how they feel. Maybe someday.

 

I asked my friend with the shock dyno to dyno the new dampers. The rear look good, they match very closely, but he thinks there might be a problem with one of the fronts. The fronts don't match nearly so well and start to diverge at high rebound. I'm going to have to ask Shaikh at FatCat about this.

Once I do get the new ones fitted, I'll dyno the stock (sport suspension) ones to see what's different.

 

Shaikh doesn't think its a problem. He blames the narrow shock design the MINI uses for being a bit tricky to balance. Then they put the stiffer shock on the driver's side. If it hadn't been drawn to my attention I probably would have thought they matched (but not as well as the rears).

This description would be a lot easier with a dyno plot to refer to, but Shaikh asked me not to post it.

 

Talking of dyno plots, I've been trying to plug some numbers into Autocross to Win's dynamics calculator: http://farnorthracing.com/autocross_secrets16.html

Whatever I do comes up with plots which are "upside down" from the dyno plots I got. That is ATW comes up with shocks which have a lot more rebound than bump. The dyno plots show a lot more bump than rebound. I don't know if someone's inverted one of the plots, or if there's a different philosophy behind the shocks. ATW's arguments are quite compelling though.

I'm also trying to work out what a dyno plot actually means to someone sitting in a car.

 

interesting.. interested to see any comparo. did u get the kbo option?

 

Btwyx - nice posts. I'm always looking for how different people set up their cars and what seems to work for them.

Just something that I noted when reading thru your writeup. It appears that you are comparing the stiffness of the front and rear bar by comparing the area of the bar. However, when a bar is put into torsion, its stiffness is a function of its polar moment of inertia, which is D^4. The front part in this case is ~191% stiffer than the rear bar. Your bar, at 25mm OD, 17.7 ID, is about 178% stiffer than the 18 mm bar and your front is only about 4% stiffer now. For most steels the modulus of elasticity is basically the same, so that would not be a factor. Also, the above doesn't factor in the mounting points (lever arm length) which provides the adjustability.

Looking forward to your next posts. They are always interesting.

 

My calculations were using the 4th power. If you do the math with 23.5mm, 18mm and 4th powers, the front gets 74.4% of the roll stiffness.

Tarett claim the bar is the equivalent of a 23.8mm bar which gives a stiffness of +205%. They say the adjustability is 2.3x to 5x. (+130% to +400%).

 

We ran Bertie with, the bar on its softest setting, at MINI Thunder on Sunday, which is at Thunderhill raceway. Turn 2 is an interesting test of understeer/oversteer its about a 180 degree semi circle (with a radius of about 90m). Bertie felt quite neutral, he didn't oversteer. I'm not sure I'd actually notice if there were understeer, as that feels normal to me. Certainly just driving around I've not noticed any oversteer, I was worried that there would be lively handling with the new bar even on the street.

Tomorrow, Bertie is getting the new dampers fitted, and this weekend we'll be at Laguna Seca, I'll be running Bertie. I'll see if there's any noticeable difference. I've decided a track day is a good test as you get much more seat time than an autocross without the distraction of competition.

Next will be to experiment with stiffer bar settings.

 

It seems we are saying the same thing but displaying it differently. Sorry for my confusion.

 

Looking forward to reading about what you think of the new shocks.

 

The dampers have been fitted. There was a slight confusion over the front bump stops. The Bilstein front struts are "upside down". That is the piston of the shock is in the strut and the body of the shock is what protrudes from the top of the strut. (See picture from the shop below.) The bump stop is actually hidden inside the strut body, I saw that when the shocks were being dynoed, Shaikh also mentioned it was already assembled.

The shop also did an alignment. I took the opportunity to put some rear negative camber back. The theory being if the rear bar will allow me to shift the car's balance, if I increase the rear grip, I'll end up with more grip total. I zeroed out the toe all around. They couldn't find much negative camber up front though. I might have to try going back to Custom Alignment to see if they can find more.

I also had them look for the clonks and rattles we've been having with the new bar. Everything was tight but they did find evidence of the lower end of the link scraping on the trailing arm. I'm going to have to investigate that.

I didn't immediately notice any difference in handling and wouldn't expect to. Maybe on the track. The steering does feel heavier, I wasn't expecting that.

 

interesting. i would expect at least to note a difference in ride...

 

Which Bilstiens did you put? Sorry if if missed that in your earlier posts.

I would think that on the track you should notice a difference. As shock control dynamic affects, you turn in might feel better. I an interested in hearing how you think it feels this weekend.

 

They turned out to be Bilstein B6 (HD) looking up the part number. FatCat MotorSports have custom revalved them to their design.

 

Difficult to say as I also changed the tires from the RE-11A to the ZII. (Algy's getting the RE-11A, Cathy's driving him this weekend, I'm in Bertie.) If anything the ride is a little harsher, but that could just be the tires. I did say I didn't want a worse ride quality as that wouldn't have a high WAF.

 

bump for anyn updates!

 

Still not found any oversteer. At Laguna I ran three sessions with the bar full soft (and the new dampers). No oversteer. So I set the bar to medium and ran two sessions. No oversteer. Now I've set the bar to full hard, I won't be able to test it fully until the autocross this coming Sunday.

I'm a bit surprised he seems quite so resistant to oversteering.

I did break my JustaCooper track record at Laguna, 2:00.9 not sure if that's due to tires (ZIIs) or the new suspension, or I just managed to nail one lap, my next best lap was a 2:02.4.

 

weird. if i recall your sway bar was pretty aggressive as far as % increase wasn't it? what FSB are u using?

 

Could oversteer have a lot to do with driving style? I have a friend with an '04 Cooper S. 22mm bar and 600# springs on coilovers in the back. You would think that it would oversteer like crazy...Noooo. I was in it when he almost pushed it straight off the track in a 180 deg sweeper. He couldn't even get oversteer by abruptly lifting off the throttle in the middle of that turn. My other S, with a 20 mm bar, Koni FSDs, -1.5 front camber was like an on/off switch with the throttle for under to oversteer. Maybe it has to do with shocks. The FSDs were not happy on the track and didn't have enough dampening. Both my friend and Btwyx have pretty stiff shocks (I am guess about yours Btwyx). But that may explain why there is little dynamic transition from under to oversteer...thoughts?

 

I was a little wary that it was too aggressive. The bar is supposed to be 3x as stiff (23.8mm equivalent), the lever arm is adjustable from 202-118mm vs the standard is 176mm. That gives an adjustment range of 2.66x (+166%) to 4.56x (+356%).

I started at +166% and adjusted it to +249%. Now its set to +356%. I hope that does something.

 

I don't know if the shocks are stiff, they feel about right, but then the old sports shocks feel about right as well. By about right I mean the transient response is good, the car bumps, it settles, that's it, no more rocking. It feels pretty ideal. Also as I mentioned elsewhere, the high speed bump feels digressive. That is the shocks let really big bumps go by without affecting the car much. It makes going over big bumps on the freeway more pleasant.

The driving style might have something to do with it, I'm on the power early after turn in, which would counteract oversteer. I would expect to feel some oversteer when trail braking though, I didn't notice any.

 

are u noticing any differences at all between the 3 settings?