Too much body roll. Why? Is there a solution?

[TagMan]

Originally Posted by ersatzS2

Interesting article in the current issue of 'Sportscar' (SCCA's magazine) by Randy Pobst, possibly the best/most successful sedan racer in the US. He describes how he likes his cars sprung as softly as possible, and says many racecars he tries are too stiff, (and seem to get stiffer the closer they get to Stuttgardt) When the springs are too stiff, he says, it leaves only the tire sidewall to absorb changes in cornering loads. This overheats and overworks the tire sooner than if the suspension had a more progressive loading. I thought that was kind of a nice iconoclastic insight relative to conventional wisdom...

Good post. That's a very interesting perspective. In the case of the 135i, I personally would like a little less body roll, but not at the sake of an overly harsh ride, although I would be more than willing to sacrifice some of the tire's lifespan.

[mprhead5]

rarly is a softer front bar the way to go. a stiffer front bar can improve turn in but will result in more understeer at higher speeds.
A rear bar change can make all the differance especaly if it was one of the things traded off by the engineers in an attempt to make the ride more comfortable. an adjustable rear bar will most likly help but I always sudgest tracking the car stock to get a baseline Idea of how the car behaves so you can tell what kind of effects the new parts are having and what parts need to be addressed. If you just change the bar based on what you feel while street driving you could end up overdoing it and find your rear end sliding out on fast sweepers.

You really need to ge the car up to speed to accuratly measure handling dynamics. That means track day. Not autocross but TRACK. at autocross speeds wou won't be able to accuratly judge the effects of the change. For instance the added turnin from a stronger front bar will help in the slow tigh autocross but you may find the overall handling limmit at full speed to be reduced.

go and buy some books on suspension tuning so you will know how to Identify handling charicteristics and what you can do to change them. I have a great one with a honda prelude on the cover called "How to make your car handle" I think

[Bionic]

OK, I find this funny... The fiancee and I were at an HPDE last year at Mid-America Motorplex (near Omaha). There was a screw-up in scheduling, and K-Pax racing was there to test their 911s for the Speed GT Series. Randy Pobst and Michael Galatti were both testing. We alternated, 1/2 hour for the Schmoes, 1/2 hour for the Pros.

My fiancee (in her Miata) was talking to Randy (big Mazda guy, even was in their "more Mazdas race on any weekend" TV spot) about her car. Its a Miata with aftermarket turbo, suspension, brakes, and so on. Normal weekend trackday mods. He then asks to take a spin in it. She, of course, grabs her helmet and hops in the passenger seat.

He does one full lap BAREFOOT (he was wearing flip-flops (!?) in the pits and didn't want to drive in them). He was, literally, heel-toeing with his heels and toes. He was faster by 2 secs a lap, in one flying lap, barefoot, in a totally unfamiliar car, than we were all day long, at a track we know, in our own freakin' car! This is why he gets paid to do this, and we pay to do it.

When he got out of the car, he said it could use more rear roll stiffness.

We then, politely, asked him to sign the center console of the Miata. He was happy to do so. He was nothing short of polite, nice, friendly, and willing to share his experiences with us while at the track. He just wanted to hang around and chat when he wasn't driving his own car.

The only reason I posted this is that I find his comments above, which I do not doubt at all, sort of ironic. The only time we've met him, he told us the opposite of what you've said.

Of course, he was talking race cars, and our Miata is streetable, even with some of the stiffest aftermarket springs around...

Either way, how cool was this????

Phil

Attachment 6152

[Doolab]

Here's a nice table that highlights suspension tuning... Enjoy :smile:

http://www.turnfast.com/tech_handlin...ingtable.shtml

[MZWIE]

I had the car on the lift last night looking at the suspension. On the rear you can't replace the sway bar w/o dropping the diff.

The bar is routed over the top of the diff. I had never seen this before. Looks like a PITA.

[MINI135i]

[quote=Bionic;118795]OK, I find this funny... The fiancee and I were at an HPDE last year at Mid-America Motorplex (near Omaha). There was a screw-up in scheduling, and K-Pax racing was there to test their 911s for the Speed GT Series. Randy Pobst and Michael Galatti were both testing. We alternated, 1/2 hour for the Schmoes, 1/2 hour for the Pros.

My fiancee (in her Miata) was talking to Randy (big Mazda guy, even was in their "more Mazdas race on any weekend" TV spot) about her car. Its a Miata with aftermarket turbo, suspension, brakes, and so on. Normal weekend trackday mods. He then asks to take a spin in it. She, of course, grabs her helmet and hops in the passenger seat.

He does one full lap BAREFOOT (he was wearing flip-flops (!?) in the pits and didn't want to drive in them). He was, literally, heel-toeing with his heels and toes. He was faster by 2 secs a lap, in one flying lap, barefoot, in a totally unfamiliar car, than we were all day long, at a track we know, in our own freakin' car! This is why he gets paid to do this, and we pay to do it.

When he got out of the car, he said it could use more rear roll stiffness.

We then, politely, asked him to sign the center console of the Miata. He was happy to do so. He was nothing short of polite, nice, friendly, and willing to share his experiences with us while at the track. He just wanted to hang around and chat when he wasn't driving his own car.

The only reason I posted this is that I find his comments above, which I do not doubt at all, sort of ironic. The only time we've met him, he told us the opposite of what you've said.

Of course, he was talking race cars, and our Miata is streetable, even with some of the stiffest aftermarket springs around...

Either way, how cool was this????

Phil



What is the exact set up (especially spring rates and bar size) of your miata just for reference as I would like to see what Randy's comment applied to?

Couple years back I ran a 1994 MP62 supercharged miata with 350 rear and 550 front springs/GC coilovers with koni yellows. Big 1 inch front bar and no rear sway at all. Absolutely loved the set up.

Thanks.

[ersatzS2]

Originally Posted by Bionic

We then, politely, asked him to sign the center console of the Miata. He was happy to do so. He was nothing short of polite, nice, friendly, and willing to share his experiences with us while at the track. He just wanted to hang around and chat when he wasn't driving his own car.

The only reason I posted this is that I find his comments above, which I do not doubt at all, sort of ironic. The only time we've met him, he told us the opposite of what you've said.

Of course, he was talking race cars, and our Miata is streetable, even with some of the stiffest aftermarket springs around...
Attachment 6152

It is amazing how many posts like this I've seen on message boards over the years regarding Pobst. I once stayed at the same B&B with him at Mid OH and had him alone for breakfast. He was unbelievably open and accessible. He was driving for Audi at the time and this was a quattro club track day. All day long he gave rides in student cars.

Re: his comments on suspension stiffness- I think the audience he is addressing in SportsCar is frankly so different than those of us driving street cars that his comments don't have much relevance. No one is driving a car hard enough for long enough on the street to overwork the tires. I just passed on the quote as a way of stirring the pot- my bias is that folks go way overboard with all the lowering and stiffening stuff. This way I can leave my suspension stock and take the high ground "I'm just practicing better tire management..."

[adc]

Originally Posted by ersatzS2

my bias is that folks go way overboard with all the lowering and stiffening stuff. This way I can leave my suspension stock and take the high ground "I'm just practicing better tire management..."

Are you making the case for something like Bilstein's Ride Control system?

[Bionic]

Hey there,

Mini135 - The Miata setup in question is something like 440 lb/in springs up front and 360 lbs/in rears with KYB adjustables. 26-mm front and 20-mm rear bars. Not a coil-over setup by any means. Yes, I know it is an apples-to-grapefruit comparison with any pure race car, I just found it funny in light of this thread.

As for Pobst, he was absolutely just a "regular guy" hanging out at the track. When not put in his car (by the manager/handler person) he was walking around, asking about people's cars, their track experience ("I lost it in the Kink at Road America once. I don't recommend it...") and just being a wonderful car guy. I think if he didn't get paid to do this, he'd be out there anyway. He was very different from the "hide in the motorhome" type driver.

It's been my experience at tracks that the road race (Rolex/ALMS type) drivers are generally pretty nice. I had a chance to meet Ron Fellows, Johnny O'Connell, Oliver Gavin and Olivier Beretta at an ALMS race at Road America a couple of years ago as a guest of Corvette Racing. Beretta literally gave me the hat off of his head! Just a great bunch of guys who realize that they've got the greatest job around.

Phil

[ramair311]

I just had the H&R Sport springs installed. Just about all of the body roll has been eliminated from stock under street conditions. Lowered stance looks great as well - and the ride is not overly stiff.

[SCA1]

Originally Posted by Colorob

Lowered stance looks great as well

How can we possibly know this for sure? Let me be the first to say ...




You've just dropped your new hotrod and you don't post pics? C-rob, get that camera working man!! :biggrin:

[ramair311]

Originally Posted by SCA1

How can we possibly know this for sure? Let me be the first to say ...




You've just dropped your new hotrod and you don't post pics? C-rob, get that camera working man!! :biggrin:

[JohnnyTT]

What about adding a strut brace?? What do these do to the ride? There is a BMW Performance SB available.

[SCA1]

Ahhhhh...I feel better now. Must see pics of first mods

[SCA1]

Originally Posted by JohnnyTT

What about adding a strut brace?? What do these do to the ride? There is a BMW Performance SB available.

In my experience it all depends on how stiff the car's body is. Some types of cars really benefit from a strut brace and others don't. Don't know about the 1er until someone bites the bullet and tries one out.

[TagMan]

I would really like to curtail some of the body roll in a proven way... and make sure that the solution doesn't just cause other problems.

I want to know when one of our members actually installs a MOD that truly reduces the body roll. Tell us what the solution really is! Post the proven details, and... post pics, if possible.

[mikeo]

TagMan, LarryN has installed H&R springs and states body roll is reduced. PM him for more first-hand info.

[plien69]

Doesn't the E82 already have strut braces from the strut tower to the firewall?

In any case, strut braces do nothing for body roll.

[bski]

Will a sway bar help the handling on the vert?

[r_seng]

don't want to completely kill the roll all the way, you won't be able to tell your breaking point, and then before you know it, game over into a wall or something.

[mikeo]

Originally Posted by r_seng

don't want to completely kill the roll all the way, you won't be able to tell your breaking point, and then before you know it, game over into a wall or something.

I don't agree with that and in my experience BMWs with race prepped suspensions (very stiff) are relatively easy to drive at the limit of grip compared to, say an Evo. Others have commented on that as well, including a SCCA Solo National Champ.