Roll centre adjustment - options & benefits? - Page 2 - Toyota GR86, 86, FR-S and Subaru BRZ Forum & Owners Community

autobrz · 07-25-2013, 11:41 AM

I used to have this idea of how to improve the handling of the brz without sacrificing any ride comfort. Lower the car 3 inches like Robispec has but keep the stock spring rates. Use his top mounts to retain suspension travel and his control arms to correct roll center and bump steer.

This would hugely reduce the distance between roll center and center of gravity. I wonder how big of a difference it would be compared to a stock car. it'll probably be my project when my stock shocks wear out. I'm not too sure about going over ramps though.

CSG Mike · 07-25-2013, 12:37 PM

IIRC, @robispec has been slowly increasing spring rates. While ride quality does suffer with higher spring rates like the ones we use (10/12k and 12/15k), on-track performance is increased.

The video I posted above is on 10k/12k.

ultra · 07-26-2013, 08:45 AM

Guess this hpthread had kind of run its course...roll centres not a priority for this car.

Thanks to everyone for chiming in.

Now...what about bump steer correction options?

autobrz · 07-26-2013, 11:28 AM

racerx or robispec both can make bump steer correction toe links...

CSG Mike · 07-26-2013, 12:08 PM

Quote:

Originally Posted by ultra

Guess this hpthread had kind of run its course...roll centres not a priority for this car.

Thanks to everyone for chiming in.

Now...what about bump steer correction options?

Coming from an S2k... I use bumpsteer to my advantage.

ultra · 07-26-2013, 02:52 PM

Quote:

Originally Posted by autobrz

racerx or robispec both can make bump steer correction toe links...

Tell me more

ultra · 07-27-2013, 07:10 AM

Quote:

Originally Posted by CSG Mike

While we haven't measured the curves, anecdotal evidence would show that it has (for us, at our level of development), a somewhat negligible effect. I CAN feel the difference, but do not think that it hurts the performance of the car enough that the cost is justified with how our car sits now.

You can see the movement of the wheel, and the car's roll here:

Holy spitballs! Just watched that vid. Aside from the lack of body roll it seems you've got some really sweet chassis balance + driving style synergy happening there. I love how you're able to throw it around BW like that, tail occasionally coming out now and then, and just keeps charging.

Great, fun looking setup!

Calum · 07-27-2013, 08:46 AM

Quote:

Originally Posted by CSG Mike

Coming from an S2k... I use bumpsteer to my advantage.

Could you please elaborate on this.

wparsons · 07-27-2013, 09:11 AM

How badly you need to correct this is also going to depend on how much you lowered the car... Robispec's car is 3"+ lower, I don't think most people spending much time on a track are anywhere near that much lower? I could be wrong, but I seem to remember most people staying in the 1.5-2" range.

CSG Mike · 07-29-2013, 12:26 AM

Quote:

Originally Posted by Calum

Could you please elaborate on this.

In the video, at 0:53, you can see the rear come out. Unwanted bumpsteer.

at 1:21, I miss my mark (the apex), and try to force the car to turn more, which results in the rear coming out. The intention was to get the car to rotate a tad more by using the bump in the apex.

At 1:32, I use the bumpsteer to induce extra rotation in the car, so I can carry more speed.

Just a few of the more obvious examples

Calum · 07-29-2013, 07:49 AM

But... Isn't that rear bump steer, not front that causes/allows you to do those? Or is it a changing Ackerman angle that changes the rotation point. Or am I just lost?

Thanks.

Ultramaroon · 08-15-2015, 06:59 PM

bump

steer
@stockysnail

Captain Snooze · 08-16-2015, 05:50 AM

Quote:

Originally Posted by Ultramaroon

bump

steer
@stockysnail

What's with the necro bump?

Ultramaroon · 08-16-2015, 02:10 PM

Quote:

Originally Posted by Captain Snooze

What's with the necro bump?

Stocky and I were questioning the merits of roll center/bump steer correction kits. It stuck in my head so I went back and searched.

I already suspected as much - that a few cm drop wouldn't wreak havoc on the platform.

Do you have a take on it?

07-26-2013, 08:45 AM	#17
ultra Curious cat. Join Date: May 2012 Drives: 86 GT base M/T - Red Location: Dubai Posts: 775 Thanks: 840 Thanked 383 Times in 191 Posts Mentioned: 31 Post(s)	Guess this hpthread had kind of run its course...roll centres not a priority for this car. Thanks to everyone for chiming in. Now...what about bump steer correction options? __________________ 2013 Toyota 86 GT M/T 2009 Renault Clio Sport R27 Team F1 Edition (sold) 1991 Mazda MX5 Miata (sold) 2007 Mitsubishi Evo 9 RS (sold) 2006 VW Golf R32 (sold)

08-15-2015, 06:59 PM	#26
Ultramaroon not playing cards Join Date: Sep 2014 Drives: a 13 e8h frs Location: vantucky, wa Posts: 32,392 Thanks: 53,053 Thanked 37,228 Times in 19,308 Posts Mentioned: 1118 Post(s)	bump steer @stockysnail __________________ service manuals

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07-25-2013, 11:41 AM	#15
autobrz Senior Member Join Date: May 2013 Drives: Mazda 3 Location: round rock, tx Posts: 413 Thanks: 487 Thanked 108 Times in 74 Posts Mentioned: 4 Post(s)	I used to have this idea of how to improve the handling of the brz without sacrificing any ride comfort. Lower the car 3 inches like Robispec has but keep the stock spring rates. Use his top mounts to retain suspension travel and his control arms to correct roll center and bump steer. This would hugely reduce the distance between roll center and center of gravity. I wonder how big of a difference it would be compared to a stock car. it'll probably be my project when my stock shocks wear out. I'm not too sure about going over ramps though.

07-25-2013, 12:37 PM	#16
CSG Mike Join Date: Jul 2012 Drives: S2000 CR Location: Orange County Posts: 14,564 Thanks: 8,942 Thanked 14,213 Times in 6,856 Posts Mentioned: 970 Post(s)	IIRC, @robispec has been slowly increasing spring rates. While ride quality does suffer with higher spring rates like the ones we use (10/12k and 12/15k), on-track performance is increased. The video I posted above is on 10k/12k.

07-26-2013, 11:28 AM	#18
autobrz Senior Member Join Date: May 2013 Drives: Mazda 3 Location: round rock, tx Posts: 413 Thanks: 487 Thanked 108 Times in 74 Posts Mentioned: 4 Post(s)	racerx or robispec both can make bump steer correction toe links...

07-29-2013, 07:49 AM	#25
Calum That Guy Join Date: Dec 2011 Drives: 2013 asphalt FRS MT Location: Halifax, Nova Scotia Posts: 4,865 Thanks: 5,058 Thanked 2,868 Times in 1,499 Posts Mentioned: 82 Post(s)	But... Isn't that rear bump steer, not front that causes/allows you to do those? Or is it a changing Ackerman angle that changes the rotation point. Or am I just lost? Thanks.

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