Experience with RalliTEK swaybars & springs + Whiteline Roll Center Kit on Spec.B

[T-Rexky]

Good day,

 

So I finally got bit by the upgrade bug...

 

It started with wanting better swaybar setup but it is now progressing towards also adding stiffer springs with the Whiteline roll centre kit. I am looking at RalliTEK bars & springs, but am debating about the roll centre kit. I ultimately want better handling without compromising the comfort too much, since the car is the primary commuter.

 

Before I dive right in, I wanted to solicit some opinions from anyone who might have the above setup on their Spec.Bs. How is the handling and balance? Is the car still going to understeer with the stiffer swaybars and the Whiteline kit, or will the roll centre kit push it over neutral and into oversteer? Ideally I would like to keep some slight understeer.

 

RalliTEK were extremely helpful on the phone, but they do not have prior experience with this specific configuration. I would very much appreciate anyone's input.

 

Thank you.

[whitetiger]

you will not feel any difference with the whiteline kit. with just lowering springs and sways. if you are concerned about under-steer, then you need better tires.

[T-Rexky]

you will not feel any difference with the whiteline kit. with just lowering springs and sways. if you are concerned about under-steer, then you need better tires.

 

Thanks for a quick response whitetiger. Are you suggesting that I should skip the Whiteline roll center kit all together? I thought its purpose was to reestablish original suspension geometry with a lowered suspension in order to reduce roll and understeer?

 

I would actually like to maintain small understeer after I am done with the mods, since I will not be the only one driving the car and I want it to remain more "predictable", particularly in our heavy winters.

[whitetiger]

no, it does not reduce roll, it reduces bump steer. the main cause of understeer is lack of grip at the front of the car. the whiteline roll-center kit barely helps this directly. the real way to get more front grip is get better tires and control weight transfer with better springs/struts and a good alignment.

[F-WDC Spec B]

to reduce understeer a larger rear swaybar works. but IMO the best bang for the buck are the sways, springs and new tires. The oem RE-11 dont have as stiff of a sidewall that is desired but they are really good for normal street driving.

[whitetiger]

a RSB wont increase front grip, but just make the rear lose more grip causing the rear to come around before the front looses grip. this will be over steer, but it means teh car will be slower since overall grip was not increased.

[mustangendsley]

/\ depends on the size of the f/r swaybars. I have the 25 mm f/r swaybars w rear on firm and front on soft and the ride on the track is awsome and feels planted w no roll. It didn't make me slower, it made me faster on the track.

[whitetiger]

^you probably have a good tire to compensate for the increased load shock caused by the thick sways. you do realize though that if you had thinner bars but stiffer springs and struts you would have even more grip on the limit.

 

i run 25mm bars as well, but that because i autox with r-comps. if i was on a street tires, i would not have gone so thick.

[FredBeans]

no, it does not reduce roll, it reduces bump steer. the main cause of understeer is lack of grip at the front of the car. the whiteline roll-center kit barely helps this directly. the real way to get more front grip is get better tires and control weight transfer with better springs/struts and a good alignment.

 

It might reduce roll a little. The most noticeable effect of the kit is the reduction in bump steer, and I found that to be a considerable improvement when I was lowered on Swifts (-2.1" up front). However it also raises the roll center back towards it's original height.

 

The roll angle of the chassis is determined by (in addition to the springs and sways) the lateral load of the vehicle and the distance between the CoG height and the roll center axis, which could be called the "torque arm". A lower roll center means a longer arm, which means all other things being equal, more roll angle.

 

Please realize I'm not trying to argue this point with you Josh, just that there is some slight difference which is probably only academic for 99% of people.

 

Finally, a stiffer rear swaybar does transfer some of the weight transfer from the front to the rear which may ever-so-slightly improve front end traction, but for the most part it is just for tweaking the handling balance of the car. Before you do any suspension work make sure you are running the best tires possible for your conditions... you can't get more g's without upgrading the rubber.

[whitetiger]

^ i know. i played the affects of it down because the RCK only makes small changes that can only be felt on the edge of grip and for most people it isn't necessary until they have other more important areas of suspension. the static angle of the LCA and tire rod only matters when measuring alignment at states full weight transfer. the name "roll center kit" is misleading since it does not really reduce body roll. but rather re-center the susp arms so they dont roll or swing beyond where they should.

[T-Rexky]

Thank you all for your responses. I gathered so far that the roll center kit will have negligible impact on car balance, which was my primary concern. It also sounds like the kit is well worth it for the reduced bump steer with a slightly dropped suspension. If and when I get the whole kit installed I will post some comments and impressions.

 

Thanks again.

[subawang]

I thought another key benefit was that in the taller ball joints, the roll center would be back or closer to it's stock location (hence the name roll center kit). This would aid in dynamic camber, which would increase front grip, thereby reducing understeer.

 

I've thought about adding this kit to my car (lowered ~1" on RCE T1's), but I'm not sure how much camber I have lost by changing the roll center and if it is worth the points assessed for the AX club I run with.