BTCC Honda Civic Typr R nary lifts a rear wheel - why?
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Re: BTCC Honda Civic Typr R nary lifts a rear wheel - why?
There have been discussions about roll centers, roll axis and roll center migration. Some don't think any of these matter much. I am in the camp that beleives roll moments are determined by RC location and migration and i have a lot of company. Thus, they control roll/weight distribution even before springs, dampers, swaybars, and track width considerations are made...based purely upon the relationship between RC location(s) and the CofG.
Camber adjustments affect RC location and migration as well...camber curves inlfuence RC migration and therefroe weight distribution...even if a little.
In a turn, RC moves to the inside, CofG or centroid mass axis moves toward the outside and we get weight transfer. How far, AND, how abruptly that weight moves is determined by RC location(s). The height of RC determines how abruptly and how much weight transfers...
Bigger springs may resist visual weight transfer, but the weight is moving in a pre-determined path regardless - pre determined by the relationship between RC and CofG.
...have the rules allowed much wider track widths? Track width affects RC location, migration and roll moments as well...
A fair number of folks in the racing community do not regard Roll Centers as important. I can only suggest that competition has caused folks to look into ever more descrete areas of tuning. In general, raise rear RC and we get a quickly loaded rear outside tire - good for transient - with reduced ultimate weight transfer in steady state when compared with a lower RC location. This in particular aids turn-in and in theory allow the use of softer rear springs and SB. I am rambling at this point, but Roll Centers are fundamental to handling fidelity...I would say that track width changes and RC location(s) are the most fundamental aspect of tuning with these tpyes of cars.
Camber adjustments affect RC location and migration as well...camber curves inlfuence RC migration and therefroe weight distribution...even if a little.
In a turn, RC moves to the inside, CofG or centroid mass axis moves toward the outside and we get weight transfer. How far, AND, how abruptly that weight moves is determined by RC location(s). The height of RC determines how abruptly and how much weight transfers...
Bigger springs may resist visual weight transfer, but the weight is moving in a pre-determined path regardless - pre determined by the relationship between RC and CofG.
...have the rules allowed much wider track widths? Track width affects RC location, migration and roll moments as well...
A fair number of folks in the racing community do not regard Roll Centers as important. I can only suggest that competition has caused folks to look into ever more descrete areas of tuning. In general, raise rear RC and we get a quickly loaded rear outside tire - good for transient - with reduced ultimate weight transfer in steady state when compared with a lower RC location. This in particular aids turn-in and in theory allow the use of softer rear springs and SB. I am rambling at this point, but Roll Centers are fundamental to handling fidelity...I would say that track width changes and RC location(s) are the most fundamental aspect of tuning with these tpyes of cars.
Last edited by meb58; 09-28-2010 at 08:09 AM.
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Re: BTCC Honda Civic Typr R nary lifts a rear wheel - why?
For a simple gross insight into the proportionality of inside rear lift on front wheel drive try thinking in cases. What's the most lift you ever did see? Was it an old showroom stock VW Rabbit? And what's the story on those that exhibit minimal or nonimal lift - like those cars Claude is always looking at? What's the difference? Is it overall stiffness? The soft cars roll and lift more? The stiff cars roll and lift less? Hmmmmmmm.
Scott, who..."NO! It Must be more complicated. Much More Complicated"...and while sure, it is...yeah but, it's not...that...let's revisit this in 7 years...
Scott, who..."NO! It Must be more complicated. Much More Complicated"...and while sure, it is...yeah but, it's not...that...let's revisit this in 7 years...
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Re: BTCC Honda Civic Typr R nary lifts a rear wheel - why?
Conversely, there is a very popular photo of a e46 M3 race car lifting its inside front wheel off the ground by an inch or two. A compromise perhaps, in a fairly tight turn where rear wheel traction is more important to lap times than front end grip...and I am sure that with the right traction control configuration that the rear wheels help point the way.
...in 7 years we'll all be gone...Dec 21, 2112...will rear wheel lift matter?
...in 7 years we'll all be gone...Dec 21, 2112...will rear wheel lift matter?
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Re: BTCC Honda Civic Typr R nary lifts a rear wheel - why?
I've seen photos of cars lifting BOTH inside tires. Maybe we should just run zero droop suspension front and rear, ditch sway bars altogether and let traction control, stability control, and ABS sort it out....
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Re: (Civic44)
My Civic lifts the inside rear far less than my Integra did. The Integra was tossing much more, and higher, weight around. This (roll center) is why the taller VW GTIs lift the rears wayyyy off the ground. Those cars are cornering best when they look like they're about to flip over.
Conversely, there is a very popular photo of a e46 M3 race car lifting its inside front wheel off the ground by an inch or two. A compromise perhaps, in a fairly tight turn where rear wheel traction is more important to lap times than front end grip...and I am sure that with the right traction control configuration that the rear wheels help point the way.
Great read so far, its nice to be able to read information like this since like said before, there isnt much of it out there.
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Re: BTCC Honda Civic Typr R nary lifts a rear wheel - why?
Looking back over this thread, I realized that something has been completely over looked.
Front droop travel.
The distance the front wheel can travel under unloading conditions is directly related to body roll, and inside wheel lift.
The car will continue pick up the inside body until there is no more weight on the inside front axle. Other than momentum (abrupt turn in, curbing, etc) a steady state load will never bring the inside front wheel off the ground on a FWD car.
Increase suspension travel, increase roll.
In a quest for a more well rounded dual purpose car, I experimented with a dual spring front strut setup this season. Adjustable body length struts allowed me to dial in exact strut length and droop specs.
With the same 750# main spring from last season, coupled with a new 350# assist spring I set it to have 1" total droop. Compared to the .25" of main spring droop from the previous season.
With no other changes to suspension, tire size, or compound, roll was increased significantly, with another inch available for the body to creep up on the inside strut. This excess motion in the front will inevitably cause more motion in the rear, and in turn cause more wheel lift.
Notice the loading on inside front contact patch, as well as load on outside front wheel are almost identical, but rear wheel lift is increased in 2014.
2014:
.
.
2013:
.
.
The old BTCC cars also used limiter straps as a quick was of droop tuning and I'm sure it was part of the body control the OP spoke of.
Front droop travel.
The distance the front wheel can travel under unloading conditions is directly related to body roll, and inside wheel lift.
The car will continue pick up the inside body until there is no more weight on the inside front axle. Other than momentum (abrupt turn in, curbing, etc) a steady state load will never bring the inside front wheel off the ground on a FWD car.
Increase suspension travel, increase roll.
In a quest for a more well rounded dual purpose car, I experimented with a dual spring front strut setup this season. Adjustable body length struts allowed me to dial in exact strut length and droop specs.
With the same 750# main spring from last season, coupled with a new 350# assist spring I set it to have 1" total droop. Compared to the .25" of main spring droop from the previous season.
With no other changes to suspension, tire size, or compound, roll was increased significantly, with another inch available for the body to creep up on the inside strut. This excess motion in the front will inevitably cause more motion in the rear, and in turn cause more wheel lift.
Notice the loading on inside front contact patch, as well as load on outside front wheel are almost identical, but rear wheel lift is increased in 2014.
2014:
.
.
2013:
.
.
The old BTCC cars also used limiter straps as a quick was of droop tuning and I'm sure it was part of the body control the OP spoke of.
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