wheel spacers (wide stance) vs handling

[azerty]

Hello there,


I'd like to start a discussion about wheel spacers vs handeling on starlet chassi.
I have done quite some read on other cars. there loads which can be find on porsche and bmw but those are RWD and obviously very different in many other aspects.

there are few reason people would like to use wheel spacer :
- wider stance to have more grip during cornering (due to less lateral weight transfer)
- looks (having your wheel flush to arches)
- leave room for big brake kit
- reduced lateral load transfer

the main downsides will be:
- bearing wear
- heavy steering due to exessive positive scrub radius
- increased torque steer due to exessive positive scrub radius

On my side, I have big brake kit, so using wheel spacer would let me have much more choice in terms of wheel design. it would also help during cornering. but I'm realy worrying about increased torque steer (which is already bad enough on standard starlet suspension geometry). the heavier steering won't be a great thing during slaloms neither.

I would like to know what is the standard scrub figures on our starlet. anyone would know ?

I plan to use 20mm hubcentric spacers, and move my coilovers top axle (using camber plate) the maximum close to engine bay so I would get maximum angle (SAI) to help with scrub figures not beeing too positive (then I'll adjust camber from bottom mount to reach -2°)

 

[azerty]

for those wondering about scrub radius and SAI (steering axis inclinasion)

 

[starletsy]

I've not got much experience in this but i think your on the right lines mate as most of the Japanese tuner starlets have spacers fitted hence why cruise and jam also made wider fenders to cover them. Also one of the glanza's i had that had been some sort of track car in Japan going buy the parts that were on it had coilovers and camber bolts which never made any sense until i read what you've put about scrub radius.

 

[AdamB]

Personally I see no good reason to use spacers. I wouldn't say that using a spacer provides more "lateral force". You need to be able to get the tyre working as effectively as possible. A lot of people tend to go for a tyre such as R888, when another tyre such as a Uniroyal could provide just as much force simply through chassis setup. You have to remember that it is THE TYRE that provides the force, not any other component.

Tyre manufacturers should be able to provide you with a graph of Lateral force Vs Slip angle. The greater the slip angle, the greater the lateral force generated by the tyre.

I believe what you are refering to as the scrub radius is what is also known as the Kingpin Inclination, which isn't adjustable on the starlet chassis. Infact, not very much is adjustable on the chassis. I believe that having independent rear suspension would be where big improvements could be made to a FF vehicle in terms of adjustability.

 

[azerty]

I would be interested to know which spacers (width) those jap tuner are using.
My choice goes to 20mm cause they are the smallest hubcentric model available I know (with their own included studs and small nuts to go on your hub studs)

AdamB, you are right about the tire and lateral force, but I would like to focus on general handling more than tire spec itself on this topic. wider stance would still result with less lateral weight transfer. it would act like having lower gravity center. basicly the car should handle better when you change from a left curve to right curve (lateral weight transfer).
Scrub radius is not Kingpin Inclination. Kingpin Inclination (KPI) is same as steering axis inclination (SAI)
Scrub radius is the result of camber, steering axis inclination (SAI/KPI) and rim offset (spacers affect rim offset).
there is no SAI adjustement on our starbo, but you can use coilovers camberplate to afect this inclisation value (hence my first post explaining I would move my coilovers top axle the maximum close to engine bay). This won't affect scrub radius that much, but it would still help a bit.
On porsche comunity, to get wider stance, they modify front lower suspension arm to have it longer. that way they get a much inclined SAI and keep scrub radius close to standard. this is the proper way to do so. but Porsche are RWD, so they don't have driveshaft messing the story. if we would like to do the same, we would need to find longer driveshaft. Goodluck...

now I wonder how this guy archived to get that wide !! I really don't think he has just used spacers (he must have changed the full suspension geometry)

So now I'm confused, should I use spacers or just buy a Porsche ???

Seriously, I'm really interested to know factory starbo scrub figures.
Then, any feedback from those who have wider stance (spacers, low wheel offset figure, custom suspension geometry...)would be very welcome

 

[azerty]

Anyone with a Tack/Rally/slalom car would like to give some feedback on this mater ?

 

[azerty]

I'm bringing back this subject just in case someone would have more info on this.

Do you know if there is any detailed page on armtrong starlet ?. I really would like to know what he has done to his suspension whishbone and rear beam to get that wide

this picture shows a different suspension geometry on front. would like to get more info on this