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tramlining in 300+ hp fwd b15s

PostPosted:Tue Nov 01, 2016 9:23 am
by yogib777
under discussion, no real solutions yet
but some findings that relate to tire wear and steering effort

Tramling can be defined as the car shaking its head.
rapid movements back and forth that can be violent

after much experiment and discussion
we find

as wheel width increases, track increases and traction increases
we get to a point of instability

some useful indicators are center of tire rotation and the resulting scrub radius changes

if the tire doesn't rotate on center
one part of the tire must move more than the other side
it scrubs
this affects tire wear as well as tamlining

looking at the following tire, we see its center of rotation is far from center
resulting in the inner edge of the tire scrubbed clean
even though wear every place else is even

Image20161017_153914 by yogib777, on Flickr


center of rotation was determined simply by turning the wheels in place
several times, rolling back a bit and observing the results


as the center of rotation moves toward the outside of the wheel [my case] steering effort increases exponentially
Small changes make big differences

closest solution is brocks short track car
9" wheels, 35mm et, 235/40/17 r-comps
center of rotation moved in about 1/4" from mine
ImageDSCN1606 by yogib777, on Flickr
ImageDSCN1604 by yogib777, on Flickr

compared to mine
Image1309488 by yogib777, on Flickr
ImageDSCN1090 by yogib777, on Flickr

back to 2jr, tomorrow
we try smaller tires on the same wheels
but track tires not street tires

will report back on new alignment specs and track dyno tune
[faster turbo spool, more low end, less top end hp]

real test will be Sat. Nov 5th
can it run wot at AMP



tuned at 361hp, 371 tq, it turned 91mph in the 1/8 mile
shaking so hard, i would not have been able to hold it in lane had it been a 1/4 mile

Re: tramlining in 300+ hp fwd b15s

PostPosted:Wed Nov 02, 2016 8:10 am
by yogib777
next we can illustrate inconsistencies
and general rules

what makes little sense yet:

complaint
car shakes on wot

ans, [camero forum]
front wheels and tires too large

yet in my case
275/40/17 r-comps went straighter
had less shake

than the 255/40/17 extreme street tires
on the same rims

17x9, 20mm et
ImageDSCN0327 by yogib777, on Flickr


but the general rule is backed up by this experiment

we tried an extreme case
a car with stock wheels, 47mm et, and extreme street tires
went straight but spinning with 225s
ImageDSCN1854 by yogib777, on Flickr

substituting 15x8s fitted with 225s of similar ilk
but
with near 0 offset
10mm spacers required to clear the z32 calipers
car goes crazy
ImageDSCN1840 by yogib777, on Flickr


hypothesis
[17"] wheels with less than 20 mm et, MAY cause excessive tramlining and increased steering effort

Re: tramlining in 300+ hp fwd b15s

PostPosted:Wed Nov 02, 2016 8:15 am
by yogib777
disclaimer
does not apply to bias ply drag racing slicks
same 15x8s equipped with 24.5x8x15 M/T slicks

runs the straightest of all tires tested [all wheels too]

Re: tramlining in 300+ hp fwd b15s

PostPosted:Thu Nov 17, 2016 8:01 am
by yogib777
next we totaly solved the problem

just run slicks
lol

i had never run slicks on all four wheels before

what a trip
total grip

to the ground goes all the zip
it's a pip

to be able to zip and rip
with just a throttle blip

but takes tires huge, and super light
ImageDSCN2035 by yogib777, on Flickr

and just the right height
ImageDSCN2011 by yogib777, on Flickr

compared to 225s that bite
ImageDSCN1949 by yogib777, on Flickr

but on the car, they look just right
ImageDSCN2040 by yogib777, on Flickr

the ride is outta sight
turns easier and with less might

nail it
wail it

it sits tight
finally got it right

Re: tramlining in 300+ hp fwd b15s

PostPosted:Thu Nov 17, 2016 8:21 am
by yogib777
tramlining what tramlining


you can see from what i wrote, this really works

tq steer is still there, but most of the head shake, wot, is gone
and for the 1st time i can use all the power coming out of corners

turn in, is instant
car feels more neutral mid corner
and corner exits have gone from nitemare to carnival ride

acceleration from 40-100 surprised me
get it to hook and this begins to feel like an 11sec 1/4 mile car


something are readily explainable
it makes sense for the turn in to quicken
we about cut the side wall in half and made it stiffer

decreasing tire diameter, is like increasing gearing
add increased grip
and faster acceleration seems expected

what i could not explain:
why the ride got better
why the steering got easier
why wot was straighter and easier to control

now, how do i duplicate this with tires i can actually drive on the street

as it sits now
i am totally happy with it

if i could use these legally
i'd be starting on the cosmetics for the 1st time

Re: tramlining in 300+ hp fwd b15s

PostPosted:Fri Nov 18, 2016 2:29 am
by CrickiKaze
Tire construction really, stiff sidewalls are more than likely the biggest assistance and the taller tire probably helps with how much flex is being transferred to the steering...only a guess really.

Re: tramlining in 300+ hp fwd b15s

PostPosted:Fri Nov 18, 2016 2:31 am
by CrickiKaze
If those are wet slicks, that will explain a good bit as well to your experince since they heat up faster.

Re: tramlining in 300+ hp fwd b15s

PostPosted:Fri Nov 18, 2016 8:55 am
by yogib777
joe used them on a miata at rd Atlanta

could not find them listed on tire racks continental competition tires list

don't know what they really are
hard to find Continental slicks

Re: tramlining in 300+ hp fwd b15s

PostPosted:Fri Nov 18, 2016 8:20 pm
by CrickiKaze
So what was the whole set up on the rims and tires, I see 19 on the tires in chalk.

Re: tramlining in 300+ hp fwd b15s

PostPosted:Sat Nov 19, 2016 10:14 am
by yogib777
they weigh 19lb ea

each tire is worn in on a specific rim
thus marked rt front etc

so no rotating the tires
each is perfectly worn in for its position on the car

this seems to work very well
not yet willing to risk changing it

Re: tramlining in 300+ hp fwd b15s

PostPosted:Sat Nov 19, 2016 10:17 am
by yogib777
wheels are 17x9, 20mm et
tires are listed as 225/45/17s

but that in no way relates to its real size or diameter
more like 245/40s or 35s