Hi Wally

Do you have any issues with the tie rod touching the chassis rail / inner mudguard?

Steve

No, but... I have squared the spare wheel well (for easier battery placement and such) and the tie rod could hit the edge or so it seemed, so I made a recess for it.
The tie rod never hit anything fortunately and now with the stiffer springs even less chance.

Wally: I'm in the process of correcting poor scrub geometry. The high offset porsche wheels make the scrub radius massively negative. I was desperate to try and avoid wider wings but the compromises just weren't worth it. From memory my scrub offset measured about 38mm -ve. A quick test with the rear 944 wheel spacers have made the steering feel much nicer and more confidence inspiring, it isn't to far off stock now I believe. Most RWD cars have +ve scrub but some late (including 2 bolt strut supers) are designed with -ve.
Rich

I hear you Rich; I run the 21mm spacers up front as well, but more because I couldn't fit the high ET wheels; this was before I ran the slimmer AVO struts. Now the spacers help to have full steering without hitting the inner fenders...

My theory is that the 944 spindles are bad for scrub radius. I think their tie rod ends are located further outwards then the originel VW 2-bolt spindles, which curve more towards the inner side of the car? Not sure though. Whats your take on my theory?

Sounds like you should just measure yours, I did it by jacking the car as you have done above at ride height and holding an edge as close as possible through the points after having marked off the width of the tyre (before I took the wheel off) to get the centre line. Tie rods shouldn't affect scrub radius, just the affect of the scrub, their effect is more too do with ackermann & steering effort/speed.

I actually did already indeed Rich, just like you described, but think I got the wrong points connected...:confused:
With your answer I am a little confused even more what KPI and scrub radius is. MotoIQ had a great article about it the other day, using tie rod(?) and the lower ball joint of our Mc Pherson suspension system. Or is that just the upper and lower suspension point in the picture? Thought the upper one was the tie rod of the steering in the schematic?
http://photos.motoiq.com/MotoIQ/Tech..._LBoxc-L-1.jpg

However, I took the line through the upper Mc Pherson strut connection with the body and the lower ball joint. Thought afterwards I did it wrong and it needed be through the tie rod and lower ball joint. Maybe I did it correct after all?
Anyways, that gave me a scrub distance of +18mm. Still not sure now if that was correctly measured or not...
Mike specified a distance between 3/4" and 3". With 18mm I am right at the lower bandwidth of that.. a bit more might help. I have a little room in the wheel arch, but I think 17" might be better for track driving anyways, mostly because of wheelweight you feel the negative effect of it most on the front. 7x17" is half an inch less wide and with a few mm more spacer, might just give that added scrub we're after?

Tire centerline above is right against the rim contact path, which is somewhat confusing too. It doesn't seem to be the exact tire centerline..?

I'll post some of the pics I took of that tonight.

http://i174.photobucket.com/albums/w...2.jpg~original
http://i174.photobucket.com/albums/w...0.jpg~original

http://i174.photobucket.com/albums/w...3.jpg~original

I think I found a way to alter KPI on my car: I can change camber with the extra large excenter bolt on the inner side of the control arm, but also still with the lower strut bolt. If I arrange the strut such that it sits most vertical (less camber with the lower strut bolt), and counter this with making the TCA longer with the inner excenter bolt, I will have effectively reduced KPA and increased the scrub whilst keeping the same camber.
That should yield a little better steering self-centering and straightline stability :)

Wally: you did it correctly for a strut front end, however that image you just posted is how to measure on a double wishbnoe front end (ie the tie rod/steering arm is not shown).
one thing to note also, just in case: you need to draw the line through the centres of the actual ball joints, not the centre at the base as this can throw the measurement out quite a bit (probably just how you have the bar leaning in the picture).

From what I've read -ve scrub gives more of a stabilising effect with a bit less feedback. The problem with going too close to zero is that it can flip between +ve and -ve depending on caster and the dynamic effects of the suspension giving very unstable feeling...

Thanks Rich; yeah, the double wishbone suspension must have confused me :)
The rod was held through the imaginary center of the lower ball-joint, but my wide angle lens doesn't picture everything -in line- so to say.

The lower pic was taken with the front high, afterwards for the actual measurement, I have taken the nose to the cars normal height of course.

So, its either much more positive or very negative scrub for better steering stability??
I though that 'some' positive scrub was the goal?

The 'norm' for RWD is +ve scrub, I'd guess 10-30mm or so? Too much gives to much kick back through the steering. I equate it to +ve giving an 'oversteer-like' kick back through and -ve as an understeer kick through the car during disturbances (ie safe). Like many of these things, it's finding a set-up that works for you as there are so many variables!

Wally, you are right that the tie rod ends are further out and this is because the steering arm is straighter i.e. more parallel than the 1303 (2 bolt one) I took off. This obviously affects the ackermann but I don't see the corrolation with the scrub radius? The bottom pivot of the 944 strut/stub axle also appears further outboard as my fabricated TCAs, although they match the 1303 pressed steel ones, had to use all the camber adjustment at the base of the strut and the inner bush to get a maximum -1.5* camber. If that is the case then it should move the point at which the kingpin angle i.e. the line through the top mount and the bottom ball joint strikes the ground plane than the VW stub axle.
I found that with 30mm spacers on the front, to fill the arches, the steering became very heavy (+ve scrub radius) and I now run without spacers for easier steering. I also now have inner wheel arch scrubbing with the 6" teledials with 195/65 tyres so I am going to try fitting those tyres to the 7" teledials that will increase the scrub radius but it might provide the compromise between the rubbing and heavy steering as well as stiffening the tyre sidewall.

Clive

Nah, that was my faulty take on what KPI angle was..:o Your right that it doesn't matter for scrub, but will for ackermann principle (if I understand that correctly). Maybe the straighter steering arms on the 944 spindles are a more modern take on suspension geometry?

Anyways, do you think the stance of my front wheel is ok in the turn, or can it have some more negative camber in the corner under stress?
It just may be so that the tca presses the (topline) semi-urethane joint enough inbound that it reduces camber too much? If so, Lee's rose joint solution for the tca may help out?
In the picture, my front camber was -2 degrees in rest!

http://i174.photobucket.com/albums/w...0.jpg~original

The best way to check if you are running the right amount of camber is to measure the tyre temps across the width after a typical hard drive, if it's constant then you have it all spot on and maximising the grip available.

Good idea, I'll start looking for one of those IR thermometers.

absolutely.... (as I suggested previously :D )

The quickest way to find out how your tyres are interacting with the road. Measure inner/middle/outer tread temps for each tyre after a hard few laps. Having a mate handy to write down the numbers as you call them out helps.

I got this one: Deal Extreme thermometer
(it's smaller then it looks, it's about 10 cm long)


It's range is from -50 to 260 degrees celsius, and works very good.
And...it's very cheap.

You have to be patient though, delivery takes 1 to 2 weeks.

i have http://www.sealey.co.uk/PLPageBuilde...iredresults=16 for doing tyre temps and its also proved to be a great diagnostic tool. checking header temps quickly tells you which cylinder is not running right.

Hi Wally, In answer to your question, the front does look as though it's running about +1* in the turn in roll but the tyre doesn't look too stressed to suggest that anything is moving around too much. I agree with the lads in that you need to take tyre temps to understand what the suspension is doing.

I would be a little concerned to dial too much -ve camber in to increase the verticality of the wheel in long fast turns as that may give the front too much grip. Understeer would be preferable in the long fast turns and my preference is neutral to slight oversteer in the tighter ones.

As regards the 944 steering arms I suspect that the angle, which is more parallel (lets say tending to 0*) is there to correct the position of the steering rack and the angle of the tie rods. Without the accurate geometry of the 944 I can only speculate. Similarly, I haven't modelled the front end of the bug with the steering box arrangement to check the ackermann, all I can say is that the steering gets heavy beyond a 1/2 turn on the steering wheel and I find that its appears to dig in on the outer wheel with no scrubbing. That may be as a result of the lower roll centre although I will experiment with the original roll centre soon.

Clive

Thanks for that Clive! I agree and won't dial in more neg. camber. Lee's new arms and the heim joints in them may however limit the amount of movement inbound the arm makes when hard cornering and so preventing further positive camber change.

I am also considering changing back to a 17"wheel as I feel the 18" are just a little too heavy for competition. I may regret it but I just need to see what it feels like again.

If I remember correctly you still wanted to increase caster for more straight line stability. Maybe this is an opportunity to also profit from the inherit increase in dynamic camber related to steering angle? So just that little more bite in the short corners, while maintaining the same amount of (safe) understeer in the long high-speed sweeps?

Besides advantages in mass, smaller wheels might also give the advantage to use them in combination with a tire (shape) that is less sensitive to positive camber angles; if that is a point to consider?

I like how you say this! :D
All good points I think AJ, some of them I didn't even think about before.

Wally, You may be right about the wheel change. principally the larger the rim diameter the heavier the wheel/tyre combination is for the same o/a diameter. This would be of significance with the unsprung weight that will affect the damper performance and bearing in mind the sprung/unsprung weight ratio on the front of a strut bug. You could also look at a compression strut installation that Rob and i have talked about in the past as that will immediately turn the anti-roll bar into sprung mass rather than unsprung with a significant effect on the ratio.

It may be fashionable to fit large diameter rims with low profile tyres but the same overall diameter with a taller tyre is lighter (tyre wall rubber is lighter than aluminium wheel.

If you set the suspension travel to standard then a 17" tyre wheel combo will lower the front by 5-35mm depending on individual tyres that has to be beneficial whilst still maintaining the geometry.

I was going to suggest a crossply racing/road legal tyre but I could find any 17" ones just 15". You could revert to 15" and use crossplys to give that extra wall stiffness and keep the tread flatter but only if your brakes will accommodate the 15" wheel. you certainly have enough power to make them work.

Speaking strictly from a weight/diameter perspective, I was surprised that, with all other things being equal or better, once I went from a 17" OEM Cup II to the heavier 18" Cup II repro my 1/4 mile time slowed appreciably and consistantly. I just didn't expect it to make THAT big a difference, but it was almost half a second.

Jason

I would try one thing after the other.Making various changes at once you won't really know what effect each individual mod has done imho.I personally disagree a little with some points mentioned.An 18" wheel is generally heavier but provides more stability also, especially ona highspeed straight and high speed corners.How many cup cars do you see with a 17" wheel nowadays? Most are running 19" or bigger.Obviously wheelbase and width are much larger than a bug which justifies the larger wheels also.Imho a larger wheel provides more overall stability in handling and would trade a couple of kilos for it any day.Remmele's bug runs under a 1:12 minute around the Hockenheim small course (997 Porsche GT3 RS runs 1:11)with 19",2 seconds faster than at the Recaro Tuning Days a few years ago with 18",and he has "only" 300bhp.Also what competition are we talking about? Against other track day cars? Wally's power to weight ratio puts him pretty far up in the field and just judging by the videos he's not really pushing it to the limit. I don't mean that negatively on your driving Wally ;)
For autocross a smaller diameter wheel is the way to go for the sharp and short corners but it's much different on an open track.

not done much testing with the 17 inch wheels but the few runs i have done i can say this, the turn in is much sharper and the brakeing seems to be better. i went from a 580mm tyre to a 620mm tyre. i was expecting to have problems with turn in as i have fitted a zf lsd as well but it was very good once i changed my driving style to suit.
tyre wise i was running 240/580/15 on 9 inch wide rims on the rear and 200/580/15 on 8 inch rims at the front with softish rally slicks. i'm now running 7.5x17 with 200/620/17 track wets which again are very soft. i have more grip and it feels very stable upto 80mph which is about as fast as i can go at prescott hill climb.
one thing i did notice was a feeling from the front that the tca to anti roll bar joint was moving, i could feel a knock when hard braking and then movment till it loaded up, this was more when braking into the corner. think i'm going to try the compresion stut to tune this out.

Very much agree with your whole post Clive! You just said it so much better :)
I will change the 7,5x18 with 225/40 fronts for 7,0x17 with 205/40. That alone gives a 20mm drop in ride height wih equal suspension geometry.

Mark, I do agree I shouldn't change multiple things at the same time so the proper effect of each can be judged better, however...there are only so many hours in the day and so much time I can spend on wrenching and driving in a season (unfortunately).
I don't agree with your saying that 18 or 19" is better for circuit driving with one car as an example. Remmele may have changed more things at the same time also...or just learnt the track better. You may be referencing to the gyroscopic effect a larger and heavier wheel has? That is indeed beneficial for straight line stability ONLY, but works counter w hen you want to change direction, i.e. turning in for a corner. With competition use I was referencing to me taking part in the TimeAttack series in the Netherlands. I even won my class last year (on points, but still) if you didn't caught up with that yet :-) http://www.timeattack.nl/nl/news/ite...iciteerd_.html .
You are absolutely right that I don't push it extremely hard in corners at the track and that is part of my poor driving abailities to push it on the edge of slip but part of me doesn't want to explore that fine line too closely. That doesn;t help my track times on circuits, but I am having fun nonetheless, I assure you!
Jasons' experience is what I was expecting and speaks volumes for what a heavier wheel does imo. Thank you for sharing that Jason!

In my opinion, wheel size just needs to be as small as to just fit your brakes and width adjustable to power you run. My front 350mm disks limit that to 17"which suits me fine tbh.

The wheel I chose are about 1,7 kg lighter for the fronts and 1,2 kg lighter for the rears. I expect about 1 kg per tire savings as well, so this should give a pretty big gain i reducing unsprung weight. The bummer is, I bought them with winter tires and have to get new summer/semi's now for them as well, so that will probably have to wait a while for budget to recover.

I'll try to make a pic coming weekend with the new wheels on the car ;)

Picked up a set of 9Jx17 / 7Jx17 with 205/50/17 M+S on the front.
These front wheels weighted 3,7 kg less per wheel then my current front wheels (!!).

Some pics of the new wheels, still with snow tires, 50 series even in front :lmao:
Yes, its definitely function over form: the gold wheels looked much more spectacular, but I think these will drive better and that what counts for me.

Went for a drive with my girl today to do some groceries, which was quality time times two :)

http://i174.photobucket.com/albums/w...1.jpg~original

http://i174.photobucket.com/albums/w...3.jpg~original

Great pics Wally ! The bumper cover mod looks very subtle .. I didin't even notice it the first time I looked :o

You car looks much more "tame" with the new wheels :p, looking forward to the race reports.

Sandeep

Yeah and thats not necessarily a bad thing when you also drive on the road imo.
But no worries, I think a 40-series front tire lateron and maybe a little turning down of the strut will give it even more aero benefit and probably also a little less 'tame' look ;).

Good choice of wheels. Your car will be more agile with these wheels and I agree it makes the car look tame, a tweek with the suspension and tyres will get back that agressive look (those goldies did look good though but it is not all about looks when you are out on the track).

Thanks Dave, we're definitely on the same page!

I like the new wheels and the aero cover on the bumper.

que hermoso, cada vez esta mas hermoso este vw!!! felicidades!!

Paint the wheels gold to keep the bug's personality unchanged! :D
Dare I ask, what are your plans about the bbs wheels?

Nah, that wouldn't suit this type of wheel. Besides, did you know I did not paint the BBS wheels hearts? The former owner (they were on a custom GolfV) I bought the wheels from painted them gold, I just bought them like that. Mostly because I was looking for that particulair size (9Jx18 is rather rare, most rears are 10Jx18).
They will be sold to raise funds to pay for the semi-slick tires I need for the 17". The current owner of my former 412S has an interest, so we'll see if that works out ;)

oh, if I remember correctly, I saw a picture of the 412 with those wheels on, and it looked veeery nice.
If that doesn't work out in the end, I'd very much like a price quote on those :D

No worries mate, you'll be first then, but he would be very foolish not to accept as I asked him a very reasonable price (which would be same for you then of course ;)).

Found some pics someone posted from the last race.
Did some racin'
http://i105.photobucket.com/albums/m...r.jpg~original
Kissed some girls
http://i105.photobucket.com/albums/m...r.jpg~original
http://i105.photobucket.com/albums/m...r.jpg~original
and sprayed some cheap bubbles :lmao:
http://i105.photobucket.com/albums/m...r.jpg~original

Are you sure only kissing:cool::cool::cool::cool:????????