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  #1021  
Old November 5th 2011, 04:55
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Originally Posted by aartjan View Post
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!
All good points I think AJ, some of them I didn't even think about before.
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  #1022  
Old November 8th 2011, 12:48
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Originally Posted by Wally View Post
.................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.
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.
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  #1023  
Old November 8th 2011, 18:35
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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
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  #1024  
Old November 9th 2011, 01:52
70Turbobug 70Turbobug is offline
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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.
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  #1025  
Old November 9th 2011, 04:59
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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.
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  #1026  
Old November 9th 2011, 05:49
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Quote:
Originally Posted by evilC View Post
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.
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

Last edited by Wally; November 9th 2011 at 05:54.
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  #1027  
Old November 10th 2011, 17:37
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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 (!!).
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  #1028  
Old November 11th 2011, 13:20
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Some pics of the new wheels, still with snow tires, 50 series even in front
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



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  #1029  
Old November 11th 2011, 13:46
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Great pics Wally ! The bumper cover mod looks very subtle .. I didin't even notice it the first time I looked

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

Sandeep
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  #1030  
Old November 11th 2011, 13:57
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Quote:
Originally Posted by Sandeep View Post
You car looks much more "tame" with the new wheels ,

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 .
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  #1031  
Old November 11th 2011, 17:38
dave forder dave forder is offline
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Quote:
Originally Posted by Wally View Post
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).
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  #1032  
Old November 11th 2011, 17:56
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Thanks Dave, we're definitely on the same page!
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  #1033  
Old November 12th 2011, 10:15
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I like the new wheels and the aero cover on the bumper.
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  #1034  
Old November 14th 2011, 13:54
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que hermoso, cada vez esta mas hermoso este vw!!! felicidades!!
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  #1035  
Old November 14th 2011, 19:20
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Paint the wheels gold to keep the bug's personality unchanged!
Dare I ask, what are your plans about the bbs wheels?
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