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-   -   Realistic top speed and tire choice for circuit driving (https://www.germanlook.net/forums/showthread.php?t=11583)

Sandeep January 16th 2013 10:51

Realistic top speed and tire choice for circuit driving
 
Hi All,

I'm looking for some suggestions on a realistic top speed for circuit driving along with some tire suggestions as I need to replace my ~ 10 yr old Pirelli P Zeros.

Car information:

1974 standard beetle body with no aero mods, 2" wider rear fenders, 1.5" wider front fenders

Coilover rear suspension, QA1 double adjustable dampers with 400 lb/in springs, 5 bar kafer brace, stock steel rear arms, no torsion bars. 24mm whiteline adjustable sway bar, new bushings throughout.

Lowered adjustable front suspension, hybrid spindles (VDub Engineering), new bushings, additional camber adjusters, 22mm whiteline adjustable sway bar.

18 x 10 rear wheels, 18 x 8.5 front wheels, 993T front calipers with 322x32mm rotors, 944T front calipers on rear with 309x28mm rotors

2413cc T4 Turbo (80mmx98mm) GT3076R turbo, max rpm ~6300, max boost ~ 20 psi. Hoping for ~ 350 FWHP

Porsche G50/01 gearbox, stock, Tilton double clutch setup with custom flywheel.

My local track would be Mosport Raceway ... now renamed http://www.canadiantiremotorsportpark.com/ and the Porsche 930's (stock) are hitting 140 mph / 225 kph on the back straight before needing to brake.

From old you tube videos (in a controlled environment :p) the beetle with turbo 2.0 / 901 gearbox hits 200 kph from a standing start in ~ 13 seconds and did the quarter mile in ~ 12 secs at ~ 118 mph.

Questions:

1. Is it realistic to drive up to a top speed of ~ 150 mph / 240 kph in a beetle with a kamie front spoiler and remmele style rear spoiler ? Not a constant top speed for a long duration ? I think it may be as I've been up to 200 kph with the car feeling stable with no jittery tendancies. Can I add 40 kph more ?

2. Old data was with a turbo 2.0 T4 and Porsche 901 gearbox. New gearbox is a g50/01 with 3.44 R/P and 0.89 5th gear. Old tire size was 235/35/18 front and 265/35/18 rear. Not a big selection in 235/35/18 now but looking at Michelin Pilot Super Sport in 245/35/18 (similar dia as old tire @ ~ 24.6) and 285/30/18 Pilot super sport rear (up from 265/35/18, but slightly smaller diameter)

This would give ~ 60 mph in second gear @ ~ 5800 rpm, 100 mph in 4th @ 5300 rpm, and ~ 150 mph @ 6200 rpm which would seem to be within the car's capabilities :idunno:

Any comments from the group who's had their bugs on a circuit ? I don't plan on doing any autocrosses and only limited drag racing with the Pilot Super Sports.

Thanks !

Sandeep

Bug@5speed(US) January 16th 2013 13:03

Sandeep,

While I have never done Mosport, it looks like a nice open tack with plenty of straight aways to get into top gear... I can't check the link as the sites are blocked on work firewalls..

IMHO, I would think that 150 is a little ambitious, but I do see you have about 350 HP.. and given the bugs weight, your box and ratios on paper looks possible..

How safe and stable, seems to be the question..

Never ran the Mich PSS so not sure how much of a comprise they are (Track vs DD tires). I have run the Mich PS and they were not what I would call a track tire.. On the other hand I recently ran some RE-11 on my E30, which is probably closer in weight than my old SHO, WRX or e46 i was running, and I liked them as a good track tire that was not a slick.. plus if needed can drive them around town..

If you can compromise DD, then why not get a dedicated track tire like Khumo Victor Racers or V700, or Avon's which tend to be a little cheaper as apposed to a DD/Track tire.

Also those are some big and fat wheels you are carrying at each corner.. Any thoughts on dropping down to 16's or 17's, to get into a cheaper size range? Not sure clearance on your front set up..

While I have done plenty of track events, given my cars, I tend to be in the 120-130 mph range at some open tracks.. .. Closer to the end of that spectrum I started to notice that aero would help, specially on straights (as car starts to feel a little light) and as I approached the end of a long run under braking as the weight starts shifting under braking and transition.. when you get that not so fresh feeling as the rear lights up, and the weight is shifted forward..

The only time I was at the range you speak 150-160, was with an instructor in a 911 turbo (late gen) and and a older 930 4 speed, which was geared a little short, both times was a bit concerning at times as we played with other cars at Watkins Glen.. Those cars did feel planted enough but required some BIG balls to drive hard... specially the older 930, as the turbo kicked in.. hold on tight..

I admire your valor.. if and when I get my car together, The figure I am gunning for 150-125 top end speed..

While not an answer hope it spawns futher discussion.. curious as to what others will chime in..
VR
Alex

judgie January 17th 2013 04:49

i would think it would be better to have it geared for a max of 150 @ max rpm. most race cars are set up so that they would hit peak rpm just before you need to brake. haveing it set up to hit 150 will give you plenty of margin so you dont hit the rev limiter on the straights.
are those tyre sizes not a bit on the large size? you have to turn them and that saps power even more so at speed. you will prob find your lap times come down with a narrower tyre as you can get some heat into them, wide tyres take a lot of force to get any temp in them and i dont think a bug [even with that sort of power] is going to be able to get enough heat to make them work properly.

Sandeep January 17th 2013 21:42

Thanks for the responses.

Looks like a sprint to 240 kph should be achievable based on this https://www.youtube.com/watch?v=iiZ9...e_gdata_player

I hear you on the size of the rubber / wheels but I think I will give it a shot with what I have. I can always downsize later to 17s if the need is there.

Ill be going with 245/35/18 and 275/35/18 in the Pilot Super Sport and see how it handles. Hopefully I can report back positively.

Sandeep

Luismj January 17th 2013 22:47

Quote:

Originally Posted by Sandeep (Post 85353)
Thanks for the responses.

Looks like a sprint to 240 kph should be achievable based on this https://www.youtube.com/watch?v=iiZ9...e_gdata_player

I hear you on the size of the rubber / wheels but I think I will give it a shot with what I have. I can always downsize later to 17s if the need is there.

Ill be going with 245/35/18 and 275/35/18 in the Pilot Super Sport and see how it handles. Hopefully I can report back positively.

Sandeep

Hi sandeep,

Welcome back!

i have 3,88 ring and pinion and 0,83 4 gear with 245 40 17 and 300 more hp.
Normally i go to 220 and stop. http://i712.photobucket.com/albums/w...ps130db71c.jpg
When it running at 230km/h something get serious...

Another big problem is the front T1 suspension, when i put my 944T brakes 320mm to really work it misaligned.
CB drop more camber and caster (205 45 17)
I wondered their your 245 on the front!

Luis

Humble April 14th 2013 13:34

I'll dust this off a bit...

Realistically I think 130-140 might be your limit mainly due to aero and I speak from experience. Having recently played with a mclaren mp4-12c it was nice to see the differences in aerodynamically affected acceleration. You find out on track that the bug accelerates very quick to about 90mph and that's where aero starts to hold you back. Above 90mph you have to work harder for each 10mph than that 930 on the same track. In my case, I had my rear wing on but I didn't have my front air dam on but I don't think it would have helped much on the straights. You only have so much road at a track, so hitting 150mph in any car is fast, but slowing down reliably, that's the key. I don't think you'll have any problems in the braking department :)

Luismj April 15th 2013 13:56

Quote:

Originally Posted by Humble (Post 86118)
... I don't think you'll have any problems in the braking department :)

What type of front suspension you have? And tire size?

Humble April 15th 2013 16:10

I run 87 944T spindles on 1303 arms, sectioned 944T struts with koni adjustable A1 golf/rabbit strut inserts, 87 944T 298mm disks with 87 930 calipers and master cylinder. I run a 245/40-17 semi slick in the dry or 225/50-16 summer tire for rain up front

Luismj April 16th 2013 00:06

Quote:

Originally Posted by Humble (Post 86131)
I run 87 944T spindles on 1303 arms, sectioned 944T struts with koni adjustable A1 golf/rabbit strut inserts, 87 944T 298mm disks with 87 930 calipers and master cylinder. I run a 245/40-17 semi slick in the dry or 225/50-16 summer tire for rain up front

I believe that the suspension of the 1303 is much better than the standard and no misalignment with the big brakes. :cool:

Luismj June 2nd 2013 14:51

Quote:

Originally Posted by Sandeep (Post 85353)
Thanks for the responses.

Looks like a sprint to 240 kph should be achievable based on this https://www.youtube.com/watch?v=iiZ9...e_gdata_player

Sandeep

It has stock front suspension with 7 x 17 ET55 205 40ZR 17 Tire.
http://i712.photobucket.com/albums/w...d.jpg~original

Rear: 8,5 x 17 ET50 235 45ZR 17
http://i712.photobucket.com/albums/w...c.jpg~original


I'm asked about the details to the front setup by mail, but do not received answer yet.

Luis

petevw June 3rd 2013 17:42

I'm using BFGoodrich sport comp2's on the M5. No issues to report. They work well after replacing the Michelin sport pilots.


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