Wheel size for trackday

[xht20]

Sorry if this has already been discussed but i can't find...

For a track day, an 18" wheel with semi-slicks is 10 times better than a 19" wheel with semi-slicks?  Because a friend wants to upgrade his front brakes with Brembo GT 6-piston 380x34mm discs and it appears that only 19" wheels can clear the disc diameter.

What do you think? The differences beetween 18" and 19" with semi-slicks on track are so big that it's better not to upgrade the front brakes?  He goes on a track not so often

Any help would be apreciated

Cheers mates

[tony_danza]

Unless his car is 2 tonnes and 500hp+, those brakes are a stupid idea. He'll never get them hot enough.

18"s are much cheaper and the wheel/tyre combo is lighter that 19"s, thus better.

[btowery]

I'm posting to an old thread but, new to this forum, I thought it useful to share my experience.
I’m a former IMSA racer, now Chief Instructor at Chin Motorsports the largest presenter of track days in the Southeast USA. I do a lot of track days in my MK5. I prefer 17" wheels for these related reasons: 1) running a 235X45 17, I'm putting a lot of rubber on the ground with minimal weight--my OZ 8.5" wheels weight just over 16 lbs each; 2) the taller sidewall gives me a lot of pneumatic adjustment; the easiest at track set up change for a busy day at the track with no crew; and, finally, but not last in importance, 3) 17" tires are significantly less expensive.

[teo_parvu]

You're right. 
 I've seen a video where they compared the 17" wheels with the 18" wheels on the same GTI on a racetrack.
The 17" wheel generates better traction so the lap times were better.
The problem is that you cannot do serious trackdays with the stock GTI brakes, they will be cooked in 3-4 laps.
If you upgrade the brakes, for sure the 17" wheels will no longer fit.     

[Erno]

You're right. 
 I've seen a video where they compared the 17" wheels with the 18" wheels on the same GTI on a racetrack.
The 17" wheel generates better traction so the lap times were better.
The problem is that you cannot do serious trackdays with the stock GTI brakes, they will be cooked in 3-4 laps.
If you upgrade the brakes, for sure the 17" wheels will no longer fit. 

It depends on the upgrade. I think that the NQSBBK with the stock discs fit 17 inch wheel...

[rich83]

If i was running a car on the track lots then 17s definitely. AP racing do a brake kit that will go under 17s as do the NQSBBK (as above)

[teo_parvu]

I know about it. CP5200 caliper and 330x28 discs. 
There are some solutions, but don't know if they are enough for a serious k04 setup.
But I was running the stock Cupra/S3 calipers with Tarox F2000 discs and Carbotech RP2 pads with 17" Federal FZ-201. I had super stopping power and laptimes.
But on my last trackday, after 4 sessions, the calipers were black, the pads gone (melted) and the seals burnt. You can see the result on my thread.

So I bought AP Racing's CP5575M1011R2.CG12 and new 18' wheels. I'm not sure if this will be enough without ducts. 

[fuscobal]

NQSBBK is a decent kit but far from competitive on a heavily modified k04. Our friend Rex with his 160HP Golf had fade with this kit towards the end of the session. Imagine how it would do on 380HP cars braking from speeds 40kmh higher on a straight ! For our cars, the best tire/brake compromise would probably be on 18" wheels with aftermarket 330-370mm brakes !

[DaveB@Vagbremtechnic]

We've got a 343mm floating kit that should fit under a 17, I'm just waiting for the guy who's running it to come up with a review/discussion thread as he's undertaken to do.

343 is very optimal for a Mk5 its on the cusp of needing to be floating so we'll be offering it bolted and floating .

The customer was in a stage 2 Pirelli and completed over 100 laps in 10x10 sessions and evidently was scaring the bejezus out of all sorts of exotica, Alex AKS fitted it (as he does with most first time kits)

Its got reasonable consumable prices too, by all accounts it worked exactly as intended zero fade over 2-300 track miles, non pro driver, available to be driven to work the following day. Im hoping that it will become the baseline Mk5/6 track kit for serious track day enthusiasts who want to run a 17" track wheel but fancy some brakes that will hold its own behind a 18/19 street wheel

The track day above was done on the floating setup and Pagid RS4-2.. Pricing isn't finalised but as fitted it was less than £2k

Some may recognise the poor camera skills and messy workshop floor

Edit: The rotor is a homologated item from the Astra VXN race series thats exclusively at the ring so its got some pedigree

[teo_parvu]

This would have been the best solution for me, I tried to contact you.
I had to sell my track wheels and get new ones so that the AP Racing BBK would fit. I used to run 17"s :))

[Hurdy]

I have always run 18's with both the Edition 30 and latterly my Golf R.

The Golf R ran 362mm AP racing 2 piece discs with HEL braided lines, Project MU race pads under 8 pot R8 calipers. They ran flawlessly at the ring under 18"x8" Team Dynamics Pro Race 1.2's with Toyo R1R rubber. A little tricky with the tyres as the car hit 200mph indicated a few times between the gantry and the bridge and aren't actually rated to that!!!

18" alloys may not be the BEST size for track, but they are the best compromise if you wish to run a decent brake upgrade. The 362mm AP Racing discs have been used in the VLN Races on the VAG cars, which says a lot for their capabilities.

[fuscobal]

Are you sure about those 200mph (320km/h) ?