Rim/tire size choice for track

[fuscobal]

I am now running 225/45/17 on standard 7.5'' GTI rims wich was a much better setup for track than my first 235/35/19 Goodyear F1 Asymmetric street tires. However, in about 2 weeks I'll be installing 6POT 362x32mm AP Racing brakes wich will require 18'' wheels. As I'm gonna buy these anyway, I was thinking of going 8.5'' (instead of 8'') wich will allow me to run 235 and 245 tires as recommended by Toyo, Kumho...for semislicks.

The data to take into account for this choice will be :

1) 370HP/475NM
2) 1450-1500Kg including driver & gas
3) TT arms in front wich throw the wheels about 7-8mm out of the wheel arch with 235/35/19 on 8.5'' rims
4) 245 tires may cause rub on the rear

Tire sizes/recommendations from different manufacturers :


Tire size > Overall diameter > Overall width > Tread witdh > Optimum rim width > Rim width limits > Sidewall height (given by tyre calculators) > Difference in diameter from stock tire (recommended <3%)

Kumho V70a

225/45/17 > 628 > 224 > 207 > 7.5'' > 7'' - 8.5'' > 101.09mm > 0% (stock size)
225/40/18 > 631 > 229 > 212 > 8'' > 7.5'' - 9'' > 89.92mm > 0.44%
245/35/18 > 624 > 251 > 234 > 8.5'' > 8'' - 9'' > 85.60 mm > 0.89%

Toyo R888

225/45/17 > 635 > 231 > ? > 7.5'' > 7'' - 8.5'' > 101.09mm > 0% (stock size)
225/40/18 > 637 > 224 > ? > 8'' > 7.5'' - 9'' > 89.92mm > 0.44%
235/40/18 > 648 > 244 > ? > 8.5'' > 8'' - 9.5'' > 93.98mm > 1.70%
245/40/18 > 653 > 249 > ? > 8.5'' > 8'' - 9.5'' > 97.79mm > 2.88%

Yokohama A048

225/45/17 > 632 > 226 > 223 > 7.5'' > 7'' - 8.5'' > 101.09mm> 0% (stock size)
225/40/18 > 635 > 231 > 216 > 8'' > 7.5'' - 9'' > 89.92mm > 0.44%
235/40/18 > 645 > 244 > 226 > 8.5'' > 8'' - 9.5'' > 93.98mm > 1.70%


Dunlop Direzza 03g is too expensive and I can find no sizes on the internet. As you can see, for 235 &245 tires, the optimum rim would be 8.5'' and the minimum 8''. As I said on point 3), my 235 tires on 8.5'' rims stick out of the wheel arch about 8mm due to the TT arms so running 235&245 tires with 8.5'' rim will require new wings (Kerscher wings are about 20-25mm wider so they give plenty of clearance for these tires). As the price of the 8'' vs 8.5'' rims will be the same (TD 1.2 pro race) and the 225 vs 235/245 tire will also be similar, the only added cost will be the Kerscher wings at 650 Euros + painting (another 200 Euros). The final question is if the added grip of 235/245 tires over 225 deserve the extra money for the new wings. Aslo, I would like to have enough sidewall to properly help the suspension over bumps (245/35/18 seem to lack sidewall here) but not too much to avoid flex (245/40/18 has the biggest sidewall but still smaller than 225/45/17)

PS : As you can see, for the same size, there are great variations in overall width and tread width between various manufacturers !

Hopefully you'll have the patience to follow this topic and will also help you guys in the future choosing tires/rims for our mk5 chassis !

 

[bostonaudi]

I am now running 225/45/17 on standard 7.5'' GTI rims wich was a much better setup for track than my first 235/35/19 Goodyear F1 Asymmetric street tires. However, in about 2 weeks I'll be installing 6POT 362x32mm AP Racing brakes wich will require 18'' wheels. As I'm gonna buy these anyway, I was thinking of going 8.5'' (instead of 8'') wich will allow me to run 235 and 245 tires as recommended by Toyo, Kumho...for semislicks.

The data to take into account for this choice will be :

1) 370HP/475NM
2) 1450-1500Kg including driver & gas
3) TT arms in front wich throw the wheels about 7-8mm out of the wheel arch with 235/35/19 on 8.5'' rims
4) 245 tires may cause rub on the rear

Tire sizes/recommendations from different manufacturers :


Tire size > Overall diameter > Overall width > Tread witdh > Optimum rim width > Rim width limits > Sidewall height (given by tyre calculators) > Difference in diameter from stock tire (recommended <3%)

Kumho V70a

225/45/17 > 628 > 224 > 207 > 7.5'' > 7'' - 8.5'' > 101.09mm > 0% (stock size)
225/40/18 > 631 > 229 > 212 > 8'' > 7.5'' - 9'' > 89.92mm > 0.44%
245/35/18 > 624 > 251 > 234 > 8.5'' > 8'' - 9'' > 85.60 mm > 0.89%

Toyo R888

225/45/17 > 635 > 231 > ? > 7.5'' > 7'' - 8.5'' > 101.09mm > 0% (stock size)
225/40/18 > 637 > 224 > ? > 8'' > 7.5'' - 9'' > 89.92mm > 0.44%
235/40/18 > 648 > 244 > ? > 8.5'' > 8'' - 9.5'' > 93.98mm > 1.70%
245/40/18 > 653 > 249 > ? > 8.5'' > 8'' - 9.5'' > 97.79mm > 2.88%

Yokohama A048

225/45/17 > 632 > 226 > 223 > 7.5'' > 7'' - 8.5'' > 101.09mm> 0% (stock size)
225/40/18 > 635 > 231 > 216 > 8'' > 7.5'' - 9'' > 89.92mm > 0.44%
235/40/18 > 645 > 244 > 226 > 8.5'' > 8'' - 9.5'' > 93.98mm > 1.70%


Dunlop Direzza 03g is too expensive and I can find no sizes on the internet. As you can see, for 235 &245 tires, the optimum rim would be 8.5'' and the minimum 8''. As I said on point 3), my 235 tires on 8.5'' rims stick out of the wheel arch about 8mm due to the TT arms so running 235&245 tires with 8.5'' rim will require new wings (Kerscher wings are about 20-25mm wider so they give plenty of clearance for these tires). As the price of the 8'' vs 8.5'' rims will be the same (TD 1.2 pro race) and the 225 vs 235/245 tire will also be similar, the only added cost will be the Kerscher wings at 650 Euros + painting (another 200 Euros). The final question is if the added grip of 235/245 tires over 225 deserve the extra money for the new wings. Aslo, I would like to have enough sidewall to properly help the suspension over bumps (245/35/18 seem to lack sidewall here) but not too much to avoid flex (245/40/18 has the biggest sidewall but still smaller than 225/45/17)

PS : As you can see, for the same size, there are great variations in overall width and tread width between various manufacturers !

Hopefully you'll have the patience to follow this topic and will also help you guys in the future choosing tires/rims for our mk5 chassis !

From experience, you are headed down one very expensive road indeed.

Are you racing, or just track event (weekend DE)?

Brakes do dictate wheel size, depending on what your doing, I'd likely suggest widest tire that will fit and still maintain correct outer diameter, which would be 245-35-18. I run 245-40-17 and the extra width helps. Yes the smaller sidewall will also influence choice and spring and damping levels.

I also run TT arms, they do push the wheel out. Most wheels in 18" size run ET45, so clearance with wings (fenders) will be a potential issue. If you keep the car near stock height it will clear, as long as they clear the struts. I run my car at 360f/350r mm fender to wheel center, no rubbing and car rides and handles best. This is less than 10mm from stock height down. Stock height on my USA 08 GTI 4dr was measured at 368f/355r.

I'm also finding its best to stick with Jap or Euro tires, Korean tires still don't seem as well developed as the usual players. In a 245-35-18 you could also consider a tire like the Kuhmo Ecsta XS, which friends have reported good results with.

To keep things much more affordable, you could also use R32 brakes up front and stay with 17" wheels. A full set of R32 brakes is powerful on a GTI and should handle your power without issue. I'm running a K04 and at the track the R32 brake setup is excellent. I'm also running RB lightweight 2 pc rotors.

My car as it currently sits, almost stock height, TT arms, R32 brakes, track ready, no clearance issues whatsoever with my stock or track wheels/tires.

 

[fuscobal]

Thanks for your reply Boston. First of all, I already have F+R R32 brakes wich have been great with Carbotech pads but I already purchased the AP Racing brakes wich should improve things even more while bringing the weight down by 12-14Kg wich is a lot ! I will keep the R32 brakes + Carbotech XP8 pads on the rear. My ride height now is about 340 wich is lower than yours but don't get rub with 235/35/19 street tires. However, on the track & with semislicks the car will definately lean more !

 

[bostonaudi]

At ride height 340 you may have front fender clearance issues on bumps. Another 10mm up should keep things from hitting. At 350 the increase in ride quality and handling over 340 is somewhat staggering.

Did you buy the racing brakes just for weight reduction? You can also save weight and a ton of cash by staying with your already excellent R32 brakes and going with lightweight rotors. The cost increase to go to 18" track tires in the sizes you are proposing is huge, most good tires in that size are $280-350 ea. The RB rotors are expensive up front, but should last long time and can stay with 17" tires.

 

[fuscobal]

Got the brakes SH at half the new price (they have under 5000km on the street) and the difference in price for the Kumho V70 tires is from 180 to 210 Euros/piece, meaning 120Euros for all 4 wheels wich is not too much ! Hopefully I will get another 2Kg/wheel from the TD 1.2s wich are 1.5Kg lighter than my 17'' OEM Denvers ! I also have the TT arms and S3 hubs wich brought a saving of about 2.5Kgs/corner !

Boston, being you're on stock rims (ET51) and your 245s don't rub on the damper it should be even better for me with ET45 !

 

[bostonaudi]

Got the brakes SH at half the new price (they have under 5000km on the street) and the difference in price for the Kumho V70 tires is from 180 to 210 Euros/piece, meaning 120Euros for all 4 wheels wich is not too much ! Hopefully I will get another 2Kg/wheel from the TD 1.2s wich are 1.5Kg lighter than my 17'' OEM Denvers ! I also have the TT arms and S3 hubs wich brought a saving of about 2.5Kgs/corner !

Boston, being you're on stock rims (ET51) and your 245s don't rub on the damper it should be even better for me with ET45 !

My track wheels are 17x8 Enkei PF01, with 245-40-17 Direzza's. Wheels are ET50. The tires are within 3mm of the strut, and do hit the fenders if I run the suspension too low and hit bump, so there is very little room to play with. If you get everything to fit OK the lighter weight will make difference. But with 370 hp on tap you don't have to go too crazy losing weight!

 

[fuscobal]

245 is on the minimum recommended of 8'' for the rim. I'm now looking at TD website > http://www.teamdynamicsracing.com/pro-race/Pro-race12.htm > and I see there is only 8'' and 9'' but no 8.5'' so if I''m going to use 235 or 245, I will have to put them on 8x18'' and not 8.5x18''. Can this be a problem if the car is heavy ? (like tire going off the rim under hard cornering). They do recommend 8.5'' as optimum but what's the difference if using the minimum of 8'' ?

 

[wizzo]

What is the perfect ride height for handling, from fender to centre of wheel? Was just wondering, it may also help OP's decision

 

[wizzo]

Op im running 245/40R18 on TD 1.2 Pro Race Rims, love everything about them.. even though future plans hold 18x9's for front running 265 and 18x8 for rear with 245

 

[fuscobal]

wizzo, 245/40R18 on 8x18'' I suppose ? What ET ? After Bostonaudi, you are the second guy I see running 245 on the minimum adised of 8'' ! Any fender rub ?

 

[the bruce]

Seems the American GTIs have much more space inside the fender. :biggrin:


I'd love to have 235/40 R18 semis with my 8x18 ET44 BBS, but I'm really scared of rubbing my fenders.
In addition I'm gonna install the TT arms at the same time.

Height is 340 and 333 mm, which I'd like to stay with.

Fusco, the outstanding Direzza 03G as 225s have more grip than other as 235s or 245s.
They beat the highly regarded PS Cup and the V70a.

 

[wizzo]

im running 18x8 et45, i have very stiff suspension? maybe that helps, dont know if ud rub on other setups

340 front and 333 rear?

 

[Gotsol]

I have the TT arms, 18x8 ET 45 wheels with 245/35-18 kumho XS tires at stock R32 ride height. The tires do stick out past the fenders by 3-4mm on each side. I've only had the tire hit the fender once on a bump mid turn. I haven't tracked it yet but am concerned that it might hit at auto cross or over curbs.

I also have the two-piece rotors, where are fantastic.

I'd recommend 234/40-18 for you.

 

[bostonaudi]

I have the TT arms, 18x8 ET 45 wheels with 245/35-18 kumho XS tires at stock R32 ride height. The tires do stick out past the fenders by 3-4mm on each side. I've only had the tire hit the fender once on a bump mid turn. I haven't tracked it yet but am concerned that it might hit at auto cross or over curbs.

I also have the two-piece rotors, where are fantastic.

I'd recommend 234/40-18 for you.

Your R32 must drive well with the front RB's and TT arms. Stock R32 rotors are boat anchors. If your tires rub at all on bumps you should address it. The suspension needs to move over its entire travel without things hitting.

At track or autocross our cars need suspension travel, and room for the wheels to move.

I would totally agree you can find über sticky tires in the stock size and do just fine, and then not worry about all these complications.

A few gratuitous shots of my car at Road Atlanta from last year. This was before my TT arms (this was my first weekend there with the FSB installed, the car drove fantastically). You can see that even on long sweepers at speed (these weren't tight corners) there is quite of a bit travel going on. Unless you are running extremely tight springs, you've got to keep the car up some to avoid rubbing, and to keep the suspension working right. With the TT arms I raised car back to 360f/350r, no problems, car rides and handles much better.

In fact, I would challenge anyone running lower (like 340) to go out to their garage now (I mean right now) raise car to 360/350, go out for drive, and then come back and tell me it didn't run a lot better. Raising the car 10-15mm will not affect alignment.

Car setup in these shots was with my 245-40-17 Direzza's on Enkei PF01 17x8 with ET50. Front camber is stock. Car is mildly lowered (at the time it was around 350f/345r.

Cornering under load - note how much travel the rear wheels need (exiting 10b).

Note there isn't much room between tires and fenders (turn 3):

Note how far rear tires have tucked under acceleration and cornering :

 

[bostonaudi]

Seems the American GTIs have much more space inside the fender. :biggrin:

Fusco, the outstanding Direzza 03G as 225s have more grip than other as 235s or 245s.
They beat the highly regarded PS Cup and the V70a.

we wish! we also wish 03G were here too!