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Old 08-14-2012, 02:34 AM   #1
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Will 18x9 fit on the front?

Looking to go to wider wheels on the Boxster racing car for next season and working out what I can fit.

I will be installing the rear fender flare from AIR and hope to get space for 18x11 in the rear, but how wide can I go in the front with the factory front fenders - will 18x9 fit?
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Old 08-14-2012, 06:32 AM   #2
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Yes, A 265 tire will fit on a 9" rim in front with careful attention to your offset. A 245 on a 8.5 wheel might be faster though. It depends on the tracks you run and your RWHP.
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Old 08-14-2012, 07:10 AM   #3
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Interesting. I am currently running 18x8.5 and 18x10 with Michelin Pilot Sport Cup 225/40 & 265/35.

The car is a dedicated racing car 2001 Boxster S which has been remapped. I will have to dyno the car again, but hope to be close to 300BHP. I am also running with a 2.5 5 speed gearbox with an LSD for better gearing.

Like I said above, I will be putting on the AIR Boxster rear fender flares which gives an extra 2" so could maybe even go up to a 18X11.5 or 18x12 rear wheel. I would have liked to get the current 18x10 that I am running in the rear to fit in the front as then I will only need to get new rear wheels
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Old 08-14-2012, 07:24 AM   #4
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Interesting. I am currently running 18x8.5 and 18x10 with Michelin Pilot Sport Cup 225/40 & 265/35.

The car is a dedicated racing car 2001 Boxster S which has been remapped. I will have to dyno the car again, but hope to be close to 300BHP. I am also running with a 2.5 5 speed gearbox with an LSD for better gearing.

Like I said above, I will be putting on the AIR Boxster rear fender flares which gives an extra 2" so could maybe even go up to a 18X11.5 or 18x12 rear wheel. I would have liked to get the current 18x10 that I am running in the rear to fit in the front as then I will only need to get new rear wheels
Unless you are running a 3.6L or turbo you are probably nowhere near 300rwhp. Get it on a true dyno so you know what you are working with. Oversized wheels can work well in AX but slow you down on large tracks. Too much unsprung, rotational weight and straight line rolling resistance. The fastest Boxsters in SoCal are running 245/275 tires.
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Old 08-14-2012, 07:52 AM   #5
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Unless you are running a 3.6L or turbo you are probably nowhere near 300rwhp. Get it on a true dyno so you know what you are working with. Oversized wheels can work well in AX but slow you down on large tracks. Too much unsprung, rotational weight and straight line rolling resistance. The fastest Boxsters in SoCal are running 245/275 tires.
+1 on that !
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Old 08-14-2012, 08:54 AM   #6
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Sorry, I was not referring to rwhp, I was talking about at the flywheel. The car will be going onto a dyno before the start of next season (we need to supply Hp results every three years, and mine is due for next season), so I will know for sure what the engine power is then.

I know that it is possible to go to wide, so appreciate the input.

Most of the racing tracks that we dire over here are not large fast ones like you have in the US. Ahvenisto is a good example of a track in Finland - Ahvenisto Race Circuit - Wikipedia, the free encyclopedia
"The Ahvenisto Race Circuit (Finnish: Ahveniston moottorirata) is a motorsport race track located in Hämeenlinna, Finland. The 3,040 metres (1.889 mi) long circuit is run clockwise. The track has an elevation change of 32 metres (105 ft), the home straight is 280 metres (0.2 mi) and the width varies from 9 metres (30 ft) to 17 metres (56 ft)."



I have had some on track contact this season, so the car will need body work done over the winter and I was going to use this as an opportunity to go wider. But based on what you are saying, maybe I would be better to stay with the wheel size I am already running with?
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Old 08-14-2012, 12:24 PM   #7
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There are practical limits to running wider and everything is a tradeoff. We look at data a lot and we look at top finishers. What are they doing?

Here in SoCal we have tracks of every configuration, from tight technical 1.8 mile circuits to big sweeping 3rd/4th gear tracks, to 150mph+ super-speedways. I have run a lot with 255 tires up front during testing and rarely do I find a performance advantage. Never on a track with high speed straights above 120 mph. Top speed suffers in my car with 255s up front. With only 170 rwhp I don't think my car easily overcomes the added rolling resistance, windage, and rotational unsprung weight of the larger tires. Add 100rwhp (Cayman R or 3.6L motor) and we might get a different result because hp is king on a long, high speed straight.

So if you want to win your class, consider everything: running weight, RWHP, tire compound, track configuration, rotational weight, windage, rolling resistance, and then begin to make decisions about what your ideal contact patch will look like. Once you make some tire choices, go out and test them to see how well it is working, analyze, readjust. Now you are ready to win.

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Old 08-14-2012, 03:14 PM   #8
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I am also running with a 2.5 5 speed gearbox with an LSD for better gearing.
Off topic, but I'm glad to hear this works. I had been thinking about trying this myself for the lower final drive ratio.
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Old 08-26-2012, 02:13 AM   #9
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I would be Really surprised if there is any speed advantage to be gained by going beyond the 8.5" wheels you are already running. Only a stopwatch will tell you but let me ask. Do you feel as if the car is under - tired as it stands? Also, what tires are you running and is there any restriction on what you are allowed to run?

Laurie

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Old 08-27-2012, 02:36 AM   #10
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I would be Really surprised if there is any speed advantage to be gained by going beyond the 8.5" wheels you are already running. Only a stopwatch will tell you but let me ask. Do you feel as if the car is under - tired as it stands? Also, what tires are you running and is there any restriction on what you are allowed to run?

Laurie
You are probably correct, and there will be no benefit in going wider than I already have.

Do I feel that the car is under-tired, not sure. I do feel like I could do with more grip at times, but that can also be altered with suspension and a better driver

There are no restrictions on tire make or size for us. I am running with Michelin Pilot Sport Cup. I was running with the Toyo R888 last year, but could not get used to them and find the MPSC much better.

I am currently running 1st in class and 2nd overall in the 2012 Porsche Sports Cup Scandinavia season here in Finland, and just looking for that extra advantage for next year and thought that maybe a bit more rubber on the track might help?
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Old 08-27-2012, 02:22 PM   #11
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Are Hoosiers available where you are? If so they would certainly be quicker. Slicks (from any of the major makers) would be faster again. I'ld be looking there before thinking 1/2inch of extra wheel. R888s are **************** as all of us who drove them in SpecBox last year found out.
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Old 08-28-2012, 01:33 AM   #12
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I think we can get Hoosiers from the US, not sure if they are available here in Finland. I know I said we are free on tiers, but that is not quite true. They must be EU approved road legal, and I am not sure if the Hoosier is approved for road use in EU?

Slicks could be run, but that will put me in a higher class with the GT3 Cup cars and will require changes to suspension and alignment settings.

I am for now happy in the class I am in. There is good competition and I am not winning every race I enter, so still a good fun race. But there are more 996 cars coming into the class and I am having problems keeping them behind me - they are faster, so any advantage I can get I want to take...
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Old 08-30-2012, 01:14 PM   #13
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Yes, the 18x9 will fit on the front. That is what I'm running now with the 250 front slicks. You may able to roll the fenders and cram a 9.5" in there but you really don't need to at your power levels. I prefer a larger front for the better braking and longer lasting front tires during a race, but there is definitely a point of "too big".


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Old 08-30-2012, 09:40 PM   #14
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Thank you Eric, we have also had the same discussion on the front wheel fitment on another forum

But now that I know that it can fit, then question that is coming up here is if it is a good idea for me to go to a wider front and rear set-up or stay as I am - what do you think Eric?
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Old 08-30-2012, 10:00 PM   #15
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Thank you Eric, we have also had the same discussion on the front wheel fitment on another forum

But now that I know that it can fit, then question that is coming up here is if it is a good idea for me to go to a wider front and rear set-up or stay as I am - what do you think Eric?
For a 3.2L Boxster, I would want more than a 225/265 pair. A 245/275 would be nice and is available, or even a 255/285 with DOT tires. It does does depend a bit on the track you run, but I would always want more than a 225 DOT(or EU equivalent street rating) to get the most out of that car in the front. You are running almost Boxster spec sizes with another 100hp, and a bit more weight I believe. So I would expect the additional footprint could be put to good use.
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Old 08-30-2012, 10:42 PM   #16
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Thank you for the recommendations Eric. My initial plan (and a way to try and keep cost down) was to try and move my current rear wheels to the front and then go 2" wider on the rear. This would give me 18x10 on the front and 18x12 or 18x11.5 on the rear.

Do you think this would be a good fit for my car or am I starting to go to wide?

Yes, the car is a 3.2 which has been remaped to get as much power from it as possible. It is also running with a 2.5L 5 speed box with a competition LSD to get better gearing and acceleration for the tracks that we have over here...
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Old 10-11-2012, 01:31 AM   #17
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OK, so the car is now in the body shop getting the scars from the 2012 season removed, and the front and rear fenders getting widened. I will get an extra 1.5" - 2" on the front and an extra 2" - 2.5" on the rear. This I hope will give me more options on wheel size etc.

I run with Michelin Pilot Sport Cup, and looking at available size to fit a 18" wheel I am considering going for 295/30 - 18 at the rear and 265/35 - 18 on the front.

Initial thought is to get a 18x10 wheel on the front and an 18x12 on the rear, and this leaves me with a question - what offset do I require to make the wheels fit the Boxster?
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Old 10-11-2012, 07:07 AM   #18
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Unless you are running a 3.6L or turbo you are probably nowhere near 300rwhp. Get it on a true dyno so you know what you are working with. Oversized wheels can work well in AX but slow you down on large tracks. Too much unsprung, rotational weight and straight line rolling resistance. The fastest Boxsters in SoCal are running 245/275 tires.
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+1 on that !
He did not say 300RWHP, he said 300BHP, which is certainly attainable with a 3.2 motor, if not economical. Putting a 3.6 in a Boxster has to be at least a $10,000 undertaking unless your labor is free.

If things like emissions, efficiency and streetablity are of no concern, 300BHP should not be a huge undertaking for a 3.2, nor insanely expensive.
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Old 10-11-2012, 07:37 AM   #19
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He did not say 300RWHP, he said 300BHP, which is certainly attainable with a 3.2 motor, if not economical. Putting a 3.6 in a Boxster has to be at least a $10,000 undertaking unless your labor is free.

If things like emissions, efficiency and streetablity are of no concern, 300BHP should not be a huge undertaking for a 3.2, nor insanely expensive.
Regardless if it's WHP or BHP, that's way too much unsprung rotational mass to effectively improve performance on any level.
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Old 10-11-2012, 07:50 AM   #20
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Regardless if it's WHP or BHP, that's way too much unsprung rotational mass to effectively improve performance on any level.
OK, so I need to go smaller - how about 265/35 on front and 295/30 in rear?
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