Worth the price difference?

[20redfire03]

I'm looking into getting a set of rear rims/tires for the drag strip. I have narrowed down my choices to the following:

15x8 Race stars with 275/50/15 ET Streets (25.8" Tall) or 17x9 rims with 275/40/17 (25.7" Tall)

The race star set after adding the lugnuts is about 120$ more. Is the benefit of less weight worth the extra price? The 17x9 rims would be 10th Ann. replicas from American Muscle.

 

[dirtyd88]

Less rotational weight is always a positive thing. The rear tires will now spin easier since they are lighter and will make the car work less to go down the track.

 

[wile2k]

Watch for a used set if you have a little time, I've seen people selling a rear set with tires in the market frequently.

Here are my thoughts on 15 vs 17, just went through weeks of trying to figure this out...

15s are generally lighter all around (6.5lb per wheel in your example and probably another lb or two per tire) and have a better selection of drag tires to choose from. Unsprung weight is a bigger deal, most people agree that 1lb of unsprung weight is equivalent to 4lb of sprung weight. If you are an M6, then more sidewall is nice for absorbing the launch too. I went with a 17 because I want to leave the wheels and tires on and generally I don't like the 15 rear 17 (or bigger) front look and didn't want to go through the trouble of 15 front and rear. My 17s though are a light weight rim and I'm not losing a ton compared to an equivalent 15, the tradeoff was worth it to me.

You already have the relocation brackets, so that isn't a worry in your case either.

If I was in your shoes, with what you are describing, I'd watch for a good deal on wheel/tire in market first and definitely go 15s.

On your tire size, again, stick or auto? Those tires are a little short, which could help gearing (and a very small amount of weight compared to something 26.5" - 27.5") if you need that help, but will also have a little less sidewall and look a little small if you care about such a thing.

 

[20redfire03]

Car is an A6. And I've seen a 275/60/15 in person and seems like it may not fit or could possibly have contact. Also, at least from what I've gathered a shorter tire would be better with the 3.15 rear gear but I could be wrong.

 

[wile2k]

I guess it depends on how low you are, I'm not worried about running a 28" tire (actually 27.2 which is stock height) on my new wheels but I'm only going for a small drop in the rear and the front is only "lowered" by the weight of the Paxton. Contact with the fender is really determined by offset and most of the drag specific wheels wont have an offset issue with a 275 (the offset is less aggressive specifically to accommodate some tire bulge). The 17, I'm less certain of, the offset is a bit more aggressive (similar offset equivalent to an SVE drift) and yeah, you might not want a lot of extra tire hanging out beyond it depending on how much you are lowered.

Agree with the smaller tire helping the 3.15, I have crap 60' and will continue to do so. It isn't a problem for me though since I don't plan to cage the car this year and it will be hard enough to keep it above a 11.50 anyway. The biggest disadvantage on the smaller rear tire is going to be looks and if that doesn't matter to you then it is probably a win win with an auto and 3.15 rear. That is my take anyway FWIW, just sometimes helps to talk it through.

 

[nicostang]

I have a "stockish" 2012 A6 with 3.15 gears and from my personal experience at our track which has almost no prep a 275/40/17 NT05R would hook about 60% of the time with long burnouts. Car would also wheelhop in some cases. The car was VERY inconsitent. I was getting 2.0 to 2.3 60 foots which is terrible for a drag radial. on top of ALL of that, the 17x9 wheel/tire combo was MUCH heavier.

I then switched to MT ET Pros 275/60/15 on 15x10 rim and the car hooks 100% of the time with a small burnout. The difference is substantial. The car was so consistent that all of my 9 runs were within .1 of each other.

Don't worry that mcuh about gearing. The A6's first gear is pretty steep and the main factor that holds the car back is the stock converter. I tried everything I could and couldn't get a 60 foot better than 1.9. The main reason is that the 5.0 is very soft under 3000rpms which is where the stock converter would flash. Once the car gets over 3500 RPM the front starts to lift and the car is a rocket