[TDIwyse]

Originally Posted by mob17

I suppose i could, but it would just look weird with 19" CSL type alloys on the front and 17" on the back!

On the front currently i've got 245/35/19 PSS, which i think have a high rolling resistance. Would changing that to a 225 "economical" 17" tire make much reduction to rolling resistance, or is there not much point and better to save the money?

You'd save weight on the wheels by going to 17's for sure, and they'd be easier to accelerate. IIRC the PSS's are pretty decent for rolling resistance. The vast majority of your HP losses will be due to wind drag at the top (at 115mph you'd have ~ 66 hp of wind drag losses for a Cd of 0.31 and FA of 21.6 ft^2 ... far more than the rolling resistance).

[mob17]

Originally Posted by TDIwyse

You'd save weight on the wheels by going to 17's for sure, and they'd be easier to accelerate. IIRC the PSS's are pretty decent for rolling resistance. The vast majority of your HP losses will be due to wind drag at the top (at 115mph you'd have ~ 66 hp of wind drag losses for a Cd of 0.31 and FA of 21.6 ft^2 ... far more than the rolling resistance).

Thanks for the insight TDI, i must be mistaken then i always thought PSS were quite average to poor for rolling resistance.

I'm thinking to get a set of OEM E39 17inch staggered alloys. Can get them cheap for around £150 for a set of 4. Just need to try and find an adaptor as the centre bore sizes are a bit different to the E9X. The E39 alloys come in 8j and 9J so i was thinking i could put some eco tires on the front (225) and hopefully some 275 Hoosiers DOT radials on the rear. Just need to confirm if the Hoosiers are road legal for the 15 mile trip to the drag strip. Then perhaps get some winter tires on them in the winter...

This spend will be coming out of nowhere, i was planning to get my solid rear subframe bushes and stiffer springs on. Plus who knows what my indy will find tomorrow, with the power issue of the car. Why did i go to that drag strip

[TDIwyse]

Originally Posted by mob17

Thanks for the insight TDI, i must be mistaken then i always thought PSS were quite average to poor for rolling resistance.
...

I haven't directly measured it myself, but this comment is based on comparitive mpg results with PSS vs other tires I've used. Also comments like this make me they're not bad for rolling resistance.

http://www.consumersearch.com/tires/...ot-super-sport

Reviewers disagree on how fuel efficient these tires are. Two separate reviews by TireRack.com say the rolling resistance on the Pilot Super Sport is the lowest to maximize fuel efficiency, but a test from a leading consumer organization says rolling resistance is only average.

[mob17]

Thanks for the info tdi.

Just measured my tire tread. The rears were 3mm in the inside and gradually went to 5mm on the outside. I'm hoping when i have fresh pss rears i may be able to do better (if i dont go the hoosier route).