17" vs 15" wheels pros and cons Options

[moggy]

I don't seem to see many 914 circuit racers with 17" wheels on. Everyone seems to stick to 15". Is there a reason for this? I'm less bothered about the looks of 17" vs 15", I'm more interested in this from a performance perspective. Who out there has tried both wheel sizes? what size did you decide on, and why?

I personally have 15" (Cookie cutters 7" wide all around)
(IMG:http://www.914world.com/bbs2/uploads_offsite/i31.photobucket.com-3285-1440357310.1.jpg)


and 17" (Cup1 7"front 9"back)

(IMG:http://www.914world.com/bbs2/uploads_offsite/i31.photobucket.com-3285-1440357310.2.jpg)

At the moment, I'm forced to use the 17" on tracks where I need the top speed, due to my low ratio gearbox (a hangup from when it was a rally car). The 17" wheels have a 26" overall diameter. Whereas the 15" wheels are used on slower, twisty tracks.

There is a huge weight difference between the wheels (including tyres) of 32kg (70.5lbs) total, which is an obvious benefit to sticking to the 15 "cookie cutters. But weight can't be the only reason why you circuit racers stick with the 15", so what are your reasons?

[john914somers]

I've been on 17" twists but was thinking about going to 15" merely for the weight and smaller diameter options. An old racer told me that I would be going backwards if I did that and that everybody generally needs to go to something bigger than 15" because of the fitment of bigger brakes. I have a 3.6 and a 915 so I'm probably heavier than most guys and the speeds I'm running I think bigger brakes are a must. I did pick up some 15" Wheels and they don't clear my rotars. Consequently I'm back to looking for some lighter 17's and even considering some 18's but I'm not certain they will fit??? Can someone chime in on 18" fitment? Thanks!

[stownsen914]

Let me throw in there too that 17 and 18 inch wheels, even when run with low profile tires, tend to be larger in diameter than 15s. This doesn't work well on older cars due to limitations in how much you can lower the suspension and also inner and outer fender clearance. I've seen 914s and older 911s running larger diameter wheels and having to run the car at artifically high ride height. Seems like a bad plan to me unless you just like the look of the larger wheels and prioritize that over performance.

I run 16" wheels with slicks on my 914 racecar. I've already made changes in the suspension and bodywork to run the car very low with the 16s. I've contemplated running 18s, but I'd have to make more changes to the front bodywork and I'm not sure the 18s would give me a significant performance advantage.