Toyota GR86, 86, FR-S and Subaru BRZ Forum & Owners Community - FT86CLUB - View Single Post

diss7 · 02-23-2013, 03:53 PM

I'm FINALLY taking delivery of my car on Monday. Even though it arrived on Thursday, apparently it takes more than two days to do a groom. Even more annoying was driving past the dealership last night and seeing the car just sitting in the showroom!

So I went and ordered my tyres, 205/40/17's. Why did I go with this size?
They have the lowest circumference of any feasible option. 195/45/16 would've been even smaller, but that would've been taking the point too far. Also, I wouldn't be able to fit the brakes I want under a 16" rim, and I'd already bought 17s anyway.

Why am I focused on a small circumference wheel? Well it has numerous benefits. For a start, less unsprung weight = better handling. Secondly, smaller circumference tyre = effectively shorter gearing = better acceleration & braking. Thirdly, lower COG.
Regarding COG, a lot of people confuse COG with wheel arch gap. If you put a bigger radius wheel and tyre on from stock you are RAISING the COG.
Putting my wheel/tyre on lowers my COG 18mm over a stock setup. Straight away, my COG with stock suspension is probably lower than another setup with massive rims and tyres and coilovers.
Running my setup with stock suspension will look a bit rude though, as the down side to all this is that I end up with more wheel arch gap. But, of course I can add coilovers with will lower my COG further and reduce this arch gap. Also, because my wheel/tyre is smaller, I'll be able to going lower before I have any form of rubbing/fouling; should I feel the need to go that low.

02-23-2013, 03:53 PM	#1
diss7 Banned Join Date: Sep 2012 Drives: AE86, 2x GT86, TE27 Location: Christchurch NZ Posts: 1,478 Thanks: 826 Thanked 1,181 Times in 522 Posts Mentioned: 33 Post(s)	New tyres 205/40/17 I'm FINALLY taking delivery of my car on Monday. Even though it arrived on Thursday, apparently it takes more than two days to do a groom. Even more annoying was driving past the dealership last night and seeing the car just sitting in the showroom! So I went and ordered my tyres, 205/40/17's. Why did I go with this size? They have the lowest circumference of any feasible option. 195/45/16 would've been even smaller, but that would've been taking the point too far. Also, I wouldn't be able to fit the brakes I want under a 16" rim, and I'd already bought 17s anyway. Why am I focused on a small circumference wheel? Well it has numerous benefits. For a start, less unsprung weight = better handling. Secondly, smaller circumference tyre = effectively shorter gearing = better acceleration & braking. Thirdly, lower COG. Regarding COG, a lot of people confuse COG with wheel arch gap. If you put a bigger radius wheel and tyre on from stock you are RAISING the COG. Putting my wheel/tyre on lowers my COG 18mm over a stock setup. Straight away, my COG with stock suspension is probably lower than another setup with massive rims and tyres and coilovers. Running my setup with stock suspension will look a bit rude though, as the down side to all this is that I end up with more wheel arch gap. But, of course I can add coilovers with will lower my COG further and reduce this arch gap. Also, because my wheel/tyre is smaller, I'll be able to going lower before I have any form of rubbing/fouling; should I feel the need to go that low.