Wheels/tires for daily-driver & time trials...

[ZDan]

I'm about to start getting my car ready for track work. Plan is to get 1" lowering springs (probably Swift Sports), camber bolts, maybe front sway bar, and wheels/tires. Keeping the stock PP Sachs dampers to save on $$$ and points for my class.

For tires, I'm thinking RE71Rs, either 225/45-17 on 17x8 , or 245/40-17 on 17x9. *Maybe* NT01s in either 225/45 or 235/40-17...

I'm not planning to run camber plates, so gonna be limited on front camber, hoping to get at least -2, maybe as much as -2.5 with SPC bolts in lower hole and factory lower bolt in upper.

I gather that the 245/17x9 route would require an offset in the +35 to +38 range to allow max camber adjustment. Seems like it'd be an awful lot of poke, with outside wheel lip at +32mm out vs. stock :O

225/17x8 should allow max camber with just about any offset wheels, no worries.

Just pondering whether I'm going to go the easier and cheaper way, or tough it out and go big. But I don't know if 245 vs 225 is really going to be a big advantage on this car at stock power...

[Racecomp Engineering]

245 vs 225 is not a big advantage at the track. May not be faster at stock power depending on track and driver. And 225 will make life easier for fitment and IMO slightly better for the street (minor things like 245s with poke kicking up a bunch of rocks all over the side of your car). Save points and money is my recommendation.

- Andrew

[ZDan]

Had beers w/ club's BRZ hotshoe last nite, plates highly recommended to get needed -3 or more camber, so I might go that route after all. Which opens up the wheel/tire options a bit. 17x9 +40 6ULs or Apex Arc-8 +42 w/ 245 RE71Rs are tempting...

$$$ and practicality still point to camber bolts and 17x8/225s.

[venturaII]

Originally Posted by Racecomp Engineering

245 vs 225 is not a big advantage at the track. May not be faster at stock power depending on track and driver. And 225 will make life easier for fitment and IMO slightly better for the street (minor things like 245s with poke kicking up a bunch of rocks all over the side of your car). Save points and money is my recommendation.

- Andrew

Then there's always the cascading effect of smaller wheels and tires too, of reduced weight requiring less tire, brake, etc. Chapman was smart.

[14stu]

You do not want to daily drive on RE71's, daily your OEM wheels and tires and swap on the good wheels and tires for the track.

The deciding factor should be the Time Trials rule set you are working with. On tracks with lower average speeds and relatively short straights, wider tires are great; however, for tracks with longer straights and higher average speeds, you won't see nearly the benefit and could be slower on the wider tires.

I love my 17x9 6UL's with 255/40-17 RE71r's, but I picked the size mostly for autox and the SCCA Club Trials I run use autox classes. If I were running NASA, I would go with narrower tires to save points.

A fast, aggressive driver can really do a number on a set of RE71r's over the course of a couple of sessions, so life-cycle costs could be high depending on your application.

[ZDan]

Originally Posted by venturaII

Then there's always the cascading effect of smaller wheels and tires too, of reduced weight requiring less tire, brake, etc. Chapman was smart.

17x9 6ULs (17.4 lb.) only weigh 1.3 lb. more than 17x8 (16.1 lb.), and 245/40-17 RE71Rs weigh the same as 225/45-17 (23 lb.). Total weight difference is less than 2 tenths of a percent of vehicle mass, negligible. In terms of unsprung mass, the difference is still only ~2%. Rotational mass difference is 3%, but since the tires contribute more to that than wheels and the tires weigh the same, the difference in rotational inertia is probably more like 1.5%.

[ZDan]

Originally Posted by 14stu

You do not want to daily drive on RE71's, daily your OEM wheels and tires and swap on the good wheels and tires for the track.

I sold the OEM tires, winter tires (Pirelli SottoZero III) are on the factory wheels. I could daily on them in the warmer months, though, they are surprisingly sportsy and grippy!

The deciding factor should be the Time Trials rule set you are working with.

Yeah, it is a factor that camber bolts are zero points, but camber plates = 2 points...

On tracks with lower average speeds and relatively short straights, wider tires are great; however, for tracks with longer straights and higher average speeds, you won't see nearly the benefit and could be slower on the wider tires.

I don't know, I think any additional aero drag due to wider tires (very small increase in frontal area) would be offset by ride height being slightly lower on 245/40s vs. 225/45s. Rotational mass difference is very small, and as a proportion of effective overall vehicle mass, negligible. I don't agree with the idea that wider tires have greater rolling resistance, in fact they should have *less* hysteresis, but IMO the difference in rolling resistance is going to be negligible...

I love my 17x9 6UL's with 255/40-17 RE71r's, but I picked the size mostly for autox and the SCCA Club Trials I run use autox classes. If I were running NASA, I would go with narrower tires to save points.

255/40s are a big thing with S2ks, but I've always wondered if they are really faster vs. lighter-weight 245s with shorter sidewalls and "better" gearing...

A fast, aggressive driver can really do a number on a set of RE71r's over the course of a couple of sessions, so life-cycle costs could be high depending on your application.

Rear RE71Rs lasted one track day on the RX-7 Nearly 3x the horsepower of the BRZ though...

[Jamestl]

Originally Posted by ZDan

I sold the OEM tires, winter tires (Pirelli SottoZero III) are on the factory wheels. I could daily on them in the warmer months, though, they are surprisingly sportsy and grippy!

Yeah, it is a factor that camber bolts are zero points, but camber plates = 2 points...

I don't know, I think any additional aero drag due to wider tires (very small increase in frontal area) would be offset by ride height being slightly lower on 245/40s vs. 225/45s. Rotational mass difference is very small, and as a proportion of effective overall vehicle mass, negligible. I don't agree with the idea that wider tires have greater rolling resistance, in fact they should have *less* hysteresis, but IMO the difference in rolling resistance is going to be negligible...

255/40s are a big thing with S2ks, but I've always wondered if they are really faster vs. lighter-weight 245s with shorter sidewalls and "better" gearing...


Rear RE71Rs lasted one track day on the RX-7 Nearly 3x the horsepower of the BRZ though...

You could try two sets of camber bolts up front (on top and bottom). Not sure from a points perspective, but it allowed me to go from 1.2/1.4 camber (with camber bolts + lower bolt up top) to 2.5. Others have had good success with the camber bolt + top bolt combo, but my experience and also a few people around the area did not yield the same results, and the two sets of camber bolts allowed them to get more. Given the cost of another set of camber bolts relative to an alignment it seems like a no brainer. Good luck!

[ZDan]

Originally Posted by Jamestl

You could try two sets of camber bolts up front (on top and bottom). Not sure from a points perspective, but it allowed me to go from 1.2/1.4 camber (with camber bolts + lower bolt up top) to 2.5. Others have had good success with the camber bolt + top bolt combo, but my experience and also a few people around the area did not yield the same results, and the two sets of camber bolts allowed them to get more. Given the cost of another set of camber bolts relative to an alignment it seems like a no brainer. Good luck!

Thanks, if I go camber bolt route that's what I'll do (2 sets). -1.3 to -2.5 is huge...

[Jamestl]

Originally Posted by ZDan

Thanks, if I go camber bolt route that's what I'll do (2 sets). -1.3 to -2.5 is huge...

It sure is. When I heard about it from someone with a twin at the track, I was like duh... why didn't I think of that! $150 alignment down the drain... on well!

[CSG Mike]

Originally Posted by ZDan

I'm about to start getting my car ready for track work. Plan is to get 1" lowering springs (probably Swift Sports), camber bolts, maybe front sway bar, and wheels/tires. Keeping the stock PP Sachs dampers to save on $$$ and points for my class.

For tires, I'm thinking RE71Rs, either 225/45-17 on 17x8 , or 245/40-17 on 17x9. *Maybe* NT01s in either 225/45 or 235/40-17...

I'm not planning to run camber plates, so gonna be limited on front camber, hoping to get at least -2, maybe as much as -2.5 with SPC bolts in lower hole and factory lower bolt in upper.

I gather that the 245/17x9 route would require an offset in the +35 to +38 range to allow max camber adjustment. Seems like it'd be an awful lot of poke, with outside wheel lip at +32mm out vs. stock :O

225/17x8 should allow max camber with just about any offset wheels, no worries.

Just pondering whether I'm going to go the easier and cheaper way, or tough it out and go big. But I don't know if 245 vs 225 is really going to be a big advantage on this car at stock power...

I do believe we discussed some potential builds for the rules for your series