Best offset for 17x9 for AutoX/track?

[timurrrr]

Hey folks,

So I've been researching various 17x9 wheels lately and was wondering what is the "best" offset for things like AutoX and track days.

There was a related question in the past:

Originally Posted by jvincent

do you guys run the same offset as stock or slightly less, i.e. not enough to be flush but a little less than stock to get a just a little bit wider stance?

which CSG Mike answered:

Originally Posted by CSG Mike

Slightly less, but because we need to clear the suspension.

Based on that response, I'm under the impression that the smaller the offset (less poke / more tuck) the better.

APEX Race Parts say that the sweet spot is around ET40–42:

Originally Posted by APEX Race Parts

9" wide wheels are the maximum wheel width we can stuff under the car with the stock suspension in place, and we believe the sweet spot for offset is ET40-42.

However, for some reason various 17x9 +35 wheels are very popular (RPF1s, TC105N, TC105X) among FT86 enthusiasts.

Titan 7 Wheels claim they purpose-build their wheels to specific cars, and for FT86 their T-S5 17x9 offering is +37.

I'm a little confused here, to be honest.
Some of the other concerns I've seen are:

• Around +42 is the highest you can go with stock suspension
• +40 and higher offsets are more likely to rub the inner fender
• At lower offsets (around +35) you need significant negative camber to avoid excessive poke / rubbing the wheel arch / popping the side marker
• The higher the offset, the less room for adjustment you have with camber bolts, having zero room around +42, and some even reported issues with +40 wheels.
  I know some folks max out their camber at the camber plates and end up also using camber bolts.
• Stock offset is +48, so the lower the offset you get, the more you change the scrub radius from the intended value — at what point does this start to matter? Does camber also affect the effective scrub radius?

In case it matters, I have CSG Spec TEIN Flex A pending install, so I might have a bit more room for the wheel if offsets even higher than +42 are beneficial. Also, I plan to run GT Radial SX2 245/40R17 for at least some time after I get 17x9s.

[Cole]

I'm running +35 (+32 effective with a 3mm spacer), with about -3* of camber with stock struts and tein lowering springs.



Realistically, if you're asking this question, you're not actually good enough for it to matter. Since you have coilovers pending install, your wheel choice comes down to whatever you think is prettiest at the price you want to pay.

[Breadman]

i have 6ULs with csg flex As. there is plenty of room to spare with my brembos, the coilover, and wheel well

[rt]

+38 with 255/40 tires and -3.1* camber didn't rub for me on the track.

[finch1750]

I rubbed a bit when really low with +42 and -2.7 camber. Id go +35 if possible. I just raised it a bit and put on 3mm spacers and have been good since.

If tracking/auotx you need camber anyway so inner clearance is the bigger need, hence the lower offsets

[KevBRZ]

FWIW, I just installed +35 offset 17 x 9 wheels with 245/40/17 tires, they will poke some and the bad thing is you really can't dial in much negative camber up front at all or tire will hit the stock spring perch in the front, i don't know exactly how much negative camber i have but probably less than -1 and i only have a few mm maybe 3 from the perch just enough to barely slip a piece of cardboard in the space but snugly . i kinda wondered if my tires were oversized a bit (rivals)
i plan on going with coilovers shortly anyhow but just in case you were interested.
I am not sure how Cole above is running that setup unless he has more narrow wheels and tires.

[Cole]

Originally Posted by KevBRZ

FWIW, I just installed +35 offset 17 x 9 wheels with 245/40/17 tires, they will poke some and the bad thing is you really can't dial in much negative camber up front at all or tire will hit the stock spring perch in the front, i don't know exactly how much negative camber i have but probably less than -1 and i only have a few mm maybe 3 from the perch just enough to barely slip a piece of cardboard in the space but snugly .
i plan on going with coilovers shortly anyhow but just in case you were interested.
I am not sure how Cole above is running that setup unless he has more narrow wheels and tires.

“More narrow wheels and tires”? What does that even mean?

My set up is as follows:
RE71R 245/40/17
720Form GTF1 17x9
3mm spacer
Tein S Tech springs
Camber bolt in the top hole, set to max negative camber
Silver Project top hats, also maxed for negative camber

[KevBRZ]

Originally Posted by Cole

“More narrow wheels and tires”? What does that even mean?

My set up is as follows:
RE71R 245/40/17
720Form GTF1 17x9
3mm spacer
Tein S Tech springs
Camber bolt in the top hole, set to max negative camber
Silver Project top hats, also maxed for negative camber

My bad , I was thinking maybe you had 17 x8 wheels and maybe 235 series tires, i only got a camber bolt in the bottom hole and if its maxed out i am literally hitting the perch. Weird. i had to back out the camber to clear the perch.

[CSG Mike]

It all depends on how you get the camber, and your specific tire.

There is no one size fits all, if you want to push the limit.

+37 is the size chosen for CSG spec TWS T66-F and Titan7, because that is the highest that will clear any reasonable variant of tire and camber modifier on stock suspension.

[timurrrr]

Thanks everyone for the data!

Originally Posted by CSG Mike

It all depends on how you get the camber, and your specific tire.

Can you please elaborate, assuming e.g. 245/40 GT Radial SX2, camber bolts and camber plates?

Originally Posted by CSG Mike

+37 is the size chosen for CSG spec TWS T66-F and Titan7, because that is the highest that will clear any reasonable variant of tire and camber modifier on stock suspension.

Would you pick a different offset for non-stock suspension, e.g. CSG Spec TEIN Flex A?

Originally Posted by CSG Mike

There is no one size fits all, if you want to push the limit.

Sure, just want to better understand the trade-offs and known good recipes before making a $1k+ purchase.

Originally Posted by Cole

Realistically, if you're asking this question, you're not actually good enough for it to matter.

Not unlikely, but the whole purpose of me buying and modding the car is to learn more and get better. Don't want to learn by making expensive mistakes that are easy to avoid by doing a bit of homework, and I'm sure someone else will later benefit from the knowledge we exchange here.

Originally Posted by KevBRZ

FWIW, I just installed +35 offset 17 x 9 wheels with 245/40/17 tires, they will poke some and the bad thing is you really can't dial in much negative camber up front at all or tire will hit the stock spring perch in the front, i don't know exactly how much negative camber i have but probably less than -1 and i only have a few mm maybe 3 from the perch just enough to barely slip a piece of cardboard in the space but snugly . i kinda wondered if my tires were oversized a bit (rivals)
i plan on going with coilovers shortly anyhow but just in case you were interested.
I am not sure how Cole above is running that setup unless he has more narrow wheels and tires.

You'll probably want camber plates, see:

Originally Posted by APEX Race Parts

For performance driving enthusiasts looking to increase handling performance while gaining more outer fender clearance (in order to stuff wider compounds onto the wheel), adjustable camber plates are the real solution. Camber/crash bolts are a band-aid fix and can only net you so much camber.

[ka-t_240]

I have 17x9 +42 and 35.

The +42 will rub on the inner fender/front on the front. I have had 3 different sets of 245 or 255 on it and have slight rub. The +35 have never rubbed anywhere.

[timurrrr]

Originally Posted by timurrrr

...

• The higher offset, the less room for adjustment you have with camber bolts, having zero room around +42.
  I know some folks max out their camber at the camber plates and end up also using camber bolts.
• Stock offset is +48, so the lower the offset you get, the more you change the scrub radius from the intended value — at what point does this start to matter? Does camber also affect the effective scrub radius?

Found some interesting old discussion on this topic and specifically this post that says that generally one should get most of the camber from the hub, not the top mounts.

[timurrrr]

Originally Posted by Breadman

i have 6ULs with csg flex As. there is plenty of room to spare with my brembos, the coilover, and wheel well

Which offset, +40?

[KevBRZ]

You'll probably want camber plates, see:[/QUOTE]
Actually with 2 camber bolts on each side or 1 camber and 1 crash bolt you can get alot of negative camber , i am going to use coilovers that will have camber plates but i am going to try to get as much negative camber i can from the lower holes not the plates, they are slotted on the coilover so with just a crash bolt i might be pretty good and i don't think you are supposed to use camber bolts on coilovers due to slippage but i am by far not an expert on these matters lol