Looking for advice on wheels and tires

[Ob1Jacobi]

I’m new to the sport so my original plan was to finish destroying my current tires (slippery energy savers) while I’m flailing around learning this year, but they’re not going to make it to the end of the year. Since I’m buying new tires anyway it seems like it would be ideal to go ahead and get an extra set for events so both the DD and autocross sets will last longer.

The Bolt EV OEM’s are 17x6.5 and weigh 23lbs. There are a few options off the Cruze, including 16x6.5 steelies weighing 18lbs and 16x6.5 alloys weighing 20 lbs. Reducing 3lbs per corner seems significant from what I’ve been seeing online, 5lbs even moreso. I’m not sure I’m experienced enough to notice, but I’ll gladly take all the help I can get.

My question is: would my OEM 17s be better for autocross with the larger contact patch, or one of the Cruze 16” options for the lighter weight, cheaper tires, and more torque (assuming smaller overall tire diameter)? Or should I burn a set of all seasons on my current 17s before getting a separate set of wheels? Or do I get some 16s and run all seasons on those before swapping sets?

After I figure out the wheel dilemma I’m going to start researching optimum tire sizes, so any advice there would be helpful too.

[nickrd10bk]

Keep in mind, the wheel weight is unsprung weight. While that is still weight bolted to the car, it's not going to be weight that is rolling back and fourth when turning.

I would opt for the larger contact patch, as power doesn't matter as much as speed. You typically get up to speed once and try to keep the highest average speed.

Another observation of your car is the rate at which the electric motor can make torque will often spin the tire(s). A smaller diameter tire is going to be easier to spin, and less likely to put power down with its reduced longitudinal grip.

[Ob1Jacobi]

Keep in mind, the wheel weight is unsprung weight. While that is still weight bolted to the car, it's not going to be weight that is rolling back and fourth when turning.

I've been under the impression that unsprung weight is worse than sprung weight because of the inertia. There's not much I can do to reduce the sprung weight, those batteries add up.

I would opt for the larger contact patch, as power doesn't matter as much as speed. You typically get up to speed once and try to keep the highest average speed.

Another observation of your car is the rate at which the electric motor can make torque will often spin the tire(s). A smaller diameter tire is going to be easier to spin, and less likely to put power down with its reduced longitudinal grip.

I would have thought that my cars biggest advantage would be the instant torque, rather than having to build up the curve. I guess I was picturing making a small tire spin as fast as possible and hoping the stickier tires wouldn't break loose to regain speed quicker exiting turns, rather than trying to hold a higher speed through turns because of how heavy it is. Maybe I'm thinking about it all wrong though.

[nickrd10bk]

I've been under the impression that unsprung weight is worse than sprung weight because of the inertia. There's not much I can do to reduce the sprung weight, those batteries add up.



I would have thought that my cars biggest advantage would be the instant torque, rather than having to build up the curve. I guess I was picturing making a small tire spin as fast as possible and hoping the stickier tires wouldn't break loose to regain speed quicker exiting turns, rather than trying to hold a higher speed through turns because of how heavy it is. Maybe I'm thinking about it all wrong though.

In an Autocross, whoever has the highest average speed is heavily favored to win. You will notice most courses have only a few power opportunities, and the rest is either a slalom or sweeper turns.

You want to carry the momentum thru the turns.

Also the torque is good enough I'd be inclined to say you wouldn't have much penalty to running the larger tires with larger contact patch. It won't affect the gearing for sure.

We may be looking at the wrong information though. We should consider what the good Autocross tires are, and what sizes they come in. You may be limited in options enough to consider a specific tire anyway

[Ob1Jacobi]

In an Autocross, whoever has the highest average speed is heavily favored to win. You will notice most courses have only a few power opportunities, and the rest is either a slalom or sweeper turns.

You want to carry the momentum thru the turns.

This makes sense, and I can picture it easier for lighter cars, but wouldn't a heavier car be forced to slow down more through a turn? Otherwise I feel like the weight and momentum would make it more prone to understeer.

We may be looking at the wrong information though. We should consider what the good Autocross tires are, and what sizes they come in. You may be limited in options enough to consider a specific tire anyway

So you're saying pick the tire first and then the wheel to match? The RE71-RS has seven options for 16 and 17s and fifteen options for 18s. Obviously I could eliminate whatever is too big to clear the fenders, to wide to fit on 6.5" width, and I could probably just pick the lowest speed rating where that's the only difference between sizes. Outside of that, where do I even start?

[Ob1Jacobi]

We should consider what the good Autocross tires are, and what sizes they come in. You may be limited in options enough to consider a specific tire anyway

This was good advice.

All of the 18" wheels I’ve seen are at least 7” wide, so I’m going to rule those out for now.

It looks like the 205/45R17 is the only 17” size in the RE71RS that will fit on a 6.5” rim and actually has a smaller contact patch than most of the 16” options. I think the 225/50R16 is going to give me the largest contact patch and conveniently enough it’s also the cheapest of the 16” options on tirerack.

[nickrd10bk]

This was good advice.

All of the 18" wheels I’ve seen are at least 7” wide, so I’m going to rule those out for now.

It looks like the 205/45R17 is the only 17” size in the RE71RS that will fit on a 6.5” rim and actually has a smaller contact patch than most of the 16” options. I think the 225/50R16 is going to give me the largest contact patch and conveniently enough it’s also the cheapest of the 16” options on tirerack.

I just looked up both of those tires and I think the 225 50 16 is the better option.

Those tires will be easier to fit on the 6.5" wheel, and they are significantly cheaper per tire. The diameter is comparable to the 205 45 17 size they have listed also.

That also allows you to mount them on a set of steelies from the Cruze and that not only makes the setup lighter, but more cost effective.

I think you're on the right track.

[rodhx]

I’m new to the sport so my original plan was to finish destroying my current tires (slippery energy savers) while I’m flailing around learning this year, but they’re not going to make it to the end of the year. Since I’m buying new tires anyway it seems like it would be ideal to go ahead and get an extra set for events so both the DD and autocross sets will last longer.

The Bolt EV OEM’s are 17x6.5 and weigh 23lbs. There are a few options off the Cruze, including 16x6.5 steelies weighing 18lbs and 16x6.5 alloys weighing 20 lbs. Reducing 3lbs per corner seems significant from what I’ve been seeing online, 5lbs even moreso. I’m not sure I’m experienced enough to notice, but I’ll gladly take all the help I can get.

My question is: would my OEM 17s be better for autocross with the larger contact patch, or one of the Cruze 16” options for the lighter weight, cheaper tires, and more torque (assuming smaller overall tire diameter)? Or should I burn a set of all seasons on my current 17s before getting a separate set of wheels? Or do I get some 16s and run all seasons on those before swapping sets?

After I figure out the wheel dilemma I’m going to start researching optimum tire sizes, so any advice there would be helpful too.

I ran my Bolt several times in 2020 and went with a set of 16" Cruze alloy wheels. The improved gearing from the small wheel/tire diameter has a big gain on acceleration. And you don't really care because single-speed trans! I've still got those wheels you can have CHEAP if you want to take them out of my basement.

[Ob1Jacobi]

I ran my Bolt several times in 2020 and went with a set of 16" Cruze alloy wheels. The improved gearing from the small wheel/tire diameter has a big gain on acceleration. And you don't really care because single-speed trans! I've still got those wheels you can have CHEAP if you want to take them out of my basement.

I found a set of steelies at LKQ but I haven't picked them up yet. Let me know what you're thinking!
What tires did you run? Any other Bolt specific tips you've got would be appreciated!

[rodhx]

I found a set of steelies at LKQ but I haven't picked them up yet. Let me know what you're thinking!
What tires did you run? Any other Bolt specific tips you've got would be appreciated!

I was thinking $100 but open to offers. These are the five spoke Cruze wheels. I ran the RE71R in something like 205/50-16. I think they were a full inch smaller diameter than the stock setup. Definitely improved acceleration. Ultimately the Bolt is hampered by the intrusive stability control (unless someone finally figured out how to defeat it after all these years) and open diff so can’t put power down in turns.

I’m working our race at Barber this weekend and could bring the wheels on Sunday. You can email me at teen.driver@alscca.net.

[Ob1Jacobi]

I was thinking $100 but open to offers. These are the five spoke Cruze wheels. I ran the RE71R in something like 205/50-16. I think they were a full inch smaller diameter than the stock setup. Definitely improved acceleration. Ultimately the Bolt is hampered by the intrusive stability control (unless someone finally figured out how to defeat it after all these years) and open diff so can’t put power down in turns.

I’m working our race at Barber this weekend and could bring the wheels on Sunday. You can email me at teen.driver@alscca.net.

That's very generous of you and I appreciate it. I'd be happy to take them off your hands and just you an email to figure out the logistics. I've been debating replacing my 17s with 16s for economy/range/comfort/cost reasons so I may keep the steelies for racing and use the alloys for daily driving.
The 225/50R16 isn't quite as small of diameter but it is a bit wider than the 205/50. Maybe there will be a little acceleration improvement over stock but hopefully the increased grip will be worth it.

I think the traction control can be turned off but from what I've read the stability control turns itself back on over 30 mph. I've seen conflicting reports of whether it's faster to leave TCS on or off. What's your experience on this?
I also managed to score a rear sway bar for a decent price on the bolt forum. So far I can't tell much difference in daily driving other than an added squeak at low speeds. I'm thinking the lock nuts may need some help from some loctite.