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Discussion Starter #1
Hey Everyone,

Just picked up my Bolt on Monday and I already have the mod bug. I have been modifying cars all my life and road racing them (willow springs, cal speedway, etc.). This car is a lease so I am thinking cost effective improvements that can improve aero thereby improving range and handling.

I am thinking of buying a set of lowering springs as soon as they become available, and then fabricating some aluminum panels to continue the flat bottom of the battery pack all the way to the rear bumper.

Shouldn't be too expensive, springs are usually 200-300 and aluminum paneling will be around the same or less, plus my time to fabricate mounting points that are removable without any permanent modifications to the car itself by using existing bolt locations, etc. on the car.

Looking for any input or suggestions, maybe some engineers on the boards would like to chip in.

I understand some owners will feel this is stupid, or a bad idea - I thank you in advance for your opinion but would like to keep this thread on topic with people who might be interested in the same thing in case someone searches this topic in the future, please PM me if you still want to share those opinions.

Thanks!
 
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I'm with you on the lowering springs - the OEM suspension sits the rear way too far up in the air, IMHO.
I'm not planning for five passengers with luggage.
 

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I like the ideas and always have the same mod bugs. Both my other 2 cars (Audis) are lowered with aluminum under plates. I discussed springs with a custom spring maker last Fall and they were interested, just needed the stock spring numbers.

Would much prefer the car lowered a bit, for aero as well as handling.

Caveats: Sharp crested driveway at work, no problem with stock suspension....until there is snow on it. (An issue for me, not for some I realize). I like the firmness of the stock suspension, fairly euro feeling. Not sure that feel would improve with shorter, stiffer springs vs. everyday ride quality in a people hauler/commuter. Would love to reduce the wheel gap if I could protect the battery better....hmm...maybe a better shield would help, as long as it allowed for proper cooling of the battery pack.
 

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Discussion Starter #5
I like the ideas and always have the same mod bugs. Both my other 2 cars (Audis) are lowered with aluminum under plates. I discussed springs with a custom spring maker last Fall and they were interested, just needed the stock spring numbers.

Would much prefer the car lowered a bit, for aero as well as handling.

Caveats: Sharp crested driveway at work, no problem with stock suspension....until there is snow on it. (An issue for me, not for some I realize). I like the firmness of the stock suspension, fairly euro feeling. Not sure that feel would improve with shorter, stiffer springs vs. everyday ride quality in a people hauler/commuter. Would love to reduce the wheel gap if I could protect the battery better....hmm...maybe a better shield would help, as long as it allowed for proper cooling of the battery pack.
I emailed Eibach to see if they want to use my car as a test car to develop a set of springs, they aren't too far from me hopefully they do it.

I haven't put the car on a lift yet but I am thinking Aluminum plates front and rear to close any gaps for turbulence and some diffusers on the rear plate, Ill paint it all flat back so it doesn't draw attention.

I am hoping the battery is pretty flat and I don't need to run aluminum plating along the entire bottom of the car, although it would protect the battery a bit against the elements but nothing major of course.
 

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Take pics of your work and post them!
Will do but might be a while, Ill post pics and prices when I get to it incase anyone wants to try the same.

Now if only I had access to a wind tunnel :) will have to use cruise control and Kw meter for tests, same road, same temp, same wind. Hopefully I can replicate those conditions, going to be hard to measure a gain. The drag coefficient on this car is pretty bad so should be plenty of room for improvement, mainly from the rear I will probably start their first, test, then the front.
 

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Now if only I had access to a wind tunnel :)
That's the thing. GM does have a wind tunnel and I'm pretty sure that if closing off the underside of the car made a significant difference on economy and therefore range, they would have done it. They would have used plastic instead of aluminum, but they would have done it. Likely there is just a tiny, if any benefit.

Lowering the car will certainly help handling and maybe aerodynamics. It might be awhile before you get a spring manufacturer interested though. They like to see numbers of cars sold, so potential customers before they commit. Maybe there are a similar springs from another car that they can do right away?
 

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You can do a quick reasonably priced lowering of the Bolt with a set of 16" wheels and tires, and with low profile tires you can easily get about 1" of lowering, with plenty of stock suspension travel.
 

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You could just do that... but I doubt you'll get any nicer handling and cool affect off of it haha. I don't know if it'll be as effective either.
 

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The 225/40/18s I'm looking at should lower by about .4" vs. the stock tire size. Yes, I know, not super aggressive, but this is a family hauling ev. Ok for the Summer, but realizing I'll need the lil' extra clearance in winter for the snow on our driveway crest. Lowering cars by tire size isn't my usual modus operandi, but works in this case. I've already looked at lowering springs but that wouldn't help me for winter, tire profile will.
 

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The 225/40/18s I'm looking at should lower by about .4" vs. the stock tire size. Yes, I know, not super aggressive, but this is a family hauling ev. Ok for the Summer, but realizing I'll need the lil' extra clearance in winter for the snow on our driveway crest. Lowering cars by tire size isn't my usual modus operandi, but works in this case. I've already looked at lowering springs but that wouldn't help me for winter, tire profile will.
Doesn't that throw off your speedometer and odometer? I think it might also effect your range estimates. Is there a way to easily recalibrate to a smaller size wheel?
 

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That's the thing. GM does have a wind tunnel and I'm pretty sure that if closing off the underside of the car made a significant difference on economy and therefore range, they would have done it. They would have used plastic instead of aluminum, but they would have done it. Likely there is just a tiny, if any benefit.

Lowering the car will certainly help handling and maybe aerodynamics. It might be awhile before you get a spring manufacturer interested though. They like to see numbers of cars sold, so potential customers before they commit. Maybe there are a similar springs from another car that they can do right away?
Not to mention the aerodynamic design modeling software...
 

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You title is "Improving the Drag". But is that what you really wany? It should be "Reducing the Drag, right?

Anyway, I never drive above 60 MPH, and the Bolt EV has been designed to reduce the drag effect at higher speeds already, so I doubt you can gain any range over what the GM engineers did, or do it cheaply without affecting other designed features, such as suspension height play and low speed range. Lowering the car may help reduce drag but that will drastically degrade city driving where there are mnay street imperfactions and "pot holes". Here we call them "street craters" when they exceed a foot in diameter because a small car wheel falls inside the hole while a larger diameter wheel can roll over it. Having less suspension clearance will cause the Bolt EV body and frame hitting the limits of travel and transmit the shock directly to the entire car and the driver/passengers. And loweing the ride height will take away one feature that makes the Bolt EV more attractive than over EVs, including the Volt, for easier senior passenger entry and exit.

The only slight improvement could be an adjustable system, as in the high end Cadillacs and TM Model S, where you (or the car itself) can adjust the ride height according to the planned drive and road speeds. But that makes the driving more complex and even increase the weight, offsetting any gains from a reduced drag. Volt owners do complain about the lower air deflector being too low and scaping even when entering a garage, so if you lower the Bolt EV ride height, you will have that new problem.

My final conclusion? Drive the Bolt EV carefully as it was designed and built, and forget about modifying its ride height. The investments in money and time to change that ride height will never return in range, and you risk damaging the ride and harming the car and the humans aboard.
 

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IMHO, the Bolt could stand to have the aft end lowered a bit - not a lot, maybe 1/2-3/4". Springs would be the right way to do it, and a moderate change shouldn't affect the ride much.
Overall, I'm quite pleased with the handling/comfort balance of the Bolt as delivered. I'll be keeping an eye on aftermarket tweaks as they become available, but the stock suspension is pretty darn good as it is.
Even the stock tires are better than I expected in local 50's rainy weather. I've got summer tires on the way, but the OEM aren't awful.
 

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Doesn't that throw off your speedometer and odometer? I think it might also effect your range estimates. Is there a way to easily recalibrate to a smaller size wheel?
I like this one: https://tiresize.com/calculator/

I've researched the different sizes that will fit, and there's a lot out there to read about camber, unsprung weight, scrub radius, etc.

There are precious few wheel options (that aren't completely cu$$tom) that are currently available (that look half way decent, imho). Very difficult to find 18s that aren't hideous and/or heavy, particularly in a 6.5" or 7" width. Hyundai makes some stock wheels that are decent, albeit heavy, in 18 x 6.5, but then you'll need an adapter, which will push the wheel out anyway. So I'm going to test fit an 18x8 and see what I think. Not looking for a ghetto look at all!

Stock wheels with 225/50/17s are also in consideration, but I'd love to keep the winter tire set on the stockers and get 18s for Summer. "All season" / no season tires are not an option for my driving. All in preparation for my 2020 Bolt SS AWD, of course!
; )
 

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You title is "Improving the Drag". But is that what you really wany? It should be "Reducing the Drag, right?

"loweing the ride height will take away one feature that makes the Bolt EV more attractive than over EVs, including the Volt, for easier senior passenger entry and exit."
The Bolt isn't made for hauling seniors, lol. The suspension is way too stiff for them, and the shape of the rear doors with the decreasing roof line makes it far from ideal for our respected elders / blue hairs. Also, the seats are set too far inward to easily turn and pop a squat for senior entry.

I know what you're saying though, with the higher ride height I feel like I'm in an suv compared to our other cars. At least the suspension is nice and firm. I'd just like to be a little lower, especially in Summer, and I'm not putting adjustable coilovers on this car.
 

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When considering lowering the car just remember there is a very expensive battery pack sitting there. Scraping the bottom on anything could cause a major and expensive F-up.
 

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The Bolt isn't made for hauling seniors, lol.
Pardon? It's pretty good for me and the better half, and we're both well past 55.
High seating is a big help. OK, the suspension is a bit stiff if you're in the Buick generation, but I'm quite happy with the ride.

Got to agree with [email protected] though - lower too far and damage the battery and you will not be a happy camper. :crying:
 
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