Big Wheels!

No, not the three-wheeled pedal kind. More like this:

I'm planning my Locost build and really like the old Indy car look. I'd love to be able to run big rubber like this around town, then throw on small diameter/wide slicks for the track.

Pros: Cool looks, more visible to traffic, better ground clearance.

Cons: Additional expense, greater unsprung weight, higher cg, need extra set of fenders/stays if I want to be legal, possible tire/body interference.

Really it's the unsprung issue that troubles me the most. I can handle the comprimised performance around town, since I can't go all-out there anyway. But are there wheel tire combinations that don't weigh a ton and/or break the bank?

I'll bet you the weight difference will be negligable......

the weight will not be negligable.. probably around 10 pounds or more per corner.. the problem will be the suspension. To control such squishy and bouncy tyres.. you are going to need super stiff suspension... but then bolt on the small rubber bands for track day use.. and you might as well not have a suspension at all

In reply to mad_machine:

That depends on wheels and tires.....for my car, the factory 16" wheels with 215/60 series tires weigh nearly the same as my 17" oz's with 245/45 star specs....and my shipping scale at work proved the factory 16x6" slicer was 8 ounces heavier than the 17x8 superleggra....

Definitely not negligible. There's a 3lb difference between a 225/45-15 and a 205/50-15 in the Toyo RA1, for example. To pick a potentially more apt comparison, I randomly chose the Goodyear Eagle GT - I used that because it's liable to come in a wide range of high profile sizes.
195/55-15 (closest I could find to a typical 23" Locost setup): 22 lbs
215/60-16 (26.2"): 28 lbs

Finding reasonable tires in large diameters without going super-wide might be a challenge, actually. Unless you go to Coker. All that big squishy sidewall and low traction might make it kind of fun on the street. You can't usually play with a Locost much outside a track, they're just too fast. But not in this case Caterham uses fairly high profile, skinny tires on their road cars.

Also, this is why they invented adjustable suspension. If you're a smart person you could even build a set of rocker arms with different mounting points to alter the ride height and shock ratios without having to do anything other than move a few bolts around.

I'm thinking skinny a la Coker, not fat a la pimpmobile. It just occured to me that flywheel effect will play in here as well. A large diameter wheel resists directional change which on an Indy car at 175 MPH might be desireable. On a Locost OTOH it's pretty well the opposite of what you want....

I think Coker actually reproduces those old Indy car tires, but then you'd need some 18" Halibrands to put them on.

One good thing is that even with a pretty stiff suspension the car should ride smoothly as the tires act as part of the suspension with a lot of give.

kreb wrote: I'm thinking skinny a la Coker, not fat a la pimpmobile. It just occured to me that flywheel effect will play in here as well. A large diameter wheel resists directional change which on an Indy car at 175 MPH might be desireable. On a Locost OTOH it's pretty well the opposite of what you want....

Actually isn't a Locost pretty twitchy in traffic? If you're driving on the freeway (probably the slowest that the flywheel effect would matter) it would help with directional stability.. less darty maybe. If your alignment and balance is good.

Nah, I've never felt mine to be twitchy at all. If it's set up to be well-balanced in an 80 mph sweeper, driving in a straight line at 75 mph is not a bit of a concern.

dculberson wrote:

kreb wrote: Actually isn't a Locost pretty twitchy in traffic? If you're driving on the freeway (probably the slowest that the flywheel effect would matter) it would help with directional stability.. less darty maybe. If your alignment and balance is good.

Twitchiness would probably be the result of not enough caster, bad geometry or alignment. My Stalker was as solid as one could ask for.

One issue that I could see is that I'm using Miata spindles (4 x 100), and Cokers or other large diameter wheels are likely to be 5-lug.

If one were to use tall tires, the tendency towards sidewall flex would be somewhat mitigated by the light weight of the car

I think people were suggesting Coker for tires, not wheels. You can get large diameter wheels in 4x100, that's not really an issue. For example, there's a 16" steel wheel from a Cobalt that will bolt up and look vintage. Or some pretty big Rota RBs.