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looking at everything online, and for my Volvo based build I will need at least a 17" wheel to clear the brakes I'm planning on using. For the tire width I'm thinking of running, I will need to run either a 17 or an 18" wheel. For a good combo with tires and wheels I'm thinking of 18x10 for the rear with a 305-35-18 and a 18x8 and a 265-35-18 on the front. Is this going to look weird and out of place? Running a 5x108 bolt pattern leaves me to either newer ford wheels, Volvo wheels, and wheels for a Ferrari. Here is a pic of the wheels I have picked out atm.

Apparently 20" is the new norm that most sticky rubbers come in. (JD get your mind out of the gutter!!!)

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mobilito ergo sum
I drive therefore I am

I can explain it to you,
but I can't understand it for you.

yea, 20" of sticky rubber is way to much for me. It would look out of place on such a little frame. I just don't want to make it look weird. the chassis will be a 442

I didn't say I liked it or that you should do it, it's just thats all you seem to see nowadays. I remember not so long ago - 4-5 years, 20" were laughed at as being too big and suddenly that's all the manufacturers do on their performance models.

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mobilito ergo sum
I drive therefore I am

I can explain it to you,
but I can't understand it for you.

"what size wheel is too big?" Anything larger than needed to clear the brakes. After that you are going for cosmetics only and need to decide if you like the looks enough to suffer the penalties.
That being said, in the widths you are after 18" may give you better options/pricing on tires.

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Build log: viewtopic.php?t=9291

I think you're thinking way too big. They'll just slow you down. Can you even warm up a tire that big? Remember these are probably made for much heavier cars.

How much does the big disk rotor, wheel and tire weigh compare to a setup on a 15" wheel? All that unsprung weight on a light car will really harshen up your ride. I know for my car it's almost %50 more weight for the 11" rotos over the 10" rotors, so I'm going 10". A 14 lb. rotor sounds good to me.

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Marcus Barrow - Car9 an open design community supported sports car for home builders!
SketchUp collection for LocostUSA: "Dream it, Build it, Drive it!"
Car9 Roadster information - models, drawings, resources etc.

Personally I think a Locost even with 17's will look goofy, but it isn't my car you're building. I'd shrink the brakes and run 15's if it were me. I've got 13's on my car, and my thinking at the time was that I could run Toyo R888's for autocross and Sumitomo was making summer performance tires in some 13" sizes back then, but not anymore. Turns out the R888's make good street tires on a car this light anyway, and don't really warm up enough for autocross.
Kristian

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I'll ask: What is the intent for the car? Street cruising? Mountain curves? Track? Autocross?

You may be surprised at how little rubber you need on >2000lb car. I've 205/50r15 NT01 on my 1700lb car with 280ft/lbs and have lots of tire grip. I can't see needing more than 225 on mine. You may be able to just opt for better performing parts (IE street/track brake pads and Rcomp tires) rather than using larger street rotors/pads and tires. Likely be cheaper too. Unsprung mass and rotational mass is something to be aware of on a light car too whether you're going for performance or comfort.

Cheers.

Cory

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Build log: viewtopic.php?t=9291

In my personal opinion, extremely wide tires that at best came stock on but a small handful of extremely uncommon cars, is a great way to ensure that the size you need will be largely unavailable within a decade. At the very least, look for something with great current availability...In other words, not 305/35R18

For something I'm pouring my heart and soul into, and may likely want to keep/drive for many years to come, one of my goals is trying to reasonably future-proof my selections. So I want to start with an outer diameter and width that is widely used in the tire industry and common to multiple wheel diameters. For example, a ~25" OD and 225mm width currently has good to great availability for 50R16, 45R17, and 40R18 sizes. Then I'll base the fitment around a wheel offset that is common in the widths and diameters under consideration. This way, even if one size starts drying up, it's just a known simple wheel/tire swap away from being good to go again, rather than having to re-engineer half the suspension for a completely different outer diameter and/or width.

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-Justin

"Orville Wright did not have a pilots license." - Gordon MacKenzie

[quote="loki98t5"]looking at everything online, and for my Volvo based build I will need at least a 17" wheel to clear the brakes I'm ...

Was the question about «look» or was it about effectiveness or functionality.
The look is a matter of personal preference. There is no absolute rule. You may want to look like the traditional Lotus seven and check the original wheel size. If you want to look modern then get yourself thin rubber on tall rims.
Functionality is another matter. IMO tall wheels give the smoothest ride, however you have to think of the differential gear ratio as this will affect (on paper) acceleration.

Loki, I didn't mean for my post above to sound harsh, but it probably did. I was in a rush on the way out the door.

Everyone here will support you with help how ever you decide to go. We're trying to get you to adjust your thinking to the size of the car you are building though. Unless you plan on seriously competing on road racing courses that are specifically very hard on brakes ( which would be unusually short and twisty courses, just a few in the country ), unusually large brakes are not needed. If you are willing to go to the effort of buying the stuff you mention you can also choose to build to a reasonably light car. That means it would be well under 1500 lbs., less than half the weight of almost anything you could buy these days.

Since the frame rail in the cockpit is unlikely to even reach the height of your knee, a set of 15" rims will have a nicely tall and modern look on your car. At least I would think so. I'm sure the original had 13" tires...

Also I was genuinely interested in the weight of the parts you are looking at because I am going thru that now on my build. Possibly steel rims at 15-20 lbs. and hub/rotors at a little under 15 lbs.

All this unsprung weight in tires, wheels and rotors, going 0-60 MPH, has to accelerated to 60 MPH, but also spun up to speed. So it all costs twice and can count for 25% or more of the power used on the 0-60 run. It does make a real difference. Plus these parts are more desirable these days so they charge more than they actually cost compared to 15" stuff.

A 225 tire on your car, considering the weight on the rubber will be something like a 650-750 size on a modern sporty coupe these days!

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Marcus Barrow - Car9 an open design community supported sports car for home builders!
SketchUp collection for LocostUSA: "Dream it, Build it, Drive it!"
Car9 Roadster information - models, drawings, resources etc.

Hi Loki. I ended up with 17" wheels for my build, partly because of frustration with finding sufficient tire options for smaller wheels. The 17's also pre-empted problems with choosing brake calipers and rotors. And from a styling standpoint, I always liked the look of the old Watson Indy roadsters with their tall wheels, so the 17" wheels played to that vibe. That said, I think 18" would have been a bit much for me, but I did go with bigs and littles for rubber on the 17" wheels.

Tires and wheels need to be selected before starting serious suspension design so you are asking the right questions. Tire o.d. and wheel offset are the key parameters, followed by hub and spindle dimensions.

It's your build, so any size you choose will be right. Keep us posted with lots of pictures.

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Cheers, Tom

My Car9 build: viewtopic.php?f=35&t=14613
"It's the construction of the car-the sheer lunacy and joy of making diverse parts come together and work as one-that counts."
Ultima Spyder, Northstar 4.0, Porsche G50/52

SeattleTom is giving good advice. I think I am stuck in the 80's, in fact that reminds me, I'm pretty sure I need a haircut.

I just don't account for limited choices in tires for 15". Wheels bigger than you need is not the right place to be, but they just don't make the street tires because of modern fashion I suppose. It looks like good competition rubber is still available in 15", but choices for everyday stuff seems limited. I'm still looking....

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Marcus Barrow - Car9 an open design community supported sports car for home builders!
SketchUp collection for LocostUSA: "Dream it, Build it, Drive it!"
Car9 Roadster information - models, drawings, resources etc.

Between 195/50R15, 195/55R15, and 205/50R15 (and 225/45R15 for a more competition focus) there is 'adequate' availability of suitable tires for 15" wheels, but the big question mark is for how much longer? It could be that they start drying up quickly within the next few years, or they could soldier on similarly for another decade or more. A lot of it probably depends on how strong the 90's Civic/Miata performance enthusiast market stays.

I too generally like the idea/look of 15" wheels with 195-205mm ~23" OD tires for these cars too. However, for cars still being (or yet to be) built, I personally believe that it would at the very least be prudent to hedge your bets and run all the numbers to make sure switching to 225mm 25" OD tires at a later date would not result in any unintended complications.

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-Justin

"Orville Wright did not have a pilots license." - Gordon MacKenzie

Approach the problem from the opposite direction. Go to Tire Rack or equiv, bring up the super high performance street rubber and see what sizes they carry - end of story. It's an academic argument if what's "right" can't be had; pick something that exists and move on.

I future-proofed Midlana design by designing around tire diameter, so what builders use for wheel size doesn't matter. I had the advantage of starting from a clean sheet, where tire selection is the first design decision. You guys building per plans that assume a really small tire diameter, yeah, that's going to be a problem. Go by tire OD and work backwards.

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