frenchyd HalfDork
10/13/17 6:36 a.m.

It's spread sheet time.

I'm starting to draw out framing details and I need a source or two for details about wheels and tires.  

Since it's a clean sheet design I can't go to Tire Rack  and enter make and model  and size could be a 15,- 19 while rim width  depends on tire size.   

Its the classic catch 22 I don't know what tires I'll use because I don't know what rims I'll use. 

Sure price plays a part as does weight, profile, and back spacing.  Wide is good but too wide just means I have to drive further in an autocross.  While it's  main purpose will be track time I can't go with a dedicated race tire since my goal will be to Drive, race and drive home. 

Jaynen SuperDork
10/13/17 6:39 a.m.
Pete Gossett
Pete Gossett MegaDork
10/13/17 7:16 a.m.

In reply to frenchyd :

What is the estimated weight? That would help you estimate a range of widths, then you can find a diameter with the best/most/cheapest options.  

Look for a common size that's likely to be in production for some time(i.e. Miata fitment). 

tomtomgt356 Reader
10/13/17 7:26 a.m.

Is this a home built car? What weight? What engine? What use (track, autocross, rallycross, show car)? A 1,500 lb 100 HP car will use a different tire than a 3,000 lb 600 HP car. A street car uses a lot different tire than a track car.

Generally you pick a tire size you want and then pick a wheel that fits that. Find a tire size that is common with a lot of options and it is less likely to be orphaned. Once you pick a tire, you can then find a wheel that works. You will go through a lot of tires before you have to replace wheels. 

frenchyd HalfDork
10/13/17 7:59 a.m.

In reply to tomtomgt356 :Yes, likely my last scratch built. I want to put all the tricks and knowledge I've learned in 55 years of racing  to use.  

What I'm looking for is a giant spread sheet that will tell me, should I go with a 15x10 and 27 inch tall tire but 11 inches or tread or should I go with a 19x8  still a 27 inch tall tire  but less tread. 

Maybe I should rethink diameter or tread width.  Trade a smaller diameter to get a better acceleration!  

Tracks I'd like to use vary from Elkhart Lake with it's long straights and tight corners to a local autocross.


Robbie PowerDork
10/13/17 8:15 a.m.

Since it's a scratch built, you can play with whatever tires you want, and adjust rear gear and trans ratios (even engine rpm powerband) to get your optimal acceleration.

Maybe pick a very common race take off size?

Also, 285/30/18 is a very intriguing size for many cars because it is wide but still short...

frenchyd HalfDork
10/13/17 9:51 a.m.

In reply to Robbie :

That's just it!  I can use whatever tires/ wheels I want!    So should I use a 15x10 and NASCAR take offs?  How about a more modern size like 19x8.5 ?   What are the price weight tread width aspect ratio of the various sizes that will fit? Not only that but what brands?  Is there better choices?  

Ive got a clean sheet Where do I find an easy source for that data so I can make a wise choice?  



Driven5 SuperDork
10/13/17 11:02 a.m.
frenchyd said:

What I'm looking for is a giant spread sheet that will tell me, should I go with a 15x10 and 27 inch tall tire but 11 inches or tread or should I go with a 19x8  still a 27 inch tall tire  but less tread. 

No such thing like that exists.  If you want it, you'll have to want it enough to make it.  I made this to help with my decision, using the Tire Rack shop tires by size tool and looking at number of tires available in each performance category of the filter.

Of course, you still need to narrow it down to a general OD and width range, then look up each possible size in that approximate range.  Picking the OD and width also need to take into account any bodywork. 

There are plenty of wheels available for any popular tire size, with the main caveats being offset and bolt pattern.  Selecting a desirable offset should be selected to work with the tire and spindle to create the desired scrub radius, but there may be practical limitations based on the offsets run by the most popular performance cars that use those wheel sizes and bolt patterns.  Bolt pattern will generally be driven by the spindle  donor, unless custome drilling your hubs.  However, when selecting your spindle donor, keep weels in mind.  For instance, lots of 15" wheels are available in 4x100, but not so much for 5x114.3.  To get an idea of general wheel availability, even if there are many brands they don't carry, Discount Tire Direct does allow you to search wheels by diameter, width, and bolt pattern.

frenchyd HalfDork
10/13/17 12:06 p.m.

In reply to Driven5 : that is exactly what I'm trying to do.  I've tried to find Tire Racks size chart without success but since you sourced your data from Tire rack I will keep searching.  

You are right wheel follows tire selection, I wish it were the other way, pick wheel and then look at tires that might fit.  Even that if you search the entire wheel market is complex as heck.  

Fenders?  I'll make whatever I need my only question there is Aluminum or carbon fiber.  Right now it looks like Aluminum for fronts and carbon fiber for rears. But that assumes my buddy will let me use my old English wheel.  

Then too I really should make two different sets of Fenders. One for my pin drive Halibrand magnesium knock offs  to be used for static displays and another for the racing wheels. 

Driven5 SuperDork
10/13/17 12:23 p.m.
frenchyd said:

I've tried to find Tire Racks size chart without success.

The size charts are available for individual tires by looking at the specific brand/make/model of tire on their website.  Find popular ones by looking at the "Tire Ratings & Reviews" for the performance categories you're most interested in, and look at the size charts for each of the best reviewed tires in those performance categories, and try to identify sizes you might be interested in that are also common between them.  That will give you a good starting point for looking at overall availability in various sizes, as in my previous post.

Keith Tanner
Keith Tanner MegaDork
10/13/17 12:39 p.m.

Tire Rack also has a chart of all available sizes - "tire sizes by wheel diameter". One click per size and you get an idea of how popular each one is.

I'm in the "pick the tire size, then pick the wheel" camp.


GameboyRMH MegaDork
10/13/17 12:46 p.m.

For tire selection and debead-odds-reduction reasons, you should go with a 17"~19" diameter wheel. These are the sizes most performance tires are made for these days. 15" performance tires will only be around for as long as people are racing old Miatas and Civics, and 16s have always been the unavailability valley for performance tires.

Recently I chose 18x12" wheels with 315/30/18 tires for a design aiming for 2700lbs and 600hp. If you're aiming for less power with your design you could scale down the width...personally I wouldn't because I like crazy grip and the look of wide tires too much cheeky

Streetwiseguy UltimaDork
10/13/17 12:52 p.m.

You can use whatever tire suits you, but you need to decide what is important to you.  If low price consumables is the point, go 15 by 10, and run super late model 10 by 26 inch tires.  They are available in about a hundred different compounds, you can generally find a used sets at your nearest short track, and you build the rest of the car to suit the tire.    You want ultimate performance and damn the cost, figure out what a Daytona prototype uses, and build for them.  At first thought, I think the biggest difference might be how much brake you can jam into the 15's, but there are an awful lot of relatively cheap late model brakes that will scrub off 25mph every eight seconds for an hour at a time.

I'd build for late model tires, but thats just me.

frenchyd HalfDork
10/13/17 1:15 p.m.

In reply to Streetwiseguy :

I like the way you think, while I intend to drive to and ( hopefully from) racetracks I have no issue with street driving race tires. My MGTD has Dunlop race tires and they've served me well.  Besides it's a pretty petty cop that writes a ticket for non DOT approved tires.  If they even know such a rule is on the books!! 

However finding light 15x 10 wheels with the proper back spacing is extremely problematic.  

You don't know of any do you?  In a perfect world they'd be light and  a number of spokes  more like wire wheels than American racing mags. 

Do I even need that much rubber?  Won't it slow me down?  I once beat Sir Sterling Moss at a autocross in the Bahamas because his factory Aston Martin DBR2 was about a foot wider than my Blackjack special and the added distance he had to drive offset the extra 150 horsepower his car had.  

My goal is 400 horsepower and 500 ft pounds of torque in a 1500 pound( dry weight) car. 

Jere Dork
10/13/17 1:29 p.m.

 I would be looking at 6 uls 15x10 pretty seriously if you aren't limited by the bolt pattern too much. 

Driven5 SuperDork
10/13/17 1:34 p.m.
Keith Tanner said:

Tire Rack also has a chart of all available sizes - "tire sizes by wheel diameter". One click per size and you get an idea of how popular each one is.


I never noticed they added that...Good to know!

frenchyd HalfDork
10/13/17 2:00 p.m.

In reply to Jere : the hubs I have are 5 bolt 4&3/4 bolt circle but easily re drilled.  But stock car steel wheels will have too little back spacing  and be massively too heavy.  Then you add that heavy stock car tire and the whole assembly is going to put me too far over the weight schedule. Necessitating heavier suspension arms, springs,  swaybars, and ultimately chassis.  


frenchyd HalfDork
10/13/17 2:03 p.m.

In reply to Driven5 : hey wow !  That's great!  I got my work cut out for me tonight  


frenchyd HalfDork
10/13/17 2:07 p.m.

In reply to GameboyRMH :

You make a good point.  While lightly used 15x 27 stock car tire sizes are readily available at really nice prices   Using them limits my wheel choices and adds a lot of weight


frenchyd HalfDork
10/13/17 2:41 p.m.

In reply to Robbie :

I'm lucky, while my final drive ratio is fixed at 3:54  I'll be using a Senz dog ring  quick change gearbox.  Like a quick change rear end I can select a variety of ratios for the 5 speeds, pull off the back end and slide a different ratio right in.  On the bench it will take less than 5 minutes to change any or all gears.  At the track it's closer to a 1/2 hour.  

Since autocross is typically a 2 speed track at most I can select the best 1st and second gear so I hit peak power just before I slow for the cones.  

Since it's a dog ring I won't have to pause as I shift to let the synchro slow down the gear.  Just slam it in the next gear as fast as my hand will move without touching the clutch. 


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