how to setup rear suspension without wheels and tires?

[mopar_freak]

Probly a extreme newbie question, Im in the middle of setting up a 3 link suspension on my 69' Roadrunner and I want to stuff really phat 20's in those wheel wells when Im all done so thats what Im trying to base all my measurements off of for ride height. But I dont have the wheels and all those suspension calculators on the net ask for tire radius...I dont have tires either and have no idea how big low profile tires are for 20" wheels. So I kinda feel like Im running blind with no rough estimate of how much tire is gonna be in the well and how much room Im gonna have in it. Any suggestions on how to go about setting the suspension up? Thanks

[Norm Peterson]

Go to www.tirerack.com and search for the various tire sizes that you are considering. Then go to the 'specs' pages for whatever you get 'hits' with.

There are other tire sites where you can get tire dimensional information - Discounttiredirect, vulcantire, nitto, and others - but tirerack's search engine is probably the easiest to use.

Just as general guidance, 20's end up being kind of tall. Even the 255/35-20, which isn't all that wide (about 10") and doesn't have much sidewall to speak of, stands about 27" tall.


The Tire Rack 'specs' pages look like ↓↓↓

http://www.tirerack.com/tires/tires.jsp?tireMake=Bridgestone&tireModel=Potenza+RE050A+Pole+Position&partnum=535WR0RE050APPXL&vehicleSearch=false&fromCompare1=yes&tab=Specs


Norm

[Bryce]

I would start by figuring out what tires you want. width and outside diamter is all that matters. Then make a mock up tire with that diameter and measure you clearance for width at ride height and full bump and turning lock to lock.

Good luck with your project.

[mopar_freak]

Thanks guys. Yeah Norm you are right 20's do get excessive and finding a wide 20" tire is kinda hard. The car is going to get mini tubbed and I would like to take advantage of that, I would like to run BFGoodrich g-Force T/A KDW 2's and the widest they come in is 12.5 on an 18" wheel. Which looks good on the Gforce Demon and it has 335/ZR18 in the back. I would rather have a wide tire stuffed under there than a tall rim. Unless anyone knows of tires that are wider I think Im gonna change my plan to 18's in the back, and I have rims that size sitting right next to the car haha :).

[HUSTLESTUFF]

With the right offset you can get 295/45/18 under the stock wheelwell. Here's mine.

[mopar_freak]

That is a nice 69'! Looks familiar....were you at MATS 2011 with that car by chance?

[HUSTLESTUFF]

That was me. Did you get a ride?

[mopar_freak]

No, I just remember seeing it around and I followed you into the gate. That car looked and sounded amazing!

[John Wright]

Try this Tire/Rim calculator (http://www.rimsntires.com/specs.jsp) for a great visual of what the tire will look like mounted on the rims. You supply the tire size and rim dimensions...it gives you a picture with dimensions.

[mopar_freak]

Wow thanks John, that calculator is awesome! Very useful

[Norm Peterson]

That tire/rim calculator works well enough most of the time.

But if you're trying to work to very tight clearances, be a little careful. It does not vary the tire section width (extreme width measured at the widest part of the sidewall), nor can you input any of the actual dimensions of the tire. Section width does vary as the wheel you mount the tire on varies from that tire's "measuring width", and a 315 width tire can vary a bit either side of 315mm.

It will also refuse to calculate for unusually wide or narrow wheels for a given tire size. For example, it won't do 315/35-17 on a 12.5" wide wheel even though that is a mfr-acceptable combination. (You'll find that the calculator arbitrarily changes the tire width up to 325, and when you force that number back down to 315, it'll then change your wheel width down to 12").

315/35-17's ↓↓↓ on max and min width wheels of the same offset (spreadsheet plot).


Norm

[mopar_freak]

Thanks for pointing that out, I wouldnt have noticed.

After you brought that up I played with it and I think that calculator might not be well thought out in some ways.....you can take a 335/30x18 and narrow the rim down to 4". But like John said good visual aid

[John Wright]

Another thing to note about the calculator....you can enter tire sizes that do not exist...so be careful there as well.

[mopar_freak]

Yeah I noticed that, but its good if you found the tire and rim you wanna run and you can kinda put in the specs and see how they will fit and kinda look like.