How do you determine "ride height" to make suspension mods??

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demon34071

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Well I am about to get my triangulated 4 link set up in the works and everyone keeps telling me I need to FIRST determine my " Ride Height " in order to get the car set where it needs to be so all of the brackets can be welded in at the proper places.

Well how do you determine this?? Is there a standard?? Or formulae??

Here is what I am working / my game plan:
I have a 71 Demon with a mini tub and 3" spring frame mount relocating kit already installed.

My game plan for rims and tires are as follows:
Rear Rims: 18" x 10" - Bullitt Wheels
Front Rims: 18" x 8" or 17" x 8" - Bullitt Wheels

Rear Tires: No clue what will fit yet, but would want to get a big tire in rear. Something like a 335 or 345 tire leaning towards a BF Goodrich KDW.

Front Tires: No clue what will fit yet, but would want to get a big tire in rear. Something like a 245 tire leaning towards a BF Goodrich KDW.

Tire issue is I have always been under the impression that I can't get my rims and tires till I get my rear end 4 link done and actually get everything measured up??

As for my rearend: I currently have a stock A- body 8.75 with lg bolt moser axels, housing is back braced, and sping perches have been moved in for the 3" kit.

Can anyone help me determine how to get my ride height determined so that i can get my fabricator to set the car at the right height when we starts my triangulated 4 link. Or at least point me in the right direction so I know where to head from here.

Thanks!
 
It really depends on intended use and what you want your final look to be. I used a very interesting method to determine my ride height. I was looking to go as low as possible so I set the rear frame on the axle housing then raised the car 3" which gives me 2" of travel and a 1" bump stop. I made my own triangulated 4 link and I just built the bars from there.

On the 18x8's in the front Plan on running a 225/45/18 tires and at least 6" backspace if you want to be able to turn the wheel. I am going to stretch my fender openings so I can run a bigger tire in the front.
 
Well intended use is going to a driver that handles like a new car. Something that I can get in and be comfortable enough to driver in the say the Pour Tour if I wanted to. Car will have the creature comforts. AC, plenty of sound deadening, Alter K front end, custom tri 4 link out back, large rim tires, "Pro Touring" car. 4sp GM OD trans, stroker 340 motor, big disc brakes all around. Will probably only go to the track once a year to hang out with my buddies who drag race, but I plan to drive the 1.5 hours there and back. No trailer queen here. So the intended use would be for a serious cruiser for long rides yet handles and hugs the country curvy roads, and yet won't bottom out on the hilly roads of Western PA. So I obviously can't slam it to the ground.

Does this help any??
 
demon34071 said:
Well intended use is going to a driver that handles like a new car. Something that I can get in and be comfortable enough to driver in the say the Pour Tour if I wanted to. Car will have the creature comforts. AC, plenty of sound deadening, Alter K front end, custom tri 4 link out back, large rim tires, "Pro Touring" car. 4sp GM OD trans, stroker 340 motor, big disc brakes all around. Will probably only go to the track once a year to hang out with my buddies who drag race, but I plan to drive the 1.5 hours there and back. No trailer queen here. So the intended use would be for a serious cruiser for long rides yet handles and hugs the country curvy roads, and yet won't bottom out on the hilly roads of Western PA. So I obviously can't slam it to the ground.

Does this help any??
Click to expand...
Yes it does a bit But you have to remember most coil over shocks are only built for 4-5 inches of travel so you can use that to help determine ride height a bit. The AlterK is an awesome set-up and should do really well for your intended use. I would also look at the RMS Street Linx for the rear they have done a ton of work and it will save you a ton of headaches. If I had the money I would have done the same kit But I had to work on a budget so I built my own rear suspension and I have a friend that owns a fab shop that is building my front K-member and suspension for me( see my thread about it in the suspension forum) But going low also improves handling by lowering the center of gravity (illinois roads are horrible and I'm going really low) because I am doing the same thing I want modern car handling in a classic car body. Look at the US Car-tool sub frame connectors too the really tighten up the chassis I can lift the whole side of the car by the rear frame rail now.
 
as stated, set it to what you like, use two jacks and raise or lower it, stand back and when you think it looks good, that's your ride height, only you can decide what you like, my scamp sits high and dry, like a 68 SS dart, lot everyone likes the look, but it's my car and my choice, and when they complain about my ride height, I tell them to build their own car and set it the way they want.
 
I might suggest that if you are set on the tires, buy them now. Take the wheels off of your car, set the tires in and then using floor jacks and jackstands, set the car to the ride height you like. This will also help in getting an idea on backspacing, axle width and whatnot. Also be sure that the wheels that you want to use have the available backspacing that you want/need, or you may have to adjust your plans accordingly.
I've seen more than a few builds go wrong because the wheels and tires were picked at the end of the build and the needed sizes couldn't be had.
 
Revhendo said:
I might suggest that if you are set on the tires, buy them now. Take the wheels off of your car, set the tires in and then using floor jacks and jackstands, set the car to the ride height you like. This will also help in getting an idea on backspacing, axle width and whatnot. Also be sure that the wheels that you want to use have the available backspacing that you want/need, or you may have to adjust your plans accordingly.
I've seen more than a few builds go wrong because the wheels and tires were picked at the end of the build and the needed sizes couldn't be had.
Click to expand...
Yeah I picked my wheels first and built my housing to match those measurements.
 
johnparts said:
Yeah I picked my wheels first and built my housing to match those measurements.
Click to expand...

I was really afraid that was going to be the suggestion. The tires and rims are going to be a nice chunk of change (that I am still working on saving up for)

I was also hoping to use housing I have with out cutting it down, but from the sounds of it that is not going to be the case either.....

Where's my ski mask I have to go to the bank! lol lol lol (banker's with hands in the air) Ha Ha Ha
 
demon34071 said:
I was really afraid that was going to be the suggestion. The tires and rims are going to be a nice chunk of change (that I am still working on saving up for)

I was also hoping to use housing I have with out cutting it down, but from the sounds of it that is not going to be the case either.....

Where's my ski mask I have to go to the bank! lol lol lol (banker's with hands in the air) Ha Ha Ha
Click to expand...
Yeah you will end up cutting down your housing sometimes as much as 4 1/2" like I did.
 
So is the only way to really figure out ride height would be as follows:

1) Buy rear tires I plan on using (ouch)
2) Buy rear rims I plan on using ( ouch, but not necessary to buy now if I have the tires?)
3) Set the car on jack stands:
4) While on jack stands establish the full stance rear and front with the rear tires up under the car. (may not nor does not need to be level due to stance)
5) Once stance is established -- Measure floor to fixed point on car and this is my ride height

Why does my creative mind think I can do this with math and my cnc router at work to save the cost of the tires and rims right now: Here me out on this:
I route a disc in MDF -- 18" Diameter to act as the rim
I route a disc in MDF -- 18" center & diameter of tire I plan to use this will act as the tire, hell I can even paint it black so my simple mind doesn't get corn-fused
I then use this wheel / tire MDF mock up to set my ride height.
I can do the both for front and rear (since I have no suspension on the car at all)

Would this basically do the same thing as buying the real parts? Granted I plan to buy the rims and tires (Feb/mar 2011 (tax refund check)) but wasn't planing on doing it now, yet the 4 link is going in now.

Any thoughts on my mock up idea?
 
demon34071 said:
So is the only way to really figure out ride height would be as follows:

1) Buy rear tires I plan on using (ouch)
2) Buy rear rims I plan on using ( ouch, but not necessary to buy now if I have the tires?)
3) Set the car on jack stands:
4) While on jack stands establish the full stance rear and front with the rear tires up under the car. (may not nor does not need to be level due to stance)
5) Once stance is established -- Measure floor to fixed point on car and this is my ride height

Why does my creative mind think I can do this with math and my cnc router at work to save the cost of the tires and rims right now: Here me out on this:
I route a disc in MDF -- 18" Diameter to act as the rim
I route a disc in MDF -- 18" center & diameter of tire I plan to use this will act as the tire, hell I can even paint it black so my simple mind doesn't get corn-fused
I then use this wheel / tire MDF mock up to set my ride height.
I can do the both for front and rear (since I have no suspension on the car at all)

Would this basically do the same thing as buying the real parts? Granted I plan to buy the rims and tires (Feb/mar 2011 (tax refund check)) but wasn't planing on doing it now, yet the 4 link is going in now.

Any thoughts on my mock up idea?
Click to expand...
Do what I did go to your local tire shop and get a junk tire the size you plan on using and buy 1 wheel. Then from there you know what the finished result would look like. Tire very on size with different rim sizes so your 26" diameter tire will vary from 24" to 28" depending on rim width. I was originally going to run a 315 until I got it on a rim and it wouldn't clear my tubs had to drop down to a 285.
 
Oh and the rear end will end up being the easy part. Just wait until you have a tire on the front end and you can only turn the wheel 1/4 turn before the tires hit the fender. I had a hell of a time getting my tires measured for the front end and I still don't know what I'm going to run exactly. The rear was done in a weekend.
 
I found the lowest structural point which was where the front frame rails ran under the cab and met the torsion bar xmember. I sectioned 1" out of that because it was relatively easy and made it nice and flat to tack in a 5" piece of square tubing for the car to sit on.

From there the lowest point was 5" from the ground......well 4 7/8"

You will need a set of tires/wheels for the mock up.....I bought some junk wheels/tires off CL that were close to the height I wanted to run.

A 335 tire is going to need a 12" wide rim. Rims get expensive after 10" wide since cost is a concern. No problem running an 18" rim on the front, stick to about 26" tall tire (35series).
 
rjsjea said:
You will need a set of tires/wheels for the mock up.....I bought some junk wheels/tires off CL that were close to the height I wanted to run.

A 335 tire is going to need a 12" wide rim. Rims get expensive after 10" wide since cost is a concern. No problem running an 18" rim on the front, stick to about 26" tall tire (35series).
Click to expand...

I was figuring that the rear rims where going to have to be widened to 12" which I was thinking on having a set of the Bullet rims stretched to the 12" (yes added cost, I know but at this point I have tossed the budget way out the window, LOL)

Hmmm... now to find a set of used rims and tires on CL in 18" (I guess ford pattern) and as close to a 335 as possible.... I will have to see what that will cost versus just buying the rims and tires now....
 
demon34071 said:
I was figuring that the rear rims where going to have to be widened to 12" which I was thinking on having a set of the Bullet rims stretched to the 12" (yes added cost, I know but at this point I have tossed the budget way out the window, LOL)

Hmmm... now to find a set of used rims and tires on CL in 18" (I guess ford pattern) and as close to a 335 as possible.... I will have to see what that will cost versus just buying the rims and tires now....
Click to expand...

Having Weldcraft or similar company widen the rims will work. The mock ups are really for the front, since that is much more difficult to determine what will work. The rear is really just a tape measure number with a straight edge
 
Lots of good advise here, a couple of thoughts:

Bump steer the car (measure the suspension travel front and rear, use the current ride height measurements to establish the base line and make your decisions from there. You need to understand the base line and travel to understand where to relocate the rear suspension and what to set it at. There are other considerations like what the car is used for and weight percentages for handling characteristics that drive set up. Chassis alignment as it relates to the front end geometry is also a consideration again determined by what you want to do with the car. Widths are pretty simple to measure, your toe plate idea would work well for that purpose, once you have that you can then make some tire and wheel size calculations. You can impact the ride and stance with wheel sizing also so so that should be part of the total calculation depending again on what you are looking for. Be certain you understand how to measure backspacing on wheels (much written on the subject). Then be certain you understand the carcass construction and tire size variation manufacture to manufacture (they publish the info) it varies. Also understand how the wheel relates to the tire if you stretch the sidewall or make it as tall as possible. When the MFG lists tread, cross section and height they will usually say on what size wheels. Understand how the total tire travel impacts things like fenders at the widest section of the tire. Tires and wheels are usually last for me, hope that helps.
 
Lots of good info here. I even like the MDF idea. If you are looking at buying Bullit wheels and then having them widened, why not just get American TT's with custom backspace? Could be close costwise. Like I mentioned earlier, check to see what the backspacing range is on the wheels you want. Example, if you decide that you need a 4.75" bs and all you can get is up to a 4.5", you are going to have to rethink the setup.
(Don't ask me how I know....)
 
Revhendo said:
Lots of good info here. I even like the MDF idea. If you are looking at buying Bullit wheels and then having them widened, why not just get American TT's with custom backspace? Could be close costwise. Like I mentioned earlier, check to see what the backspacing range is on the wheels you want. Example, if you decide that you need a 4.75" bs and all you can get is up to a 4.5", you are going to have to rethink the setup.
(Don't ask me how I know....)
Click to expand...

I already checked and American TT M's don't come in 18x12 either -- So regardless I am stuck with either widening the Bullit wheels or the American TT M's to get them to the 18x12 that I need. Since I have to widen them I can have the wheel shop set the back spacing at what ever I want. I am also waiting to hear back from COY's on a custom set of C-5's --- Figure by the time I buy rims, have them widened, then have the refinished to look right, I am going to have some coin in the rims so I am just trying to work out the most cost effective way of doing them.
 
FYI - Coy's won't make custom 18x12 C-5 wheels either. --- as per their email:

We only produce what is posted on the web site.
http://www.coyswheel.com/coys.html

On Wed, Oct 27, 2010 at 5:56 PM, Derek Libreht <[email protected]> wrote:
Your Email Message
Name: Derek Libreht
Email: [email protected]
Message: I am interested in finding out if you can do custom sized rims in the C5's -- I am interested in getting a cost on (2) rims in 18x12 - 5 on 4.5 mopar spacing bolt patter -- color would be either chrome and black or the chrome and dark gray.
Please let me know if this can be done and what it would cost.
Thanks
Derek
Pittsburgh, PA 15212

--
Coys Equipped
303-297-2697
5952 North Broadway
Denver, Co. 80216
 
Well after tons of searching and talking to everyone here I have determined my tires and a possibility for wheels:

Rear Tires: BF Goodrich g-Force T/A KDW 2 -- 335/30ZR18
Front Tires: Will be same type and they have plenty of sizes for me to get it work.

Wheels: Billet Specialties offers 18x12's in 2 styles that are close to the Bullit Mustang wheels -- These are Dagger G & Mag-G

With that done. As for determining ride height everyone said to order the wheels and tires and use them to set the car where you want it and they start building. Well since I do not have $2300 for the rear wheels and tires at the moment I am going to build some mock ups to do the same thing. Give me a week or so and I will post my pics. But her is the plan:

Cut (2) disc's out of 3/4" plywood or MDF on my CNC at work the same size as the tire diameter. On same discs route a groove at 18" to show the rim and at same time this will give me an idea of sidewall. I plan on then taking the (2) discs and screwing them together with spacers at the width of tire wheel combo I am planing on. This will give me a pretty accurate idea of my wheel and tire combo. I can then lower the car over the mock up wheel to set my ride height. --- I plan on repeating the above for all (4) wheels to get a true feel.

hope it works!
 
UPDATE::: Finally got my mock up mdf/plywood wheels and tires done.

Here is what I mocked up to help determine my ride height:

wheels - 18" painted silver (cause that's how my brain works)

Rear tires - 335/30ZR18 -- 25.9" Overall diameter and 13.5 overall section width on a 12" wheel -- painted black (cause that's how my brain works)

Front tires - 235/35ZR18 -- 24.5 Overall diameter and 9.5" on an 8.5 rim ---not set on this tire and wheel width due to fitting issues, but needed to pick something and a 24.5 in tire seems to be the recommended size. -- painted black (cause that's how my brain works)

I even skinned one of the rears in black just to get a feel for the width when I mock up under the tire. Looks narrower than I want, but a 26" tire seems to be a good starting point for determining my ride height. Anyone running a taller tire on an 18" wheel with a mini tub?

Hoping to get the car off the rotisserie soon to try them up underneath to set the ride height.
 

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I can definitely tell you I have called, emailed, and no one will do an 18x12 -- Even custom ordered they still won't -- Bullitt Rims - NO ---- COYS -- NO

Only company I found who will do one is Billet Specialties, They make them completely custom to your backspacing in a style close to the Bullit Rims for around $750/ each -- Not too bad for an 18x12 with custom back spacing.
 
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