Questions about Springs and Suspension

[Jay Mann]

Now that 33 Coyote is on the road, it is obvious that it has plenty of torque and horsepower. Getting all that power into the pavement is going to take some significant practise. As stated in another post, the big Wilwood Brakes are more than capable of eye ball sucking stops. The car has exceeded my expectations, but it is not in my nature to leave well enough alone.

So now I am interested in learning more about suspension and fine tuning the ride and handling of the car to suit the driving conditions in my area. After reading the excellent threads by Dan and Tom on both forums, I ordered the QA1 setup from Dan as soon as I ordered the kit. I fine tuned the shock mount bracket with a ball peen hammer ( it actually looks OK), the configuration of the shocks and springs fit into the car perfectly.

Tom mentioned the quality of the roads north of the Mason-Dixon line, well the roads north of the 49th parallel can be another story altogether.... Because of the large brakes, I have to use 17" rims on the fronts, the side wall height is limited by the need to run bike fenders ( no fenders will get a ticket from the local constabulary every time). The rear tires could be higher but the selection of tires that would work is limited. I am using Falken 452, 245/70/17 and 295/30/18 now. When these wear out I may change to the Azenis 615K which are available in a 295/45/18.

I am expecting to use two setups for the car, one for street and one for tracks days. If I have to change springs and tires for the odd track day, that is no problem. In fact the current confuration is probably very good for a track. So now I want to set the car up for everyday driving on Canadian city streets.

Question 1 - Spring rates - I do not understand why the rear springs are so much heavier than the fronts. I do not have access to the car for exact measurements, but the lever arm effect effect on inboard shocks results in approximately a 2:1 ratio, so the #450 lb/in front springs are effectively #225 lb/in. The rear springs are #325 lb/in. Since the weight distribution of the car is close to 50/50, I would have expected the fronts to be a little stiffer than the rear due to weight transfer when braking and cornering. Has anyone tried a #250 lb/in or lighter rear? The car has such a low CG that I do not expect to need sway bars for street use unless the springs get too soft.

Question 2 - Wheel hop - I have no experience in high torque light weight cars. I have spent enough time standing on the start line at a drag strip watching inexpereinced drivers to know that wheel hop after shifting can ruin a good day. When pushing the car a little I am experiencing wheel hop after shifting into 2nd and 3rd. After shifting I wait a split second before adding more throttle, but just a little too much and the back end starts bouncing. Any suggestions about how to reduce this effect?

[skullandbones]

Hi Jay,

I have a roadster so I hope you don't mind my joining in. I am recently interested in suspension also since I just go mine on the road. So I was wondering what rear end and suspension setup you have. Sorry: haven't seen the other threads where you probably mentioned the setup. But I think there is knowledge to be found on the forum that can be transferred from one type of car to another (sometimes). That's why I'm curious as to what you are doing with the hot rod. I have a link and have not experienced the "wheel hop" that many people have reported for that particular set up. Thank you, WEK.

[Jay Mann]

Hi Jay,

I have a roadster so I hope you don't mind my joining in. I am recently interested in suspension also since I just go mine on the road. So I was wondering what rear end and suspension setup you have. Sorry: haven't seen the other threads where you probably mentioned the setup. But I think there is knowledge to be found on the forum that can be transferred from one type of car to another (sometimes). That's why I'm curious as to what you are doing with the hot rod. I have a link and have not experienced the "wheel hop" that many people have reported for that particular set up. Thank you, WEK.

Hi,
I am using a 4 link, Tire pressure at 26 psi. QA1 Ultra ride shocks set on second lowest rebound setting. 10" 325 lb/in springs with some preload.

Thanks,
Jay

[skullandbones]

Jay,

Do you have the same multiple (3) holes for the inner upper rear control arms as on the roadster? I have mine set in the middle position but I thought I had them in the aggressive drag racing mode (forgot!). I don't know what the difference is in the geometry between the roadster and hot rod but if you have those adjustment holes, it might be an option just to test the "wheel hop" issue. It didn't explain in the manual which setting would reduce that problem but it does say the lower position is best for straight line launches. You may have already addressed this but just in case you haven't. You obviously have the spring and shock variables covered! Thanks, WEK.

[Jay Mann]

Thanks for pointing me to the Roadster forum, there is a lot of info on wheel hop. After reading the material, I am thinking that what I am interpreting as wheel hop is actually just spinning tires. I have laid down over 50 feet of perfectly solid black marks on smooth fresh pavement, the only reason I let up was the car was going sideways. The car did not bounce at all when I did the burnout. The 33 does not have upper arm adjustments, only on the lower arm, I have it bolted in the lowest position for better traction. I have not seen anything on wheel hop in the 33 forums, so this also leads me to think that its just spinning tires. The vibration I am feeling might just be normal for spinning tires. It is rather conerning at 50mph +. Maybe my mother was right when she said the cure was to better control my right foot. I may set the rear shocks a little stiffer and see waht that does to the vibration.

[Godscountry]

Ride Tech cut the spring rate really low in the front and back and added sway bars.Thier 33 works so use what works,plus the ride must be so nice .As far as wheel hop,you only have to go to any drag strip in American,their are plenty of ultras fast Mustangs,look at the cars,video them and document what they have in the rear suspension.All the pieces should fit.add a little math some fine tuning,your 33 should knock off some quick 60 foot times,which is a good indicator all is well.Good luck

[Godscountry]

Ride Tech cut the spring rate really low in the front and back and added sway bars.Thier 33 works so use what works,plus the ride must be so nice .As far as wheel hop,you only have to go to any drag strip in American,their are plenty of ultras fast Mustangs,look at the cars,video them and document what they have in the rear suspension.All the pieces should fit.add a little math some fine tuning,your 33 should knock off some quick 60 foot times,which is a good indicator all is well.Good luck

One other bit of information,Jay,its a light car,a lose convertor if a automatic and make sure throttle response is quick,it should be up to engine speed quickly.I see your not in American,but I'm sure their is a active race and car community in Ecuador,get involved,share ideas,information.thanks for posting.

[CHOTIS BILL]

Jay,

The wheel rate will change at the square of the motion ratio so if you have 450# spring and a 2:1 motion ratio you have ½ =.500 and .500 squared = .250 so 450# x .250 = the wheel rate is 112.5# not 225#. You didn’t mention what the rear motion ratio is but you need to do the same calculations for the rear to find the rear wheel rate to be able to compare the front wheel rate to the rear wheel rate.

HTH,

Bill Lomenick

[Jay Mann]

Jay,

The wheel rate will change at the square of the motion ratio so if you have 450# spring and a 2:1 motion ratio you have ½ =.500 and .500 squared = .250 so 450# x .250 = the wheel rate is 112.5# not 225#. You didn’t mention what the rear motion ratio is but you need to do the same calculations for the rear to find the rear wheel rate to be able to compare the front wheel rate to the rear wheel rate.

HTH,

Bill Lomenick

Thanks for the info, can you recommend a reference book on suspension? I am a Mechanical Design Eng by training, but have never worked with dynamic suspension. The motion ratio for the rear is virtually 1:1. The springs are vertical on the live axle. If I understand correctly, the wheel rate of the rear is 350#, much more than front.

[frankeeski]

Hi,
I am using a 4 link, Tire pressure at 26 psi. QA1 Ultra ride shocks set on second lowest rebound setting. 10" 325 lb/in springs with some preload.

Thanks,
Jay

Jay, If I were you I would start by playing with tire pressure. I know there is a large consensus saying 10 lbs for every 1000 lbs of car but I have found that sidewall stiffness also plays a part. I run 18-20 lbs cold in my Roadster running 18" wheels and tires to give you an idea. The best advise I can give regarding springs is to start soft and gradually spring stiffer till it fits your needs. These cars can be very harsh when sprung too stiff.

[CHOTIS BILL]

Most of the books I read in the past don’t cover the later suspensions but there are newer ones that do. One newer one I can highly recommend is “THINK FAST” by Neil Roberts. Most books cover designs that are used but Neil goes into detail about design parameters. He has worked on cars from Formula Ford’s to Indy cars and knows what works and what doesn’t work so well. To do the actual design work on suspensions I bought a “Heath Kit” computer and wrote my own program which worked very well but was limited to 2D analysis. Back in the 80’s there were no suspension programs available to the public. Later I purchased “WinGeo3” which is a state of the art design tool.

Bill Lomenick

[Tom Veale]

Hi Jay,
I've not tried drag racing my '33 as of yet. I have the 3 Link which helps stablize the rear axle. I have noticed when I have the QA1's set for the street that at very high speeds the car gets pretty "floaty" (above 100 MPH). I did a seat of the pants test of the Koni vs the QA1 and found that the Koni's softest setting was about the same as Position #9 of 18 on the QA1.

I run the QA1 shocks at the 2nd softest setting for the street and it dampens most spring harmonics under street driving. However, that setting leads to the "floaty" feeling when running at high speeds on the track. I set the QA1s up to 4 or 5 clicks from softest for the track and it tamed it right down at 100+MPH. My guess is that if you crank in some more clicks on the QA1s they will tame the wheel hop.

Remember, once you're at about 9 clicks from softest, then you will be about as stiff as the Koni's at full soft. So, you should have some room between full soft and #9 that will give you control without shaking your kidneys loose!

Best regards, Tom

[Jay Mann]

Thanks to all for the advice.

I spent last week working on and driving the car. I installed 10" x 250lb/in springs with 2" spacers in the rear and 8" x 350lb/in no spacers in the front. The ride was noticably softer and acceptable on the frost heaves in the roads. With the QA1's set at 2 clicks it was a little floaty and wheel hopped when under load. When I went to 4 clicks, it calmed right down and I was able to increase my 0-60 time by 1/2 a second without hopping. The car does not lean much in the corners even when approaching the tire limits.

[[email protected]]

I have read all posts so far. I need softer spring or QA1 shocks part # and correct spring rate advise for rear. my 33 is a 4 link and has Koni's that came with kit. Koni's are set on softest and screwed up on thread adjustment about 2/3 of way to get rear higher. I want to use QA1 springs because they are chrome (old school). About how long and what spring rate for a cruiser. Front seems O.K on ride because it is low, not much preload about 1 inch on thread. By what was said in posts above I feel 10 to 11 in long 225 lb? advise needed.

[[email protected]]

New to Forum, How do I get in touch with Dan Ruth? A.K.A.Dr Ruth Does he have a website or an e-mail address? Is he one of the vendors?
Help needed

[Arm7419]

his number is 602 332 5398

chuck

[TigerBill]

I read this thread and the one on FFcars. Lots of good information and I am going to go with the QA1 shocks, but have a question about the springs. Everyone seems to say that longer springs are better. Can someone explain why? It seems like an 8" spring with a spring rate of 350#/in will act the same as a 10" spring with the same spring rate. Especially on a light car when deflection is minimal. Both will compress around 1 1/2 inch on the rear. What am I missing?

[Jay Mann]

I used 10" springs on the rear QA1s. I needed to use 2" of spacers for the rear. with 8 inch springs, I would have had 4 inches of spacer because of the thread length on the shock. 12 inch springs would require much more cutting on the axle mount. So 10 inch on the rear and 8 inch on the front are optimal.

Jay

I read this thread and the one on FFcars. Lots of good information and I am going to go with the QA1 shocks, but have a question about the springs. Everyone seems to say that longer springs are better. Can someone explain why? It seems like an 8" spring with a spring rate of 350#/in will act the same as a 10" spring with the same spring rate. Especially on a light car when deflection is minimal. Both will compress around 1 1/2 inch on the rear. What am I missing?

[TigerBill]

Thanks Jay. So the 10" springs are for fit up reasons, not for performance? The pics on your web site don't show spacers. Where the spacers added later? What ride height are you at on the rear? Thanks again.

[Jay Mann]

Bill,

I changed to the much softer 250 lb spring rate for performance and drivability. This was done after the pics on the website. I will update the website with new pics on my next trip to work on the car. I am running the car an inch higher than spec so I can clear speedbumps.

Thanks Jay. So the 10" springs are for fit up reasons, not for performance? The pics on your web site don't show spacers. Where the spacers added later? What ride height are you at on the rear? Thanks again.

[TigerBill]

Thanks Jay. I am definitely at least going to try the same spring rates as you since I already have some 250# springs and can move the ones from the back to the front. The rear especially seems too stiff. With the body off, my rear stock springs only compress 3/4" and the front springs only 1".

Lewieslaptop, here is a link to the thread on the FFCars forum where this issue is discussed at length and where Dr. Dan gives his recommendations. He still seems a little heavy on the springs and the front shock is 1" shorter than the Koni supplied with the kit. Since I am only compressed 1" now, I am not at the center of the shock stroke at the desired ride height (not compressed enough). A shorter shock would make that worse, I think. Seems like the next size up would be better - US404, compressed - 11.125", extended - 15", a lot closer to the Koni lengths of 11.15 and 15.15. But he certainly has a lot more experience than me. I wonder if there are some geometry differences in the earlier kits vs. the later ones. My rear axle is from a 96 Mustang. I ordered the QA1 US404 and the US502 shocks. We'll see how it goes. Here is the link.

http://www.ffcars.com/forums/120-fac...ristics-2.html

[Jay Mann]

Shocks and Springs 2.0 for 33Coyote

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The car is a continuous improvement project.

After 5000 miles, I decided the ride could use even more compliance on our rough roads here in Alberta. As mentioned previously, the car is set approximately 4 1/2" at the firewall and 5 1/2" in front of the rear fender. I found that the rear QA1 US502 shocks were at 16" extension, the max recommended sitting distance is 14 1/4". The front QA1 us 402 shocks were at 13 1/2", the max recommended sitting distance is 12 1/4". Since the shocks were so close to max extension, the suspension was not extending properly.

New configuration - The car is at the same height.
Rear Shocks - QA1 DS702, 16" ext ( within recommended envelope), 12" 200 lb/in springs with 1" spacer. The spacer helps clear the shock mount on the axle.
Front Shocks - QA1 US 502 13 1/2" ext ( only 1/4" shorter that recommended envelope) , 10" 325 lb/in springs.

The shocks are all set 4 clicks from softest at this time.

The new setup completely changed the characteristics of the car. The ride is still very firm, but it handles the frost strips, shallow potholes and pavement undulations very well at all speeds. It leans a little in the corners, but not much and is very acceptable for spirited street driving.

The car launches, corners and stops better also.

As referenced in my recent Bump Steer Post, the Tim Whittaker Bump Steer Kit has also contributed to the improved handling.

The big test has been a recent 1600 mile round trip to the coast with my father in the shotgun seat. We did 600 miles in one day with no discomfort or excessive fatigue.

BTW, over 20 USmpg average over whole trip.
__________________

[Jay Mann]

Tire and Wheel Update

For some reason the rear tires needed replacing at 8000 miles , So I changed out the Falken 295/30/18's for Nitto 555 315/35/17 mounted on 17 x 10.5 wheels. Using 1" spacers. These tires give me another inch of sidewall, which should help the ride and the traction.20150207_Avery_0088r.jpg

I prefer the higher ride height so I can negotiate the Alberta Roads better.