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Re: XV Level 1 Suspension
[Re: 6o4o]
#46466
11/05/08 07:40 PM
11/05/08 07:40 PM
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Anonymous
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Re: XV Level 1 Suspension
[Re: boydsdodge]
#46467
11/05/08 09:37 PM
11/05/08 09:37 PM
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Joined: Jan 2003
Posts: 27,465
So Cal
autoxcuda
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Posts: 27,465
So Cal
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Quote:
I think this thread is going off topic, but it's great info.
Maybe we should have a section just for corner carving, suspension mods and tires.
Just start another thread about Handing wheel sizes. XV is just getting free advertising out of this one.
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Re: XV Level 1 Suspension
[Re: boydsdodge]
#46469
11/06/08 11:48 PM
11/06/08 11:48 PM
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Joined: Jan 2003
Posts: 5,387
Pikes Peak Country
TC@HP2
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master
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Pikes Peak Country
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So what do you want to know that hasn't been covered here? Yes, it can probably get a whole lot more in depth, but how deep do you want to go? What are your goals, rules, budget? It really can get out of hand if you let it, or you can really crunch numbers and do a lot of detailed, tedious work and get the stock appearing stuff to really kick butt.
Lets get some input from members AlexP, autoxcuda, or 6o40. The have a really serious autocross combos on their street cars and can tell you some of the pros and cons to these set ups as well as how they got there.
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Re: XV Level 1 Suspension
[Re: ThermoQuad]
#46471
11/08/08 01:36 AM
11/08/08 01:36 AM
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Joined: Jan 2003
Posts: 27,465
So Cal
autoxcuda
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Quote:
I would like some one to show me exactly how to choose the best set of leaf springs for my car's type of use and whom to buy them from.
That's always a tough one.
I'd get scale weights on your rear tires to help determine the right arch your desired ride height.
Is there something lacking in the balance of your car now to feel like you need new/different leaf springs?
Might be a good idea to rate your current leaves to know where you are at now. Car doesn't seem that bad. Then you have a better idea of what numbers you want to hit for improvement.
There's a lot of trial and error it seems with leaf springs.
Leaf springs are the linkage and the spring at the same time. The linkage itself bending, twisting laterally, and twisting longitudinally. It's movement is not easy to predict with geometry.
A 3,4-link etc type suspension is all linkage with just a spring attached to it to control the motion. The movement of the solid linkage is easy to predict with geometry.
We've run leaf spring circle track pavement cars for 7 seasons now and have acheived great success and lots of wins. At one time we had over 10 leaf springs in the crash cart to test and tune with!! The chassis builder also has a leaf spring rater (Longacre IRRC). We've run all kinds of leaf combinations too.
Actually this year they allowed 3 link rear ends in our class and we built one. One thing with a leaf spring car, the drivers say they are more forgiving to drive than the 3 link (or four link for that matter too). Our 3 link car got one more win than the second most winning leaf spring car (7 vs 6).  But we did get our third championship in the last 4 years. 
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Re: XV Level 1 Suspension
[Re: ThermoQuad]
#46474
11/08/08 02:33 PM
11/08/08 02:33 PM
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Joined: Jan 2003
Posts: 27,465
So Cal
autoxcuda
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Too Many Posts
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Posts: 27,465
So Cal
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Quote:
Based on my seat of the pants dynomometer and the feedback from others at the track I need more rear spring in the car.
I understand that I must remove the springs and calculate the current rate to determine the new rate, but now how do I order a set of springs with more rate that doesn't change the ride height and from whom??
The basics on leaf springs are rate (lbs/in) and arch (in).
There's people other than Tom reading this so here's an example.
Lets say you want a 150 in/lbs spring. Then you need to figure how much arch you want with the spring installed at ride height after the weight of the rear is placed on them. That's why you need to know what the weights are at your rear tires.
So lets say each rear tire is 900 lbs of weight on it. With a 150 lbs/in spring that would need 4" of arch (theoretically) to end up with zero arch. But you probably what a little more arch at static ride height, like 1". So you would get in theroy 150 lbs/in spring with 5" arch that would end up in theroy with 1" arch left installed.
Now that's in theroy. I dont think the leaf spring will actually measure that linear. When you're done making it, you need to get the force (lbs) at each inch of compression. OR find someone that is real familiar with making/using leaf springs for race cars.
Also the amount of installed arch and total compression you get in a turn will affect rear steer. Rear steer is when the outside rear tire is moved back relative to the inside rear tire. Then the whole rear end is pointing slightly to the outside, causing the car to oversteer more when near the most rear tire travel/compression.
Is a little induced rear steer good or bad? Neither. Depends on the setup you are running. But most run as little installed arch as possible. Remember those MP circle track zero arch springs.
Also the more installed arch you have the more leverage the rear end has to move the rear end from side to side. As usual, there are all kinds of compromises taking place here.
3 and 4 links have rear steer too.
BTW...
Coil springs out of the box will not measure as advertised too. And they will vary out of the box. There are some brands/models of race coil springs that are more consistant that others.
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Re: XV Level 1 Suspension
[Re: ThermoQuad]
#46475
11/08/08 04:55 PM
11/08/08 04:55 PM
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Joined: Jan 2003
Posts: 5,387
Pikes Peak Country
TC@HP2
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master
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Pikes Peak Country
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Tom, You definetly want to get the car on some scales as a starting point. You will want to get all the wheel weights, cross weights, and roll couple etc. figured out to tell you were you are at currently. Once you know that, then you can see where you need to go. When it comes down to purchasing the leaf springs, there are a few decent off the shelf, decent priced, performance options available from places like Afco, Landrum, and Speedway motors. You can look at some general weight breaks for various sizes in multi or mono leaf set up and spend around $150-200 per spring. these will all get you close to what you want to get a good set up. If you truly want to get a custom made leaf designed for performance and aren't worried about cost; there is a guy on the Pro-Touring board who knows more about leaf springs than anyone I have ever read. He is a formally trained engineer and trained under Dick Guldstrand for many years back in the hey day of trans am racing. First you have to register on http://www.pro-touring.com/ to gain access to the members list. Then look up member chicane67 and send him a PM. He does build custom leafs springs but does not advertise. Expect to spend between $500 to $1000 per spring, but these will be the best set of leaf springs you will ever see. The choices and options of main leafs and secondary leafs will amaze you.
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Re: XV Level 1 Suspension
[Re: TC@HP2]
#46478
11/08/08 05:56 PM
11/08/08 05:56 PM
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Joined: Jan 2003
Posts: 27,465
So Cal
autoxcuda
Too Many Posts
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Too Many Posts
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Posts: 27,465
So Cal
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Quote:
...
If you truly want to get a custom made leaf designed for performance and aren't worried about cost; there is a guy on the Pro-Touring board who knows more about leaf springs than anyone I have ever read. He is a formally trained engineer and trained under Dick Guldstrand for many years back in the hey day of trans am racing. First you have to register on http://www.pro-touring.com/ to gain access to the members list. Then look up member chicane67 and send him a PM. He does build custom leafs springs but does not advertise. Expect to spend between $500 to $1000 per spring, but these will be the best set of leaf springs you will ever see. The choices and options of main leafs and secondary leafs will amaze you.
Our high school auto shop teacher had a hobby stock chevelle circle track car. Somehow we managed to get Guldstrand Engineering to sponsor us a poly insert bushings front and rear and a front end kit. The old Guldstrand shop in Culver City was about 5 miles from our High School. That was before the Energy Suspension kits and you had to use the old shells like we still have to do for Mopar poly LCA bushings. Fitting those inserts were a total PITA btw. Lots of work.
I asked the guy that ran the part dept about rear leaf springs. He said that had a local place that would make them up and I should shoot for like 180 lbs if I had front spring with wheel rate like a camaro with 750 lbs coils. The key was a strong second leaf that came right up to the front spring eye to make the front segment solid. I think all Mopars are like that anyway but he was a GM guy.
Real nice helpful guy to a 19 year old at the time. I think his name was Buzz or something. Maybe I still have a card.
I've got the Guldstrand catalog from date 1990 that he gave me in my hand right now. They don't publish any rates or specs.
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