Need to get a set of new front shocks. Looking at the QA1’s just wondering if someone has the right shock number. I believe it is the ones with the 7” stroke but just want to make sure before ordering. Thanks
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Need to get a set of new front shocks. Looking at the QA1’s just wondering if someone has the right shock number. I believe it is the ones with the 7” stroke but just want to make sure before ordering. Thanks
Just because I've been shock researching today, I notice the Penske fronts are pretty reasonably priced at $215. each (7000 series).
I was just looking and thats a good deal for those. Do you happen to know what options on them I would need for a vee shock. They have a few options i was not sure about. Thanks RobQuote:
Originally Posted by BLS
No, don't have those myself. I'd recommend going through a suspension supplier that knows what you need for that shock. Penske states they are for FV, so they may be able to tell you what you need.Quote:
Originally Posted by Robber98
I sell a lot of shocks in this part of the world for Vee's and other open wheelers.
For the fronts for Vees's I've had some success in having them built with larger shafts to give more bump resistance. Any competent supplier can have them built that way.
While you can increase the piston bump spring and or the piston resistance, increasing the shaft diameter will give you a better results across all piston speeds.
Isn't this another way of saying you have increased the compression curve?Quote:
Originally Posted by Hawke
How does this improve grip? How do you know the front needs changing?
Brian
Compression is increased with the larger shafts.Quote:
Originally Posted by Hardingfv32
What i noticed was many if not all - were running a zillion bump stops give some extra bump. They had softened the front spring to increase grip, so the shocks needed little rebound.
End result was increased lap times.
Over the decades I have worked with FVs, I have found that front shocks valving is not all that important,
What is important is the amount of droop you allow for the front suspension. Bottom line shock droop trumps anything you can do with the shock valving.
The front suspension of a FV has enough friction to provide all the damping you need. Controlling the droop is way more effective way to tune the handling than anything else you can do. I learned this fact by dumb luck.
Steve
What effect did droop limiting have on the car ... More droop equals under steer or more grip in rear? How about less
droop? Greg Rice used this a lot on his vees but never reall explained how he tuned the car with it.
I modified a pair of shocks for the front of a FV. I had the shafts threaded at the top so I could adjust the droop length. During testing, we found that the car worked better the shorter we made the shocks. The last step was to remove the bottom nut and have the shaft pass through the rod end at the shock mount. We ran the car that way and got the best results. That setup left the shock serving just as a droop limiting device.Quote:
Originally Posted by veeten
When I was developing the push rod bell crank systems for the current Citations, Weitzenhof and I came up with a friction test that I run on the cars. For the test, I press the car down to see where the suspension would stay. I take a ride height measurement. Next I gently pull up on the car to see how high I can get the ride height to stay. The difference in the ride height is the amount of stiction/friction in the suspension. If you take that difference in ride height, say it is .25 inches and you multiply that difference by the spring rate at the wheel of the suspension, you get a number. That number is the amount of force it takes to move the suspension. When we started it was close to 40 pounds to move it. This made the car slide a bit before the tires gripped up. So the car would slip and then stick, hitching its way around a corner. The 87 car the frame would twist so the suspension gave as the loads increased vs having the tires slip a bit on the track.
When we first ran that test on the 1994 Citations, the suspension took about 40 pounds. If the frame is not very rigid, that number won't be a big deal. The 87 Citation was a quarter as stiff as the 94 Citation. The suspension of the 87 Citations and the 94 Citations were the same. But the frames were very different in torsion, and that becomes big issue as we developed the 94 version..
And Steve hasn't either.Quote:
Originally Posted by veeten
A normal car you lift a wheel off the track and you lose grip. The FV's trailing arm front end is a little more complicated. You lose camber when the car rolls... there is no camber gain that is found on regular race car suspensions. So with a droop limited FV (front), when on the limiter you loose grip with the inside wheel off the ground, but you do not lose as much camber on the outside wheel because of roll.
Is this a net gain or lose of grip for the front end? My testing using coil over shocks and spring rates 2-3 times as stiff as the normal (rear rates increased to match) indicate the front FV tire is not very sensitive to camber change. So if that is the case, then reducing roll with a front droop limiter is not a benefit. Thus, the main reason for the droop limiter is to reduce grip.
Brian
So what is it, you are increasing compression or rebound?Quote:
Originally Posted by Hawke
Brian
I have used Bill Mitchell's software to analyze suspension systems for decades. I still use it when I do suspension design or setups.
I have modeled the front of a FV in the Mitchell software. I modeled is as an a-arm system where the pivot axis of the upper and lower a-arms were perpendicular to the center line of the car. The software gave a very interesting analysis. I have done the rear end as well, where the rear is a double a-arm system with the upper and lower a-arms share a common pivot axis. The Mitchel software gives results that are totally consistent with how a FV works.
If you can get access to that software, you might consider taking a look at what it tells you about the FV suspension.
How did you simulate the axle side loads as found while cornering? These loads cause friction at the axle bell and transaxle interface.Quote:
Originally Posted by S Lathrop
My testing with this axle bell interface showed that improvements in friction reduction don't jump out at you.... say the increased rear grip causing the car to get a small understeer. I used a rear spring system that added no side forces. You still have side force from cornering. So for reduced friction at the bell I developed a teflon daisy spacer for the axle bell.
Brian
Brian,Quote:
Originally Posted by Hardingfv32
I have not done this type of testing on a FV.
What about the suspension loading that is exerting an outward force on the axle as the cornering forces are exerting a compression load on the axle?
Increasing compression, and also increasing the rate of increase. If you look at a graph of force/velocity, you will see the slope of the graph increase.Quote:
Originally Posted by Hardingfv32
Off coarse you are talking about a typical push rod style spring system. I used a pull rod system for packaging and driver adjustments features. This obviously adds load to the axle bell when cornering. This is a compromise I had to make to achieve other design goals. Cannot make a comparison statement about handling before and after this design change.Quote:
Originally Posted by S Lathrop
I can say a recent Nat Champion changed from push rod to a pull rod rear spring system and he did not report any dramatic change in car balance. So while reducing friction/drag at the axle bell is a benefit, it probably can only be measured on a 4 post chassis shaker using appropriate side loads.
Brian
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