I have an '83 Audi Quattro that I just started to build and as I tested it on the Festival Circuit I hear a scraping noise as I take the first turn (slowing down). Initially I thought it was the ride height (which I had set to min, 5.3/5.3 F/R) so I increased these yet had the same noise. I checked telemetry and then saw that the springs were not bottoming out at all during that turn. However, as expected I did see all the weight transfer to the rear right side tire of the car. So, I wanted to get some insights as to is this normal? Is there something that I need to change on my settings? If so, what areas can I start focusing on? Thanks!
Hello, this has happened to me while tuning on catalunya nationnal. On the firt corner.
I believe the ride height is too low and that the tyres are rubbing inside while turning the wheel. It was from my front tyres that the sound was coming from.
I kind of resolved the problem by raising the ride heigt a bit and stiffening the front.
Hope this can help.
Cheers
Hi Rosny! Forgot to ask did you mean stiffen the springs, ARBs, or both? I would expect that the camber value (-3.5) would have an impact as well? Thanks!
The front springs. Play with the front rebound. If it doesn t help stiffen the front springs
Thanks Rosny! From the telemetry I could not pick that up since it is side scrapping I guess. Good to know. Not sure if for me is the front or rear since I do see a lot of the weight shift towards the rear right tire. I’ll check both, though will be hard to hear front/rear diff. I’ll stiffen up the front (or rear) since I have already turned up the RH 3-4 clicks.
UPDATE – This pitbull problem does not want to go away. Rosny, I took the Rebound from the 11 range down to 5, and bump up/down from 1.5 to 6 and noise is still there. I just tested FB @ 13 and RB @ 1 and vice-versa = same! I also increased the front ride height to maxi (from 5.3 to 7.4) and still no change to the noise. I am still wondering if it is normal, yet, does not seem so. I zoomed into when it happens and is primarily when turning and releasing throttle or slight/mid braking for the turn.
Any more ideas out there? Thanks!
What is the tune exactly ?
Here it is…any thoughts? Thanks!
Tires F28.2 R29.3
Gearing 3.43//3.02/1.94/1.43/1.13/.93/.79
Camber F-2.5 R-2.0, Toe F0.0 R0.0, Caster 6.2
ARBs F27.80 R21.20
Springs F638.1 R365.3 RH F5.3 R5.3
Rebound F10.1 R9.0 Bump F2.1 R1.8
Aero N/A
Brake balance 48% force 105%
Diff Front (acc40% dec10%) Rear (acc60% dec10%) Center 50%
Try with less Camber/Caster
Hmmmm, interesting. I initially replied to Rosny thinking that camber might have an impact (which I initially had at -3.5)
So I dropped to -1.5 yet same issue. I will reduce even further. I never changed the Caster, so, will try that as well.
Thanks Drows!
Stock caster is at 5.0.
Urrrrrggggg…OK, just tested Camber down to -3.5 and up to +2.5, no change. The, onto Caster, went to 1 & 7 (extremes) and mid-points, no luck. Just tested the stock number 5.o, same issue…
Interesting…I went to 100% original stock car (C451 PI) and it has the same noise. I guess that’s the answer!
Again, the issue is when I left off throttle or brake. Still, could it be normal on this car? If anyone has this car it be great if you could check it out. Thanks!
I’m going to assume you have a supercharger installed. At speed with this part if you decelerate with no throttle applied you will encounter the sound you mentioned. With any throttle at all applied you will not spool down to that point. Just a guess.
It’s a good guess. Actually, I initially was going down the same line of it being most likely the turbo while decelerating. The stock car comes with a Single Turbo. No conversion and/or upgraded Race Turbo. I tested with both the Race and Stock with no difference in noise.
Could try offsetting your rh so rear is higher than front or vice versa. If it’s a weight problem this might help shift the balance but settings this way also promote oversteer(rear higher) understeer(front higher) just something to try
Thanks for the tip. I’ll try this out. I had done some RH adjustments yet I believe it was increasing both.
I suspect the car is experiencing “jacking down” due to low bump and high rebound damping . . . I remember seeing track undulations at the first corner of Bernese Alps.
At each successive suspension compression, the wheel cannot return back to original height to absorb the next compression. Therefore the suspension keeps on getting rapid successive compressions resulting in bottoming out.
Logic states, if driving over 3 successive bumps, 1" high, spaced to perfectly match the car’s suspension’s frequency:
Bump 1: Wheel rides up by 1", returns by 0.2" = ride height reduced by 0.8"
Bump 2: Wheel rides up by 1", returns by 0.2" = ride height reduced by 1.6" total
Bump 3: Wheel rides up by 1", returns by 0.2" = ride height reduced by 2.4" total
This is GROSS OVERSIMPLIFICATION of what happens but that’s the concept.
Suppose the car drives over more than 3 bumps in succession . . . Bottoming out, from my point of view, woud be inevitable . . .
That’s my logic.
My recommendation for fix = increase bump and decrease rebound thereby bring those numbers close together so they are happily in the equator instead of freezing at the poles.
Thanks GRD! Your comments/logic of this issue certainly make sense. I’ll try the Rebound/Bump combo change as you suggest. I had been keeping bump down per many of the threads on Rebound versus Bump %'s on Forza 5. Yet, as you have stated before, some of these generalities at times do not apply for particular cars/tracks.
I had actually given up on this, so, back to my garage to pick up the Quattro. I’ll post back once I play around with the settings.
Again, thank you! Lately I have seen many “noise” problems and need to learn from this one and apply as I see fit and/or need.
So, changing the springs (thus frequency) should help as well? F = (1/2PI)(k/m)^(1/2), k=spring, m=car’s mass, PI=3.14, F-frequency