Hasbro
Hasbro Dork
3/1/13 10:55 p.m.

Preferably on line, doesn't have to get too technical. Just want to get a basic understanding of it. Fwd.

It seems that my build is leaning more towards a road rally car and am curious as to how similar mine is vs. rally. Higher travel, lighter springs, etc.

Thanks

irish44j
irish44j UltraDork
3/1/13 11:35 p.m.

You mean like TSD rally? I haven't done one, but I don't see why a stock/stockish suspension wouldn't be fine for that, seeing as you're on public roads doing "legal" speeds.

Or maybe there's more to TSD that I'm not aware of .

Hasbro
Hasbro Dork
3/2/13 12:02 a.m.

Here's a decent read;

http://homepage.virgin.net/shalco.com/subaru_setup.htm

In reply to irish44j:

I've been building a street car that I want to handle as well as possible without giving up too much riding comfort. I am my brother's caregiver and the car was getting pretty uncomfortable for him. Some autox and some track days but 95% daily driver. I have Konis and soft springs and almost full travel with 3/4" drop from suspension and 1/2" from tires. Coilovers gives more travel back. Springs are 15% heavier in rear and 25% in front from stock but car will 20% lighter than stock so not that soft. But on full soft and low tire psi, the bro is happy. When he's not in the car it gets readjusted.

So, after watching a bunch of the older road rally cars they had a bunch of travel and tenacious grip and a decent ride. I figured they might have some tidbits of suspension dos that would apply to my situation. I have an EP3 Civic Si, which isn't crazy about extreme drops anyway. Just fishin', I guess.

I'm pretty happy with the way the suspension is developing. Since I'm not trying to fit in any racing group, just optimal handling, there is more flexibility. Some slight connecting point changes, very little. Lots of caster, wider track, that kind of stuff.

Rally video (Stratos, Delta, etc.);

http://www.youtube.com/watch?v=mXgWWNJVdYA

GameboyRMH
GameboyRMH UltimaDork
3/2/13 6:48 a.m.
irish44j wrote: You mean like TSD rally? I haven't done one, but I don't see why a stock/stockish suspension wouldn't be fine for that, seeing as you're on public roads doing "legal" speeds. Or maybe there's more to TSD that I'm not aware of .

Yeah for TSD you want something stockish, even being able to go fast isn't a big advantage, never mind being able to go around a corner the fastest. Having to crawl over bad roads with rock-hard coilovers on the other hand, will definitely slow you down. In an offroad TSD I do, one of the regularly winning teams has one of the least capable vehicles, it's mostly about navigation skill.

fritzsch
fritzsch HalfDork
3/2/13 7:15 a.m.

This may shed some light on rally car setups and their suspension. Just a tiny bit of light though

http://autopitstop.net/car-improvements/progressive-dampers-vs-digressive-dampers/ said: One of the reason rally cars are able to do what they do, is a specially tuned suspension. The other reason is they use shock absorbers with digressive valving. Digressive valving is a revolutionary way of valving shocks that is entirely different than in usual shock absorber design. Traditionally shocks have more damping force at higher shaft velocities, and that’s why they are called progressive shock absorbers. These shock absorber design have multi-stage valving to cater to various types of road conditions. Despite of these multi-stage valving, they are quite different from digressive valving, which is opposite of how shocks have been traditionally valved. A digressive shock absorber has stiff, progressive damping at low shaft speeds (less than 3 inches per second). This helps to control car body motion like roll, dive and squat. At this point, it functions like a typical stiff racing shock absorber. At higher shaft speeds, between 3 to 10 inch per second the damping force is more or less constant despite the rapid change in shaft velocity! The result is the suspension is kept supple in response to bumps and irregularities in the road, therefore traction is maintained on bumpy roads by reducing suspension hop, yet provides a firm ride, even at the high damping rates needed for body motion control. First used with success in off-road racing, digressive shock absorbers have only recently made their way into the on-road racing area.
Knurled
Knurled UltraDork
3/2/13 7:25 a.m.

Stage rally cars have much heavier springs than street cars. Gravel is usually 2x factory and tarmac is more. Better dampers allow lighter spring rates, too, but they never get much lighter than 2x.

Some of the old Audi rally cars ran 750lb springs.

Hasbro
Hasbro Dork
3/2/13 6:32 p.m.
fritzsch wrote: This may shed some light on rally car setups and their suspension. Just a tiny bit of light though
http://autopitstop.net/car-improvements/progressive-dampers-vs-digressive-dampers/ said: One of the reason rally cars are able to do what they do, is a specially tuned suspension. The other reason is they use shock absorbers with digressive valving. Digressive valving is a revolutionary way of valving shocks that is entirely different than in usual shock absorber design. Traditionally shocks have more damping force at higher shaft velocities, and that’s why they are called progressive shock absorbers. These shock absorber design have multi-stage valving to cater to various types of road conditions. Despite of these multi-stage valving, they are quite different from digressive valving, which is opposite of how shocks have been traditionally valved. A digressive shock absorber has stiff, progressive damping at low shaft speeds (less than 3 inches per second). This helps to control car body motion like roll, dive and squat. At this point, it functions like a typical stiff racing shock absorber. At higher shaft speeds, between 3 to 10 inch per second the damping force is more or less constant despite the rapid change in shaft velocity! The result is the suspension is kept supple in response to bumps and irregularities in the road, therefore traction is maintained on bumpy roads by reducing suspension hop, yet provides a firm ride, even at the high damping rates needed for body motion control. First used with success in off-road racing, digressive shock absorbers have only recently made their way into the on-road racing area. - See more at: http://autopitstop.net/car-improvements/progressive-dampers-vs-digressive-dampers/#sthash.Lgin1vnC.dpuf

Bingo! Thanks so much.

Kenny_McCormic
Kenny_McCormic Dork
3/2/13 7:22 p.m.

The thing that makes TSDs fun, at least in my limited experience, is the set average speeds are quite challenging in a street car on normal all seasons or snow tires. Going through one in a stage rally car on proper gravel or snow rally tires would be boring.

Keith Tanner
Keith Tanner MegaDork
3/2/13 10:46 p.m.

Digressive damping isn't that unusual these days, honestly. I think Racecar Engineering had a recent article on regressive damping in some new Penske shocks. It's not all figured out yet, but it's working in some situations.

As someone who had given a shot at building a tarmac rally suspension from scratch - it turns out that it's not that different from a good track suspension with slightly softer spring rates and as much travel as you can handle. Not that much softer, though.

Hasbro
Hasbro Dork
3/2/13 11:15 p.m.
Keith Tanner wrote: Digressive damping isn't that unusual these days, honestly. I think Racecar Engineering had a recent article on regressive damping in some new Penske shocks. It's not all figured out yet, but it's working in some situations. As someone who had given a shot at building a tarmac rally suspension from scratch - it turns out that it's not that different from a good track suspension with slightly softer spring rates and as much travel as you can handle. Not that much softer, though.

Would 3-3 5" of travel work?

Keith Tanner
Keith Tanner MegaDork
3/2/13 11:43 p.m.

Wheel travel? Eeek. Shock travel? Maybe, depends on your motion ratios.

Turns out, lots of travel comes in handy on the track as well.

Hasbro
Hasbro Dork
3/3/13 12:58 a.m.
Keith Tanner wrote: Wheel travel? Eeek. Shock travel? Maybe, depends on your motion ratios. Turns out, lots of travel comes in handy on the track as well.

I can go higher. Apples and oranges but what was your spring travel when you were using digressives?

Keith Tanner
Keith Tanner MegaDork
3/3/13 1:10 a.m.

I still am using digressive I'm at about 4" right now, I think. Might be 5" in the rear. It's been quite a while since I came up with the measurements.

You can really feel the difference on track. The car is more stable and I'm able to really work over the kerbs. One instructor who rode with me commented that "the track is wider for this car" We can learn a lot from the rally guys, just as they learn a lot from circuit racing. It's no coincidence that Loeb is untouchable on tarmac and a podium finisher at Le Mans.

Hasbro
Hasbro Dork
3/3/13 2:28 a.m.
Keith Tanner wrote: I still am using digressive I'm at about 4" right now, I think. Might be 5" in the rear. It's been quite a while since I came up with the measurements. You can really feel the difference on track. The car is more stable and I'm able to really work over the kerbs. One instructor who rode with me commented that "the track is wider for this car" We can learn a lot from the rally guys, just as they learn a lot from circuit racing. It's no coincidence that Loeb is untouchable on tarmac and a podium finisher at Le Mans.

Cool beans, Keith. Would Koni be one of the more affordable places to start inquiring with?

Keith Tanner
Keith Tanner MegaDork
3/3/13 1:53 p.m.

Dunno. The most important thing is to find a company that wants to work with you, not just take your money. Koni isn't really going to be working with individuals, they're mostly a manufacturer making the raw materials that some other people play with. Same with Bilstein.

Personally, I found working with AFCO very effective. I could specify the length of my shock body, length of the shaft, mono- vs twin-tube construction, number of adjustments, type of mount top and bottom and they were happy to work on the details of the valving for me. Plus I can do some limited servicing and modification at home without any specialized equipment.

But you're talking about a custom suspension. Affordable is going to be a relative term.

Hasbro
Hasbro Dork
3/5/13 2:14 a.m.

As usual, you were right, Keith. Had a nice conversation with a tech at True Choice. He suggested that I look at the Penske 7500 series, which is a little out of my league right now. So the whole idea will have to wait. We talked about my desire to keep the travel as long as possible and he felt I should just increase the spring weight on my Koni Sports if/when needed before considering other options such as double adjustable Race Konis etc. Left me feeling pretty good about what I have.

Hasbro
Hasbro Dork
3/5/13 2:16 a.m.
Hasbro wrote: As usual, you were right, Keith. Had a nice conversation with a tech at True Choice. He suggested that I look at the Penske 7500 series, which is a little out of my league right now. So the whole idea will have to wait. We talked about my desire to keep the travel as long as possible and he felt I should just increase the spring weight on my Koni Sports if/when needed before considering other options such as double adjustable Race Konis etc. Left me feeling pretty good about what I have. But don't worry, Keith, I still have plenty of other things to pester you about - pulling the fenders in a couple of weeks.
Keith Tanner
Keith Tanner MegaDork
3/5/13 11:13 a.m.

Drop a line to AFCO. My setup runs about $2000 all in, it's a very affordable option in the world of high end custom shocks.

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