Adonis

I am seriously considering to fit Leda's option b on my Type-R ver.6 and I need some fitback from people who use it.
Thanx.

JohnT

I am also considering fitting Leda B to my STI V5 Wagon, however I'm put off by comments about clunking noises. I think the standard STI 5 suspension is too hard at the front thus making the car 'skitish' at high speed, I'm not sure that Leda C would improve this without make the ride too harsh? It's a pity Pete @SS doesn't have a return policy if you are not satisfied.

Pete Croney

Hi John

All of our products have a return policy and at least 12 months full rtb warranty.

At Scoobysport, all senior staff own Imprezas. It is only by owning and using a car, on a daily basis, that you really tell what works and what doesn't. Other than Prodrive, no company invests more in R&D of its Impreza products than us and that is why our Leda suspension is so loved by its owners.

Adonis

Pete,
as I've realised you work for ScoobySport.
I would apriciate some information on Leda for my Type-R VI.
Living in Cyprus, I wonder how can I get Leda suspension, do you have any retailers here?
p.s. i sent an e-mail to SS asking info but I did'nt get a reply.

Thanx.

Adonis

DavidLewis

Pete,

Does this mean I can return my Brembo's after Donnington, then refit/remove them after each track-day

mike_nunan

Heh, I bet you knew I'd comment to this one, Pete!

OK, for the benefit of John and Adonis, here is a summary of my current understanding (FWIW)...

Rattling noises - LEDA have addressed this and have come up with a fix, which consists of an extra rubber isolator for the top mounts at the rear. I have not had this fitted to my car (which has the rattle) because having been in a "fixed" car I can still hear the noise, albeit at a much reduced level. However, this needn't worry any potential LEDA purchaser, thanks to Pete's excellent warranty. Comparatively few damper units exhibit the problem, so you can simply have some different units swapped in and away you go.

There is an abiding mystery surrounding this problem, in that I have had every single working part of my dampers replaced, and I still have the noise. The *only* remaining original parts are the damper casings (including the adjuster mechanisms), and it is very hard to see how these parts could be responsible for any rattles. However, in Sherlock Holmes style, when you have eliminated the impossible, what remains, however improbable, must be the cause. I simply haven't made the time to visit LEDA yet, as the noise is a nuisance rather than a major problem, but I will post an update once the changeover has been made.

Ride quality - this is a more interesting area. Dampers work by forcing oil through apertures, which leads to a degree of resistance that is almost exactly proportional to the speed of movement. Generally you want more resistance to the upwards movement of the wheels ("bump") than do downward movement ("rebound"). The difference is achieved by using one-way valves that prevent oil flowing through certain apertures during bump, but allow the flow during rebound.

The exact ratio between bump and rebound damping is important, especially for hard off-road driving. If you have too much bump damping, the dampers won’t let the wheels lift up enough, causing the car to "jack up" over sequences of bumps. The other way round and the car will "jack down" as the excessive rebound damping delays the car from settling back to its normal ride height after a bump.

LEDA's struts are superior to many other adjustable suspension units because they maintain the ratio between bump and rebound as you move the adjuster. There are dampers that allow separate bump and rebound adjustment (GT2 anybody? ) but they tend to be much more expensive.

However, there is one important parameter that LEDA don't allow you to adjust, and that is the high-flow bump setting. The apertures that the oil is forced through in order to provide the regular bump and rebound damping are relatively small. (LEDA have re-valved my dampers several times, and have made meaningful changes to the damper behaviour by widening the valve ports by just a few thou'.) If these tiny apertures were the only oil-flow channels available, consider what would happen when you hit a harsh ridge or the far edge of a pot-hole. A very sudden, high-amplitude shock would be transmitted up the damper leg, which would be almost locked solid. We would much sooner this was absorbed before it reached the car. The car weighs a lot, and won't be easy to move as a whole. Instead, we are going to put huge stresses into the tyres, wheels, suspension mounts and (since they're unyielding) the dampers themselves.

To get around this, suspension designers use a spring-loaded relief valve that is forced open when one of these big shocks hits the strut. The aperture is much larger than the small holes I talked about above, so that larger volumes of oil can flood through quickly.

The valve spring stiffness must be carefully chosen so that gentle inputs (e.g., due to body roll on turn-in, or gentle rolling bumps in a smooth road) don't open the valve. This way, you still get a nice taut feeling to the suspension. OTOH, you don't want the spring to be so stiff that really high damper piston velocities are required to open the valve, or undesirable levels of harshness will be the result.

LEDA go one step beyond most road suspension suppliers in that they actually have a choice of two different springs for the high-rate valve, which they also refer to as the "foot valve". LEDA call the softer and harder spring types the "road" and "competition" foot-valve springs, respectively.

I currently have a road-type spring in all four units, and I have a reasonably acceptable level of compliance. Any LEDA owners who think their ride is a bit harsh (most don't, it seems) would be well advised to speak to LEDA and find out which foot valve spring they have. You might be able to harvest some major improvements by replacing this 2p part!

In my case, I suspect that fitting an even softer spring would improve the ride without compromising the body control, as the ride can be a bit crashy at times. Maybe the manufacturing tolerances of the foot valve springs are a bit wide, as other owners don't appear to feel this. Whatever, one of the beauties of the LEDA kit is that you can visit the factory and work with Dave Lyons and the other guys to get the valving exactly right. Since I am planning a return visit to address the knocking noises, I will no doubt use the opportunity to tweak the valving further.

Some vendors right at the top end of the market (e.g., Ohlins, Prodrive - we're talking rally kit here) sell three-way adjustable damper units that have separate bump, rebound and high-flow adjusters. This is really the ultimate, but so are the prices. Try 20 *GRAND*, fitted, for the Prodrive kit. Also, the adjustment range on these units tends to be quite narrow (usually about +/-20%), as the adjusters are used as "trims" and any big changes in rates are done at the factory by altering the valving.

For road use, I believe a two-way adjustable system allowing pro-rata bump+rebound control on one adjuster and high-rate bump adjustment on the other would be close to ideal, especially if the high-rate had a nice wide adjustment range. This would mean you could really impress the misses with some seriously S-Class ride quality, then crank everything up for that street racer feel. PeteC+LEDA, are you listening??

TTFN

-= mike =-

Stuart Knight

iTrader: (2)

Great post Mike. Very informative and informed!

mike_nunan

Thanks for the kind words Stuart! I'd put in a "shy smiley" but I haven't found out where all these animated emoticons live yet (anyone car to enlighten me as to the location of the full list!)

Anyway, glad you enjoyed it, as it did take over any hour to write up -- I should be working really

Best regards,

-= mike =-

Pete Croney

Hi Mike

A couple of points that you know, but aren't clear above...

The valve settings that Leda use, as standard, are optimised for the spring rates which we prefer to supply the kit with. Before you decided to change these for softer springs, we agreed that firmer damper settings would need to be used to acheive similar body control. This is moving back towards the standard Subaru set-up, which uses soft springs and high damper rates... and gives that crashy feeling over bad surfaces (Incidentally, you are the only owner that has chosen to go softer on springs, but several have chosen to go firmer).

Leda do have a seperate bump and rebound adjustment system, which gets over the fixed rate high speed bump valve setting, but as with everyone elses, these cost over £2500 a set and are intended for serious competition use.

The vast majority of owners have taken our recommendations and all have commented on how well the system works with the Impreza chassis. A lot of these owners are "die hard" track day fans and races are won by carrying speed through corners, not by having massive power. Jack McFarlane rang a while ago, enthusing about his trial session in a Fiesta XR2 race car at Knockhill. His times were nearly as quick as his best in his (standard) 22B!!!

Mike, I know you have enjoyed your time at Leda, working with the guys to develop *your own* settings and rates etc, but you haven't said above if you actually like Leda suspension. This is what Adonis was asking. By the way Adonis, I've mailed you with some of our customers mails.

The noise... this was a problem on a few cars and we struggled to find the solution. The problem is that the rear of the car acts like a resonator box amplifying any sounds. It was Mike Wood at Prodrive that helped solve it. I was chatting to Mike about this and he said that they had had similar problems when developing their kits. He told me the answer lay in the standard set up (...and no more than that ). When we looked again, we realised why Subaru put huge great rubber mats in the system. Too much rubber will take away part of the suspensions action, so we developed a system which retains the control, but eliminates 99% of the noise. Cars with Leda units fitted, before this fix was developed, which have had noise problems... have had the modification done free of charge.

Leda's warranty back is legendary and the guys there share our philosophy that satisfied customers are our greatest asset.

mike_nunan

Hi Pete,

Didn't think it would take long

Ok, re the valve settings, the damper rates I have now are about equal to the 98MY standard kit when all my adjusters are set to zero. Set this way, my dampers produce almost identical suspension dyno plots to the original dampers from my car. To achieve this LEDA put extra valve apertures that I asked for, so my dampers can go softer than most other peoples' LEDA B setups. The upper end of the scale is still plenty hard enough, and I've never used more than about 70% of the range even on the track. Even on zero, the slight harshness caused by the foot valve springs is still apparent, however.

I should stress that this isn't a complaint - my suspension is still a joy across country and on the track. I'm just a compulsive perfectionist Virgo, however, and now that I have understood how the high-flow valving can be used to optimise the ride quality over London's pockmarked tarmac (where, sadly, I have to spend the majority of my motoring miles) I want it all! There is no doubt that my standard kit did much better in this environment, but for track and fast road use, i.e., where it really counts, I'll keep my LEDA kit thanks very much.

Another important thing that I failed to mention before is the one-way flow feature of the LEDA units. This makes the oil circulate continually through the outer tube, so that it gets much better cooling than in other twin-tube dampers. (In fact, the oil flows both ways, but there is a sort of "one step forward, two steps back" approach to the valving that means that it keeps circulating on average, IYSMIM.) This means that the LEDA units are comparable to Bilstein single-tube designs in their ability to dissipate heat. Single-tube designs can't easily be made adjustable, however, so unless you go up to a full rally-spec system, LEDA has at least one major advantage in its favour.

Pete, I wasn't aware that LEDA made units with high-flow adjust for "only" £2500, but that's good news. I might even be interested in a set! I've been looking into getting some ex-rally Prodrive units, but it looks like £3-4000 is the minimum even for used kit, and I'm not prepared to go that far. Before anything else, I'm going to see how far I can go by altering the foot valve stiffness, but it is a bit of a PITA having to get LEDA to strip all the units just to get at one tiny little spring. C'est la vie.

Adonis, sorry if this seems to have gone off the deep end when all you asked was a simple question. To sum up, this is good kit supplied by a firm with deep reserves of engineering skill and a strong competition pedigree. If you want to go as far as I have with the tuning side, you have the opportunity. If not, you can rely on a good enough level of care and service that you can essentially fit and forget. The caveat is, this is all specialist equipment compared with the mass-market stuff that came with the car, so there is more chance of minor issues and the need for a return visit. Don't let that put you off, as it applies to every aftermarket item, be it brakes, a new turbo, a dump valve or whatever -- if a salesman tells you different, he's probably trying to pull the wool over your eyes... 8)

Best regards,

-= mike =-

Steve Prockter

Very interesting to learn additional views about the mechanics of the suspension units. It would pay LEDA/SS to produce some detailed technical information of this kind (excuse me if they do and I don’t know about it), as it leads to a greater understanding of the product and how best perhaps to go about set up.

I would like to add my own comments about the handling characteristics of a so shod Impreza (LEDA C), which I will try and summarize in a small space (which is, after all, the main reason that most people change suspension). I’ve clocked about 800 track miles and 16,000 other miles on the road since July.

Braking…..the outstanding level of stability and car composure surprises. The sensation is as if the car has been sucked to the road.

Bumps and severe undulation……considering the firmness of the ride you might expect it easy to jump the car sideways mid bend over a large bump or undulation. Never does it though.

High speed bends…….100mph+ drifts just feel so natural. You always try it quicker the next time (p.s my favorite aspect of the suspension).

On the limit…….not as “playable” perhaps as the standard suspension, but very predictable and trustworthy. You can always lean on the rear with total confidence. It won’t let you down.

Turn in……go-cart.

Tyre wear…..good bye worn outer edges, hello even tyre wear.

Grip/feel…..dry road grip and feel is sensational, wet road grip is probably stronger than you think it feels.

Comfort….very compliant ride, never crashy. As though a cushion of air absorbed the initial movement.

Steve.

Adonis

Thanx Mike, that was more than informative and now I am almost sure what suspension to go for.

Pete, thanx for the mail, was good feedback but still have an unanswered question...
How can I be supplied with a kit here in Cyprus and how difficult is it to be fitted considering that there is no Leda expert here?

JClark

This is a very informative thread, thanks Mike, Pete, Steve et al.

I am thinking of having Leda B/C fitted to my STI 5 4-door, as I find the current STI suspension far too hard and crashy for our potholed Sussex roads! I need to impress the missus with the ride quality, so I am just wondering if the standard Leda setup will suit my requirements, or will I need to specify softer springs etc?

Jeremy