At the request of SRC's R&D department, we tested their shock absorber springs with the aim of getting up to date, understanding and ordering them at a theoretical level; and testing assembly and driving sensations at a practical level.
SRC currently has up to 12 different shock absorber spring references, (dis)ordered into 4 series of 3, 3, 2, and 4 types with designations t1, t2, t3, and t4.
SRC SHOCK ABSORBER SPRING RANGE:
T1 AND T2 SPRINGS:
Pending confirmation from the manufacturer, we identify that the T1 shock absorbers are the starting point for the entire range.
Likewise, also pending confirmation and thanks to seeing them equipped in 3 chrono series cars, we identify that the T1-Medium springs are equipped as standard on both the front and rear axles.
(In case this observation is the result of the bizarre imagination of the undersigned, we will consider it valid as it would be an ideal starting point).
Both t1 and t2 have 3 different types: soft, hard, and medium, providing 3 hardnesses according to the wire used. The difference is that t1 is short (6mm) and t2 is long (7mm). This difference in length would establish different resulting intermediate hardnesses between t1 and t2 applied by travel, not by wire.
T1 and T2 springs ordered by hardness (least to greatest) for practical purposes:
t2soft < t1 soft < t2medium < t1medium < t2hard < t1hard
T3 SERIES
The t3 series shows the extremes, with 2 references it would include the ultra-soft t3blt and the closed-coil tblock with only 1 turn of travel, meaning to lock the shock absorber with only a few tenths of survival. The t3s have the length of the t1s.
T4 SERIES
The t4 series appears to be made with the same wire, and the difference between its 4 types is their total length. Two peculiarities: the t4 springs have a central part with compact coils and ends with travel. On the other hand, their hardness is inversely proportional to their length, with the hardest being the shortest.
The t4.1 (5.2mm) have a single coil (turn) with travel at the ends and are the shortest in the series, the t4.2 (5.8mm) and the t4.3 (6mm) are the two intermediate references, with two and three open coils and a compact center. And the t4.4 (6.2mm) have 4 turns, being the longest and paradoxically softest. Given the same wire hardness, the force of the t4 springs is inverse to their designation and length; the t4.1s are the shortest and stiffest, and the t4.4s are the longest and have greater extension.
The first theoretical conclusion is that the entire series could be summarized in 5 references, the t1 and t3, as they show the extremes and 3 intermediate hardness levels:
t3blt < t1 soft < t1medium < t1hard < t3tblock
From this, I dare to propose to the brand a product "pack" with these 5 references grouped into one.
HARDNESS ORDER
Src springs ordered by hardness (least to greatest) for practical purposes:
T3blt < t2soft < t1 soft < t2medium < t1medium < t2hard < t4.4 < t1hard < t4.3 <t4.2 < t4.1 < t3tblock.
Practical equivalences:
The t3blt would be tactilely equivalent to the t2soft with the shock absorber head open 2 turns.
The t1soft would be equivalent to the t2medium, also with the latter having an open head.
The t2hard and the t4.4 have a similar feel and are difficult to distinguish. I consider them equivalent.
Likewise, to the previous ones, the t1hard and t4.3 feel similar.
WORKSHOP PRACTICE AND TRACK SENSATION TEST:
TEST BASES:
Four LANCIA S4 Chrono cars were used, two of which (cars "B" and "C") were completely new and assembled for the occasion, and two that were already tuned and run-in (cars "A" and "D").
ACKNOWLEDGMENTS.
We thank SRC for lending units "A" and "B" for the test, as well as my fellow enthusiasts Mike Onane and Jordi Borromeo for lending their units. I must also thank Toni Mulet and Ròmul Puig for their contributions throughout the testing period.
EQUIPMENT:
All 4 cars are equipped with the same motor (RM0109), the same guide springs (RM0805 short), and the same hard-rubber tires (RN0103), new for the test. RN0115 tires were discarded to prevent a tire with too much grip and rapid wear from masking the driving sensations of the test. Likewise, 4 pairs of the same braid, cut to the same length, were installed, and the motor wires were replaced with 4 pairs of the same type. The bodies were adjusted to the same screw openings, and the motors were secured to the chassis at the same ground height, 1.2mm. The front tire on all 4 cars is ultra-low profile, lowered, zero grip, with a front wheel diameter close to 16.5mm. The track widths of all 4 cars were adjusted to 61mm rear and 56mm front, from rim to rim.
CARS “B” AND “C”
To reach a point of stable running and operation, the 2 new cars ran for hundreds (or thousands) of sections over a month and a half, in their standard configuration, until they were considered sufficiently loose and comparable in mileage, especially to the competition unit “A”.
Even with slight differences in character between them, cars “B” and “C” always maintained similar behavior, moving past their initial stiffness to a point where testing springs was deemed necessary.
The shock absorber configuration for cars “B” and “C” was, as noted at the beginning of the text, t1medium on both axles.
CARS “A” AND “D”
The 2 cars that were already tuned had about 3 months of running time at the start of the test, were quite loose, and were used as extremes for comparison.
One of these two cars, “A”, was configured with a t3block rear and t3blt front, which is the extreme hardness configuration, proposed as ideal by most of the Legends championship specialists consulted.
Car “D” was set up with the opposite extreme, a soft t1 rear spring and a medium t1 front spring, to be able to compare the opposite extreme to the "hard rear soft front" mantra that has pursued us since the Ninco era.
I must admit that the test could have been done perfectly with cars “A” and “B”, but having two more units allowed me to always see the extremes (car “D”) or maintain the starting points as an anchor (car “C”).
HOW THE TEST WAS CARRIED OUT
Car "B" was chosen to make changes to the shock absorbers, while car "C" was kept with the initial configuration of T1medium on both axles to compare the changes. At the start of the test, "B" was the unit most similar in feel and times to car "A", which was considered the reference.
The 6 stages of a rally in Cerdanyola slot were chosen, being secret at the start of the test. All 4 cars completed one stage each on the 6 sections, observing behaviors and sensations.
Each track exit was done with clean tires.
The tests for each car or configuration consisted of two runs on tracks 1 and 2 in a sporty driving style, aiming to obtain a couple of lap times and noting sensations and observations:
TEST ZERO: Performed with unit “A”
TEST ZERO BETA: performed with unit "D" without timing, only sensations.
TEST 1: Performed with units “B” and “C” with the original springs.
TEST 2 to 6: The remaining tests were performed with car "B", making progress in spring changes. After each run of car "B" with its new configuration, cars "A" and "C" were driven to confirm the observations.
TEST RESULTS:
GENERALITIES (GENERAL CONCLUSIONS)
The chrono times for all configurations ended up being so similar that we decided not to include them as they are not explanatory of anything. The differences between configurations or cars are more about sensations, confidence in the car, and there is no single configuration that shows worse records than the others.
I have always noticed this fact with Src cars; in my fleet, I currently have 5 active units, two Peugeots, two Lancias, and a 914, and the times between the five cars differ by at most one second per section.
"The harder the rear shock absorber, the greater the need for counterweight": with the initial configuration, t1medium on both axles, surprisingly, the cars do not tend to roll over. Likewise, unit "D" with soft springs in the rear makes no attempt to roll over. When the hardness of the rear spring is increased, the leverage effect exerted by the body volume on the outer wheel of the curve supposedly increases, the shock absorber does not yield, and the car lifts.
"The frog jump": contrary to the previous paragraph, and to my surprise, with shock absorbers tending to be soft at the rear, instead of tending to roll over, the car makes a lateral displacement in the form of a half-jump (what would be the famous bullfighter's frog jump) when entering a corner, to continue its trajectory without further ado. This movement is heard with a "thud" when entering the corner and usually happens with very clean tires.
"Softer rear, greater braking";
"Softer rear, greater rollover absorption";
"Softer rear, greater traction"...
... would be the three conclusions that determine the benefits of mounting non-rigid shock absorbers on the rear axle. That is, soft or medium rear can work, and must be taken into account in the car's setup. The existence of these three observations negates the validity of the Ninco era mantra.
"But softer rear = squarer corners," The car stops more in corners. It is confirmed that it is a matter of setup. In this case, we correct the excessive mechanical braking with control adjustment.
"As we harden the rear and soften the front, the car becomes more inertial": That is, it enters deeper into corners and lengthens braking, maintains inertia better when releasing the trigger, and moves more like a 4x2 than a 4x4. This behavior has nothing to do with the running-in or tuning of the cars, which is why so much time was dedicated to adapting the new cars. The cars were fully lubricated and tuned, and it was by hardening the rear suspension and softening the front that car "B" showed more inertial behavior than car "C" (which, let's remember, maintained the original t1medium setup on both axles).
To rule out any variation of these general guidelines with the RN0115 competition tires, these were mounted on cars “A” and “B” at the end of the tests, resulting in the same sensations with an added grip and greater need for counterweights.
TEST ZERO
Car “A” / t3block rear / t3blt front / 4 layers of side counterweight
The first test is carried out with the car configured according to the classic competition setup, and sensations and behaviors are noted.
The car moves smoothly, with a round and progressive drift, easy to drive and swing. Cornering is so fast that the car tends to open up at the rear.
In fast and linked sections, the constant speed is extremely high, even when entering sudden braking zones too fast.
The car moves more like a 4x2 than a 4x4.
Deep guide, perfect gearing, very long braking.
Given the excessive drift compared to the other cars, counterweights were removed, leaving 2 layers per side as a balance point to prevent rolling.
TEST ZERO BETA (performed one week before the joint test)
Car “D” / t1soft rear / t1medium front
Thanks to having a unit assembled with this unorthodox configuration (one of the three softest springs in the catalog at the rear), we took the opportunity to confirm or rule out whether it was undrivable as is often preached.
The surprise was that in terms of times, car "D" was on par with the other three, and in terms of behavior, the following was discovered:
Enormous starting and traction capacity.
Cornering by closing the car on the inside.
No attempts to roll over, but adaptability.
Excessive braking.
The movement of the rear gearing that causes the sway of the wheel axle does not affect (at least noticeably) either noises or transmission failures. It is not the mechanical perfection of a crown moving against a pinion, but this movement is not noticeable.
When opening the throttle exiting a wide curve (drift on exit), the car performs a kind of "trajectory correction", sensing a kind of "traction control" effect that corrects the excess power and straightens the car. In all cases, there is no counter-drift, i.e., when exiting a curve at full power, the car "self-corrects". We have also noticed this effect at all times in cars "B" and "C" which have t1medium rear suspensions. In contrast, the rigid rear unit "A" drifts and moves flat, maintaining a block.
We theoretically consider the setup with soft range rear springs for possible low-grip terrains or dirty rallies.
TEST 1
Cars “B” and “C” / stock config / t1medium rear and front.
This is the standard configuration, in terms of times it shows to be on par with the other cars, and allows us to assert that not having hard rear shock absorbers is part of a car's setup.
Absence of drift. Lots of grip, rail-like, with great traction and acceleration.
More braking? Yes, high braking and acceleration capabilities.
In laboratory asphalt conditions (flat and clean Ninco), it is very safe, however, in real conditions (dust on the track or secret section), it is somewhat imprecise, or slow to react, or lacking in improvisation capacity.
Instead of drifting, cars "B" and "C" do the "frog jump."
Feeling that it doesn't let us fully enter the corner, doesn't let us turn smoothly, as if it were too grippy.
TEST 2
Car “B” / t3blt rear / t1medium front
To corroborate TEST Zero Beta, on the same day as the test, we lowered the rear hardness to the softest level in car "B", which was chosen to make the changes.
We confirm that the soft extreme of the rear spring increases the sensations of TEST 1.
Huge traction, possible dirty setup, more braking than with t1medium, more grip, more digging in on corners.
TEST 3
Car “B” / t2hard rear / t1medium front
Configuration with the two spring types from the center of SRC's hardness range. Short rear travel and non-soft (but not-hard) front.
By stiffening the rear axle a notch, the car brakes less and allows turning in corners, drives more flat and at the same time starts to lift a bit, especially in the first laps with clean tires.
We begin to consider the previously mentioned need for counterweight. It feigns rolling over due to the higher corner entry speed.
It is curious that with only a slight increase in rear hardness, the car is so sensitive to changes.
Even so, the car still stops at corner entry, and I'm afraid it's not so much about being medium/soft at the rear as it is about being medium/hard at the front.
TEST 4
Car “B” / t2hard rear / t1soft front
We keep the rear and lower the front hardness, entering one of the 3 soft band springs.
The soft t1 front, combined with a slight opening of the shock absorber head, helps us maintain the sensations of TEST 3 and significantly reduces the attempt to roll over. Corrected front stiffness, could these be the causes of the rollover?
Despite what was said in the previous paragraph, we still consider the need for a gentle counterweight to ensure confidence in the car.
The car is even flatter but maintains high traction and "squareness" in turns, perhaps due to the semi-hard rear. It is faster than the configuration of TEST 3.
At this point, I go out on track with TEST 1 and TEST 0, cars "C" and "A" respectively: The superior grip and excessive braking of car "C" versus "B" are maintained.
Car "B" from TEST4 is similar in performance to car "A" from TEST Zero. The latter still carries 3 layers of counterweight on both sides of the motor, more stable and secure but slow to react and drifting more, due to, I don't know if it's the t3block rear or the counterweight.
I confirm a direct relationship between rear stiffness and tendency to roll over.
TEST 5
Car “B” / t4.2 rear / t1soft rear and open shock absorber head
We configure with less hardness in the front and greater hardness in the rear (one of the 3 harder options).
The "traction control" effect mentioned in TEST Zero Beta (and maintained in TEST 1 or with medium/soft rear shock absorbers) disappears, and the car exits corners flat.
Acceleration is not as impetuous and it maintains corner entry inertia much better. Braking is longer; in short, it maintains a more consistent speed.
Greater tendency to roll over, almost mandatory at least 1 sheet of counterweight per side.
TEST 6
Car “B” / t3block rear / t1soft front
We increase the trend of TESTS 4 and 5 to harden the rear and soften the front, and we have increased sensations in the same direction.
Corner entry speed increases, constant speed increases, and cornering is more lively.
Much longer braking and driving similarity more towards a 4x2 than a 4x4.
We understand that lowering front spring hardness and locking the rear reduces the importance of front wheel contact on the track.
A hint of rollover, I finally put 1 and 1 sheets of weight (I didn't want to) and gained sensations of stability (more for peace of mind than anything else).
I slightly open the rear shock absorber head to have a minimum survival travel.
With this last configuration and with counterweights already in place, car "B", which initially had behavior similar to "C", now resembles car "A".
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