ICT is not HL
Ridge Rider said:
As for braking, the disc brake force is much closer to the axle than rim brakes but is the force is also proportionally larger. The brake force applied to the wheel and the force at the tire contact patch can be (for linkage calcualtion purposes) be replaced with a force and a torque at the rear axle that will be identical for disc brakes and rim brakes and it also doesn't matter what orientation the disc or rim brake is mounted (the mounting location will matter for structural strength considerations).
The main reasons why riders can't tell the difference between HL Turners and TNT turners:
1. The main swingarm pivot is in the same place and the center of curvature of the HL is in almost exactly the same place. This means that the peddaling characteristics that are determined by the axle path are the same.
2. The rest of the linkage points are the same, so the progresivness of the linkage (or leverage rate curve) is almost exactly the same. This means that the behaviour of the suspension to bumps and pedal induced movement (as it applies to the rate curve) will be the same.
3. Theoretical differences in the braking behavior which appear to be significant due to the difference in location of the HL's instant center and the TNT's main pivot are not as significant in most braking situations because due to the high center of gravity, the forward wieght shift from decelleration unweights the rear tire to the point where the differences in brake squat between the two designs are much less than the braking force coming from the front wheel.
4. The geometry, pivots, and structural stiffness of the 2 designs are identical except for the area at the rear axle.
In short a Turner is still a Turner with only small differences.
Good summery of the minimal pedaling and braking differences of ICT and monopivot TNT, Ridge Rider. And many great comments here by others.
The pedaling anti-squat and kickback are the vertually same in theory and ride tests now finally verify. The lower flex of the TNT design produces even more efficent pedaling responce. The braking tradeoff of the TNT's less flexy rear wheel mount and elimination of brake dive reaction offset the freer extending but more front suspension loading Turner 4-bar (so-called ICT) design.
The TNT design is a forward advance in Turner design, technically superior in all conditions than ICT.
I've said this for years. Turner invented his own designs. ICT is a written description of what Turner designed in the late '90s, which was followed by FSR design soon after Turner. The ICT patent even boldly sites prior design use by Turner, admitting it is a stolen design, without putting Tuner's name on the ownership application!
To the original post. So-called "ICT" geometry is not Horst link geometry.
HL has subtle but noticeable performance differences. Slightly more acceleration efficient, at the tradeoff cost of slightly increased pedal kickback than the ICT pedal kickback. And HL is slightly more bump compliant while braking at lower speeds than ICT, particularly more compliant than the more parallel versions of ICT which have significant rear suspension extending reactivity.
Unlike HL geometry, ICT does not change the axle path and subsequent pedaling reactivity compared to a monopivot with the same near BB pivot. The lower chain-stay pivot location of the HL produces a path that can be described by a monopivot if the pivot was where the back tire and front derailieur are, which has been impractical for bike design. Note that FSR design followed Turner in raising the chainstay pivots about inch higher above the HL geometry, but moved the BB pivot rearward as far as practical to somewhat maintain the Horst Link reactivity, but it compromised the more significant difference a Host link geometry produces.
An inch difference in pivot geometry is very significant when only a few millimeters in link geometry difference can sometimes make a noticeable difference.
Braking is potentially very similar between ICT and HL. The late '90's Turner "so-called ICT" geometry had HL type braking geometry. While the IC migrates in travel behind the front axle near axle height it is close to HL reactivity. For lower speed common trail riding velocity the HL geometry has more significant bump sensitivity compliance reactivity than when the IC is ahead of the front axle producing a rear suspension extending reaction. The HL become more compressive in mechanical reaction when deeper in travel and less compressing when in shallow travel, complementing bump travel traction compliance.
The more parallel floating brake designs more common of the Dare and latest almost yearly design change of the TE trail bikes are extending in brake reaction, effectively launching the rider if not for platform or slow rebound damping. Some downhill riders find advantage with extending brake reactivity, although the experts are not using floating brakes now days as much as in the nineties. The more rearward path DH designs such as high monopivot and Lawwill noticeably benefit from more extending reaction braking. Extending brake reactivity has no net benefit for slower trail riding.
Horst link has a noticeable pedaling and braking performance difference that many experts prefer. Many other experts prefer the soft pedaling and more stable braking lower monopivot design. It's a matter of personal preference.