Toyota Supra MKIV Ultimate Clutch FAQ Part 2

Picking up from Part 1, we continue on from our variables list below.

1. Cost 2. Street-ability 3. Pedal Pressure 4. Drag Racing Performance 5. Road Racing 6. Pedal Engagement Point 5. Failure Rate of Clutch 6. Rebuild Cost of Clutch 7. HP/Torque Capabilities 8. Stock Car 9. BPU Car 10. Chatter 11. Crank-Walk Potential

Road Racing: With road racing clutches, I am defining them as street cars that also do double duty on road racing circuits. Since there are no hard launching or heavy slipping required like in drag race applications, you can eliminate the need for the top end clutch systems.

What people are looking for is a clutch that allows the motor to rev well, shift smoothly, hold the power and typically with a light pedal feel. This put you into for the most part the entry level multi disk clutches, which offer all of the above. To be honest, if streetability is a great factor, then the Blitz Twin Disk, OS Giken (new version) are solid choices. There really isn't a bad choice, with the exception once again of the HKS twin and triples as their street-ability is very poor. Single disc clutches can work, if you can use a lightweight flywheel (solid), coupled with a sprung hub disc. You can get away quite nicely with an ACT pressure plate, factory disc and a lighweight flywheel from Fidanza or RPS. This will hold fine to 500hp or so on a street road car. For those running in the 750hp range, then you will once again need to make the switch to a 6 puck disc with the least aggressive pad material possible.

Pedal Engagement Point: One of the nuances of learning to drive most any aftermarket clutch for the Supra, is adapting to the new engagement points for the clutches. I define pedal engagement point as the point when the clutch pedal is depressed to the floor, and then released upwards to the point where it start to engage or grab.

Single disc clutches typically start to engage around 1 to 1.5" off the floor board, which is a significant change, when you are used to the stock clutch engaging about 1/3 to 1/2 way up. The multi-disk clutches tend to engage about 1.25 to 1.75" from the floor.

One must factor in proper adjustment of the clutch pedal, condition of your master cylinder and the overall set-up of the clutch itself.

Failure Rate of Clutch Brands: This is a dangerous section because people have clutches that I might rate as not as robust as another and have a completely different opinion. It is subjective. What I am doing is rating the reliability of the manufacturer in building these clutches for MKIV Supras, warrany support and the ability to quickly turn around a problem.

The ratings might be numerical and subjective, but they are mine.

1. ACT. ACT is a well run company that support their product well, has replacement parts generally available (isn't general the term for all Supra owners?, as no one every has enough MKIV parts on the shelf, us included) and is a well designed product. USA made and supported. This does not mean ACT is the best clutch, just supported well, good quality with readily available spares. That goes along ways though.

2. HKS. They service and support the product well, but the fact being is the twin and triple disc clutches are a flat pain on the street. On a side note, while for a Japanese supplier, they do stock quite a bit, having replacement parts is an issue. They stand behind what the sell.

3. Exedy. Japanese built but with a mass marketing strategy which means decent spares, good support and enough resources to help.

4. Tilton. For $5000+ they better stand behind the product and they do a good job of that. You get what you pay for with them. Good product support, although they can be a bit stand-off-ish if you are just an average consumer and for that reason alone I put them below HKS.

5. Blitz. Stands behind the product very well, but they are hard to come by, so if something goes wrong, you are usually down for quite some time.

6. Carbonetics. Very solid company with a multi plate carbon based product that doesn't have too many installs i the field, but are known to support the product well. Jury still out, but very respectful.

7. SPEC. I know SPEC doesn't have the greatest reputation in the MKIV Supra world, but they do stand behind their product and for the lower power cars, they are pretty decent.

8. OS GIKEN. Vast improvement in the quality of the parts and design, as well as product support of days of old. Why are they number 5 then? Jury is still out on total reliability and parts availability, but an ultra-high quality part, no doubt.

9. RPS. Rob Smith the founder of RPS loves Supra's and out of all the companies listed above, knows more about Supra's in my opinion. Rob supports his product, but his business has suffered some growing pains in quality of the carbon carbon clutches because he doesn't have the resources for development testing like the bigger companies. I have always liked the basic single disc RPS clutches, his pressure plates are rebuildable and segmented and the carbon carbon products are novel. A bit more data in the field will cause RPS to climb. I still do not hesitate to recommend Rob's product, just know that sometimes things go wrong and then the challenge of proper support comes into play.

Others. AZ Clutch and HPF clutch. AZ uses the RPS pressure plate and a six puck sprung hub disc with a hybrid metallic puck. The HPS uses the ACT pressure plate and either a standard bronze 6 puck or what we call a ferrite based hard metal puck. Parts are readily available since they are RPS and ACT products with a clutch disc manufactured by multiple companies and rebadged as their own designs. The AZ clutch which is also known as the WOTM.

Rebuild Costs: True rebuildables are Tilton, Carbonetics, RPS Carbon Carbon, OS Giken (new), HKS and SPEC multi plate series. For single disc the RPS segmented flywheel is totally rebuildable. Single disc clutch hubs are not rebuildable. If you have the $5000 for a Tilton triple or quad then you have the $1500+ for a rebuild.