2G Opinions on best street and track twin disk for 7 bolt

[Kasperrr]

I have a Talon tsi making roughly 500 TQ but it’s possible I may turn it up this year. My question is, are there even twins that do decent on street with the occasional track events. Or should I not go to twin and just get a nice single.

 

[twicks69]

I can tailor a QM gear drive ceramic friction street twin for your power goals, otherwise the special order one would be OS Giken (nice heavy flywheel, large sprung hub, thinner race ferometallic friction disks, use OEM TOB MD749998 (QM) or Conical TOB TM5-5048-TBA (Can use either with OS Giken), TOB clip MD706185 and Comp clutch forged clutch fork FRK-5048 (needs this clutch fork to clear either twin disk without modification), and matching length flywheel bolts depending on application and flywheel flange thickness - see below).

I can do the Quarter Master as either a 7 bolt AWD street flywheel, street friction gear drive disk pack, 6 leg or 8 leg twin disk options. The 6 leg stuff is the older V-Drive Rally style which are straight forward, durable and a bit less expensive to rebuild due to the lower cost of the clutch cover, floater, pressure plate and my flywheel. The 8 leg stuff is the newer Optimum-V modular flat clutch cover with 8 steel legs that are pinned and fastened to the flywheel as well as to the cover (8 legs, 16 small ARP fasteners, 16 leg pins on flywheel side), and then it uses the matching 8 leg floater plate and pressure plate with Quarter Master's flywheel. Also, the 6 leg street twin with my flywheel would use 21.2mm flywheel bolts (MD302074 x7), and the QM 8 leg flywheel would use 19.5mm flywheel bolts (1120A062 x7) because of the thinner flywheel flange. Both would use an AT20 7/8"×20-spline clutch alignment tool, but you need to modify the tool for use with the QM 8 leg flywheel by taping the end to slide fit into the larger alignment hole, which is simple enough with a roll of electrical tape, measurement and careful taping.

Both clutches have the same torque capacity, which i can adjust with changing to my spec cover spring rate to meet your power goals. As for design differences, QM says the 8 leg is 25% more rigid but thats only because of 8 vs 6 legs. The 8 leg does have more durable legs (flat aluminum cover with steel bolt on legs) that are not going to gall up from continuous high rpm engine braking which the 6 leg (1 piece machined aluminum cover and legs) can get beat up with a lot of abuse. The 8 leg clutch design was made to be modular for other applications by only needing to change the leg height component vs making multiple cover designs /heights. The 8 leg costs more to rebuild than the 6 leg. The 6 leg uses M8x1.25 cover fasteners with my street flywheel to 22-24 ft/lbs torque spec. The 8 leg uses much smaller ARP fasteners that you do need to be careful with installation and use loctite 243 blue with 16 ft/lbs max torque. Both clutches weigh within a pound or so of each other ~23-24#.

Or if you want the most longevity from the driveline while going towards the upper limits of a single disk clutch, I would go with a South Bend Clutch SSX pressure plate with B series full face ceramic friction B-Series clutch disk. Part number is K536SSXB.

Clearly the SBC single will be more streetable than the twin options.

Also, as far as timelines go, SBC has been taking 1-2 days to make and ship, whereas QM has been around 3-4 weeks, OS Giken is typically 6-8 weeks from Japan.