lsd advice again

[10 foot]

Wanting to upgrade my standard diff to LSD for track day improvement and more sideways fun generally. Do 5-6 trackdays per year plus road blatting. I have a mate who races Westfields who is my mechanic and he is advising removing diff, sending to BARA Motorsports in Bromsgrove and have them fit a Viscous LSD into it I think.

Does anyone have experience of Bara and am i being advised correctly with viscous lsd?

Supersport 140 incidentally

[Roadsport06]

SPC Steve Perks is just down the road from Bromsgrove and is brill. He can advice and fit a LSD. He recommends plate diffs such as titan and tran-x.

[Pendennis]

Viscous LSD is not suitable for a DD Caterham apparently

[charlie_pank]

Viscosity must be set up correctly for weight & torque of car. Very unlikely to find someone able to do that for you - which is why viscous LSDs are much cheaper than the other types!

 

Stick with plate or ATB type.

[skydragon]

If I were you I'd contact Road and Race. They can supply and fit a Titan LSD unit to your existing diff casing and come highly recommended

 

(Road & Race Transmissions, Filston Farm, Filston Lane, Sevenoaks, Kent, TN14 5JU. Phone: 01959 525105)

 

BTW - where in Yorks are you?

 

Edited by - skydragon on 28 Feb 2013 17:42:19

[7 wonders of the world]

Go for a plate that has correctly set preload and ramps,

 

Steve @ SPC will sort you one for a 7 no problem

 

ATB's are OK for road but lack the ability to handle track use, and are not tuneable either.

 

 

[LesG]

That's funny; I was just telling Phil at Road & Race only yesterday how I did this conversion! 😬

 

Basically; if you have a 7 with the early Caterham-modified Sierra driveshafts (you can tell these as the cv joints on each end of the driveshaft are cylindrical, and don't have the 3-sided 'pinched' shape), you can swap the inner cv for a lobro joint and Bob's your uncle. Simples. I think I'm right in saying all the Westies have a Ford viscous lsd fitted, so does my Caterham, and it seems to work ok.....!

 

Edited by - LesG on 28 Feb 2013 20:14:47

[Wrightpayne]

I have a quaiffe ATB as the were all the rage a few years ago. Been fine for road and 3ish track days per year. If I was buying now I'd go for a plate LSD.

 

All my gearbox and Diff work has been done by Steve at SPC (only 50 mins away from me) and he definitely knows his stuff. He understands the diff needs of a lightweight car like the seven.

 

 

Regards

 

 

Ian

[charlie_pank]

To be more specific, ATB is a torque bias system so it doesn't need to have the ramps set as the more a wheel spins the less torque it gets. It is also progressive. The plate system won't get upset/damaged by skipping curbs on track in the same way that an atb will, but it is more binary in its operation and really does need to be correctly set up for the car in question.

 

You should completely dismiss the viscous option.

[LesG]

Charlie; we'll have to arrange a trackday at Knockhill sometime, I'll let you drive my car and you can tell me if I wasted my time or not lol.......

[charlie_pank]

From wikipedia

here

 

 

The viscous type is generally simpler because it relies on hydrodynamic friction from fluids with high viscosity. Silicone-based oils are often used. Here, a cylindrical chamber of fluid filled with a stack of perforated discs rotates with the normal motion of the output shafts. The inside surface of the chamber is coupled to one of the driveshafts, and the outside coupled to the differential carrier. Half of the discs are connected to the inner, the other half to the outer, alternating inner/outer in the stack. Differential motion forces the interleaved discs to move through the fluid against each other. In some viscous couplings when speed is maintained the fluid will accumulate heat due to friction. This heat will cause the fluid to expand, and expand the coupler causing the discs to be pulled together resulting in a non-viscous plate to plate friction and a dramatic drop in speed difference. This is known as the hump phenomenon and it allows the side of the coupler to gently lock. In contrast to the mechanical type, the limiting action is much softer and more proportional to the slip, and so is easier to cope with for the average driver. New Process Gear used a viscous coupling of the Ferguson style in several of their transfer cases including those used in the AMC Eagle.

 

Viscous LSDs are less efficient than mechanical types, that is, they "lose" some power. In particular, any sustained load which overheats the silicone results in sudden permanent loss of the differential effect.[7] They do have the virtue of failing gracefully, reverting to semi-open differential behavior. Typically a visco-differential that has covered 60,000 miles (97,000 km) or more will be functioning largely as an open differential;[citation needed] this is a known weakness of the original Mazda MX-5 (a.k.a. Miata) sports car. The silicone oil is factory sealed in a separate chamber from the gear oil surrounding the rest of the differential. This is not serviceable; when the differential's behavior deteriorates, the VLSD center must be replaced.

[10 foot]

cheers Charlie for your in depth research! I Think I'll talk to Road & Race somewhere 'darn sarf', near the big smoke.....Kent so I'm told. General opinion on here seems to point to them knowing their Caterham diffs.

Did an excellent 100 mile Blat yesterday in un-broken sunshine around the glorious scenery and superb roads that is Upper Wensleydale. 'Twas a tad slape under 't arse end tho', (had her sideways on more than one occasion officer.)

It's Grim up North,- but the roads are quiet.

[LesG]

Well, if the worst thing that happens, is that I overheat the silicone and it reverts to a semi-open diff, then I'll look to invest in a plate-type. As it is, this viscous lsd came in the boxes of spares with the car when I bought it, and I thought; well, it'd be rude not to!