ISF - Suspension / LSD

BTCC_ Racer · May 27, 2022

Hi all,

I've owned the ISF for a few months and i've carried out all the preventative stuff.

Im turning my focus on the suspension / LSD got a few questions:

Im thinking of refreshing my shocks for oem units, although the oem units are pretty stiff, i hear later models are a worthy upgrade?

Also Bilstein B6 offer some oem equivalents - anyone had first hand experience?

In regards to the LSD anyone carried out a swap? i.e LSD fitted in original casing or just sourced a complete unit?

Thank you

Twellsie · May 30, 2022

My car had Bilsteins on it when i got it, unfortunately I dont know how this compares to stock but it was comfy enough, now on BC Racing Coilovers.

LSD is on the list but have not got round to it yet

BTCC_ Racer · May 30, 2022

7 hours ago, Twellsie said:

My car had Bilsteins on it when i got it, unfortunately I dont know how this compares to stock but it was comfy enough, now on BC Racing Coilovers.

LSD is on the list but have not got round to it yet

How do the BC coilovers compare to the Bilsteins?

what options are you looking at for a diff? I would prefer a oem diff unit and just swap the whole assembly.

Twellsie · May 31, 2022

15 hours ago, BTCC_ Racer said:

How do the BC coilovers compare to the Bilsteins?

what options are you looking at for a diff? I would prefer a oem diff unit and just swap the whole assembly.

I really like the BC's if you order from a authorised distributor you can spec the spring rates and the shocks are valved accordingly, i intentionally spec'd mine slightly harder than Bilsteins (16-12), at full soft they are about the same as the Bilsteins and at full hard they are pretty stiff, FIGs recommend 14-10 for everyday road use which I think would be spot on if you just want a nice compliant ride.

LSD wise I was leaning towards the Cusco 1.5 Way, but closer to when I am ready to pull the trigger will speak with the guys at Gripper Diffs to see what they can do.

BTCC_ Racer · May 31, 2022

Is the Cusco a clutch pack diff?

Twellsie · May 31, 2022

32 minutes ago, BTCC_ Racer said:

Is the Cusco a clutch pack diff?

its a plated diff yes

Twellsie · May 31, 2022

sorry its the OS Giken one that would be my prefereance

BTCC_ Racer · May 31, 2022

22 minutes ago, Twellsie said:

its a plated diff yes

Not ideal for the road. I have a clutch pack in the DC2, great on track but a little pig for daily use.

Any non clutch options?

Twellsie · May 31, 2022

10 minutes ago, BTCC_ Racer said:

Not ideal for the road. I have a clutch pack in the DC2, great on track but a little pig for daily use.

Any non clutch options?

based on what? noise, servicing?

The Os Giken has through holes on the plates so stays quiet, its also adjustable via spring preload so doent need replacement of the plates so frequently.

i am not aware of any non-plated diffs available so you would be looking at ISF, GSF or RCF diffs, i believe there is a IS300 LSD that fits but thats a shorter ratio

BTCC_ Racer · May 31, 2022

11 minutes ago, Twellsie said:

based on what? noise, servicing?

The Os Giken has through holes on the plates so stays quiet, its also adjustable via spring preload so doent need replacement of the plates so frequently.

i am not aware of any non-plated diffs available so you would be looking at ISF, GSF or RCF diffs, i believe there is a IS300 LSD that fits but thats a shorter ratio

Ive had a plate diff in the DC2 for over 14 years, well two units, one a Kaaz and another a Mugen both 1.5way. I've known people in the trackday scene who have Os Giken not disputing how effective it is, just the noise and yes the oil needs changing frequently, i change the oil on the DC2 annually. If you can live with the clunks on tight turns and coming out of junctions then go for it.

For me the ISF is a road car so will be sticking to oem type. GSF and RCF diff are torque vectoring will they work in the ISF?

Twellsie · May 31, 2022

personally i am not too concerned with clunking on a rear wheel drive application, i had a plated diff front and rear on a 4x4 Cosworth which was horrible, changed the front to a Quaife ATB which was much better and the rear was fine.

Its been a while since i looked into it but seem to remember the oil change intervals were something like 30k miles for the OSG?

regarding the RCF and GSF diffs I believe not all had TVD

4969_LXS · May 31, 2022

@Twellsie is right, if an RCF, GSF and LC500 isn't specced with the TVD diff. They come with the same 2.937 ratio Torsen limited slip differential that was used on 2010+ ISF's. The GSF and RCF even use the same housings, so is a straight swap. I would bet the LC500 uses the same housing as well. Saves the company money using an existing design.

Twellsie · May 31, 2022

@BTCC_ Racer Out of curiosity I spoke with Gripper Diffs (as mentioned above) they dont currently manufacture a unit for the ISF, but can do bespoke applications, for a 1 off it would be £3000 +VAT (their off the shelf diffs are generally around the £1200 mark so more than half the price goes into the engineering costs) If a few of us were interested that would obviously bring the price down.

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With certain settings the “differential action” is hardly noticeable, the improved handling being all that is felt. Alternative settings, say for “Rallying”, will give continuous drive even when a wheel is lifted or indeed a broken drive shaft, instilling complete confidence in whichever type of vehicle you are driving.

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BTCC_ Racer · June 2, 2022

Snap I'd also emailed Gripper and whilst at it I emailed Quaife. Quaife want a min of 10 order and a diff assembly as a donor.

Id by down for the gripper if there was a group buy.

F.A. · June 2, 2022

All GSFs came with the TVD. It was an option on the RCF.

F4Fun · June 2, 2022

I’ve come from owning a 08 ISF for 5 years to a late 10 MY11 ISF with the upgraded suspension. I’ve got to say it’s a vast improvement over my 08. Definitely a worthy upgrade to do if you can get it.

With regards to the LSD, if you can fit one do it. I was constantly on the look out for one when I had my 08 and even considered buying one new from Lexus but £4800 seemed a bit steep. Couldn’t fault my 08 handling wise, but I always wanted a bit more fun out of junctions etc and the LSD really does transform the ISF, it’s so much more playful/fun on road and on track.

BTCC_ Racer · June 3, 2022

13 hours ago, F4Fun said:

I’ve come from owning a 08 ISF for 5 years to a late 10 MY11 ISF with the upgraded suspension. I’ve got to say it’s a vast improvement over my 08. Definitely a worthy upgrade to do if you can get it.

With regards to the LSD, if you can fit one do it. I was constantly on the look out for one when I had my 08 and even considered buying one new from Lexus but £4800 seemed a bit steep. Couldn’t fault my 08 handling wise, but I always wanted a bit more fun out of junctions etc and the LSD really does transform the ISF, it’s so much more playful/fun on road and on track.

That what I like to hear - thanks for this! I was out over the moors last night like many nights and powering out of tight corners aren't the cars strong points given a little grease.

F4Fun · June 3, 2022

2 hours ago, BTCC_ Racer said:

That what I like to hear - thanks for this! I was out over the moors last night like many nights and powering out of tight corners aren't the cars strong points given a little grease.

No problem mate.

BTCC_ Racer · June 9, 2022

On 5/31/2022 at 11:34 AM, Twellsie said:

sorry its the OS Giken one that would be my prefereance

I've spoken to someone ive used for gearbox rebuilds and he has stated the newer type OS Giken TCD does not clunk nor make any noise like the older designs.

I will now add OS Giken on to the potential list. Changing the diff our every year or so doesn't bother me.

It would be nice to get feedback from somehow who has fitted the diff to provide some insight on the following info:

Diff bushes - worth changing?

Pre-facelift electronics integration with the a LSD - how does the e-brake work with this? Im assuming on the facelift ones the calibration has altered due to have a factory LSD?

Twellsie · June 10, 2022

100% i would change the diff bushes, preferably stiffer ones, infact on my own car a would probably go solid mounted.

Presume you mean how the brakes manage the diff on a non-LSD? From what I understand the controls are the same across all years, however a mechanical diff is quicker than the electronics so doesnt have the opportunity to kick in

BTCC_ Racer · June 10, 2022

1 hour ago, Twellsie said:

100% i would change the diff bushes, preferably stiffer ones, infact on my own car a would probably go solid mounted.

Presume you mean how the brakes manage the diff on a non-LSD? From what I understand the controls are the same across all years, however a mechanical diff is quicker than the electronics so doesnt have the opportunity to kick in

excellent - ill probably just get oem bushes for the rear diff, I get no wheel hope which usually is a sign of wear but equally its rude not to refresh whilst the diff assembly will be removed. Now its a case of finding a diff!