R32 Gtr Suspension Setup - What's Next

[MrStabby]

If you want a gain there are two things I would do as a first step:

1. Replace the the stock upper link mounting bracket with either a Nismo item or a stock item remanufactured to be like the Nismo geometry or run one of those top links with the bearing in the middle of it (which I dont much like but each to their own)

Is this the one (kit with mounting bracket, lower control arm and radius rod)? http://www.nismo.co.jp/en/products/competition/lb/skylinebnr32.html

I guess the lower control arm must be different. I already have the nismo radius rods and i believe the only difference is the wider bush.

[djr81]

What would you go for? 6kg/ 7kg?

Its 'moot' not 'mute' Also - I would have thought that the type of tyres could not effect under/oversteer balance - am i wrong?

Well you are running 450/350 lb/in. I assume they are 2.5 spring ID's and to be honest I would buy both and try both a 400lb and a 350lb spring. It is one of those things if you try the harder of the two and the car likes it you go another step. You can also go up/down in 25lb (.5kg/mm) increments although the general rule is 10% otherwise you are wasting your time unless very close anyway. Springs are cheap tuning devices which probably explains why I have boxes of the things laying about home and no, none in that range, sorry.

Give Troy a break he was probablly on an ipos of some description with an autocomplete/correct.

The type of tyre does have an effect. Some like more camber than others, for example due to their sidewall stiffness or may be more sensitive to it due to their construction. See the photo for the difference between an A050 & an RE55. Which do you reckon is more sensitive to camber?

[djr81]

Is this the one (kit with mounting bracket, lower control arm and radius rod)? http://www.nismo.co.jp/en/products/competition/lb/skylinebnr32.html

I guess the lower control arm must be different. I already have the nismo radius rods and i believe the only difference is the wider bush.

Yeah but they are drug money given they are just stock components drilled or bushed differently and painted silver.

The castor rod is 5mm or so shorter with a harder than stock bush

The LCA has the outer mount 5mm or so further out. Is same casting.

The bracket has different drill points. See the attached drawing. Pretty common for production style racers to weld/redrill and generally butcher these things. May be an option - I think Fatz did it to his 32.

[Roy]

The type of tyre does have an effect. Some like more camber than others, for example due to their sidewall stiffness or may be more sensitive to it due to their construction. See the photo for the difference between an A050 & an RE55. Which do you reckon is more sensitive to camber?

This ..3 deg is a fair bit of camber if you call KU36, Federal 595 RSR and Advan AD08 semis (a lot of people do these days) if you are running RE55s and the spring rate and roll package you are... I would guess its about close to optimum. With AO50s it could very well be not enough.

I ask because the rule is softer springs and less camber is generally required with grippy street tyres. With premium street tyres , running too much camber means you never generate the grip to generate the roll to use the face of the tyre and you end up with an understeery car.

My car was finally sorted on RE55s then I moved on to AO50s and have had to change a few things re springs, alignment etc to get it how I want to drive...and its still not there. The thing is way quicker on AO50s but I still have not got the balance of the car as sorted on the AO50s.

So from my experience above is why I asked about tyres. And going back to when I ran street Falkens one track day with my optimised RE55 setup,...was a washy piece of understeering poo that was hard to get in, through or out of a corner

[MrStabby]

I'm running R888s, but will go for a new rim/tyre combo when they're done because i want to use the 34GTR rims for street.

[djr81]

This ..3 deg is a fair bit of camber if you call KU36, Federal 595 RSR and Advan AD08 semis (a lot of people do these days) if you are running RE55s and the spring rate and roll package you are... I would guess its about close to optimum. With AO50s it could very well be not enough.

I ask because the rule is softer springs and less camber is generally required with grippy street tyres. With premium street tyres , running too much camber means you never generate the grip to generate the roll to use the face of the tyre and you end up with an understeery car.

My car was finally sorted on RE55s then I moved on to AO50s and have had to change a few things re springs, alignment etc to get it how I want to drive...and its still not there. The thing is way quicker on AO50s but I still have not got the balance of the car as sorted on the AO50s.

So from my experience above is why I asked about tyres. And going back to when I ran street Falkens one track day with my optimised RE55 setup,...was a washy piece of understeering poo that was hard to get in, through or out of a corner

This. In spades.

There is a trade off between suspension geometry, spring and anti roll bar rates. Put simply your geometry will give you camber compensation in roll (because it has wishbones rather than MacPherson struts). How much depends on arm lengths top and bottom.

The higher your spring rate and anti roll bar rate the less the car will roll (obviously) and the less the camber compensation in roll will come into effect. The more grip you have the more roll you will get. You need to balance all of those things to achieve what the tyre wants. If it is a S spec tyre (I think that is what they are calling them) like an AD08 it will be in the middle of a road tyre and an R compound in terms of camber requirement.

I suspect that the reason Japanese track biased suspension is so hard is not because of the smooth circuits nor because they dont understand roll bars but more that there is no easy way of sorting the front suspension on an R32 to get the camber right and have it liveable on the road on road tyres.

Be interested to hear Troys thoughts on the RE55 vs A050 differences. My impression is that the Yokies are:

Less one dimensional in term of grip ie they will turn and brake/accelerate more happily than the Bridgestone.

Less sensitive to suspension changes than the Bridgestones - mostly due to the crown on the treadface.

Quicker by atleast half a second a minute.

Need much lower pressures.

[djr81]

I'm running R888s, but will go for a new rim/tyre combo when they're done because i want to use the 34GTR rims for street.

Well the common view of R888's on GTR's is that they suck the balls of a dog on account of there being insufficient sidewall stiffness for the weight of the vehicle.