Hi guys,

I'm buying a set of 18" wheel for track use and I'm deciding what tire to use. I did a search and could not find anything about using the Yoko A048 265/35 at the front. Have anyone tried it? Does it scrub?

It has a diameter of 25.2 inches. The rears, 315/30, has 25.4 inches. Is this difference ok?

Thanks!

 

I can't speak for fitment, but performance is dubious. I used that tire on a spec racer ford and they do not heat cycle well. We used to replace them after 4 cycles. At the runoffs, guys were running a new set every session.

 

ABS will be fine

Sizing will be fine - but, the front strut may have to be rotated and then some shims added to get caster back close to 8

You can try it without strut rotation but it may rub on large turning angles

 

Thanks guys. I was just informed that 315/30 size is not available anymore so I'll have to look for another brand option.


About caster, as I just bought the car I did the first aligment last week and I have just 6°50' of caster. I lnow I should aim for 8°30' but what should I do to have more caster? Is it what I have too little?

Regards,
Ipe

 

you may install adjustable fork (thrust) arms in front.
http://www.tarett.com/items/996-997-...010-detail.htm

also if you use solid LCA bushings
http://www.tarett.com/items/996-997-...a01-detail.htm
it also allows to get a bit more caster, but for more adjustment you need custom fork arms.

 

You have a few choices

1) with the front strut tops in as delivered position (ie non rotated), you should have no problem getting caster to spec

2) with the strut tops rotated (do this for 2 reasons, to get camber to mid 2s or high, and or to do this when fitting a wide front tire)
- your front OE caster puck should have two locations - use the location to max your caster
- after doing this, with rotated struts that's starts your camber at let's say -2, do not use the eccentric to add additional camber, but use shims and insert them in your 2 piece lower control arm - the geometry of the front suspension is such that adding the shims to get additional camber actually adds caster
- assuming your front camber is let's say -2.5, then with rotated front struts, the eccentric set to the zero position as a start, and then fully shimmed to get as close to -2.5 as possibly and then only the tiniest eccentric adjustment, your caster should be approximately 8.0

The above should give you what you want - the approach also allows you with rotated + shims + maybe 5mm spacer to fit a large front tire - add a little bit of a worked front fender with a wood baseball bat, change the front spring to a 2.25 ID from 60mm and you can likely fit a 285 front 18" that runs very slightly shorter than stock height (let's say 24.5-25" diameter)

You can order an Adjustable Trust Arm to perfectly get your caster number / at least maximize it as much as possible until you get rubbing

http://www.tarett.com/items/996-997-...010-detail.htm

You don't really need to do this but if you like the max caster driving feel this is type of product allows you to fine tune. If you are going to do that then when in there, order solid caster pucks and monoballs

http://www.tarett.com/items/996-997-...996-detail.htm

Or to make it easy, order it all put together

http://stuttgartperformance.rpmware..../i-398277.aspx

 

if you want to get full benefit from wide tires i would go one extra step forward and instead of 9"/12" x19" wheels or 9"/12" x18" wheels went to a shop, rolled up fenders and went to cup sizes or 10/12 rims.
with 10" rim in front wide tire will sit much better than 265/275 sits on a 9". and I am not sure if makes any sense to put 285 tire on a 9" rim. even 275 is quite wobbly there. it really wants 10".

 

Sorry for my ignorance but I'm coming from a 996 MKI GT3 so all the things from 997 and GT3 RS are new to me. Does the .2 RS come with caster eccentric bolt in control arm or does it have two holes? If it is neither way how do I adjust caster to spec?

Thanks for your help!

 

I can't speak to the .2RS but the 997gt3.mk1 has 2 holes, unless I've lost my mind, for caster adjustment - there is no eccentric (that is for camber) - i would have thought this should be the same as your 996gt3. The difference between gt3 and RS is the rear lower control arms are also 2 piece like the fronts - except since the eccentric in the rear is at the bottom, which is also were the shims would go for added camber, it is easier to use the eccentrics in the rear for camber adjustments ( you could argue that using shims in the rear would prevent any unwanted camber changes if you use shims only and leave the eccentric in the zero position).

I dialed down my front camber from-2.7 to -2.3 to try the PSS tires. With rotated front struts and shims in the lower arms for all camber adjustment and with the caster placed in the second hole, my caster is 8.0 - if camber was adjusted without the shims but with just the eccentrics and with rotated struts, caster I believe is just above 7.0.

If you are going to be running low 2s high 1s for front camber it would be best to use un-rotated front struts to keep caster in spec - that is unless you are shoving in big front rubber and thus require the space via strut rotation to make the tire fit.

And, 6 caster isnt going to kill you - caster is really a feel thing and most drivers would never know the difference if the car was working with camber, toe, tire temps, etc - that said, as long as your shop has camber shims (OE or other), you can increase your caster at least closer to spec.

 

Thanks again for your help! As for the eccentric bolt for caster adjustment for 996 GT3, look below in this page of the 996 GT3 Techinical Manual that you can have a control arm with this eccentric bolt to adjust caster.

 

on my car with rotated front mounts eccentric was only able to give 6.8 something caster with -3 deg of camber. so i had to get adjustable fork arms.
if you can fit 265 rubber on stock rims without them getting in contact with springs - good for you, but it may not be possible. in order for wider rims to fit uder stock fenders you will need to turn upper mounts.

 

I believe we are talking about the same thing - i.e. what you are calling an eccentric for caster adjustment, I am referring too as the second hole in the caster puck for increasing the caster. I am quite certain, although one can never be positive, that on 'my' OE caster pucks (in the front), and at least one other one I've seen that is an OE part, it is a two hole puck (less caster, more caster) - it isn't a sliding eccentric per say as your typical camber adjustment would be.

 

This may be because there are OE GT3 arms with only 1 hole for caster - mine have 2. My lowest caster, when rotated, in the outer hole is 7.3 - it may in fact be 6.8 when in the '1st' hole. I was then able to shim it out to 7.9 on one side and 8.0 on the other (if memory serves) when I bumped up camber with shims.

 

I don't think we are talking about the same thing. Look below at another page of the techinical manual about this caster eccentric bolt.

 

difficult to say now... i just looked - i have 2 holes there. so, not sure why, may be something else was shifted too. who knows.