Cup 2's & 968 castor mount bushes.

[Guest]

I've finaly got the cup 2's back on the car after 8 months. And she looks real perty. The only thing is she does'nt drive as well as she did with the origional tele dials on. I'm back in the land of sordid tram lining. I was hoping the castor mount bushes would have done the trick but it's no better than the day I tram lined into that sodding kerb. After driving on the origional wheels for all this time I have to say I seem to have spent a lot of money to ruin my car. looks aside that is, but once I'm inside the car I can't see the outside can I? Anyway i'll be taking her for a 4wheel alignment ASAP and if that does'nt give me any joy I'll be either back on the tele dials or asking for some ideas from you guys. In fact if anyone has any sugestions I would be very greatfull.
Regards.
Simon

 

[Guest]

Simon,

I'm sure you shifted things around putting on the new castor blocks. I was really off after upgraded castor blocks and dropping the crossmember for new motor mounts. It was pretty bad.

Get the front end aligned and centered by a good shop. You will have an idea how well the alignment guy is qualified if he keeps pulling the car off the rack to drive it around a bit and apply heavy braking to settle the suspension down and see how things track, then adjust some more, back off the lift to test, etc. My alignment guy had the car on and off the lift about 5 times that I saw before he was satisfied. But he is a P-Car racer so is probably more concerned about getting things spot on than the normal alignment guy.

 

[A5DSR]

What is the true meaning of tramlining? Following contours of the road?
What tyre sizes were on your teledials & what have you got now?

I have just change from teledials with 215/60/15's all round to Boxster 17" wheels with 205/40/17 at the front and 255/40/17 at the rear.
The only thing I notice is a very small amount of 'no mans land' when the car is travelling straight. ie a little movement on the strreing wheel with no obvoius movement of the road wheels. Can't remember if it did this before.

As I expected the streering/ handling is no different even though I gone from 215 to 205 tyres at the front, the actual width of the tyres have stayed the same.

Daz.

 

[Guest]

What is the true meaning of tramlining? Following contours of the road?
What tyre sizes were on your teledials & what have you got now?

The car follows contours, white lines, surface changes, Rabbits! Well it's not quite as bad as that but it's not the true as a lie detector drive that it was with the 'old' wheels.
I had 195's up front and 225's behind, now have 225's front and 255's rear so it's quite a different set up and the more i think about it the more likley i think the alignment will iron out a lot if not all of the problem. Still I recon a 1987 2.5 lux just was'nt designed for such a lot of wheel. and it is a beautiful drive with the origional wheels, so whatever the verdict nothing is irreversible.
I'll keep you posted.
Regards
Simon

 

[A5DSR]

Get the tracking checked, it could just be 225's are too wide for a 7J rim.

Check here.http://www.chris-longhurst.com/carbibles/index.html?menu.html&mainpage.html

Excellent tyre/wheel info.

Daz.

 

[Hilux]

I have just change from teledials with 215/60/15's all round to Boxster 17"

No gain in going bigger IMO, its a current trend and will affect the cars dynamics IMO.

The larger reciprocating mass alters the weight/ride height/steering feel/COG etc and probably compromises the original fine handling.

This was certainly true of my Westfield and Ginetta where stock 15" wheels felt positively ponderous against 13"

Not intended to be a criticism simply an observation. Note however that SOME of your symptoms could be that the car is now overtyred and/or that castor/camber angles are now incorrect

 

[944Turbo]

Getting the alignment done should help and consider increasing the castor from stock. Before that how old are the dampers? Fitting new ones will require realignment again so it might be better to do it first, but if original it should make a big difference.
Tony

 

[Fen]

ORIGINAL: Hilux
No gain in going bigger IMO, its a current trend and will affect the cars dynamics IMO.

Note however that SOME of your symptoms could be that the car is now overtyred and/or that castor/camber angles are now incorrect

That might well be true except that the 968CS - generally accepted to be the best handling of the family - had 17" wheels out of the box. Alignment check and you should be right.

Note that 225 tyres are pretty much right for 7" rims.

 

[Hilux]

968CS - generally accepted to be the best handling of the family - had 17" wheels

Did it also have M030 lowered suspension?

 

[Fen]

Only if specifically ordered with it.

True it probably had different spring rates to a 944 Lux but once you get to an alloy wishbone car the basic suspension was the same on the 968 apart from things like spring rates and bushes - all changeable in other words.

BTW the 968 didn't havce big enough brakes to require 17's in case anyone suggests that was the real reason.

 

[Guest]

thanks for the replys everyone, I hope to get the alignment done tomorrow, so fingers crossed eh? I was wondering if the different wheel offset for different 944/968 models equate to them having different track maesurements? Is my 1987 lux a norrower track car compared to say a M030 car? and if so by putting on the bigger wheels have I tryed to widen the track, so knocking out the geometry?
I'm just glad there is a lot of adjustability even in the lux's suspension.
Regards
Simon

 

[Guest]

Tracking done, the car now go's in a straight line and ignors white lines surface changes etc. it seems the problem was down to the changing of the castor mount bushes. Got my handling back, Massive.

 

[sawood12]

I've just replaced my castor mount bushes this morning. I noticed on comparing the two mounts that the 968 mounts will raise the wishbone bolt away from the car underside due to the positioning of the bush bore. This will change the angle of the lower wishbone. I was very careful not to disturb anything else so my settings shouldn't have been altered. However do I need to get my castor settings reset due to the angle change of the wishbone??
On a little test drive the car doesn't seem to have suffered at all for the mount change. I havn't noticed a huge improvement in turn in but the car does feel tighter at motorway speeds

 

[Guest]

ORIGINAL: sawood12

I've just replaced my castor mount bushes this morning. I noticed on comparing the two mounts that the 968 mounts will raise the wishbone bolt away from the car underside due to the positioning of the bush bore. This will change the angle of the lower wishbone. I was very careful not to disturb anything else so my settings shouldn't have been altered. However do I need to get my castor settings reset due to the angle change of the wishbone??

I'm no expert on suspension, but I'm pretty darn sure you do. Porsche put out a service bulletin that the 968 castor blocks were a required upgrade to run 17" rims on the 944. Something to do with the suspension dynamics.

There was also an internal memo on dealers recording owners running 18" rims on the 944. It was prohibited and if they saw it they were supposed to record in the vehicle history data base the observation as well as tell the customer he couldn't/shouldn't do it.

And if you noticed the blocks are a little different in the exact form of the hold downs so you probably didn't get them precisely lined up like the old ones which also had a lot more rubber to soak up misalignment. Besides, what do you think the eccentric for castor adjustment are there for?

 

[Fen]

I wondered how long it would take for that old chestnut to resurface, although I expected it to be in the !8" wheels thread.

You pays your money and takes your choice but as I see it the service bulletin was directly aimed at the ridiculously litigious North American market; it's easy to say "don't" if that then covers you against future liability.

If the suspension is in good condition and properly maintained then how exactly can an 18" wheel be any worse than a 17" wheel? Before you take the easy answers remember there has been no technical bulletin (to my knowledge) precluding the use of slicks or even treaded tyres with much greater performance than were available in 1993 (when the bulletin came out) despite that creating much higher loadings on suspension and the 968 Turbo S had 18's from the factory on the same basic suspension design.

 

[Guest]

ORIGINAL: Fen

I wondered how long it would take for that old chestnut to resurface, although I expected it to be in the !8" wheels thread.

Before you take the easy answers remember there has been no technical bulletin (to my knowledge) precluding the use of slicks or even treaded .

BLAH, BLAH, BLAH

I guessed you totally missed that part about that I was not a suspension expert. All I suggested he do is get an alignment as I suspect he has things off.

So go bugger off![]

 

[Guest]

Some time ago, after reading on here about larger wheels/castor mounts I asked an OPC mechanic was it necessary to change the mounts to 968 ones when going to 17's. He replied that it was not at all necessary. (But he did insist on calling it a nine forty-four)
Anyway, don't shoot the messenger..... only relating what I was told and in no way consider it an opinion of my own (either way) I think that has covered it!

 

[Guest]

I don't know if it is REALLY required as I ran 17" rims for 15 years without the upgraded castor blocks, no problem. And a lot of guys are running 18" rims with no disasters that I've heard about. The only thing I have heard about that could be related is aluminum A-Arm ball jiont failure but that could just be related to abuse and/or simple age and miles.

 

[Diver944]

I ran 17"s without the new caster mount for about a year and it is not necessary.

However, after fitting and an alignment it made tramlining a thing of the past and the car was a lot nicer to steer.

 

[Guest]

Ibought my car with 17' cup 2's on it and ran it for a year before changing over to the standard teledials. and it was only then that i realised how much the car had been tram lining and I had a closer look at the suspension. the car had been runnung on the standard 944 cator mount bushes so I replaced them with the 968 items and put the cup's back on. The car tram lined worse than ever and I started complaining. However, after having the geometry re aligned I can honestly say the 968 bushes have stopped the tram lining and restored the handling to how it was with the teledials on. So although it may not be 'necessary' to use the 968 bushes with 17' wheels, i would say if you own the car for driving pleasure then fit them and enjoy the pricise handling the car has.