New rear anti roll bar

[Stuntz]

My wote is for yokohama!

[Evodelta]

My vote is for slicks.

It's not an under inflation problem is it?

[jimnielsen]

I know looks like an under inflation problem - but I started with 31 PSI front and rear. After 8 laps pressure was 39 PSI. Temp on outside edge was 70 degrees C - Ambient air temp was 23 degrees and track temp certainly less than thirty.

I am planning on giving this tyre a go : -

http://www.fsport.com.au/fsport_site...umho/v70a.html

Has anyone used it as a track tyre? They are quite expensive - $360.0 (AUD) each. Apart from the Federal 595RSR tyre (that is currently on the car) these Kumho v70a tyres are the only 'R type' ones that I can find in 205/16/45 size. I may go to slicks next year - but then I have to move up to "racing class" - something I was hoping to avoid for a little while.


The anti roll bar on the front is the standard one.


I am interested in adding some castor angle on the front struts (as has been mentioned here) in an attempt to gain a little more camber under cornering - although the wheel in the picture does still seem to have tome negative camber..Has anybody tried this on a Q4? Mine had the D2 struts.

thanks, jimn~

[Steve Webb]

I had the same problem a few years back on track, and I think it is pretty much down to tyre construction. I was running Yoko A539s and it didn't matter what pressure they were at, in low speed corners they were trying to pull themselves off the rims.

What width are the tyres and what is the rim width?

Not sure how you would go about adding Castor as both the top and bottom of the strut seem pretty fixed to me. The only way would be to slot the holes that the suspension top mount bolts through, but then you have the problem of locating the top mount securely!
Is the tyre issue the driving force in you wanting more -ve camber under cornering? Personally I'd try looking for tyres with a stiffer sidewall construction first.

[jimnielsen]

The tyres are 205/16 R45 - the standard width. 7" rims...

I may try these..

http://www.stuckey.com.au/tyres_deta...TyreName=DZ03G

but in 225/16 R45.

jimn~

[Steve Webb]

225's may be just a little too wide for 7" rims. I'm fairly sure the Toyo's I've got at the moment need a 7.5" rim for a 225\40 section.

[jimnielsen]

yes - I agree that 7 1/2 would be better, but many WRX's run the these 225's as a track tyre here on 7's. - and I only have 7's at the moment

[Evodelta]

What temps did you have across the tyre, outside edge, inside and centre? This is how you check for over/under inflation.
I use normal road tyres sometimes and never have this problem, I'll see if I can get a pic later as we recently wore some down to the string on a concrete track (very coarse) and there is no sidewall damage, it's just worn smooth.

[Evodelta]

[QUOTE=Steve Webb;11230]I had the same problem a few years back on track, and I think it is pretty much down to tyre construction. I was running Yoko A539s and it didn't matter what pressure they were at, in low speed corners they were trying to pull themselves off the rims.

QUOTE]

To be fair, any tyre will want to pull itself off the rim! Did yours have any bad damage to them like Jims has?

[Steve Webb]

[quote=Evodelta;11241]

I had the same problem a few years back on track, and I think it is pretty much down to tyre construction. I was running Yoko A539s and it didn't matter what pressure they were at, in low speed corners they were trying to pull themselves off the rims.

QUOTE]

To be fair, any tyre will want to pull itself off the rim! Did yours have any bad damage to them like Jims has?

Yep, excessive shoulder wear with chunks of rubber missing, also people trackside questioning what tyre pressures I was using as they thought they were under inflated. I was running 38psi cold at the front.

[#84]

Kumho Ecsta V70A = NO

I have tried different compounds, but they can not handle the front weight. They even over heat during braking (with good brakes) and has no control once you turn the steering wheel.

Pirelli PZero Corsa are available in 205/45-16 at about €230 each.

I did consider 225/45-16, but it requires 8" rims and it is extremely critical to get the lateral match strut/caliper/wheel arch.

[cuore_sportivo_155]

I'm going for toyo R888 in 195/50 r16 on 7" wide rims, but then I have a 2.0 8v which is a fair bit lighter than a q4... but still worth considering as this size is less likely to run of the rim....

[jimnielsen]

Thats great info about the Kumho V70a, #84 - Its great to hear from somebody who has actually USED the tyre in question! Ad I have to use 'something' - though not till the 18th of Jan - I will probably give the Dunlop DZ03G a shot in 225/45R16. I will report back and let you know how that goes!

[na15575]

I have the same problem with the outer side of the tyre in the track I use toyo r888 195/50/15
my first mistake is that I put them on 6" rims
all the outer of the tyre front and back is gone to the first 4 laps
I raise the pressure to 40 psi ,match better but still a problem
I use the same tyre on 7" rims and I make 30 laps with out a serious wear at the side
as I can see from your tyre the pressure that you use is low
and this because the centre of the tyre is with out any wear
I have 36 psi in all the tyres at start and am going to try 38psi that I believe is better
I going to raise the pressure until I see that the centre of the tyre have bigger wear .
205/45/16 needs at list 7.5"
and 225/45/16 at list 8+
with your rims go for 195/?/16
it is the best that you can do
and I see that this recommends and from the others

[#84]

One thing you should have in mind when discussing tyres for track use is that for road tyres you use the pressure to adjust the structural stiffness - as a consequence the tyre will run cooler with higher pressure since structural flex is responsible for a large extent of the heat generation. For a R classed track tyre, street legal or not, the cord structure is totally different (stronger) and the pressure is used to regulate the temperature - lower pressure => lower temperature.

So, maybe you start at 2,8-3 bar with a good sport tyre, while starting at 1,8-2 bar with a R-tyre. Depending on the compound you might have to start at one pressure, drive two laps and then lower the pressure, otherwise you may destroy the tyre the first laps when the temperature hasn't build up the pressure. In this case you have too soft compound.

Some of the cheaper R-tyres has a cord structure similar to the road tyres, but with a racing compound. The Kumho tyre is an example and the wear pattern is very strange (not only on my car). It is worn out at 25 % and 75%, sen from the outer edge.

[jimnielsen]

Below is a link to a site that has a very nice and easy to read comparison of anti roll bar (sway bar) diamaters and their relative stiffnesses. its From a Subaru WRX site.

http://www.northursalia.com/techdocs/sway/sway.html

Also (from the same site) is this:

http://www.northursalia.com/techdocs...uspension.html

It is just an exploded view diagram of the WRX front suspension. What is interesting is how similar it is to the Q4 setup.

There is a huge amount of information on the web about WRX's used on the track and the strategies that they use - both technical and driving style - to combat understeer.

I thought that this one was particularly interesting...


http://www.clubwrx.net/forums/suspen...ps-thread.html


cheers for Christmas.

jim.

[jimnielsen]

Hi.

I have had a part number made up here at Pedders Suspension in Bendigo, Australia for a 24mm rear antil roll bar for the 155 Q4. It is their part number: SXR18

I have just had another of these bars made for "na15575" a member of this forum from Greece.

The bar is $310 AUD (including shipping it back from Sydney to Bendigo) - approx 160 Euro.

Shipping from Australia to Europe is $165 AUD - approx 82 Euro.

you can contact Pedders Bendigo here...

http://www.pedders.com.au/storeFinder/1/store27 - ask for Brendan!

I can take care of shipping the bar to you if need be. The manufacturer has my original bar to copy from. The bar has no tabs (the little ears that attach the bar to the body about 6" along from the main attachment point.) Just remove the one from the existing standard bar.


Cheers, Jimn~

[#84]

Excellent!

And I suppose it was possible to get it in 22 mm as well? Or would you recommend 24 mm on a "time-to-time race car"?

/A

[jimnielsen]

Should be no problem to make it in 22mm - just tell brendan
At Pedders!

Cheers

[AlfaJack]

Hi Jim,

I am very interested in having one of these made. I will contact you about it soon

[wrinx]

Give me a shout when you do...if I can stretch to one it might help with the postage or even the overall cost

How about a UK group buy???

wrinx

[AlfaJack]

Give me a shout when you do...if I can stretch to one it might help with the postage or even the overall cost

How about a UK group buy???

wrinx

Will do

[mindus]

Add me to the list please.... I would go for 24 mm

[Steve Webb]

Have any of you spoken with Balance motorsport in the UK, they proclaim to be offer custom made ARB's. They do quote a 12 week lead time, but if you are going for a bulk buy shipping might work out a little cheaper.

[AlfaJack]

Will give them a buzz on Monday. The advantage with Pedders is that they dont need one of us to send an original to them as Jim has already had a couple made. Oh and the price is very good!
Will let you know what Balance say though.

Whiteline in the UK will make a front ARB for V6 and TS 155s for ?130 but need a minimum order of 10.